22_ENVIRONMENTAL ENGINEERING

Source: Standard Handbook for Civil Engineers 22 G Raymond Schulte Thomas E Wilson Consulting Engineer, Johnson, Mirmiran and Thompson, Inc Baltimore, MD Consulting Engineer, Barrington, IL ENVIRONMENTAL ENGINEERING E nvironmental engineers are concerned with works developed to protect and promote public health, improve the environment, and prevent degradation of land, water, and air Their practice includes surveys, reports, designs, reviews, management, operation, and investigations of such works They also engage in research in engineering sciences and such related sciences as chemistry, physics, and microbiology to advance the objectives of protecting public health and controlling environment Environmental engineering deals with treatment and distribution of water supply; collection, treatment, and disposal of wastewater; control of pollution in surface and underground waters; collection, treatment, and disposal of solid and hazardous wastes; housing and institutional sanitation; rodent and insect control; control of atmospheric pollution; limitations on exposure to radiation; limitations on noises; and other environmental factors affecting the health, comfort, safety, and well-being of people This section, while covering primarily the aspects related to handling of liquid wastes, also deals briefly with other environment-related tasks, such as solid-waste handling and air pollution (See also environmental discussions in Sec 14 and subsequent sections.) 22.1 Prevention of Environmental Pollution Because of public concern over accelerating deterioration of the natural environment, Congress established the Environmental Protection Agency (EPA) and passed legislation to control disposal of solid wastes and discharges to water and air The following legislation is of particular significance to environmental engineers National Environmental Policy Act n All agencies of the Federal government and state and municipal agencies executing programs supported by Federal funds are required to carefully consider the environmental consequences of major actions, including proposed construction projects, and proposed legislation The objectives are: Fulfill the responsibilities of each generation as trustee of the environment for the succeeding generation Assure for all Americans safe, healthful, productive, and esthetically and culturally pleasing surroundings Attain the widest range of beneficial uses of the environment without degradation, risk to health or safety, or other undesirable and unintended consequences Preserve important historic, cultural, and natural aspects of our national heritage, and maintain, wherever possible, an environment that supports diversity and variety of individual choice Achieve a balance between population and resource use that will permit high standards of living and a wide sharing of life’s amenities Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.2 n Section Twenty Two Enhance the quality of renewable resources and approach the maximum attainable recycling of depletable resources Clean Water Act (Federal Water Pollution Control Act) n The objective is to restore and maintain the chemical, physical, and biological integrity of the nation’s waters The act directs EPA to establish technology-based limitations and standards for industrial discharges The states set water-quality standards for their waters Control is achieved principally by issuance of permits by EPA or delegated states under the National Pollutant Discharge Elimination System (NPDES) Safe Drinking Water Act n EPA is required to establish regulations for public drinking water supplies Primary regulations set maximum allowable levels for contaminants in drinking water and establish criteria for water treatment Secondary regulations deal with taste, odor, and appearance of drinking water Other regulations protect groundwater through controls over injection wells under the Underground Injection Control Program EPA delegates primary responsibility for enforcement to the states and supports state programs with grants Resource Conservation and Recovery Act n The objectives are to improve management of solid wastes, protect the environment and human health, and conserve valuable material and energy resources The act also provides for state programs regulating hazardous wastes from generation to disposal, including disposal of industrial sludges containing toxic materials The states regulate disposal of solid wastes on land in accordance with Federal criteria Marine Protection, Research and Sanctuaries Act n EPA is required to protect the oceans from indiscriminate dumping of wastes and to designate safe sites for dumping An objective is an ultimate halt in ocean dumping of wastes The Corps of Engineers issues, subject to EPA approval, permits for dredging, filling of wetlands, or dumping of dredged material Superfund (Comprehensive Environmental Response, Compensation and Liability Act) n The Federal government is authorized to remove and safely dispose of pollutants in hazardous waste sites, underground water supplies and other facilities The act establishes a Hazardous Waste Response Fund to pay for cleanup and damage claims EPA designates substances that may present substantial hazards to public health or welfare or to the environment The National Response Center should be notified of releases of hazardous substances Clean Air Act n The objective is to protect public health and welfare from the harmful effects of air pollution EPA promulgates National Ambient Air Quality Standards To meet these standards, the states prepare State Implementation Plans and plans for enhancement of visibility and prevention of significant deterioration of air quality in areas where the standards have been attained EPA also develops New Source Performance Standards, to reduce pollutant emissions, and National Emission Standards for Hazardous Air Pollutants, applicable to pollutants that will cause an increase in mortality or incapacitating illness In addition, EPA sets limits on emissions from moving sources of air pollution (R A Corbitt, “Standard Handbook of Environmental Engineering,” McGraw-Hill Publishing Company (www.books.mcgraw-hill.com).) 22.2 Major Sources of Water Pollution There are two major sources of water pollution: point sources and nonpoint sources The former consists of sources that discharge pollutants from a well-defined place, such as outfall pipes of sewagetreatment plants and factories Nonpoint sources, in contrast, cannot be located with such precision They include runoff from city streets, construction sites, farms, or mines Therefore, prevention of water pollution requires a mixture of controls on discharges from both point and nonpoint sources Domestic wastewater and industrial discharges are major point sources The Clean Water Act and the Marine Protection, Research and Sanctuaries Act (Art 22.1) aim at elimination of discharge of pollutants in navigable waters and the ocean Wastewater is the liquid effluent of a community This spent water is a combination of the liquid and water-carried wastes from residences, commercial buildings, industrial plants, and insti- Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.3 tutions, plus groundwater, surface water, or storm water Wastewater may be grouped into four classes: Class n Effluents that are nontoxic and not directly polluting but liable to disturb the physical nature of the receiving water; they can be improved by physical means They include such effluents as cooling water from power plants Class n Effluents that are nontoxic but polluting because they have an organic content with high oxygen demand They can be treated for removal of objectionable characteristics by biological methods The main constituent of this class of effluent usually is domestic sewage But the class also includes storm water and wastes from dairy product plants and other food factories Class n Effluents that contain poisonous materials and therefore are often toxic They can be treated by chemical methods When they occur, such effluents generally are included in industrial wastes, for example, those from metal finishing Class n Effluents that are polluting because of organic content with high oxygen demand and, in addition, are toxic Their treatment requires a combination of chemical, physical, and biological processes When such effluents occur, they generally are included in industrial wastes, for example, those from tanning Domestic wastewater is collected from dwelling units, commercial buildings, and institutions of the community It may include process wastes of industry, groundwater infiltration, surface-water inflow, and miscellaneous waste liquids It is primarily spent water from building water supply, to which have been added the sanitary waste materials of bathroom, kitchen, and laundry (See Art 22.14.) Storm water is precipitation collected from property and streets and carrying with it the washings from surfaces Industrial wastes are primarily the specific liquid waste products collected from industrial processing but may contain small quantities of domestic sewage Such wastes vary with the process and contain some quantity of the material being processed or chemicals used for processing purposes Industrial cooling water when mixed with process water is also called industrial waste Industrial wastes, as distinguished from domestic wastes, are related directly to processing operations and usually are the liquid fraction of processing that has no further use in recovery of a product These wastes may contain substances that, when discharged into surface water or groundwater, cause some biological, chemical, or physical change in the water Organic substances exert a biochemical oxygen demand (BOD) of relatively high proportion compared with domestic waste It is not unusual in food processing to have wastes with a BOD of 1,000 to 5,000 mg/L or in the processing of edible oils to have 10,000 to 25,000 mg/L BOD The wastes may cause discoloration of a receiving stream, as in the release of dyes, or increase the temperature of the water, as in the case of a cooling tower or process-cooling water discharges Chemicals in the waste may be toxic to aquatic life, animals, or human populations using the water, or may in some way affect water quality by imparting taste or odor Phenols introduced into water in the parts-per-billion range can produce such marked taste that the water becomes unusable for many purposes Nitrogen and phosphorus, referred to as nutrients, may stimulate aquatic growth, and large concentrations of algae and other microorganisms in the receiving stream may be increased Some algae and other microorganisms are detrimental to water quality since they too produce taste, odor, color, and turbidity in the water Industrial wastes that contain large quantities of solids may produce objectionable and dangerous levels of sludge on the bottom of a stream or along the banks These add to the chemical, biological, and physical degradation of the stream Discharges containing grease or oil may render bathing beaches useless, interfere with nesting water fowl, and present extra problems of removal in watertreatment processes Wastes containing acids or alkalies may attack pier structures and water craft and produce serious toxic effects on aquatic life Some wastes, such as those containing copper, interfere with the normal processes of wastewater treatment and may, if mixed with municipal waste, render the whole treatment process inoperative Pretreatment of industrial wastes is often required to protect the sewers and treatment plant maintained by a municipal agency Toxic pollutants are controlled by EPA General Pretreatment Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.4 n Section Twenty Two Regulations, which contain limits on specific substances discharged by various industries Most municipalities have industrial pretreatment ordinances in effect Treatment of industrial wastes to the degree required to protect a receiving body of water is a requirement in all states; it may range from neutralization and other simple primary treatments to complete treatment or, in some instances, even an advanced stage of treatment to remove trace chemicals (see also Art 22.31) Combined wastes are the mixed discharge of domestic waste and storm water in a single pipeline Industrial waste may or may not be found in a combined waste (W W Eckenfelder, Jr., “Industrial Water Pollution Control,” and R A Corbitt, “Standard Handbook of Environmental Engineering,” McGraw-Hill Publishing Company, New York (www.books.mcgraw-hill.com); N L Nemerow, “Liquid Wastes of Industry: Theories, Practices and Treatment,” and R L Culp et al., “Advanced Wastewater Treatment,” Van Nostrand Reinhold Company, New York.) 22.3 Types of Sewers A sewer is a conduit through which wastewater, storm water, or other wastes flow Sewerage is a system of sewers The system may comprise sanitary sewers, storm sewers, or a combination of both Usually, it includes all the sewers between the ends of building-drainage systems and sewagetreatment plants or other points of disposal Sanitary sewers carry mostly domestic wastewater They may also receive some industrial wastes But they are not designed for storm water or groundwater Storm sewers are designed specifically to convey storm water, street wash, and other surface water to disposal points Combined sewers are sewers that carry both domestic wastewater and storm water They were constructed, generally in larger communities, in the early half of the 20th century, to save the higher construction cost of separate sanitary and storm sewers Combined sewers include diversion and overflow structures, which, when the combined sewer reaches its carrying capacity, discharge sanitary sewerage diluted with storm water, to a watercourse Combined sewers are no longer permitted to be built in the U.S The EPA has issued a national policy statement (40 CFR Part 122) entitled “Combined Sewer Overflow (CSO) Control Policy.” This policy establishes a consistent national approach for controlling discharges from CSOs to the Nation’s waters through the National Pollutant Discharge Elimination System (NPDES) permit program Contained in the Policy are provisions for developing appropriate, site-specific NPDES permit requirements for all combined sewer systems (CSS) that overflow as a result of wet weather events Building sewers, or house connections, are pipes carrying wastewater from the plumbing systems of buildings to a sewer or disposal plant In urban areas, the flow goes to a common sewer, which serves abutting property This conduit may be a lateral, one that receives wastewater only from house sewers A submain, or branch sewer, takes the flow from two or more laterals A main, or trunk sewer, handles the flow from two or more submains or a submain plus laterals An outfall sewer extends from the end of a collection system or to a treatment plant disposal point An intercepting sewer receives dry-weather flow and specific, limited quantities of storm water from several combined sewers A storm-overflow sewer carries storm-flow excess from a main or intercepting sewer to an independent outlet A relief sewer is one built to relieve an existing sewer with inadequate capacity Usually, domestic-wastewater or storm-water flow does not completely fill the conduit But all sewers may be filled at some time and must be capable of withstanding some hydraulic pressure Some types are always under pressure Force mains flow full under pressure from a pump Inverted siphons, conduits that dip below the hydraulic grade line, also flow full and under pressure 22.4 Estimating Wastewater Flow Before a sewer is designed, the community or area to be served should be studied for the purpose of estimating the type and quantity of flow to be handled Design should be based on the flow estimated at some future time, 25 to 50 years ahead, or at completion of the development The quantity and flow patterns of domestic wastewater are affected principally by population and population increase; population density and Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.5 density change; water use, water demand, and water consumption; industrial requirements; commercial requirements; expansion of service geographically; groundwater geology of the area; and topography of the area The quantity of domestic wastewater, however, generally is less than water consumption since some portion of water used for firefighting, lawn irrigation, street washing, industrial processing, and leakage does not reach the sewer Some of these losses, however, may be offset by addition of water from private wells, groundwater infiltration, and illegal connections from roof drains and sump pumps If the community to be served by the sewerage system already exists, the wastewater flow may be estimated from the gallons per capita per day (gcd) of water being consumed For a planned community, the estimate may be based on the gcd of water being consumed by an existing similar community Table 22.1 lists reported flows for several large United States cities Although flow may range from 70 to 130% of water consumption, designers often assume the average flow equal to the average water consumption or, for estimating purposes, 100 to 110 gcd The peak flow often is several times larger than the average The rate of flow of domestic wastewater varies with water use But short-term fluctuations tend to dampen out inasmuch as there is a time lag from the time of water use to the time the flow reaches the sanitary-sewer mains Hourly, daily, and seasonal fluctuations, though, affect design of sewers, pumping stations, and treatment plants Daily and seasonal variations depend largely on community characteristics In a residential district, greatest use of water is in the early morning A pronounced peak usually occurs about A M in the laterals In commercial and industrial districts, where water is used all day, a peak may occur during the day, but it is less pronounced At the outfall, the peak flow probably will occur about noon Wherever possible, measure flow in existing sewers and at treatment plants to determine actual variations in flow For residences housing families with both spouses working, weekend flows may be higher than weekday flows Industrial operations of a seasonal nature influence the seasonal average The seasonal and annual averages often are about equal in May and June The seasonal average may rise to about 125% of the annual average in late summer and drop to about 90% at winter’s end Peak flows may exceed 300% of average in laterals and at the treatment plant Several state health departments require that laterals and submains be designed for a minimum of 400 gcd, including normal infiltration (see below), and main, trunk, and outfall sewers, for a minimum of 250 gcd, including normal infiltration, and any known substantial amounts of industrial waste Inflow into Sewers n Water may inflow into a sewer system and service connections from such sources as roof, cellar, yard, area, and foundation drains, cooling-water discharges, drains from springs and swamps, manhole covers, cross connections from storm and combined sewers, catch basins, storm water, surface runoff, and street washes or drainage Inflow does not include infiltration into sewers Infiltration into Sewers n Water may infiltrate sewers through poor joints, cracked pipes, and walls of manholes Sewers in wet ground with a high water table or close to streambeds will have more infiltration than sewers in other locations Since infiltration increases the sewage load, it is undesirable The sewer design should specify joints that will allow little or no infiltration, and the joints should be carefully made in the field Some specifications limit infiltration to 500 gal per day per inch diameter per mile Often, enforcement agency specifications and requirements call for leakage tests Some states limit the net leakage to 500 gal/day per inch diameter per mile for any section of the system 22.5 Sewer Design Before a sanitary-sewer system can be designed, the quantities of wastewater to be handled and the rates of flow must be estimated This requires a comprehensive study of the community or area to be served (Art 22.4) Then, a preliminary layout of the sewerage can be made Also, pipe sizes, slopes, and depths below grade can be tentatively selected Preliminary drawings should include a plan of the proposed system and show, in elevation and plan, location of roads, streets, water courses, buildings, basements, underground utilities, and geology In addition, construction costs should be estimated After the preliminary design has been accepted, a survey should locate, in plan and elevation, all Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.6 n Section Twenty Two Table 22.1 Municipal Discharges* City State Bismarck Boise Bozeman Chicago West S.W Calumet North Side Cleveland East South Des Moines Detroit Houston North Side and 69th Sims Bayou Southwest Indianapolis S Belmont Rd Southport Rd Jacksonville Kansas City Los Angeles Hyperion Terminal Island Minneapolis New York Wards Island Hunts Point Bowery Bay Tallman’s Island Newtown Creek Oakwood Beach Oklahoma City (South) Philadelphia Northeast Southwest Portland Reno, Sparks Salt Lake City San Francisco North Point Richmond, Sunset South East Schenectady Seattle (West Point) St Louis ND ID MT IL Population served 37,000 75,000 21,000 Design flow mgd Design, gcd 4.95 10 5.2 133 133 247 2,900,000 604,000 1,243,330 1200 310 410 413 513 330 819,101 635,000 201,200 2,400,000 123 96 35 1290 150 151 174 538 460,000 359,463 173,433 55 48 30 120 134 173 539,108 205,516 164,000 418,000 120 57 17.5 85 223 277 107 203 3,000,000 115,000 434,000 420 14 218 140 122 502 1,270,000 770,000 725,000 460,000 2,100,000 105,000 218,900 180 150 120 60 310 15 30 142 195 166 130 148 143 137 1,240,000 925,000 377,800 110,000 181,650 175 136 100 20 45 141 147 265 182* 248 150 30 37 15.1 125 424 136 208 194 253 OH IA MI TX IN FL MO CA MN NY OK PA OR NV UT CA NY WA MO 353,840 220,030 177,450 77,985 494,000 (Table continued ) Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.7 Table 22.1 City Continued State Le May Bistle Point Washington Wichita DC KS Population served 849,783 988,357 1,780,000 275,000 Design flow mgd 240 251 240 45 Design, gcd 282 254 135 164 * From Computer Run 1974: National Water Quality Inventory, app C, vol II, Office of Water Planning and Standards, EPA 440/9-74- 001 existing structures and underground utilities that may affect the design Preferably, borings should be taken to determine soil characteristics along the alignment and at sites for structures in the system Physical characteristics of the area, including contours, should be shown on a topographic map Scale may be in to 200 ft, unless the number of details requires a larger scale Contours at 5- or 10ft intervals usually are satisfactory Elevations of streets should be noted at intersections and abrupt changes in grade Sufficient depth of soil cover is necessary to prevent damage from traffic loads Also, the sewers must be below the frost level Municipal and state regulations on cover should always be reviewed before a design for a specific location is undertaken The location of the sewers should be shown in elevation on profiles Horizontal scale may be in in 40 ft or in in 100 ft, depending on the amount of detail Vertical scale generally is 10 times the horizontal The final design should include a general map of the whole area showing location of all sewers and underground utilities and the drainage areas; detailed plans and profiles of sewers showing ground levels, sizes of pipe and slopes, and location of appurtenances; detailed plans of all appurtenances and structures; a complete report with necessary charts and tables to make clear the exact nature of the project; complete specifications; and a confidential estimate of costs for the owner or agency responsible for the project Extensive plans require tabulation of data beginning at the upper end of the system and proceeding downstream from manhole to manhole The addition to flow from connecting sewers should be included Approval of a supervising government agency, such as a county, parish, city, or state agency, usually must be obtained for the plans Sewer designers should be familiar with requirements for sewers in the locale in which work is to be done Design Flows n Unless force mains are required because sewage must be pumped, or inverted siphons are necessary because of a drop in terrain or encounters with obstacles, sewers usually are sized for open-channel flow Maximum flow occurs when a conduit is not completely full For example, for a circular pipe, maximum discharge takes place at about 0.9 of the total depth of the section Sewers, however, should be designed to withstand some hydraulic pressure For storm sewers, common practice is to permit pipe to carry design flow at full depth Sanitary sewers should be designed to carry peak design flow with a depth from half full for the smallest sewers to full for the larger sewers For example, sewers under 15 in in diameter are usually designed to flow half full during peak flow periods, whereas sewers from 15 to 60 in in diameter may be designed to flow three-quarters full and sewers larger than 60 in, to flow full Laterals may be designed for ultimate flow of the area to be served Submains may be designed for 10 to 40 years ahead Trunk sewers may be planned for long periods, with provision made in design for parallel or separate routings of trunks of smaller size to be constructed as the need arises Appurtenances may have a different life since replacement of mechanical equipment will be necessary Usually, they are designed for 20 to 25 years ahead, and a timetable of additions during that period is then scheduled in an overall improvement plan In general, flow may be assumed uniform in straight sewers Velocity changes, however, will occur at obstacles and changes in sewer cross Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.8 n Section Twenty Two section and should be considered in making hydraulic computations Velocity Formulas n Velocity of flow, ft/s, in straight sewers without obstructions may be estimated with satisfactory accuracy from the Manning formula V¼ C 2=3 1=2 R S n ð22:1Þ where n ¼ coefficient dependent on roughness of conduit surface R ¼ hydraulic radius, ft ¼ area, ft2, of fluid divided by wetted perimeter, ft S ¼ energy loss, ft/ft of conduit length; approximately the slope of the conduit invert for uniform flow C ¼ 1:486 (conversion factor to account for change from metric units used in development of the formula) (See also Art 21.9.) A common value for n is 0.013, suitable for well-laid brickwork, smooth concrete pipe, and vitrified clay pipe with liner plates For vitrified clay pipes without liner plates, and plastic and resin-lined pipes, 0.011 may be used for n for design purposes For corrugated-metal pipe, n may range from 0.011 for a spun asphalt lining to 0.02 for the plain pipe or pipe with a paved invert Smaller values of n than the preceding may be used for new smooth pipe, but the roughness, and value of n, is likely to increase with age The quantity of flow, ft3/s, is given by ultimate size, may be much smaller than design flow Actual velocity then may be less than the selfcleaning velocity For example, suppose a circular pipe is sized and sloped to handle design flow when flowing full at ft/s This velocity will also be maintained when the pipe is flowing half full to full But if the depth of flow drops to one-third the diameter, the velocity will decrease to about 2.4 ft/s; and at a depth 0.2 of the diameter, velocity declines to about 1.8 ft/s Table 22.2 gives the hydraulic characteristics of circular pipe It enables the quantity and velocity of flow to be computed for a circular pipe flowing partly full, when the respective values for the pipe flowing full are known The quantity, ft3/s, for flow full may be estimated from Q¼ 0:463 8=3 1=2 d S n ð22:3Þ and the velocity for flow full from V¼ 0:59 2=3 1=2 d S n ð22:4Þ where d ¼ inside diameter of pipe, ft Table 22.3 lists the quantities and slopes given by these formulas for various velocities and diameters Information such as that in Tables 22.1 to 22.3 may be stored in computer memories for design use Programs for application of the data are available commercially ð22:2Þ Minimum Pipe Size n In many cities, in is the minimum diameter of sewer permitted, and in large cities and metropolitan areas 10 in may be the minimum In any case, pipe smaller than in in diameter should not be used because of the possibility of stoppages Minimum Velocity n Velocity should be at least ft/s, and preferably 2.5 ft/s, in sanitary sewers to prevent settlement of solids Slopes and cross sections of sewers should be chosen to achieve this or a larger velocity for design flows Where sewers are sized for lower velocities than recommended minimums, provision for flushing and removal of obstructions should be made in the design Maximum Velocities n High velocities in sewers also should be avoided because the solids carried in the flow may erode the conduit A usual upper limit for sanitary sewers is 10 ft/s For velocities in that range, though, lining at least the lower portion of the sewers with abrasion-resistant material, such as vitrified-clay blocks, is advisable Q ¼ AV where A ¼ cross-sectional area of flow, ft Slopes n Pipe slopes generally should exceed the minimum desirable for maintaining minimum velocity for design flow since actual flows, especially before a development reaches its Energy Losses n The assumption of uniform, open-channel flow in sewer design implies that the hydraulic grade line, or water surface, will parallel the sewer invert This may quite often be true But where conditions exist that change the slope of the Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.9 Table 22.2 Hydraulic Characteristics of a Circular Pipe Depth of flow Inside diameter Partial area Total area Quantity, ft3 =s; partly full Quantity; ft3 =s; flowing full Velocity partly full Velocity flowing full 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.60 0.70 0.80 0.90 0.95 1.00 0.019 0.052 0.094 0.143 0.196 0.252 0.312 0.374 0.437 0.500 0.627 0.748 0.858 0.950 0.982 1.000 0.005 0.021 0.049 0.088 0.137 0.195 0.262 0.336 0.416 0.500 0.671 0.837 0.977 1.067 1.075 1.000 0.25 0.40 0.52 0.62 0.70 0.77 0.84 0.90 0.95 1.00 1.07 1.12 1.14 1.12 1.09 1.00 water surface, the carrying capacity of the sewer will change, regardless of the constancy of the invert slope This should be taken into account in hydraulic computations for flow near intersections of large sewers, any structure combining the flow from two or more sources, interchange of velocity and pressure head, and submerged outlets at outfalls In curved sewer lines, allowance must be made for larger energy losses than in straight sewers The energy losses may be determined by application of formulas found in references on hydraulics To account for the energy loss due to change in direction of sewers at manholes, the invert in the manhole may be dropped about 0.04 ft If the sewer increases in size at the manhole, the design-flowdepth points of the pipes may be set at the same elevation The invert drop also may offset head losses due to size changes Thus, it reduces the danger of the flow backing up and building up pressure If the sewer size decreases at the manhole, pipe invert elevations may be kept the same example, an egg shape, with the small end down, offers a rapidly decreasing cross-sectional area for decreasing flows Since, for a given quantity of flow, velocity is inversely proportional to area, velocity in an egg shape does not fall off so rapidly with decreasing flow as in other shapes But cost of constructing such curved sections may be higher than that for simpler shapes Often, a compromise shape is chosen, one that has favorable hydraulic characteristics and relatively low cost For this reason, circular sewers generally are used, especially for prefabricated conduit This shape provides the maximum cross-sectional area for the volume of material in the wall and has fair hydraulic properties (Table 22.2) But because of the roundness, there is added cost in bedding circular pipe compared with shapes with a flat bottom Figure 22.1 shows some typical shapes that have been used for large reinforced concrete sewers The inverts usually are curved or incorporate a cunette, or small channel, to concentrate small flows to obtain desirable velocities Sewer Shapes n In selection of a sewer shape, designers sometimes favor one that permits higher velocities at both small and large flows For Sewer Materials n Sewers should be made of materials resistant to corrosion and abrasion and with sufficient strength to resist hydraulic pressure, Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.10 n Section Twenty Two Table 22.3 Quantities, Velocities, and Slopes for Circular Sewers, Flowing Full* Velocity, ft/s Dia, in 10 12 15 18 21 24 27 30 33 36 42 48 54 60 66 72 78 84 90 96 108 120 Qz Sz Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S Q S 2.0 3.0 4.0 5.0 6.0 7.0 8.0 0.70 3.3 1.1 2.5 1.6 1.9 2.5 1.4 3.5 1.1 4.8 0.92 6.3 0.77 8.0 0.66 9.8 0.57 11.9 0.50 14.1 0.45 19.2 0.36 25.2 0.30 31.8 0.26 39.2 0.23 47.6 0.20 56.5 0.17 66.4 0.16 77.0 0.14 88.4 0.13 101 0.12 127 0.10 157 0.09 1.1 7.5 1.6 5.6 2.4 4.4 3.7 3.2 5.3 2.5 7.2 2.1 9.4 1.7 11.9 1.5 14.7 1.3 17.8 1.1 21.2 1.1 28.9 0.82 37.7 0.68 47.7 0.59 58.8 0.51 71.3 0.45 84.7 0.40 99.5 0.36 115 0.33 133 0.30 151 0.27 191 0.23 236 0.20 1.4 13.3 2.2 9.9 3.1 7.8 4.9 5.8 7.1 4.5 9.6 3.7 12.6 3.1 15.9 2.6 19.6 2.3 23.8 2.0 28.3 1.8 38.4 1.5 50.3 1.2 63.6 1.0 78.5 0.90 95.1 0.80 113 0.71 133 0.64 154 0.58 177 0.53 201 0.48 254 0.41 314 0.36 1.8 20.8 2.7 15.5 3.9 12.1 6.1 9.0 8.8 7.1 12.0 5.8 15.7 4.8 19.9 4.1 24.5 3.6 29.7 3.1 35.4 2.8 48.1 2.3 62.8 1.9 79.5 1.6 98.1 1.4 119 1.2 141 1.1 166 0.99 192 0.91 221 0.83 252 0.76 318 0.64 392 0.56 2.1 30.0 3.3 22.3 4.7 17.5 7.4 13.0 10.6 10.1 14.4 8.3 18.8 7.0 23.9 5.9 29.4 5.2 35.7 4.5 32.4 4.0 57.7 3.3 75.4 2.7 95.4 2.4 118 2.0 143 1.8 170 1.6 199 1.4 231 1.3 265 1.2 302 1.1 381 0.93 471 0.81 2.4 40.7 3.8 30.3 5.5 23.8 8.6 17.8 12.4 13.8 17.8 11.3 22.0 9.5 27.9 8.1 34.4 7.0 41.7 6.2 49.5 5.5 67.3 4.5 88.0 3.7 111 3.2 137 2.8 166 2.4 198 2.2 232 2.0 270 1.8 309 1.6 352 1.5 444 1.3 549 1.1 2.8 53.2 4.4 39.6 6.3 31.0 9.8 23.0 14.2 18.1 19.2 14.7 25.2 12.4 31.9 10.5 39.3 9.2 47.6 8.1 56.6 7.2 76.9 5.8 101 4.9 127 4.2 157 3.6 190 3.2 226 2.8 266 2.5 308 2.3 353 2.1 402 1.9 508 1.7 628 1.5 *From Manning formula [Eqs (22.3) and (22.4)] for n ¼ 0:013 For other values of n, multiply slopes given in the table by n=0:013; multiply quantities and velocities by 0:013=n Velocities less than ft/s are not recommended † Q ¼ quantity of flow ft3/s S ¼ slope, ft/1000 ft ‡ Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.60 n Section Twenty Two treatment Cooling water, for example, can be segregated from high-strength wastes, thereby reducing the size of the treatment plant Process wastes have a wide range of flow from hour to hour, depending on the operation Hence, it may be necessary to provide equalization or holding tanks to produce a more uniform flow to be treated over a 24-h period This is more efficient than treatment units designed to handle maximum flows produced during an 8-h shift It is also possible with equalization tanks to mix wastes of different characteristics, such as acids and alkalies, and obtain a neutralized waste Peak solids production and BOD may also be reduced or regulated Industrial wastes may be placed in general classifications, such as food processing, textile and apparel manufacture, chemical manufacture, and basic materials manufacture, including pulp and paper, iron and steel, metal plating, oil processing, glass, plastic, and rubber production and processing Table 22.8 indicates some characteristics of waste typical of the several classifications When preparing for treatment of any specific waste, an engineer should see that the waste is sampled over a sufficient time period to include major variations introduced by process operation Treatment of process wastes may require a series of methods selected to accomplish certain degrees of treatment that would ultimately produce an effluent acceptable for discharge to a receiving stream These methods may include, in order: Pretreatment to reduce temperature, neutralize the wastes, and remove fibers and other coarse solids by screening Primary treatment to remove settleable solids Secondary treatment by biological processes applied to biodegradable wastes Secondary treatment with chemicals for chemical conversion, precipitation and removal of solids, and oxidation or reduction of substances contained in the waste Preconditioning or secondary treatment by anaerobic digestion to produce a biochemical conversion of substances Ion exchange, dialysis, reverse osmosis, or evaporation to remove inorganic solids or recover chemicals Chlorination for oxidation or disinfection purposes Various forms of irrigation, lagooning, or algal oxidation ponds It is frequently necessary to select theoretically best combinations of treatment for a process waste and to follow up the selection with pilot-plant operations to establish the parameters of design for the full-scale treatment plant Employment of advanced waste-treatment methods may be necessary for specified purposes, such as removal of trace metals, control of phosphorus- and nitrogenbearing compounds, and reduction of excessive amounts of suspended solids Several methods of treatment are described in Arts 22.19 to 22.23, 22.25, 22.26, and 22.27 Discharge Permits n In accordance with the Clean Water Act (Art 22.1), anyone discharging wastewater to the waters of the United States is required to obtain a permit for that purpose from the Environmental Protection Agency (EPA) or a designated state, under the National Pollutant Discharge Elimination System (NPDES) Permits usually are written for a specific term (up to years) and contain effluent limitations and monitoring requirements for each discharge point One objective is to have industry apply the best available technology economically achievable for controlling toxic pollutants and the best conventional pollutant-control technology for conventional pollutants (Industries discharging to municipal sewer systems, however, are not required to obtain NPDES permits Control of pollutants from these sources is achieved through EPA General Pretreatment Regulations, which set specific industry-byindustry standards with specific limits on effluents.) EPA has established a list of hazardous wastes from specific industries, such as electroplating wastes or air-pollution-control scrubber sludges from coke ovens and blast furnaces If a waste is on this general list, the producer must treat it as a hazardous waste EPA has also compiled a list of toxic chemicals that are often contained in industrial wastes Wastes containing any of these chemicals must be treated as a hazardous waste But even if a waste is not on either list, it should be considered hazardous if it is radioactive, ignitable, corrosive, reactive, or toxic Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.61 Table 22.8 Types and Characteristics of Industrial Wastes* Type of waste Canning Corn products Beans Peaches Tomatoes Milk products General dairy Fermentation Brewing Laundry Roofing Paperboard General slaughterhouse Paper mill Paperboard Textile Cotton sizing Basic dyeing Rayon viscose Wool dyeing and scouring Vegetable oils Acidulating waste Unit Ton Case no cans Ton Ton 1,000 lb raw milk Volume, gal per unit BOD, lb per unit Suspended solids, lb per unit 12,000 35 2,610 227 19.5 200.0 29.2 8.4 30.0 60.0 13.0 2.9 340 570 Population equivalent per unit 186 0.35 280 82 540 10 barrel beer 100 lb dry wash 204 400+ 1.2 1,250+ 0.6 500+ 12 20– 25 Ton animal 36,075 360 18.2 7.7 144.0 3.2 125 74 Ton pulp 14,000 1,000 lb goods processed 1,000 lb goods processed 1,000 lb product 1,000 lb product ton oil 121 84 60.0 18,000 90 140 240,000 110 125 9.6 800 1,500 385 0.5 10 * From E B Besselievre and M Schwartz, “The Treatment of Industrial Wastes,” 2d ed., McGraw-Hill Book Company, New York Hazardous Wastes n Options for disposal of hazardous wastes include recovery for reuse, incineration, landfills with the option of fixation before landfilling, land treatment, mine storage, and deep-well injection Radioactive wastes are subject to severe restrictions when the receiving body of water may be used for human consumption, recreational bathing, fish propagation for food, or plant irrigation Federal and state regulations should be reviewed whenever radioactive wastes are to be disposed Permissible concentrations of radioactive material in water are usually specified in microcuries per milliliter of water Procedures that have been used for the treatment of radioactive wastes include concentration and storage, and dilution and disposal Burial after required decay may follow the first and discharge to sewers or streams may follow the latter Low-activity material may be diluted, while high-activity material, requiring long storage periods, may be safely enclosed in containers and buried or stored in isolated caves or other underground facilities Concentration of radioactive wastes before storage may be accomplished by coprecipitation The radioactive sludge concentrate is then removed, packaged, and buried Evaporation is widely used for concentration of low-activity wastes Condensate may be released to a sewer The sludge is transferred to polyethylene- Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.62 n Section Twenty Two lined drums for burial Cation exchange with synthetic resins may be used on small liquid volumes having low solids concentration and low radioactivity levels Land treatment is suitable for wastes that can be biodegraded, chemically altered, immobilized, or deactivated by interaction with soil Studies should be made to determine acceptable waste-loading rates and monitoring requirements Provisions should be made to prevent discharge from the site of untreated water or for treatment of such water Unless contaminated soil is to be removed and transported to a treatment or disposal facility, applications of wastes containing metals should be controlled so that no toxic hazard will result After the last load of waste has been placed, the site should be stabilized with vegetation or capped as required for a landfill to control infiltration and erosion For deep-well disposal, liquid wastes are injected through shafts into deep subsurface geologic formations, where the wastes will be contained The technique has long been used by the oil industry for disposal of brine Care must be taken that groundwater which might be required for use above ground will not be polluted For landfills, see Art 22.31; for incineration, see Art 22.32 (W W Eckenfelder, Jr., “Industrial Water Pollution Control,” H M Freeman, “Standard Handbook of Industrial Waste Treatment and Disposal,” and S C Reed and E J Middlebrooks, “Natural Systems for Waste Management and Treatment,” McGraw-Hill Publishing Company, New York (www.books.mcgraw-hill.com); J R Conner, “Chemical Fixation and Solidification of Hazardous Wastes,” R L Culp et al., “Advanced Wastewater Treatment,” J Devinney et al., “Subsurface Migration of Hazardous Wastes,” E J Martin and J H Johnson, “Hazardous Waste Management Engineering,” and N Nemerow and A Dasgupta, “Industrial and Hazardous Waste Treatment,” Van Nostrand Reinhold Company, New York.) 22.31 Sanitary Landfills Refuse collected from households, commercial establishments, and industrial plants must be disposed of at minimum cost and without creating health hazards or nuisances One solution is a sanitary landfill, which requires daily compaction of refuse and daily placement of an earth cover to 12 in thick The cover is increased to ft when filling has been completed The method is suitable where low-cost land is available within convenient hauling distance of the contributing population and good soil is available for the earth cover Other factors to consider in selection of a landfill site are possible adverse effects on quality of surface water, groundwater, and air and potential for subsurface migration of leachates Also, a site should not be located within 200 ft of a fault nor within a 100-year floodplain Refuse comprises all solid wastes except body wastes It may consist of garbage, ashes, rubbish, street cleanings, dead animals, abandoned automobiles and solid market and industrial wastes Garbage consists of putrescible wastes resulting from processing, handling, preparation, cooking, and consumption of food Rubbish consists of solid wastes other than ashes, body wastes, and garbage from domestic, commercial, and institutional sources About 14 acre-ft, including cover, per 10,000 population per year of operation will be required for sanitary landfill Sufficient land should be available to ensure area for a preplanned period of to 10 years The area needed can be derived from an estimate of volume required computed from V¼   R P 1À þ Cv D 100 ð22:33Þ where V ¼ volume, yd3 per capita per year, of sanitary landfill R ¼ weight of refuse, lb per capita per year, to be handled at landfill D ¼ average density of refuse, lb/yd3 P ¼ percentage reduction of refuse volume from compaction Cv ¼ volume, yd3, of cover material required (6- to 12-in-thick intermediate layers, temporary sides, front slope, and top, and at least 24 in on all finished surfaces) Cv varies from 17% of the refuse volume for deep fills to 33% for shallow fills It may be assumed at 25% in estimates For this value, the Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.63 required volume of landfill may be estimated from V ¼ 1:25   R P 1À D 100 ð22:34Þ Drainage of the site before, during, and after filling should be planned in advance Provision should be made for windbreaks to keep dust, paper, and other light objects from being blown away from dumping areas and becoming a nuisance Also, the final disposition of the site should be planned in advance Parks, recreational areas, and outdoor storage are suitable end uses for landfills Choice of end use should be influenced by the uncertain settlement characteristics of such fills and the objectionable odors that may be released where excavations are made A covered fill may be odorless, but excavation may be hazardous and expensive because of the presence of obnoxious toxic and flammable gases produced by decomposing refuse Soil used for cover should not have a high proportion of sand or clay or operation of trucks will be hindered Clay also is difficult to handle, and when dry, it cracks, providing openings for rodents, insects, and air A sand-clay-loam mixture with about 50% sand has been found satisfactory Landfills must meet a number of restrictive requirements imposed by state regulatory agencies An impermeable liner is typically placed at the bottom of the landfill to prevent leachate from entering and contaminating groundwater A drainage system consisting of perforated pipe in a gravel drainage layer is placed at the bottom of the landfill, above the liner, for leachate collection Leachate is either treated on site or transported to a wastewater treatment plant for treatment The specific requirements in each state should be ascertained by the engineer Usually, the engineer is required to submit a plan and report on the specific areas to be filled, schedule of filling, site preparation, sources and types of materials to be used as cover, and subbase The plan should also include details on application of cover material; composition of waste; final grades; handling of surface water and fill drainage, including the method of collection and treatment of leachate to prevent groundwater or surface-water pollution; erosion control; nuisance control; air-pollution prevention measures; method of record keeping; and, in general, any data required to ensure that environmental impact (Art 22.34) will not be adverse or unacceptable to the enforcement agency Landfills should be provided with means for controlling leachate and runoff Leachate is contained by placing an impermeable liner under and around the site Choice of liner depends on the nature of the wastes to be discharged Liners often are concrete, synthetic fabrics, or impermeable clay (R A Corbitt, “Standard Handbook of Environmental Engineering,” McGraw-Hill Publishing Company, New York (books.mcgraw-hill com); American Public Works Association Committee on Refuse Disposal, “Municipal Refuse Disposal,” APWA, 2345 Grand Boulevard, Suite 500, Kansas City, MO 64108-2641 (www.APWA net); D G Wilson, “Handbook of Solid Waste Management,” and A Bagchi, “Design, Construction and Monitoring of Sanitary Landfills,” Van Nostrand Reinhold Company, New York.) 22.32 Incineration of Refuse and Hazardous Wastes Where land is costly or unavailable for sanitary landfill, municipalities may resort to incineration for refuse disposal Refuse comprises all solid wastes except body wastes The material is not homogeneous, and its characteristics vary considerably Fuel value may range from 600 to 6500 Btu per pound of refuse, as fired Moisture content influences this value significantly Controlled high-temperature (16008F or more) incineration is an effective alternative to traditional methods of disposal of hazardous wastes Such incineration is capable of converting many hazardous wastes into innocuous gases and ash and often recovering some of the energy produced by combustion The process must be controlled to prevent emission to the atmosphere of hazardous combustion products or products of incomplete combustion EPA regulations require incinerator operators to obtain a permit to burn the specific wastes to be treated Basic standards call for 99.99% destruction and removal efficiency for each principal hazardous component of the waste; 99% removal of HCl from the exhaust, when the wastes contain more than 0.5% of organically bound chlorine; and emission not exceeding 180 mg/m3 of exhaust gas Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.64 n Section Twenty Two Refuse n In incineration of refuse, volatiles are driven off by destructive distillation They ignite from the heat of a combustion chamber (Fig 22.29) Gases produced pass through a series of oxidation changes in which time-temperature relationship is important They must be heated above 14008F to destroy odors Combustion products ultimately discharge from a stack at 8008F or less, usually after passing through an expansion chamber, fly-ash collector, and wet scrubbers Normally, only submicron- and the smaller micron-size particles should escape with the flue gases Dust emissions may be in the range of to lb per ton of refuse charged for a well-operated unit equipped with scrubbers Air needed ranges from to lb per pound of refuse burned For nonhomogeneous wastes, up to 200% of theoretical requirements may be needed for combustion The air provides oxygen for combustion of organic matter, helps dry wet refuse, and mixes with organic gases But the air cools the gases if too much dry material is being burned Air should be passed over the refuse and through it from under the grates Incinerators generally are rated in accordance with the estimated weight of refuse they are capable of burning in 24 h Loading rates range up to slightly over 100 lb of refuse per hour per square foot of grate area for incinerators with mechanical stoking Small incinerators for apartment buildings and institutions are loaded at much lower rates Standards of the Incinerator Institute of America suggest loading rates for domestic refuse, lb/ (h ft2), of 20 in 100-lb/h burning units to 30 in 1000lb/h burning units Fig 22.29 Several types of incinerators are available from manufacturers Kiln shape may be round or rectangular The kiln may be stationary or rotate about a horizontal axis The hearth may be horizontal and fixed, with grates; traveling, with grates; multiple; step movement; or barrel-type rotary (Fig 22.29) Some types have drying hearths Feed may be continuous, stoker, gravity, or batch For rational design of incinerators, the engineer should know or estimate such characteristics of the refuse to be burned as weight, water content, percentage of combustible and inert material, and Btu content Available heat from the refuse must be balanced against heat losses due to radiation, excess air, flue gas, and ash Heat balance can be calculated from several estimates based on averages Manufacturers of each type of incinerator recommend sizes for various conditions Furnace volume may be approximated by allowing 20,000 Btu/ft3, and grate area by allowing 300,000 Btu/ft2 Secondary combustion chambers permit combustion to continue to completion Volumes of such chambers range from 10 to 25 ft3/ton of rated capacity Expansion chambers and other air-cleaning devices remove fly ash and other particles carried out of the furnace by gases Expansion chambers are desirable where a stack serves more than one furnace Gas velocities in secondary chambers should not exceed 10 ft/s Stacks should be designed for gas velocities of about 25 ft/s with maximum air As a rough approximation, 0.3 ft2 of stack area may be required per ton of rated capacity Stack heights usually range from 100 to 180 ft Height is desirable for Schematic of refuse incinerator Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.65 creating natural draft and for dispersion of gases in the atmosphere Hazardous Wastes n For incineration of hazardous wastes, liquid-injection incinerators are usually used Vertically aligned units are generally used for wastes high in organic salts and yielding large quantities of ash Horizontal incinerators are preferable for wastes producing small quantities of ash A fluidized-bed incinerator is one alternative (Fig 22.30) It is a vertical steel cylinder with a grid supporting hot sand through which combustion air flows at a velocity high enough to keep the sand in suspension The sand is heated by an air preheat system, plus fuel-fired combustion Dewatered sludge, injected into the sand, is burned at temperatures between 1400 and 15008F if it does not contain hazardous wastes and over 16008F if it does Ash is carried off with the exhaust gases and is captured in air-pollution-control devices This equipment makes more efficient use of fuel than the multiple-hearth furnace (Art 22.24), which, however, is simpler to operate and maintain Rotary kiln incinerators are another alternative They can be used to burn solid and containerized wastes, slurries, and liquids Other alternatives include starved-air/pyrolysis incinerators, incineration in high-temperature industrial facilities, such as cement kilns and industrial boilers; incineration at sea on special ships or off-shore platforms; and mobile incineration employing special heavy-duty truck trailers Because facilities that incinerate wastes and produce energy for other applications are exempt from Resource Conservation and Recovery Act Fig 22.30 Schematic of fluidized-bed incinerator Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.66 n Section Twenty Two emission-control regulations, there is an incentive to cofire wastes in industrial facilities Studies indicate that organic wastes can be used to replace on the average up to 15% of cement-kiln fuel (E T Oppelt, “Thermal Destruction Options for Controlling Hazardous Wastes,” Civil Engineering, September 1981.) Incinerators should be designed to ensure that the wastes, auxiliary fuel if needed, hot combustion gases, and combustion air come into intimate contact and that the wastes stay long enough in the combustion chamber to be destroyed For this purpose, high-efficiency burners should be used, liquid-waste feed should be atomized for insertion in the combustion chamber, and excess combustion air should be supplied and controlled to maintain turbulence in that chamber Emission-control devices should be used to limit emission of hazardous exhausts Afterburners may be employed to provide additional combustion volume at high temperatures to burn incompletely combusted exhaust products Scrubbers (Art 22.33) are advantageous for removal of particulates, acid gases, and residual organics from the exhaust (“Engineering Handbook on Hazardous Waste Incineration,” Environmental Protection Agency, National Service Center for Environmental Publications, P.O Box 42419, Cincinnati, OH 45242 (www.epa.gov/epahome/publications.htm); C R Brunner, “Handbook of Incineration Systems,” and G Tchobanoglous, “Solid Wastes: Engineering Principles and Management Issues,” McGraw-Hill Publishing Company, New York (www.books.mcgraw-hill.com); D G Wilson, “Handbook of Solid Waste Management,” and E J Martin and J H Johnson, Jr., “Hazardous Waste Management Engineering,” Van Nostrand Reinhold Company, New York; H B Palmer and J M Beer, “Combustion Technology,” Academic Press, New York (www.academicpress.com).) 22.33 Air-Pollution Control Air pollution exists when one or more substances, such as dust, fumes, gas, mist, odor, smoke, or vapor, are present for a sufficient time in the atmosphere in quantities and with characteristics injurious to life or property, or detrimental to comfortable enjoyment of life and property These pollutants derive from numerous sources They may be roughly classified as natural, industrial, transportation, agricultural, commercial and domestic heat and power, municipal activities, and fallout Natural sources include water droplets or spray evaporation residues, windstorm dusts, meteoric dusts, surface detritus, and pollen from weeds Industrial sources include process waste discharges, ventilation products from local exhaust systems, and heat, power, and waste disposal by combustion processes Transportation sources include discharges from motor vehicles, rail-mounted vehicles, airplanes, and vessels Agricultural sources include applications of insecticides and pesticides and burning of vegetation Commercial and domestic heat and power sources include gas-, oil-, and coal-fired furnaces used to produce heat for dwellings, commercial establishments, and utilities Municipal activity sources include refuse disposal, liquid-waste disposal, road and street paving, and fuel-fired combustion operations Fallout comprises radioactive pollutants suspended in the air after a nuclear explosion Since pollutants are contributed by many sources, air pollution is always present but in varying degrees In effect, pollution from natural sources is a base line with which total pollution can be compared The major correctable sources of pollution are associated with community activity, rather than rural activity, because community air generally is more polluted Environment is made less desirable by pollutants Hence, there is ample reason to conserve air as a resource, in many ways parallel to the need for conservation of water Air-pollution control requires knowledge of what constitutes an ideal atmosphere This leads to establishment of criteria for clean air and standards setting limits on the permissible degree of pollution Control also requires means for precise measurement of pollutants and practical methods for treating polluting sources to prevent undesirable emissions In addition to its adverse effects on health, air pollution also is objectionable because of its contribution to reduced visibility In many parts of the world, burning of soft coal yields particles that combine with fog to produce smog, a mixture that at times reduces visibility to zero Smog is Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.67 created when microscopic water droplets condense about nucleating substances in the air to form aerosols These are liquid or solid, submicron-size particles dispersed in a gaseous medium In an atmosphere with an aerosol concentration of about mg/m3, visibility may be limited to 1600 ft There would be about 16,000 particles per milliliter restricting visibility by scattering light Coal is only one source of nucleating particles that are responsible for smog Chemical conversion of reaction products in the air also produces nucleating substances that grow large enough to cause light scattering Converted sulfur dioxide too becomes a nucleating substance as it oxidizes and hydrolizes to form sulfuric acid mist The most desirable means of controlling air pollution is to prevent contaminants from getting into the atmosphere Complete elimination of air pollution, however, is not always practicable But there are many means for reducing it Sulfur dioxide release, for example, can be decreased by use of a fuel with low sulfur content An industrial process with a gaseous effluent can be changed to eliminate the gaseous waste Aerosols and particles can be removed from a gas stream by air-cleaning equipment Air-Quality Standards n In accordance with the Clean Air Act (Art 22.1), the Environmental Protection Agency (EPA) develops National Ambient Air Quality Standards These list the maximum amount of an air pollutant that can be present with an adequate margin of safety in protection of public health and welfare and that will not cause significant deterioration of air quality in areas where ambient standards have been attained Check with EPA for the latest criteria because they are subject to change when appropriate for public protection EPA also develops National Emission Standards for Hazardous Air Pollutants to limit emissions that cause or contribute to air pollution The standards apply to both new and existing sources For example, for restricting emissions of inorganic arsenic from smelters, EPA requires high-efficiency particulate controls operated at optimum temperature for arsenic condensation for process gas streams, effective capture systems, and highefficiency particulate controls for several sources of fugitive emissions In addition, EPA develops New Source Performance Standards based on the best systems that have been demonstrated to reduce emissions continually, taking into account costs and energy requirements The standards apply to new sources and existing sources that have been modified after establishment of EPA criteria For example, EPA has issued limitations for the following: SO2 and NO2 emissions from industrial boilers NO2 emissions from diesel engines Hydrocarbon emissions from dry cleaning equipment Emission of volatile organics from numerous processes and storage units Evaporative emissions from metal cleaning and degreasing operations Particulate emissions from numerous processes, including battery manufacturing, processing of minerals prior to metal reduction, phosphate rock processing, coke ovens, manufacture of asphalt roofing and gypsum, and combustion of wood, municipal solid wastes, refuse-derived fuels, and bagasse—alone or combined with fossil fuels Air-Cleaning Devices n Sizes of substances to be eliminated (Table 22.9) are a major factor in selection of air-cleaning devices Coarse solids can be removed by screens Particles down to 10 mm in diameter can be settled out in settling chambers with expanding cross section for velocity reduction to under 10 ft/s Particles between 10 and 200 mm can be removed in cyclone separators, with an efficiency of 50 to 90% In this equipment, the gas to be cleaned is injected tangentially into a cylindrical chamber The gas spirals downward, then upward through the vortex at high velocity, and exits at the top Before the gas leaves, however, particles are centrifuged out, hit the side walls, and drop to the conical bottom of the chamber Particles 10 mm in diameter or smaller may be removed with filters made of cloth, metal, or glass fiber But air or gas velocities leaving such filters are low For dry fiber filters, efficiency may be only about 50% The efficiency of such filters, however, may be increased by application of a viscous coating, such as an oil with low volatility Filters made of cloth usually are tubular bags, which trap particles as air or gas passes through Many bags may be enclosed in a large chamber When loaded with dust, they are shaken, and the dust falls into a Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.68 n Section Twenty Two Table 22.9 Approximate Sizes of Particles in Aerosols, Dusts, and Fumes Type of Particle Tobacco smoke Rosin smoke Carbon black Zinc oxide fumes Magnesium oxide smoke Metallurgical fumes Viruses Oil smoke Pigments Ammonium chloride fumes Alkali fumes Metallurgical dust Sulfate mist Spray-dried milk Bacteria Pulverized-coal fly ash Fog Sulfuric acid concentrator Cement dust Sulfide ore for flotation Foundry dusts Stoker fly ash Pulverized coal Ground limestone Mist Size Range, Microns 0.01– 0.2 0.01– 1.1 0.01– 0.3 0.01– 0.4 0.01– 0.5 0.01– 1.3 0.01– 0.05 0.03– 1.0 0.09– 0.1– 1.4 0.1– 1.6 0.1– 200 0.5– – 10 – 12 – 60 – 50 1.1– 11 – 200 – 300 – 1000þ 10– 90 10– 500 30– 900 50– 600 hopper Bag filters remove 99% of particles larger than 10 mm Filters packed with activated charcoal are used to absorb gases Wet collectors or scrubbers remove particles to mm in size These devices also may remove watersoluble gases In a scrubber, the gas to be cleaned may pass through a countercurrent water flow The water may be sprayed or atomized The scrubber may have deflectors to improve mixing of the gas and water Chemicals may be added to the liquid to improve absorption Wet collectors often are used to clean air from kilns, roasters, and driers They also are used for processes producing fine dust, films, vapors, and mists in food, chemical, foundry, metalworking, and ceramic industries Scrubbers may be classified as dynamic precipitators, centrifugal collectors, orifice collectors, collectors with high-pressure nozzles, and packed towers In dynamic precipitators, dynamic or centrifugal forces, aided by water, clean the air In centrifugal collectors, centrifugal forces throw particles in the air against wetted collector surfaces After striking the surfaces, the particles fall to the bottom of the device and are removed Orifice collectors deliver large quantities of water to a collecting zone where dust is removed from the air by centrifugal force, impingement, or collision In collectors with high-pressure nozzles, air at 20,000 ft/min or more and water under 250 psi or more jet through venturi tubes The water breaks into a fine mist, increasing the probability of contact with tiny particles The turbulence disperses the water, causes quick impact with dust in the air, and removes the particles In packed towers, dust particles are removed when air flows upward through the packing, which usually is in the form of ceramic saddles, while water flows downward Ionizable aerosols and particles down to 0.1 mm in size can be removed by electrostatic precipitators with an efficiency of 80 to 99% These devices ionize particles in a gas passing by high-voltage electrodes Oppositely charged plates trap the particles To rid the plates of the particles, the current to the plates is interrupted or the plates are rapped Dispersal of Pollutants n When pollutants cannot be completely eliminated at the source, air pollution may be reduced by keeping the concentration of the pollutants low by dispersing them Whether atmospheric dilution is a suitable solution depends on the meteorology of a region, local topography, and building configurations Basic meteorological conditions of the atmosphere that must be considered include wind speed, direction, and gustiness, and vertical temperature distribution Under some conditions, humidity also is important In general, diffusion theories predict that ground concentration of a gas or fine-particle effluent with very low subsidence velocity is inversely proportional to the mean wind speed Vertical temperature distribution determines the distance from a stack of given height at which maximum ground concentration occurs Raising the temperature of gas leaving a stack is equivalent to increasing stack height Gas does not normally come to the ground under inversion conditions It may accumulate Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.69 aloft when the atmosphere is calm or nearly so and be brought down to the surface as the sun heats the ground in early morning Turbulence caused by buildings and topography usually is so complex that theoretical computation of the effect is impractical In some cases, however, model studies in wind tunnels have been used successfully to make predictions based on measurements of gas concentration and visible patterns of smoke Air Sampling and Monitoring n The degree of air pollution at any time and place is determined by taking air samples and analyzing them Airsampling methods may be classified as those sampling particles, inorganic metals and salts, inorganic gases, organic substances, and mixed miscellaneous substances Many automatic, recording, air-monitoring instruments are available They can be operated with few attendants and little manipulation It is generally necessary to calibrate automatic instruments against a standard wet chemical or physical measurement method Subsequent field calibration before, during, and after use may also be essential to maintain reliable test results Although there are many variations, particle-sampling devices generally use gravity or suction-type collection and pass the sample through thermal or electrostatic precipitators, impingers and impactors, cyclones, absorption and adsorption media, scrubbing apparatus, or filters of various materials, such as paper, glass, plastic, or cloth Several types of units with air pumps drawing air through paper tapes mounted on a spool are available The tape is moved automatically so that successive samples are taken for timed intervals on fresh paper In addition to standard wet chemical methods of measuring gases, there are many automatic or semiautomatic instruments designed to measure a spectrum (mass spectrometer) of one or more specific gases These employ many different analytical principles, such as electrical conductivity; potentiometry; coulometry; flame ionization, thermal conductivity; heat of combustion; colorimetry; infrared, ultraviolet, and visible light photometry; gas chromatography; atomic absorption and electron capture Stack sampling requires special techniques and usually a train of sampling devices to measure particles and gases High-volume samplers are used at many sampling network stations in the United States Electron microscopes may be used to examine aerosols and submicron particles Photoelectric meters are used to control alarm systems connected to stacks Combination instruments may be used for general sampling and location of emission sources Such devices measure wind direction and velocity and direct air samples into multiple sample units, each representing a wind-direction sector (R A Corbitt, “Standard Handbook of Environmental Engineering,” M L Davis and D A Cornwell, “Introduction to Environmental Engineering and Technology,” and H S Peavey and D R Rowe, “Environmental Engineering,” McGrawHill Publishing Company, New York (www books.mcgraw-hill.com); P O Warner, “Analysis of Air Pollutants,” and W L Faith and A A Atkinson, “Air Pollution,” John Wiley & Sons, Inc., New York (www.wiley.com); R O Gilbert, “Statistical Methods for Environmental Pollution Monitoring,” Van Nostrand Reinhold, New York.) 22.34 Environmental Impact Statements In accordance with the National Environmental Policy Act (Art 22.1), Federal agencies, departments, and establishments are required to prepare environmental impact statements in connection with proposals for legislative and other major Federal activities significantly affecting the quality of human environment It is essential that a draft statement be prepared, as early as possible, by the project engineer or other appropriate authorized person for review and comment The actions may include all or any of the following: Agency recommendations on their own proposals for legislation Agency reports on legislation initiated elsewhere but concerning subject matter for which the agency has primary responsibility Projects and continuing activities that may be a Undertaken directly by an agency Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.70 n Section Twenty Two b Supported in whole or in part through Federal contracts, grants, subsidies, loans, or other forms of funding assistance c Part of a Federal lease, permit, license, certificate, or other entitlement for use Decisions of policy, regulation, and procedure making Although it is possible that there can be exceptions, the following actions are generally considered major or environmentally significant: Actions whose impact is significant or highly controversial on environmental grounds Actions that are precedents for much larger actions that may have considerable environmental impact Actions that are decisions in principle about major future courses of action Actions that are major because of the involvement of several Federal agencies, even though a particular agency’s individual action is not major Actions whose impact includes environmentally beneficial as well as environmentally detrimental effects Contents of Environmental Impact Statements n Environmental impact statements must assess in detail the potential environmental impact of a proposed action The purpose of the statement is to disclose the environmental consequences of a proposed action That disclosure is designed to alert the agency decision maker (local, state, or Federal, or any combination of these), the public, and, perhaps on major works, Congress and the President to environmental risks involved Environmental impact statements should present: A detailed description of the proposed action, including information and technical data adequate to permit a careful assessment of environmental impact Discussion of the probable impact on the environment, including any impact on ecological systems and any direct or indirect consequences that may result from the action Any adverse environmental effects that cannot be avoided Alternatives to the proposed action that might avoid some or all of the adverse environmental effects, including analysis of costs and environmental impacts of these alternatives An assessment of the cumulative, long-term effects of the proposed action, including its relationship to short-term use of the environment versus the environment’s long-term productivity Any irreversible or irretrievable commitment of resources that might result from the action or that would curtail beneficial use of the environment When the final statement is prepared, it must also include any discussions, objections, or comments presented by Federal, state, and local agencies, private organizations, and individuals that addressed the subject during review of the draft statement Impact Statement Review n In general, any Federal, state, or local agency that has jurisdiction by law or specific expertise with respect to any environmental impact involved must be consulted for comments Agencies to be consulted include those having responsibilities for the following (state or local agencies may have additional agency review requirements): Water quality Air quality Weather modification Environmental aspects of electric energy generation and transmission Toxic materials, pesticides, and herbicides Transportation and handling of hazardous materials Wetlands, estuaries, waterfowl refuges, beaches Historic and archeological sites Flood plains and watersheds Mineral land reclamation Parks, forests, outdoor recreational areas and wildlife Soil and plant life, sedimentation, erosion, and hydrologic conditions Noise control and abatement Food additives, food sanitation, and chemical contamination of food products Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.71 Microbiological contamination Radiation and radiological health Sanitation and waste systems Transportation and air and water quality Environmental effects with special impact on lowincome neighborhoods Rodent control Urban planning, congestion in urban areas, housing and building displacement River and canal regulation and stream channelization In areas of environmental engineering activity, the principal government agency having responsibilities for reviewing impact statements is the Environmental Protection Agency As a matter of fact, any Federal agency having a jurisdiction that centers around air and water pollution, drinking water supplies, solid waste, pesticides, radiation, and noise may be involved Hence, engineers should ascertain specifically any agencies in addition to EPA that may have review responsibilities Engineers should also determine to what extent the state agencies dealing with the above areas have jurisdiction In addition, engineers should check with the appropriate regional and municipal planning agencies (See also Sec 14.) How to Prepare an Impact Report n There are several alternate formats of report that would contain all the pertinent information required under the Federal guidelines One method that has had technical acceptance is the base matrix, in which a series of actions that are part of a proposed project are related to the characteristics and conditions of the environment that are affected Under each of the actions proposed, a ranking from to 10 is placed to indicate impact magnitude, 10 being the highest order Correspondingly, under a diagonal in the box, a ranking from to 10 can be inserted concerning the importance of a specific impact as related to an environmental condition Any suitable form of text that will discuss the significance of these two interrelated indices should be acceptable A sample matrix illustrating these points is shown in Fig 22.31 One of the more complete diagrams for an information matrix was prepared by the United States Geological Survey in 1971 It appears as a separate attachment in Geological Survey Circular No 645 The basis for the preparation of this matrix is indicated in Table 22.10 In dealing with any particular project, the engineer can select from the matrix in Table 22.10 on either margin those conditions and actions applicable to the project It is then possible for the engineer to prepare an environmental impact document so that reviewing agencies can provide comments in an orderly fashion Within the format, it is important to present both present conditions and current trends, the alternate action proposed, and the impact either favorable or unfavorable that will result with and without the proposed action If unavoidable harm may result from the proposed action, the procedures for reducing the harmful effect, together with the ultimate benefits resulting even though some harm may be done, should be presented in full detail with objective substantiation of all statements Fig 22.31 Matrix used to demonstrate the environmental impact of proposed actions Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.72 n Section Twenty Two Table 22.10 Items for Inclusion in Environment Impact Matrix Top Margin: Proposed Actions That may Cause Environmental Impact A Modification of Regime a Exotic flora b Biological controls c Modification of habitat d Alteration of ground cover e Alteration of groundwater hydrology f Alteration of drainage g River control and flow modification h Canalization i Irrigation j Weather modification k Burning l Surface or paving m Noise and vibration B Land Transformation and Construction a Urbanization b Industrial sites and buildings c Airports d Highways and bridges e Roads and trails f Railroads g Cables and lifts h Transmission lines, pipelines, and corridors i Barriers including fencing j Channel dredging and straightening k Channel revetments l Canals m Dams and impoundments n Piers, seawalls, marinas, and sea terminals o Offshore structures p Blasting and drilling q Cut and fill r Tunnels and underground structures C Resource Extraction a Blasting and drilling b Surface excavation c Subsurface excavation and retorting d Well drilling and fluid removal e Dredging f Clear cutting and other lumbering g Commercial fishing and hunting D Processing a Farming D Processing (Continued ) b Ranching and grazing Left Margin: Existing Characteristics and Conditions of the Environment A Physical and Chemical Characteristics Earth a Mineral resources b Construction material c Soils d Land form e Force field and background radiation f Unique physical features Water a Surface b Ocean c Underground d Quality e Temperature f Recharge g Snow, ice, and permafrost Atmosphere a Quality (gases, particulates) b Climate (micro, macro) c Temperature Processes a Floods b Erosion c Deposition (sedimentation, precipitation) d Solution e Sorption (ion exchange, complexing) f Compaction and settling g Stability (slides, slumps) h Stress-strain (earthquake) i Air movements B Biological Conditions Flora a Trees b Shrubs c Grass d Crops e Microflora f Aquatic plants g Endangered species h Barriers i Corridors Fauna a Birds b Land animals including reptiles c Fish and shellfish Fauna (Continued ) d Benthic organisms Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.73 Table 22.10 Continued Top Margin: Proposed Actions That may Cause Environmental Impact c Feed lots d Dairying e Energy generation f Mineral processing g Metallurigcal industry h Chemical industry i Textile industry j Automobile and aircraft k Oil refining l Food m Lumbering n Pulp and paper o Product storage E Land Alteration a Erosion and control and terracing b Mine sealing and waste control c Strip mining rehabilitation d Landscaping e Harbor dredging f Marsh fill and drainage F Resource Renewal a Reforestation b Wildlife stocking and management c Groundwater recharge d Fertilization application e Waste recycling G Changes in Traffic a Railway b Automobile c Trucking d Shipping e Aircraft f River and canal traffic g Pleasure boating h Trails i Cables and lifts j Communication k Pipeline H Waste Emplacement and Treatment a Ocean dumping b Landfill c Emplacement of tailing, spoil, and overburden d Underground storage e Junk disposal f Oil well flooding Left Margin: Existing Characteristics and Conditions of the Environment e Insects f Microfauna g Endangered species h Barriers i Corridors C Cultural Factors Land Use a Wilderness and open spaces b Wetlands c Forestry d Grazing e Agriculture f Residential g Commercial h Industrial i Mining and quarrying Recreation a Hunting b Fishing c Boating d Swimming e Camping and hiking f Picnicking g Resorts Aesthetics and Human Interest a Scenic views and vistas b Wilderness qualities c Open space qualities d Landscape design e Unique physical features f Parks and reserves g Monuments h Rare and unique species or ecosystems i Historical or archaeological sites and objects j Presence of misfits Cultural Status a Cultural patterns (lifestyle) b Health and safety c Employment d Population density Constructed Facilities and Activities a Structures b Transportation network (movement, access) c Utility networks d Waste disposal e Barriers (Table continued ) Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.74 n Section Twenty Two Table 22.10 Continued Top Margin: Proposed Actions That may Cause Environmental Impact Left Margin: Existing Characteristics and Conditions of the Environment H Waste Emplacement and Treatment Constructed Facilities and Activities (Continued ) (Continued ) g Deep well emplacement f Corridors h Cooling water discharge D Ecological Relationships Such As: i Municipal waste discharge including a Salinization of water resources spray irrigation b Eutrophication j Liquid effluent discharge c Disease-insect vectors k Stabilization and oxidation ponds d Food chains l Septic tanks, commercial and domestic e Salinization of surficial material m Stack and exhaust emission f Brush encroachment n Spent lubricants g Other I Chemical Treatment E Others a Fertilization b Chemical deicing, of highways, etc c Chemical stabilization of soil d Weed control e Insect control (pesticides) J Accidents a Explosions b Spills and leaks c Operational failure K Others It is very important that engineers present the multiphasic effects of the proposed project on air, water, and land characteristics, the biota, and on constructed structures, if any It is also important to relate, in the discussion of impact, environmental interests related to recreation, education, science, history, and culture as well as to overall community well-being Health and safety considerations, both within the project and in any exterior community relationship, must be discussed Specific guidance on format and content can be found in the Council on Environmental Quality guidelines, and more specifically, in each sponsoring federal agency guidelines, such as Department of Transportation, Federal Aviation Administration or the Army Corps of Engineers As required by the Environmental Protection Agency, the report must assess: The probable impact of the action The adverse environmental effect should the project be implemented The alternatives The relationship between the local short-term effect on environment, and maintenance of or increased benefit to the environment over the long term The commitments of resources that might be considered irreversible if the proposed action should take place (E T Chanlett, “Environmental Protection,” 2nd ed., R A Corbitt, “Standard Handbook of Environmental Engineering,” and J F Rau and D C Woolen, “Environmental Impact Analysis Handbook,” McGraw-Hill Publishing Company, New York (www.books.mcgraw-hill.com); J E Heer, Jr., and D J Hagerty, “Environmental Assessments and Statements,” and D C Rona, “Environmental Permits,” Van Nostrand Reinhold, New York; S J Rosen, “Manual for Environmental Impact Evaluation,” Prentice-Hall, Inc., Englewood Cliffs, N.J (www.prenhall.com).) Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website [...]... For depths of flow Storm-water inlet with opening in a curb Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.13 up to 0.4 ft capacity of inlet may be calculated from the weir... (www.asce.org); Metcalf & Eddy, Inc., “Wastewater Engineering, ” 3rd ed., McGraw- Catch basin with grating inlet in a gutter Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING 22.14 n Section Twenty Two Hill Publishing... For sewers under 60 in in diameter; (b) for larger sewers Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.15 considerable excavation If the drop is less than 2 ft, however,... weir along the side wall of the sewer (Fig 22.6a) Diversion, Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.17 Fig 22.6 Flow-regulating devices for sewers ft3/s, may be estimated... to a point in that riser pipe to the sewer force main HGL Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.19 HGL can be calculated as follows Start at the downstream end of... Similarly, pumping may be necessary to give sufficient head Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.21 Fig 22.8 Small automatic wastewater pumping station for wastewater... curve This procedure accounts for additional friction loss as Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.23 the force main pipe ages A pump curve is also a plot of head versus... through the voids, in other attached growth processes, the Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.25 BOD, CBOD, and COD n The amount of oxygen used during decomposition... surface freezes, effluents are poor, but the ice prevents odors Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.27 Wastewater treatment in oxidation ponds depends on aerobic decomposition... horizontal line representing oxygen content at saturation Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights reserved Any use is subject to the Terms of Use as given at the website ENVIRONMENTAL ENGINEERING Environmental Engineering n 22.29 ging dispersion, to prevent sludge buildup at the discharge In ... Reports on Engineering Practice, No 37 and 60, respectively, American Society of Civil Engineers (www.asce.org).) Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)... Eddy, Inc., “Wastewater Engineering, ” 3rd ed., McGraw- Catch basin with grating inlet in a gutter Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)... pollutants are controlled by EPA General Pretreatment Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies All rights