Environmental engineers handbook - Chapter 8 pdf

8.1 REMOVING SUSPENDED SOLID CONTAM- INANTS Algae Control Carbon Particles Gravity Settling Solids Disposal Foundry Sand Laundry Wastes The Problem of Commercial Waste Treatment Systems Quality of Effluent Mill Scale Design Parameters Operational History Mineral Tailings 8.2 REMOVING ORGANIC CONTAMINANTS Aldehydes Biological Oxidation Air Stripping Carbon Adsorption Cellulose Pulp Wastewater Volume Effluent Characteristics Methods of Treatment Research Problems Food Processing Wastes Water Reuse Water Conservation Elimination of Water Use Wastewater Treatment Hydrocarbons Design Basis Operational History Pesticides Pesticide Removal in Natural Aquatic Systems Biodegradable Replacement and Controlled Self-Destruction Biological Treatment Processes Chemical Flocculation and Oxidation Activated Carbon Adsorption Reverse Osmosis Incineration Research Trends Phenol Solvent Extraction Biological Treatment Carbon Adsorption Chemical Oxidation Starch Biological Treatment Textile Industry Wastes Viruses and Bacteria Chlorination Ozonation 8.3 REMOVING INORGANIC CONTAMINANTS Aluminum Bicarbonate Removing Bicarbonate Alkalinity Cadmium Sources of Cadmium-bearing Waste- waters Treatment Methods Calcium 8 Removing Specific Water Contaminants I.M. AbramsԽD.B. AulenbachԽE.C. BinghamԽL.J. BollykyԽT.F. Brown, Jr.ԽB. BruchԽR.D. BuchananԽL.W. CanterԽC.A. CaswellԽR.A. ConwayԽG.J. CritsԽE.W.J. DiaperԽJ.W.T. Ferretti ԽR.G. GantzԽW.C. GardinerԽL.C. Gilde, Jr.ԽE.G. KominekԽ D.H.F. LiuԽA.F. McClure, Jr.ԽF.L. ParkerԽR.S. RobertsonԽ D.M. RockԽC.J. SanthanamԽL.S. SavageԽS.E. SmithԽF.B. TaylorԽC.C. WaldenԽR.H. Zanitsch ©1999 CRC Press LLC Chromium Reduction and Precipitation Ion Exchange Cyanides Chlorination Ozonation Fluoride Hardness Ion Exchange Lime and Lime-Soda Ash Softening Iron Controlling Iron with Bacteria Removing Iron Salts Lead Treatment Methods Magnesium Manganese Mercury Properties Sources of Contamination Methylation of Inorganic Mercury Methods of Removal from Water Nickel Silica Insoluble Silica Soluble Silica Strontium Sulfate Ion Exchange Evaporation and Crystallization Reverse Osmosis Biological Reduction Sulfide Zinc Ion Exchange Precipitation 8.4 INORGANIC NEUTRALIZATION AND RECOVERY Boiler Blowdown Water Spent Caustics from Refineries Phenolic Sulfidic Steel Mill Pickle Liquor The Pickling Process Disposition of Spent Liquor 8.5 OIL POLLUTION Effects on Plant and Animal Life Toxicity Marine Organisms Plants and Oil Sources and Prevention Oily Materials Detection, Identification, and Surveys Prevention Methods of Control Characteristics and Composition Mechanical Containment Mechanical Recovery Application of Agents 8.6 PURIFICATION OF SALT WATER Conversion Processes Desalination Plants Desalting Processes Multieffect Evaporation Vapor Compression Evaporation Multiflash Evaporators Freezing Processes Vacuum-Freeze Vapor Com- pression Reverse Osmosis Electrodialysis The Future of Desalination 8.7 RADIOACTIVE LIQUID WASTE TREATMENT Low-Activity Wastes Precipitation Ion Exchange Evaporators Dilution and Release Hydrofracture Bituminization High-Activity Wastes Generation Storage in Tanks Conversion to Solids Storage ©1999 CRC Press LLC Algae Control The types of algae and the concentration in wastewater depend on residence time, climate and weather, amount of pollutants entering the pond, and dimensions of the pond. Normally, small unicellular types of algae develop first, e.g., Chlorella.Because of their physical dimensions they are difficult to remove by the processes listed in Table 8.1.1. Longer residence times lead to the development of larger algae and other plankton, which is more readily re- moved. The algae concentration affects the choice of re- moval process and the rate of treatment. Because of their light density, the dried weight of suspended solids is not an efficient measure of concentration. Algae are normally measured in volumetric or areal standard units (Anon. 1971). In surface water supplies, concentrations may be as high as 30,000 cells per milliliter (ml), this can be much higher in nutrient-rich waste treatment effluents. A com- bination of processes may be the best treatment, e.g., cop- per sulfate addition and microstraining, as used on surface water supplies in London, England. Carbon Particles Carbon particulate matter suspended in waste effluent must be either controlled or removed prior to discharge. Wastes associated with the carbon black and acetylene in- dustries are of concern. These wastes may contain up to 1000 milligrams per liter (mg/l) carbon particles in sus- pension; in most cases this carbon concentration must be reduced to less than 50 mg/l suspended solids. Usually, these solids settle readily and are removed by gravity set- tling and/or flotation. Individual particle sizes range from a submicron to larger than 100 micron ( ␮ ). Larger particles settle, whereas smaller particles float. Transition size particles remain sus- pended almost indefinitely unless forced out of suspension by mechanical or chemical means. Unless a highly clari- fied effluent is required, suspended matter may not have to be removed as it amounts to a small proportion of to- tal solids concentration. GRAVITY SETTLING Two types of gravity systems are available: (1) settling Lagoons, which provide retention time for solid particles to settle as sludge. These must be cleaned periodically; and (2) mechanical Clarifiers, which remove suspended solids and also rid bottom sludges mechanically. The settling lagoon requires a minimum capital invest- ment. Cleanout costs are high compared with the me- chanical clarifier operating costs. Settling devices are usually designed on the basis of over- flow rate, gal per day (gpd) per sq ft of surface area. According to the Ten State Standards (Great Lakes-Upper Mississippi River Board of State Sanitary Engineers 1968), this rate should be in the range of 600 to 1000 gpd/sq ft. In designing the carbon settling lagoon, frequency of la- goon cleaning must be considered, and the lagoon must be sized accordingly. Carbon sludge will settle to a den- sity of 5–20% solids. ©1999 CRC Press LLC 8.1 REMOVING SUSPENDED SOLID CONTAMINANTS TABLE 8.1.1ALGAE REMOVAL PROCESSES: MERITS AND FLAWS Algae Removal Process Advantages Limitations Copper sulfate Simple and inex- Creates toxicity; only some algal pensive forms attacked Chlorine Simple and inex- High doses needed; not all algae pensive attacked Coagulation and Positive removal of High chemical doses needed; dif- settling all types of algae ficult sludges produced Sand filters Positive removal of Rapid filter clogging may occur all types of algae Microstraining Simple and inex- Not all algal forms removed pensive Air flotation Positive removal of Not all algal forms removed; all types of algae sludges may be difficult to handle As an example, a 5-acre lagoon, 5 ft deep, with an in- fluent suspended solids concentration of 1000 mg/l and an effluent concentration of 50 mg/l at a flowrate of 10 mgd will retain almost 80,000 lb of solids per day. If the solids settle to a 5% sludge density, the lagoon will be filled with sludge in less than two months, as indicated by the calcu- lations in Table 8.1.2. A settling lagoon design for this ap- plication would probably be based on cleaning frequency rather than on overflow rates. The outfall structure of a settling system should retain floating material and maintain laminar flow to prevent solids from resuspending at discharge due to turbulence. An underflow-overflow weir (Figure 8.1.1) efficiently pro- vides such an outfall. According to the Ten State Standards (Great Lakes–Upper Mississippi 1968), weir loading rates should not exceed 10,000 gpd per linear ft of weir to as- sume minimum resuspension of settled matter from tur- bulent flow. For the example in Table 8.1.2, a weir 1000 ft long would be required. SOLIDS DISPOSAL Whether a mechanical clarifier, a settling lagoon or other means of solids removal is utilized, concentrated carbon slurry or sludge must be disposed of. Disposal methods in- clude incineration, landfill disposal, reuse, and dewatering. Removal and disposal of concentrated solids slurry is the most difficult part of the carbon clarification system. Eliminating waste at the source is ideal. Tightening pro- duction controls and modifying the process can drastically reduce waste losses and should be investigated before any removal system is developed. No treatment system is jus- tifiable without assurance that waste production is mini- mized at the source. Frequently, waste carbon is a prod- uct loss, and recovery is valuable. Keeping carbon out of wastewater prevents problems in waste treatment. Foundry Sand Foundry melting emissions contain solid particles ranging from coarse dust to fines of submicron size. Cupola emis- sions are much coarser than electric furnace emissions, which are generally less than 5 ␮ . Foundry melting dusts include combustibles containing 20–30% carbonaceous material. Iron oxides account for nearly 60% of collected dusts; silica and miscellaneous metallic oxides account for smaller quantities. ©1999 CRC Press LLC TABLE 8.1.2EXAMPLE: SETTLING LAGOON FILL TIME CALCULATION Settling Lagoon Data: Area ϭ5 acres Depth ϭ5 ft Flow ϭ10 million gal/day (mgd) Influent concentration ϭ1000 mg/l Effluent concentration ϭ50 mg/l Sludge density ϭ5% Carbon deposited per day: (1000 Ϫ50) ϫ10 ϫ8.34 ϭ80,000 lb/day Lagoon volume: V ϭ5 acre ϫ5 ft ϭ25 acre-ft ϭ8.3 ϫ10 6 gal Solids capacity of lagoon at 5% sludge density: 5% ϭ50,000 mg/l ϭ0.42 ᎏ g lb al ᎏ Capacity ϭ0.42 ᎏ g lb al ᎏ ϫ8.3 ϫ10 6 gal ϭ3.5 ϫ10 6 lb solids Time required to fill lagoon with sludge: T ϭ ᎏ 8 3 ϫ .5 1 ϫ 0 4 1 l 0 b 6 /d lb ay ᎏ ϭ44 days FIG. 8.1.1Settling lagoon outfall structure. Water curtains and scrubbers are used to remove solids from foundry stack gases. Wet scrubbers also remove acidic compounds. Scrubber water is treated to neutralize acids and to remove solids prior to recirculation. Settled solids are vacuum filtered prior to disposal. Most foundries have a number of scrubbers working on different opera- tions, and all effluents are combined and treated together. In grinding and shakeout areas, the scrubber may be ei- ther cyclonic or water curtain, which tolerates dirty feed- water. However, abrasive materials of ϩ200 mesh should be removed to avoid abrasion of circulating pumps. For complete solids removal—down to smoke particles from cupola emission gas—high-energy scrubbers such as Venturis are required, which need clean water. Cupola cooling water should also be clean to prevent heat ex- change surface fouling. If water is used for slag quench- ing, a mass of porous particles up to 1 /4 in is produced. These usually float. Casting washing produces a slurry with ϩ150 mesh sand. Most of these materials can be sep- arated on a vibrating screen of approximately 50 mesh. Depending on the recirculation system, grit separators, settling basins, or clarifiers are used. A hydroseparator re- moves fine sand down to approximately 50 ␮ . Removal of finer solids requires chemical treatment with lime, alum, and possibly a polyelectrolyte to produce clarified effluent containing 10–20 mg/l of suspended solids. Disc, drum, or belt filters are used for dewatering foundry waste solids. Filter rates range from 25–40 lb of dry solids/hr/sq ft. Some foundries have sand scrubber wastes. This differs from dust collection water as it settles more slowly. Overflow rates of no more than 0.3–0.5 gpm/sq ft can be used. Filtration rates for sand scrubber wastes vary from 3–10 lb of solids/hr/sq ft. Laundry Wastes THE PROBLEM OF COMMERCIAL WASTE Commercial coin-operated laundry installations pose problems when sewers are not available, and septic tank or leach field systems are utilized. Because of the small amount of land available for liquid waste discharge, ad- ditional treatment is necessary. Treated effluent reuse should also be considered. Table 8.1.3 indicates typical waste flow (Flynn and Andres 1963) from laundry installations on Long Island, N.Y. A typical installation of 20 machines produces 4,000 gpd. Depending on soil conditions, this volume might re- quire a much larger disposal area than is available. Table 8.1.4 describes typical laundry waste properties and com- position as resembling weak sewage with the exception of high alkyl benzyl sulfonate (ABS) and phosphate contents. Large quantities of water are required for washing, therefore alleviating both water supply and waste disposal problems via partial or complete recycling of treated waste- water effluents should be considered. TREATMENT SYSTEMS Septic Tanks Septic tanks followed by leach field systems are often in- adequate to process the quantity and quality of water to be disposed. Physical Methods All laundry waste should be strained in a removable bas- ket so that lint does not clog pumps and other equipment in the treatment system. Plan settling of laundry waste removes the heavier grit particles washed out of clothes. Most biological oxygen demand (BOD) is soluble, therefore settling has little ef- fect on the BOD and chemical oxygen demand (COD) of the waste. Several types of filtration units are used to treat laun- dromat wastes. A sand filter efficiently removes particu- late matter. Pressures and filters usually require less space than gravity sand filters. The latter is used following other treatment methods and is little different from filtration through soil. Filtration through diatomaceous earth filter cake is highly recommended, since it removes bacteria and some viruses, and is particularly effective in separating chemical sludges. In diatomaceous earth filtration, prior settling or sand filtration lengthens filter runs but will not result in a better quality effluent. ©1999 CRC Press LLC TABLE 8.1.3TYPICAL WASTE FLOW FROM A COIN- OPERATED WASHING MACHINE Average wastewater flow 89–240 gal/day Maximum average flow 587 gal/day Minimum design basis for treatment based on a 12–hr day 550 gal/machine TABLE 8.1.4TYPICAL QUALITY OF LAUNDRY WASTES Concentration, mg, per liter Parameter Average Range pH 7.13 5.0–7.6 BOD 120 50–185 COD 315 136–455 ABS (methylene blue active 33 15–144 substance) Total Dissolved Solids 700 390–1450 Phosphate (PO 4 3Ϫ ) 146 84–199 Acidity as CaCO 3 91 73–124 Alkalinity as CaCO 3 368 340–420 Chemical Methods Coagulation or precipitation followed by settling and/or filtration has proven effective in treating laundromat wastes. Alum alone at a pH of 4–5 may result in a 75% reduction in ABS and an 85% reduction in phosphate con- tent of the waste. Iron salts effect a similar reduction, whereas calcium chloride can reduce ABS by 85%, but this results in only a 50% reduction in phosphate content at high doses. In addition, ABS may be completely neutralized, us- ing a cationic detergent. Tests must be performed to pro- vide exact equalization with no excess of either deter- gent. Substances to perform this are commercially available. Phosphates are effectively removed by precip- itation techniques. Alum, iron salts, and calcium salts at high pH offer a high degree of phosphate removal. Better than 90% phosphate removal can be obtained by cal- cium chloride combined with adjusting the pH to 10, or by lime, both followed by filtration in a diatomaceous earth filter. Physicochemical Methods Considered a physicochemical process, ion exchangehas not been successful in producing high quality water for reuse from laundry waste. Residual organic matter may be effectively removed by contact with activated carbon.Granular carbon in an up- flow pressure tank seems to be most efficient, although adding powdered activated carbon to other chemicals prior to filtration can also be effective. Activated carbon is also effective in removing anionic detergents. However, high ABS concentration exhausts the capacity of activated car- bon to remove other organic matter, therefore prior treat- ment to reduce ABS should be applied. Biological Methods When soluble organic material is present, it is difficult to reduce BOD by more than 60% through chemical pre- cipitation and filtration. To achieve high degrees of BOD removal, biological treatment may be required. Although there is an adequate bacteria food supply of carbon and phosphorus in the waste, total nitrogen content may be deficient for biological treatment. Solids Disposal Chemical precipitation solids and diatomaceous earth solids are amenable to landfill disposal. Biological sludges are treated similarly to septic tank sludges. The sludge holding tank should be conveniently located for periodic pumping by a local scavenging firm. Suggested Treatment System A schematic flow diagram for a suggested laundromat waste treatment system is shown in Figure 8.1.2. After screening lint, waste is stored in a holding tank to equal- ize flow and provide sufficient volume for operating the treatment system during normal daytime hours. A pump can deliver waste to the chemical mixing tank where the appropriate chemicals are added. A settling tank removes the bulk of precipitated solids prior to diatomaceous earth filtration. A pump is required to provide pressure for fil- tration in the diatomaceous earth filter. Recycling to the chemical mixing tank would be required during the filter precoat operation. Following filtration, activated carbon adsorption may be practiced as needed. A final storage tank is provided for adding chlorine if needed or for holding effluent for future use. Settling tank sludges and diatomaceous earth filter discharges should be collected in a sludge holding ©1999 CRC Press LLC FIG. 8.1.2Laundry waste treatment tank and pumped out periodically by a scavenger system. This system should provide effluent satisfactory for dis- charge or partial reuse. QUALITY OF EFFLUENT Chemically precipitated and filtered wastes can be disposed in a subsurface system, provided that there is adequate land to accommodate the hydraulic load. Biological treat- ment may be necessary to improve water quality before discharge into a small stream. Water reuse should be considered because of the large volume. Since chemical coagulants increase total dissolved solids in water, complete reuse and recycle would contin- uously increase total dissolved solids. Thus, chemicals should be limited to prevent excess. Because the water is still warm, heat energy can be saved by recycling treated effluent. To control total solids buildup, an ion exchange system is theoretically applicable. However, experience shows that this system is not effective in treating laundry waste effluents. Other uses for the treated water may be found, depending on the water requirements of nearby in- dustries. Recharging water into the soil uses the soil’s nat- ural treatment ability and maintains a high water level in the aquifer, providing water for the laundromat. Mill Scale This is a case history of the design, construction, and op- eration of a wastewater treatment system established to remove mill scale from water contaminated by steel mill scale removal operation and to provide a closed system enabling reuse of water for the mill scale removal opera- tion. The installed cost of the total system was approxi- mately $600,000, including two parallel treatment sys- tems assuring continuous 24-hr operation via available al- ternate flow patterns for necessary equipment repair or maintenance. DESIGN PARAMETERS To define the problem, existing system elements were re- viewed (Figure 8.1.3). The original design specified a once- through system capable of processing an existing flow of 3500 gpm with the capability to handle 7000 gpm in the future. Effluent quality was to meet stringent state re- quirements for discharge to the waterway. Applying knowledge of stream quality to the original design re- quirements raised question about the once-through con- cept. It was noted that if process utilization of this water did not require a higher quality supply than the polluted raw river water presently used, the need for a once-through system was questionable. A system to treat this wastewater to meet stage dis- charge standards would be very expensive. However, it cost much less to treat this wastewater only to the extent required by the process. Historically, this requirement was met by the quality of a badly polluted stream. The cost difference between a reuse system and a once-through dis- charge system is substantial. Water quality design stan- dards were key factors in system cost. Table 8.1.5 lists the design parameters. Provisions were also made for sludge and recovered oil handling with min- imal expense and minimal personnel time required. The original process flowsheet is shown in Figure 8.1.4. A closed system of this type is susceptible to three primary problems: algal accumulation, dissolved solids buildup, and heat buildup. Solving these problems requires bactericide and/or al- gicide additives, blowdown and addition of makeup wa- ter, and a system cooling tower. The original design in- cluded a cooling tower hookup, if required, together with a chemical feed system. However, makeup water from the ©1999 CRC Press LLC FIG. 8.1.3Original water supply layout. A. Original plant wa- ter supply line. (Raw river water was used without pretreatment for mill scale removal process.) TABLE 8.1.5DESIGN PARAMETERS FOR MILL SCALE WATER TREATMENT PLANT a Wastewater Flow 3500 gpm existing 7000 gpm design capability Primary Pollutants Iron solids (fines) Oil Heat Treated Effluent Quality Continuous 24-hr reuse Required capability Acceptable Pollutant Content Iron (suspended solids) in Effluent 600 ppm Oil 150 ppm (plus freefloating oil) a System to be as fully automatic as possible. river was thought sufficient to compensate for evaporative losses and to control dissolved solids buildup. Dissolved solids presented no serious problem. OPERATIONAL HISTORY In operation, the system is entirely satisfactory. The cool- ing tower was not installed originally because heat loss through the system—due to the length of the lines and the surface area of the tanks—was considered sufficient. During most of the operating time, this was true. However, during summer when ambient surface air temperatures oc- casionally reach 110° to 115°F in this region, Joliet, Ill., heat loss was not enough to maintain comfort for per- sonnel manning the spray nozzles in the plant. During such periods, return water temperature rose to 114°F for a few days. Therefore, a cooling tower was installed. The sludge averages 50 to 60% solids, about the min- imum water content for the sludge to slide easily from the discharge chutes into catch buckets. Oil-skimming devices are rotary cylinder units mounted at the water surface level in the tanks. These units require heat protection to prevent freezing in the winter. The sludge is recovered; since it consists primarily of mill scale, it can be sold as blast furnace charging material. Strainers are 0.005 in units with 5,000 gpm capacity each. These are in the system for insurance in the event of heavy overloading of the settling tanks. This might occur if one of the two parallel systems was shut down for pump or ejection mechanism repairs when the mill is operating at peak capacity. Until now, the system has performed well, except for minor startup and training problems. Mill operating per- sonnel are pleased, because return water quality is far bet- ter than the raw river water they were using. Mineral Tailings Wastewater from mining or ore beneficiation contains sus- pended particles of fine sand, silt, clay, and possible lime- stone. A large percentage of solids may be colloidal due to their nature or as a result of milling and flotation pro- ©1999 CRC Press LLC FIG. 8.1.4 Reuse system on steel plant water. (P ϭ pump; F ϭ filter) TABLE 8.1.6 SETTLING VELOCITY OF SILT AND SAND PARTICLES IN TERMS OF APPLICABLE OVERFLOW RATES Particle Comparable Overflow Diameter (mm) Rate cpm/sq ft 1.0 148.0 0.4 62.0 0.2 31.0 0.1 11.8 0.06 5.6 0.04 3.1 0.02 0.91 0.01 0.227 0.004 0.036 FIG. 8.1.5 Thickener for mineral tailings cessing with reagents added to disperse the solids. Table 8.1.6 shows the velocities at which particles of sand and silt subside in still water (American Water Works Asso- ciation 1969) at 50°F. Collodial particles cannot be removed by settling with- out chemical treatment. Because of the chemicals added in milling and during flotation, it is virtually impossible to economically clarify mineral tailings, and mineral tail- ing overflows from thickener clarifiers are usually re- tained indefinitely. Figure 8.1.5 illustrates thickener de- sign used in alumina, steel, coal, copper, and potash processing. —E.W.J. Diaper, T.F. Brown, Jr., E.G. Kominek, D.B. Aulenbach, C.A. Caswell References American Water Works Association, Inc. 1969. Water treatment plant design.New York, N.Y. Anon. 1971. Standard Methods for the Examination of Water and Wastewater.13th ed. Aulenbach, D.B., P.C. Town, and M. Chilson. 1970. Treatment of laun- dromat wastes, Part I.Proceedings, 25th Industrial Waste Conference. Purdue University, Lafayette, Ind. (May 5–7). Aulenbach, D.B., M. Chilson, and P.C. Town. 1971. Treatment of Laundromat Wastes, Part II.Proceedings, 26th Industrial Waste Conference. Purdue University, Lafayette, Inc. (May 4–6). Burns and Roe, Inc. 1971. Process design manual for suspensed solids removal.Environmental Protection Agency Technology Transfer. Flynn, J.M. and B. Andres. 1963. Launderette waste treatment processes. J.W.P.C.F.,35:783. Great Lakes–Upper Mississippi River Board of State Sanitary Engineers. 1968. Recommended standards for sewage works. ©1999 CRC Press LLC 8.2 REMOVING ORGANIC CONTAMINANTS Aldehydes Aldehydes have several properties important to water pol- lution control. Saturated aldehydes are readily biodegraded and represent a rapid oxygen demand on the ecosystem, whereas unsaturated aldehydes can inhibit biological treat- ment systems at low concentrations. Aldehyde volatility makes losses through air stripping an important consider- ation. BIOLOGICAL OXIDATION Aldehyde amenability to biodegradation is indicated by high biochemical oxygen demand (BOD) levels reported by several investigators. At a low test concentration, formaldehyde, acetaldehyde, butyraldehyde, crotonalde- hyde, furfural, and benzaldehyde all exhibited substantial biooxidation (Heukelekian and Rand 1955; Lamb and Jenkins 1952). An olefinic linkage in the ␣ , ␤ position usu- ally renders the material inhibitory (Stack 1957). The lev- els inhibitory to unacclimated microorganisms for acrolein, methacrolein and crotonaldehyde were 1.5, 3.5, and 14 mg. per liter (mg/l), respectively, whereas levels for ac- etaldehyde, propionaldehyde and butyraldehyde were 500 mg/l or above. Formaldehyde was inhibitory at 85 mg/l. Bacteria can develop adaptive enzymes to allow bio- logical oxidation of many potentially inhibitory aldehydes to proceed at high influent levels. Stabilization by accli- mated organisms of several organic compounds typical of petrochemical wastes has been investigated (Hatfield 1957). For organisms acclimated to 500 mg/l formalde- hyde, approximately 3 hr aeration time was required to bring the effluent concentration to zero. However, efflu- ent organic concentration after this interval was still high, indicating oxidation to formic acid or Cannizzaro dismu- tation to methanol and formic acid. Eight to ten hr of aer- ation were required for the effluent BOD to approach zero. Removals of acetaldehyde (measured as BOD) were from an initial concentration of 430 to 35 mg/l after a 5 hr aer- ation time. Propionaldehyde removals were from 410–25 mg/l after five hr. The oxidation pattern of paraformalde- hyde, the polymer of formaldehyde, resembled its precur- sor. Data collected through Warburg respirometer studies using seed sludges from three waste treatment plants (Gerhold and Malaney 1966) showed that aldehydes were oxidized to an extent second only to corresponding pri- mary alcohols. Only formaldehyde exhibited toxicity to all three sludges. Branching in the carbon chain increased re- sistance to biooxidation. AIR STRIPPING Kinetic data for air stripping of propionaldehyde, bu- tyraldehyde, and valeraldehyde have been presented (Gaudy, Engelbrecht and Turner 1961). Removal of pro- pionaldehyde in model units at 25°C followed first-order reaction kinetics; removals calculated from residual alde- hyde and residual chemical oxygen demand (COD) analy- ses were parallel, indicating that no oxidation of the acid occurred. However, at 40°C stripping was not described by first-order kinetics, and propionaldehyde oxidation to less volatile propionic acid was apparent when removals measured as COD were less than those measured as alde- hyde. Stripping of butyraldehyde and valeraldehyde at 25°C did not follow first-order kinetics, indicating oxidation of aldehyde to acid may also be occurring. Removals after an 8 hr aeration time at 25°C and an air flow of 900 ml/min/l, were 85% for propionaldehyde and butyralde- hyde, and 98% for valeraldehyde. In a biological system all three removal mechanisms would exist: biological ox- idation and synthesis, air stripping, and air oxidation. The magnitude of each means would depend primarily on the activity of the bacterial culture and the degree of gas-liq- uid contact. CARBON ADSORPTION Aldehydes, due to their low molecular weight and hy- drophilic nature, are not readily adsorbed onto activated carbon. Typical data from Freudlich isotherm tests of ad- sorbability at various carbon dosage levels are presented in Table 8.2.1. On a relative basis, aldehydes were less amenable to adsorption than comparable undissociated or- ganic acids but were more amenable than alcohols (Giusti 1971). However, none of the low molecular weight, po- lar, highly volatile materials were readily adsorbed. Cellulose Pulp All pulp mill effluents contain wood extractives, a highly diverse, ill-defined chemical group that varies widely ac- cording to wood species and origin. Chemical pulping wastes also contain hydrolyzed hemicelluloses and lignin, solubilized during cooking. Since various pulp processes vary considerably in mill design and operation, effluents are extremely diverse. WASTEWATER VOLUME Problems arise due to the tremendous volumes discharged (Table 8.2.2). Newer installations recycle process waters. Much market pulp is bleached, with bleach plant dis- charges as large as those from pulping. Since mills with 500–1000 ton/day capacity are not uncommon, volumes discharged at a single point may be abnormally high. EFFLUENT CHARACTERISTICS Pulp effluents usually have an abnormal pH, a variable loading of suspended fibrous solids, and an appreciable oxygen demand (Table 8.2.2). Older mills may have even heavier loadings. Kraft pulping produces alkaline wastes, ©1999 CRC Press LLC TABLE 8.2.1CARBON ADSORPTION OF ALDEHYDES Aldehyde Removal from 1000 mg/l Solution at 5 gm/l Carbon Dose Equilibrium Loading mg/g Removal Carbon Level, % Formaldehyde 19 9 Acetaldehyde 22 12 Propionaldehyde 57 28 Butyraldehyde 106 53 Acrolein 61 31 Crotonaldehyde 92 46 Benzaldehyde 188 94 Paraldehyde 148 74 TABLE 8.2.2EFFLUENT CHARACTERISTICS OF CELLULOSE PULPING WASTES a Water Volume BOD 5 a Suspended Solids Unit Process U.S. gal/ton pH lb/ton lb/ton Hydraulic debarking 500–10,000 4.6–8.0 5–20 30–50 Groundwood 6,500–10,000 6.0–6.5 10–40 15–80 Neutral sulfite semichemical pulping (with recovery) 3,000–20,000 6.5–8.5 30–60 Ͻ10 Kraft pulping 6,000–20,000 7.5–10.0 10–50 Ͻ20 Sulfite pulping (no recovery) 20,000–30,000 2.5–3.5 550–750 150–200 Sulfite pulping (with recovery) 20,000–30,000 2.5–4.0 50–100 40–60 Bleaching 20,000–40,000 2.0–5.0 10–25 14–25 a Oxygen consumed at 20°C during a 5-day incubation with acclimated microorganisms. [...]... from 0.05 to FIG 8. 2.14 Low-speed surface aerator installation ©1999 CRC Press LLC ΃ TABLE 8. 2 .8 COMPOSITION OF WASTES FROM A SYNTHETIC FIBER FINISH MILL BOD avg ppm BOD % OWFb avga pH range Total solids range, ppm 8. 2–9.0 6 .8 6.9 — 1.012–5.572 3. 388 –7.256 — 2 ,83 2 58 960 Scour and dye Scour and bleach 8. 3 8. 5 8. 9–9.6 1.534–2.022 766–946 First rinse Second rinse 7.0–9.1 6 .8 7.3 1 08 188 80 88 2,000 750 (Estimated)... 9.3–12.6 8. 2–10.7 6.5 8. 2 7 .8 9.0 7.3–7.6 — 1.492–2.2 78 150–954 106–932 , 3 18 1,016 106–134 — 1,360 90 25 3 68 11 450 3.4 0.2 0.1 0.9 0.0 1.1 9.5–10.0 6.4 8. 7 2.2–6.5 4.1–6.5 1.3–1.7 5.9–7.7 6.3–7.4 3.7–4.3 1.350–2.470 102–294 , 170–1.950 116–300 , 130–3.002 , 612–1 .82 4 82 –152 , 89 6–2.3 18 2,190 109 175 42 995 688 50 2,110 6.6 0.4 0.5 0.1 3.0 2.0 0.2 6.3 Rayon processing Scour and dye Salt take-off Waterproof... reactivated by chlorination or by permanganate Aeration reduces chlorine requirement A-L-ST-SF 8. 5–9.6 Yes pH control required A-Co-L-ST-SF 8. 5–9.6 Yes Laboratory control required Cation exchange 6.5 No Periodic regeneration with salt solution L-ST-SF No Iron is precipitated as ferrous carbonate in the absence of oxygen 8. 0 8. 5 a A ϭ aeration; ST ϭ settling; SF ϭ sand filtration; Acat ϭ catalytic aeration;... Trickling filtration Lagoons Suspended Solids BOD Grease Color Alkalinity 20–30 20–30 95 0–10 30–50 30–50 40–50 24–45 95 0 80 –90 95– 98 0 0 0 0 10–50 10–20 0 0 0 0 10–20 10–20 0–50 40–50 40–70 60 15–25 20–56 20 21 83 32–65 59 84 50 80 85 –90 80 85 0 85 — 97 — — — — — 75 — — — 80 –95 80 –95 80 –95 0–15 0–10 0–10 10–30 10–30 10–30 10–30 10–30 10–20 90–95 90–95 30–70 20 50–65 50–65 Reprinted, from FWPCA 1967 The... turbid surface water containing organic matter Iron and manganese in oxygen-free well water containing about 1.5 to 2.0 ppm iron and manganese Iron in soft well water; iron is present as ferrous bicarbonate Processa Operating pH Oxidation Remarks A-ST-SF Acat-ST-SF A-Fcat 6.5 6.5 6.5 Yes Yes Yes Fcat 6.5 Yes A-Cl-ST-SF 7.0 8. 0 Yes Easy to operate Easy to operate; requires double pumping Easy to control;... form The reactions are as follows: R*H R*H \ \ SO4 ϩ Na2Cr2O7 WV Cr2O7ϩ Na2SO4 “ “ R*H R*H 8. 3(10) R*H \ Cr2O7 ϩ NaOH WV (Na2Cr2O4 W V “ R*H Na2CrO4) ϩ 2 R°H Ϫ OH 8. 3(11) R*H 2 R*H—OH ϩ H2SO4 WV Reducing Agent: Cr6ϩ ϩ Fe2ϩ ϩ Hϩ ® Cr3ϩ ϩ Fe3ϩ SO2 or Na2S2O5 Cr3ϩ ϩ OHϪ ® Cr(OH)3 2Ϫ SO4 8. 3 (8) 8. 3(9) Reaction 8. 3 (8) proceeds almost instantaneously at a pH of 2.0 or less Each reducing agent shown in the... showed fairly rapid removals TABLE 8. 2.6 REMOVAL OF PESTICIDES IN WATER TREATMENT PLANT OPERATIONS ACTIVATED CARBON ADSORPTION CHEMICAL FLOCCULATION AND OXIDATION Removal, percent Pesticide (10 ppb dosage) CoagulationFiltration Lindane Endrin Dieldrin 2,4,5-T Ester Parathion DDT Ͻ10 35 55 65 80 98 ©1999 CRC Press LLC Carbon Slurry 5 ppm 20 ppm 30 80 75 80 Ͼ99 Not Tested 80 94 92 95 Ͼ99 Not Tested Considerable... hydrolysis of the ester linkages Hydrolysis can be either acid-catalyzed, e.g., ciodrin, or base-catalyzed, e.g., malathion Microbial degradation can be by hydrolysis or oxidation Partial degradation is often the case, although for diazinon, chemical hydrolysis of the thiophosphate linkage attached to the heterocyclic ring results in 2-isopropyl-4-methyl-6-hydroxypyrimidine, which is degraded rapidly by soil... arranged in a sloping soilair-water interface (Metcalf, Sangha and Kapoor 1971) A food chain of plant and animal organisms, compatible with the environmental conditions simulated in the aquarium, is chosen for following radiolabeled DDT (labeled in the aryl rings with C14) and methoxychlor Average data presented in Table 8. 2.5 show a 13,000-fold increase in con- TABLE 8. 2.4 PESTICIDE REMOVAL ORIENTATION... reuse as a chromate-rich solution This solution can be re©1999 CRC Press LLC SO4ϩ 2H2O “ R*H 8. 3(12) where: R° ϭ R3N, a weakly basic macroporous resin A typical flow diagram using the Higgins-type, continuous, countercurrent ion exchange system is shown in Figure 8. 3.1 Cyanides The major portion of cyanide-containing wastewater comes from metal finishing and metal plating plants Photo-processing plants . attached to the heterocyclic ring results in 2-iso- propyl-4-methyl-6-hydroxypyrimidine, which is degraded rapidly by soil microorganisms. Among the orthophos- phates, parathion is one of the most resistant. methoxychlor. Average data pre- sented in Table 8. 2.5 show a 13,000-fold increase in con- ©1999 CRC Press LLC FIG. 8. 2.9Polishing pond performance from startup. A ϭini- tial BOD of 2420 ppm (at. Slurry (10 ppb dosage) Filtration 5 ppm 20 ppm Lindane Ͻ10 30 80 Endrin 35 80 94 Dieldrin 55 75 92 2,4,5-T Ester 65 80 95 Parathion 80 Ͼ99 Ͼ99 DDT 98 Not Not Tested Tested