Environmental Pollution Control Microbiology - Chapter 13 ppt

Chapter 13 SOLID WASTES Solid wastes are one of the more interesting environmental contaminants to deal with. The primary characteristic of importance for solid wastes lies in the fact that they are solid. Unlike gaseous wastes that flow into the vast atmosphere around us or liquid wastes that flow downhill until they ultimately reach the ocean, solid wastes tend to stay put until a major effort is made to move them to another spot. Solid wastes tend to remain as such until someone finds a use for the solid wastes and converts them into something of value. Suddenly, the solid wastes disappear until the new product loses its value and becomes solid wastes once again. The lack of value of solid wastes has resulted in limited information on their interaction with various microorganisms. Few people bothered to study solid wastes until the Federal government provided the funds for studies. It is not surprising that most of our understanding of solid wastes has come in the last 40 years. SOLID WASTE CHARACTERISTICS One of the frustrating problems confronting environmental scientists and environmental engineers lies in trying to determine the characteristics of solid wastes. Solid wastes are simply solid materials that have lost value for their Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. owner and are discarded. It does not mean that the solid wastes being discarded have no value. It simply means that the solid wastes have no value for the current owner. It may well have value for another owner. If the solid wastes have value for a new owner, these materials are no longer solid wastes, but rather raw materials for further use with renewed value until the new owner decides to discard them as solid wastes. All material goods that society makes and uses will become solid wastes in time. Solid wastes cannot be characterized by their chemical composition or their size or their weight alone. Solid wastes are characterized by many parameters. Chemical composition is an important parameter, along with size and weight. Bio-stability is also an important parameter for solid wastes that has largely been ignored. Bio-stability is the parameter that defines how the solid waste materials react to microorganisms and the rate of that reaction. Most solid wastes currently being produced are largely bio-stable, showing little to no reaction with microorganisms. Food wastes are the least bio-stable solid wastes, undergoing rapid reaction with microorganisms. Grass clippings and leaves are seasonal solid wastes that are not very bio-stable. From a practical point of view environmental microbiologists are only interested in the solid wastes having the least bio-stability. There are many ways to characterize solid wastes. No one classification is perfect. Classifications tend to start with the major sources of solid wastes. 1. Residential SW - all solid wastes produced by people living in residences within the classification area. Residences include single-family houses, duplexes, and apartments with multiple family units. 2. Commercial SW - all solid wastes produced by commercial establishments within the classification area. 3. Industrial SW - all non-hazardous solid wastes produced by industrial manufacturing plants within the classification area. 4. Construction and Demolition SW — all solid wastes generated during the normal construction of houses, apartments, commercial establishments, and industrial factories or from the destruction of houses, apartments, commercial establishments, or industrial factories. 5. Street Sweepings SW - all solid wastes collected by street sweepers operating in urban communities. 6. Water & Wastewater Treatment Plant Sludge SW - all sludge solid wastes produced by water and wastewater treatment plants within the classification area. 7. Automotive SW - all solid wastes generated when automobiles Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. and trucks are junked. 8. Bulky SW - all large solid waste items from residences and commercial establishments that require special collection and handling. Bulky solid wastes include washing machines, refrigerators, stoves, sofas, etc. 9. Trees - large trees that die or trees that are cleared for construction projects require special handling. 10. Agricultural SW - all solid wastes produced from farming operations. 11. Mining SW — all residues remaining from mining and mineral processing. These broad classifications of solid wastes have value for looking at the total solid waste problem at the national level. Regional classifications normally look at municipal SW, rural SW, agricultural SW, and mining SW. Prior to 1965 data on solid waste characteristics were quite limited. Few people were concerned enough about solid wastes to determine their characteristics. The major problem was simply that it was too difficult to take representative samples of solid wastes and make complete analyses. Although every person was concerned with the generation and disposal of solid wastes, no one cared enough to characterize those solid wastes. No one knew what to do with the limited data that appeared in the literature. When Congress passed the first solid waste legislation at the federal level, it became immediately apparent that no one had any real data on the magnitude of the solid waste problem. All available data was largely extrapolation of a limited database that dealt with the weight and volume of solid wastes generated by municipalities. Much of the early efforts of the new federal Office of Solid Wastes dealt with gathering more reliable data. Contracts were given to various engineering firms and research organizations to determine data on solid waste characteristics across the country. The data generated from these studies is the basis for most of the solid waste characterization. MUNICIPAL SOLID WASTES Municipal solid wastes include the residential SW, the commercial SW, and limited industrial S W generated within the jurisdiction of the municipality. The latest EPA published data on municipal solid wastes indicated that the United States produced 232 million tons in 2002. The per capita SW generation averaged 4.5 Ibs/d. The composition of municipal solid wastes in the United States and the percentage of each group by weight are given in Table 13-1. Examination of the different groups of municipal solid wastes indicates that glass and plastics are the most biostable with metals being relatively biostable. Paper, wood, rubber, leather and textiles are slowly biodegradable under specific conditions. Food wastes and yard wastes are biodegradable. One of the key Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. Table 13-1 COMPOSITION OF MUNICIPAL SOLID WASTES IN 2000 Paper Yard Waste Plastics Food Wastes Metals Rubber, Leather, & Textiles Glass Wood Other 37.4% 12.0% 10.7% 11.2% 7.8% 6.7% 5.5% 5.5% 3.2% parameters for biodegradability is moisture content. Food wastes contain up to 80% moisture, averaging about 70% moisture. Yard wastes average about 60% moisture with grass clippings having the most moisture and dead branches having the least moisture. Paper and cardboard normally contain less than 10% moisture. Wood can contain up to 40% moisture. Rubber, leather, and textiles usually contain less than 10% moisture. These materials are not biodegradable without the addition of water to increase their moisture level. Dry metal objects are bio-stable except in the presence of water. Microorganisms can slowly react with wet metal products, if the end products of the microbial-metal reactions are not toxic to the microorganisms. Glass and plastics have very low moisture content and are bio-stable even when immersed in water. For the most part municipal solid wastes reflect the lifestyle of the people within the municipal jurisdiction and the changes in the local economy. INDUSTRIAL SOLID WASTES Industrial solid wastes consist of hazardous solid wastes and non-hazardous solid wastes. The hazardous solid wastes are dangerous for the environment and are controlled by separate federal legislation than the non-hazardous solid wastes. The characteristics of industrial solid wastes are highly variable, depending upon the specific industrial processes and the workers within specific plants. Industrial solid wastes range from inorganic materials to organic materials. The EPA's estimate of non-hazardous industrial solid wastes in 1996 was 7.6 billion tons/yr. CONSTRUCTION AND DEMOLITION SOLID WASTES The construction of new houses and new commercial buildings results in the production of construction solid wastes in direct proportion to the materials Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. employed in the construction project. The characteristics of the construction solid wastes will vary with each project. Normally, construction wastes will include the residual materials that could not be incorporated into the finished building. The construction of houses will include pieces of wood, wallboard fragments, partial shingles, and excess roofing paper. If the house has a cinder block foundation and/or a brick front, broken cinder blocks and broken bricks will also be included. The amounts of construction wastes produced are directly proportional to the number of houses and buildings constructed. As a net result, the construction waste quantities and characteristics are highly variable and not easily estimated. Eventually, every house and every building will become solid wastes when their value is too low and the maintenance costs are too high. Under good economic conditions, old buildings are bulldozed to allow new replacement structures on the same site. Demolition of old structures results in complete destruction of the old structures. Demolition debris will consist of all the materials remaining in the structure. These materials are simply bulldozed and placed in a truck for removal from the site. The entire weight of all the materials in the old structure comprises the demolition wastes. Major urban renewal projects create large amounts of demolition wastes over a specific time period. The amount and characteristics of demolition wastes require separate evaluation of every project and cannot be generalized. STREET SWEEPINGS Many cities in the United States use street sweepers to collect dirt and trash that accumulates on streets in the major commercial and industrial areas. Occasionally, the residential streets will also be swept. The shape of road surfaces allows the dirt and trash to accumulate next to the curb and the road. For this reason street sweepers normally clean the area of the street next to the curb. The quantity of street sweepings collected is a function of the size of the city and the rainfall characteristics. Large cities produce more street sweepings than small cities. Large cities tend to attract dirty industries that can operate with a minimum of complaints. Cities tend to keep the dirty industries together, making it easier to keep the streets reasonably clean. Industrial areas tend to have large impervious surface areas, allowing maximum runoff during and after every rain event. The rapid runoff of rainwater carries the contamination on the streets into storm sewers for collection and removal. Areas with heavy rains will find that the streets are cleaned of all but the heaviest solid materials. Areas with light rains, occurring frequently, will find only the lightweight materials removed by the runoff water. Examination of street sweepings indicates they are composed of dirt, sand, grit, Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. paper products of various types, plastic materials, broken glass, rubber particles, and miscellaneous materials too difficult to identify and measure. Most of the street sweepings are relatively inert material that can be used as fill or placed into a sanitary landfill. One of the problems with street sweepers is their tendency to suspend fine particles around the street sweeper rather than capturing the fine particles. There are no uniform analyses for street sweepings. Every community must determine its own characteristics of street sweeping wastes, both as to quantities produced and their chemical characteristics. WATER AND WASTEWATER SLUDGES Every community that has a water treatment plant and/or a wastewater treatment plant will have water treatment sludge and/or wastewater treatment sludge. Emphasis on water treatment plants and wastewater treatment plants is on the removal of pollutants from the water being treated. The treatment processes produce a clean water and waste sludge. The water treatment plants generate alum sludge and calcium carbonate sludge, if the treatment plant softens the water. The clean water, produced in the water treatment plant, is distributed to every user in the community through a complex pipe network. Once the clean water has been used, it is returned as wastewater. The wastewater collection system is also a network of complex pipes that services every house and building in the community. The wastewaters are collected and discharged into a wastewater treatment plant. The pollutants in wastewater are classified as suspended pollutants and soluble pollutants. The majority of the suspended pollutants are removed by gravity sedimentation. The remaining suspended pollutants and the soluble pollutants are treated biologically with the pollutants converted into suspended solids that form settleable floe particles that are removed by gravity sedimentation. The two types of wastewater sludge are normally mixed together and treated in an anaerobic digester. The anaerobic digester destroys the readily biodegradable suspended solids, leaving a relatively inert residue for disposal on land. The characteristics of water treatment plant sludge are quite similar from plant to plant as far as chemical characteristics are concerned. The quantity of sludge produced varies with the magnitude of treatment required to remove the contaminants. Alum treatment of surface water produces an aluminum hydroxide floe that removes the suspended solids in the surface water. River water will contain both organic and inorganic particles. During periods of heavy rainfall and runoff in rural areas the river water will contain soil particles and any materials washed from the soil surface. The net result is for wide variations in alum use and in sludge production. Lake water contains colloidal suspended solids and various microorganisms. Understanding the source of the water being treated is essential to knowing the type and magnitudes of contaminants in the Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. water plant sludge. Water plants that soften the water will produce calcium carbonate sludge. A few plants may produce magnesium hydroxide in addition to the calcium carbonate. Softening sludge is an inorganic sludge. Each water treatment plant must determine its own sludge production rates as they are variable from plant to plant. Wastewater treatment plants produce screenings and grit in addition to the sludge generated every day. Screenings are large solid wastes that are collected on bar screens at the head of the treatment plant. Most plants collect the screenings and dispose of them with the other municipal solid wastes in sanitary landfills. A few plants grind the screenings and return them to the liquid stream. Logic indicates that it is simpler to handle the screenings as solid wastes once they have been collected. Grinding the screenings and returning them to the liquid wastes means that the screenings have to be removed twice from the wastewater. Grit is largely sand and dense organic particles that could damage mechanical equipment in the units that follow the grit chamber. Grit is usually washed as it is collected and used as fill material. The primary sludge and the biological sludge are combined and anaerobically digested before being dewatered and placed on the land. Most municipal wastewater treatment plants will produce about 0.14 kg/m 3 (1,200 Ibs TS/MG) wastewater treated. If 0.02 kg/m 3 (200 Ibs TSS/MG) are lost in the treated effluent, 0.12 kg/m 3 (1,000 Ibs TSS/MG) will be returned to the land environment. Wastewater treatment plants handling large quantities of industrial wastes will produce even more excess sludge. AUTOMOTIVE SOLID WASTES Every automobile sold in the United States will eventually become solid waste. Old automobiles are processed by automobile scrap dealers. With an average life of 7 to 8 years the number of automobiles scraped each year can be estimated by looking at the production data 7 to 8 years ago. With increased emphasis on waste recycling the automobile manufacturers have tried to use materials that could be processed and reused with a minimum of effort. The automobile scrap dealers remove all the parts of value before shipping the residue to a metal grinder and separator to recover the metal for reuse. Automobile tires pose one of the major processing problems for recycling. BULKY SOLID WASTES Every community produces bulky solid wastes from time to time. Bulky solid wastes are all large household items that are discarded. Stoves, refrigerators, washing machines, sofas, large chairs, beds, mattresses, and other large items Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. require special collection. Usually, the person discarding the item is responsible for seeing that the bulky waste is collected and delivered to the proper disposal site. Often, when a large item is replaced, the dealer selling the new item collects the old item and delivers it to the disposal site. Reclamation dealers remove any useful parts before sending the residue for recycling or for burial in a sanitary landfill. TREES As communities age, there will be a steady production of dead trees and trees removed for residential or commercial expansion. The dead trees are usually ground up and used for mulch in the community. Living trees removed from private or public property will be used commercially, where possible. Large trees can be cut for lumber; while small trees are mulched for use in paper production or in parks and gardens. Every effort is made to reuse the wood rather than burying it in sanitary landfills. AGRICULTURAL SOLID WASTES Farms produce large quantities of solid wastes. The quantities of solid wastes produced are a function of the specific crops grown on the farm. Farmers have long recognized that manure from farm animals and crop residues after harvest must be returned to the land to help maintain the soil quality for future crop production. Farmers are among the oldest of the recyclers in our society. The major problems in recent years have come from the large confined animal farms. The manure from the confined animal buildings is handled as a liquid waste rather than as a solid waste. Operators of the large confined animal farms have had to learn new methods of handling the liquid manure to minimize environmental pollution. The basic problem is processing the liquid manure for return to the land environment. It is not surprising that there are no simple solutions for processing the liquid manure as previously indicated. MINING SOLID WASTES The mining industry produces large quantities of solid wastes that must also be returned to the land environment. Mining results in the removal of non-valuable materials along with the valuable materials. The failure of the mining industry to properly handle the non-valuable solid materials at the same time they handled the valuable materials has produced localized environmental damages and created a negative image for the mining industry. Too often mining companies simply closed down and walked away from the mined area when the mining operation stopped being profitable. Some of the mining residues contain Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. hazardous chemicals that slowly wash into nearby streams, creating even more environmental damage. The net effect has been for the mining industry to have created a very negative impression on the public at large. It will take decades of major effort by the existing mining industry to overcome the current negative image and to correct the environmental damage that has been done over the years. PROCESSING SOLID WASTES Normal processing of solid wastes has always followed the path of least resistance. Solid wastes have always been handled with the least effort and the lowest cost. Since our interests are focused on the microbiological side of environmental pollution control, we will only examine those treatment processes that significantly deal with microorganisms. Our focus will be primarily on municipal solid wastes and agricultural solid wastes and how microorganisms can be used to stabilize these solid wastes. We will briefly examine how bacteria react with mining solid wastes to extract mineral elements. Biological treatment of solid wastes falls into three general categories: sanitary landfills, composting, and soil stabilization. Although sanitary landfills have been extensively used in the United States, the lack of understanding of how microorganisms react in sanitary landfills has created problems in both design and operation of sanitary landfills. Composting is another biological process that has not been fully evaluated from a microbiological point of view. Soil stabilization of solid wastes has long been used for treating agricultural solid wastes and has potential for treating any readily biodegradable solid waste. Since the production of solid waste will continue to be related to existing populations, we can expect to see increased production of solid wastes. It is essential that we understand how the microorganisms metabolize the biodegradable materials in solid wastes and what we can expect from biological treatment systems currently in operation. SANITARY LANDFILLS By definition sanitary landfills are engineered burial of solid wastes. Unfortunately, sanitary landfills grew up at a time when municipal government paid little attention to solid waste processing. Although municipal government is the primary beneficiary of well-designed and well-operated sanitary landfills, municipal government must accept full responsibility for all the problems related to sanitary landfills. Municipal officials put solid waste processing at the bottom of the problem pile until the environmentalists forced the federal government to make municipal officials face up to years of neglect in the area of Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. solid waste processing. Sanitary landfills should be carefully designed for maximum operating efficiency with a minimum of discomfort and objections from the citizens living around the landfill. Fundamentally, all sanitary landfills should be located within the boundaries of the community producing the solid wastes. This location allows the citizens of the community to continuously observe how their elected officials manage one of the most important municipal functions. It is completely possible to design and operate a sanitary landfill within the municipality without creating problems for the citizens or the municipal officials. Unfortunately, few communities are willing to make the effort that is required to construct and operate a sanitary landfill correctly. Most communities choose to establish their sanitary landfill far enough outside the community boundaries that few citizens know where the sanitary landfill is located or how it is being operated. Basic Concepts A sanitary landfill should be constructed in dry soil on flat terrain capable of holding at least 20 to 30 years production of solid waste from the contributing population. The natural water drainage should be away from the landfill site or should be diverted around the landfill site to prevent excess runoff from crossing the landfill and eroding the cover soil. Because of concerns about leachate formation and its effect on groundwater below the landfill, the bottom of the landfill should be sealed with clay or an impermeable membrane. A series of perforated pipes should be placed at intervals across the bottom of the landfill to collect the leachate and to convey it to a concrete sump where the leachate can collect and be pumped to a leachate storage facility prior to treatment. A layer of coarse sand is placed over and between the leachate pipes to prevent possible damage to the collection pipes by the tractor or tractors used for compacting the solid wastes in the landfill. The solid wastes should be placed first at the far end of the landfill. Bulldozers push the solid wastes into a corner and compact the solid wastes to their maximum concentration. By moving back and forth over the solid wastes the bulldozer is able to compact the solid wastes to a concentration close to 593 kg/m 3 (1000 Ibs/cy). Figure 13-1 shows a bulldozer compacting solid waste in a sanitary landfill. At the end of each day the compacted solid waste is covered with about 0.15 m (6 inches) of topsoil to act as a temporary cover. As more solid wastes are added to the landfill, the landfill slowly fills to the design level. As the landfill fills with solid waste, perforated gas collection pipes are placed in the upper part of the landfill to collect the gas produced in the landfill. The landfill is covered with a layer of clay or an impermeable membrane to minimize infiltration of water. The top of the impermeable layer is then covered with at least 0.61 m (2 ft) of topsoil. The topsoil is sloped to allow the natural storm water runoff to flow away from the Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved. [...]... Method, EPA-600/ 8-8 0-0 22 USDA (1998) Long Term Decomposition of Crop Residues in Dry Land Agroecosystems, TEKTRAN, Ag Res Service, March USEPA (2002) Municipal Solid Waste - Basic Facts, http://www.epa.gov, Web Site University of California (1953) Reclaiming Municipal Refuse by Composting, Tech Bull No 9, Series 37, Sanitary Engineering Research Project, Berkeley, CA Wiley, J S (1955) Studies of High-Rate... Recirculation, MSWManagement, 24, March/April McGauhey, P H (1971) American Composting Concepts, SW-2r, USEPA Metcalf & Eddy (1991) Wastewater Engineering, 3rd Ed., McGraw-Hill Richman, M (1966) Wrestling with In-Vessel Composting, WEF Operations Copyright 2004 by Marcel Dekker, Inc All Rights Reserved Forum, 13, 11, November Snell, J R (1957) Some Engineering Aspects of High Rate Composting, Jour San... temperature was controlled to maximize rapid microbial growth Professor Snell found the compost was finished when there was no significant increase in temperature, no further loss of nitrogen, and the compost had no offensive odors With all the increased interest in high-rate composting John S Wiley of the USPHS set up his own experiments to determine the primary factors affecting the high-rate systems... facultative or strict anaerobes The high protein content of the manure helps keep the pH high as NH 3 -N is released The organic acids formed as end products of anaerobic degradation are quickly neutralized by the excess NH3-N, allowing the methane bacteria to metabolize the organic acids The breakdown of lignin-cellulose compounds by the cattle allows cellulose bacteria to grow in the manure Returning the...Figure 1 3-1 BULLDOZER COMPACTING SOLID WASTES AT THE LAWRENCE, KS SANITARY LANDFILL landfill into catch basins and a storm water collection sewerage system to minimize the infiltration of rainwater into the landfill... Dekker, Inc All Rights Reserved accumulate for one to two years before using it Yard waste composting confirms the observation from other solid wastes that lignin-cellulose materials degrade slowly Fungi and actinomycetes metabolize lignin-cellulose materials under aerobic conditions provided there are sufficient nitrogen, phosphorus, and trace metals for normal cell growth These microbes require less... stabilization of the biodegradable organic matter The problem with recycling the leachate from the bottom of the landfill around the landfill is the accumulation of soluble, non-biodegradable contaminants in the leachate The soluble non-biodegradable materials accumulate in the recycled leachate on each pass through the solid wastes in the landfill Eventually, the accumulated nonbiodegradable materials may... favor harvesting the crop residues for feeding cattle as part of their overall rations No-till advocates definitely favor leaving crop residues on the land The opposite view indicates that crop residues tend to accumulate on the soil surface, making planting of new crops more difficult It has also been indicated that no-till cropping can lead to increased transmission of microbial plant diseases Crop residues... ground crop residues since there are more nutrients and trace metals available from the soil A study reported by the USDA Agricultural Research Service in TEKTRAN indicated a long-term study of crop residue reduction in three no-till sites in eastern Colorado found a 43% yearly average residue loss The residue loss also followed a first order relationship It appears that limited mixing of the crop residues... sludge 13 High rate composting systems only stabilize the readily biodegradable organic compounds 14 Curing is required for at least 3 to 6 months or longer before most compost is stable enough to be used 15 Soil stabilization of wastewater sludge has been quite successful at many WWTP 16 Crop residues are decomposed at a slow rate, requiring years for stabilization 17 Mixing, moisture, and nutrients control . Chapter 13 SOLID WASTES Solid wastes are one of the more interesting environmental contaminants to deal with. The primary characteristic . wastes that are not very bio-stable. From a practical point of view environmental microbiologists are only interested in the solid wastes having the least bio-stability. There are many. multiple family units. 2. Commercial SW - all solid wastes produced by commercial establishments within the classification area. 3. Industrial SW - all non-hazardous solid wastes produced