Developing Human Health-related Chemical Guidelines for Reclaimed Waster and Sewage Sludge Applications in Agriculture

Transcription

1 Developing Human Health-related Chemical Guidelines for Reclaimed Waster and Sewage Sludge Applications in Agriculture Prepared for World Health Organization By Andrew C. Chang 1, Genxing Pan 2, Albert L. Page 1, and Takashi Asano 3 1 University of California, Riverside, California, USA 2 Nanjing Agricultural University, Nanjing, People s Republic of China 3 University of California, Davis, California, USA September 30, 2001 Revised May 17, 2002

2 Summary and Conclusions This document is an update of a 1994 report on evaluating the methodology of developing human health-related chemical guidelines for irrigating crops with reclaimed wastewater and using sewage sludge as fertilizer (Chang et al. 1995). The work was completed under a contract with the World Health Organization, Community Water Supply and Sanitation Unit, Division of Environmental Health, Geneva, Switzerland. Systematic land applications of wastewater and sewage sludge have been practices around the world for more than a century. While technical information on using municipal wastewater and sewage sludge in crop irrigation have appeared in published literature since the early 1900s, documentations of such practices tended to be provincial and were not always obtainable from the electronic information retrieval systems. Data often existed as unpublished internal documents of various agencies in countries around the world. These documents have limited circulation and invariably prepared in language of the country they originated. Literature reviewed and cited in this report represent only a small fraction of those that were brought to the attention of the investigators. As a result, it was difficult to estimate the extent of the land application practices on a global scale and to evaluate fully their benefits as well as potential environmental impacts. The World Health Organization, perhaps, should initiate an inventory of land application operations worldwide and establish a database of available literature on land application. A global water shortage is looming on the horizon. The interests of water reuse are rapidly growing. By critically reviewing the technical issues involved in the development of guidelines for cropland application of reclaimed wastewater and sewage sludge, the World Health Organization may direct the attention of interested parties to safeguard these practices worldwide. In this study, we have analyzed the information available to us, addressed health concerns regarding sodium and nitrate ions, as requested by the World Health Organization, and have evaluated the existing methodologies and factors necessary for developing globally-applicable guidelines for inorganic and organic pollutants. Based on the assumption that food chain transfer is the primary route of exposure to potentially hazardous pollutants in the wastewater and sewage sludge, numerical limits defining the maximum permissible pollutant concentrations in soils are derived for a set of organic and inorganic pollutants. The global diet was used to represent the food consumption pattern. The outcomes of the investigations illustrated the difficulties of establishing guidelines for land applications. 1. Land application has been a popular option for disposing of municipal wastewater and sewage sludge worldwide for more than a century. While most of the operations appear to be successful, reports from countries such as China suggested that large-scale irrigation of crops with mostly untreated municipal and industrial wastewaters could be harmful to crops and cause injuries to humans because of poorly controlled discharge of toxic and hazardous constituents in the wastes. ii

3 2. Concentrations of potentially hazardous pollutants in the municipal wastewater and the resulting sewage sludge varied considerably from location to location and, for the same community, were subject to temporal variations due primarily to point-source discharges from industries. The frequency of detection for inorganic pollutants, such as the trace elements in the wastewater, usually ranges from 50 to 100% and they are invariably concentrated into the sewage sludge in the course of wastewater treatment. The frequency of detection for organic pollutants was considerably lower. They range usually from 5 10% and their concentrations, when found, were low. Community-wide industrial wastewater pretreatment provisions to prevent the discharge of pollutants by industries have been effective in reducing the pollutant concentrations in wastewater and sewage sludge. 3. The two approaches, as explained below, differ in their underlying principles and may be employed in the development of guidelines to safeguard the cropland application of reclaimed wastewater and sewage sludge. Prevent Pollutant Accumulation in Waste-Receiving Soils. In land application, if the pollutant input equals to the pollutant output, there will not be a net accumulation of pollutants in the receiving soil. Consequently, the pollutant contents of the soil will remain at the background level and the soil's ecological and chemical integrity are preserved. When this requirement is met, the capacity of the soil to sustain any future land uses is guaranteed and the transfer of pollutants up the food chain is kept to a minimum. Numerical limits, therefore, are set to prevent the pollutant concentration of the soil from rising during the course of land application. Guidelines derived from this approach will have stringent upper limits for pollutants and are universally applicable. The cost of implementation will be high as wastewater treatment plants need to employ the advanced wastewater treatment technologies to minimize the pollutant levels in the reclaimed wastewater and sewage sludge. Taking Maximum Advantage of the Soil's Capacity to Assimilate, Attenuate, and Detoxify Pollutants. Soils possess natural abilities to assimilate, attenuate, and detoxify pollutants. In land applications, this capacity should be fully utilized. In this manner, the agronomic benefits of applying wastewater and sewage sludge may be realized and, when managed properly, accumulation of pollutants in soil can be controlled so that they will not reach levels harmful to human health. Land application guidelines based on this approach set the maximum permissible pollutant loading and provide users the flexibility to develop suitable management practices for using wastewater and sewage sludge within the boundary. Under this scenario, pollutant levels in the soil, however, will rise eventually to levels considerably higher than the background levels, and future land uses may be restricted. Also, the technical data needed to define the pollutant transfer parameters of the exposure pathways are not always available. Both approaches were considered in this investigation and their principles were iii

4 employed to guide the cropland application of reclaimed wastewater and sewage sludge under different circumstances. Details will be discussed later. 4. For communities that have effective industrial wastewater pretreatment programs, the pollutant discharge into the wastewater collection and treatment systems is effectively regulated and pollutants incompatible with land application may be screened out. The reclaimed wastewater from these communities may be used for crop irrigation without undue restrictions, provided the bacteriological quality of the water is acceptable and the volume of water applied does not exceed the normal water requirement for a successful crop harvest. In this manner, the pollutant input to the receiving soil, realistically, may be balanced by the outputs through plant absorption when the reclaimed wastewater is used for irrigation. 5. For other waste streams (sewage sludge, partially treated wastewater, and untreated wastewater), when applied on cropland, the pollutant inputs to the receiving soils may be substantial and will result in a gradual accumulation in soils. It is imperative that upper limits for pollutants in soils be established. To optimize the agronomic, the pollutant attenuation capacity of the soil should be utilized to accommodate waste application. 6. To derive the numerical limits for pollutant input in land application, the process starts with establishing the acceptable daily human intake (ADI) for a pollutant. It then quantitatively backtracks the pollutant transport through various environmental exposure routes to arrive at an acceptable pollutant concentration for the receiving soil. Human exposures to pollutants released by the land application may take place through seven pathways, namely, waste soil plant human, waste soil human, waste soil plant animal human, waste soil animal human, waste soil airborne particulate human, waste soil surface runoff surface water human, waste soil vadose zone groundwater human, and waste soil atmosphere human. 7. To obtain the preliminary numerical limits for land application of wastewater and sewage sludge, a simplified approach was adopted. Instead of assessing all of the exposure routes, we considered only the food chain transfer of pollutants via the waste soil plant human route and considered only the pollutant intake from consumption of grain, vegetable, root/tuber, and fruit. Food chain transfer is the primary route of human exposure to environmental pollutants. Based on the global diet, daily intake of grain/cereal, vegetable, root/tuber, and fruit account for about 75% of daily adult food consumption. The exposure scenario assumed that most exposed individuals were the adult residents (60kg in body weight) of a land application area whose entire consumption of grain, vegetable, root/tuber, and fruit were produced from the soils affected by the waste streams. Their daily intake of pollutants from consumption of grain, vegetable, root/tuber, and fruit foods accounts for 50% of the ADI. The remaining 50% of the ADI is credited to the background exposure. This simplification should not seriously affect the final iv

5 outcome and yet will greatly alleviate the need for extensive input data. The maximum permissible pollutant concentrations in the receiving soils are summarized as follows: Inorganic Element Soil Concentration Soil Concentration (mg kg -1 Organic Compound ) (mg kg -1 ) Ag 3 Aldrin 0.48 As 8 Benzene 0.14 B* 1.7 PAH (as benzo(a)pyrene) 16 Ba* 302 Chlorodane 3 Be* 0.2 Chlorobenzene 211 Cd 4 Chloroform 0.47 F 635 Dichlorobenzene 15 Hg 7 2,4 D 0.25 Mo* 0.6 DDT 1.54 Ni 107 Dieldrin 0.17 Pb 84 Heptachlor 0.18 Sb 36 Hexachlorobenzene 1.40 Se 6 Pyrene 41 Tl* 0.3 Lindane 12 V* 47 Methoylchlor 4.27 Pentachlorophenol 14 PCBs 0.89 Tetrachloroethane 1.25 Tetrachloroethylene 0.54 Toluene 12 Toxaphene ,4,5 T 3.82 Trichloroethane 0.68 Phthalate 13,733 Styrene 0.68 Dioxins *The computed numerical limits for these elements were within the range that is typical for soils. The values presented in the above table were derived strictly from computation, involved empirical parameter values estimated with currently applied method in the uniform system for the evaluation of substances (USES). Because of the uncertainties surrounding the selection of data and the difficulty of defining an exposure scenario that is truly global, we feel these numerical limits are by no means absolute. If the methodology is deemed acceptable, these values provide estimates of what the numerical limits may look like and permit us to identify what types of technical information are necessary to refine the estimates or to conduct site- and case-specific evaluations. The numerical limits of B, Be, Ba, Mo, Tl, and V were comparable to the typical v

6 concentration of soils around the world. The overlap of computed numerical limits to their respective typical concentrations in the soils indicate that, in land application of reclaimed wastewater and sewage sludge, the margin of safety for these elements may be narrower that other elements on this list. As the USES can only provide approximations, the parameter values for B, Be, Ba, Mo, Tl, and V require care evaluation and further refinement. The calculated maximum permissible concentrations for organic constituents varied considerably. For dioxin and toxaphene, the tolerances were virtually zero due to a combination of very low acceptable daily intake (ADI) and high potentials for plants to absorb these two chemicals. Comparing to dioxin and toxaphene, the organic solvents (benzene, tetrachloroethane, tetrachloroethylene, toluene, and trichloroethane) have relatively high ADIs. The calculated numerical limits for these compounds remain low because plants may readily absorb them from the soils. PAHs, chlorobenzene, pyrene, pentachlorophenol, and phthalate that are hazardous under other environmental settings did not appear to be critical under the cropland application, primarily because of their extremely low potential for being absorbed by plants. 8. The numerical limits for pollutants in soils may be expressed either as the annual or cumulative mass loading or as the maximum pollutant concentrations of the soils. We believe the maximum permissible pollutant concentration of soil is a more suitable global reference point. It establishes a universal upper limit without the need of accounting possible past and/or future pollutant inputs from other sources. 9. This investigation demonstrated that numerical limits for pollutants may be developed to safeguard human health from possible exposures to pollutants released during the land application of wastewater and sewage sludge. It also illustrates the potential deficiencies. While the technical database for establishing the numerical limits may be refined, the inherent variability in diets, environmental exposure to pollutants, and soil and plant partition coefficients will always be problematic, from a global perspective. 10. In land application of reclaimed wastewater and sewage sludge, the numerical limits on pollutant inputs ideally should be evaluated on a site- and case-specific basis. When the environmental pathways, exposure scenarios, and parameters for the mathematical equations are calibrated accordingly, the outcomes are far more reliable. In this regard, it may be more appropriate to establish a standardized protocol and a technical data bank from which site- and case-specific evaluations on the merits of land application may be derived. For this purpose, a computerbased model should be developed. The model will enable the users to select the appropriate pollutants, exposure pathways and exposure scenarios and a regularly updated database from which the ADIs, coefficients for environmental transfer, etc. may be obtained in a consistent manner. vi

7 11. The potential ecological consequences of releasing the pharmaceutically active ingredients and endocrine disrupting substances through the land application of reclaimed wastewater and sewage sludge were not categorically considered. In land application, compounds belonging to this category are not expected to accumulate in the harvested food to levels that would constitute to the administration of a therapeutic dose when the harvested food is consumed. Further, no adverse health effect associated with the land application has been linked to the endocrine dysfunction of humans. Many of the organic chemicals identified through the hazard identification process and the numerical limits for these compounds were subsequently derived however exhibit endocrine disrupting characteristics. They include, aldrin, dieldrin, benzo(a)pyrene, pyrene, phthalate, PCBs, and dioxins. These compounds were included in the recommendation because of their potential adverse effects on human health not related to the hormonal disorders. The numerical limits may indirectly prevent the uncontrolled release of endocrine disrupting substances through land application of reclaimed wastewater and sewage sludge. We believe that the potential environmental consequences of endocrine disrupting substances require long term and continuous monitoring. Issues related to the ecological impacts of land application should be revisited regularly in the future. vii

8 Table of Contents Summary and Conclusions Table of Contents List of Tables ii viii x Chapter 1. Introduction 1.1 Land Application of Reclaimed Wastewater Land Application of Sewage Sludge Public Health Concerns Pathogens and Toxic Chemicals Pathogens Toxic Chemicals Issues in Land Applications Emerging Pollutants Disinfection Byproducts, Pharmaceutically-active Ingredients, and Endocrine Disruptors Disinfection Byproducts Pharmaceutically-active Ingredients and Endocrine Disruptors Scope of The Report 15 Chapter 2. Approaches for Criteria Development 2.1 Water Quality Criteria Guidelines, Criteria, and Regulations for Land Application of Reclaimed Wastewater and Sewage Sludge Preventing Pollutant Accumulation in Waste-Receiving Soils Taking Maximum Advantage of the Soil s Capacity to Assimilate and Detoxify Pollutants Evaluation of Selected Criteria and Regulations Irrigation Water Quality Criteria Land Application of Municipal Sludge Recent Developments in European Union Perspectives Concluding Remarks Waste Category Approaches of Controlling Pollutant Release 41 viii

9 Chapter 3. Risk-based Assessment of Human Health Hazards 3.1 Hazard Identification Health Concerns of Nitrate and Sodium Ions Nitrate Ion Sodium Ion Dose-Response Analysis Exposure Analysis Pathway 1: Sludge-Soil-Plant-Human Pathway 2: Sludge-Soil-Human Pathway 3: Sludge-Soil-Plant-Animal-Human Pathway 4: Sludge-Soil-Animal-Human Pathway 10: Sludge-Soil-Airborne Particulate-Human Pathway 11: Sludge-Soil-Surface Runoff-Surface Water-Human Pathway 12: Sludge-Soil-Vadose Zone-Groundwater-Human Pathway 13: Sludge-Soil-Atmosphere-human Remarks Selection of An Exposure Analysis Method Exposure Scenario Employed Daily Food Intake Fraction of Diet Affected by Land Spreading of wastes Pollutant Partition Factor Between Soil and Plant (K sp ) Acceptable Daily Intake (ADI) Body Weight (BW) Background Pollutant Exposure Computation of Soil Pollutant Concentration Results Concluding Remarks Needs of a Computer Model 76 Chapter 4. Guideline Formulation 4.1 Pollutant Source Control Maximum Permissible Pollutant Concentrations of Soils Receiving Sewage Sludge and/or Untreated Municipal Wastewater Potential Long Term Adverse Ecological Impact of Land Application 79 References 80 ix

10 List of Tables Table 1.1 Reclaimed Water Uses in California 3 Table 1.2 Sewage Sludge Productions and Disposal Methods in the United States 5 Table 1.3 Sewage Sludge Disposals in Western European Countries 6 Table 1.4 Frequencies of Detection for Chemical Constituents Found in Sewage Sludge, According to the U.S. Environmental Protection Agency 1986 National Sewage Sludge Survey 9 Table 2.1 Irrigation Water Quality Criteria of Selected Countries 26 Table 2.2 Estimated Trace Element Inputs form Irrigation vs. Typical Trace Element Contents of Soils and Plant Tissue 28 Table 2.3 Physical State of Impurities of Municipal Wastewater 29 Table 2.4 Typical Concentrations of Selected Elements in Untreated Wastewater 30 Table 2.5 Pollutant Removal Efficiencies of Conventional Wastewater Treatment Processes 31 Table 2.6 Annual Pollutant Loading Limits of Sewage Sludge-treated Soils 32 Table 2.7 Total Cumulative Metal Loading of Sewage Sludge-treated Soils of Selected Countries 32 Table 2.8 Maximum Contamination Levels (MCL) for Land Application of Sewage Sludge in the U.S. 33 Table 2.9 Maximum Permissible Metal Concentrations of Sewage Sludge for Land Application in The Netherlands 35 Table 2.10 Trends in Metal Concentrations of Sewage Sludge Produced by Wastewater Treatment Plants in the U.S. 35 Table 2.11 Metal Concentration Limits for Sewage Sludge-treated Soils, Proposed by Cornell University Waste Management Institute 36 Table 2.12 EU Proposed Numerical Limits of Heavy Metals in Sludge for Use on Land 37 Table 2.13 Target Sludge Quality and Annual Pollutant Loading for 90% of the Sludge Produced in EU Member Countries 38 Table 2.14 EU Proposed Maximum Heavy Metal Contents of Soils Beyond Which the Land Application of Sludge May be Restricted 38 Table 2.15 EU Proposed Numerical Limits of Organic Compounds and Dioxins in Sludge for Use on Land 39 Table 2.16 People's Republic of China National Standards GB , Maximum Permissible Pollutant Concentrations in Sludge Applied on Agricultural Land 40 Table 2.17 People's Republic of China National Standards GB , Environmental Standards for Soils 40 Table 3.1 Occurrence of Toxic Organic Chemicals in Wastewater from 23 Treatment x

11 Plants in Canada 46 Table 3.2 Listing of Potential Toxic Chemicals in Regulatory Documents 47 Table 3.3 Inorganic Elements Listed in Selected Standards and Guidelines 49 Table 3.4 Organic Compounds Listed in Selected Standards and Guidelines 50 Table 3.5 Reference Dose (R f d) of Inorganic Elements 55 Table 3.6 Reference Dose (R f d) of Organic Chemicals 55 Table 3.7 Pollutant Transport Pathways and Exposure Scenarios 58 Table 3.8 Selected Food Consumption Patterns 67 Table 3.9 Plant and Soil Partition Coefficient (K sp ) for Inorganic Chemicals 69 Table 3.10 Plant and Soil Partition Coefficient (K sp ) for Non-ionic Organic Chemicals as Calculated by Eq Table 3.11 Maximum Pollutant Level Computation Table for Inorganic Chemicals 72 Table 3.12 Maximum Pollutant Level Computation Table for Organic Chemicals 73 Table 4.1 Maximum Permissible Pollutant Concentrations of Soils Receiving Sewage Sludge and/or Untreated Municipal Wastewater 78 xi

12 Chapter 1. Introduction Archaeological evidences have traced the practice of domestic wastewater conveyance and disposal back to antiquity (Asano and Lavine, 1996). The concept of establishing a community-wide wastewater collection, treatment, and disposal infrastructure, however, did not emerge until the late 19 th century. From the very beginning, land application was a common practice and an integral component for municipal wastewater disposal, and many large urban centers around the world applied their wastewaters to land for a long time. Noted examples were the "sewage farms" established in Paris, France in 1869; Berlin, Germany in 1874; and Melbourne, Australia in 1896, as cited by Jewell and Seabrook (1979). Early supporters of land application advocated the use of soil as a "treatment" medium and considered wastewater as a source of plant nutrients, in contrast to the then customary "directly-discharge of untreated sewage that had fouled the receiving water bodies. In land application, the need for an all-season reliable discharge outlet was not always compatible with the seasonal fluctuations of water and nutritional requirements of growing plants. While land application was a welcomed solution for sewerage authorities, most early systems were plagued with both hydraulic and pollutant overloading and the consequent operational problems that pollution and public nuisances were rampant (Jewell and Seabrook, 1979). Because of these problems, the sanitary engineering profession turned to other options for the solution of wastewater disposal (Chase, 1964a). While technical information on using municipal wastewater and sewage sludge in crop irrigation have appeared in published literature since the early 1900s, documentations of such practices tended to be provincial and were not always obtainable from the electronic information retrieval systems. Data often existed as unpublished internal documents of various agencies in countries around the world. These documents have limited circulation and in variably prepared in language of the country they originated. The recent developments in electronic communication have greatly accelerated the dissemination of the technical information. The internet-based data however lack the permanency of technical journal articles or published documents and they may not always be retrievable at a future data as the information posted may be replaced or removed at the discretion of the owner of the website. Literature reviewed and cited in this report represent only a small fraction of those that were brought to the attention of the investigators. It was difficult to approximate the extent of the land application practices on a global scale and to evaluate their benefits as well as potential environmental impacts. To effectively plan and implement land application systems, it is advantageous to develop a comprehensive electronic information network that link such resources worldwide. 1

13 1.1 Land Application of Reclaimed Wastewater The interest of applying municipal wastewater to land re-surfaced in the Western Hemisphere during because the quality of treated effluents steadfastly improved as wastewater treatment technology advanced (Chase, 1964b). Land application became a cost-effective alternative to surface water discharge and was especially attractive in the semi-arid and arid regions of the world as treated effluents could be used to supplement the growing demand for water (Stone, 1952). Scientific and engineering investigations concentrated on the hydraulics of dissipating water and on public health aspects of pathogen survival and transport (Orlob and Butler, 1955; Gotaas et al., 1955). This time around, the circumstances had changed. Unlike the early practices, most of the land treatment systems were successful because the hydraulic and pollutant assimilation capacities of soils were understood better. Many of the difficulties resulting from pollutant overloading and public nuisance were remedied by properly treating the wastewater prior to land application. The soil mantle could serve as an effective treatment system in attenuating wastewater pollutants (McGauhey, et al., 1966). Long-term environmental impacts from irrigating with reclaimed wastewater appeared to be minimal (Benham-Blair & Associates, Inc. and Engineering Enterprise, Inc. 1979; Renolds et al., 1979; U. S. Environmental Protection Agency, 1991). In addition to its use for irrigation, reclaimed wastewater may also be used for groundwater recharge and other industrialbased beneficial reuses. There is no systematic inventory of the existing wastewater reclamation and reuse projects and this type of information is not readily obtainable from commonly used information retrieval systems. Based on limited knowledge in the published literature, there have been more than 3000 land application sites in the United States alone (Jewell and Seabrook, 1979; U. S. Environmental Protection Agency, 1981 and 1992a). In developing countries, land application has always been the predominant means of disposing of municipal wastewaters as well as meeting irrigation needs (Al-A ama and Nakhla, 1995; Bahri and Houmane 1988; Kansel and Singh, 1983; Zhang and Liu, 1989; Abdel-Reheem et al., 1986; Ul-Haque et al., 1986; Sanai and Shayegen, 1980). In Athens, Greece, 7 x 10 5 m 3 /day of primary effluents were reused and crop and landscape irrigation was the major uses (Yiannis and Alexopoulou, 1996). In China, at least 1.33 x 10 6 hectares of agricultural land are irrigated with untreated or partially treated wastewater from cities (Wang, 1984). In Mexico City, Mexico, a metropolis of 15 million inhabitants, more than 70,000 hectares of cropland are irrigated with reclaimed wastewater (Villalobos et al., 1981). Sewage effluents have been used for crop irrigation at a municipality operated farm for over 60 years in Cairo, Egypt (Abdel-Sabour et al., 1995). Heaton (1981) reported wastewater reclamation and reuse in Israel, Saudi Arabia, Iran, South Africa, The Netherlands, and Germany. Judging from the origins of these activities, land application is practiced on every continent. A recent survey of non potable water reuse management practices conducted for the U. S. based Water Environment Research Foundation included 40 projects in the U.S with capacity of reuses ranging from 0.02 to 5.5 m 3 /sec and 25 projects from 13 countries with reclaimed water volume varying from 0.1 x 10-3 to 5.5 m 3 /sec (Vivendi Water, 2

14 1999). In California, water recycling is an integral part of the strategic plan for statewide water management plan and 496 x 10 6 m 3 of reclaimed water are beneficially used annually (California Water Resources Control Board, 2000). Agricultural and landscape irrigation accounted for approximately 70% of the total reclaimed water used (Table 1.1). Several guidelines and manuals have become available for using reclaimed wastewater for crop irrigation (Pettygrove and Asano, 1985; World Health Organization, 1989c; Pescod, 1992; U. S. Environmental Protection Agency, 1992a). Human health issues related to the introduction of toxic pollutants via wastewater irrigation, however, were not explicitly addressed. Table 1.1 Reclaimed Water Uses in California Type pf Reuse Agricultural Irrigation Landscape Irrigation and Impoundment Industrial Use Ground Water Recharge Seawater Intrusion Barrier Recreational Impoundments Wildlife Habitat Enhancement Miscellaneous Total Volume (10 6 m 3 /year) Percent (%) Office of Water Recycling, California Water Resources Control Board, 2000 ( 1.2 Land Application of Sewage Sludge When the collected wastewater was directly discharged, sewage sludge did not exist. As wastewater treatment technology advanced and the potential pollutants were removed from the wastewater, the treated effluents became less a threat to the public health and the dissolved oxygen levels of the receiving waters. The reliance on land application to dispose of wastewater rapidly diminished; instead, the treated effluents were discharged routinely into surface water bodies. With the advancement of wastewater treatment, the volume of sewage sludge incrementally increased. As the residue of municipal wastewater treatment, sewage sludge represents the aggregation of organic matter, pathogens, trace elements, toxic organic chemicals, 3

15 essential plant nutrients, and dissolved minerals originally dispersed in the wastewater and were captured and transformed by the wastewater treatment processes. Compared to the volume of wastewater being treated, the volume of sludge produced in a wastewater treatment work is not extraordinarily large. The sludge, however, is costly to handle and there has not been a satisfactory solution to its final disposal, regardless of the treatment. Land application, land filling, ocean dumping, and incineration are all used to dispose of sewage sludge. An estimated 5.3 million dry tons of sewage sludge is produced annually in the United States (Table 1.2) and, in a 1992 document, comparable amounts were reported in the western European nations (Table1.3). 4

16 Table 1.2 Sewage Sludge Production and Its Disposal Methods in the United States (Bastian, 1997) Region Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont Amount Disposal Method (as % of Total Amounts) (Ton/Year) Land Application Surface Disposal Incineration Other 367, New Jersey, New York, and Puerto Rico 605, Delaware, Maryland, Pennsylvania, Virginia, West 1,040, Virginia, and Washington D.C. <1 Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and 1,050, Tennessee Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin 1,705, Arkansas, Louisiana, Oklahoma, New Mexico, and 425, Texas Colorado, Montana, North Dakota, S. Dakota, Utah, and Wyoming Arizona, California, Hawaii, and Nevada 819, Alaska, Idaho, Oregon, and Washington 220, Shipped out of the region for land application. 2 Long-term storage. Data derived from Bastian (1997). 5

17 Table 1.3 Sewage Sludge Disposals in Western European Countries Country Amount Disposal Method (as % of Total Produced) (10 3 T/yr) Agriculture Landfill Incineration Other Austria Belgium Denmark France Germany (W) 2, Greece Ireland Italy Luxembourg Holland Portugal Spain Switzerland UK 1, Total 6, Data derived from Davis, A more recent report showed that as much as 8 x 10 6 tons of sewage sludge may be produced in the member countries of the European Union (Bonnin, et al., 2001). Significant amounts of sewage sludge produced in the United States and the western European nations have been applied on land (U. S. Environmental Protection Agency, 1993; Davis, 1992; Bastian, 1997). In a survey of its production, use, and disposal, the United Kingdom reported that nearly 45% of the nation's sewage sludge is spread on approximately 0.3% of the agricultural land (Department of Environment, 1993). The remainder is dumped in the ocean (30%), buried in landfills (13%), incinerated (7%), and diverted to other beneficial uses (6%). The situations in other parts of the world are expected to be similar. Bonnin (2001) reported that 65% of the sewage sludge in France was land applied. If it were not for the potentially hazardous trace elements and toxic organic pollutants, land application would be ideal for sludge disposal because this practice could be mutually beneficial for the municipalities and the farmers. While the agricultural land provides a reliable outlet for municipal sludge, the N, P, and organic matter added into the soil create favorable agronomic conditions for plant growth. Following the promulgation of the Standards for the Use and Disposal of Municipal Sewage Sludges (Code of Federal Regulations, Title 40, Part 503) by the U.S. Environmental Protection Agency, land application has become an increasingly common option for the treatment and disposal of sewage sludge disposal in the United States (Bastian, 1997). In California, over 60% of the publicly owned treatment works in the state employed land application in sewage sludge management (California Association of Sanitation Agencies, 1999). 6

18 1.3 Public Health Concerns- Pathogens and Toxic Chemicals Pathogens Since the discovery of germ theory, the overriding concern of wastewater treatment and disposal has been the elimination of pathogens. Even with treatment, reclaimed wastewater and its unavoidable byproduct, sewage sludge, remained potential sources of human pathogens that could spread via a fecal-oral route when the material is released. Using wastewater for crop irrigation or sewage sludge as fertilizer might shortcircuit the fecal-oral transmission route and raise the possibility of spreading epidemic diseases unless the pathogens in the wastes were effectively inactivated or eliminated. Pathogen survival in land application systems has been investigated (Rudolfs et al., 1950; Benarde, 1973; Burge and Marsh, 1978, Frankenberger, 1985). Epidemiological investigations showed that, with proper treatment of the wastewater and regulation of its use, there was little indication that disinfected wastewater could not be safely used in crop and landscape irrigation (Uiga and Crites, 1980). At an epidemiological study involving the populace in and around a 1,500-hectare wastewater application site in Texas, although spray irrigation of wastewater produced no obvious and significant outbreak of disease, the rate of viral infections was slightly increased among those receiving a higher degree of exposure through aerosols of spray irrigation (George et al., 1986). The World Health Organization has developed a microbiological guidelines for proper use of wastewater in agriculture (1989c). Based on results of longterm virological, bacteriological, and chemical assays of harvested vegetables, the safety of irrigating with the oxidized and filtered effluents was comparable to the use of locally available groundwater (Sheikh et al., 1990). Several studies indicated that the use of secondary or tertiary treated wastewater effluents for food crop production is safe and acceptable in terms of the potentials for pathogen and trace element contamination of food (Pound et al., 1978; Benham-Blair and Associates, Inc. and Engineering Enterprises, Inc., 1979; Renolds et al, 1979; Hinesly et al., 1978; George et al., 1986; Sheikh et al., 1990). Most studies, however, did not address the issues related to the potentially toxic trace organic pollutants in wastewater irrigation Toxic Chemicals Municipal wastewater is a source of chemical pollutants that may affect human health. Tens of thousands of chemicals are being used routinely in manufacturing, in agricultural production, and in household products. One compilation listed almost 8000 regulated chemicals (ChemADVISOR, Inc., 1992). A fraction of the potentially toxic chemicals may inadvertently find their way into the municipal wastewater collection systems. There is no effective method to routinely monitor hazardous pollutants present in the wastewater (World Health Organization, 1975). A survey of publicly-owned treatment works in the United States showed that the concentrations of priority pollutants 7

19 in influent wastewater often exceed the allowable concentration limits (Bhattacharya et al., 1990). Results from pilot-scale wastewater treatment systems spiked with selected toxic chemicals indicated that up to 90% of the added chemicals might be removed from the wastewater. Certain compounds such as di- and tri- chlorobenzenes, hexachlorobutadiene, dibutyl phthalate, butyl benzyl phthalate, bis(2-ethylhexyl) phthalate, naphthalene, lindane, dieldrin might be found to concentrate in the sludge fractions (Bhattacharya et al., 1990). Surveys in the U.S. revealed that both the occurrence and the concentration of toxic pollutants in municipal wastewater and sewage sludge were extremely variable (Blakeslee, 1973; Chen et al., 1974; Feiler, 1979; Klein et al., 1974; Levins, et al., 1979; Minear et al., 1981), and the outcomes were often influenced by industrial waste pretreatment requirements. Upon entering the wastewater collection system or during the wastewater treatment, trace elements and organic chemical pollutants tend to be sorbed onto particulates and end up in the sludge fraction. However, even effluents processed with the most advanced wastewater treatment technologies contain traces of organic pollutants (McCarty and Reinhard, 1980). Even the municipal sludge produced a long time ago was not free of potentially harmful elements. Rudolfs and Gehm (1942) reported typical municipal sludge in the United States contained, on the dry weight basis, , , 930-1,860 and up to 1,400 mg kg -1 dry weight of Cu, Zn, Pb, and Cr, respectively. When industrial waste contributes significantly to the wastewater flow, sludge containing 41,000, 12,000, 26,000, 62,000, and 1,500 mg kg -1 dry weight of Cr, Cu, Pb, Zn, and Cd, respectively have been reported (Matthews, 1984). In the non-industrial communities, the trace metal contents of sewage sludge are significantly lower. Akhter (1990) reported the average concentration of Cd, Cu, Ni, Pb and Zn in the 12 month old sewage sludge in Bahrain were 9.2, 380, 53, 186, and 729 mg kg -1 dry weight, respectively. In addition to trace elements, potentially toxic organic pollutants were also prevalent in municipal sludge (Jacobs, et al., 1987; Rogers, 1987). Rogers (1987) reported that polychlorinated biphenyls, polyaromatic hydrocarbons, chlorinated aromatics, and pesticide residues occurred in sludge within the range of 1-10 mg kg -1 dry weight. The widely used surfactants, alkylbenzene sulphonates and polyethyloxylates, may be found in sludge at levels as high as 1,000 mg kg -1, dry weight. Due to rigorous and persistent enforcement of industrial waste pretreatment standards, the toxic pollutant concentrations of municipal sludge in the United States have declined considerably over the past 25 years (U. S. Environmental Protection Agency, 1990, Pietz, et al, 1998). In 1988, U.S. Environmental Protection Agency conducted a national sewage sludge survey in which 208 sludge samples were obtained for analyses of >400 chemical constituents (U.S. Environmental Protection Agency, 1990). Among those analyzed, 254 chemicals were not detected in any of the samples and only 56 chemicals had frequencies of detection of 10% or greater (Table 1.4). In land application, the human health-related issues involving toxic chemicals must be addressed. Reports from China have indicated serious human health problems related to long-term irrigation with wastewater heavily polluted by industrial waste 8

20 discharge. A report estimated that 8.4% of the 2.1 x 10 6 hectares of wastewater-irrigated farmlands in China are seriously polluted and almost 50% of the total acreage exhibited pollutant accumulation in soils (Anonymous, 1992b). Yuan and Zhao (1987) studied the adverse health effects in a petroleum wastewater-irrigated area in China and reported that, among the 13,621 subjects examined, the incidence of hepatomegaly were 10.61%, 1.92% and 0.42% of the subjects residing in the heavily polluted area (>50 years of wastewater irrigation), the lightly polluted area (22 years of wastewater irrigation), and the control area (no wastewater irrigation), respectively. Although the soils and the rice produced on these soils had higher concentrations of mineral oil, phenol, and benzo(a)pyridine, contaminated drinking water was the suspected cause. Siebe (1995) reported that the metal concentrations of soils irrigated with untreated municipal wastewater from Mexico City, Mexico increased steadily with the durations of application. Plant uptake of Cd and Pb were increased in proportion to the metal concentrations in the soils. Table 1.4 Frequency of Detection (%) <2% 3 5% 6 9% 10 20% 21 50% 51 99% 100% Frequencies of Detection for Chemical Constituents Found in Sewage Sludge, According to the U.S. Environmental Protection Agency 1986 National Sewage Sludge Survey (U.S. Environmental Protection Agency, 1990) Chemical Acetophene, Anthracene, Azinphos methyl, Benzyl alcohol, α-bhc, δ-bhc, Biphenyl, Chlorobenzene, Chloroform, 2-Chloronaphthalene, DDE, DDT, Di-n-octyl phthlate, Diazinon, Dibensofuran, 1,4-Dichlorobenzene, trans-1,2-dichloroethene, 1,2:3,4-Diepoxybutane, Dimethoate, Dimethyl phthalate, 1,4-Dioxane, I-Endosulfan, 2-Methylnaphthalene, N- nitrosodiphthlene, Naled (Dibrom), Naphathalene, 4-methyl-2-Pantanopne, Phenanthrene, Phosphamidon, Tri-o-tolyl Phosphoric acid, 2-Picoline, Santox (EPN), α-terpineol, Tetraethylpyrophosphate, Trichloroethene, Aldrin, Benz(a)anthraanthene, Ben(a)pyrene, Benz(k)fluoranthene, p-chloroaniline, Chlorpyrifos, Chrysene, Di-n-butyl phthalate, Dieldrin, Ethylbenzene, Heptachlor epoxide, 2- Hexanone, Isobutyl alcohol, Nitrofen (TOK), Pyrene, Styrene, Tetrachloroethene, Tetrachloromethane, Trichlorofluoromethane, Trifluralin (Treflan), m-xylene, o- and p- Xylene Benz(b)fluoranthene, Benzoic acid, β-bhc, Butyl benzyl phthalate, Chlorobenzilate, Cobalt, 0-Cresol, p-cymene, n-docosane, Endrin, Fluoranthene, n-octadecane 2,4-dichlorophenoxy acetic acid, Carbon disulfide, n-decane, n-dodecane, n-eicosane, II- Endosulfan, n-hexacosane, n-hexadecane, n-octacosane, PCBs, Pentachloronitrobenzene, 2,4,5-trichlorophenoxy propionic acid, n-tetracosane, n-tetradecane, Thallium, n-triacontane Antimony, Beryllium, Boron, 2-Butanone, p-cresol, Cyanides (soluble salts and complexes), Hexanoic acid, Methylene chloride, Phenol, 2,4,5-trichlorophenoxy acetic acid Bis(2-ethylhexyl)phthalate, Fluoride, Nitrate, Nitrite, 2-Propanone, Silver, Tin, Titanium, Toluene, Vanadium, Yttrium Aluminum, Barium, Calcium, Dioxins, Iron, Magnesium, Manganese, Sodium, Cadmium, Copper, Chromium, Nickel, Lead, Zinc Issues in Land Applications For over 150 years, sewage treatment has been the backbone of the communitywide environmental sanitation practice. It effectively controlled the epidemics of waterborne diseases. The infrastructure of wastewater collection, treatment and disposal provides consistent and predictable performances and adequate technical redundancy to 9