A new development for the treatment of domestic wastewater is a technology based on aerobic granular sludge. Granular sludge can be developed under specific process conditions and, because of its unique properties, high volumetric loading rates of aeration tanks can be applied. Thanks to excellent settling properties, the separation of treated wastewater and granular sludge can take place at high hydraulic loading rates. Depending on the process configuration chosen, good effluent quality can be obtained, complying with stringent effluent requirements regarding nitrogen and phosphorus, which can be expected in the future. In this way, aerobic granular sludge has the potential to contribute significantly to wastewater treatment management.This report describes the results of research carried out at the Technical University of Delft.IWA Publishing Water and Wastewater Practitioner Series: STOWA Report

This highly technical work is at the leading edge of spatial analysis. It covers the Global Monitoring for Environment and Security (GMES) initiative in the international context of access to environmental data. This book identifies the data policy issues, such as intellectual property rights, privacy, licensing and archiving policies, that affect environmental monitoring organisations, statistical institutes, mapping agencies, institutes for natural resources and Earth observation. It recommends courses of action to improve information services in GMES and assesses the impact of data policy on access to and cost-efficient use of information services in GMES.

This title will be essential reading for government institutions such as mapping organisations, space agencies, environmental departments, military and defence departments; it will also be useful to students of environmental policies and industries involved in mapping, cartography, aerial surveys and the space industry.

The ability to measure sludge network strength is important in sludge dewatering applications because it can be used to determine optimum polymer dose for conditioning to achieve good dewaterability. This was demonstrated in laboratory and in full-scale dewatering and thickening. The network strength increased as the polymer dose was increased, however, at the optimum dose a "drop" in the network strength occurred. Further research is needed to verify this concept at full scale and to provide a robust technology to the water and wastewater treatment industry. A second phase is sought through WERF funding. Rheometry was used for determining the sludge network strength. This report also formulated and demonstrated a standard protocol for measuring network strength in terms of energy dissipated in a certain volume of sludge. Two protocols for measuring network strengths by either torque or concentric cylinder rheometers are described in this report. A mathematical derivation has shown that area under rheograms, namely the curves which were developed by plotting shear rate (1/sec) versus shear stress (Pa) and time (sec) versus torque (mNm), indicated the rate of energy dissipation within the sludge system and the total dissipated energy was related to the network strength. The research did not intend to measure the "absolute" network strength, rather a comparative strength of different aggregates using the same instrument and under the same measuring conditions.

Contamination of aqueous environments by hazardous chemical compounds is the direct cause of the decline of safe clean water supply throughout the globe. The use of unconventional water sources such as treated wastewater will be a new norm. Emerging nanotechnological innovations have great potential for wastewater remediation processes. Applications that use smart nanomaterials of inorganic and organic origin improve treatment efficiency and lower energy requirements. This book describes the synthesis, fabrication, and application of advanced nanomaterials in water treatment processes; their adsorption, transformation into low toxic forms, or degradation phenomena, and the adsorption and separation of hazardous dyes, organic pollutants, heavy metals and metalloids from aqueous solutions. It explains the use of different categories of nanomaterials for various pollutants and enhances understanding of nanotechnology-based water remediation to make it less toxic and reusable.

With contributions from an international team of experts, this book offers planners, engineers, and designers guidelines for using recycled water in landscape and agricultural applications. The book thoroughly covers all of the relevant technical, economic, financial, agronomic, health, environmental, regulatory, and social issues. It covers how to develop, implement, and operate wastewater reuse systems based on rigorous, best management practices that maximize efficiency, reliability, and economy while minimizing the potential for adverse effects to the environment and human health. Comprehensive tables, charts, figures, photographs, and case-studies make the information easy to find. Lazarova; Valentina Suez Environment Services Locaux, CIRSEE, Le Pecq, France,Akissa; Bahri INRGREE, Ariana, Tunisia

Mathematical modeling is a useful tool for the design, analysis and control of wastewater treatment systems. The activated sludge process is one of the most common processes used in wastewater treatment, and therefore is a particularly important candidate for the application of mathematical models. In the 1980s, a task group organized by the International Association on Water Quality (IAWQ) developed a conceptual model of the activated sludge process, which has become an industry-wide standard for the development of computer-based activated sludge models. A recent version of the IAWQ model incorporates 19 components, 17 processes, and numerous rate and stoichiometric coefficients. It is difficult and costly to quantify all of the necessary coefficients for any given application of the model; consequently, it is important to identify the most critical wastewater and biomass components and the relevant coefficients to be quantified for the most common uses of the model. It is also important to provide guidance to potential model users on the use of default and/or estimated values for the remaining parameters.

Uncontrolled spreading of waste materials leads to health problems and environmental damage. To prevent these problems a waste management infrastructure has been set to collect and dispose of the waste, based on a hierarchy of three principles: waste prevention, recycling/reuse, and final disposal. Final disposal is the least desirable as it causes massive emissions, to the atmosphere, water bodies and the subsoil. The emission of methane to the atmosphere is an important source of greenhouse gasses. Organic waste therefore gets a lot of attention in waste management, which for Europe can be illustrated by the issue of the Landfill Directive (99/31/EC) and the Sewage Sludge Directive (86/278/EEC). Proper treatment of organic waste may however turn this burden into an asset. In particular, biological treatment may help in developing more effective resource management and sustainable development. The following advantages may be listed: The greenhouse effect is tackled as methane emissions from landfilling are prevented Soil quality can be restored or enhanced by the use of compost in agriculture Compost may replace peat in horticulture and home gardening, reducing greenhouse emissions and wetland exploitation Anaerobic digestion has the additional benefit of producing biogas that may be used as a fuel Pesticide use can be reduced by proper use of the disease suppressive properties of compost Resource Recovery and Reuse in Organic Solid Waste Management disseminates at advanced scientific level the potential of environmental biotechnology for the recovery and reuse of products from solid waste. Several options to recover energy out of organic solid waste from domestic, agricultural and industrial origin are presented and discussed and existing economically feasible treatment systems that produce energy out of solid waste and recover useful by-products in the form of fertiliser or soil conditioner are demonstrated. The potential of environmental biotechnology is highlighted from different perspectives: societal, technological and practical.

This project was undertaken in response to needs by the wastewater treatment industry to better understand the generation of odors from biosolids produced by wastewater treatment plants (WWTPs). Its primary objective is to begin to establish relationships between WWTP process parameters and biosolids odors, so that more effective techniques for minimizing biosolids odors can be developed. The project consisted of a detailed field study involving extensive sampling and analyses at 11 WWTPs across North America with capacities from 13 to 350 million gallons per day (mgd). Biosolids samples were collected from the WWTPs at a number of sampling points, which were chosen to represent a complete snapshot of biosolids generation and handling at each WWTP. The sampling points started with influent wastewater, proceeded through primary and secondary clarification, and continued through digestion, dewatering, and onsite storage of dewatered biosolids cake. Laboratory-scale anaerobic storage tests were conducted to simulate odor development of biosolids in storage, prior to their beneficial reuse or disposal. A battery of analyses were performed on the biosolids samples by the participating utility laboratories, commercial laboratories, and specialized university laboratories. The analytical data were evaluated and compared with process and operation parameters at each participating WWTP.

The objective of this project was to develop and evaluate a practical technique to indicate the probability of the presence of bacterial pathogens in receiving waters. A "practical" method was defined as one that would limit the use of defined culture-based microbiological methods, and would be based on: (1) validating indicator organisms that predicted the presence of pathogens, or (2) detection of pathogens by polymerase chain reaction (PCR)-based assays. The study also assessed the utility of PCR-based technology for bacterial pathogen detection with respect to technology transfer to a wider range of water and wastewater facilities.

This collection of papers explains how knowledge and capacity development can contribute to improved, effective water management with a digest of lessons learned in the areas of development of tools and techniques, field applications and evaluation. The authors are prominent practitioners, capacity builders and academics within the water and capacity development sectors. Capacity Development for Improved Water Management starts with an introduction and overview of progress and challenges in knowledge and capacity development in the water sector. The next part presents tools and techniques that are being used in knowledge and capacity development in response to the prevailing challenges in the water sector, and a review of experience with capacity change in other sectors. In the third part a number of cases are presented that cover knowledge and capacity development experiences in the water resources and water services sectors. This part also presents experiences on water education for children and on developing gender equity. The fourth part provides experiences with the monitoring and evaluation of knowledge and capacity building.

These proceedings present state-of-the-art papers on mine and mill tailings and mine waste as well as current and future issues facing the mining and environmental communities. This includes matters dealing with technical capabilities and developments, regulations, and environmental concerns. Papers include topics related to site characterization and monitoring, reclamation and remediation, protective liners, covers, and barriers, design, operation and disposal, groundwater and surface water quality and modeling, geotechnical and geochemical aspects, reprocessing, utilization and treatment, radioactivity and risk, new technologies and paste technology, and case histories.

Cyanide occurs in many industrial and municipal wastewaters and is often an expected constituent of typical treatment plant wastewater streams. However, a growing number of wastewater treatment plants (WWTPs) across the USA have detected cyanide in cholorinated effluents at levels exceeding influent concentrations. Because water quality criteria and related discharge limits are typically low some of these WWTPs periodically exceed effluent cyanide standards. Potential causes include cyanide formation during wastewater cholrination processes, the presence of interferences that cause false negatives, and false positives caused by artifacts of sample handling or analytical techniques. The possible causes of the apparent cyanide formation phenomenon were investigated in this study. This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

A general review of literature published from 1990 to 2000 and unpublished (gray) literature on odors associated with municipal wastewater collection systems and treatment facilities, including biosolids handling. The literature review focused on several areas including odor characterization technology, odor sampling, analysis, measurement technology, and odor mitigation (control) technology.

Anaerobic/aerobic (AnA) and completely aerobic (CA) laboratory-scale sequencing batch reactors operating on an acetate- and casamino acids-based synthetic wastewater were used to investigate the suitability of the AnA process for treating nutrient?deficient wastewaters in plants that have stringent effluent nutrient requirements. Of particular interest is the case where phosphorus (P)-deficient wastewaters with highly variable influent COD loading are being treated to meet both effluent TSS and P limits. At a 4 d mean cell residence time, AnA activated sludge had an approx. 20% lower P requirement than CA activated sludge. The difference between the end-of-aerobic cycle polyhydroxyalkanoate and carbohydrate contents of the sludges indicated that the AnAsludge used more influent carbon than the CA sludge for synthesis of non-P-containing storage products. The nitrogen requirements of AnA sludge were similar to those of the CA sludge. The AnA and CA SBRs were subjected to three different transient influent COD loading patterns that simulated (#1) daily COD Loading fluctuations, (#2) low weekend COD loading, and (#3) extended low COD loading periods. During the Loading Pattern #1 experiment, the average effluent soluble P concentrations for the AnA and CA SBRs were 0.4 and 1.0 mgP/L respectively, and complete removal of influent acetate was observed. During the Loading Pattern #2 experiment, the average effluent soluble P concentrations for the AnA and CA SBRs were 0.3 and 0.9 mgP/L respectively, but effluent acetate was detected during the first high COD loading cycle following the low weekend COD loading period. During the Loading Pattern #3 experiment, the VSS content of both reactors dropped sharply, effluent acetate breakthrough occurred, and effluent P concentrations exceeding 1 mgP/L were detected in both the AnA and CA SBRs. Based on these findings, the AnA process has potential as a technologically and economically superior alternative for wastewater treatment plants treating P-deficient wastewasters to meet stringent effluent TSS and P limits. This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

The purpose of this research was to evaluate and compare various thermophilic anaerobic digestion processes for meeting U.S. EPA biosolids Class A pathogen standards. The project was split into three phases. Phase 1 screened three bench-scale thermophilic anaerobic process configurations at three different thermophilic temperatures based on their fecal coliform destruction efficiency. All three of the thermophilic process configurations tested were capable of achieving the Class A fecal coliform standard and were included in Phase 2. In Phase 2, bench-scale anaerobic digesters were fed primary sludge seeded with E.coli, helminth ova, poliovirus, and Salmonella to evaluate pathogen destruction. Two process configurations, the thermophilic single-stage and the two-stage mesophilic acid-phase/thermophilic methane-phase system, met Class A requirements at 50oC. In Phase 3, the single-stage thermophilic anaerobic digestion process was compared to the single-stage mesophilic process at full scale (1.5-MG digesters) based on fecal coliform and pathogen destruction, process performance, digested sludge dewaterability, and odor generation.Pathogen destruction and process performance comparisons of the various process configurations are presented for each phase of the study. Based on the fecal coliform data presented here, an empirical model was developed for quantitatively comparing multiple stage and single-stage thermophilic anaerobic digester performance. The model demonstrates that various combinations of thermophilic temperatures, staging, and residence times can achieve the Class A fecal coliform requirement. This study also suggests that anaerobic digesters operating in the lower thermophilic temperature range (approximately 50degreeC) are not only capable of achieving Class A requirements but may also produce digested sludges with less odor and lower volatile solids than digesters operating at higher thermophilic temperatures.

This research attempts to evaluate nitrification treatment performance in combined carbon/nitrogen municipal wastewater reactors using traditional physical/chemical methods and modern molecular techniques. Bench scale activated sludge reactors were operated at different SRTs under varying DO levels and temperatures over a 21-month period. Real-time PCR assays were used to determine cell concentrations of total bacterial 16S rDNA, a gross measure of biomass content, the amoA gene, a measure of ammonia-oxidizing bacteria (AOB), and the Nitrospira 16S rDNA gene, a measure of nitrite-oxidizing bacteria (NOB). As expected, gravimetric biomass and total bacterial 16S rDNA levels increased with increasing SRT. Ammonia oxidation rates and N. oligotropha-type AOB concentrations did not follow similar trends with respect to changes in SRT, temperature, and DO nor were they highly correlated. The concentration of available nitrite and SRT were positively correlated with Nitrospira cell densities, while DO concentration and temperature were negatively correlated with NOB levels. The percentage of the total population comprised of AOB and NOB obtained with the real-time PCR assays were compared to predicted values estimated from design equations using typical kinetic parameters. While the percentages of NOB measured using the real-time PCR assay corresponded very well with the predicted values, the measured percentages of AOB were much lower than those estimated from the design equations, suggesting that N. oligotropha-type AOB were not the dominant ammonia-oxidizing species in these reactors. This publication can be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

Disinfection of wastewater is a necessary treatment process for protecting the public from potential exposure to pathogenic microorganisms because many wastewater effluents are discharged into water bodies that may be used for recreation or as future drinking water supplies. Two common forms of disinfection are chlorine and ultraviolet (UV) light. However, microorganisms differ in their susceptibility to UV and chlorine disinfectants. It is necessary to understand how different classes of pathogens respond to UV and chlorine disinfection processes in wastewater to better develop strategies for optimizing the treatment of pathogens in wastewater. It is also recognized that water quality may impact disinfection effectiveness, such as protection of pathogen by particles and disinfectant demand. This study investigated bacteria, viruses and protozoan pathogens. All species of bacteria tested were susceptible to both UV and chlorine, despite differences in antibiotic resistance and tendency to aggregate. Upon exposure to disinfection conditions that could indicate viability of the bacteria tested, but not culturability using common methods, it was found that UV and chlorine were effective in eliminating the capability of viable but non-culturable bacteria to resuscitate and become re-infective. Clostridium spores were resistant to free chlorine and UV disinfection but found to be susceptible to long exposure to monochloramine. Cryptosporidium was resistant to all chlorine forms but very susceptible to UV irradiation. Pathogenic and indicator viruses tested were very susceptible to free chlorine and UV disinfection. UV radiation throughout the 200 to 300 nm range was effective for inactivation of viruses and C. parvum, but wavelengths between 260-270 nm and below 220 nm appeared to be more effective for viruses, suggesting a possible advantage for polychromatic UV sources. Sequential disinfection strategies were proposed and tested to enhance inactivation of various microorganisms. One scenario integrated UV disinfection followed by dynamic chloramination through addition of free chlorine and subsequent transformation to combined chlorine. Further, disinfection of microorganisms in wastewater presents challenges that are inherent to the water matrix, such as pathogens associated with particles. UV and chlorine were both effective for disinfection of coliform in wastewater but chlorine was found to be more effective during long contact times for inactivation of particle associated coliform. In addition to coliform, both Cryptosporidium parvum and Salmonella typhimurium were identified as being particle associated in wastewater using molecular approaches developed to detect microbes in environmental samples

This report presents the results of an evaluation of technologies that may result in less biomass production in activated sludge processes. The report summarizes the results of a comprehensive literature review that was done to evaluate technologies in terms of their sludge reduction potential, ease of implementation, impacts on plant operations and effluent quality, reliability, and relative capital and operating costs. Reporting testing results supported significant biomass reduction by processes using chemical and thermal methods, higher life forms (predator processes), anaerobic instead of aerobic respiration, and extreme solids retention times, but biomass reduction for enhanced biological phosphorus removal (EBPR) processes and a mechanical disintegration process were less conclusive. The predator enhancement process showed promise for industrial wastewater treatment, but is less attractive for municipal wastewater treatment for which a lower soluble COD fraction is present. Extreme solids retention time processes may be practical for small wastewater flows and perhaps with the use of membrane separation technology. Anaerobic treatment processes are known to have a lower biomass yield (one fourth or a less than for aerobic treatment), but work is needed to develop their applications for low strength, low temperature wastewaters, such as in municipal wastewater treatment. For some processes such as the cell disruption using mechanical, thermal, and chemical means, the cost of implementing the biomass reduction technology was greater than the cost savings associated with less sludge production. Addition of chemical uncouplers can greatly reduce biomass production, but pose problems of toxic chemicals in the treated effluent. In a series of bench-scale tests carried out at the Seattle West Point wastewater treatment facility and the University of Washington environmental engineering laboratories the presence and mechanism of COD loss (and subsequent less biomass production) in the anaerobic zone of EBPR processes was investigated. The results of the test work and fundamental evaluation could not support previous claims of a COD loss in EBPR processes, nor was less sludge production observed.

Biological wastewater treatment plants can be adversely affected by influent toxicity. The effects can range from poor clarifier biomass settling and elevated effluent BOD and ammonia levels to total plant kills. These problems could be minimized or eliminated if an effective method existed for continuously monitoring biological wastewater treatment plant influent for toxicity to the treatment plant microorganisms. Current influent screening methods have not been proven to be adequate for adaptation to continuous screening in the field. The primary reasons include the batch-wise nature of the assays and an inadequate correlation between the assays and plant performance. The goal of the research team was to create new bioluminescent biosensors from different types of bacteria found in biological wastewater treatment plants for the development of a multi-channel continuous monitoring system. A system built from multiple biosensors would make it possible to differentiate between potential influent toxicity effects to different classes of bacteria (such as nitrifying and heterotrophic bacteria). The research team found it unexpectedly challenging to apply common microbiological transformation methods for laboratory strains to the wastewater treatment plant strains. The research team generated six new bioluminescent bioreporters from bacteria that are typical constituents of activated sludge. Of particular significance is a bioreporter developed using a Hyphomicrobium sp., which is a slow growing bacterium known to be present in significant numbers in some activated sludge plants. Of the six generated, initial bioluminescence and toxicity screening indicated that one strain (a Pseudomonad) was a particularly promising candidate due to its ease of cultivation and high light production. Further toxicity testing, however, determined that the response of the strain to 48 organic compounds and 8 metals commonly found in wastewater was similar to that of a previously created strain, Shk1 (also a Pseudomonad). Further work is therefore needed in the generation of appropriate biosensors and test conditions for populations not represented by the new heterotrophic biosensor.

Utilities must decide whether to modify their existing treatment practices to achieve compliance with the D/DBP regulations. A regulatory impact analysis predicted that up to 70% of large surface-water systems would need to make some treatment modifications. Meeting multiple water-quality objectives plays an important role in the decision-making process of water utilities. Utilities must meet other regulatory requirements and secondary drinking-water standards. In addition, there are operational, financial, and engineering issues that affect the selection of treatment technologies. Because of the uncertainty of how stringent certain regulations will be and the high costs of advanced treatment technologies, many utilities have implemented treatment modifications in stages. Most utilities have made treatment modifications that have been cost-effective to meet their site-specific needs and objectives, while continuing to study or implement long-term treatment changes to meet more stringent future regulations. Utilities must factor in other regulatory requirements and secondary drinking-water standards when selecting a treatment modification for compliance with the D/DBP Rule. Some utilities chose advanced treatment processes (e.g., ozonation, membranes) that would enable them to satisfy other current and anticipated future regulations or other water quality objectives. Some systems chose ozone, in part because of its ability to destroy taste-and-odor-causing contaminants. Likewise, granular activated carbon was added to filters for taste-and-odor control. In addition, space and retrofit considerations affected technology choices. Many utilities have implemented treatment modifications in stages. To meet Stage 1 of the D/DBP Rule, most utilities have made treatment modifications that have been cost-effective to meet their site-specific needs and objectives, while continuing to study or implement long-term treatment changes to meet more stringent future regulations. The major disadvantage to staged implementation was that the treatment process was re-optimized each time treatment modifications were made. However, this problem was minimized if the full range of changes in treatment was envisioned in advance and if incremental modifications were made that were part of and consistent with long-term modifications. Originally published by AwwaRF for its subscribers in 2003 This publication can be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

This research focused on the use of sonication to destroy surfactants and surface tension properties in industrial wastewaters that affect traditional water treatment processes. We have investigated the sonochemical destruction of surfactants and a chelating agent to understand the release of metals from surfactants during sonication. In addition, the effects of physical properties of surfactants and the effect of ultrasonic frequency were investigated to gain an understanding of the factors affecting degradation. Successful partial or total destruction of surfactants resulting in the release of metals bound to surfactants may result in a significant cost savings of treatment plants. Sonochemical degradation of surfactants was observed to be more effective than nonsurfactant compounds. In addition, as the concentration is increased the degradation rate constant does not decrease as significantly as with nonsurfactant compounds in the NAP reactor. In fact, the total number of molecules degraded increases with concentration. The degradation of metal complexes is not as effective as in the absence of the metal. However, this is likely an artifact of the model complexing agent used at the hot bubble interface, significantly increasing ligand exchange kinetics and thus degradation of the complex. This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

Narrative water quality criteria are an integral component of States' water quality standards but they pose special problems when incorporated into the TMDL process. The TMDL process is typically a quantitative activity, defining numeric allowable loads necessary to meet a numeric water quality objective. Narrative criteria confound development of quantitative TMDLs, due to the absence of these numeric criteria. The objective of this research was to improve the methods for addressing narrative water quality criteria in the TMDL process. The problems associated with narrative criteria in the TMDL process are known in general terms but, prior to this research, there has not been a thorough review of the use of narrative criteria in TMDLs nor broad guidance on how to address narrative criteria in the TMDL process. The approach taken for this research was to define the range of problems associated with all types of narrative criteria by means of a comprehensive review of 120 narrative TMDLs, and provide guiding principles to help address these problems.Adherence to these guiding principles is expected to significantly improve the evaluation of water bodies for impairment of a designated use based on non-attainment of narrative water quality criteria, resulting in more accurate 303(d) lists with a greater focus on those water bodies truly impaired. Also, adherence to these guiding principles will contribute to improvements in the TMDL development process, resulting in a greater degree of success in attaining designated uses when a TMDL is implemented . This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

Thermal enrichment of coldwater streams by heated stormwater in summer months is often overlooked and even exacerbated by traditional management practices that typically account for flow moderation and pollutant removal only. Initiated in 1999, this study evaluated and identified innovative and traditional approaches to moderate this temperature impact by monitoring and analyzing the hydrologic and thermal regimes of an urban stormwater treatment system consisting of two traditional wet detention ponds and an enhanced natural wetland. Data analysis clearly shows temperature increases in the open detention ponds and the ability of the wetland to mitigate this thermal enrichment. Event-based thermal loading and temperature regime analysis indicated flow reduction via infiltration and effective vegetative cover in the wetland were the primary mechanisms for mitigating stormwater thermal enrichment. Using the concept of temperature equivalent, we also established the locations and strength of thermal enrichment areas. A heat transfer model was developed to simulate runoff temperature. Results indicated that rainfall characteristics, temperature difference between rainfall and the ground surface, and the runoff flow depth were the most important factors affecting runoff temperature.

This investigation reviewed and evaluated methodologies used for microbial risk assessment with respect to their applicability for reclaimed water applications. The investigation was comprised of five primary components: a comprehensive database of articles, reports and books describing microbial risk assessment methodologies was established and reviewed. Risk assessment techniques and models were identified for estimating the public health risk from exposure to microorganisms via reclaimed water applications. Two models were identified for further evaluation: a static (individual based) and a dynamic (population based). In the third component, the two models were evaluated to differentiate between the conditions under which models predict similar and substantially different estimations of risk. Through numerical simulation, exposure/pathogen combinations were identified when it may be appropriate to use the less complex, static model. Case study risk assessment scenarios demonstrated the model selection process for three realistic, yet hypothetical reclaimed water scenarios.The fourth component presents a constraint analysis for existing reuse regulations. The constraint analysis is carried out by documenting the existing reuse regulations. The constraint analysis is carried out by documenting the existing regs in three states for landscape irrigation and uses that comparison as a starting point to identify how microbial risk assessment may be useful within the context of existing and potential future water reuse regulations. The investigation concludes by identifying criteria for a computer interface that would allow regulatory and/or municipal agencies/utilities to take advantage of the analysis discussed in the report. This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

TMDLs, or total maximum daily loads, are required under the Clean Water Act, Section 303(d), for waterbodies that do not attain water quality standards. The objective of this research was to review the existing TMDL process and to develop an improved design for TMDL development where improvements are needed. This objective was accomplished through: (1) Identifying and verifying problems with the existing TMDL program; (2) Formulating a range of recommended improvement options on specific topics that address identified weaknesses; and (3) Providing case studies examples that highlight these recommended changes to improve the TMDL process. The research team identified ten specific areas for improvement, based on a review of approved TMDLs, a survey of state programs, and an in-depth review of specific case study examples. These topics relate to specific steps and/or methods employed in the TMDL development process. They include: estimating background pollutant loads; quantifying nonpoint source loads using simple methods; incorporating urban wet weather sources; selecting critical conditions; guiding principles for modeling; estimating the TMDL margin of safety; approaches to the allocation of loads; linking best management practices to load reduction; implementation planning, tracking, and adaptation; and adaptive watershed management. Each topic is addressed in a separate chapter of the report, with a discussion, recommendation of improved approaches where appropriate, and specific examples to help guide water quality professionals when developing or reviewing TMDLs.