Municipal Wastewater Management in Developing Countries discusses various approaches to municipal wastewater management in order to protect both public health and the environment, with the major focus being on waterborne diseases. Developing countries can be divided into two main categories, i.e. countries in transition with higher growth rates where industrialisation and urbanisation are taking place rapidly, and countries with slower growth rates. It is important, therefore, that approaches should be tailor-made and site-specific. In general, the major trends of water pollution control have significantly contributed to the development of ?conventional sanitation? approaches in terms of legal and financial frameworks, as well as technological enhancement. Despite advances in the science, engineering and legal frameworks, 95 per cent of the wastewater in the world is released into the environment without treatment. Only five per cent of global wastewater is properly treated using the ?standard? sanitation facilities, mainly in developed countries. As a result, the majority of the world?s population is still exposed to waterborne diseases, and the quality of water resources has been rapidly degraded, particularly in poor developing countries. The challenge now is to provide the world?s population, especially the poor, with adequate water and sanitation facilities. Despite billions of dollars of investment spent every year, billions of poor people are still suffering and dying because of poor sanitation. At the beginning of this century, about 1.1 billion people lived without access to clean water (compared to about the same number in 1990), 2.4 billion without appropriate sanitation (compared to 2.3 billion in 1990) and four billion without sound wastewater disposal. The future scenario, that water resources will be further depleted by a growing world population, will be coupled with environmental degradation due to poor pollution control, particularly in most of the developing countries. In order to address the issue of water and wastewater management in developing countries it is necessary to take into consideration the segments of the society itself, particularly the types of housing areas. The segments will indicate the level of socio-economic, mentality and knowledge, which is important for any planned changes in their life style and social engineering. It is also important to segregate the funding framework of any proposed projects. High-income urban communities, for instance, are generally willing to pay for sewerage services and higher water supply tariffs, therefore a designated system can be accordingly provided. Over the past 10 years, serious criticism has been given to the ?conventional sanitation? approach, consequently many definitions, concepts and characteristics have been proposed on ?sustainable sanitation?. Sustainable sanitation is a relevant concept in order to achieve the Millennium Development Goals by 2015 of providing water supply and adequate sanitation for developing countries. Sustainable sanitation is flexible in approach any community ? poor or rich, urban or rural, water-rich or water-poor country ? and requires lower investment costs compared to conventional sanitation approaches. It is also important to note that the framework of sustainable sanitation is much easier to adopt in developing countries where water supply and sanitation infrastructures are still in the developing stages. In some developing countries, no public facilities are available therefore it is an ideal condition to start a new infrastructure with a new framework. This comprehensive reference, prepared by leading international authorities, will provide an invaluable reference for all those concerned with the management of sanitation services in developing countries worldwide.

Handbook of Nanomaterials for Wastewater Treatment: Fundamentals and Scale up Issues provides coverage of the nanomaterials used for wastewater treatment, covering photocatalytic nanocomposite materials, nanomaterials used as adsorbents, water remediation processes, and their current status and challenges. The book explores the major applications of nanomaterials for effective catalysis and adsorption, also providing in-depth information on the properties and application of new advanced nanomaterials for wastewater treatment processes. This is an important reference source for researchers who need to solve basic and advanced problems relating to the use of nanomaterials for the development of wastewater treatment processes and technologies. As nanotechnology has the potential to substantially improve current water and wastewater treatment processes, the synthesis methods and physiochemical properties of nanomaterials and noble metal nanoparticles make their performance and mechanisms efficient for the treatment of various pollutants.

This is the second of two volumes that together provide a comprehensive overview of the current sustainable and low-cost wastewater treatment technologies applied in communities that lack the financial and technical resources needed for an environmental, disease prevention and health nexus. This book reviews engineered wastewater treatment technologies and discusses their application in regard to greenhouse gas emissions, natural resource utilization, land-use, and energy and water savings. The chapters from expert contributors cover topics such as aerobic and anaerobic biological treatments, chemical treatments and precipitation, and disinfection. Readers will also learn about simplified and low-energy wastewater treatment plants, strategies for wastewater reuse, and nanotechnologies for wastewater environmental management. The feasibility regarding time and cost of implementing such technologies is also discussed in this book, and particular attention is given to the removal of conventional and emerging pollutants, toxicants, and heavy metals. Given the breadth and depth of its coverage, the book offers an invaluable source of information for researchers, students and environmental managers alike.

The Activated Sludge (AS) Process is old technology but is still widely adopted worldwide for its convenience and simplicity: an impressive number (many hundred of thousands) of this kind of system are in operation. Occasionally, problems such as bulking and foaming occur, causing regulation violations and large investment is often required immediately to control them. For this reason, an intense research effort has been made during the last few decades to face these problems, and this report details the work undertaken by the IWA Specialist Group on Activated Sludge Population Dynamics. This Scientific and Technical Report describes the main reasons fslyuor the growth of the different filamentous microorganisms in activated sludge, and the biological molecular tools available today for the identification of the main biomass components. The wide range of experiences around the world is documented and the methods to avoid the proliferation of these organisms are presented and critically reviewed. Activated Sludge Separation Problems consists of seven chapters, presenting up-to-date technical and scientific aspects of these processes. Scientific and Technical Report No. 16

Wastewater disinfection is practiced with the goal of reducing risks of human exposure to pathogenic microorganisms. Ideally, this goal is to be met without introducing other risks, such as those that could be associated with disinfection by-products. The purpose of this research was to assess the effects of wastewater disinfection on human health. This assessment was conducted by examining two fundamental questions regarding the application of disinfection: 1. Should municipal wastewater effluents be disinfected prior to discharge?; and, 2. Under circumstances where disinfection is necessary, how should it be accomplished? Undisinfected effluent samples from a several municipal wastewater treatment facilities were collected for analysis. The facilities selected for sampling were chosen to represent a broad spectrum of effluent qualities. Facilities were selected to provide a broad spectrum of effluent quality, particularly as related to nitrogenous compounds. Samples were subjected to bench-scale disinfection under conditions that allowed compliance with relevant discharge regulations, and such that disinfectant exposures could be accurately quantified. Disinfectants applied in this research included chlorine and UV radiation. Disinfected samples were subjected to a battery of microbiological assays to assess the immediate and long-term effects of disinfectant exposure on bacteria and viruses.

Instrumentation, control and automation (ICA) in wastewater treatment systems is now an established and recognised area of technology in the profession. There are obvious incentives for ICA, not the least from an economic point of view. Plants are also becoming increasingly complex which necessitates automation and control. Instrumentation, Control and Automation in Wastewater Systems summarizes the state-of-the-art of ICA and its application in wastewater treatment systems and focuses on how leading-edge technology is used for better operation. The book is written for: The practising process engineer and the operator, who wishes to get an updated picture of what is possible to implement in terms of ICA; The process designer, who needs to consider the couplings between design and operation; The researcher or the student, who wishes to get the latest technological overview of an increasingly complex field. There is a clear aim to present a practical ICA approach, based on a technical and economic platform. The economic benefit of different control and operation possibilities is quantified. The more qualitative benefits, such as better process understanding and more challenging work for the operator are also described. Several full-scale experiences of how ICA has improved economy, ease of operation and robustness of plant operation are presented. The book emphasizes both unit process control and plant wide operation. Scientific & Technical Report No. 15

Siting Noxious Facilities explains and illustrates processes and criteria used to site noxious manufacturing and waste management facilities. It proposes a framework that integrates economic location analysis and risk analysis, emphasizing the reduction of uncertainty. This book begins by defining noxious facilities and considers the important role of manufacturing in the world economy, before going on to describe the historical practices used in locating these facilities for much of the twentieth century. It then shifts focus to analyze the complex set of considerations in the twenty-first century that mean that any facility that produces annoying smells and sounds, is unsightly and emits hazardous substances has had the bar of acceptability markedly raised for economic, environmental, social and political acceptability. Drawing on case study examples that highlight pollution prevention, choosing locations at major plants (CLAMP), negotiations, and surrendering control of an activity, Greenberg presents a hybrid framework that advocates the amalgamation of industrial location processes with human health and environmental-oriented risk analysis. This book will be of great interest to students and scholars of location economics, environmental science, risk analysis and land-use planning. It will also be of great relevance to decision-makers and their major advisers who must make choices about siting noxious facilities.

This report deals with whether the experience of odors, i.e., odors as sensations, from biosolids at wastewater treatment plants (WWTPs) causes illness. There exists no repository of information on the numbers of complainants with illness, their specific complaints, or the relationship between degree of exposure and complaints. Anecdotal reports nevertheless imply a pattern much like that associated with other industrial malodors. Any connection between odor and illness has received little note among the millions of articles in the medical literature. This state of affairs presumably exists because odors per se generate no objective signs of illness in otherwise healthy persons. However, malodors may exacerbate both symptoms and signs of illness in persons with certain chronic disorders, such as asthma and migraine. Vulnerability to such effects may vary considerably from person to person.

The presence of cationic pollutant metals in municipal wastewater effluent is a concern because stringent discharge requirements cannot always be met with conventional treatment methods. Attempts to improve metal removal are often unsuccessful because a significant fraction of the cationic metals are complexed by the synthetic chelating agent ethylenediamine tetraacetic acid (EDTA). To identify practical approaches for improving metal removal, an analytical method for measuring metal-EDTA complexes was used to survey metal speciation at a series of wastewater treatment plants. Following these analyses, bench-scale experiments were conducted. The survey data indicated that pollutant metal-EDTA complexes account for a significant fraction of the dissolved metals in wastewater. The bench-scale studies indicated that ferric chloride addition improves the removal of copper and zinc by approximately 20%. To test the results of the bench-scale experiments, a full-scale experiment was conducted by interrupting chemical addition at a municipal wastewater treatment plant that normally adds ferric chloride during primary treatment. Results indicated that ferric chloride addition had a slight impact on metal speciation but no effect on metals removal. The lack of an effect was attributed to changes in metal speciation that occurred during primary treatment irrespective of ferric chloride addition.

Plant-availability of metals in biosolids-treated soils may be mathematically described by M t = C x 1 - e - (k x t) ] where M t (mg kg -1 ) is the cumulative metal removal from the biosolids-treated soils by growing and harvesting plants for t years, C is the total phytoavailable metal pool of the soil (mg kg -1 ) at t = 0, and k is the metal absorption rate coefficient (yr -1 ). The total available metal pool, C, is defined as metals extractable by organic acids in the rhizosphere of growing plants and k is related to the kinetics of metal release by organic acids. Half-life of the available metals in biosolids-amended soils may be derived from k. Experiments were conducted to characterize the concentration and composition of the organic acids. A successive extraction method was used to extract metals from biosolids-treated soils for determinging C and k. In this manner, the plant available metals of the bioslids-treated soils are defined by the total avialble metals, half-life, and duration of plant growing. Examples showed that the total available metals of the biosolids-amended were 18 to 39, 0.12 to 2.0, 7.4 to 13, 24 to 46, 1.2 to 2.1, and 43 to 53% of the total Cd, Cr, Cu, Ni. Pb, and Zn in the soils. This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below

Class A biosolids can be produced using low-cost, low-technology biosolids treatment processes including lagoon storage, air drying, and cake storage. This project reviewed the available literature and municipal agency data about these processes. This report presents design and operating guidelines distilled from the review process. It is designed for wastewater treatment plant (WWTP) managers, operators, and engineers who wish to discern whether these processes, used alone or in combination, might be practically applied at specific plants. This report also describes the U.S. regulatory environment in relation to producing Class A Biosolids and defining Class A processes. It also presents a list of recommended research needs. This report: Familiarizes WWTP managers, operators, and engineers with low-cost, low-technology biosolids treatment processes, likely pathogen kill mechanisms, and practices that have reduced pathogen densities to Class A levels at scales ranging from laboratory tests to large municipal biosolids treatment operations. Presents guidelines for producing Class A biosolids under a variety of conditions. Describes low-technology treatment processes within the Class A regulatory framework, identifies satisfactory end conditions for products created from low-tech treatment processes, and provides guidance in developing national or site-specific certification as processes equivalent to a process to further reduce pathogens (PFRP).

Nitrification kinetics were evaluated in bench-scale batch reactors fed with a synthetic wastewater containing approximately 1,000 mg ammonia-nitrogen (NH3-N)/L operated at 5, 10, and 20 day solids retention times (SRTs) and with dewatered biosolids supernatant (1,126 to 1,680 mg NH3-N/L) operated at a 20-day SRT. For the 5- and 10-day SRTs, complete nitrification appeared to be inhibited by the presence of un-ionized ammonia and un-ionized nitrous acid. For the 20-day SRT, near complete nitrification was observed for both substrates. Observed ammonium oxidation rates decreased with increasing SRT. Observed yield coefficients were similar for all SRTs and substrates. Fully established steady-state conditions were observed at higher SRTs despite process start-up and operational considerations. Although it may be possible to culture a nitrifier population capable of near-complete nitrification at lower SRTs, the design configuration and operational strategy must mitigate the potential for un-ionized ammonia and un-ionized nitrous acid inhibition (e.g. process start-up at lower concentration with gradual increase to higher concentration, continuous feed operation, etc.). Batch bioaugmentation analyses were conducted in the mixed liquor suspended solids and final clarifier effluent from a non-nitrifying activated sludge with seed nitrifiers developed from the 20-day SRT reactors and with biomass from a nitrifying trickling filter facility. Ammonia removal was observed in all bioaugmentation analyses with no apparent lag or acclimation period. Observed ammonium oxidation rates were not significantly different between the seed and batch bioaugmentation reactors. Acclimation does not appear to be a critical obstacle for nitrifier bioaugmentation when environmental conditions (e.g. temperature, pH, etc.) between the seed and bioaugmentation processes are not significantly different.

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

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.

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.

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.

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 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 denitrification by heterotrophic bacteria is common in the wastewater industry in the U.S. and in drinking water processing in Europe. To facilitate heterotrophic denitrification, organic compounds such as methanol, ethanol and acetic acid are added to provide a carbon source for the bacteria. The resulting organic carbon residual may create problems with chlorination. The addition of these carbon compounds is expensive and results in added sludge production. This study focused on the use of autotrophic hydrogen oxidizing bacteria for denitrification. The method transfers hydrogen gas to solution via microporous hollow fiber membranes. Typically, gases are supplied to a system using conventional bubble diffusers. The conventional bubble aeration system has a low gas transfer efficiency, and, as a result, the cost of dissolving the required amount of gas is very high. In this study, microporous hollow fiber membranes were employed to supply hydrogen gas to hydrogen oxidizing autotrophic bacteria. Laboratory scale membrane modules were constructed and mass transfer studies were carried out to develop the design correlations for hydrogen gas transfer. A mixed culture was obtained and acclimated for batch denitrification studies. Both Sodium carbonate and carbon dioxide were used to deliver inorganic carbon. Bench scale continuous flow biofilm reactors containing plastic media were operated to remove nitrate from water. The required hydrogen gas was supplied at a constant rate via gas transfer modules, containing sealed end microporous hollow fiber membranes. The reactors were optimized for removal of nitrate and nitrite by varying the recycle ratios and hydraulic detention time. Experimental results indicated the presence of hydrogen oxidizing denitrifiers in wastewater sludge. Adequate pH control was possible and the pH averaged around 6.95. Gas transfer studies indicated that hydrogen transfer was primarily controlled by liquid film diffusion. Hydrogen gas was successfully delivered to the reactor via the hollow fiber membrane gas transfer module. Nitrate and hydrogen concentration measurements indicated that the system did not experience hydrogen limitations at detention times of 3.25 hours or greater. The use of hollow fiber membrane module appears to be a viable technology for transferring hydrogen gas to water. The research results in this report provide valuable information for pilot and full-scale studies for the water/wastewater community focusing on membrane processes for autotrophic denitrification.

First published in 1978: The purpose of this two-volume series is to present a consolidated and comprehensive reference on oxygen-activated sludge technology.