bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Nonsteady‐State Conditions and Kinetics of Mass Transport for Hydrophobic Compounds in Activated‐Sludge Treatment
Authors: Rittmann Bruce E. , Lee Kuan‐Chun , Shi Jay , McAvoy Drew C.
Published: September 2006

A new model that describes the fate of hydrophobic and volatile organic compounds in activated‐sludge treatment includes two novel features. First, all of the mass balances are nonsteady state, which allows the model to describe the effects of transients in loading, temperature, or operation. Second, the model describes the mass transfer of hydrophobic compounds with kinetics, not equilibrium. A series of examples demonstrate the new features of the model and how they can be important. When the kinetics of mass transfer are not fast, hydrophobic compounds remain significantly out of equilibrium, even when the system is operating at steady state. When the loading of a hydrophobic compound increases, its aqueous‐phase concentration approaches (but does not quite reach) its steady‐state concentration much more rapidly than does the density of the adsorbed hydrophobic compound. Finally, the importance of mass‐transport kinetics between the aqueous and sorbed phases suggests that research should be focused on this poorly understood mechanism in activated sludge.
Detection of Cryptosporidium parvum in Secondary Effluents Using a Most Probable Number–Polymerase Chain Reaction Assay
Authors: Tsuchihashi Ryujiro , Loge Frank J. , Darby Jeannie L.
Published: September 2006

Polymerase chain reaction (PCR) was used to detect Cryptosporidium parvum oocysts in secondary effluent samples collected from activated‐sludge facilities. Serial dilutions of the purified nucleic acid extracts from the samples were made and PCR was conducted to estimate the C. parvum oocyst concentration via a Poisson distribution‐based most probable number (MPN). The degree of oocysts associated with wastewater particles was also evaluated. The sensitivity of the MPN–PCR assay was 20 oocysts/PCR unit. The detection limit of the concentration, extraction, and purification protocols in phosphate buffer saline spiked with a known concentration of oocysts ranged from 1.1 to 4.6 oocysts/L; the detection limit for the wastewater samples ranged from 11 to 4200 oocysts/L depending on the extent of inhibition in each sample. The recovery efficiency of the oocysts ranged from 48 to 59% in most samples. Oocysts were found in two out of seven samples with concentrations of 203 and 308 oocysts/L, as estimated by the MPN–PCR method. The oocysts were found only in the filtrate of the grab samples; particle‐associated oocysts were not detected. Association of spiked C. parvum oocysts with particles in secondary effluent drawn from wastewater plants with varying operating conditions indicated a weak correlation between the degree of association and the mean cell residence time of the system.
Effect of Powdered Activated Carbon on the Performance of an Aerobic Membarane Bioreactor: Comparison between Cross‐Flow and Submerged Membrane Systems
Authors: Kim Jae‐Seok , Lee Chung‐Hak
Published: September 2006

The effects of powdered activated carbon (PAC) on the performance of an aerobic membrane bioreactor were investigated under two different filtration modes: cross‐flow and submerged filtration. Under a cross‐flow microfiltration mode, floe breakage resulting from sludge recirculation caused a rapid decrease in the microbial floe size and the release of colloidal and soluble components including extracellular polymeric substances (EPS). The released components caused rapid loss of membrane permeability by the formation of a dense cake layer on the surface of the membrane. Biological activated carbon (BAC) sludge formed by the addition of PAC released lower amounts of fine colloids and EPS. Although the pattern of floe breakage of the BAC sludge by pumping shear was similar to that of conventional activated sludge, PAC in the BAC microbial floe adsorbed or entrapped some microfloe components into the floe and reduced permeability loss by approximately 35% compared with conventional activated sludge. Under a submerged microfiltration mode, the effect of PAC addition was more pronounced. For the BAC sludge, the increase in transmembrane pressure was more sluggish and, thus, the operating interval could be extended up to 3 times that for the submerged membrane bioreactor with normal activated sludge.
Comparisons of Polymeric and Conventional Coagulants in Arsenic(V) Removal
Authors: Fan Maohong , Brown Robert C. , Sung Shin Wu , Huang Chin‐Pao , Ong Say K. , van Leeuwen J. (Hans)
Published: September 2006

The removal of arsenic(V) from water was investigated under various coagulation conditions and compared to a variety of coagulation agents, including polymeric ferric chloride, polymeric ferric sulfate, polymeric aluminum chloride, polymeric aluminum sulfate, ferric chloride, ferric sulfate, aluminum chloride, and aluminum sulfate. Coagulation conditions evaluated include pH, temperature, type of coagulant, the addition of a coagulation aid, and initial arsenic(V) concentration. Results indicated that the arsenic removal efficiencies of polymeric coagulants were typically 10 to approximately 20% higher than those of their conventional coagulant counterparts.
Incinerator Slag Formation and Control of Excursion Temperatures
Authors: Greenwood Stephen , Geisenhoff Jack
Published: September 2006

An evaluation of slag formation was initiated to reduce incinerator slag. A factorial test was used to determine the effect of polymers, primary/secondary sludge ratio, and dewatering equipment on ash fusion temperatures (ASTM D‐1857). None of the parameters affected the initial deformation or softening temperatures, 1141 and 1181 °C, respectively. Incinerators experience slag formation several hundred degrees lower than the measured ash fusion temperature test results. A new test was developed to determine ash fusion temperature. More than seventy 5‐cm ash cubes were formed and heated in sets to temperatures of 816, 871, 899, 927, 954, 982, 1038, and 1093 °C. The compressive strength of each cube was measured to determine at what temperature fusion begins. A water spray system was built to control excursion temperatures and slag formation. Supplemental water for cooling excursion temperatures requires approximately 4 times less mass than air. Water injected to the incinerator condenses in the wet scrubber; therefore, there is no additional mass load to the incinerator fan. This process study defined the effect of temperature on slag formation.
The Determination of Longitudinal Dispersion Coefficients in Rivers
Authors: Palancar María C. , Aragón José M. , Sánchez Fernando , Gil Roberto
Published: September 2006

The dispersion coefficient of several sections of two Spanish rivers (Tagus and Ebro) is calculated using different methods. The aim of the study is to accurately know the effects of accidental leaks from two nuclear power plants that are placed upstream. Experimental data from tracer injections as well as data from hydraulic parameters were used to calculate the dispersion coefficient. Two methods based on tracer curves fit the experimental data well. One method is based on the time at which the tracer concentration is half the maximum concentration; the other method is based on the variance of the tracer curve distribution. An alternative method based on governmental data of velocity profiles and correlations of hydraulic parameters was also used. The results of this method are strongly sensitive to small variations in the stream flowrate. A new correlation is proposed to predict the dispersion coefficient with an error smaller than the one provided by other correlations in the literature.
The Removal of Chemical Oxygen Demand from Primary‐Treated Domestic Wastewater in Subsurface‐Flow Reed Beds Using Different Substrates
Authors: Manios T. , Stentiford E. I. , Millner P.
Published: September 2006

Subsurface‐flow experimental reed beds were designed and built based on a combination of two design methodologies. Four different growing media were used with a combination of topsoil, gravel, river sand, and mature wastewater biosolids compost to determine the best substrate for chemical oxygen demand removal. Eight units were constructed, two for each material. One bed for each pair was planted with Typha latifolia plants commonly known as cattails. Primary‐treated domestic wastewater was continuously fed to the beds for more than 6 months. The best performance was achieved by the gravel reed beds, with an average removal rate higher than 50%. Soil‐based beds containing topsoil and sand only managed to attain removals of approximately 10%. The reed beds containing compost in their substrate produced the worst treatment, mainly because of leaching of organic substances from the compost. Primarily as a result of channel flow, all beds showed significant deviation from the designed retention time. There was no significant difference in the performance of planted and unplanted reed beds.
A Laboratory Batch Reactor Test for Assessing Nonspeciated Volatile Organic Compound Biodegradation in Activated Sludge
Authors: Cano M. L. , Saterbak A. , van Compernolle R. , Williams M. P. , Huot M. E. , Rhodes I. A. , Allen C. C.
Published: September 2006

The relative rates of biodegradation and stripping and volatilization of nonspeciated volatile organic compounds (VOCs) in wastewater treated with aerobic activated‐sludge processes can be quantified using a newly developed procedure. This method was adapted from the original aerated draft tube reactor test that was developed to measure biodegradation rate constants for specific volatile pollutants of interest. The original batch test has been modified to include solid‐phase microextraction(SPME) fibers for sampling in the gas phase. The experimental procedure using SPME fibers does not require specific identification and quantitation of individual pollutants and can be used to evaluate wastewater with multiple VOCs. To illustrate use of this procedure, laboratory experiments were conducted using biomass and wastewater or effluent from three activated‐sludge treatment systems. Each experiment consisted of two trials: a stripping‐only trial without biomass and a stripping plus biodegradation trial using biomass from the activated‐sludge unit of interest. Data from the two trials were used to quantify the rates of biodegradation by difference. The activated‐sludge systems tested were a laboratory diffused‐air reactor treating refinery wastewater, a full‐scale surface aerated reactor treating a petrochemical wastewater, and a full‐scale diffused‐air reactor treating a variety of industrial effluents. The biodegradation rate constant data from each laboratory batch experiment were used in model calculations to quantify the fraction emitted (fe) and the fraction biodegraded (fbio) for each system. The fe values ranged from a maximum of 0.01 to a maximum of 0.32, whereas fbio values ranged from a minimum of 0.40 to a minimum 0.95. Two of these systems had been previously tested using a more complicated experimental approach, and the current results were in good agreement with previous results. These results indicate that biodegradation rate constant data from this laboratory method can be successfully used to predict the fate of VOCs in field‐scale treatment units, and thus could potentially be used for demonstration of compliance with wastewater VOC emission regulations.
Engineered Bioretention for Removal of Nitrate from Stormwater Runoff
Authors: Kim Hunho , Seagren Eric A. , Davis Allen P.
Published: September 2006

A bioretention unit is a simple, plant‐ and soil‐based, low‐impact treatment and infiltration facility for treating stormwater runoff in developed areas. Nitrate, however, is not attenuated in conventional bioretention facilities. Thus, this study systematically evaluated a reengineered concept of bioretention for nitrate removal via microbial denitrification, which incorporates a continuously submerged anoxic zone with an overdrain. Experimental studies were performed in four phases. In the first two phases, column studies demonstrated that, overall, newspaper is the best solid‐phase electron‐donor substrate for denitrification out of the set studied (alfalfa, leaf mulch compost, newspaper, sawdust, wheat straw, wood chips, and elemental sulfur) based on superior nitrate removal and effluent water quality. The nitrate loading and hydraulic loading studies in the second phase provided design information. In the third phase, system viability after 30‐ and 84‐day dormant periods was evaluated in column studies, demonstrating that newspaper‐supported biological denitrification should be effective under conditions of intermittent loadings. Finally, in the fourth phase, pilot‐scale bioretention studies demonstrated the effectiveness of the proposed design, showing nitrate plus nitrite mass removals of up to 80%. These results indicate that engineered bioretention for the removal of nitrogen from stormwater runoff has the potential for successful application as an urbanstormwater treatment practice.
Survival of Indicator Organisms during Enrichment on Tetrachloroethene
Authors: Skramstad J. D. , Hurst C. J. , Novak P. J.
Published: September 2006

A laboratory study was performed as the basis for a full‐scale bioaugmentation project at a site contaminated with chlorinated ethenes. The objectives of this study were to 1) develop a protocol to enrich for a tetrachloroethene (PCE)‐dechlorinating culture from waste activated sludge and anaerobic digester biosolids and 2) monitor the survival of fecal coliform bacteria and bacteriophage, which model enteric viruses, during the enrichment process. A culture was enriched in 8 days with the ability to degrade 6‐μM PCE to cis‐dichloroethene. Using the enrichment protocol in two identical experiments, significant inactivation of fecal coliform bacteria (2 log) and somatic coliphage (0.33 log) was observed in one of the experiments; no inactivation occurred in the second experiment. The number of F‐specific coliphage decreased in both experiments (0.87 and 1.26 log inactivation). Despite the decrease in some of the coliform and bacteriophage numbers, the quantity of organisms and phage particles present after enrichment was still high (∼7.5 × 105 most probable number/L, 6.9 × 106 plaque‐forming units (PFU)/L, and 3.3 × 105 PFU/L, for fecal coliform bacteria, somatic coliphage, and F‐specific coliphage, respectively). This may be cause for concern, depending on the current and future groundwater use at or near a site undergoing bioaugmentation with cultures derived from waste activated sludge and anaerobic digester biosolids.
Relationship Between the Van Kleeck and Mass‐Balance Calculation of Volatile Solids Loss
Authors: Switzenbaum Michael S. , Farrell Joseph B. , Pincince Albert B.
Published: September 2006

An equation was developed that quantifies the relationship between volatile solids reduction (VSR) calculated by the Van Kleeck and mass‐balance equations. Two sets of data were used to illustrate the significance of fixed‐solids loss on the agreement between the two methods. The Van Kleeck equation assumes that fixed solids are conserved during the digestion process; however, this assumption is not needed for the mass‐balance equation. Therefore, if substantial changes in the fixed‐solids concentration occur, the Van Kleeck equation will not be as accurate as the mass‐balance equation for computing VSR and will also underestimate VSR.
Comparison of Dalmatian Water Evaluation Indices
Authors: Ŝtambuk‐Giljanović Nives
Published: September 2006

Water quality in the Dalmatian waters of Southern Croatia was assessed using four different indices: an arithmetic index, arithmetic modified index, geometric modified index, and Solway‐modified index. The waters were sampled 12 times during 1 year (from July 1998 to July 1999) at 50 sampling sites in Dalmatia. Nine water quality parameters were evaluated: temperature, mineralization, corrosion coefficient, dissolved oxygen, biochemical oxygen demand, total nitrogen, protein nitrogen, total phosphorus, and total coliform. A comparison of the indices showed that the arithmetic modified index and Solway modified index are relatively similar for high‐quality water (i.e., they enable better discrimination between high‐ and low‐quality water). Both indices, however, tend to yield a lower index number for low‐quality waters.
Maintaining Granulation in a Denitrifying Upflow Sludge‐Blanket Reactor Treating Groundwater with Low Hardness
Authors: Rouse Joseph D. , Nakashima Takahiro , Furukawa Kenji
Published: September 2006

Maintenance of denitrifying granular sludge for treating soft groundwater (total hardness ≈ 75 mg calcium carbonate/L) in an upflow sludge‐blanket reactor was demonstrated with complete removal of applied nitrate (20 mg N/L) over extended operation and a hydraulic residence time of 34 minutes. A high pH of approximately 9.0 was shown to be important for generation of mineral precipitation needed for production of heavy granular sludge with good retention characteristics. As a method of increasing precipitation potential, pH adjustment was determined to be more economically favorable than calcium or alkalinity supplementation. In addition, temporary increases in substrate loading were shown to be effective for enhancing biomass levels in a manageable granular sludge. The significance of biomass in promoting mineral precipitation was discussed.
Evaluation of Constructed Wetland Treatment Performance for Winery Wastewater
Authors: Grismer Mark E. , Carr Melanie A. , Shepherd Heather L.
Published: September 2006

Rapid expansion of wineries in rural California during the past three decades has created contamination problems related to winery wastewater treatment and disposal; however, little information is available about performance of on‐site treatment systems. Here, the project objective was to determine full‐scale, subsurface‐flow constructed wetland retention times and treatment performance through assessment of water quality by daily sampling of total dissolved solids, pH, total suspended solids, chemical oxygen demand (COD), tannins, nitrate, ammonium, total Kjeldahl nitrogen, phosphate, sulfate, and sulfide across operating systems for winery wastewater treatment. Measurements were conducted during both the fall crush season of heavy loading and the spring following bottling and racking operations at the winery. Simple decay model coefficients for these constituents as well as COD and tannin removal efficiencies from winery wastewater in bench‐scale reactors are also determined. The bench‐scale study used upward‐flow, inoculated attached‐growth (pea‐gravel substrate) reactors fed synthetic winery wastewater. Inlet and outlet tracer studies for determination of actual retention times were essential to analyses of treatment performance from an operational subsurface‐flow constructed wetland that had been overloaded due to failure to install a pretreatment system for suspended solids removal. Less intensive sampling conducted at a smaller operational winery wastewater constructed wetland that had used pretreatment suspended solids removal and aeration indicated that the constructed wetlands were capable of complete organic load removal from the winery wastewater
Pilot‐Scale Evaluation of Separate‐Stage Nitrification Using an Attached‐Growth, Moving‐Bed Media Process
Authors: Zimmerman Robert A. , Richard Don , Bradshaw Andrew T. , Craddock Patti P.
Published: September 2006

Submerged attached‐growth processes, both fixed and moving bed, are becoming more popular. These processes may or may not be used in combination with suspended‐growth treatment. The objective of this project was to evaluate a tertiary attached‐growth, moving‐bed media nitrification system based on the ammonia‐nitrogen removal rates and effluent concentrations that could be achieved. A pilot‐scale system for nitrification of secondary municipal wastewater effluent was operated for 142 days. The minimum aeration requirements for media mixing provided sufficient dissolved oxygen. The generation of biological solids from nitrification was insignificant. Design effluent ammonia‐nitrogen concentrations (<6 mg/L) were achieved at influent loading rates greater than design (1.18 g ammonia‐nitrogen/[m2·d]) coincident with detention times shorter than design conditions (4 hours). Empirical relationships for the ammonia‐nitrogen removal rate and effluent concentration as a function of influent ammonia‐nitrogen loading were developed. Detention time is believed to be an important parameter affecting these relationships.
Effects of Oxygen on Anoxic Biodegradation of Benzoate during Continuous Culture
Authors: Çinar Özer , Deniz Timur , Grady C. P. Leslie
Published: September 2006

In this study, various amounts of oxygen were added to denitrifying chemostats receiving benzoate to mimic the input of oxygen to anoxic zones of biological nutrient removal systems. The effect of oxygen on the biodegradative capability of the mixed‐microbial culture for benzoate was investigated. The anoxic benzoate biodegradative capability of the culture was not significantly changed as the mass flowrate of oxygen was increased to 40% of the input benzoate chemical oxygen demand (COD) mass flowrate, but was decreased approximately 70% when the mass flowrate of oxygen was increased to 70% of the input benzoate COD mass flowrate. The decrease in the anoxic benzoate biodegradative capability was due primarily to the loss of the denitrifying enzymes (measured by the anoxic pyruvate‐degrading ability) and not to the loss of the key anoxic catabolic enzyme (benzoyl‐coenzyme A reductase). The proportional increase in the concentration of nitrate as the residual terminal electron acceptor and the lack of synthesis of aerobic ring‐cleavage enzymes as the oxygen input to the chemostat was increased suggest that the mixed microbial culture preferred oxygen to nitrate as the terminal electron acceptor, but degraded benzoate using the anoxic metabolic pathway. The concentration of the mixed microbial culture increased as the oxygen input to the chemostat was increased, suggesting that the oxygen was used by cytochrome cbb3 rather than quinol oxidase because the energetic yield of cytochrome cbb3 is higher than that of quinol oxidase or the nitrogen oxide reductases.
Odor and Volatile Organic Compound Removal from Wastewater Treatment Plant Headworks Ventilation Air Using a Biofilter
Authors: Converse B. M. , Schroeder E. D. , Iranpour R. , Cox H. H. J. , Deshusses M. A.
Published: September 2006

Laboratory‐scale experiments and field studies were performed to evaluate the feasibility of biofilters for sequential removal of hydrogen sulfide and volatile organic compounds (VOCs) from wastewater treatment plant waste air. The biofilter was designed for spatially separated removal of pollutants to mitigate the effects of acid production resulting from hydrogen sulfide oxidation. The inlet section of the upflow units was designated for hydrogen sulfide removal and the second section was designated for VOC removal. Complete removal of hydrogen sulfide (H2S) and methyl tert‐butyl ether (MTBE) was accomplished at loading rates of 8.3 g H2S/(m3·h) (15‐second empty bed retention time [EBRT]) and 33 g MTBE/(m3·h) (60‐second EBRT), respectively. In field studies performed at the Hyperion Treatment Plant in Los Angeles, California, excellent removal of hydrogen sulfide, moderate removal of nonchlorinated VOCs such as toluene and benzene, and poor removal of chlorinated VOCs were observed in treating the headworks waste air. During spiking experiments on the headworks waste air, the percentage removals were similar to the unspiked removals when nonchlorinated VOCs were spiked; however, feeding high concentrations of chlorinated VOCs reduced the removal percentages for all VOCs. Thus, biofilters offer a distinct advantage over chemical scrubbers currently used at publicly owned treatment works in that they not only remove odor and hydrogen sulfide efficiently at low cost, but also reduce overall toxicity by partially removing VOCs and avoiding the use of hazardous chemicals.
Flow and Transport Simulation Models for Prediction of Chlorine Contact Tank Flow‐Through Curves
Authors: Wang Hong , Shao Xuejun , Falconer Roger A.
Published: September 2006

Turbulent flow, solute transport, and chemical and biological decay are some of the basic processes encountered in water treatment plants. This paper presents recent developments in the numerical simulation of turbulent flow and disinfection processes in disinfection contact tanks. Simulation runs have been conducted for various tank design alternatives and in different grid resolutions. The accuracy of simulated contact tank flow and the disinfection process depends largely on calculations of the hydrodynamic and solute transport characteristics in the tanks. A key factor of this is the accuracy of advection and shear stress term computations, which can be affected by the use of different hydrodynamic submodels and numerical schemes. The performance of a simulation model relies to a great extent on the right combination of such submodels and numerical schemes. In this study, a number of simulation models were tested against realistic tank configurations and measurements to evaluate the various combinations of turbulence models and difference schemes by analyzing predicted flow and solute transport patterns, as well as the corresponding flow‐through curves. Models for disinfection tank simulations are recommended based on comparisons of simulation results with measurements. These models may also be applied to other water treatment processes such as wastewater treatment.
Kinetic Study of the Hydrodechlorination of Trichloroethene in Water Using a Platinum Catalyst and Hydrazine
Authors: Miyabe Kanji , Taniguchi Norie , Imura Aiko , Tezuka Yoshisato
Published: September 2006

Column experiments were used to measure the hydrodechlorination rate of relatively high concentrations of trichloroethene (TCE) (approximately 100 mg L−1). Trichloroethene in water was treated with a platinum on titania (Pt–TiO2) catalyst and hydrazine. The influence of some experimental conditions (i.e., flowrate, temperature, and pH) on the catalytic conversion of TCE was studied. The pseudo‐first‐order rate constant of the overall hydrodechlorination of TCE was approximately 1 × 10−3 to 1 × 10−2 s−1 in the temperature range of 283 to 328 K and was determined from the dependence of the TCE conversion on the contact time of the feed water with the catalyst by assuming first‐order kinetics. The activation energy of the catalytic hydrodechlorination of TCE was calculated as approximately 34 kJ/mol from the temperature dependence of the rate constant. The TCE conversion increases with increasing pH, and probably correlates with the presence of un‐ionized hydrazine.
Enhanced Biological Phosphorus Removal from Wastewater by Biomass with Different Phosphorus Contents, Part I: Experimental Results and Comparison with Metabolic Models
Authors: Schuler Andrew J. , Jenkins David
Published: September 2006

Enhanced biological phosphorus removal (EBPR) in wastewater treatment involves at least two types of bacterial metabolism: a polyphosphate‐accumulating metabolism (PAM) and a glycogen‐accumulating metabolism (GAM). Laboratory‐scale sequencing batch reactors operated in an anaerobic–aerobic cycle confirmed that low influent phosphorus/chemical oxygen demand (COD) ratio feed favored a GAM‐dominated culture and high influent phosphorus/COD ratio feed favored a PAM‐dominated culture, as indicated by changes in phosphorus, acetate, glycogen, and polyhydroxyalkanoate (PHA) concentrations during the anaerobic phase. Differential PAM and GAM dominance may explain variance in anaerobic phosphorus release, glycogen degradation, and PHA synthesis per acetate uptake ratios previously reported in EBPR systems and proposed metabolic models. The measurement of the ratios of anaerobic phosphorus release to acetate uptake and glycogen degradation to acetate uptake is suggested as an assay to estimate the relative dominance of PAM and GAM, respectively, in EBPR cultures.
Enhanced Biological Phosphorus Removal from Wastewater by Biomass with Different Phosphorus Contents, Part II: Anaerobic Adenosine Triphosphate Utilization and Acetate Uptake Rates
Authors: Schuler Andrew J. , Jenkins David
Published: September 2006

Data from laboratory‐scale sequencing batch reactors operated in an anaerobic–aerobic cycle showed that a low influent phosphorus/chemical oxygen demand (COD) ratio feed favored a glycogen‐accumulating metabolism (GAM)‐dominated culture and that a high influent phosphorus/COD ratio feed favored a polyphosphate‐accumulating metabolism (PAM)‐dominated culture. The PAM‐dominated culture anaerobically took up acetate approximately 7 times faster than the GAM‐dominated culture. Adenosine triphosphate (ATP) balances were performed assuming eight different metabolic scenarios that included the Entner–Doudoroff or the Embden–Myerhof glycolytic pathway, acetyl‐coenzyme A (CoA) synthase or the acetate kinase–phospho‐transacetylase (AK–PTA) system for acetyl‐CoA synthesis, and ATP synthesis or no ATP synthesis during fumarate reduction. The ATP available for transport of acetate into the cell (α) was calculated using these balances. The assumed quantity of ATP produced during fumarate reduction had a relatively small effect on α, particularly when PAM was dominant. When GAM was dominant, little or no ATP was available for acetate transport depending on the assumed scenario, and the Embden–Myerhof pathway was more feasible. The value of α increased with increasing PAM dominance for all eight metabolic pathways. The maximum calculated α value of 0.5 mol ATP/C‐mol acetate uptake occurred at maximum PAM dominance and when the Embden–Myerhof pathway was active, when ATP was produced during fumarate reduction, and when the AK–PTA system was active. This value of α was higher than previously calculated values with the same metabolic assumptions. An acetate uptake mechanism was suggested that included acetyl‐CoA synthetase and direct regeneration of the proton motive force by a proton‐translocating pyrophosphatase. Polyphosphate‐accumulating metabolism may have a competitive advantage over GAM through a higher anaerobic acetate uptake rate made possible by a greater use of energy for acetate uptake, by use of a different acetate uptake mechanism, or both.
Enhanced Biological Phosphorus Removal from Wastewater by Biomass with Different Phosphorus Contents, Part III: Anaerobic Sources of Reducing Equivalents
Authors: Schuler Andrew J. , Jenkins David
Published: September 2006

Laboratory‐scale sequencing batch reactors exhibiting enhanced biological phosphorus removal (EBPR) operated at different influent phosphorus/chemical oxygen demand (COD) ratios were analyzed to evaluate possible anaerobic sources of reducing equivalents. Assuming anaerobic glycogen degradation was the sole anaerobic reducing equivalent source, an anaerobic phase carbon balance showed that glycogen‐accumulating metabolism (GAM)‐dominated systems were nearly carbon‐balanced, but that polyphosphate‐accumulating metabolism (PAM)‐dominated systems had end‐anaerobic phase carbon deficits. An anaerobic‐phase reducing equivalent balance showed a reducing equivalent excess for the GAM‐dominated systems and a deficit for the PAM‐dominated systems, suggesting that glycogen degradation was not the sole reducing equivalent source for PAM. Reducing equivalent balances showed that metabolic models including complete anaerobic tricarboxylic acid (TCA) cycle activity, partial TCA cycle activity, and the glyoxylate bypass could provide the reducing equivalents required in PAM. Metabolic precursors produced in glycolysis, the TCA cycle, or modified versions of the TCA cycle could allow anaerobic growth and account for the PAM carbon deficits. The importance of considering both PAM and GAM activity in evaluating EBPR metabolic models was illustrated.
Evaluation of Odor Characteristics of Heat‐Dried Biosolids Product
Authors: Murthy Sudhir , Kim Hyunook , Peot Christopher , McConnell Laura , Strawn Mary , Sadick Thomas , Dolak Ivan
Published: September 2006

Because it produces an exceptional quality pellet product, heat drying of wastewater solids from municipal wastewater treatment plants is becoming more prevalent as biosolids management regulations become more restrictive. The product from heat drying is sometimes odorous as dry or wetted pellets. The odors, although not regulated, can be important for marketability and public acceptance of the product. The reasons for the odors are usually a result of upstream processing and management of wastewater solids prior to drying. The goals of this study were to determine odor characteristics and to compare the odors produced by evaluating odors from four types of heat‐dried biosolids products: all undigested; primary digested–waste activated sludge (WAS) undigested; all digested; and WAS lime stabilized pellets. The results are described in this paper.
Performance Evaluation of a Cloth‐Media Disk Filter for Wastewater Reclamation
Authors: Bourgeous Keith N. , Riess Joe , Tchobanoglous George , Darby Jeannie L.
Published: September 2006

A cloth‐media disk filter (CMDF) was evaluated as an alternative to granular‐medium filtration for use in wastewater recycling applications. The CMDF was effective for filtration of effluent from an activated‐sludge treatment process. Effluent turbidity values from the CMDF were consistently less than California's wastewater recycling application limit of 2 nephelometric turbidity units (NTU) for influent turbidity values of up to 25 NTU at hydraulic loading rates varying between 7 and 15 m/h (2.86 and 6.1 gpm/sq ft). The filter produced 154 m/d (3781 gpd/sq ft) at a hydraulic loading rate of 7 m/h (2.86 gpm/sq ft) with high turbidity (6 to 25 NTU) and 330 m/d (8102 gpd/sq ft) at a hydraulic loading rate of 15 m/h (6.1 gpm/sq ft) with low influent turbidity (≤6 NTU/m2 [6 NTU/sq ft] of filter cloth). The backwash water required by the CMDF at HLRs between 7 and 15 m/h (2.86 and 6.1 gpm/sq ft) and corresponding solids loading rates between 5 and 32 kg/(m2·d) (0.21 and 1.35 lb/d/sq ft) varied from 2 to 10% of the total influent flow. Thus, the CMDF could consistently meet the recycling requirements of a turbidity less than 2 NTU over a broad range of influent turbidity values and hydraulic loading rates.
Effect of Solids Retention Time on the Performance of Thermophilic and Mesophilic Digestion of Combined Municipal Wastewater Sludges
Authors: Moen Greg , Stensel H. David , Lepistö Raghida , Ferguson John F.
Published: September 2006

The steady‐state performance of thermophilic (55 °C) and mesophilic (35 °C) anaerobic digestion as a function of solids retention time (SRT) was evaluated in laboratory digesters at SRTs ranging from 4 to 15 days, and in pilot‐plant digesters at a 20‐day SRT. All of the digesters were fed the same source of municipal combined primary and secondary waste sludge. The destruction efficiency of volatile solids increased from 53% to 66% as the SRT was increased from 6 days to 20 days. The average destruction efficiency of volatile solids was 3 percentage points higher for the thermophilic digester at the 6‐day SRT and approximately 1 percentage point higher for the higher SRTs, but the difference was only statistically significant at the 15‐day SRT. Based on volatile suspended solids measurements, the thermophilic solids destruction efficiency was approximately 4 percentage points higher at the 10‐ and 15‐day SRTs. At a 4‐day SRT, methanogenic activity could only be maintained in the thermophilic digester. The pH, alkalinity, ammonia, volatile fatty acid, and soluble chemical oxygen demand concentrations were higher for the thermophilic digester at each SRT. At SRTs of 10 days and less, the thermophilic digester had a much higher propionate and slightly higher butyrate concentration. Carbohydrates were readily degraded by both digesters, protein was the major component in the sludge at the long SRTs, and lipid degradation increased with increasing SRT.
Evaluation of Different Methods for the Determination of Maximum Heterotrophic Growth Rates
Authors: Stasinakis Athanasios S. , Mamais Daniel , Paraskevas Panayotis A. , Lekkas Themistokles D.
Published: September 2006

This work evaluated the most commonly used methods for determining maximum heterotrophic specific growth rates (μm) in batch reactors. Parallel batch experiments were conducted under various initial substrate‐to‐biomass (S0/X0) ratios and values of the solids retention time (θc). The maximum specific growth rate, μm, was determined simultaneously according to measurements of oxygen consumption (i.e., oxygen uptake rate, OUR) and volatile suspended solids (VSS) increase. The S0/X0 ratio was found to significantly influence μm values. Under high S0/X0 ratios (= 20), fast‐growing bacteria seemed to gain a competitive advantage resulting in higher μm values than those obtained under low S0/X0 ratios (= 1.5). The OUR‐based estimate of μm (μm(OUR)), under certain circumstances, is differentiated from μm that is based on exponential bacterial growth (μm(VSS)), and seems to be more a measure of substrate oxidation than a measure of bacterial growth. At high S0/X0 ratio and low θc, μm(OUR) was significantly higher than the μm(VSS), indicating that considerable uncoupling between anabolism and catabolism was occurring under these conditions. Batch experiments conducted at high S0/X0 ratios seemed to be a more sensitive method for determining μm values in the presence of an inhibitor than tests conducted at low S0/X0 ratios.
Comparative Survey of the Influent and Effluent Water Quality of Shrimp Ponds on Mexican Farms
Authors: Ruiz–Fernández A.C. , Páez–Osuna F.
Published: September 2006

The influent and effluent water quality of two ponds at four aquaculture facilities (two intensive and two semiintensive growout systems) located on the Northwest coast of Mexico was monitored. Temperature, salinity, pH, dissolved oxygen, biochemical oxygen demand (self–consumption in 48 hours), total suspended solids, particulate organic material, nitrite, nitrate, ammonium, reactive and total phosphate, and chlorophyll a were analyzed every 2 weeks during two consecutive growout cycles. Changes recorded in most of these water quality variables were not strongly related to the management practices of the ponds, but rather to environmental factors. The mean percent differences between inflowing and outflowing water that were observed indicated that water used for culture returned to the natural environment depleted of nutrients (inorganic nitrogen and reactive phosphate), and it was evident that the rearing activities promoted the exportation of particulate material to the surrounding environment.
Cyanide Removal from Wastewater Using Gas Membranes: Pilot–Scale Study
Authors: Shen Zhisong , Han Binbing , Wickramasinghe Ranil
Published: September 2006

Results are presented for the removal of cyanide from four different wastewaters using hollow–fiber gas membranes. The pilot–scale membrane facility had a maximum treatment capacity of 1000 L using 10 hollow–fiber modules with a total membrane surface area of 180 m2. The results are in general agreement with previous laboratory–scale studies. However, different wastewaters contain different dissolved solutes. These dissolved solutes reduce the predicted efficiency of the cyanide removal process and the purity of the recovered cyanide. Other volatile species present in the wastewater could be removed with the cyanide into the strip solution. Further osmotic pressure differences between the wastewater and strip solution could lead to water vapor passing through the gas–filled pores of the microporous hollow–fiber membranes.
Changes in Anoxic Denitrification Rate Resulting from Prefermentation of a Septic, Phosphorus–Limited Wastewater
Authors: McCue Terrence , Naik Rahul , Zepeda Mauricio , Liu Yan–Hua , Vassiliev Igor , Randall Andrew Amis
Published: September 2006

A preliminary bench–scale study of parallel University of Cape Town (UCT) biological nutrient removal systems showed improvement in anoxic denitrification rates resulting from prefermentation of a septic (i.e., high volatile fatty acid [VFA] content), phosphorus–limited (i.e., total chemical oxygen demand/total phosphorus [TP] ratio < 40:1) wastewater. Net phosphorus removals due to enhanced biological phosphorus removal (EBPR) were only improved marginally by prefermentation in spite of significant increases in anaerobic phosphorus release, polyhydroxyalkanoate formation, and higher anoxic and aerobic uptakes. This probably was due to the high VFA/TP ratio in the raw influent relative to the VFA requirements for EBPR because enough VFAs were already present for phosphorus removal prior to prefermentation. An additional assessment of prefermentation using parallel UCT systems with step feed of 50% of the influent to the anoxic zone was completed. This second phase quantified the effect of prefermentation in a step–feed scenario, which prioritized prefermentation use to enhance denitrification rather than EBPR. While specific denitrification rates in the anoxic zone were significantly improved by prefermentation, high denitrification in the clarifiers and aerobic zones (simultaneous denitrification) made definitive conclusions concerning the potential improvements in total system nitrogen removal questionable. The prefermented system always showed superior values of the zone settling velocity and sludge volume index and the improvement became increasingly statistically significant when the prefermenter was performing well.
A Simplified Headspace Biochemical Oxygen Demand Test Protocol Based on Oxygen Measurements Using a Fiber Optic Probe
Authors: Min Booki , Kohler David , Logan Bruce
Published: September 2006

Batch respirometric tests have many advantages over the conventional biochemical oxygen demand (BOD) method for analysis of wastewaters, including the use of nondiluted samples, a more rapid exertion of oxygen demand, and reduced sample preparation time. The headspace biochemical oxygen demand (HBOD) test can be used to obtain oxygen demands in 2 or 3 days that can predict 5–day biochemical oxygen demand (BOD5) results. The main disadvantage of the HBOD and other respirometric tests has been the lack of a simple and direct method to measure oxygen concentrations in the gas phase. The recent commercial production of a new type of fiber optic oxygen probe, however, provides a method to eliminate this disadvantage. This fiber optic probe, referred to here as the HBOD probe , was tested to see if it could be used in HBOD tests. Gas–phase oxygen measurements made with the HBOD probe took only a few seconds and were not significantly different from those made using a gas chromatograph (t test; n 5 15, R2 5 0.9995, p , 0.001). In field tests using the HBOD probe procedure, the probe greatly reduced sample analysis time compared with previous HBOD and BOD protocols and produced more precise results than the BOD test for wastewater samples from two treatment plants (University Area Joint Authority [UAJA] Wastewater Treatment Plant in University Park, Pennsylvania, and The Pennsylvania State University [PSU] Wastewater Treatment Plant in University Park). Headspace biochemical oxygen demand measurements on UAJA primary clarifier effluent were 59.9 ± 2.4% after 2 days (HBOD2) and 73.0 ± 3.1% after 3 days (HBOD3) of BOD5 values, indicating that BOD5 values could be predicted by multiplying HBOD2 values by 1.67 ± 0.07 or HBOD3 by 1.37 ± 0.06. Similarly, tests using PSU wastewater samples could be used to provide BOD5 estimates by multiplying the HBOD2 by 1.24 ± 0.04 or by multiplying the HBOD3 by 0.97 ± 0.03. These results indicate that the HBOD fiber optic probe can be used to obtain reliable oxygen demands in batch respirometric tests such as the HBOD test.
Autotrophic Denitrification of High–Salinity Wastewater Using Elemental Sulfur: Batch Tests
Authors: Koenig Albert , Liu Linghua
Published: September 2006

The feasibility of autotrophic denitrification of a highsalinity wastewater using sulfur–oxidizing autotrophic denitrificants was studied. These autotrophic bacteria oxidize elemental sulfur to sulfate while reducing nitrate to elemental nitrogen gas, thereby eliminating the need for the addition of organic carbon compounds. A series of bench–scale batch tests was performed with synthetic and actual flue gas desulfurization (FGD) wastewater to examine the effects of various environmental and operational factors such as temperature, pH, high salinity, and potentially toxic substances on the rate of autotrophic denitrification using elemental sulfur. Specific denitrification rates of 6 to 8 mg nitrate–nitrogen (NO3—‐N)/g volatile suspended solids (VSS)·h were obtained. The highest denitrification rates were found between pH 7.0 and 8.0 and a temperature of 30 8 C. The denitrification rate started to decrease above an osmotic pressure of 19 atm (approximately 70% of seawater), independent of the type of salt ions, and amounted to approximately 70% activity at the concentration of seawater. Polyphosphate or pyrophosphate could be used as the source of phosphorus instead of orthophosphate because the latter caused immediate calcium phosphate precipitation in the FGD wastewater. Inhibiting factors attributed to inorganic or organic compounds originating from coal combustion were discussed.
Biodegradation of Methyl tert–Butyl Ether and BTEX at Varying Hydraulic Retention Times
Authors: Sedran Marie A. , Pruden Amy , Wilson Gregory J. , Suidan Makram T. , Venosa D
Published: September 2006

The feasibility of biologically degrading methyl tert–butyl ether (MTBE)–contaminated groundwater is dependent on the ability to degrade MTBE and its byproducts in the presence of other gasoline contaminants. This study investigates a mixed culture degrading both MTBE and benzene–toluene–ethylbenzene–xylene (BTEX) in a continuous–flow reactor with a biomass retention system (porous pot) at varying hydraulic retention times (HRTs). The reactor degraded both MTBE and BTEX simultaneously to less than the U.S. Environmental Protection Agency's drinking water standards and recommendations at an HRT of 3.76 days. Methyl tert–butyl ether was degraded from 75 mg/L to less than 1 μg/L and each BTEX compound was degraded from 17 mg/L to less than 1 μg/L. Effluent concentrations of MTBE and BTEX increased as the HRT was decreased from 3.76 to 0.52 days, but remained lower than drinking water limits. The highest MTBE effluent concentration was at 0.52 days and continued to average less than 10 μg/L. Although tert–butyl alcohol (TBA) is commonly sited as a degradation byproduct of MTBE, it remained lower than 1 μg/L throughout all reactor operation periods. The MTBE and BTEX observed yield coefficients for the reactor ranged from 0.11 to 0.16 mg biomass/mg MTBE and BTEX, with the rate increasing with increased HRT. Degradation rates from the reactor were compared to results from batch studies with the same culture on MTBE and TBA alone and in the presence of BTEX. Results of batch studies showed that BTEX was not required for this culture to degrade MTBE. The presence of BTEX only had an effect on the rate of MTBE degradation at the highest concentration, while BTEX significantly delayed the degradation of TBA at all concentrations. Batch studies also showed that the rate of degradation of TBA was higher with and without BTEX than the rate of degradation of MTBE, explaining the lack of high levels of TBA in the reactor.