bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Anaerobic–Aerobic Contact Time on the Change of Internal Storage Energy in Two Different Phosphorus‐Accumulating Organisms
Authors: Wang J.C. , Park J.K.
Published: September 2006

Laboratory‐scale sequential batch reactors were operated by feeding acetate and glucose as a single carbon source under the anaerobic–aerobic hydraulic retention times (HRTs) of 40:140 minutes and 120:560 minutes to assess the effect of anaerobic–aerobic HRTs on changes in internal storage energy of two different phosphorus‐accumulating organisms (PAOs). The PAOs grown on acetate accumulated poly‐Beta‐hydroxybutyrate in cells with a phosphorus content (phosphorus per volatile suspended solids, P/VSS) of 20 to 23%, whereas PAOs grown on glucose accumulated glycogen in cells with a phosphorus content of 10 to 15%. A longer anaerobic HRT resulted in a secondary phosphorus release that was not associated with internal cellular energy synthesis. A longer aerobic HRT resulted in a depletion of cellular energy. The PAOs with lower cellular energy may lose their competitive edge against other nonPAOs in biological phosphorus removal (BPR) systems. The danger in oversizing the anaerobic and aerobic zones in a BPR system was demonstrated. Optimal anaerobic HRT should be based on the volatile fatty acid uptake rate or the fermentation rate and optimal aerobic HRT should be determined based on the amount of internal energy synthesized during the anaerobic stage and the target effluent phosphorus concentration. From the analysis of cellular fatty acid composition and a metabolic study, PAOs grown on acetate were found to differ from those grown on glucose. Any PAO biochemical models proposed so far could not explain the metabolism of PAOs grown on glucose.
Changes in Dewatering Properties Between the Thermophilic and Mesophilic Stages in Temperature‐Phased Anaerobic Digestion Systems
Authors: Bivins Jason L. , Novak John T.
Published: September 2006

Temperature‐phased anaerobic digestion (TPAD) has become increasingly appealing in recent years because of the pathogen destruction capabilities of the system. However, there has also been concern about the dewatering properties of the solids created by these systems. A laboratory study was conducted at Virginia Polytechnic Institute and State University, Blacksburg, to determine the effect of thermophilic solids retention time (SRT) on dewatering properties of wastewater solids to characterize system parameters associated with dewatering and to understand the mechanisms causing changes in dewatering properties between the thermophilic and mesophilic phases. The study showed that, while anaerobic digestion caused dewatering properties to deteriorate, the solids varied little with thermophilic SRT. Acidogenesis was essentially complete after 1.5 days. Subsequent mesophilic digestion resulted in little change to dewatering properties and modest reductions in conditioning doses, but substantial reductions in biopolymer (protein and polysaccharides) occurred. It seems that thermophilic anaerobic digestion creates or releases colloidal materials that cause dewatering to be poor and subsequent mesophilic digestion for 15 days does little to improve the dewatering properties of solids in TPAD systems.
Dynamic Modeling to Assess Worker Exposure to Gas‐Phase Volatile Organic Compounds in Collector Sewers
Authors: Parker Wayne J. , Yu Jiyoung
Published: September 2006

A dynamic model was developed to simulate the behavior of volatile organic compounds (VOCs) in collector sewers when released to the sewer as a slug. The model incorporates liquid–gas mass transfer in sewer reaches and drop structures. The model was configured to reflect the structure and flows of a full‐scale collector sewer that had been previously characterized by a tracer study. Selected release scenarios were simulated to reflect potential spills into the sewer system. In the scenarios, the response of benzene, toluene, and tetrachloroethylene were predicted and the effect of sewer structures and flow conditions on headspace concentrations was assessed. It was found that the presence of inverted siphons can substantially reduce gas‐phase concentrations immediately downstream of the siphon. Tributary sewers that contribute contaminant‐free air to the collector can substantially reduce gas‐phase concentrations. Drop structures that enhance liquid–gas mass transfer can create zones of elevated gas‐phase concentrations of VOCs. Contaminants that enter a sewer in the gas phase can be scrubbed into the aqueous phase, thereby reducing gas‐phase concentrations. Application of the model to selected spill scenarios suggests that spills of gasoline into sewer systems may result in worker exposures to benzene that exceed short‐term exposure limits for this substance. Excessive exposures were observed irrespective of whether the compounds entered the collector sewer at the upstream end that had relatively low flow rates or part way along the collector sewer where flowrates were well established. Spills of other common solvents such as toluene and tetrachloroethylene did not seem to be likely to cause unacceptable exposures.
Rapid Detection of Salmonella in Water Samples by Multiplex Polymerase Chain Reaction
Authors: Kapley Atya , Lampel Keith , Purohit Hemant J.
Published: September 2006

A rapid protocol for detecting Salmonella species in water samples using the polymerase chain reaction (PCR) technique is described in this paper. Salmonellae, the etiological agents for typhoid fever, salmonellosis, and gastrointestinal infections, require more than 30 hours to be detected in water samples using current standard protocols. In epidemic conditions, where detection time is crucial, the multiplex PCR protocol developed can give results within 5 hours of collection of water samples. This latter protocol uses a gradient temperature program that allows simultaneous amplification of five different loci in a single reaction. The target loci used were invA, phoE, spvA, spvB, and 16s rDNA gene. The selected primers in the reactions allow the detection of a broad range of pathogenic Salmonella, whereas 16s rRNA locus was included as a reaction control for raw water samples devoid of Salmonella. The protocol has been successfully tried on standard strains and on samples collected from river water.
Hydraulic Characteristics of a Subsurface Flow Constructed Wetland for Winery Effluent Treatment
Authors: Grismer Mark E. , Tausendschoen Markus , Shepherd Heather L.
Published: September 2006

Similar to batch reactors, wastewater treatment by constructed wetlands depends on the detention time within the system. Unlike reactors, however, internal detention times within constructed wetlands are largely unknown because they are a function of wastewater flowpaths and extent of wastewater interaction with constructed wetland porous media and vegetation. Internal hydraulic characteristics of two pilot‐scale constructed wetland tanks designed to reclaim winery wastewater are evaluated to link treatment performance to hydraulic properties and compare these properties between new and old tanks. Each tank contained pea gravel to a 0.95‐m depth. The old tank had established bulrush and cattail vegetation and had operated as a winery wastewater treatment system for more than 3 years, while the new duplicate tank had no vegetation. Two impulse‐type, bromide‐tracer studies were conducted, and the results were analyzed, assuming that traditional one‐dimensional flow breakthrough‐curve models could be applied to the three‐dimensional flow system. Because of variable recovery of the tracer at different locations along the tanks, the method of moments was used to analyze bromide residence‐time distributions (RTDs) to determine detention times, water velocities, and dispersion coefficients. While tank outflow tracer RTDs could not be described using either plug‐flow reactor or simple continuously mixed‐system models, 20 to 35 tanks‐in‐series models adequately replicated the measured outflow RTDs. No preferential flows were observed in the constructed wetland tanks because outflow RTDs were nearly symmetric and surprisingly similar. Overall, outflow RTD‐based dispersion coefficients (D) were small and only slightly different between the old (D = 1.5 mm2/s) and new (D = 1.2 mm2/s) tanks. However, the mean detention times in the new and old tanks were approximately 15% greater and 30% less, respectively, than those estimated using the average gravel porosity and assuming plug flow.
Iron and Aluminum Hydroxy (Oxide) Coated Filter Media for Low‐Concentration Phosphorus Removal
Authors: Ayoub George M. , Koopman B. , Pandya Neha
Published: September 2006

The presence of phosphates in water and wastewater negatively affects the aquatic environment. Several processes have been used for the removal of phosphorus from water and wastewater; however, most failed in attaining removal levels that will alleviate the problems associated with its presence. In this study, laboratory experiments were conducted to determine the efficacy of iron aluminum hydroxy (oxide) coated filter media in removing low concentrations of phosphates. Two media (silica sand and olivine) were used in the experiments, and tests were conducted on distilled water, artificial groundwater, tap water, and treated wastewater. The effect of flowrates, ranging from 10 to 80 mL/min (3.4 to 27.2 m3/m2·h), on phosphate removal efficiencies was evaluated for distilled water. Results indicate that the process was very effective in phosphate removal (more than 90%) present in low concentrations (approximately 0.5 mg/L) when applied to distilled water and artificial groundwater and with less success when applied to tap water (less than 80%) and treated wastewater effluent (less than 70%). This reduced removal may be attributed to the presence of competing species and, in this case, in the form of sulfates. The results also show that, for distilled water, the treated pore volumes before breakthrough (set at 0.1 mg/L) ranged from 137 to 348 pore volumes (51 to 129 bed volumes) for sand and 245 to 370 pore volumes (100 to 152 bed volumes) for olivine, depending on the flowrates. The results for distilled water further indicated that the flowrates used in the experiments had negligible effect on the removal efficiency of the process, and operating rates of 27 m3/m2·h could be applied to distilled water with negligible negative effects.
Increasing Flexibility in the Design of Wastewater Treatment Processes
Authors: Hopkins Lisa N. , Lant Paul A. , Newell R.B.
Published: September 2006

An increasing focus on the design of biological nutrient removal processes and the development of new and varied designs (propelled by increasing needs for higher efficiencies and lower costs) has introduced the need for improved methods of design for wastewater treatment plant (WWTP) processes. These design methods may include studies of process operability (i.e., flexibility, controllability, and resilience). This paper focuses on flexibility and the tools available to facilitate the study of flexibility. A simple example is used to demonstrate a method of flexibility analysis and a more complex example is used to illustrate the significance of the results to WWTP process design. The most significant result is that the flexibility of a process can sometimes be significantly increased with negligible increases in capital costs.
Ozone Decolorization of Mixed‐Dye Solutions in a Gas‐Induced Reactor
Authors: Hsu Yung‐Chien , Chen Jia‐Tsween , Yang Hsiang‐Cheng , Chen Jyh‐Herng , Fang Charng‐Fwu
Published: September 2006

Ozone decolorization of several mixed two‐ and three‐dye solutions was studied using a newly developed gas‐induced reactor. Decolorization kinetics of the mixed‐dye solutions, the ozone utilization rate, and chemical oxygen demand (COD) elimination during decolorization were all examined. In the kinetic study, the method of absorption of dye solution during ozonation was used with mixed two‐dye solutions. For more complicated mixed three‐dye solutions, the method of the American Dye Manufacturers Institute (New York) for determining decolorization kinetics was adopted. Overall, pseudo‐first‐order kinetics can be used to describe the behavior of mixed‐dye solutions during decolorization; however, two‐stage decolorization kinetics occur in certain mixed three‐dye solutions. Using the gasinduced reactor, a greater than 90% ozone utilization rate was obtained before 90% decolorization was reached. The elimination of COD was approximately 33% before 96% decolorization.
Characterization of Denitrification and Nitrification in a Step‐Feed Alternating Anoxic–Oxic Sequencing Batch Reactor
Authors: Lin Ying‐Feng , Jing Shuh‐Ren
Published: September 2006

This study was conducted to characterize the denitrification and nitrification in a bench‐scale sequencing batch reactor operating with a three‐stage, alternating anoxic–oxic sequence and step feed (SAOSBR) for treating synthetic wastewater. The results of long‐term operation and dynamic studies showed that the SAOSBR increased the availability of organic matter in wastewater for exogenous denitrification in anoxic periods, and subsequently allowed nitrification to occur under a lower organic loading in oxic periods. Comparatively high kinetic rates of 1.2 to 6.6 mg nitrate/g mixed liquor suspended solids (MLSS) · h for denitrification and 1.0 to 2.8 mg nitrogen/g MLSS · h for nitrification were found in dynamic studies. With sufficient influent organics and alkalinity, complete denitrification and full nitrification could be achieved sequentially in the alternating anoxic and oxic periods, resulting in an average total nitrogen removal efficiency up to approximately 90%. Alkalinity recovery because of exogenous denitrification was experienced, and a minimum influent alkalinity to total Kjeldahl nitrogen (TKN) ratio of 2.4 was required to reach complete TKN removal. The pH value would be a better parameter other than oxidation–reduction potential or dissolved oxgyen to determine the completeness of nitrification and denitrification in the SAOSBR.
Use of Biodegradable Dissolved Organic Carbon to Assess Treatment Process Performance in Relation to Solids Retention Time
Authors: Babcock Roger W. , King Stacey , Khan Eakalak , Stenstrom Michael K.
Published: September 2006

A biodegradable dissolved organic carbon (BDOC) method has been developed and used to analyze secondary‐ and advanced‐treated wastewater effluents and to investigate correlations between residual organic content and the solids retention time (SRT). Conventional biochemical oxygen demand (BOD) bottles and a 28‐day incubation period were used. Secondary wastewater effluents from Hawaii were found to contain between 9.0 and 14.0 mg/L of dissolved organic carbon (DOC), of which 23 to 35% was biodegradable in the 28‐day BDOC test (from a survey of nine treatment plants). Bench‐scale, continuous‐flow activated‐sludge biological reactors treating synthetic wastewater were operated at SRTs between 2 and 15 days, and effluent BDOCs were determined. A good BDOC prediction equation was developed that incorporates the initial DOC, the DOC remaining after 5 days, and the SRT of the system from which the sample originated. This equation can be used to determine the BDOC value using data that can be obtained during a conventional 5‐day BOD test. The determined equation was found to be appropriate for some of the full‐scale wastewater effluent survey data.
Tracking Sources of Bacterial Contamination in Stormwater Discharges to Mission Bay, California
Authors: Schiff Kenneth , Kinney Patrick
Published: September 2006

Sources of the indicator bacteria total coliform, fecal coliform, and enterococcus were investigated in stormwater flows discharging to Mission Bay, a heavily used aquatic park in San Diego, California. Stormwater flows were targeted because long‐term receiving water monitoring of the bay indicated that wet weather discharges were the predominant source of bacterial contamination. Exceedences in water quality objectives for body contact recreation established by the State of California most often occurred in the east bay, where the least amount of circulation and largest quantities of stormwater discharges occur. Unlike the wet weather results, almost all of the 89 storm drains that discharge to the bay either did not have flowing fresh water or did not contain exceedingly high bacteria densities during dry weather. Upstream tracking during multiple storm events on two of the largest watersheds draining to the bay showed that sources of indicator bacteria were diffuse and widespread. Densities were as high at the head of each watershed as they were at the mouth, where both discharged to the bay. Every reach in each creek exceeded State of California water quality objectives and had densities similar to surface flows measured before they entered the separate municipal storm sewer system from urban land uses, such as residential, commercial, and industrial, as well as open lands.
Temperature Effects in Treatment Wetlands
Authors: Kadlec Robert H. , Reddy K.R.
Published: September 2006

Several biogeochemical processes that regulate the removal of nutrients in wetlands are affected by temperature, thus influencing the overall treatment efficiency. In this paper, the effects of temperature on carbon, nitrogen, and phosphorus cycling processes in treatment wetlands and their implications to water quality are discussed. Many environmental factors display annual cycles that mediate whole system performance. Water temperature is one of the important cyclic stimuli, but inlet flow rates and concentrations, and several features of the annual biogeochemical cycle, also can contribute to the observed patterns of nutrient and pollutant removal. Atmospheric influences, including rain, evapotranspiration, and water reaeration, also follow seasonal patterns. Processes regulating storages in wetlands are active throughout the year and can act as seasonal reservoirs of nutrients, carbon, and pollutants. Many individual wetland processes, such as microbially mediated reactions, are affected by temperature. Response was much greater to changes at the lower end of the temperature scale (< 15 °C) than at the optimal range (20 to 35 °C). Processes regulating organic matter decomposition are affected by temperature. Similarly, all nitrogen cycling reactions (mineralization, nitrification, and denitrification) are affected by temperature. The temperature coefficient (θ) varied from 1.05 to 1.37 for carbon and nitrogen cycling processes during isolated conditions. Phosphorus sorption reactions are least affected by temperature, with θ values of 1.03 to 1.12. Physical processes involved in the removal of particulate carbon, nitrogen, and phosphorus are not affected much by temperature. In contrast, observed wetland removals may have different temperature dependence. Design models are over simplified because of limitations of data for calibration. The result of complex system behavior and the simple model is the need to interpret whole ecosystem data to determine temperature coefficients. Temperature seems to have minimal effect on biochemical oxygen demand (0.900 < θ < 1.015) and phosphorus (0.995 < θ < 1.020) removal, and more significant effect on nitrogen removal (0.988 < θ < 1.16). In colder climates, there may be seasonal slowdown of treatment, which can decrease the overall treatment efficiency of constructed wetlands.
Pipe Friction Head Loss in Transportation of High‐Concentration Sludge for Centralized Solids Treatment
Authors: Murakami Hisashi , Katayama Hideaki , Matsuura Hidetsugu
Published: September 2006

The objective of this study was to develop a method of predicting pipe friction head loss, which is a key factor in pipeline transportation of high‐concentration sludge, thereby optimizing design for pipeline systems. The study involved both experimentation and analysis of pipeline transportation. Moreover, the study led to the representation of pipe friction head loss as functions of average velocity, transportation distance, pipe diameter, pipe interior roughness, and solids viscosity and temperature.
Anaerobic Migrating Blanket Reactor Treatment of Low‐Strength Wastewater at Low Temperatures
Authors: Angenent Largus T. , Banik Gouranga C. , Sung Shihwu
Published: September 2006

The feasibility of the compartmentalized anaerobic migrating blanket reactor (AMBR) was studied for the treatment of low‐strength soluble wastewater under low‐temperature conditions. During an operating period of 186 days, a 20‐L AMBR was fed nonfat dry milk substrate as a synthetic wastewater at low temperatures (15 and 20 °C). The concentration of the influent was constant at chemical oxygen demand (COD) and 5‐day biological oxygen demand (BOD5) concentrations of 600 and 285 mg/L, respectively. The soluble COD (SCOD) removal efficiency was 73% at the end of the operating period (15 °C) at a 4‐hour hydraulic retention time (HRT), while the total COD (TCOD) removal efficiency was 59%. At a 4‐hour HRT, staged conditions promoted complete removal of propionic acid in the final compartments of the reactor. The specific methanogenic activity of granules increased slowly until the end of the operating time, improving the removal rate. Biomass was retained effectively, as evidenced by the solids retention time (SRT) that was always greater than 50 days even during step decreases of the reactor HRT from 12 hours to 4 hours. A long SRT also promoted system stability during changes in flow, which was observed by SCOD removal efficiencies staying greater than 70%. During a hydraulic stress test, the HRT was reduced from 4 hours to 1 hour for one day (24 HRTs) in which volatile suspended solids (VSS) in the effluent increased from an average background level of 8.7 g/d to 35 g/d and the SRT decreased from 50.5 days to 12.6 days. However, mixed liquor volatile suspended solids concentration decreased only by 1 g/L, and hence a similar COD removal efficiency and biogas production was found one day after the hydraulic stress (as compared to one day before the hydraulic stress).
Analysis of Statistical Outliers with Application to Whole Effluent Toxicity Testing
Authors: Buckley James A. , Georgianna Thomas D.
Published: September 2006

In this analysis, low‐value outliers were detected in five data sets obtained from laboratory records. The effect of removing the outliers by three methods of data rejection (asymmetrical and symmetrical trimming and Winsorization) revealed that all three methods slightly increased the mean and reduced the variance of the data sets. These opposing effects on the results of a hypothesis test of means were examined in the context of passing or failing a regulatory requirement of no significant difference between an effluent concentration and a control. Analysis by statistical resampling of one data set showed that while all data rejection methods reduced the level of Type II error in a hypothesis test of no difference in reproduction between a test concentration and a regulatory limit, asymmetrical trimming was the best in this regard.
Evaluation of Direct Removal of Nitrate with Entrapped Mixed Microbial Cell Technology Using Ethanol as the Carbon Source
Authors: Qian X. , Yang P.Y. , Maekawa T.
Published: September 2006

Biological denitrification from simulated contaminated groundwater using ethanol as an external carbon source was investigated with an entrapped mixed microbial cell (EMMC) system. Ethanol was used as an external carbon source to serve both as the energy source for the nitrate removal reaction and substrate for microorganisms in the system. The hydraulic retention time and chemical oxygen demand (COD)/nitrogen ratio significantly affect nitrate removal performance and, therefore, must be monitored carefully to achieve high rates of nitrate and COD removal. The effect of packing ratios of carriers in the reactor on nitrate removal performance was also investigated. The removal of nitrate and COD in reactors with various carrier packing ratios (12, 22, and 35%) is not significantly different during steady‐state operation. However, the start‐up periods in these three reactors are significantly different. The highest packing ratio can result in a fast removal of nitrate during the start‐up periods. Results of solids retention time (SRT) analysis indicate that a long SRT in the EMMC system contributes to the stable removal of nitrate and to fast start up of the system. The increase of SRT is related to the increase in days of operation, SRT is maintained at a level of more than 200 days.
Evaluation of Agricultural Sediment Load Reductions Using Vegetative Filter Strips of Cool Season Grasses
Authors: Fasching Richard A. , Bauder James W.
Published: September 2006

Vegetative filter strips for controlling sediment generated from the bare ground (i.e., ground not protected by mulch or plant cover) were studied. Plots consisted of a 4.6‐m clean‐tilled upslope sediment source area and a 12.2‐m vegetative filter strip located downslope from the sediment source area. Vegetative filter strips consisted of pure stands of six adapted cool season grasses and two cereal grains. Sediment‐laden runoff was transported into the upslope edge of each filter strip. Runoff samples were collected from the lower end of each plot and analyzed for nonflow weighted sediment concentration. The rate of advance of water through each vegetative filter strip was measured. Additional measurements were made to define the plant characteristics of each vegetative filter strip species. In general, planted vegetative filter strips resulted in a 68% reduction in concentration of sediment in initial runoff from a 50‐year, 24‐hour storm event on prewetted soil. Crested wheatgrass and smooth bromegrass vegetative filter strips reduced water flow velocity an average of 217% compared with the clean‐tilled control plot. The length of time that water remained in the vegetative filter strip modestly correlated with average sediment concentration in runoff that was 5.5 g/L and 5.0 g/L, respectively, compared with the control plot, which yielded 16.3 g of sediment/L of runoff. Under dry soil conditions, sediment concentration in runoff from bromegrass and crested wheatgrass was reduced by an average of 85% compared with the bare control plot. Length of time for water to advance through the smooth bromegrass and crested wheatgrass vegetative filter strips increased an average of 325% compared with the length of time required to flow through the clean‐tilled bare strip.
Time‐Dependent Retardation Model for Chemical Oxygen Demand Removal in a Subsurface‐Flow Constructed Wetland for Winery Wastewater Treatment
Authors: Shepherd H.L. , Tchobanoglous G. , Grismer M.E.
Published: September 2006

The relative success of chemical oxygen demand (COD) removal models to describe measured rates of COD removal in a pilot‐scale constructed wetland designed for treatment of high‐strength winery wastewater are evaluated using retention times determined from tracer studies. Not surprisingly, two‐parameter residual and retardation models better fit the measured removal data than single‐parameter, first‐order decay models for wastewater at average COD loadings up to nearly 5000 mg/L. The residual and retardation models yielded nearly equivalent fits to the measured data. However, the retardation model had more consistent parameters for COD removal data across different depth levels in the constructed wetland and at different loadings, and a slightly smaller sum of least‐squared errors. The retardation model seems to be appropriate for constructed wetland design because it allows a steady decrease in COD with increased treatment time rather than a constant residual COD (C* ) value. From the least‐squares optimization procedure used to estimate model parameters (a volumetric rate constant, Kv, range of 3 to 12 d−1), nonrealistic, or physically meaningless, large C* values (C* range of 23 to 450 mg COD/L) that were dependent on COD loading were obtained, potentially underestimating the constructed wetland system's actual winery wastewater treatment potential. The optimal parameters for the retardation model applied to the pilot‐scale constructed wetland ranged from 9 to 12 d−1 for the initial degradation rate constant, Ko, and 2 to 5 d−1 for the time‐based retardation coefficient, b. These values should be verified for full‐scale field systems based on field measurements currently underway.
Persistency of Bacterial Indicators in Biosolids Stabilization with Coal Fly Ash and Lime
Authors: Wong Jonathan W.C. , Fang Min , Jiang Rongfeng
Published: September 2006

Alkaline coal fly ash and lime were tested for their effectiveness in pathogen removal from biosolids at different time intervals and temperatures. Coal fly ash at 10 and 35% w/w was mixed with dewatered biosolids and then the ash–biosolids mixture was mixed separately with 0, 1.1, 2.2, 4.4, 8.5, 11, and 18% calcium oxide (w/w on a dry weight basis) with and without heating to 55 °C. Total bacteria, salmonella, and total coliforms were monitored at various time intervals. Both ash–biosolids mixtures with or without lime amendment had a significantly lower total bacterial population than the biosolids control, but the residual indigenous bacterial flora in the ash and lime stabilized biosolids still maintained a population of greater than 104 g−1 dry biosolids. Alkaline‐stabilized biosolids with a lime amendment rate greater than 8.5% could maintain pH greater than or equal to 12 for more than 2 hours, which effectively removed total coliforms and salmonella in the mixture. Heat treatment to 55 °C and a storage time of 14 days provided an added advantage resulting in a further reduction in pathogens for all treatments. It is recommended that 10% ash–biosolids mixture should be amended with a minimum of 8.5% lime on a dry weight basis for at least 2 hours to achieve acceptable levels of salmonella and total coliforms to ensure no pathogenic risk following land application.
Degradation of Oleic Acid in Anaerobic Filters: The Effect of Inoculum Acclimatization and Biomass Recirculation
Authors: Pereira Alcina , Mota Manuel , Alves Madalena
Published: September 2006

The degradation of oleic acid in anaerobic filters was studied and the effect of an acclimated inoculum and biomass recirculation was evaluated. Three anaerobic filters (R1, R2, and R3) were operated in parallel. The anaerobic filters R1 and R2 were inoculated with nonacclimated biomass, whereas the anaerobic filter R3 was inoculated with acclimated biomass. In the anaerobic filters R2 and R3, biomass settling and recirculation were applied. The use of an acclimated inoculum and biomass recirculation (R3) was beneficial in terms of removal efficiency, which was 4 to 8% higher than in the anaerobic filters R1 and R2 when oleate was the sole carbon source fed to the reactors at an applied organic load of 12.5 kg of chemical oxygen demand (COD)/m3·d, even with an oleate to calcium and magnesium ion molar concentration ratio of 6.8. Biomass recirculation significantly reduced the biomass washout and the toxic effect on the acetogenic and methanogenic populations. The use of an acclimated inoculum was beneficial in terms of methane yield, which was 50% greater than that observed for the reactors inoculated with nonacclimated inoculum for the highest applied organic loading rate (12.5 kg COD/m3·d). At the end of the operation, the biomass was encapsulated by a whitish matter, which was well detected by microscopic examination. When this sludge was incubated in batch vials at 37 °C where no substrate was added, methane production from the adsorbed organic matter was evidenced, attaining a maximum value (at standard temperature and pressure) of 39.7 mL/g volatile solids·d for the biomass taken from R1. With stirring (150 r/min), the methane production rate was 13.8 times higher than under static conditions. When oleate was added to this sludge, methane production was delayed, suggesting that adsorbed matter can be an intermediate of oleate degradation such as stearic, palmitic, myristic, or other saturated acids.
Upflow Anaerobic Sludge Blanket Treatment of Starch Wastewater Containing Cyanide
Authors: Annachhatre A.P. , Amornkaew A.
Published: September 2006

Treatment of tapioca starch wastewater containing cyanide using an upflow anaerobic sludge blanket (UASB) process was investigated. Sludge from an anaerobic lagoon treating tapioca starch wastewater was used as seed. Performance of the UASB reactor with influent cyanide concentrations up to 25 mg/L was assessed. The inhibitory effects of cyanide were temporary and reversible. The process required longer recovery period for higher cyanide dosage. For 25 mg/L of cyanide concentration in the feed, the reactor required 15 days for complete recovery. Process performance was sensitive to operating parameters such as upflow velocity, cyanide loading rate, and chemical oxygen demand (COD) loading rate. A maximum cyanide loading rate of 0.38 kg/m3·d was achieved in the process at a COD loading rate of 50 kg COD/m3·d. Experiments with tapioca starch wastewater containing up to 10 mg/L of cyanide yielded satisfactory cyanide removal of approximately 93 to 98% and gas productivity of 7.5 m3/m3·d with a COD loading rate of 30 to 40 kg COD/m3·d.
Seeding Effect on Cocomposting Wastewater Biosolids with Coal Fly Ash
Authors: Fang Min , Wong Jonathan W.C.
Published: September 2006

The seeding effect on fly ash‐amended biosolids composting was evaluated by inoculating a mixture of ash and biosolids with seeding materials before composting. These inocula included thermophilic bacteria (Bacillus. brevis, B. coagulans, and B. licheniformis) isolated from the ash–biosolids compost, a commercial decomposter, and recycled biosolids compost. Although the addition of these microbial additives to the ash–biosolids compost improved the population of thermophilic bacteria at the early stage of composting, the improvement was negligible after 4 days of composting. Inoculation with isolated bacterial culture, milk powder, or the decomposter, only, did not effectively improve the decomposition of organic matter compared with those receiving inoculation of both microbial additives and milk powder together. The isolated Bacillus species was as efficient as the commercial decomposter in accelerating the decomposition rate during ash‐amended biosolids composting as indicated by the high amounts of carbon dioxide evolved and cumulative weight loss. Ash–biosolids compost inoculated with 15% (dry weight basis) of recycled compost showed a comparable decomposition activity to those inoculated with bacterial culture and the commercial decomposter with milk powder. Taking into consideration the lower operating cost and acceptable decomposition efficiency, recycled biosolids compost seemed to be a promising additive to ash‐amended biosolids compost to improve composting efficiency.
Anaerobic Co‐Digestion of Aircraft Deicing Fluid and Municipal Wastewater Sludge
Authors: Zitomer D. , Ferguson N. , McGrady K. , Schilling J.
Published: September 2006

At many airports, aircraft deicing fluid and precipitation mix, becoming aircraft deicing runoff having a 5‐day biochemical oxygen demand (BOD5) of 102 to 10 6 mg/L. Publicly owned treatment works can be used for aerobic biological treatment; however, it may be more economical to use anaerobic digesters to codigest a mixture of aircraft deicing fluid and sludge. The objectives of this investigation were to determine benefits and appropriate propylene glycol aircraft deicing fluid loadings to anaerobic codigesters. Results demonstrate aircraft deicing fluid can be successfully codigested to produce methane; supernatant BOD5 and Kjeldahl nitrogen concentration were not higher in codigesters compared to a conventional digester. Aircraft deicing fluid loadings as high as 1.6 g chemical oxygen demand (COD)/L·d were sustainable in codigesters, whereas system fed only aircraft deicing fluid with nutrients and alkalinity achieved a loading of 0.65 g COD/L·d. The sludge used increased digester alkalinity and provided nitrogen, iron, nickel, cobalt, and biomass required for methanogenesis. The deicer provides organics for increased methane production.
Characterization and Evaluation of a Novel Exalting Round‐Plate Photocatalytic Reactor
Authors: Xing He , Wang Yizhong , Hu Chun
Published: September 2006

A novel reactor, the exalting round‐plate photocatalytic reactor (ERPPR), was designed and evaluated. Residence time and light intensity distributions were determined by stimulus–response experimentation and an irradiation meter, respectively. The effects of hydraulic loading of the round plate and aeration on the photocatalytic degradation of azo dye were investigated during different conditions. Experimental results show that the ERPPR is intermediate between a completely stirred tank reactor and a plug‐flow reactor. Mean hydraulic loadings at different rotational speeds were significantly influenced by the reaction rate for dye decolorization. Photodegradation of the dye, however, was not significantly influenced by the amount of oxygen gas aerated, except when aerating with pure oxygen. Results further indicate that the photoreaction atmosphere of the ERPPR depends on mass transfer between gas and liquid on the round plate. The primary role of aeration is to mix catalyst and solution.
Oxygen Fluxes and Ammonia Removal Efficiencies in Constructed Treatment Wetlands
Authors: Wu Mei‐Yin , Franz Eldon H. , Chen Shulin
Published: September 2006

Ammonia‐removal efficiency in constructed wetlands is often limited by the amount of oxygen available in the system. In this study, the oxygen‐transfer rates to laboratory‐scale, subsurface‐flow and free‐water‐surface constructed wetlands were quantified for two input concentrations of ammonia, 10 and 50 mg nitrogen/L, both with and without Typha latifolia. Rates of oxygen diffusion into the subsurface‐flow constructed wetlands were 6.01 to 7.92 g/m2·d and were strongly correlated with ammonia concentration in the water. In contrast, low oxygen diffusion rates of 1.36 to 1.76 g/m2·d were observed for the free‐water‐surface system. The presence of Typha latifolia had small but consistent effects on atmospheric oxygen‐diffusion rates and ammonia‐removal efficiencies in both the subsurface‐flow and free‐water‐surface systems. The observed small effects were consistent with measurements of oxygen inputs from T. latifolia roots. Only approximately 0.023 g/m2·d of oxygen was released from roots of T. latifolia, as measured using the titanium (III) citrate buffer method. The results for the ammonia‐removal rates of the laboratory‐scale constructed wetlands were further verified using pilot‐scale constructed wetlands under greenhouse conditions.
Microbial Risks from Wastewater Irrigation of Salad Crops: A Screening‐Level Risk Assessment
Authors: Petterson S.R. , Ashbolt N.J. , Sharma A.
Published: September 2006

The potential health risk from viruses, associated with the consumption of lettuce crops spray irrigated with secondary‐treated municipal effluent, has been evaluated in the first level investigation of a tiered microbial risk assessment. The study assessed the impact of two factors on the estimated risk of infection: a suitable probability density function for the occurrence of human enteroviruses in irrigation water and appropriate die‐off rates for viruses on lettuce crops. A Monte Carlo simulation using a log‐normal and a nonparametric, kernel estimated probability density function indicated that slight changes in the upper tail of the probability density function had a relatively low effect on the estimated infection rates. Predicted infection rates were much more sensitive to the decay rate of viruses than occasional high virus numbers. The median and 99th percentile risks of infection from the overall model were 0.10 and 0.51/10 000 lettuce consumers, respectively, indicating possible human health concern, and the justification of a more detailed microbial risk assessment.
Aerated Biofiltration for Simultaneous Removal of Iron and Polycyclic Aromatic Hydrocarbons from Groundwater
Authors: Richard Don E. , Dwyer Daryl F.
Published: September 2006

Filters incorporating the principles of biological accumulation have been used in Europe to remove iron from drinking water for many years. The authors of this study hypothesized that a modified biological iron‐removing filter could simultaneously degrade polycyclic aromatic hydrocarbons (PAHs) in groundwater impacted by former manufactured gas plant (MGP) operations. The MGP‐impacted groundwater obtained for this study had an average total iron concentration of 3.8 mg/L and an average total dissolved PAH concentration of 3.0 mg/L. Naphthalene was the primary PAH, with an average concentration of 2.8 mg/L. The groundwater was passed intermittently through duplicate gravel‐media columns at 15 to 30 cm/d for 2 months while filtered air was delivered countercurrently at 4 mL/min. The columns remained partially saturated throughout the study. Flooding, which would have indicated plugging of the columns, was not observed, and the pressure needed to aerate the columns remained constant. Total iron in the effluent was below the detection limit of 0.1 mg/L (97% removal) for 40 days of operation. Removal of total PAHs, primarily two‐ and three‐ring compounds, averaged 99%. This single‐stage treatment process represents an economical alternative to biological treatment systems currently available for MGP‐impacted groundwater that require pretreatment to remove iron.
Measurement of Microbial Numbers and Biomass Contained in Thermophilic Anaerobic Reactors
Authors: Solera R. , Romero L.I. , Sales D.
Published: September 2006

This paper describes the determination of the microbial population in terms of the number, biomass, and composition of single‐ and two‐phase, laboratory‐scale thermophilic (55 °C) anaerobic reactors under steady‐state conditions. Epifluorescence microscopy with 4',6‐diamidine‐2‐phenylindole (DAPI) as fluorochrome was used to determine the total number of microorganisms in the reactors, and autofluorescence microscopy was used to determine the total methanogenic bacteria populations. The results obtained by the direct count methods were compared to the quantity of biomass contained in the system, which was determined by volatile suspended solids. The concentration of acidogenic bacteria was estimated by subtraction of the autofluorescence results from those of the DAPI epifluorescence microscopy. The viable bacterial population was determined by plating techniques using an anaerobic chamber. The total bacterial and methanogenic populations of single‐stage digesters increase when the hydraulic retention time decreases; nevertheless, the percentages of the principal bacterial groups (acidogenic and methanogenic) remain constant at 87% and 13%, respectively. In the two‐stage reactors, the percentages of the acidogenic and methanogenic groups are 99% and 26% of the total population in the acidogenic and methanogenic reactors, respectively. In the single‐stage reactors, biomass determinations can be used to estimate microbial concentrations, and vice versa, as there is a high positive correlation between microorganism concentration and biomass. The syntrophic relationship between the bacteria involved in the anaerobic process is a possible explanation for the low values of viable population obtained in the reactors studied. Nevertheless, there is a high correlation between direct counts by epifluorescence microscopy and viable plate counts for the combined system studied.
Responses of Onondaga Lake, New York, to Early Stages of Rehabilitation: Unanticipated Ecosystem Feedbacks
Authors: Matthews D.A. , Effler S.W. , Matthews C.M. Brooks , Siegfried C.A. , Spada M.E.
Published: September 2006

Responses of polluted Onondaga Lake, New York, to early stages of a phased program to rehabilitate the lake from the effects of domestic waste inputs are documented. The analysis is based on more than 10 years of paired monitoring of the effluent (total ammonia and total phosphorus) of a wastewater treatment plant (WWTP) that discharges to the lake as well as the lake itself (including total ammonia, nitrite, total and dissolved forms of phosphorus, plankton biomass and composition, Secchi disc transparency, and zebra mussel density). Major reductions in total ammonia and total phosphorus loading relative to the preceding decade are reported for the WWTP for the November 1998 through October 1999 interval. Dramatic and, in some cases, unanticipated changes in the lake's water quality and biota in response to the reductions in loading are documented for the April to October interval of 1999 including: (1) major decreases in total ammonia concentrations and improved status with respect to ammonia toxicity standards, (2) development of dense populations of zebra mussels, (3) decreases in fall concentrations of nitrite and improved status with respect to the related toxicity standard, (4) decreases in total phosphorus and total dissolved phosphorus concentrations, and (5) a severe Microcystis (phytoplankton) bloom that caused nuisance conditions and poor clarity. The zebra mussel invasion is attributed to the reductions in total ammonia concentrations to below toxic levels. The Microcystis bloom was probably related to the abrupt increase in the zebra mussel population. Additional reductions in phosphorus loading from the WWTP will be required to limit phytoplankton production and avoid the potential for continued nuisance conditions. Potential complications in resolving lake responses to future reductions in loading associated with the zebra mussel invasion are considered.
Comparison of Fatty Acid Composition and Kinetics of Phosphorus‐Accumulating Organisms and Glycogen‐Accumulating Organisms
Authors: Wang J.C. , Park J.K. , Whang L.M.
Published: September 2006

It was demonstrated that glycogen‐accumulating organisms (GAOs) were able to compete with phosphorus‐accumulating organisms (PAOs) for acetate in a biological phosphorus removal (BPR) process, leading to a loss of BPR capability. Cellular fatty acid composition, which serves as a fingerprint for microbial identification, was used to determine microbial population change and to investigate the competition mechanisms of PAOs and GAOs. Analysis of cellular fatty acid composition indicated that PAOs grown with acetate and glucose were different species and that GAOs and PAOs grown with the same substrate were also different species. Glycogen‐accumulating organisms seemed to coexist with PAOs even in a well‐developed BPR process. The GAOs were able to accumulate more poly‐β‐hydroxybutyrate (PHB) and glycogen than PAOs during the anaerobic stage of the BPR process. The GAOs synthesized more in‐cell glycogen than PAOs. The growth rate for PAOs was always greater than that for GAOs at various acetate or glucose concentrations, while GAOs had higher acetate uptake and PHB synthesis rates than PAOs. Therefore, GAOs are thought to compete with PAOs only at long solids retention times (≤ 20 days).