bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of Nitroaromatics from Synthetic Wastewater Using Two‐Step Zero‐Valent Iron Reduction and Peroxidase‐Catalyzed Oxidative Polymerization
Authors: Mantha Ramkrishna , Biswas Nihar , Taylor Keith E. , Bewtra Jatinder K.
Published: September 2006

Degradation of nitroaromatics, which are significant environmental pollutants, is difficult to achieve. Zero‐valent iron reduction of nitroaromatics coupled with peroxidase‐catalyzed capture of the resulting anilines as a two‐step strategy for removing nitroaromatics from wastewater and process water is investigated here. The concentration range of nitroaromatics studied was that which would be present in industrial wastewater streams. Studies were done in continuous‐flow columns. The enzymatic treatment following zero‐valent iron reduction was carried out in a plug‐flow reactor using a crude preparation of the enzyme soybean peroxidase extracted from soybean hulls. The complete reaction time for the two steps was 5 to 5.5 hours. Operating parameters including pH, peroxide/substrate ratio, enzyme concentration, and alum concentration were optimized. Optimum conditions obtained were approximately neutral pH with a hydrogen peroxide/substrate molar ratio of 1.5 for all of the nitroaromatics tested. Alum concentrations between 50 and 100 mg/L were useful in removing the apparent color from the treated water.
In‐Sewer Wastewater Characterization and Model Parameter Determination Using Respirometry
Authors: do Céu Almeida Maria , Butler David
Published: September 2006

Experimental determination of wastewater characteristics and model parameters is required for robust modeling of in‐sewer processes. Respirometric assays can be used to determine some of the model parameters, thus reducing the number of model parameters to be determined by model calibration and verification. However, the model structure has to be considered for this purpose. The model used consists of three main modules, namely hydrodynamics, advection and dispersion, and biochemical processes, and is applicable in sewers under aerobic dry‐weather flow conditions. A procedure is proposed to determine important chemical oxygen demand (COD) fractions and model parameters for biochemical processes. Cumulative oxygen utilization proves to be useful for process identification, providing extra information on substrate availability during the assay. While the values obtained for both COD fractions and parameters depend on the model structure adopted, the procedure used can easily be adapted to other model formulations.
Significance of Aqueous Cation Composition on Heavy Metal Mobility in a Natural Clay
Authors: Lim Teik‐Thye , Tay Joo‐Hwa , Teh Cee‐Ing
Published: September 2006

Heavy metal mobility in soils is influenced by various soil variables and environmental factors, including the composition of the soil‐aqueous phase. This study used the sequential extraction technique to study how major cations could affect heavy metal sorption and speciation in a natural clay. The sorption of Zn, Pb, and Cd by the soil in the presence of Na+ and Ca2+ and the resulting metal speciation in the sorbed phases were examined. Sorption experiments were performed at pH levels of 3 to 8. Sorptions occurring in both single and multiple heavy metal systems were investigated. The results show that Na+ and Ca2+ significantly inhibited Zn, Pb, and Cd sorption in the acidic pH range only. The reduction in the exchangeable sorption was responsible for a large part of the reduction in the total Zn, Pb, and Cd sorption in the presence of Na+ and Ca2+. Specific adsorptions of heavy metals in other fractions of sorbed phases were only marginally affected by the composition of cations. The reduction in the exchangeable sorption increased with increasing concentration of Na+ and Ca2+. In the presence of a major cation, the competitive adsorption among the heavy metals seemed to have only a minor effect on individual heavy metal sorption.
The Effect of Storage and Lag Time on MS2 Bacteriophage Susceptibility to Ultraviolet Radiation
Authors: Jolis Domènec
Published: September 2006

The susceptibility of MS2 bacteriophage suspensions to UV radiation was assessed using a collimated beam technique. Storage of MS2 bacteriophage cultures at 4 °C resulted in a decrease in phage susceptibility to UV radiation over time. After 18 days, the level of MS2 bacteriophage inactivation achieved for the range of UV doses tested decreased by 0.7 to 1.1 logs, but remained constant after that point. Changes in the protein coat of the bacteriophage, a decrease in viability over time, and an increase in coagulation may have played a role in the observed susceptibility decrease. A 2‐hour lag time between the preparation of the MS2 suspension and the irradiation test also resulted in a decrease in phage susceptibility.
Modeling of Nitrification Inhibition with Aniline in Suspended‐Growth Processes
Authors: Khin Than , Gheewala Shabbir H. , Annachhatre Ajit P.
Published: September 2006

Nitrification inhibition due to aniline was investigated in completely mixed suspended‐growth, batch, and continuous processes. Synthetic wastewater was used with aniline as the carbon source. The experiments were conducted at aniline concentrations inhibitory to nitrifier organisms. In the batch tests, degradation took place rapidly (within 4 to 6 hours) for initial aniline concentrations below 100 mg/L, with nitrification picking up as soon as the aniline concentration decreased to less than 3 to 4 mg/L. For initial aniline concentrations of 250 mg/L and higher, complete nitrification did not take place even though the aniline concentration decreased to less than 3 to 4 mg/L. This observation indicated nitrifier inhibition due to aniline. In the continuous experiments, a hydraulic residence time of 8 to 24 hours and a solids retention time of 8 to 24 days were maintained. Complete nitrification took place at bulk aniline concentrations less than 0.5 mg/L, while at higher aniline concentrations, nitrification inhibition took place. The inhibitory effect of aniline on the nitrification process was modeled using uncompetitive inhibition kinetics. Modeling of batch processes yielded the value for the inhibition constant for aniline, Ki, as 3.3 mg/L. Modeling of continuous processes yielded criteria for stable process operation for nitrification under inhibitory conditions, which were also confirmed through experimental results.
Process Kinetics of Upflow Anaerobic Sludge Bed Reactors Treating Inhibitory Substrate
Authors: Jih Charng‐Gwo , Huang Ju‐Sheng , Huang Shin‐Yen
Published: September 2006

A kinetic model that accounts for the distributed fraction of methanogens (f) and granule‐size distribution of upflow anaerobic sludge bed (UASB) reactors is proposed. In addition, the anaerobic degradation of phenol in four UASB reactors with various superficial flow velocity (us = 0.5, 1.0, 2.0, and 4.0 m/h) was performed to generate experimental data. When using the proposed kinetic model, the calculated residual concentrations of phenol, volatile fatty acids, and chemical oxygen demand are in fairly good agreement with the experimental data. With an increase in either us or volumetric loading, the granule size of the UASB reactor increases. The experimental f values decrease with an increase in volumetric loading; the f values in the lower and middle part of the sludge bed tend to be larger than those in the upper part of the sludge bed.
Equilibrium and Kinetics of Color Removal from Dye Solutions with Bentonite and Polyaluminum Hydroxide
Authors: Kacha S. , Derriche Z.
Published: September 2006

Wastewater from the textile industry contains soluble dyes that are toxic and particularly difficult to remove. A promising low‐cost treatment, however, is use of polyaluminum hydroxide associated with bentonite. At suitable conditions, this process is able to efficiently remove color from solutions containing mixtures of soluble acid azo dyes and produce easily settleable sludge. The removal mechanism, which is believed to involve adsorption or precipitation and weak pH variations, is not well understood. With the overall reaction being second order, two elementary first‐order reactions could be assumed. The equilibrium removal is a decreasing function of the temperature. However, this effect is weak and decreases when the dye concentration increases. At usual values of concentration in textile wastewater, this effect can be neglected. The resulting solid compound is particularly resistant to mechanical stress. Moreover, color was significantly released at pH greater than 8. Sodium ions have no influence on the compound stability, which reinforces the assumption of the involvement of an adsorption process.
The Use of a Genetically Engineered Pseudomonas Species (Shk1) as a Bioluminescent Reporter for Heavy Metal Toxicity Screening in Wastewater Treatment Plant Influent
Authors: Ren Shijin , Frymier Paul D.
Published: September 2006

Heavy metals are known to be inhibitory and toxic to the activated‐sludge microbial community in biological wastewater treatment plants. Toxicity screening of aqueous mixtures of these heavy metal ions in plant influent could use both chemical and biological methods. As a biological method, luminescent bacterial bioreporters offer the advantages of a simple test procedure and rapid response. Current biologically based methods for screening aqueous streams for toxicity are labor‐intensive, inaccurate, or difficult to use in continuous monitoring applications. In the present study, a system was developed that is simple and easily automated. This system is based on the bacterium Shk1, a genetically engineered bioluminescent Pseudomonad whose parent strain was originally isolated from activated sludge. Compared with other bioluminescence‐based systems (specifically, the Microtox assay), the system of the present study more accurately reflects the effects of the toxicity of common metal ions on activated‐sludge respirometry without being overly sensitive to typical constituents of wastewater. The use of Shk1 as a bioluminescent reporter for heavy metal toxicity testing for the application of wastewater treatment influent toxicity screening is presented in this study.
Effect of Water Quality Management Efforts on Wastewater Loadings During the Past Century
Authors: Hetling Leo J. , Stoddard Andrew , Brosnan Thomas M. , Hammerman Diane A. , Norris Theresa M.
Published: September 2006

The history of wastewater discharges to the Hudson River watershed from Troy, New York, to the New York City Harbor was traced from 1900 to 2000. The parameters studied include population, flow, type of treatment, biochemical oxygen demand, suspended solids, total nitrogen, and total phosphorus. This paper details a methodology for estimating historic loadings where data are lacking. The data show dramatic changes in wastewater loadings. There has been a continued increase in wastewater flow and population over the past century but a decrease in contaminant loading during the last 25 years. The reduction in effluent loads is directly related to state and federal water quality management programs and the substantial public and private investment made in upgrading point source water pollution control infrastructure. A comparison of point with nonpoint source loads shows that although nonpoint sources are now a significant contributor of contaminants to the river, point sources remain as major sources of total nitrogen and total phosphorus.
Determining Critical Flow Conditions for Chloride Impairment in an Effluent‐Dominated, Storm‐Peaking, Western U.S. Stream
Authors: Duke L. Donald , Erickson Elizabeth
Published: September 2006

Extensive agricultural land use and intensive urban residential growth of the Calleguas Creek, California, watershed has increased chloride load and impaired beneficial uses. The hydrology of the watershed is typical of the semiarid U.S. West in that nearly all rainfall occurs in a small number of discrete storm events that each produces peak discharges of a duration of several days or less; conversely, during the dry weather season, discharge has historically been near zero. Currently, a year‐round flow is sustained by two factors: base line flow sustained by discharges from publicly owned treatment works (POTWs) and increased groundwater discharge from a shallow water table elevated by intensive agricultural irrigation (deep groundwater basins used for water supply have declined into overdraft). Water quality impairment of Calleguas Creek increases during low‐flow days, but cannot be defined seasonally because days not influenced by storm discharge occur at substantial proportions during all months. Impairment is greatest not during lowest flows, which are dominated by POTW effluent, but when groundwater and other nonpoint sources are highest, thereby contributing chloride load disproportionately to their flow. The highest nonstorm days are identified through cumulative frequency of mean daily discharge (MDD) as the transition from nonstorm conditions (described by normal distribution) to storm conditions (described by log‐normal distribution). Transition occurs at approximately the 80th to 85th percentile MDD at three Calleguas Creek locations. Critical conditions for chloride impairment are defined as volumetric flow at those percentiles of cumulative MDD distribution.
The Effect of pH on the Decomposition of Hydrophenols in Aqueous Solutions by Ultraviolet Direct Photolysis and the Ultraviolet–Hydrogen Peroxide Process
Authors: Shen Yung‐Shuen , Lin Chi‐Chang
Published: September 2006

The decomposition of catechol (o‐hydrophenol) and resorcinol (m‐hydrophenol) in aqueous solution by 254‐nm UV direct photolysis and the UV–hydrogen peroxide (H2O2) process under various solution pH values was studied. The light absorbance and photolytic properties of catechol and resorcinol were found to be highly dependent on solution pH and can be adequately described with a three‐species distribution model. For the UV–H2O2 process, the individual contribution to the decomposition of pollutants by direct photolysis and indirect hydroxyl radical destruction was differentiated by studying the linear addition of UV light absorbance of various reactant species. The contribution to the decomposition of the two hydrophenols by hydroxyl radical destruction was more than 95% in acidic and neutral solutions for treatment with the UV–H2O2 process.
Investigation of Corrosion Caused by Constituents of Refinery Wastewater Effluent Used as Circulating Cooling Water
Authors: Zhang Zhongzhi , Song Shaofu , Huang Jie , Ji Lin , Wu Fangyun
Published: September 2006

The corrosion rate of steel plate using single‐factor, multifactor, and complex water systems was investigated via refinery wastewater effluents used as circulating cooling water. The results show that the primary corrosion factors of steel depend on the characteristics of the ions, the formation of the oxidized coating, the diffusion of dissolved oxygen, and other complex factors, although ions such as chloride, calcium, and carbonate play an important role. The corrosion rate of carbon steel exhibits two trends: The corrosion rate is high at low conductivity, increases to a maximum, and then decreases and becomes stable with increasing conductivity, as is the case with chloride, sulfate, nitrate and calcium ions. On the other hand, the corrosion rate is highest at low conductivity and then decreases and becomes stable with increasing conductivity, as is the case with carbonate, silicate, and sodium nitrate ions. Research results indicate that the anticorrosive ability is minimal at low conductivity; but is excellent at high conductivity. Pretreatment of low‐conductivity water using air flotation and clarification to decrease the concentrations of chloride, calcium, and carbonate ions to a suitable level to satisfy the anticorrosion requirements is required. However, it is not necessary to significantly reduce the salt concentration or conductivity of the water by osmosis or ion exchange to obtain an anticorrosion effect when reusing wastewater effluents as circulating cooling water.
Representation, Dispersion, and Variation of Bacterial Indicators in the Coastal Waters of Nagore (East Coast of India)
Authors: Mohandass C. , Bharathi P. A. Loka
Published: September 2006

The occurrence of bacterial indicators in the coastal waters of Nagore on the east coast of India was studied during two monsoon and nonmonsoon cycles from 1995 to 1996. Proteus/Klebsiella, Vibrio parahaemolyticus, and total coliforms were typically present at a mean level of 109 colony‐forming units/g dry sediment, whereas other indicators such as Salmonella, Shigella, and V. cholerae were at the 105 level. In the water column, total coliforms and Salmonella were 2 to 3 orders of magnitude lower than in sediment. Higher numbers of indicators were retrieved at 10‐ and 15‐m depth lines than at a 5‐m depth line. While southwest monsoon caused increased bacterial input to the coastal sediment of Nagore, cyclonic effect on indicators was observed only in the water samples. Although physicochemical parameters did not influence the variation in coliform population significantly, most of the indicators in the sediment showed significant negative correlation with chlorophyll a, indicating an inverse relationship between them. With ever increasing development of Nagore, nonpoint sources of pollution may become a serious problem. Continued monitoring of these groups of bacteria over longer periods of time would help develop models for their regulation and may suggest remedial measures.
Water Quality Improvement through Bioretention: Lead, Copper, and Zinc Removal
Authors: Davis Allen P. , Shokouhian Mohammad , Sharma Himanshu , Minami Christie , Winogradoff Derek
Published: September 2006

Intensive automobile use, weathering of building materials, and atmospheric deposition contribute lead, copper, zinc, and other heavy metals to urban and roadway runoff. Bioretention is a low‐impact‐development best management practice that has the potential to improve stormwater quality from developed areas. The practice represents a soil, sand, organic matter, and vegetation‐based storage and infiltration facility used in parking lots and on individual lots to treat runoff. Investigations using pilot‐plant laboratory bioretention systems and two existing bioretention facilities documented their effectiveness at removing low levels of lead, copper, and zinc from synthetic stormwater runoff. Removal rates of these metals (based on concentration and total mass) were excellent, reaching close to 100% for all metals under most conditions, with effluent copper and lead levels mostly less than 5 μg/L and zinc less than 25 μg/L. Somewhat less removal was noted for shallow bioretention depths. Runoff pH, duration, intensity, and pollutant concentrations were varied, and all had minimal effect on removal. The two field investigations generally supported the laboratory studies. Overall, excellent removal of dissolved heavy metals can be expected through bioretention infiltration. Although the accumulation of metals is a concern, buildup problems are not anticipated for more than 15 years because of the low metal concentrations expected in runoff.
Making Classifying Selectors Work for Foam Elimination in the Activated‐Sludge Process
Authors: Parker Denny , Geary Steve , Jones Garr , McIntyre Lori , Oppenheim Stuart , Pedregon Vick , Pope Rod , Richards Tyler , Voigt Christine , Volpe Gary , Willis John , Witzgall Robert
Published: September 2006

Classifying selectors are used to control the population of foam‐causing organisms in activated‐sludge plants to prevent the development of nuisance foams. The term, classifying selector, refers to the physical mechanism by which these organisms are selected against; foam‐causing organisms are enriched into the solids in the foam and their rapid removal controls their population at low levels in the mixed liquor. Foam‐causing organisms are wasted “first” rather than accumulating on the surface of tanks and thereby being wasted “last”, which is typical of the process. This concept originated in South Africa, where pilot studies showed that placement of a flotation tank for foam removal prior to secondary clarifiers would eliminate foam‐causing organisms. It was later simplified in the United States by using the aeration in aeration tanks or aerated channels coupled with simple baffling and adjustable weirs to make continuous separation of nuisance organisms from the mixed liquor.
Simazine and Metolachlor Removal by Subsurface Flow Constructed Wetlands
Authors: George Dennis , Stearman G. Kim , Carlson Kristofer , Lansford Stacey
Published: September 2006

A subsurface flow constructed wetlands system was used in this pilot‐scale field study to treat runoff from a container nursery. The goal of the study was to determine the statistical significance of certain factors on the removal of simazine (2‐chloro‐4,6‐bis[ethylamino]‐s‐triazine) and metolachlor (2‐chloro‐N‐[2‐ethyl‐6‐methylphenyl]‐N‐[2‐methoxy‐1‐methylethyl] acetamide). The factors analyzed included the hydraulic flowrate, media depth, cell aspect ratio, and the presence or absence of Scirpus validus. Analysis of variance using the general linear model procedure determined that vegetation and flowrate significantly (α = 0.05) affected herbicide mass removal. The results showed that vegetated subsurface flow cells generally remove more simazine and metolachlor than nonvegetated cells. Decreasing the hydraulic loading rate and, therefore, the areal simazine mass loading rate to vegetated cells from 1659 to 415 mg/m2 caused an increase in the percentage of total mass removed from approximately 60 to 96%. Similarly, metolachlor mass removal percentage increased from approximately 62 to 96% when the areal mass loading to vegetated cells decreased from 1037 to 260 mg/m2. Media depth and aspect ratio did not significantly (α = 0.05) affect effluent simazine and metolachlor concentrations. Peak effluent metolachlor concentrations were less than 300 μg/L from vegetated cells receiving hydraulic loading rates of 204 and 102 m3/d·ha. Peak simazine concentrations in the effluent of vegetated cells receiving similar hydraulic loadings were approximately 1400 and 750 μg/L (204 and 102 m3/d·ha), respectively.
Preferential Transport of Cryptosporidium parvum Oocysts in Variably Saturated Subsurface Environments
Authors: Darnault Christophe J. G. , Garnier Patricia , Kim Young‐Jin , Oveson Kristina L. , Steenhuis Tammo S. , Parlange J.‐Yves , Jenkins Michael , Ghiorse William C. , Baveye Philippe
Published: September 2006

When oocysts of the protozoan Cryptosporidium parvum contaminate drinking water supplies, they can cause outbreaks of Cryptosporidiosis, a common waterborne disease. Of the different pathways by which oocysts can wind up in drinking water, one has received little attention to date; that is, because soils are often considered to be perfect filters, the transport of oocysts through the subsoil to groundwater is generally ignored. To evaluate the significance of this pathway, a series of laboratory experiments investigated subsurface transport of oocysts. Experiment 1 was carried out in a vertical 18‐cm‐long column filled either with glass beads or silica sand, under conditions known to foster fingered flow. Experiment 2 involved undisturbed, macroporous soil columns subjected to macropore flow. Experiment 3 aimed to study the lateral flow on an undisturbed soil block. The columns and soil samples were subjected to artificial rainfall and were allowed to reach steady state. At that point, feces of contaminated calves were applied at the surface along with a known amount of potassium chloride to serve as a tracer, and rainfall was continued at the same rate. The breakthrough of oocysts and chloride, monitored in the effluent, demonstrate the importance of preferential flow on the transport of oocysts. Compared with chloride, peak oocyst concentrations were not appreciably delayed and, in some cases, occurred even before the chloride peak. Recovery rates for oocysts were low, ranging from 0.1 to 10.4% of the oocysts originally applied on the columns. However, the numbers of oocysts present in the effluents were still orders of magnitude higher than 10 oocysts, the infectious dose considered by the U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, to be sufficient to cause Cryptosporidiosis in healthy adults. These results suggest that the transport of oocysts in the subsurface via preferential flow may create a significant risk of groundwater contamination in some situations.
Examination of Mechanisms for Odor Compound Generation During Lime Stabilization
Authors: Kim Hyunook , Murthy Sudhir , Peot Christopher , Ramirez Mark , Strawn Mary , Park Chul‐Hwi , McConnell Laura L.
Published: September 2006

Lime‐stabilized biosolids produced from a wastewater treatment plant often emit odors, especially those described as “fishy” and “decaying”. These odors can generate public opposition to biosolids land‐application programs even though they represent an environmentally friendly recycling of organic material that is beneficial to the agricultural industry. Therefore, it is critical to examine the controlling factors involved in odor production during the lime stabilization process. Results from preliminary experiments examining added polymer and protein material to dewatered limed biosolids show increased trimethylamine (TMA) production with further increases in 1‐hour and 4‐hour storage times prior to liming. Further experiments with water‐silica slurry reaction media reveal that enzymatically facilitated degradation of polymer and protein is the overriding factor in TMA and dimethyldisulfide (DMDS) production. It is hypothesized that macromolecules such as polymer and proteins in biosolids are first broken down enzymatically, upon which the addition of lime causes TMA and DMDS to be released.
Relative Efficacy of Intrinsic and Extant Parameters for Modeling Biodegradation of Synthetic Organic Compounds in Activated Sludge: Steady‐State Systems
Authors: Magbanua Benjamin S. , Smets Barth F. , Bowyer Rebecca L. , Rodieck Allison G. , Sanders Richard W. , Sowers William W. , Stolze Stephanie B. , Grady C.P. Leslie
Published: September 2006

The performance of intrinsic and extant kinetic parameters as predictors of synthetic organic compound (SOC) concentration in biotreatment systems operated at steady state was evaluated. Two laboratory‐scale, completely mixed activated‐sludge systems were sampled on a routine basis, and SOC concentrations were quantified using gas chromatography with flame‐ionization detection coupled with solid‐phase microextraction for analyte concentration. At the same time, intrinsic and extant respirometric tests were performed periodically, and the kinetic parameter estimates obtained were used to predict effluent SOC concentrations for comparison with the measured values. Out of 28 comparisons that could be made between intrinsic and extant predictions, extant parameters were superior in 27 cases and intrinsic parameters were comparable, at best, to extant parameters in the remaining case. Given their superior performance and relative ease of measurement, extant parameters are preferable for use in design and operational decision‐making.
Simultaneous Biological Nutrient Removal: Evaluation of Autotrophic Denitrification, Heterotrophic Nitrification, and Biological Phosphorus Removal in Full‐Scale Systems
Authors: Littleton Helen X. , Daigger Glen T. , Strom Peter F. , Cowan Robert A.
Published: September 2006

Simultaneous biological nutrient removal (SBNR) is the biological removal of nitrogen and phosphorus in excess of that required for biomass synthesis in a biological wastewater treatment system without defined anaerobic or anoxic zones. Evidence is growing that significant SBNR can occur in many systems, including the aerobic zone of systems already configured for biological nutrient removal. Although SBNR systems offer several potential advantages, they cannot be fully realized until the mechanisms responsible for SBNR are better understood. Consequently, a research program was initiated with the basic hypothesis that three mechanisms might be responsible for SBNR: the reactor macroenvironment, the floc microenvironment, and novel microorganisms. Previously, the nutrient removal capabilities of seven full‐scale, staged, closed‐loop bioreactors known as Orbal oxidation ditches were evaluated. Chemical analysis and microbiological observations suggested that SBNR occurred in these systems. Three of these plants were further examined in this research to evaluate the importance of novel microorganisms, especially for nitrogen removal. A screening tool was developed to determine the relative significance of the activities of microorganisms capable of autotrophic denitrification and heterotrophic nitrification‐aerobic denitrification in biological nutrient removal systems. The results indicated that novel microorganisms were not substantial contributors to SBNR in the plants studied. Phosphorus metabolism (anaerobic release, aerobic uptake) was also tested in one of the plants. Activity within the mixed liquor that was consistent with current theories for phosphorus‐accumulating organisms (PAOs) was observed. Along with other observations, this suggests the presence of PAOs in the facilities studied.
High Nitrite Buildup During Nitrification in a Rotating Disk Reactor
Authors: Antileo Christian , Roeckel Marlene , Wiesmann Udo
Published: September 2006

Incomplete nitrification with high nitrite accumulation has three practical advantages: lower oxygen consumption, less need for organics for denitrification, and lower sludge production during denitrification. Nitrification leading to high nitrite formation was experimentally studied in a continuous single rotating disk reactor (RDR) and compared to a modeled continuous completely stirred tank reactor (CSTR). The results of this model show that to accumulate nitrite greater than 50% at oxygen levels higher than 3.5 mg O2/L, pH levels higher than 8.5 and 9.0 are required for a CSTR with and without cell washout, respectively. For a CSTR without cell washout at pH 7 and 1 mg O2/L, it was predicted that a nitrite accumulation less than 5% could be reached. Conversely, for a partially submerged continuous RDR without any additional aeration supply (already at pH 7 and 1.3 mg O2/L), high nitrite accumulation (more than 75%) was achieved and the influence of pH from 7 to 9 was not significant. This difference is believed to be caused by mass transfer. In addition, nitrification was observed to occur under oxygen transport limitation for a totally submerged continuous RDR.
Detection of Infectious Human Adenoviruses in Tertiary‐Treated and Ultraviolet‐Disinfected Wastewater
Authors: Thompson Shawn S. , Jackson James L. , Suva‐Castillo Mila , Yanko William A. , El Jack Ziad , Kuo Jeff , Chen Ching‐Lin , Williams Fred P. , Schnurr David P.
Published: September 2006

A pilot‐scale study investigating the use of low‐pressure, high‐intensity UV radiation for disinfection of urban wastewater was conducted. The inactivation of coliform bacteria, wastewater‐indigenous enteric viruses, seeded poliovirus, and seeded F‐specific coliphage was studied. During the course of the pilot study, infectious human adenoviruses were isolated from 15 of 16 large‐volume samples of UV‐disinfected secondary‐ and tertiary‐treated wastewater. Half of the tertiary‐treated, UV‐disinfected effluent samples from which the adenoviruses were isolated had total coliform concentrations that complied with California's Water Recycling Criteria. To determine the relative UV resistance of the adenovirus isolates, purified viruses were seeded into tertiary‐treated wastewater and exposed to low‐pressure, high‐intensity, collimated UV radiation. A dose of approximately 170 mW‐s/cm2 was required to achieve 99.99% inactivation. These findings suggest that UV doses effective at meeting certain wastewater regulations for total coliform bacteria may not provide suitable inactivation of the UV‐resistant human adenoviruses.
Decolorization of the Dye, Reactive Blue 19, Using Ozonation, Ultrasound, and Ultrasound‐Enhanced Ozonation
Authors: Lall Raman , Mutharasan Raj , Shah Y. T. , Dhurjati Prasad
Published: September 2006

Reactive dyes constitute a significant portion of colorants used in industries ranging from the textile industry to the paper industry. In most cases, the effluent streams from textile plants are highly colored, and treatment methods for dye decolorization such as chemical oxidation need to be explored. The oxidation processes investigated in this study are those of ozonation, ultrasound, and ultrasound‐enhanced ozonation. The oxidation of an anthraquinone dye was studied under conditions of varying ultrasonic power, dye concentration, ozone concentration, pH, and temperature. Laboratory experiments were performed using a semibatch reactor by ozonating dye samples with and without ultrasound. Under conditions of constant ultrasonic radiation and continuous gas application, decolorization rates have been enhanced by ultrasound. The apparent first‐order rate constants increased between 35 and 204% for the ultrasonic power inputs between 40 W/L and 120 W/L compared with ozonation alone.The effects of ultrasonic power input on the gas‐liquid mass‐transfer coefficient were also investigated and the results indicate that an increase in ultrasonic power input increases the mass‐transfer coefficient. The mass‐transfer coefficient increased between 89 and 93% for ozone inlet concentrations between 5.4 and 9.4 mg/L at an ultrasonic power of 120 W/L compared with ozonation alone. The reactions of the dye with ultrasound‐enhanced ozone occurred through the hydroxyl radical pathway.
Catalytic Wet Oxidation: Mathematical Modeling of Multicompound Destruction
Authors: Yang J. , Hand D. W. , Hokanson D. R. , Crittenden J. C. , Oman E. J.
Published: September 2006

A mathematical model of a three‐phase catalytic reactor, CatReac, was developed for analysis and optimization of a catalytic oxidation reactor that is used in the International Space Station potable water processor. The packed‐bed catalytic reactor, known as the volatile reactor assembly (VRA), is operated as a three‐phase reactor and contains a proprietary catalyst, a pure‐oxygen gas phase, and the contaminated water. The contaminated water being fed to the VRA primarily consists of acetic acid, acetone, ethanol, 1‐propanol, 2‐propanol, and propionic acid ranging in concentration from 1 to 10 mg/L. The Langmuir‐Hinshelwood Hougen‐Watson (L‐H) (Hougen, 1943) expression was used to describe the surface reaction rate for these compounds. Single and multicompound short‐column experiments were used to determine the L‐H rate parameters and calibrate the model. The model was able to predict steady‐state multicomponent effluent profiles for short and full‐scale reactor experiments.
Effect of Alkalinity Type and Concentration on Nitrifying Biofilm Activity
Authors: Biesterfeld Sidney , Farmer Greg , Russell Phil , Figueroa Linda
Published: September 2006

The effect of alkalinity on nitrifying biofilm activity was determined by collecting 21‐day‐old biofilm samples from the top of a full‐scale nitrifying trickling filter and evaluating bench‐scale nitrate plus nitrite generation rates at (1) various initial carbonate alkalinity concentrations and (2) with four types of available alkalinity: carbonate only, phosphate only, phosphate plus hydroxide, and phosphate plus carbonate. Initial carbonate alkalinity concentrations were varied between 308and 20 mg/L as calcium carbonate (CaCO3). Ammonia, nitrite, and nitrate concentrations were measured at time zero, 90 minutes, 180 minutes, and 270 minutes. Generation rates in grams of nitrogen per square meter per day were calculated for each time period and normalized against dry‐weight biomass. Generation rates were impaired at initial carbonate alkalinity concentrations of 40 mg/L and lower (as CaCO3) and were unaffected at concentrations of 45 mg/L and greater. For reactor runs with different alkalinity types, ammonia, nitrite, and nitrate concentrations were measured at time zero and at 375 minutes. The type of alkalinity, carbonate versus phosphate, affected nitrification rates. When the carbonate alkalinity was less than 45 mg/L, nitrification rates were impaired regardless of the total alkalinity concentration. This effect seems to be independent of pH for the range of 6.92 to 7.99 evaluated here. This suggests that in addition to neutralizing the acid generated by the nitrification process, a minimum level of carbonate alkalinity is necessary to meet the ammonia‐oxidizer's inorganic carbon requirement for cellular synthesis and growth.
Linking Nitrifying Biofilm Structure and Function through Fluorescent In Situ Hybridization and Evaluation of Nitrification Capacity
Authors: Biesterfeld Sidney , Russell Phil , Figueroa Linda
Published: September 2006

Fluorescent in situ hybridization (FISH) was used to quantify the ammonia‐oxidizing populations within intact biofilm samples collected from a full‐scale nitrifying trickling filter (NTF). Ammonia, nitrite, and nitrate concentrations were measured for aqueous samples taken in conjunction with biofilm samples at multiple filter depths. The ammonia removal capability of collected biofilms was evaluated by transferring the biofilms to laboratory batch reactors. Nitrate plus nitrite generation rates were calculated for the full‐scale NTF and for the bench‐scale reactors. Correlation coefficients for individual sampling events, calculated by simple linear regression of FISH signal area and nitrate plus nitrite generation rates for the full‐scale NTF, ranged from −0.882 to 0.984. Correlation coefficients obtained for FISH signal area and nitrate plus nitrite generation rates for the bench‐scale reactors ranged from 0.853 to 0.994 when using probe Nso190 and from 0.919 to 0.986 when using probe Neu23a. Occasional differences between the number of ammonia‐oxidizing bacteria quantified by the probe Nso190 versus the NEU23a probe with depth suggest that genera other than Nitrosomonas are present in the NTF.
The Effect of an Initial Anaerobic Zone on the Nutrient Requirements of Activated Sludge
Authors: Harper Willie F. , Jenkins David
Published: September 2006

Laboratory‐scale sequencing batch reactors (SBRs) operating on an acetate and casamino acids‐based synthetic wastewater were used to determine the phosphorus and nitrogen requirements of anaerobic–aerobic (AnA) and completely aerobic (CA) activated sludge. At a 4‐day mean cell residence time, AnA activated sludge had an approximately 20% lower phosphorus requirement than CA activated sludge. The difference between the “end‐of‐aerobic‐cycle” polyhydroxyalkanoate (PHA) and carbohydrate contents of the sludges indicated that the AnA activated sludge used more influent carbon than the CA activated sludge for synthesis of non‐phosphorus‐containing storage products. Nitrogen requirement experiments showed that nitrogen limitations caused significant increases in the PHA and carbohydrate content of both the AnA and CA SBRs, and the limiting nitrogen requirements of AnA activated sludge were similar to those of the CA activated sludge. These findings are part of an evaluation of the AnA process for treating nutrient‐deficient wastewaters in plants with stringent effluent nutrient requirements.
A Comparative Pilot‐Scale Study of the Performance of Conventional Activated Sludge and Membrane Bioreactors under Limiting Operating Conditions
Authors: Soriano G. Aguilera , Erb M. , Garel C. , Audic J. M.
Published: September 2006

The behavior of the conventional activated‐sludge (CAS) process was compared to that of the membrane bioreactor (MBR) process under limiting operating conditions; that is, at a low solids retention time (SRT) and hydraulic residence time (HRT). The SRT was varied from 2 to 7 days, and the HRT ranged from 5 to 18 hours. The comparison was carried out in terms of nitrification and denitrification kinetics and in terms of the carbon and nitrogen removal performance of these processes. The study involved two pilot‐scale units: a CAS unit with a 9‐m3 aeration tank and a 225‐L MBR. Both of these units were installed and run under real process conditions at a wastewater treatment plant in Evry, France. In the case of the MBR process, the specific nitrification rates, rN, and the specific denitrification rates, rDN, increased as SRT was reduced from 6.5 days to 2 days. This trend was reversed and the rN and rDN decreased only when the HRT was reduced to 5 hours. A similar behavior was observed in the case of the CAS process, although rN and rDN increased only when the SRT was reduced to as low as 4 days; below this value, the rates dropped considerably. It seems that the presence of the membrane renders the MBR more robust by preventing the washout of nitrifiers at low SRT and HRT. Besides the structure and size distribution of the MBR, flocs are more favorable to intraparticle mass trasfer than those of the CAS process and could explain the higher nitrification kinetics observed with the MBR process. In all cases, the carbon and nitrogen removal performance of the MBR process was better than that of the CAS system.
Posttreatment of Upflow Anaerobic Sludge Blanket‐Treated Industrial Wastewater by a Rotating Biological Contactor
Authors: Torkian Ayoob , Alinejad K. , Hashemian S. J.
Published: September 2006

The performance of a rotating biological contactor (RBC) for posttreatment of the slaughterhouse effluent from an upflow anaerobic sludge blanket (UASB) reactor was investigated in this study. The 280‐L, six‐stage RBC pilot plant was operated at different organic loading rates (OLRs) and biodisk speeds. The overall removal efficiencies for soluble biochemical oxygen demand (SBOD), total biochemical oxygen demand (TBOD), and total chemical oxygen demand (TCOD) decreased with increasing OLRs. Disk rotational speed did not have a significant effect on performance in the range studied. The results showed that satisfactory posttreatment to meet regulatory requirements for agricultural purposes (effluent biochemical oxygen demand of 100 mg/L) can be achieved at an OLR of 5.3 ± 2.9 g SBOD·m−2·d−1, with an SBOD removal efficiency of 85 ± 3%. Most of the organics were removed in the first three stages, with minimal contribution from the remaining stages of the RBC reactor. There was a decrease in SBOD removal efficiency to 74 ± 3% at an OLR value of 17.8 ± 2.1 g SBOD·m−2·d−1. The results for elimination capacity indicated a linear relationship with first‐stage OLRs without any signs of limitation at the range of loading rates investigated in this study. However, average first‐stage elimination capacity rates of 4.8 and 3.8 g·m−2·d−1 at OLR values of 17.8 and 11 g SBOD·m−2·d−1 were relatively lower than previous studies of RBC performance using domestic or industrial wastewater without anaerobic pretreatment. It was suggested that the lower elimination capacity rates were due to the fact that a smaller fraction of UASB effluent was biodegradable as reflected in TBOD/TCOD ratios of 0.47 ± 0.04.
Virus Removal from Wastewater in a Multispecies Subsurface‐Flow Constructed Wetland
Authors: Vidales Juan A. , Gerba Charles P. , Karpiscak Martin M.
Published: September 2006

Virus removal was studied in a multispecies subsurface‐flow constructed wetland. Tracer studies and a virus survival test were conducted using bromide and bacteriophage PRD1 that were simultaneously added into a 6‐year‐old gravel‐filled wetland. The estimated dimensionless variance and the observed bromide breakthrough curve suggest a plug‐flow reactor with some dispersion. Most of the PRD1 was removed during the first 4 days; however, the PRD1 background concentration was not reached by the end of the study. Average bacteriophage removal was 98.8%, whereas bromide mass recovery was 75%. The removal rate of PRD1 was estimated to be −1.17 d−1; in contrast, its inactivation rate in situ for a 12.4‐day period was −0.16 d−1. Apparently, virus removal is governed by an initial irreversible attachment followed by a comparatively long inactivation period. This study suggests that a subsurface‐flow wetland can decrease the virus load by approximately 99% with a 5.5‐day detention time.
Marine Macroalgae as Biosorbents for Cadmium and Nickel in Water
Authors: Ofer Raize , Yerachmiel Argaman , Shmuel Yannai
Published: September 2006

Experimental studies showed that brown marine algae, Sargassum vulgaris and Padina pavonia, can be used to develop an efficient biosorbent for heavy metal removal from aqueous solutions. Sargassum vulgaris exhibited high uptake capacities for cadmium (0.9 to 1.1 mmol Cd/gr) and nickel (0.85 to 1 mmol Ni/gr) that are higher than those of other types of biomass and powdered activated carbon, while P. pavonia showed a broader range of nickel and cadmium uptake capacities (0.7 to 1 mmol Ni/gr and 0.8 to 1.1 mmol Cd/gr). The metal adsorption and desorption processes were rapid, with 70% of the sorption and desorption completed within 10 minutes. The equilibrium data for both algae fit well to Langmuir and Freundlich isotherm models. More than 90% desorption of adsorbed metals from the algae was achieved by hydrochloric acid and ethylenediaminetetraacetic acid (1:1 molar ratio). After eight to nine adsorption and desorption cycles, S. vulgaris showed a 15 to 35% decrease in metal uptake capacities; P. pavonia showed a higher decrease of 50 to 60%.
Controlling Biosolids Phosphorus Content in Enhanced Biological Phosphorus Removal Reactors
Authors: Chaparro Sean K. , Noguera Daniel R.
Published: September 2006

A methodology to reduce the phosphorus content of biosolids produced by enhanced biological phosphorus removal treatment plants was studied. The process consists of mixing phosphate‐rich waste activated sludge (WAS) with either primary sludge or the supernatant from a primary‐sludge gravity thickener under anaerobic conditions to induce the release of phosphate from WAS. The solubilized phosphate could then be chemically sequestered and removed from the biosolids. Bench‐scale phosphate release experiments were conducted with sludge from the Nine Springs Wastewater Treatment Plant (Madison, Wisconsin) at different mixing ratios. A WAS/primary sludge or WAS/supernatant mixing ratio of 1:1 (by volume) resulted in the highest phosphate release in the batch tests. For experiments with less than 50% WAS (by volume), the total phosphate release was directly proportional to the amount of WAS added. When the mixture contained more than 50% WAS, total phosphate release was limited by the volatile fatty acids (VFAs) available. For the Nine Springs plant, optimal biosolids phosphorus could be achieved using a primary sludge/WAS mixing ratio of 1.02 kg volatile suspended solids (VSS)/kg VSS or a supernatant VFA/WAS mixing ratio of 0.028 kg VFA/kg VSS. The expected reduction in phosphorus content would be 35 and 32% if primary sludge or supernatant, respectively, were used.
Factors Affecting Ballasted Flocculation Reactions
Authors: Young James C. , Edwards Findlay G.
Published: September 2006

Ballasted flocculation represents a relatively new technology that shows promise of bringing improvements to the field of water and wastewater treatment. Ballasted flocculation involves the addition of a ballasting agent (high‐density microsand, sp gr = 2.65) to a chemically stabilized and coagulated suspension of particulate solids. Tests were conducted to determine the effect of eight independent parameters on the settling velocity of the resulting floc. Measurements showed settling velocities ranging from approximately 100 m/h for 0.5‐mm diameter particles to as high as 380 m/h for particles having effective diameters up to 7 mm. Settling velocities for discrete microsand particles and discrete ballasted flocs were found to fit conventional settling theory with reasonable accuracy. The most important factors contributing to the benefits of ballasted flocculation are the large floc sizes that can be maintained, the greater roundness of the floc particles, and a lower shape factor for the ballasted floc, which all contribute to higher settling rates. Higher settling rates allow for substantially smaller sedimentation units and decreased capital costs.