bluuebunny/crossref_metadata_2025 huggingface dataset:
Multilevel protocol for assessing the fate and effect of toxic organic chemicals in anaerobic treatment processes
Authors: Young James C. , Tabak Henry H.
Published: February 2012

ABSTRACT:  A multilevel protocol has been developed to provide a consistent and repeatable means of determining fate and effect of toxic organic chemicals in anaerobic wastewater treatment processes. Level I consists of a three‐step screening protocol for assessing toxicant effect on organic cosubstrate transformations. Level II is a cosubstrate kinetics protocol designed to reveal the effect of toxic organic chemicals on the kinetics of acetogenic and methanogenic transformations. Level III is a toxicant degradation kinetics protocol. The protocol test approach represents a composite of conditions and procedures used by a number of investigators of anaerobic reactions. It permits a wide latitude in specific reactor sizes and types and in measurement techniques as long as the basic culture, chemical and physical environment, and substrates are maintained as prescribed. Examples are presented to illustrate the type of test results that can be expected when using the protocol.
Performance of an artificial wetlands filter treating facultative lagoon effluent at Carville, Louisiana
Authors: Zachritz Walter H. , Fuller J. Wayne
Published: February 2012

ABSTRACT:  Treatment plant upgrades of existing facultative lagoon systems are rapidly incorporating constructed artificial wetlands systems to control biochemical oxygen demand (BOD) and total suspended solids (TSS). Subsurface flow wetlands or artificial wetlands filters (AWF) are being installed at many facilities throughout the U.S. Most of these systems are relatively new and extensive operational experience is lacking. This study presents an examination of the performance of a system at the U. S. Public Health Service's Gillis W. Long Hensen's Disease Control Center located in Carville, Louisiana. The AWF is designed to meet effluent standards of 10 mg/L 5‐day BOD (BOD5) and 15 mg/L TSS, based on a design flow of 568 m3/d (150 000 gpd) with a 24‐hour detention time. The AWF has a 0.69‐m depth of 2–8 cm rock with a 15cm pea gravel cap and swamp potato (Sagittaria latifola) and duck potato (Sagittaria falcata) planted on 30‐cm centers. The study was initiated in the spring of 1988 and samples were collected twice a week from seven sampling stations and analyzed for BOD5, flow rates, temperature, pH, TSS, and VSS. The results indicated that the AWF was effective at controlling BOD5 and TSS within design standards over a range of hydraulic fluctuations of 163–871 m3/d (43200–230000 gpd). The AWF removed 62 and 76.5% of the influent BOD5 and TSS, respectively. Analysis of samples taken from sample wells located in the first one‐third of the filter indicated 40 and 60% removal of BOD5 and TSS, respectively. Step flow introduction of wastewater could better optimize filter bed volumes and maintain uniform plant growth. For new AWF systems designs, greater length to width ratios could achieve the same treatment while minimizing front end clogging and ponding problems.
Effect of GAC characteristics on adsorption of organic pollutants
Authors: Sorial George A. , Suidan Makram T. , Vidic Radisav D. , Brenner Richard C.
Published: February 2012

ABSTRACT:  The impact of the characteristics of granular activated carbon (GAC) on adsorption capacity and on the potential for polymerization of phenolic compounds on the surface of GAC in the presence of molecular oxygen is evaluated in this study. Adsorption isotherm data were collected for p‐chlorophenol on five activated carbons; three manufactured from bituminous coal, one manufactured from lignite coal, and one manufactured from wood. These isotherms were collected under anoxic (absence of molecular oxygen) and oxic (presence of molecular oxygen) conditions. Higher extraction efficiencies of the carbons used in the oxic isotherms were obtained for the carbons that exhibited lower increases in capacities when compared to anoxic isotherms. Furthermore, no impact of the presence of oxygen on adsorption capacity was noted for the wood base carbon. Breakthrough curves developed for p‐chlorophenol on the five carbons studied have shown tailing effects for the carbons that demonstrated differences in capacities under oxic and anoxic conditions whereas no tailing was noticed for the wood base carbon.
Fate of volatile organic compounds in municipal activated sludge plants
Authors: Parker Wayne J. , Thompson Doug J. , Bell John P. , Melcer Henryk
Published: February 2012

ABSTRACT:  The fate of volatile organic compounds (VOCs) in municipal activated sludge plants was investigated at pilot and full scale. More than 80% of the mass flow of nonchlorinated compounds was observed to be biodegraded while less than 20% was removed by stripping. Conversely, 46% of the mass flow of chlorinated compounds was biodegraded and 47% was removed by stripping. Adsorption of VOCs onto waste sludge was not a significant removal mechanism. The pilot plant employed was found to effectively emulate the liquid‐gas phase partitioning and overall compound removals observed in a full‐scale plant. Little difference in liquid‐gas phase partitioning was observed for coarse and fine pore diffusers in spite of differing mass‐transfer characteristics as demonstrated by oxygen‐transfer measurements. This implies that equilibrium between the liquid and gas‐phase concentrations was achieved with both diffuser types. Stripping of VOCs was observed to increase with airflow; however, the extent of stripping increased at a declining rate.
Ultraviolet disinfection for wastewater reclamation and reuse subject to restrictive standards
Authors: Darby Jeannie L. , Snider Kile E. , Tchobanoglous George
Published: February 2012

ABSTRACT:  An ultraviolet (UV) disinfection system was operated under field conditions using both unfiltered and filtered secondary wastewater effluents to assess the feasibility of using UV light to meet the stringent criterion specified in the California Wastewater Reclamation Criteria (CWRC). In the unfiltered wastewater the CWRC criterion that the 7‐day median not exceed 23 total coliform/100 mL was met consistently in effluent exposed to an average UV dose of 60 mW · s/cm2 or greater. In the filtered wastewater, the CWRC criterion that the 7‐day median not exceed 23 total coliform/ 100 mL was met consistently in effluent exposed to an average UV dose of 48 mW · s/cm2 or greater. The most stringent criteria, that the 7‐day median not exceed 2.2 total coliform/ 100 mL and that the total coliform not exceed 23/100 mL in more than one sample in a 30‐day period, was met consistently in filtered effluent exposed to an average UV dose of at least 97 mW · s/cm2. Filtration of the secondary effluent clearly enhanced the performance of the UV disinfection. Filtration was effective in removing significant amounts of suspended solids, in altering the particle size distribution of the secondary effluent, and in providing a consistently high quality effluent (turbidity < 2 NTU).
Inorganic solids development in a pilot‐scale anaerobic reactor treating municipal solid waste landfill leachate
Authors: Keenan Peter J. , Iza Jon , Switzenbaum Michael S.
Published: February 2012

ABSTRACT:  A 30‐L hybrid upflow anaerobic sludge bed filter (U ASBF) reactor was operated for 9 months on‐site at a municipal solid waste landfill in western Massachusetts. Total chemical oxygen demand (COD) removals exceeded 85% at organic loading rates as great as 10 kg/m3·d. However, periodic monitoring of sludge profiles in the unpacked region indicated that the granular sludge bed was becoming compacted and mineralized. After 9 months of operation, total solids concentrations were approximately 450 g/kg, with approximately 80% of the total solids being fixed. Excessive inorganic scale accumulation on the interior reactor surfaces resulted in operational problems, and forced the eventual shutdown of the reactor. Evidence of reduced sludge activity resulting from the presence of metal precipitates indicates that pretreatment for metals removal is necessary prior to anaerobic treatment.
Sulfide toxicity in anaerobic systems fed sulfate and various organics
Authors: Maillacheruvu Krishnanand Y. , Parkin Gene F. , Peng Chen Ye , Kuo Wen‐Chien , Oonge Zablon I. , Lebduschka Vladimir
Published: February 2012

ABSTRACT:  Upflow anaerobic filters fed acetate and propionate, and completely mixed, suspended growth reactors fed acetate, propionate, lactate, and glucose were used to investigate the effect of electron donor and reactor type on the interaction between sulfate‐reducing bacteria (SRB) and methanogens. Organic loading rates of 0.25–0.50 g chemical oxygen demand (COD)/L · d were used in suspended growth systems and 1.0–5.0 g COD/L · d in filters. COD/sulfur ratios ranged from 20/1 to 2/1 for completely mixed reactors, and 20/1 to 8/1 for anaerobic filters. Results indicated that organisms involved in the conversion of lactate and glucose into simpler products were not affected by sulfide toxicity. Levels of 60–75 mg sulfur/L of hydrogen sulfide and 150–200 mg/L of dissolved sulfide (DS) caused stress in all suspended growth reactors; 100–150 mg sulfur/L of hydrogen sulfide and 200–400 mg DS/L could be tolerated in lactate and glucose systems, although with diminished COD and sulfate removal. For similar loading conditions, lactate and glucose systems had higher DS levels than acetate and propionate systems. A cyclic pattern of variation of DS and hydrogen sulfide with volatile‐acids COD (VACOD) was observed in long‐term experiments with suspended growth reactors. Anaerobic filters were able to tolerate higher DS and hydrogen sulfide levels than suspended growth reactors. A propionate‐fed filter could withstand more than 150 mg hydrogen sulfide/L of hydrogen sulfide and 1000 mg DS/L, and an acetate‐fed filter could tolerate more than 125 mg sulfur/L of hydrogen sulfide and 400 mg DS/L.
Effects of temperature and mean cell residence time on biological nutrient removal processes
Authors: McClintock Samuel A. , Randall Clifford W. , Pattarkine Vikram M.
Published: February 2012

ABSTRACT:  The effects of temperature and mean cell residence time (MCRT) on biological nitrogen and phosphorus removal were investigated by operating two pilot‐scale continuous‐flow reactors in parallel over a range of temperatures and MCRTs. One system was operated as a high‐rate Virginia Initiative Plant (VIP) biological nutrient removal (BNR) process, and the other was operated as a conventional, fully aerobic activated sludge process for comparison. Results showed that less aerobic volume was needed for complete nitrification in the BNR process than in the conventional process when conditions of temperature and MCRT were suitable for complete nitrification. However, the BNR system was more prone to nitrifier washout than the conventional system. Nitrification rates and the degree of nitrification achieved by the BNR system and the conventional system were equal when compared on the basis of aerobic MCRT. Enhanced biological phosphorus removal (EBPR) was adversely afFected by colder temperatures, with lower MCRTs being most affected. EBPR was not possible at a 5 day system MCRT and 10°C. Nitrification, however, was more sensitive to MCRT and temperature effects than EBPR under all conditions studied. Operation of the BNR process at the lowest MCRT that provided complete nitrification provided the best combined nitrogen and phosphorus removal when EBPR was chemical oxygen demand (COD)‐limited. Higher MCRTs were considered optimal when EBPR was limited by phosphorus because of lower sludge productions.
Point‐of‐entry treatment of petroleum contaminated water supplies
Authors: Malley James P. , Eliason Pamela A. , Wagler Jennifer L.
Published: February 2012

ABSTRACT:  Contamination of individual wells in rural areas from leaking petroleum storage tanks poses unique problems for regulatory agencies, utilities, and potentially responsible parties. A potential solution is the use of point‐of‐entry (POE) treatment techniques. Results indicate POE systems using aeration followed by granular activated carbon (GAC) are a viable, cost effective, short‐term solution while ground water remediation is performed or an alternate drinking water supply is secured. Selection and design of POE systems should consider variations in water usage and contaminant concentrations. Iron and manganese did not affect POE system performance at the ten sites studied. However, iron precipitation was observed and may pose problems in some POE applications. Increased concentrations of nonpurgeable dissolved organic carbon consisting primarily of methy‐t‐butyl ether (MTBE) and hydrophilic petroleum hydrocarbons were found in the raw waters but did not affect volatile organic chemical (VOC) removals by aeration or GAC. Microbial activity as measured by heterotrophic plate count significantly increased through four of the ten POE systems studied. Reliability of the POE systems will best be achieved by specifying top quality system components, educating POE users, and providing routine maintenance and VOC monitoring.
Modeling the fate of metals in municipal water pollution control plants
Authors: Monteith Hugh D. , Bell John P. , Thompson Douglas J. , Kemp Jeff , Yendt C. Mark , Melcer Henryk
Published: February 2012

ABSTRACT:  A solution of seven metal salts was dosed into batch and continuous‐flow dynamic wastewater experiments at bench‐ and pilot‐scale to calibrate a computer‐based mathematical model for predicting the fate of metals in municipal water pollution control plants (WPCPs). The model accounts for both precipitation and sorption onto primary and secondary sludges, and predicts the concentrations of metals in the primary sludge, return activated sludge, and secondary clarifier effluent. In dynamic step experiments, six of seven metals were removed substantially (55–99%) by the pilot activated sludge system. Lead and chromium were removed to the greatest extent while nickel was least removed. With the exception of nickel, a large fraction of the effluent metal concentrations were in particulate form. Below the solubility limits, a linear sorption model generally was able to simulate the observed effluent response to a step input. Sampling at a full‐scale WPCP was conducted for testing the steady‐state model's predictive capability. Except for lead, the predicted effluent concentrations agreed well with observed values.
Floc breakup in activated sludge plants
Authors: Das Debankur , Keinath Thomas M. , Parker Denny S. , Wahlberg Eric J.
Published: February 2012

ABSTRACT:  This investigation, conducted at 24 full‐scale activated sludge wastewater treatment plants, quantified the extent of floc breakup resulting from the manner in which mixed liquors in aeration basins and conveyance systems are handled. Results showed that the concentration of dispersed solids increases with increasing aeration basin mixing intensity in the case of diffused air aeration systems. Also, the beneficial effect of the tapered aeration mode of operation on the extent of flocculation was shown. In mechanically aerated basins, the location of the aerator nearest the basin discharge point was found to be critical with respect to floc integrity since the degree of solids dispersion was shown to vary inversely with distance from a mechanical aerator. The presence of elbows and free falls of less than 0.5 m in mixed liquor transport systems was found to slightly increase solids dispersion. Free falls greater than 1.2 m however, were observed to cause significant floc breakup. Shear rates normally present in conveyance pipelines resulted in net floc aggregation.
Molecular oxygen and the adsorption of phenols—effect of functional groups
Authors: Vidic Radisav D. , Suidan Makram T. , Sorial George A. , Brenner Richard C.
Published: February 2012

ABSTRACT:  This study reveals that the presence of molecular oxygen (oxic conditions) has a significant impact on the exhibited adsorptive capacity of granular activated carbon (GAC) for several phenolic compounds. The increase in the GAC adsorptive capacity under oxic conditions results from polymerization of these adsorbates on the carbon surface. The mechanism of polymer formation is through oxidative coupling of phenolic molecules. The extent of an increase in the GAC adsorptive capacity is in accordance with the ease of oxidation of these compounds. However, substituting a nitro group on the parent phenol molecule suppressed polymerization reactions and no increase in the GAC adsorptive capacity was observed under oxic conditions for these substituents.
Factors affecting dispersion of activated sludge flocs
Authors: Li Dahong , Ganczarczyk Jerzy J.
Published: February 2012

ABSTRACT:  The parameters of the power‐law and log‐normal floc size distribution models were correlated with the values of process operation factors for five, full‐scale conventional activated sludge wastewater plants. Stepwise regression was applied to investigate the combined effects of these factors and the interaction of selected factors. Factors affecting the frequency of occurrence of primary particles were examined by logistic regression and stepwise regression. It was found that the process operation factors affect the floc size distribution in a complex way, but sludge loading was the most important and statistically significant factor influencing the frequency of occurrence of primary particles (<2 μm) in mixed liquor.
Anaerobic removal of 2,4,6‐trinitrotoluene (TNT) under different electron accepting conditions: laboratory study
Authors: Boopathy Ramaraj , Wilson Marti , Kulpa Charles F.
Published: February 2012

ABSTRACT:  An attempt has been made to study the anaerobic removal of 2,4,6‐trinitrotoluene (TNT) under different electron accepting conditions by a soil bacterial consortium. The results indicated that among the different electron acceptors studied (sulfate, nitrate, and carbon dioxide), significant TNT removal was observed under nitrate reducing conditions. When there was no electron acceptor in the medium, TNT was not removed even after 60 days of incubation. Under nitrate reducing conditions, 82% of TNT was removed from the original concentration of 100 ppm of TNT. Under sulfate reducing conditions, approximately 30% of TNT was removed. When carbon dioxide was used as electron acceptor and H2 as electron donor, TNT was removed by 35%. This result indicates that TNT could be removed under anaerobic conditions when there is appropriate and adequate electron acceptor present in the soil. TNT did not serve as an electron acceptor and TNT removal was apparently achieved by co‐metabolism. The anaerobic reactions demonstrate that decontamination of TNT is possible under anaerobic conditions for TNT contaminated sites of soil and water, where aerobic treatment is not economically feasible.
Hydrogen monitoring in anaerobic sludge bed reactors at various hydraulic regimes and loading rates
Authors: Pauss André , Guiot Serge R.
Published: February 2012

ABSTRACT:  The dissolved hydrogen concentration was monitored in four laboratory‐scale upflow sludge bed reactors. The upflow velocity (υUP) differed in each reactor, providing different hydraulic regimes. Five pseudo‐steady‐state conditions were applied to the four reactors. The dissolved hydrogen concentration increased proportionally with the organic loading rates (OLR) of the reactors, to attain values as high as 20 μM, while still remaining independent of the hydraulic regime. The experimental data yielded low hydrogen mass‐transfer rates (kLa) and high ratios of the measured dissolved hydrogen concentration value to the equilibrium value calculated from the hydrogen partial pressure in the gas phase (sursaturation factor): from 0.04 to 0.46 h−1 and from 19 to 102, respectively. Also, the increase in the υUP did not affect the hydrogen kLa nor the sursaturation factor. The kLa values showed a reasonable and positive correlation with the OLR values and the gasflow rates, however no correlation was found between the sursaturation actor values and the latter parameters. This indicates that dissolved hydrogen concentration can not be predicted from hydrogen gaseous measurements in such reactors.
Bacterial leaching of toxic metals from municipal sludge: influence of sludge characteristics
Authors: Tyagi Rajeshwar D. , Blais Jean‐François , Auclair Jean‐Christian , Meunier Nathalie
Published: February 2012

ABSTRACT:  The presence of high concentrations of heavy metals in wastewater sludge is one of the most important factors that limit the application of sludge on agricultural land. In the last few years, the microbiological process of heavy metals removal from wastewater sludge has been studied in a batch mode. In the present study, the effects of metals, solids concentration, and initial pH on indigenous sulfur‐oxidizing thiobacilli growth and metal solubilization were examined. The results obtained indicate that metals removal is possible even in high sludge solids concentration (70 g/L). The rate of sulfuric acid production through the oxidation of added elemental sulfur is increased by the increased sludge solids concentration. The initial pH of the sludge (7.0–3.0) does not affect the capacity of metal leaching. The high concentration of metallic ions (Cu2+ and Zn2+) adjusted in the sludge did not greatly affect the microbiological activity of metal‐leaching bacteria. The leaching tests conducted with metal sulfides as substrate (chalcocite, galena, pyrite, sphalerite) showed that metals solubilization from sulfides occurred by an indirect mechanism (production of acid followed by metal solubilization due to the action of the acid produced). No evidence of direct oxidation of metal sulfides was observed.
Kinetics of sorption and desorption of copper(II) and lead (II) on activated carbon
Authors: Wilczak Andrzej , Keinath Thomas M.
Published: February 2012

ABSTRACT:  The rate of sorption of copper(II) and lead(II) onto activated carbons Nuchar SA and Filtrasorb 400 was observed to occur rapidly at the outset, followed by a slow and prolonged sorption. This indicates that previous sorption studies conducted for short equilibration periods likely underestimated the actual capacity of activated carbon for heavy metals. Although copper and lead ions desorbed from the activated carbon surface rapidly, the rate of desorption of lead was slower, prevailing over several days. Sorption of copper and lead ions on Nuchar SA was found to be fully reversible.
Treatability of DNT process wastewater by supercritical water oxidation
Authors: Li Lixiong , Gloyna Earnest F. , Sawicki John E.
Published: February 2012

ABSTRACT:  This study focused on the treatment of dinitrotoluene (DNT) process wastewaters by supercritical water oxidation (SCWO). Major organic components found in the DNT process wastewaters were 2‐nitrophenol, 4‐nitrophenol, 2,4‐dinitrophenol, 4,6‐dinitro‐ortho‐cresol, phenol, and dinitrotoluene. Tests were conducted using a 20‐cm3 batch reactor and two 120‐cm3/min continuous‐flow reactor systems. Separate oxidant tests employed oxygen and hydrogen peroxide. Organic destruction efficiencies of target compounds were obtained at supercritical and subcritical water conditions. Temperatures and pressures, respectively, ranged from 250°C to 500°C and 140 bar to 310 bar. The reaction times varied from 1 minute to 7 minutes. Wastewaters premixed with a biological sludge were also tested. SCWO was capable of destroying the U.S. Environmental Protection Agency (EPA) priority pollutants found in the DNT process wastewater. Under SCWO conditions, destruction efficiencies greater than 99% were achieved.
Use of Monte Carlo techniques to assess POTW compliance with EPA water quality criteria for heavy metals
Authors: Bumgardner Jim , Malone Christopher , Walker Larry F. , Shanks Robert F.
Published: February 2012

ABSTRACT:  This paper presents the results of a study (Larry Walker Associates, 1990) to determine the nature of additional controls necessary for the Sacramento Regional Wastewater Treatment Plant (Regional Plant) to comply with the numeric water quality objectives for metals recently adopted by the State of California. In addition, the impact of Regional Plant effluent on Sacramento River metals concentrations is examined, and the costs of compliance with the new objectives are estimated. Monte Carlo techniques are used to determine the ability of the Regional Plant to achieve the metals objectives and the effects of treatment plant discharge on receiving water metal concentrations. Frequency distributions of advanced treatment efficiencies, such as lime precipitation and reverse osmosis, are used to simulate effluent concentration reductions that are potentially achievable. The costs associated with the additional treatment required to meet objectives are estimated using published cost estimates for advanced treatment plants of similar size. Results show that currently, the Regional Plant does not meet objectives for cadmium, copper, mercury, and zinc. Furthermore, the additional treatments evaluated would not completely eliminate violations of the copper and mercury objectives.
Mechanistic model for facultative stabilization ponds
Authors: Colomer F. LLavador , Rico D. Prats
Published: February 2012

ABSTRACT:  In this work a 12‐parameter mechanistic model representing the biochemical interactions in facultative stabilization ponds is proposed (as an extension of the Fritz et al. [ 1979] model). An acceptable degree of fitness between the model predictions and the experimental data from the real plant was obtained. The stability of calculated concentrations with respect to small changes in the kinetic constant values of the model were also studied.
Organic loading effects on the treatment of phenolic wastewaters by sequencing batch reactors
Authors: Nakhla G. F. , Al‐Harazin I. M. , Farooq S.
Published: February 2012

ABSTRACT:  The biodegradability of high concentrations of phenol and ocresol in wastewater and the impact of these toxicants on sludge settleability was investigated. Sequencing batch reactors were utilized to treat phenol and ocresol aerobically at a hydraulic retention time of 1 day and a solids residence time of 14 days. The reactors achieved greater than 99.5% removal of phenol and o‐cresol at toxicant loadings in the ranges of 0.1‐0.8 kg phenol/m3 · d and 0.1‐0.6 kg o‐cresol/m3 · d. The average 5‐day biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) removal efficiencies were approximately 99% and 94%, respectively. High toxicant loadings were not observed to hinder the biodegradability of other waste constituents, reflected by the effluent BOD5 being consistently less than 5mg/L, or impair sludge settleability because the effluent total suspended solids (TSS) and sludge volume index (SVI) were consistently approximately 12 mg/L and 80 mL/g, respectively.
Competition between PolyP and non‐PolyP bacteria in an enhanced phosphate removal system
Authors: Čech Jakub S. , Hartman Petr , Wanner Jiři
Published: February 2012

ABSTRACT:  The competition between polyphosphate accumulating bacteria (PolyP bacteria) and a group of microorganisms not accumulating polyphosphate (tentatively named “G bacteria”) was observed in a laboratory sequencing batch reactor exhibiting enhanced biological phosphate removal (EBPR). The “G bacteria” were able to dominate the anaerobic‐oxic system even though acetate was readily available. When acetate was used as the sole source of organic carbon, however, PolyP bacteria were able to compete successfully with “G bacteria.” The molar ratio of phosphate released to acetate taken up in the anaerobic stage varied from 0 to 0.78 and depended on the ratio of the numbers of PolyP bacteria to “G bacteria” in the activated sludge.
The removal of radioactive cobalt, cesium, and iodine in a conventional municipal wastewater treatment plant
Authors: Stetar Elisabeth A. , Boston Harry L. , Larsen Ingvar L. , Mobley Michael H.
Published: February 2012

ABSTRACT:  A radiotracer study was conducted to determine removal efficiencies for cobalt, cesium, and iodine in a conventional municipal wastewater treatment plant. The study was conducted in a full‐scale facility that provides primary treatment through physical settling and secondary treatment using activated sludge. The radiotracers, 58Co and 134Cs as chlorides, and 131I as Nal, were equilibrated in raw wastewater and introduced to the treatment system as a pulse in the incoming raw wastewater. Samples of wastewater and sludge were collected and analyzed to quantify primary treatment, secondary treatment, and overall removal efficiencies. Selected samples were filtered to determine the partitioning of the tracers between the solid and liquid phases of the wastewater and sludge throughout the treatment process. In the incoming wastewater, approximately 10% of the 58Co, 7% of the 134Cs, and 3% of the I31I were associated with suspended solids. The suspended tracer fractions decreased across the treatment plant. Primary treatment resulted in the partial removal of the incoming suspended fraction with observed removal efficiencies of 8.1% and 3.0% for 58Co and 134Cs, respectively, and an estimated removal of 2% for 131I. Approximately 80% of the radiotracers in the primary treatment sludge were associated with the sludge solids. The affinity of the radiotracers for the activated sludge solids was in the following order: 58Co > 134Cs > 131I. Secondary treatment removal efficiencies of 25% and 9.4% were observed for 58Co and 134Cs, respectively. The secondary treatment removal efficiency for 131I was estimated to be 2‐3%. Overall removal efficiencies were 31%, 12%, and 3‐5% for 58Co, 134Cs, and 131I, respectively. The remaining fractions of the radiotracers remained within the soluble phase of the wastewater and were discharged in the treatment plant effluent.
Sorption of low levels of cyanide by granular activated carbon
Authors: Guo Runde , Chakrabarti Chuni L. , Subramanian Kunnath S. , Ma Xiaojie , Lu Yanjia , Cheng Jianguo , Pickering William F.
Published: February 2012

ABSTRACT:  The sorption of cyanide at levels ≤ 1 mg/L in solution by granular activated carbon (GAC) was investigated in order to define the conditions required to reduce residual levels to below the maximum acceptable concentration value specified in the Guidelines for Canadian Drinking Water Quality. The sorption process proceeded slowly with uptake continuing over a 30‐hour mixing period. The initial rate of adsorption increased with decreasing particle size of the activated carbon. In general, uptake was independent of pH except for a slight increase in the pH range of 8‐9, but increased linearly with increasing adsorbent density until the concentration of cyanide was lowered to approximately 0.3 mg/L; below 0.3 mg/L, the amount sorbed became proportional to a power‐law term of the adsorbent density. The effect of cyanide concentration on the uptake could be described by a Freundlich isotherm with the amount sorbed per unit weight of granular activated carbon being proportional to (Ce)0.13. Addition of up to 10 mg/L nitrilotriacetic acid had little effect on the amount of cyanide adsorbed; however, humic acid, Ca(II), Mg(II), Al(III), and Fe(III) reduced the cyanide uptake by 30‐50%. Possible mechanisms for cyanide sorption by GAC and their implications for water treatment have been considered. The mechanisms considered include CN− uptake by ion exchange, and sorption of cyanide as HCN molecules through formation of H‐bonds with oxygenated functional groups such as — COH.
Biological sulfide prestripping for metal and COD removal
Authors: Haas Charles N. , Polprasert Chongchin
Published: February 2012

ABSTRACT:  Organic wastes of high concentration and containing high concentrations of metals have generally been treated by a preliminary metal removal process (for example, precipitation) followed by biological treatment of the degradable component of the organic matter. It was the objective of this study to determine if a high strength waste containing metals could be treated by a precipitation‐anaerobic digestion process in which the precipitant was sulfide generated by the digestion step itself. To answer these questions, laboratory reactors were fed a synthetic medium (containing copper as the metal of interest and glucose and acetate as primary organic substrates) and operated in a semicontinuous draw and fill manner. Overall, the results of this study are encouraging and point to the potential feasibility of the process.
Wastewater treatment with complementary filter feeders: A new method to control excessive suspended solids and nutrients in stabilization ponds
Authors: Smith Daniel W.
Published: February 2012

ABSTRACT:  Zooplankton filter feed small suspended solids (SS) while filter‐feeding fish (Hypophthalmichthys molitrix) feed on large suspended particles. The combination should control SS and nutrients in wastewater stabilization ponds. The technique proposed herein maintains coexistence of zooplankton and filter‐feeding fish by excluding the fish from part of the water column. A series of 1‐m3 tanks was stocked with channel catfish (Ictalurus punctatus) alone, catfish and silver carp, or catfish and silver carp that were excluded from one‐half of the water column. The refuge permitted coexistence of high densities of zooplankton with the silver carp, and the combination of filter feeders reduced algal biomass by as much as 99% compared to controls. SS and nutrients were presumably likewise controlled. Application to stabilization ponds in series would be straightforward.
Heterogeneous photocatalytic oxidation of hazardous organic contaminants in water
Authors: Suri Rominder P. S. , Liu Junbiao , Hand David W. , Crittenden John C. , Perram David L. , Mullins Michael E.
Published: February 2012

ABSTRACT:  Photoactive catalysts, when illuminated with UV‐light, generate highly reactive radicals that can oxidize the organic contaminants in water. One method to increase the efficiency of the process, and thereby reduce the light energy requirements, is by developing more active catalysts. Several catalysts that were obtained commercially and/or prepared in the laboratory were examined for their photoactivity, and they are: Ti02, Pt‐Ti02 with platinum loading varying from 0.5% to 10% by weight, SrTi03, and 1.5% NiO‐SrTi03. The organic compounds used to identify the best catalyst were trichloroethylene (TCE), toluene, methyl ethyl ketone (MEK), salicylic acid, and 2,4‐dichlorophenol, with initial concentration varying from 0.1 to 10.0 mg/L. This study also examined the impact of catalyst dosage, organic compound and its initial concentration, and electron acceptor concentration on the reaction kinetics. The process efficiency for mineralization of organic compounds is also evaluated. The results demonstrate that the activity of photocatalysts can be improved by approximately 2–4 times over commercially available catalysts.
A QSBR development procedure for aromatic xenobiotic degradation by unacclimated bacteria
Authors: Okey Robert W. , Stensel H. David
Published: February 2012

ABSTRACT:  The relationship between chemical structure and the comparative rate of biodegradation (defined here as the biodegradation index) by unacclimated activated sludge has been studied. The findings of one model illustrate that the relationship between structure and biodegradability for a homologous series of aromatic compounds may be easily developed using techniques drawn from medical and pharmacological sciences, in this case, Hammett's constants. This is true when the biodegradation pathway is known. However, such a model is not broadly applicable to a diverse group of substances where such pathway information is not available. A second model was developed using a newer technique—molecular connectivity indices—which does not require pathway information. The second model was calibrated with the data employed in the first model. This model did not contain specific pathway or directional information, but successfully predicted the rates at about the same confidence level as the first.
Simplified calculation procedure for carbon adsorption model
Authors: Roy Dipak , Wang Guang‐Te , Adrian Donald Dean
Published: February 2012

ABSTRACT:  The nonlinear equilibrium isotherm relationship for carbon adsorption has been linearized by expanding it using a Taylor series. The Taylor series expansion is truncated so that the resulting linear form can be substituted into the equation obtained by applying orthogonal collocation technique to the differential equation for adsorption process. Finally, a set of algebraic formulas was derived by using Laplace transform for calculating bulk liquid concentration and interface liquid concentration. The Taylor series replacement iterative procedure is recommended for calculating the true values of bulk liquid concentration. The results from the new approach were verified by comparison with those obtained from Runge‐Kutta integration using experimental data reported by other investigators. The proposed algebraic method is applicable for all types of batch adsorption experimental data without any restrictions.
Fate of chlorination byproducts and nitrogen species during effluent recharge and soil aquifer treatment (SAT)
Authors: Amy Gary , Wilson L. Gray , Conroy Aimee , Chahbandour John , Zhai Wenyi , Siddiqui Mohamed
Published: February 2012

ABSTRACT:  A pilot‐scale study was conducted under field conditions to determine the potential role of soil aquifer treatment (SAT) in renovating wastewater effluent to potable water quality. Instrumented test basins were used to evaluate water quality transformations through the upper vadose zone during effluent recharge. Samples of either chlorinated secondary or reclaimed (tertiary) effluent were obtained from suction samplers situated in two separate test basins at depths of up to 6.1 m (20 ft). Samples were characterized according to dissolved organic carbon (DOC), a measurement of dissolved organic matter, and total organic halide (TOX), a measurement of chlorination byproducts. Average DOC and TOX removals were 50% and 40%, respectively, for secondary source water; slightly higher removals were observed for tertiary source water. Performance was found to be affected by operational factors; variations in DOC and TOX removal were observed within a wetting cycle as well as from cycle to cycle. Significant nitrification occurred during drying cycles between flooding cycles, resulting in an initial wave of high nitrate in the percolating water.
Measurement of chemical sludge floc density and implications related to sludge dewatering
Authors: Knocke William R. , Dishman C. Michael , Miller Gail F.
Published: February 2012

ABSTRACT:  An isopyenic centrifugation procedure was developed for estimating the characteristic floc density present in several chemical sludges. Issues addressed included selection of a low osmotic pressure gradient medium; selection of appropriate centrifugal acceleration and time values for testing; viscosity effects; and need for temperature control. Increases in sludge floc density were predictive of an increase in cake solids concentration following mechanical dewatering. Most sludge water removal during dewatering was hypothesized to be external to the floc structure.
Slip flow through porous media with permeable boundaries: implications for the dimensional scaling of packed beds
Authors: Chellam Shankararaman , Wiesner Mark R.
Published: February 2012

ABSTRACT:  A theoretical description of single‐phase flow through porous media having permeable boundaries is presented. The volume averaged momentum transfer equation is solved numerically by a finite difference technique after neglecting the nonlinear inertia term. The influence of fluid slip on axial velocity profiles and wall skin friction is analyzed as a function of cross‐flow and the porous medium shape factor. Boundary effects on momentum transfer are quantified. The implications for the design of scale models for porous media such as filters, adsorber columns, and aeration towers are discussed. In accordance with experimental data obtained by other researchers, it is shown that in most cases, additional viscous dissipation effects due to the presence of boundaries are expected to be insignificant even in laboratory‐scale models only a few packing element diameters wide.
Process and kinetic analysis of nitrification in coupled trickling filter/activated sludge processes
Authors: Daigger Glen T. , Norton Lynn E. , Watson Richard S. , Crawford Deborah , Sieger Ronald B.
Published: February 2012

ABSTRACT:  A model for nitrification in a coupled trickling filter/ activated sludge system is presented. Nitrification will occur in the trickling filter component of the system when the organic loading to the trickling filter is about 1 kg BOD5/m3· d (60 lb BOD5/1000 ft3 · day); the degree of nitrification will increase as the organic loading decreases below this value. Nitrification in the upstream trickling filter has two impacts on the downstream suspended growth unit. First, partial removal of ammonia by the upstream trickling filter reduces the ammonia‐nitrogen loading on the downstream suspended growth unit. Second, the seeding effect of nitrifiers grown on the upstream trickling filter which slough off and pass into the downstream suspended growth unit allows the suspended growth unit to nitrify at solids residence times that would otherwise preclude nitrification. A mathematical model for the suspended growth units that incorporates this seeding effect is developed and presented. Data from the City of Garland, Texas, Duck Creek and Rowlett Creek Wastewater Treatment Plants are presented that demonstrate this mechanism and verify the predictive capability of the proposed model.
A model of measurement precision at low concentrations
Authors: Berthouex P. M. , Gan D. Robert
Published: February 2012

ABSTRACT:  This paper presents a model that describes the precision of measurements at low concentrations (near the limit of detection). The total variance includes both background noise, which exists even when no analyte is present and is assumed to have a fixed variance, and analytical error, which in chemical measurements is often proportional to the concentrations of the analyte. This total variance model is used to define a limit of detection and two other measures of measurement precision. These are the Characteristic Limit, which is defined as the concentration where the variances of background noise and analytical error are equal, and the Limit of Guaranteed Purity, which defines how large the true concentration might be, in light of a given measured value. Data on lead in wastewater effluent and organic chemicals in sediment are used to illustrate the calculations and demonstrate the performance of the model.
Comparative performance of anaerobic filters at mesophilic and thermophilic temperatures
Authors: Harris William L. , Dague Richard R.
Published: February 2012

ABSTRACT:  Anaerobic filters were operated at mesophilic and thermophilic temperatures with hydraulic retention times (HRTs) of 12, 24, and 48 hours over a COD loading range from 2.75 g/L/day to 49.5 g/L/day (172 to 3090 lb/1000 cu ft/day). The purpose of the research was to determine the effect of HRT and organic (COD) loading as independent variables. Results indicated that the mesophilic systems were more sensitive to HRT than were the thermophilic systems, with significant decreases in performance of the mesophilic systems with decreases in HRT. The thermophilic reactors showed virtually no reduction in performance with decreased HRT. The increase in organic load produced a reduction in removal efficiency at all HRTs for the mesophilic reactors. The effect of organic load was more significant at the lower HRTs for the mesophilic reactors. The thermophilic units, on the other hand, displayed a reduction in chemical oxygen demand (COD) only at the high loadings while at an HRT of 48 hours. The increase in loadings showed little effect at the lower HRTs (24 and 12 hours) when the systems were able to flush the inhibitory substances from the reactors. Overall, the thermophilic systems were able to treat the waste at more than twice the COD loading rate of the mesophilic systems.
Sediment and benthic response to wastewater solids in a marine mesocosm
Authors: Maughan James T. , Oviatt Candace A.
Published: February 2012

ABSTRACT:  Wastewater solids were added to a series of marine mesocosms at the Marine Ecosystem Research Laboratory (MERL), University of Rhode Island. There was a range of sludge addition simulating 1, 4, and 8 times the average nitrogen enrichment of Narragansett Bay. Three other mesocosms received inorganic nutrients at similar levels, and three mesocosms were maintained as controls. In systems receiving nutrients or sludge, primary production was initially increased. Respiration of the increased loading in the sludge treatment generally resulted in decreased dissolved oxygen concentrations. In the highest level of sludge treatment, the benthic respiration resulted in anoxic conditions in the fourth month of the experiment. The benthos seemed to be the area primarily affected by wastewater disposal. Species feeding at or near the sediment–water interface showed a strong positive density response to sludge addition because of the increase in available food. Based on the findings of this experiment and comparison with marine areas of wastewater disposal, the condition of the benthic community can be generally defined based on organic loading rates. Organic loading rates less than approximately 0.1 g/m2 · d C had little effect on the sediment community. Loading rates between 0.1 and 1.0 g/m2 · d C resulted in an enriched sediment community, while loading over 1.5 g/m2 · d C produced degraded conditions. The quantification of the relationship between organic loading and benthic response presented here can be useful in evaluating wastewater treatment and disposal options.
Variation of carbon monoxide production during methane fermentation of glucose
Authors: Bae Jaeho , McCarty Perry L.
Published: February 2012

ABSTRACT:  Carbon monoxide (CO) production in continuous stirred tank reactors (CSTRs) following perturbations with glucose, formate, or acetate was the focus of this study. Although reactors were operated in a similar manner, CO concentration following perturbations with substrate increased above detection limits in some reactors, but not in others. Where detectable, CO concentration appeared to increase in an unpredictable fashion with increases in acetate, formate, and possibly H2 concentrations. With one mixed culture, CO concentration increased from 0.051 Pa (0.5 × 10−6 atm) to only 0.41 Pa (4 × 10 −6 atm) when acetate concentration was increased to 20 mM, but increased no further with acetate increase to 60 mM. During formate perturbations with one culture, CO increased to a very high value of 25 Pa (250 × 10−6 atm), a concentration near thermodynamic equilibrium with the added formate. However, in another mixed culture operated under similar conditions, the addition of similar acetate and formate concentrations resulted in formation of barely detectable CO concentrations (about 0.05 Pa). Such inconsistencies in CO production following substrate perturbations, even under similar conditions of operation, suggest that CO is not a useful monitoring parameter for the control of anaerobic treatment.