Showing papers in "Journal of Environmental Engineering in 1994"
TL;DR: In this paper, a mass transfer-based model is developed for predicting chlorine decay in drinking-water distribution networks, considering first-order reactions of chlorine to occur both in the bulk flow and at the pipe wall.
Abstract: A mass‐transfer‐based model is developed for predicting chlorine decay in drinking‐water distribution networks. The model considers first‐order reactions of chlorine to occur both in the bulk flow and at the pipe wall. The overall rate of the wall reaction is a function of the rate of mass transfer of chlorine to the wall and is therefore dependent on pipe geometry and flow regime. The model can thus explain field observations that show higher chlorine decay rates associated with smaller pipe sizes and higher flow velocities. It has been incorporated into a computer program called EPANET that can perform dynamic water‐quality simulations on complex pipe networks. The model is applied to chlorine measurements taken at nine locations over 53 h from a portion of the South Central Connecticut Regional Water Authority's service area. Good agreement with observed chlorine levels is obtained at locations where the hydraulics are well characterized. The model should prove to be a valuable tool for managing chlori...
449 citations
TL;DR: This paper reviews the history associated with the occurrence and regulation of disinfection by-products in finished drinking water, some of the underlying chemistry associated with their formation, technologies and strategies appropriate for their control, and conclusions concerning the current status of their regulation in the United States.
Abstract: This paper reviews the history associated with the occurrence and regulation of disinfection by-products in finished drinking water, some of the underlying chemistry associated with their formation, technologies and strategies appropriate for their control, and conclusions concerning the current status of their regulation in the United States. Key issues and concerns, along with recommendations for further research, are identified and incorporated into the discussion. The importance of balancing risks associated with disinfection by-products against risks associated with waterborne pathogenic microorganisms is emphasized, along with the notion that limited information concerning the occurrence and health effects of disinfection by-products and reliable, safe, and cost-effective strategies for their control preclude their strict regulation at this time.
374 citations
TL;DR: In this paper, an Escherichia coli strain, ATCC 33456, was reduced by using a variety of electron donors including glucose, acetate, propionate, glycerol and glycine.
Abstract: Toxic hexavalent chromium, Cr(VI), was reduced by an Escherichia coli strain, ATCC 33456, under both aerobic and anaerobic conditions by using a variety of electron donors including glucose, acetate, propionate, glycerol and glycine. In addition to electron‐donor type, the initial cell concentration, Cr(VI) concentration, pH, and temperature had profound effects on the rate of Cr(VI) reduction. Cr(VI) reduction was not significantly affected by the presence of moderate level of phenolic compounds. The concentration levels that caused a 50% reduction in the rate of Cr(VI) reduction (IC50) were 986, 1,526, and 5,263 mg/L for p‐cresol, 2‐chlorophenol, and phenol, respectively, in anaerobic cultures with higher IC50 values noted in aerobic cultures. Cr(VI) reduction by this strain was more susceptible to heavy metals (Zn2+ and Cu2+) than the phenolic compounds. The reduction of Cr(VI) by E. coli ATCC 33456 was enzymatic, and was not affected by redox potential of the culture media and other possible electron ...
170 citations
TL;DR: In this article, a node flow analysis that determines the available nodal flows under deficient conditions by considering the nodal demands and heads, simultaneously, is presented for determining WDS reliability.
Abstract: Traditional network analysis (Hardy Cross, Newton‐Raphson, or linear theory methods) presumes that the nodal demands are always satisfied in a water‐distribution system (WDS) and determines the available heads. However, when a pump fails or a pipe breaks, the WDS may be unable to supply all nodal demands at required heads. Thus, the traditional network analysis does not correctly describe the partially failed WDS. In reliability analysis of WDSs, however, the nodal flows that would be available under deficient conditions should be evaluated and used. Therefore, an approach termed node flow analysis that determines the available nodal flows under deficient conditions by considering the nodal demands and heads, simultaneously, is presented for determining WDS reliability. The reliability is based on a node‐reliability factor, volume‐reliability factor, and network‐reliability factor. Even though WDS reliability depends on several parameters, only the pipe break and pump failure conditions are considered. Ho...
143 citations
TL;DR: In this paper, a process for the treatment of industrial wastewater containing heavy metals, using fly ash adsorption and cement fixation of the metal-laden adsorbent, was investigated.
Abstract: A process for the treatment of industrial wastewater containing heavy metals, using fly ash adsorption and cement fixation of the metal-laden adsorbent, was investigated. Results show that the fly ash can be an effective metal adsorbent, at least for Zn(II) and Cd(II) in dilute industrial wastewaters. Fly ash adsorption capacities for Zn(II) and Cd(II) were 0.27 mg/g and 0.05 mg/g, respectively. A mortar specimen prepared with 10% metal-laden fly ash showed a 56-day strength, about the same or even greater than that of cement alone. Leachates from the fixed metal-laden fly ash, obtained by using both the ASTM and U.S. Environmental Protection Agency-extraction procedure (USEPA-EP) leaching tests, exhibit metal concentrations lower than the drinking water standards. Compressive strength and leaching tests results suggest that metal-laden fly ash can be considered for use in secondary construction materials.
130 citations
TL;DR: Bacterial colonization of GAC was monitored in three carbon filters having varying depths and filtration velocities, but similar empty bed contact time (EBCT), indicating that biological removal of organic matter in GAC filters having a given EBCT is independent of filTration rate.
Abstract: A study of biological filtration on granular activated carbon GAC has been performed at the Neuilly-sur-Marne (France) treatment plant using experimental pilot filters. Bacterial colonization of GAC was monitored in three carbon filters having varying depths and filtration velocities, but similar empty bed contact time (EBCT). About three months were required to colonize the GAC in the filters and a steady state bacterial biomass of around 2 μgC/cm³ GAC was reached. During the colonization period, removal of nonbiodegradable organic carbon (NBDOC) by filtration decreased from 50% to less than 10% showing a gradual saturation of GAC adsorption capacity. However, biological processes take turn with adsorption to ensure a significant removal of biodegradable dissolved organic carbon (BDOC) during the study period (more than 200 days). Filters operating under different conditions did not show any difference in the BDOC removal. This indicates that biological removal of organic matter in GAC filters having a given EBCT is independent of filtration rate (in the range 6 m/h–18 m/h). The maximum bacterial density in the filter effluent water was 1.5 x 10\u5 bacteria/mL during the colonization phase; this seemed to be linked to a lag in establishing a protozoan population, which, at equilibrium, efficiently removed bacterial biomass produced within the filters. Once established, the efficiency of this complex microbial assemblage was remarkable; the removal of about 0.25 mgC/L of BDOC resulted in the release of less than 0.5 x 10\u5 bacteria per milliliter, around 0.0015 mgC/L as bacterial biomass in the effluent.
129 citations
TL;DR: In this paper, a model of sediment oxygen demand (SOD) was presented that relates the SOD to flow velocity over the sediment, and a quantitative relationship between SOD and the velocity and dissolved oxygen concentration in the bulk water.
Abstract: A model of sediment oxygen demand (SOD) is presented that relates the SOD to flow velocity over the sediment. Previous analyses emphasize, almost exclusively, the relationship between SOD and sediment composition, i.e., their chemistry and biology. Herein a quantitative relationship is established between SOD and the velocity and dissolved oxygen concentration in the bulk water. Oxygen consumption in the sediment is expressed as the sum of biological consumption with Michaelis‐Menten kinetics, and the chemical consumption assumed to be a first order reaction of oxygen. At very low flow velocities, transport through the diffusive water boundary layer is the limiting factor of SOD, and SOD is expressed as a linear increasing function of velocity. On the other hand, when flow velocities are increased, SOD becomes independent of velocity, since the reactions in the sediment become rate‐limiting. The model also suggests that SOD is an increasing function of dissolved oxygen concentration in the water overlying...
122 citations
TL;DR: In this article, a physicochemical model for the distribution of hydrophobic organic compounds between aqueous, micellar, and sorbent compartments in a soil/aqueous system containing nonionic surfactant micelles is presented.
Abstract: Hydrophobic organic compounds (HOCs) are modeled as being distributed between aqueous, micellar, and sorbent compartments in a soil/aqueous system containing nonionic surfactant micelles. The partitioning of HOC between the hydrophobic interiors of the nonionic surfactant micelles and the surrounding solution can be characterized with a mole fraction partition coefficient. Nonionic surfactant sorption onto soil may be described by a maximum sorption parameter. Sorbed surfactant molecules tend to increase HOC sorption, and free surfactant monomers in solution tend to decrease HOC sorption by increasing the HOC apparent aqueous solubility; these effects can be represented by a modified HOC soil/water partition coefficient. The distribution of HOC between the three compartments can be estimated using a physicochemical model, for which model parameter values conceptually may be obtained from independent experiments.
117 citations
TL;DR: In this article, the mineral surface of Wyoming bentonite was modified by replacing inorganic ions by different quaternary ammonium compounds of known molecular structure by an ion exchange process, and the resulting organically modified bentonites (organobentonites) were evaluated for their suitability as components of compacted earthen liners for waste-disposal sites.
Abstract: The mineral surface of Wyoming bentonite was modified by replacing inorganic ions by different quaternary ammonium compounds of known molecular structure by an ion‐exchange process. The resulting organically modified bentonites (organobentonites) were evaluated for their suitability as components of compacted earthen liners for waste‐disposal sites. Varying weight percentages of an Ottawa sand, either of five types of organobentonites, untreated bentonite, and water were mixed uniformly and compacted to simulate sand‐and‐bentonite liners for waste‐disposal facilities. The hydraulic conductivities of the compacted soil specimens were measured in triplicate. The hydraulic conductivities of compacted specimens composed of 88% (by mass) Ottawa sand, 8% untreated bentonite, and 4% organobentonite were on the order of 10−8 cm/s. Benzene sorption from water to Ottawa sand, bentonite, and two of the organobentonites was measured experimentally. Benzene sorption to each organobentonite was significantly greater th...
109 citations
TL;DR: The use of granular activated carbon (GAC) columns to treat lead wastewaters was investigated in this article, where significant quantities [70 to 325 bed volumes (BV)] of wastewater were treated prior to breakthrough (Ce=0.03C0); X/M−values were as high as about 30 mg Pb/g carbon.
Abstract: The use of granular activated carbon (GAC) columns to treat lead wastewaters was investigated. Synthetic wastewaters containing Pb (10 or 50 mg/ L), acetic acid (0.001 N) or EDTA (1:0.1 or 1:1 Pb:EDTA molar ratios) were studied. For lead‐only and lead‐acetic acid experiments significant quantities [70 to 325 bed volumes (BV)] of wastewater were treated prior to breakthrough (Ce=0.03C0); X/M‐values were as high as about 30 mg Pb/g carbon. For EDTA experiments, Ce was always >0.03C0. The amount of lead not removed corresponded to the amount that was complexed by EDTA. Column pH is the critical parameter influencing column performance. The increase in effluent Pb concentration corresponded with the decrease in column pH. GAC columns were successfully regenerated using a 1L(≈8BV)0.1NHNO3 rinse followed by a 1L0.1NNaOH rinse. Column performance was not adversely affected by regeneration. When the regeneration step was used on virgin carbon, a dramatic improvement in column performance was observed and was attr...
87 citations
TL;DR: The feasibility, advantages, and problems of using linear programming methods in the preliminary analysis of central material-recovery facilities are discussed and demonstrated in this article, where the proposed method is implemented using a commercial linear programming package and using Microsoft EXCEL spreadsheet software.
Abstract: The feasibility, advantages, and problems of using linear‐programming methods in the preliminary analysis of central material‐recovery facilities are discussed and demonstrated. The design and operation of such facilities involves a wide variety of choices. Linear programming can help identify promising directions for design and operations from many feasible choices. Linear programming is likely to be most effective when used in conjunction with traditional engineering process flow diagrams, computerized in spreadsheet form. The proposed method is implemented using a commercial linear‐programming package and using Microsoft EXCEL spreadsheet software.
TL;DR: In this article, a simulation model is developed to predict contaminant elution curves during solvent flushing for the case of one-dimensional, steady flow through a contaminated medium, where column experiments are conducted with a Eustis fine sand that is initially equilibrated with an aqueous naphthalene solution, and then eluted with different methanol-water mixtures to remove the contaminants.
Abstract: Solvent flushing is a potential technique for remediating a waste disposal/spill site contaminated with organic chemicals. This technique involves the injection of a solvent mixture (e.g., water plus alcohols) that enhances contaminant solubility, reduces the retardation factor, and increases the release rates of the contaminants. A simulation model is developed to predict contaminant elution curves during solvent flushing for the case of one‐dimensional, steady flow through a contaminated medium. Column experiments are conducted with a Eustis fine sand that is initially equilibrated with an aqueous naphthalene solution, and then eluted with different methanol‐water mixtures to remove the naphthalene. The model simulations, based on parameter values estimated from literature data, agree well with the measured elution profiles. Solvent flushing experiments, where the soil was initially equilibrated with a solution of naphthalene and anthracene, show that compounds with different retardation factors are separated at low cosolvent contents, while coelution of the compounds occurs at higher contents. In general, the smaller the retardation factor in water and the higher the cosolvent fraction, the faster the contaminant is recovered. The presence of nonequilibrium conditions, soil heterogeneity, and type of cosolvent will influence the time required to recover the contaminant.
TL;DR: In this article, the authors developed a computer-based suite of mechanistic models collectively known as TOXCHEM, which predicts the fate of VOCs in wastewater treatment plants.
Abstract: The need for the control of volatile organic contaminants (VOCs) has led to the development of a computer‐based suite of mechanistic models collectively known as TOXCHEM, which predicts the fate of VOCs in wastewater treatment plants. TOXCHEM includes both steady‐state and dynamic models, and will predict the location and mass of VOC emissions from several locations within a wastewater treatment installation. Derivations are shown for expressions describing important removal rate coefficients and VOC mass balances for each unit process of a secondary treatment plant. Calibration of the model at pilot scale was conducted, and data from other full‐scale investigations were used to verify the model. It was found that the TOXCHEM models predicted reasonably well and would improve as the true rate coefficients are established. This model has the potential to be an extremely useful tool for wastewater treatment plant engineers and administrators of sewer use regulations.
TL;DR: In this paper, a multiobjective optimization model is presented to determine the efficient aggregation of land parcels for use as a solid or hazardous waste landfill, and a new constraint for measuring c...
Abstract: A multiobjective optimization model is presented to determine the efficient aggregation of land parcels for use as a solid or hazardouswaste landfill. In this work, a new constraint for measuring c...
TL;DR: In this paper, a continuous process of combined ozonation and chemical coagulation was employed for treatment of textile wastewaters from several dyeing and finishing plants for color removal.
Abstract: A continuous process of combined ozonation and chemical coagulation was employed for treatment of textile wastewaters from several dyeing and finishing plants. Ozonation was found to be highly effective in color removal with complete discolorization of textile wastewater being achieved in less than 10 min in the continuous reactor. Chemical coagulation was observed to be mainly responsible for removing dissolved and suspended solids with a COD removal efficiency of up to 66%. The treatment efficiency of the combined process can be further enhanced when used in conjunction with the activated sludge process. Preliminary economic analysis of the process shows that ozonation for decolorization is highly competitive in terms of its total cost compared with use of decoloring agent. The cost saving is further complemented by a considerable improvement in the overall quality of the treated wastewater.
TL;DR: In this article, a series of bench-scale continuous flow experiments, using primary sludge from a local municipal wastewater-treatment plant, has been employed to investigate the effect of hydraulic retention time (HRT) on the acid phase anaerobic digestion process.
Abstract: A series of bench‐scale, continuous‐flow experiments, using primary sludge from a local municipal wastewater‐treatment plant, has been employed to investigate the effect of hydraulic retention time (HRT) on the acid‐phase anaerobic digestion process. Results show that both volatile fatty acid (VFA) production and chemical oxygen demand (COD) solubilization increase significantly with increasing HRT up to 12 h, but drop moderately at a longer HRT. Acetic acid and propionic acid are the main VFAs formed, averaging 46% and 32% of the total, respectively. Variation in HRT has a profound effect on organic substrate degradation as well. Regardless of the prevailing experimental conditions, lipids and carbohydrates are converted at higher percentages than proteins. Furthermore, protein utilization appears to be independent of reactor configuration, but carbohydrate and lipid degradation patterns are a function of the reactor regime.
TL;DR: In this article, the axial dispersion model (ADM) was provided to integrate the nonideal mixing, mass transfer, and ozonedecay process as a whole, and the effects of various process parameters on the ozone profiles were analyzed numerically.
Abstract: Mathematical models previously employed to analyze concentration profiles of dissolved ozone in bubble‐column contactors often assumed either plug flow or complete mixing. In this paper a more realistic model, the axial dispersion model (ADM), was provided to integrate the nonideal mixing, mass‐transfer, and ozone‐decay process as a whole. The effects of various process parameters on the ozone profiles were analyzed numerically. It was found that a group of dimensionless quantities (PeL, Da, StG, and StL) is most convenient in describing the performance of ozone‐contacting systems. The different types of ozone contactors (countercurrent‐flow bubble columns, cocurrent‐flow bubble columns, and reactive contacting chambers) exhibited different patterns of concentration profile; as a result, different approaches are needed to relate their characteristic concentrations to readily observed measurements for predicting the disinfection efficiency. The applicability of the model is illustrated through the analysis...
TL;DR: In this article, the U.S. Environmental Protection Agency proposed three rules: an information collection (ICR), an enhanced surface water treatment rule (ESWTR), and a two-stage D/DBP rule.
Abstract: The U.S. Environmental Protection Agency (U.S. EPA) is currently attempting to balance the complex trade-off in chemical and microbial risk associated with controlling disinfection and disinfection by-products (D/DBP) in drinking water. In attempting to achieve this balance, the U.S. EPA will propose three rules: an information collection (ICR); an enhanced surface water treatment rule (ESWTR) and a two-stage D/DBP rule. Controlling D/DBP will have a major impact on drinking water utilities in the United States. There are several options for D/DBP control, including moving the point of disinfection, removal of by-products once they are found, removing precursor material or natural organic matter before it interacts with the disinfectant, or use of a disinfectant that minimizes the formation of by-products. The least-expensive approach to D/DBP control is to move the point of disinfection or the use of an alternative disinfectant. The least-desirable approach is to remove disinfection by-products once they are formed. Overall, the most effective approach to D/DBP control is to remove precursor before it reacts with the disinfectant. The choice of any given strategy is very site specific.
Journal Article•
TL;DR: In this article, the authors examined the detail of moisture profiles in three landfills located in semi-arid climates in a Third World country and concluded that one of the components of the water balance that is most difficult to define or estimate is the storage capacity of the refuse body.
Abstract: Waste‐disposal practices in poor Third World communities can have extremely adverse environmental impacts, especially with regard to ground‐water pollution. The water‐balance or water‐budget method has been developed and used to predict leachate production from sanitary landfills. This study examines the detail of moisture profiles in three landfills located in semiarid climates in a Third World country. It concludes that one of the components of the water balance that is most difficult to define or estimate is the storage capacity of the refuse body. This appears to be greatly influenced by the properties and disposition of the layers of intermediate cover. This information is most important for the design of low‐cost, environmentally acceptable landfills for Third World communities. The study also investigates soil moisture suction in landfills and concludes that even in semiarid areas, soil moisture suction in landfills is sufficiently low to enable uninhibited bacteriological activity to take place.
TL;DR: The type and quantity of wastes produced by this industry, much of which are listed hazardous wastes, as well as the hazardous waste disposal problems facing this industry are discussed in this paper.
Abstract: Semiconductors are electrical devices that perform functions such as processing and display, power handling, and conversion between light and electrical energy Semiconductor production processes involve over 100 proprietary solutions and 200 generic materials to achieve the final product This industry generates significant quantities of spent solvents and liquids containing metals The economic and liability incentives caused by increasing disposal costs and more stringent regulations are resulting in efforts to minimize such wastes at the source This paper provides information about: (1) The type and quantity of wastes produced by this industry, much of which are listed hazardous wastes; (2) the hazardous waste disposal problems facing this industry; and (3) waste minimization case studies
TL;DR: In this paper, air extraction and injection in both horizontal and vertical wells are evaluated to estimate air conductivity and porosity in the vadose zone, and 60 data sets were developed by measuring gas pressures as a function of time at six gas probes during each of the tests.
Abstract: Field tests using air extraction and injection in both horizontal and vertical wells are evaluated to estimate air conductivity and porosity in the vadose zone. Six extraction tests and four injection tests were conducted. Sixty data sets were developed by measuring gas pressures as a function of time at six gas probes during each of the tests. Two analytical procedures are used to evaluate each data set. The first procedure, which is a modified Theis analysis, neglects the effects of leakage through the top boundary of the flow field. The second procedure, which is a modified Hantush analysis, includes the effects of leakage by assuming that it is generated within the flow layer. Image‐well theory can be used to evaluate data from horizontal wells. Variations in parameter estimates are caused by spatial variability, measurement error, data analysis methodology, well configuration, and the direction of air flow. At this particular field site, variations due to measurement errors were of the same order as ...
TL;DR: In this paper, the authors compared experimental data with results from a model developed for nonionic surfactant solubilization of hydrophobic organic compounds (HOCs) in soil/aqueous systems.
Abstract: Experimental data are compared with results from a model developed for nonionic surfactant solubilization of hydrophobic organic compounds (HOCs) in soil/aqueous systems. The model parameters that describe each of the major physicochemical processes affecting sorption and micellar uptake of both nonionic surfactant and hydrophobic organic compounds can be characterized with values obtained independently from separate experiments involving aqueous, soil, or soil/ aqueous systems. The experimental data presented in this paper demonstrate that the modeling approach is reasonably valid for several nonionic surfactants. It is also shown that treating a soil with successive surfactant washings results in greater removal of HOC than a single washing with the same total mass of surfactant. An inverse method is evaluated with experimental data. This method permits the determination of a ratio of the values of two of the model parameters from gross experimental data such that if one parameter is measured the other ...
Journal Article•
TL;DR: In this article, the use of ORP to control two lab-scale aerobic-anoxic sludge digesters was evaluated using a sequencing batch-reconstruction approach, where one was operated in a real-time manner with 3 h of air-on and air-off time determined by computer detection of the breakpoint in the orp-time profile.
Abstract: This research documents the use of oxidation‐reduction potential (ORP) to control two lab‐scale aerobic‐anoxic sludge digesters. The reactors were operated in sequencing batch reactor fashion, and one reactor had the ratio of air‐on/air‐off arbitrarily “fixed” at 3 h for each portion of the cycle. The other reactor operated in a real‐time manner with 3 h of air‐on and the air‐off time determined by computer detection of the nitrate breakpoint in the orp‐time profile. Reactor performances were evaluated from a chemical (mass balance) removal perspective [total and volatile suspended solids (TSS and VSS), nitrogen, and phosphorus] coupled with a consideration of the control stability achieved when the reactors were subjected to spikes of sodium nitrate, ammonium chloride, and hydrogen peroxide. The reactors showed comparable chemical removals, however the real‐time control reactor displayed a greater ability to accommodate the disturbances investigated.
TL;DR: A procedure was developed to predict the removal of trace organic compounds from natural water by powdered activated carbon (PAC) adsorption systems, which function as a batch reactor or a continuous stirred tank reactor (CSTR).
Abstract: A procedure was developed to predict the removal of trace organic compounds from natural water by powdered activated carbon (PAC) adsorption systems, which function as a batch reactor or a continuous stirred tank reactor (CSTR) The procedure uses the equivalent background compound method coupled with the ideal absorbed solution theory to quantify the competition between trace organics and background organic matter in water, and uses the pseudo single-solute homogeneous surface diffusion model to describe the adsorption kinetics of the target compound under the influence of the background organic matter The parameters required by the model as input data can be independently determined from adsorption isotherms and a set of batch kinetic test data Good agreement between predicted aual performance was found for adsorption of atrazine from Central Illinois ground water at different initial concentrations and different carbon doses using a batch reactor and two CSTRs, one of which was a PAC/ultrafiltration system
TL;DR: In this paper, the chemical, microbiological, and mutagenic effects of using the major drinking water disinfectants (chlorine, chlorine dioxide, chloramine, ozone) w...
Abstract: During a oneyr study at Jefferson Parish, La., the chemical, microbiological, and mutagenic effects of using the major drinking water disinfectants (chlorine, chlorine dioxide, chloramine, ozone) w...
TL;DR: In this article, a laboratory-scale continuously fed anaerobic attached film expanded bed (AAFEB) was used to examine the feasibility of tetrachloroethylene/ trichlorocethylene (PCE/TCE) dechlorination.
Abstract: A laboratoryscale continuously fed anaerobic attached film expanded bed (AAFEB) reactor is utilized to examine the feasibility of tetrachloroethylene/ trichloroethylene (PCE/TCE) dechlorination und...
TL;DR: A biofilm model for the cometabolic degradation of trichloroethylene (TCE) by methane oxidizing (methanotrophic) bacteria is derived and reported low rates of TCE degradation by biofilms were found to be compatible with the high rates found in dispersed growth studies.
Abstract: A biofilm model for the cometabolic degradation of trichloroethylene (TCE) by methane oxidizing (methanotrophic) bacteria is derived. Methane utilization and TCE transformation were modeled using diffusive mass transport, Monod kinetics, competitive inhibition, TCE transformation product toxicity, and growth, decay and inactivation of the methanotrophic bacteria. Reported low rates of TCE degradation by biofilms were found to be compatible with the high rates found in dispersed growth studies. The slower rates result from phenomena inherent in biofilms, and not necessarily from a difference in performance characteristics of the organisms. The possibility that biofilms may not be copper-limited is also considered. Other model predictions include an optimum methane concentration that maximizes TCE flux. Also, survival of a biofilm should only occur when the methane concentration is above a certain minimum value (S\dm\di\dn), which is linearly related to TCE concentration. The model is general and can be applied to other primary substrates and chlorinated aliphatic hydrocarbons (CAHs).
TL;DR: In this paper, a Monte Carlo analysis of the feasibility for energy-self-sufficient leachate evaporation via landfill methane combustion is presented. But the feasibility of energy-independent leachation is not discussed.
Abstract: This paper reviews and extends understanding of evaporation/distillation as treatment for landfill leachate. Evaporation may produce condensate that is high quality and easier to dispose of than effluent from conventional leachate‐treatment processes with the volume of the concentrated residuals being a small fraction of the original leachate volume. Laboratory‐scale, one‐ and two‐step distillation experiments with pH adjustment were performed with ammonium acetate test solution and three leachate samples from older landfills. A single‐step, acidic distillation of the strongest leachate samples removed more than 95% of ionic impurities, except for volatile organic acids, which were removed at 85%. Two‐step acid‐base evaporation, or ammonia stripping coupled with evaporation, may effectively remove ammonia and volatile organic acids if present together in relatively high concentrations. A Monte Carlo analysis of the feasibility for energy‐self‐sufficient leachate evaporation via landfill methane combustion...
TL;DR: A07 is found to be less toxic to nitrification than some metal and phenolic compounds, but more toxic than some common organic compounds such as formalin, methanol, or acetone.
Abstract: The effect of Acid Orange 7 (A07) (C.I. 15510), an azo dye commonly used in textile, pharmaceutical, food, and cosmetic industries, on the nitrification process is studied using completely stirred tank reactors (CSTR) and batch treatment systems. Azo dyes are of concern because many of the dyes or their metabolic intermediates are carcinogenic. A07 biodegradation is found to be essentially complete when solids retention times (SRT) are maintained above 7.5 days, but systems with lower SRTs are unstable. It is shown that A07 inhibits all stages of the nitrification process. Nitrite oxidizers are found to be more sensitive to A07 tahn ammonium oxidizers. The results of kinetic studies indicate that the inhibition of ammonium oxidation is typified by noncompetitive inhibition; the presence of A07 decreases the maximum substrate utilization rate and very slightly increases K\ds, the half-saturation constant. A07 is found to be less toxic to nitrification than some metal and phenolic compounds, but more toxic than some common organic compounds such as formalin, methanol, or acetone.
TL;DR: In this article, the authors describe the testing of a wastewater treatment optimization model for the developing world (described by Ellis and Tang in 1991) in applications to four existing wastewater treatment units in Puchong, Malaysia; Shatin, Hong Kong; Min shen, Taiwan; and Pattaya, Thailand).
Abstract: This paper describes the testing of a wastewater treatment optimization model for the developing world (described by Ellis and Tang in 1991) in applications to four existing wastewater treatment units in Puchong, Malaysia; Shatin, Hong Kong; Min shen, Taiwan; and Pattaya, Thailand). In each case, a reciprocal matrix of a suitable number of wastewater-treatment alternatives (decision variables) was developed for each of 20 technical and socio-economic parameters. These 20 parameters are flow capacity, influent and effluent characteristics, size of treatment site, nature of site, land cost for site, local/foreign money for construction, local skill for construction, community support, power source, availability of local material, cost of operation and maintenance, professional/technical skill available for operation and maintenance, administration set up, training, professional ethics, climate, waterborne diseases, and endemic vector-borne diseases. The matrices were then integrated by a computer program to obtain a final ranking of the original alternatives using the analytic hierarchy process mathematical technique. The model was also tested for its sensitivity in predicting changes to an appropriate technology selected as socio-economic parameters change with time.