Journal of Environmental Engineering

Arsenic (As) in drinking water was removed by a combined co-precipitation, active filtration process. A serpentine prereactor for ferric chloride $\left({\mathrm{FeCl}}_3\right)$ reagent mixing was combined with a moving bed active filter, followed by separation of waste residuals from clean water discharge. Waste effluent, using 10% of influent for transport, was retained in a clarifier for settling prior to water recycling. Process residuals passed leach tests for landfill disposal. The pilot-scale apparatus was tested at a small community, public drinking water system in Fruitland, Id. In a $49\text{hour}$ test, influent groundwater averaging $40.2\pm 1.0\mu \mathrm{g}∕\mathrm{L}$ total As $(n=17)$ was fed at $38\mathrm{L}∕\min \left(10\mathrm{gpm}\right)$ and $\mathrm{Fe}{\mathrm{Cl}}_3$ solution was added at an optimized Fe to As molar ratio of 133:1. Arsenic concentrations were reduced to $3.3\pm 1.4\mu \mathrm{g}∕\mathrm{L}(n=49)$ over the test period. Research observations support the hypothesis that the formation and renewal of iron oxide-coated sand in the active filter is a viable mechanism for high efficiency As removal. Further testing is underway to optimize long-term operating performance and to characterize the chemical processes of the system.

An electrochemical (EC) disinfection system employing an iridium–antimony–tin-coated titanium anode and direct current was used to inactivate bacteriophage MS2 in synthetic solutions with sodium chloride addition. The inactivation data fit the modified Chick–Watson $(n\ne 1)$ model well. The model indicates that, although better disinfection could be achieved with increases in salt content, contact time, and applied current, these three parameters influence the EC disinfection of MS2 in distinct manners and to different degrees. Compared with chlorination, our EC disinfection system exhibited superior inactivation capability especially with a longer contact time or in the presence of ammonium. The formation of trihalomethanes and haloacetic acids in the EC system was smaller than that from chlorination but a large formation of chlorate ions was observed. These differences indicate that the EC system is likely to produce other potent oxidants that enhance inactivation and alter disinfection by-product formation.

Three $12.5\mathrm{L}$ upflow anaerobic filter (AF) reactors, with ceramic saddle, plastic ring, and crushed stone packing, were employed to evaluate the treatment of raw municipal wastewater under a wide range of hydraulic and organic loadings and operating conditions. Emphasis is placed in this paper on column profile sampling, draining, and biomass evaluation studies conducted to ascertain the functioning of the reactors and accumulation of biosolids. The concentration of organics and solids within the AF gradually increased, starting at the low end and progressing to higher elevations. The peak chemical oxygen demand value measured within the reactors was $\mathrm{11,500}\mathrm{mg}∕\mathrm{L}$ and was noted in the stone-packed unit at $20\mathrm{cm}$ after $\mathrm{1,009}\text{days}$ , and the stabilization of suspended material was greater in lower column sections. Packing material morphology influenced the removal by draining of entrapped biomass, and the volume of drainage recovered was substantially smaller than available void space. Biosolids retained in the saddle-packed unit after $34\text{months}$ totaled $33\mathrm{kg}∕\mathrm{1,000}{\mathrm{m}}^3$ wastewater treated, and no signs of clogging were observed in any of the reactors.

Aqueous solutions of trichloroethylene (TCE) and tetrachloroethylene (PCE) were treated in a flow-through reactor equipped with ultrasound and ultraviolet light sources. The reactor was operated as sonolysis (US), photolysis (UV), and simultaneous photosonolysis (UV/US) reactors; then as US, UV, and sequential UV/US reactors with the installation of a partition in the reactor. The reactor without the partition was simulated by using one continuously stirred-tank-reactor (1-CSTR) model, and the reactor with the partition was simulated by using the sequential CSTR model. Through model calibration, the decomposition rate constants and reactor efficiencies for the removal of TCE and PCE were evaluated. The results suggest that the combined effect of UV and US on the decomposition of TCE and PCE is synergistic in both the simultaneous and sequential UV/US modes, that the rate constants of sonolysis and photolysis are greater with the sequential combination than with the simultaneous combination, and that overall efficiency is higher for the reactor with the partition than for the one without it.

Models ranging through simple, intermediate, and International Water Association complex activated sludge models (ASMs) were evaluated to compare their ability to describe biomass growth and substrate removal in an activated sludge system. A membrane-activated sludge bench-scale system was used to treat a complex synthetic wastewater over a wide range of operating conditions, ranging from 1 to 15 days solids retention time and 4 to 12 h hydraulic retention time. Total suspended solids, volatile suspended solids (VSSs), and total and soluble chemical oxygen demands (CODs) were monitored in the influent, the reactor, and the effluent. A variety of substrate removal formulations were used with the simple and intermediate models. Although all models provide excellent prediction of biomass growth, the intermediate model was best. Prediction of substrate removal was good with models that incorporated a nonbiodegradable component in the influent. ASM3 was the best model for predicting effluent soluble COD, but overall, the intermediate model was judged best for prediction of mixed liquor VSS and effluent soluble COD.

Treatment of chemical mechanical polishing wastewater containing nanosized silica from semiconductor industry by dispersed air flotation was investigated. Very effective removal of particles from wastewater was found when cationic surfactant, cetyltrimethyl ammonium bromide (CTAB), was used as a collector. The flotation efficiency decreased slightly under a pH of 4.5. The zeta potential increased with a increasing concentration of CTAB, and flocculation of particles by CTAB was found. It is proposed that both the change of interface properties and the aggregation of particles contributed to flotation removal of particles. Longer reaction time and higher dosage were needed when $n$ -dodecyl amine chloride (DAC) was used as a collector, owing to its relatively weak adsorption. The flotation efficiency increased with increasing DAC concentration. The improved flotation efficiency at pH of 10.0 was probably due to the formation of DAC precipitate.

This study has been originated and motivated by a series of discussions, concerning the containment and use of polluted groundwater of a comparatively wide part of the Coastal Plain Aquifer (CPA) in Israel that has been polluted by kerosene [light nonaqueous phase liquid (LNAPL)]. A variety of types of information have indicated that hydraulic barriers should be employed. However, such an operation should be subject to optimize the aquifer remediation, which is also obtained due to the hydraulic barrier operation. The particular part of the CPA is comprised of “fractured permeable formation” namely sandstone interbedded with sandy clay lenses. Therefore, in this study a simplified conceptual model is applied to represent the formation and implement the pump-and-treat remediation procedure, whose major objective is cost effective containment of the polluted area. Three physical measures, aimed at the remediation process enhancement, have been analyzed: (1) changing the pumping-injection discharge, (2) use of surfactant additives (or other types of solubilizing agents), and (3) use of controlled means to increase the aperture size and density of fracture segments. Possibly, an appropriate combination of such means is most feasible and should be determined. However, the present study evaluates the separate possible effects of each one of such measures on major parameters of the remediation process (time and volume of water that should be treated). It is shown that a particular set of parameters can be applied to evaluate the optimal design and adequate combination of such physical measures aimed at remediation enhancement.

This study investigates the potential of primary sludge fermentation for the generation of readily biodegradable substrate. Experimental evaluation indicates that uncontrolled fermentation converted 22% of the initial volatile suspended solids in the sludge into soluble biodegradable chemical oxygen demand (COD). More than 85% of the soluble COD generated was associated with the formation of short chain volatile fatty acids (VFAs). The recoverable fraction of the fermented sludge supernatant may potentially increase the biodegradable COD content of the primary effluent by 5%. The VFA composition predominantly involved acetic and propionic acids as reported in the literature. Due to the high VFA content, activated sludge Model No. 1 could not predict the COD fractionation in the primary sludge; activated sludge Model No. 3 provided a better interpretation of the oxygen uptake profile through initial storage of the VFAs in the sludge.

Ammonium and nitrate were used as nitrogen sources to support microbial biodegradation of crude oil in continuous-flow beach microcosms to determine whether either nutrient was more effective in open systems, such as intertidal shorelines. No differences in the rate or extent of oil biodegradation were observed, regardless of whether these nutrients were provided continuously or intermittently. Nutrients were provided once every two weeks to intermittent-input microcosms and washed out within four to five days. In continuous-input microcosms, ammonium and nitrate were assimilated as quickly as they were provided during the first week, but both accumulated to greater than $10\mathrm{mg}\mathrm{N}∕\mathrm{L}$ thereafter. The sensitivity of the oil mineralization rate to nutrient input decreased rapidly as the extent of oil degradation increased, and after about two weeks the rate of oil-mineralization appeared to be independent of nutrient input. Therefore, there may be little value in maintaining a long-term supply of nutrients in contact with oil-contaminated sediments. The rates of microbial assimilation of ammonium and nitrate followed similar trends. Both compounds were assimilated more slowly as the extent of oil biodegradation increased, and the nitrate uptake rates approached zero after about two weeks. Ammonium assimilation continued at a low rate throughout the six-week experiment, but this did not appear to affect the rate of oil mineralization. Assimilation of ammonium resulted in a sharp decrease in the pH of the synthetic seawater that was pumped continuously through the microcosms, but nitrate had a much smaller effect on pH. The magnitude of the ammonium-associated pH change was never as large as was observed in previous studies involving oil biodegradation in batch reactors, however, and did not affect the oil-biodegradation rate.

Pollutant detachment rates have been determined for four chloride salts during simulated urban storm runoff. Under rainfall and/or overland flow conditions, chloride mass flux was measured and related to boundary shear stress of the test surface. Washoff coefficients, presumed to depend only on pollutant characteristics, were computed based on the slopes of dimensionless mass flux versus dimensionless time plots. Washoff coefficients were found to vary among and between the chloride compounds studied. In general, higher overland flow rates produced lower boundary shear and lower washoff coefficients. The combination of simulated rainfall and overland flow resulted in an increased boundary shear and an increased washoff coefficient. An empirical washoff coefficient based on a load characteristic curve derived from an exponential washoff relationship was also computed from the runoff data and compared with the previous washoff coefficient. A linear correlation between these two washoff coefficients was observed. The magnitude of the latter coefficient under simulated rainfall was consistent with reported values obtained from field data.

The evaluation of dispersant effectiveness used for oil spills is commonly done using tests conducted in laboratory flasks. The success of a test relies on replication of the conditions at sea. We used a hot wire anemometer to characterize the turbulence characteristics in the swirling flask (SF) and the baffled flask (BF), the latter is being considered by the Environmental Protection Agency to replace the prior. We used the measurements to compute the velocity gradient, $G$ and the energy dissipation rate per unit mass, $\epsilon$ . The study shows that the mixing in the BF is more uniformly distributed than that in the SF. Flask average energy dissipation rates in the SF were about 2 orders of magnitude smaller than those in the BF. The sizes of the microscales in the BF were found to be much smaller than that in the SF. Also, in the BF, the sizes of the microscales approached the size of oil droplets observed at sea $\left(50\text{–}400\mu \mathrm{m}\right)$ , which means that the turbulence in the BF closely resembles the turbulence occurring at sea during breaking waves. Hence, the BF is preferable for dispersant testing in the laboratory.

The loss of polychlorinated biphenyls (PCBs) from sediment by volatilization is currently under scrutiny by polluters, regulators, and researchers. In this research, a one-dimensional mathematical model for the volatilization of PCBs from sediment was developed. The model considers a system with three phases: A water-saturated PCB contaminated sediment, the overlying water, and air above the water. A simple microcosm consisting of sediment, water and air that allows for (pseudo)-one-dimensional transport of PCB from the sediment to the gas phase was utilized to perform PCB transport studies using two PCB congeners: 4, $4^{\prime }$ -dichlorobiphenyl (DCB) and 2, $2^{\prime }$ ,4, $4^{\prime }$ ,5, $5^{\prime }$ -hexachlorobiphenyl (HCB). The experimental data on DCB were used to calibrate and validate the mathematical model. The calibrated model was then used to simulate the effect of sediment layer thickness, depth of the overlying water, and the level of contamination on the rate of DCB volatilization.

The high cost of surfactant enhanced aquifer remediation (SEAR) could be reduced if contaminants in the extracted surfactant flushing water could be biodegraded, and the surfactant reinjected. To test this concept, ex situ biotreatment using immobilized bacteria was simulated in laboratory columns. Nonionic surfactant solutions of $\mathrm{1,000}–\mathrm{5,000}\mathrm{mg}∕\mathrm{L}$ Tergitol NP-10 (TNP10) were flushed through contaminated soil collected from a wood-treatment site. The highest TNP10 dose increased the effluent concentrations of tetrachlorophenol (TeCP) and tetrachlorohydroquinone (TCHQ) by about 3 and 16 times, respectively. These wash solutions were then treated by the aerobic bacterium Sphingomonas chlorophenolica RA2 immobilized in polyurethane foam. The immobilized bacteria were capable of degrading pentachlorophenol, TeCP and TCHQ in soil flushing wastewater containing up to $\mathrm{4,900}\mathrm{mg}∕\mathrm{L}$ TNP10. Surfactant sorption to the biotreatment columns occurred, but these losses decreased over time as the sorption capacity of the foam was exhausted. The results suggest that SEAR wastewater could be biotreated, thus enabling reinjection of the surfactant.

Geographic information systems (GIS) technology was combined with fuzzy logic to construct a phytoremediation plant selection tool. Phytoremediation involves the use of vegetation for treatment of contaminated soils, sediments, and water. In this paper, the focus is on one particular phytoremediation mechanism plant-assisted bioremediation of polycyclic aromatic hydrocarbon (PAH) soil contamination. Many plants show potential for PAH remediation, but factors such as growth requirements, climate, and soil conditions need to be considered. Given the spatial nature of the data involved, GIS was chosen as the basis for the plant selection tool. Eight candidate plants were selected because of their PAH phytoremediation potential, and their growth requirements were represented using fuzzy membership functions to account for parameters’ uncertainty. Vermont and South Carolina were selected as case studies, and calculations were performed to determine the suitability ratings for each of the candidate plants in these areas based on the plants’ growth requirements with respect to climate and soil attributes.

Anaerobic and aerobic treatment of high-strength pharmaceutical wastewater was evaluated in this study. A batch test was performed to study the biodegradability of the wastewater, and the result indicated that a combination anaerobic-aerobic treatment system was effective in removing organic matter from the high-strength pharmaceutical wastewater. Based on the batch test, a pilot-scale system composed of an anaerobic baffled reactor followed by a biofilm airlift suspension reactor was designed. At a stable operational period, effluent chemical oxygen demand (COD) from the anaerobic baffled reactor ranged from 1,432 to $\mathrm{2,397}\mathrm{mg}∕\mathrm{L}$ at a hydraulic retention time (HRT) of 1.25 day, and 979 to $\mathrm{1,749}\mathrm{mg}∕\mathrm{L}$ at an HRT of 2.5 day, respectively, when influent COD ranged from 9,736 to $\mathrm{19,862}\mathrm{mg}∕\mathrm{L}$ . As a result, effluent COD of the biofilm airlift suspension reactor varied between 256 and $355\mathrm{mg}∕\mathrm{L}$ at HRTs of from 5.0 to 12.5 h. The antibiotics ampicillin and aureomycin, with influent concentrations of 3.2 and $1.0\mathrm{mg}∕\mathrm{L}$ , respectively, could be partially degraded in the anaerobic baffled reactor: ampicillin and aureomycin removal efficiencies were 16.4 and 25.9% with an HRT of 1.25 day, and 42.1 and 31.3% with HRT of 2.5 day, respectively. Although effective in COD removal, the biofilm airlift suspension reactor did not display significant antibiotic removal, and the removal efficiencies of the two antibiotics were less than 10%.

A method for Type II settling data analysis was modified for spreadsheet calculations. This method yields values comparable to those given by the traditional manual method. It allows a rapid and objective analysis of experimental data.

The principal objective of this work was to measure nonaqueous phase liquid-air partition coefficients for various gas tracer compounds. Known amounts of trichloroethene (TCE) and tracer, as neat compounds, were introduced into glass vials and allowed to equilibrate. The TCE and tracer concentration of the headspace was analyzed and the partition coefficient was calculated from a mass balance. The TCE-air partition coefficient, defined as the ratio of the concentration of the tracer in the vapor phase to its concentration in the TCE phase, for gas tracer compounds perfluorodimethylcyclobutane, perfluoromethylcyclopentane, perfluoromethylcyclohexane, dibromodifluoromethane, and dibromotetrafluoroethane were determined to be 22, 24, 53, 370, and 470 for temperatures of $22–28°\mathrm{C}$ . Most of the variability follows from uncertainty with measurements of tracer vapor-phase concentrations, with overall relative percent differences ranging from 8.5 to 25%. This methodology produces results consistent with literature values obtained from column tests, with similar reproducibility.