Journal of Environmental Engineering

Sensitivity analysis using importance ratios was applied to multivariate polynomial regression (MPR) models to make inferences about the nature and magnitude of fecal coliform (FC) sources in a combined sewer overflow-impacted stretch of the Passaic River at Paterson, New Jersey. The predictor variables in this study were temperature, discharge, precipitation, and upstream concentrations. The MPR models are applicable only for the current conditions with respect to pollutant sources. New models should be developed in case of any change in pollutant sources, by location or magnitude. This is a limitation that MPR models have in common with any empirical modeling approach, including multilinear regression or artificial neural networks. The performance of the MPR models using $R^2$ was significantly better than simple linear models using the same variables. The importance ratio, a dimensionless measure of model sensitivity, was used for comparison of the effects of different variables. Because model sensitivities, and therefore importance ratios, are not constant in nonlinear models, this work examines their distributions and relates them to system behavior, for example by showing under what conditions dilution does or does not affect FC concentrations in the stream. The analysis showed that MPR models and importance ratios can be used to provide significant information to better understand pollutant sources at a site and the relative importance of various predictor variables in explaining the variability in the FC concentrations.

A dual discharge strategy has been proposed for management of the effluent from the Syracuse Metropolitan Treatment Plant (Metro). The approach involves routing the discharge to the Seneca River when assimilative capacity is available there and to Onondaga Lake when it is not. Application of a deterministic modeling approach has demonstrated that the dual discharge strategy is effective in meeting water-quality standards/goals in both the river [dissolved oxygen (DO)] and the lake [total phosphorus (TP)] under summer average conditions of river flow and upstream boundary condition DO. Here, that analysis is extended to include a probabilistic treatment of the impact of natural variability in river flow and DO boundary conditions on the feasibility of this management option. Model simulations, incorporating these key sources of system variability, indicate that the dual discharge strategy will meet the lake management goal for TP $\sim 94\mathrm{\%}$ of the time, with no attendant violation of river DO standards. Excursions from the lake TP goal, occurring $\sim 6\mathrm{\%}$ of the time, range from $1–5\mu \text{g}\cdot {\text{L}}^{-1}$ , are within the range of uncertainty in indicators applied in identifying trophic status. This novel management option is compared with an in-lake discharge alternative in terms of technical and economic feasibility and public acceptance of resultant water quality. Additional management actions, recommended to accompany implementation of the dual discharge strategy, are discussed.

Effective porosity commonly represents only the voids in soils or rock that contribute to the advective transport of groundwater. In the extreme case, all the pores or fractures are interconnected and contribute to the transport of groundwater. However, in most cases, some pores or fractures are dead-ended or isolated and, therefore, do not contribute to the advective movement of water through the soil or rock mass. The effective porosity is often estimated to be some fraction of the total porosity. The purpose of this study was to compare a glacial marine clay deposit’s effective and total porosities. The inner connection of the soil pores and the importance of the clay minerals on the pore spaces are at the root of the effective porosity testing described herein. Based on the results of three tracer tests on a low-plasticity, glacial marine clay, the effective porosity was found to be approximately equal to the total porosity within an error of less than 10%. Based on visual appearance of this uniform clay, the longitudinal dispersivity was assumed to be small compared to the tracer specimen length. However, it was found that larger test specimens would have made the tracer breakthrough curves less complicated.

This study investigates the feasibility of using coal fly ash and fly ash-bentonite mixtures as a barrier material for mine waste. The hydraulic conductivity of the coal fly ash was measured to be in the order of $2\times {10}^{-9}\text{m}/\text{s}$ when it was permeated with deionized water, and this value decreased significantly when the permeant was switched to acid mine drainage (AMD). The addition of bentonite to coal fly ash lowered the hydraulic conductivity during water permeation but no further significant change was observed upon switching the permeant to AMD. Chemical analyses on the effluent from the hydraulic conductivity tests indicated that heavy metals present in AMD were attenuated and were well below the leachate criteria set by the Ontario Government. X-ray diffraction and scanning electron microscopy analyses results of postpermeation samples showed significant structural differences and formation of secondary minerals after AMD permeation. The results of this study suggest that the addition of 10% bentonite to coal fly ash reduced the hydraulic conductivity of the coal fly ash to less than $1\times {10}^{-9}\text{m}/\text{s}$ and improved the chemical compatibility for mine waste containment.

The oxygen decay coefficient is a key parameter used to predict the distribution of oxygen concentrations spatially and temporally in a waste rock pile. The present study proposes a new equation to calculate the oxygen decay coefficient based on the oxidation rate (sulfate release rate) of the waste rock, dry density, and equivalent porosity for oxygen transport. The equation gave oxygen decay coefficients that were of the same order of magnitude as those obtained from a semianalytic solution to the modified Fick’s law with an oxygen consumption term. Values were in the range of $3.74\times {10}^{-8}{\text{s}}^{-1}$ for air dry waste rock and $3.99\times {10}^{-7}{\text{s}}^{-1}$ for moist waste rock. The effect of water addition frequency on the oxidation rate and the oxygen decay coefficient was investigated through four column experiments with various flushing rates and a laboratory case simulating actual precipitation at a specific site. The results indicated that the oxygen decay coefficient was dependent on not only the oxidation rate but also on the physical characteristics of the waste rock, such as porosity and dry density. The flushing rate had a significant influence on the oxidation rate of the waste rock and the calculated oxygen decay coefficient. The oxidation rate of the waste rock decreased from $1.19\times {10}^{-6}$ to $5.32\times {10}^{-7}{\text{s}}^{-1}$ with an increase in flushing intervals from 1 week to 4 weeks. When the drying period was longer than 3 weeks, the oxidation rate decreased very slowly with an increase in drying period for the tested waste rock.

Biological and abiotic sorptions as well as kinetic experiments were performed to elucidate the mechanism by which color was being removed from paper mill effluents using anaerobic composting. Experiments were performed using pulp mill upset tank wastewater $\left(\text{color}=\mathrm{5,500}\text{PCU}\right)$ and E stage filtrate $\left(\text{color}=\mathrm{10,300}\text{PCU}\right)$ . Color removal experiments using active and gamma sterilized compost showed that the color removal capacity for both wastewaters was nine times higher when using active compost than for those reactors using gamma sterilized compost. Final decolorization for pulp mill upset tank and E stage filtrate was 91 and 83%, respectively, while only 33% decolorization was achieved with gamma sterilized compost. Kinetic tests also showed higher color degradation rates when using active compost compared to sterilized compost. Additional experiments demonstrated that biological color removal appears to be robust with respect to pH and is largely unaffected by pH over a range from pH 5 to 10, typical values for the effluents in paper mills. The effect of aging in sorption were tested and results showed that virgin compost could establish a microbial population in less than 50 days which resulted in a compost with sorption capacity similar to the aged compost.

Anaerobic biodegradation in sewage sludge of polyhydroxybutyrate (PHB) was investigated. Evolved gaseous carbon was measured to assess biodegradability according to ASTM D5210. Mass-loss experiments were performed to determine degradation kinetics. Changes in the polymer properties were investigated. The impact of a natural plasticizer [tributyl citrate (TBC)] on biodegradation was determined. Polylactic acid was also biodegraded for comparison. Melt-pressed plates of PHB (with thicknesses of 0.24, 0.5, 1.2, 3.5, and 5.0 mm) were biodegraded to investigate the relationship between initial mass:initial surface area ratios and decay rates. Scanning electron microscopy micrographs of degraded specimens were recorded for visual illustration of the degradation process. A relationship between initial mass:initial surface area and degradation rates indicates that the thickness and surface area of the material affect its degradation. The degradation rates were impacted by the sewage sludge activity. TBC additive hindered PHB’s rate of degradation. Thermal properties, molecular bonding, and molecular weight measured by differential scanning calorimetry, Fourier transform infrared, and size exclusion chromatography, respectively, were only slightly affected by biodegradation, indicating that recycling PHB will not affect its performance.

A filamentous fungal strain (Penicillium expansum BS30) isolated from a municipal wastewater treatment plant was used in this study to simultaneously reduce sludge solids, pathogens, and improve the sludge settling and dewaterability [simultaneous solids and pathogens reduction, settling and dewatering (SSPRSD)] in shake flask and 10-L bioreactor experiments. The fungal strain role in the SSPRSD process was evaluated at different temperatures and inoculum (spores) concentrations. The best performance of the process was achieved at incubation temperature of $25°\text{C}$ and inoculum concentration of ${10}^6\text{spores}/\text{mL}$ . At these optimal conditions, suspended solids (SS) and volatile SS were degraded $>50$ and $>53\mathrm{\%}$ , respectively. The capillary suction time value recorded $\left(<13\text{s}\right)$ was lower than that required for sludge dewaterability $\left(<20\text{s}\right)$ . The populations of total coliforms and Salmonella (pathogen indicators) were reduced by two and four log cycles, respectively. A study on molecular screening of penicillin biosynthesis gene cluster and toxic organic compounds degrading machinery of the fungal strain was also conducted. It was found that the fungal strain possessed the penicillin-producing gene and toxic organic compounds degrading genes, and therefore may be helpful in degrading these compounds.

The importance of bacteria in catalyzing microbially induced concrete corrosion was evaluated. Experiments were conducted to determine the optimum pH and growth kinetics of four selected bacterial strains (Thiobacillus neapolitanus C2, Thiobacillus thioparus H1, Acidithiobacillus thiooxidans, and Acidiphilium cryptum LHET2). Combinations of these strains were inoculated into flasks containing $\sim 42\text{g}$ concrete blocks half-submerged in 600 mL of synthetic wastewater with hydrogen sulfide in the headspace air. Controls not inoculated with bacteria lost 0–3 mg/g concrete over 227 days; in the aqueous phase the minimum pH was 6–6.7 and 19–23 mg of calcium/g concrete was released. Systems inoculated with two species of neutrophilic sulfur oxidizing microorganisms (SOM) lost 8 mg/g concrete; in the aqueous phase the minimum pH was 4.5 and 25 mg of calcium/g concrete was released. The concrete samples incubated with neutrophilic and acidophilic SOM and an acidophilic heterotroph experienced the greatest deterioration, with a total mass loss of 13 mg/g concrete, minimum aqueous pH of 3.0, 28 mg calcium/g concrete released, and 47 mg sulfate/g concrete produced.

Removal of nonpolar contaminants such as most organic compounds are transported primarily by electroosmosis in electrokinetic remediation, thus the process is effective only if the contaminants are soluble in pore fluid. Hydrophobic organic compounds such as hexachlorobenzene (HCB) and phenanthrene (PHE) can adsorb strongly to clayey soil. Therefore, in this study, enhancements were done by adding 2-hydroxylpropyl- $\beta$ -cyclodextrin surfactant and ultrasonication comparably to assist the electrokinetic treatment in improving the mobility of these hydrophobic compounds. The results show that HCB and PHE were mobilized and removed in both cases. But HCB is more difficult to remove than PHE, because of its highly stable nature and low water-solubility property. Ultrasound-assisted test performed better PHE reduction than surfactant-assisted test, because ultrasound can degrade the contaminant through oxidation by free radicals.