Journal of Environmental Engineering

The implementation and operation of wastewater treatment plants are fundamental actions for environmental water body pollution control that generally involve large amounts of financial resources. Hence, employment of optimization techniques for decisions about the minimum required wastewater treatment plant efficiencies might be very useful. In this study, an optimization technique known as the genetic algorithm (GA) was combined with a water-quality model to determine the minimum efficiencies for sewage treatment in watersheds. Combinations of the optimization technique and models that incorporated environmental quality standards for the parameters of dissolved oxygen (DO), biochemical oxygen demand (BOD), and equity measures among sewage treatment systems, either as constraints or in the objective functions, were developed. These combinations were applied to the Santa Maria da Vitória river watershed, located in the State of Espírito Santo, Brazil, considering possible effluent disposal scenarios and implementation of different established optimization models. The developed combinations of the genetic algorithm and a water-quality model demonstrated to be versatile and efficient tools for determining the minimum sewage-removal efficiencies for wastewater treatment plants in watersheds. Among the developed combinations of optimization models, the best results, or minimum costs, were obtained when the rivers’ self-depuration capabilities were taken into account.

A continuous in-stream water quality measurement (CWQ) study was carried out in two Lincoln, Nebraska urban watersheds. Discrete stormwater samples were collected at the study sites during 17 storm runoff events over a three-year period. In-stream flow and water quality (e.g., turbidity) measurements were combined with climatic data to develop multiple-linear regression (MLR) models for the estimation of six stormwater pollutant concentrations [i.e., total suspended solids (TSS), soluble reactive phosphorus (SRP), total phosphorus (TP), nitrate plus nitrite-nitrogen ($N+N$), total Kjeldahl nitrogen (TKN), and Escherichia coli (E. coli)]. MLR concentration models based on in-stream measurements (CWQ-C) were developed to estimate pollutant concentrations at any time during a storm. Three additional MLR models were developed to estimate event mass loads based on (1) climatic data only, (2) both CWQ and climatic data (CWQ-L), and (3) use of literature event mean concentrations (simple mass load). The comparison suggests that for small, urban watersheds, using correlated in-stream water quality and flow measurements along with climatic data (e.g., CWQ-L models) best captures variability, especially for TSS, SRP, and TP. The study also showed that nitrate atmospheric deposition data improved the N+N and TKN Climatic and CWQ-L load models.

A ring-shaped disinfection apparatus has been developed containing twenty ultraviolet-light-emitting diodes (UV-LEDs) with emission at 285 nm. The apparatus was applied to Escherichia coli, $Q\beta$, MS2, and adenovirus in water. The reduction-equivalent fluence in the apparatus was determined, based on a modification of the protocol for the bench-scale challenge test by low-pressure (LP) UV lamp systems (LPUV). All species demonstrated log-linear inactivation profiles versus the fluence, and the inactivation rate constants for E. coli, $Q\beta$, MS2, and adenovirus were 0.157, 0.037, 0.029, and $0.023{\mathrm{cm}}^2/\mathrm{mJ}$, respectively. The inactivation rate constant for adenovirus under the UV-LED exposure ($k_{\mathrm{UV}\text{-}\mathrm{LED}}^{\prime }$) was higher than that under a LPUV lamp ($k_{\mathrm{LPUV}}^{\prime }$), and the ratio of $k_{\mathrm{UV}\text{-}\mathrm{LED}}^{\prime }$ to $k_{\mathrm{LPUV}}^{\prime }$, which is approximated as a germicidal factor at 285 nm, was 1.15 for adenovirus. To conclude, this study demonstrated a high potential of the 285 nm UV-LEDs to inactivate microorganisms in water. The germicidal factor found for adenovirus implies that the 285 nm UV-LED could be a good option to inactivate adenovirus in water.

Exposure to lead in drinking water poses a risk for various adverse health effects, and significant efforts have been made to monitor and eliminate lead exposure in drinking water. This study focused on the localization of lead exposure from 71 drinking water fountains in nonresidential buildings in order to determine the source of elevated lead and understand the effects of fountains associated with lead concentration in drinking water. Drinking water fountains containing lead-lined cooling tanks and brass fittings were found to release lead concentrations in excess of $10\mathrm{\mu g}/\mathrm{L}$, and fountains with low or infrequent usage and those with cooling tanks produced the highest concentrations (in excess of $20\mathrm{\mu g}/\mathrm{L}$) of lead. One particular fountain model found at several locations throughout the institution was associated with some of the highest lead concentrations measured throughout the study. This fountain was recalled in the United States, but not in Canada. This article adds to existing research demonstrating that drinking water fountains are a potentially significant and underappreciated source of lead exposure in nonresidential buildings.

This work determined the effect of a combination of microwave irradiation and sodium persulfate (${\mathrm{Na}}_2{\mathrm{S}}_2{\mathrm{O}}_8$, SPS) on the decomposition of landfill leachate. The effect of treatment temperature, $T$(60–90°C), SPS concentration, [SPS], (0.05–0.30 M), and solution pH (3.0–8.4) were characterized. As $T$ increased from 60 to 90°C, the observed degradation rate constant of total organic carbon (TOC), $k_{\text{obs}}$, in landfill leachate increased from 0.0032 to $0.0704{\min }^{-1}$. The value $k_{\text{obs}}$ fitted the Arrhenius equation and yielded an apparent activation energy of $104\mathrm{kJ}/\mathrm{mol}$. As [SPS] increased from 0.05 to 0.3 M, $k_{\text{obs}}$ increased from 0.0075 to $0.0974{\min }^{-1}$. It decreased as pH increased. Within the design boundaries, $T$ ($p<0.01$) significantly affected the TOC removal of landfill leachate but [SPS] did not ($p>0.05$). The results demonstrate that microwave-assisted persulfate oxidation can adequately remove organics from landfill leachate.

Changes in temperature and precipitation patterns due to global warming are likely to affect the quantity and quality of water in different water bodies. Water temperature modeling techniques are usually employed to study the effects of global climate change on stream and river ecosystems. This study aims to identify a suitable air–water temperature relationship for a small aquatic pond in a semiarid region of India and examine the effects of increased water temperature on the small pond’s attributes. The performance of two parametric statistical models—simple linear regression (SLR) and four-parameter nonlinear logistic regression (NLR) models—was evaluated. The developed models were field tested for mean, minimum, and maximum air–water temperatures on daily, weekly, and monthly timescales. The model parameters were estimated from the measured air–water temperature time-series data using the least-squares optimization method. Model performance was evaluated using three statistical indicators—the index of agreement ($d$), Nash–Sutcliffe modeling efficiency ($E$), and root mean square error (RMSE). The performances of the SLR and NLR models were found to be comparable for all three data series and timescales. However, the NLR model was found to perform relatively better compared to the SLR model for all three timescales. Results also revealed better correlations between the measured and simulated water temperatures on weekly and monthly timescales compared to the daily timescale. Application of the SLR model for projecting changes in attributes of a small aquatic pond in a semiarid region of India under changing climate scenarios revealed a 1.3 to 3.7°C increase in pond water temperature with increases in air temperature from 1.5 to 4.3°C by the end of 2080. This increase in water temperature will cause the water evaporation rate to increase by 8.3–30.3% and the hydroperiod and saturated dissolved oxygen to decrease by 3–26 days and 2.2–6.5%, respectively.

A waste management model associated with public-private partnerships (WMMPPP) was formulated and applied to the City of Hamilton, Ontario, Canada. The WMMPPP has the advantages of considering a combination of public and private services so that trade-offs between system costs and service quality can be addressed. Meanwhile, uncertain information presented as interval numbers can be effectively communicated into the optimization processes such that feasible decision alternatives can be made through the interpretation and analysis of the interval solutions according to projected applicable system conditions. The model minimizes the inexact costs (direct costs, indirect costs, and penalties) under three waste-service-delivery scenarios: (1) 100% in-house public services, (2) a combination of public and private services, and (3) 100% private services. These three scenarios covered most types of the municipal solid waste (MSW) management systems in North American municipalities. The results indicated that reasonable solutions were generated through the WMMPPP under different scenarios. Most importantly, the risk of total system costs would increase with the decrease of service quality due to privatization in Hamilton. This study is potentially useful for MSW decision-makers in most municipalities of North American for long-term planning of regional waste management activities and for formulating related local policies/regulations regarding privatizing the service delivery in waste management. It is recommended that more-complex and hybrid inexact programming models based on the WMMPPP be further developed.

Adsorbable organic halogens (AOX) were measured at the outlet (${\mathrm{AOX}}_{\mathrm{o}}$) and after 24 h contact time with residual disinfectant (${\mathrm{AOX}}_{24\mathrm{h}}$) for 10 samples obtained from 7 drinking water treatment plants (WTPs) that employ chlorine-based disinfectants. ${\mathrm{AOX}}_{\mathrm{o}}$ ranged from 0.75 to 7.60 μM ($26.2–266.0\mathrm{\mu g}\mathrm{Cl}/\mathrm{L}$) and increased by up to 170% after 24 h contact time. The results were also compared with AOX formation potential (${\mathrm{AOX}}_{\mathrm{FP}}$) measured in the laboratory for the samples collected prior to disinfection at the same WTPs. In general, ${\mathrm{AOX}}_{24\mathrm{h}}$ and ${\mathrm{AOX}}_{\mathrm{FP}}$ values varied by less than $\pm 20\%$. A suite of disinfection byproducts (DBPs) were individually measured to elucidate the AOX composition. Trihalomethanes and haloacetic acids explained the largest fraction of AOX; however, the percentage of AOX not accounted for by measured DBPs varied greatly between samples (14.5–62.0%). Additionally, the fate of ${\mathrm{AOX}}_{\mathrm{FP}}$ was assessed across the seven WTPs. On average, coagulation removed $67\pm 7\%$ of ${\mathrm{AOX}}_{\mathrm{FP}}$ across the WTPs, while dual media filtration did not substantially remove ${\mathrm{AOX}}_{\mathrm{FP}}$. The effect of ozone on ${\mathrm{AOX}}_{\mathrm{FP}}$ varied between WTPs, while biological activated carbon filtration removed $33\pm 13\%$ ${\mathrm{AOX}}_{\mathrm{FP}}$. The ratio of known versus unknown ${\mathrm{AOX}}_{\mathrm{FP}}$ did not change across the WTPs.

The gas extraction wells installed in landfills are used to control gas emission. The degradation of municipal solid waste (MSW) is the main influencing factor for gas production and migration. The symmetric equation of gas migration was established considering the gas extraction wells and peak behavior of the degradation rate. An analytical solution is presented. The peak behavior of degradation rate can be modeled by an equation. The steady degradation ratio of MSW is related to methane generation potential $L_o$ in the LandGEM model. The extraction and injection tests can be well simulated by the symmetric change theory of gas pressure in landfills. From back analysis of the Brogborough test, both the MSW landfill degradation rate and the peak value of gas pressure increased with sludge addition. The degradation time at peak is less than about 700 days. The peak gas pressure in landfill with added sludge increases by 20%.

Groundwater at many existing or former industrial areas and underground storage tank sites is contaminated by petroleum hydrocarbons. In this study, a column experiment was applied to evaluate the effectiveness and mechanisms of sulfate reduction processes on the bioremediation of benzene, toluene, and methyl-$t$-butyl ether (MTBE) contaminated groundwater. Simulated anaerobic groundwater containing benzene, toluene, and MTBE (average concentration = $20\mathrm{mg}/\mathrm{L}$) was pumped into the system at a flow rate of $0.36\mathrm{mL}/\min$. Sulfate (used as the electron acceptor) was injected into the system to activate the sulfate-reducing process. Anaerobic sludge collected from an anaerobic basin of an industrial wastewater treatment plant was inoculated into the system to enhance the sulfate reduction rate. Up to 92, 65, and 45% of toluene, benzene, and MTBE removal efficiencies were observed with the first-order decay rate of 34, 1.8, and $11/\mathrm{d}$, respectively. Results indicate that toluene is more biodegradable under sulfate-reducing conditions compared to benzene and MTBE, and $0.7\mathrm{g}/\mathrm{L}$ of sulfate consumption was observed during the biodegradation process. The occurrence of sulfate reduction can be confirmed by the increased sulfide (increased from 7–9 to $340–520\mathrm{mg}/\mathrm{L}$) and ferrous iron (increased from $<0.1$ to $52\mathrm{mg}/\mathrm{L}$, then dropped to $0.14\mathrm{mg}/\mathrm{L}$ attributable to the formation of iron sulfide) concentrations. In the latter part of this study, accumulation of hydrogen sulfide caused the microbial inhibition, and thus, decreased contaminant removal efficiencies were observed. The microbial communities were characterized by 16S rRNA-based denaturing gradient gel electrophoresis (DGGE) profiling for soils in the system. Results show that sulfate addition could result in the enhancement of sulfate reducer growth, and thus, sulfate reduction becomes the dominant biodegradation process. A total of 39 different petroleum-hydrocarbon degrading bacteria were observed under the sulfate-reducing conditions. Results indicate that the sulfate reduction has the potential to be developed into a practically and economically acceptable technology to remediate petroleum-hydrocarbon contaminated groundwater.

High concentrations of nitrate-nitrogen degrade the quality of aquatic environments. The primary mechanism by which nitrate-nitrogen is removed (denitrification) requires anoxic conditions and electron donors. While removal of total and ammonium-nitrogen is often high in stormwater biofilters, poor removal or even the release of nitrate-nitrogen in the outflow has often been observed. Five Perspex biofilter columns (94 mm internal diameter) were fabricated with a filter layer that contained 8% organic material. Columns were operated at $875\mathrm{mm}/\mathrm{h}$ and fed with simulated stormwater with different antecedent dry days (ADDs) and concentrations of nitrate-nitrogen. Samples were collected from the outflow at different time intervals between 2 and 150 min and were tested for nitrate-nitrogen. The removal of nitrate-nitrogen varied during an event from a high removal percentage (60–90%) in the initial outflow that gradually decreased in the first 30 min and settled at 0–15% removal thereafter. This remained consistent during all simulated events independent of the number of ADDs or inflow concentrations. ADDs and previous event feed concentrations affected the outflow nitrate-nitrogen concentration in the first 30 min of the current event. Therefore, from this study it is concluded that denitrification within stormwater biofilters occurs mainly during drying periods rather than wetting periods.

An increasing number of municipalities are encouraging homeowners to implement on-site residential stormwater management. In some communities, this encouragement takes the form of a stormwater utility fee or rain tax that may be reduced if homeowners take measures to reduce runoff. The most commonly cited techniques for reducing runoff are disconnecting downspouts or installing rain barrels, rain gardens, or permeable pavements. The analysis presented here examines the hydraulic performance of the less commonly recommended residential stormwater infiltration gallery designed to reduce off-site runoff from roof gutters. Case study simulation results based on a 10-year precipitation record for Cleveland, Ohio, indicate that a 30-m (100-ft) infiltration gallery sitting atop soil with a modest infiltration rate of $0.64\mathrm{cm}/\mathrm{h}$ ($0.25\mathrm{in.}/\mathrm{h}$) could attain a single downspout roof service-area runoff reduction of 90%, and a 61-m (200-ft) gallery could attain a whole roof runoff reduction of more than 85%. This performance is superior to that expected from rain barrels or modest-size rain gardens, and the operation-free and low-maintenance gallery would address many of the concerns often expressed by homeowners about other stormwater-management options.

The removal of benzene from industrial wastewaters is investigated in this work, through photocatalytic degradation processes using nanocomposite particles. A series of polyaniline/anatase ${\mathrm{TiO}}_2$ (${\mathrm{PANI}/\mathrm{TiO}}_2$) nanocomposite powders with different ${\mathrm{PANI}:\mathrm{TiO}}_2$ ratios were prepared by in situ deposition oxidative polymerization of aniline hydrochloride. Several tools, such as Fourier transform infrared spectroscopy (FTIR), X-ray crystallography (XRD), particle-size analyzer (PSA), and scanning electron microscopy (SEM) were used to investigate the nanocomposite structure and composition. The effects of important parameters such as type of catalyst, initial benzene concentration, pH, and degradation time have been investigated on the rate of removal of benzene. The results show that the ${\mathrm{PANI}\text{-}\mathrm{TiO}}_2$ composite has the potential viability to be used as a photodegradable material. The results show that photocatalytic degradation in the solid polymer matrix proceeds much faster than direct photolytic degradation in the open atmosphere. The removal percent of benzene with a nanocomposite type of [$5:1$] of ${\mathrm{PANI}/\mathrm{TiO}}_2$ in the ambient temperature with an optimum pH of 7 in a 120-min period is 99.22% under solar radiation and 98.95% under ultraviolet (UV) radiation.