Journal of Environmental Engineering

The sorption kinetics and equilibrium endpoints of two widely prescribed anionic lipid-regulating pharmaceuticals—atorvastatin and simvastatin acid—were evaluated for wastewater-treatment plant primary clarifier biosolids, a peat soil, a sandy soil, and a stream sediment. All equilibrium isotherms were linear over an aqueous concentration range of $0.01\mu \text{g}/\text{L}$ to greater than $100\mu \text{g}/\text{L}$ . $\text{Log}{K}_{\text{oc}}$ values for statin sorption to biosolids were 2.91 and 2.96 for atorvastatin and simvastatin acids, respectively. Comparative isotherm experiments with the peat soil, sandy soil, and stream sediment found $\text{log}{K}_{\text{oc}}$ values for atorvastatin of 2.96, 2.70, and 3.20, respectively, and values of 2.89, 2.81, and 3.33 for simvastatin acid, respectively. Sorption was noncompetitive between the two statin drugs. Temperature changes did not affect sorption of either statin over the range of $5–32°\text{C}$ , indicating that heats of sorption were near zero. Taken together, these observations suggest that despite its anionic structure, statin sorption occurs via partition (solubilization) of the hydrophobic part of the molecule into the sorbent organic matter. Results from kinetic experiments show that statin sorption to biosolids reaches equilibrium much more rapidly compared to the soils and sediment, as the mass-transfer-rate coefficient, $\alpha$ , for the two-site equilibrium/kinetic model is approximately one-order-of magnitude higher for the biosolids. Presentation of these sorption data provides a requisite first step for future studies of statin fate and transport in wastewater-treatment plants and the environment.

This bench-scale study was conducted to evaluate the stabilization of mercury (Hg) and mercuric chloride-containing surrogate test materials by the chemically bonded phosphate ceramics technology. This study was performed as part of a U.S. EPA program to evaluate treatment and disposal alternatives to the current land disposal restriction (LDR) treatment standards for mercury. The stabilized materials were subjected to a suite of leaching tests: one test characterized the solubility and release behavior of mercury as a function of pH between the pH values of 2 and 12; the second test used the toxicity characteristic leaching procedure (TCLP); and the third leaching test used the TCLP “cage” modification. TCLP results showed that leachability of Hg decreased by approximately two orders of magnitude and a maximum of five orders of magnitude. The three leachability test methods produced similar amounts of leached mercury, but the test that studied mercury solubility as a function of pH released slightly higher levels (at pH 2) compared to the TCLP methods. On comparing the results obtained with the standard TCLP and the TCLP cage modification, we learned that the leachates from stabilized wastes containing 50 wt % loading of elemental Hg and ${\text{HgCl}}_2$ were within the LDR requirements. However, wastes containing higher loadings (i.e., 70 wt % loading of Hg and ${\text{HgCl}}_2$ ) had leachate concentrations exceeding the 0.2 mg/L treatment standard and therefore would not meet the Resource Conservation and Recovery Act disposal requirements.

A novel application of ultraviolet (UV) light emitting diodes (LEDs) as a light source for the degradation of organic contaminant has been investigated. Photocleaving of hydrogen peroxide $\left({\text{H}}_2{\text{O}}_2\right)$ via UV LEDs photolysis resulted in the generation of hydroxyl radicals. It was found that phenol removal was insignificant in the absence of hydrogen peroxide, therefore oxidation of phenol was attributed to the formed radicals. Two criteria were selected to provide detailed information on the performance of UV LEDs in phenol oxidation: (1) the reaction quantum efficiency and (2) the energy consumption. Statistical tools such as the response surface methodology and the ANOVA were applied to estimate the influence of various process parameters such as the wavelength (255, 269, and 276 nm) and ${\text{H}}_2{\text{O}}_2$ to phenol molar ratio (5, 50, and 100) on phenol degradation reaction quantum efficiency. The decay of phenol (initial concentration of 1.06 mM) was the most pronounced at 255 nm and ${\text{H}}_2{\text{O}}_2$ to phenol molar ratio of 50. Finally, the “figure-of-merit” was used to estimate the specific energy consumption of the UV LED-based process.

An integrated technique containing coagulation, ultraviolet/Fenton oxidation, and pressurized biological processes was provided for the treatment of wastewater generated from drilling operation where sulfonated muds were used. Ultraviolet/Fenton oxidation process was used to improve biodegradability of effluent after coagulation [assessed through a ratio of biological oxygen demand to chemical oxygen demand (COD) (B/C) index]. Pressurized biological experiments were used to further remove COD so as to meet the wastewater discharge standard. The results showed that coagulation pretreatment could help remove most of CODs (70–80%) in drilling wastewater. A 57% reduction in COD was obtained in the ultraviolet/Fenton oxidation process with 0.8 $Q\text{th}$ ${\text{H}}_2{\text{O}}_2$ (in 30 min), and the biodegradability was significantly improved (B/C was increased from 0.03 to 0.47). The pressurized biological process could help speed up the reaction process with a saved aeration time of 66.7% under a system pressure of 0.2 MPa (in comparison with the condition of a normal pressure). The overall COD removal efficiency was about 95% and the COD level in the final effluent was less than 100 mg/L, which satisfied the wastewater discharge standard.

The industrial solvent trichloroethylene (TCE) is among the ubiquitous chlorinated organic compounds found in groundwater contamination. The objective of this study was to evaluate the potential of applying basic oxygen furnace (BOF) slag as the catalyst to enhance the Fenton-like oxidation to remediate TCE-contaminated groundwater. Results indicate that TCE oxidation via the Fenton-like process can be enhanced with the addition of BOF slag. Results from the X-ray powder diffraction analysis reveal that the major iron type of BOF slag/quartz sand media was iron oxyhydroxide $\left(\alpha {\text{-Fe}}_2{\text{O}}_3\right)$ . Approximately 81% of TCE removal was observed (with initial TCE concentration of approximately $5\text{mg}{\text{L}}^{-1}$ ), with the addition of $1,000\text{mg}{\text{L}}^{-1}$ of ${\text{H}}_2{\text{O}}_2$ and $10\text{g}{\text{L}}^{-1}$ of BOF slag. Results also show that TCE concentrations dropped from 5 to $1.1\text{mg}{\text{L}}^{-1}$ , and chloride concentrations increased from 0 to $2.7\text{mg}{\text{L}}^{-1}$ after 60 min of reaction with the presence of ${\text{H}}_2{\text{O}}_2$ and BOF slag. This indicates that the depletion of TCE corresponded with the oxidation reactions and release of chloride ions very well in this study. Results demonstrate that the BOF slag can be used to supply catalysts continuously, and it can be installed in a permeable barrier system to enhance the Fenton-like process in situ.

The effect of microwave (MW) field on the rate of thermal desorption of polychlorinated biphenyls (PCBs) from long-term contaminated soil was examined in the laboratory environment. For these purposes a modified MW oven was used, with a uniformly extended MW field and a power consumption of 200–600 W. The weight of the soil samples was 100 g, the sum of concentrations of seven indicative congeners of PCB Nos. 28, 52, 101, 118, 153, 138, and 180 was, on average, 264 mg/kg of dry matter. It was experimentally proven that the efficiencies of PCB desorptions were high, over 99.9%. The maximal desorption temperature of $600°\text{C}$ was reached within 15–17 min. It came to light that the presence of alkaline additives in the soil (such as carbonates and alkaline metal hydroxides) did not have an apparent effect on the desorption of PCBs under those conditions. The results concerning the efficiency of PCB separations are in agreement with our previous findings regarding the efficiency of thermal desorption without using MWs in the pilot (input 35 kg) and industrial (input 15 t) desorption chambers with a stationary layer of the same type of contaminated soil. The main disadvantage of experiments with thermal desorption without the action of MWs was the low rate of heating up the soil. This study was focused to solve the problem of contamination in a complex way; we also studied the effect of MWs on the rate of the deterioration of the separated PCBs in aqueous condensates, the deterioration of PCBs in contaminated waste water containing alkaline agents (soda and lye), and on the catalytic reductive dechlorination of PCBs in the system Pd supported on active coal with sodium formate as the hydrogen donor. Experiments with the MW-enhanced catalytic reductive oxidation show over 98.5% reduction in the concentration of PCBs. An important and new finding is the more than 98% reduction in the concentration of PCBs when the MW field was applied on the contaminated water into which only 2.5% of ${\text{Na}}_2{\text{CO}}_3$ was added. Further studies on possible influences of MWs on the reaction kinetic are needed. Meanwhile we attribute the positive MW effects to their thermal properties rather than to their influence on the reaction mechanism.

The performance of a down-flow hanging sponge (DHS) system was continuously evaluated for 1 year for enhancement of organic matter and nutrient removal in the treatment of presettled municipal wastewater. A pilot-scale DHS (24 L) was installed at a wastewater-treatment site and operated at an ambient temperature of $25°\text{C}$ . This paper reports on the results of a long-term monitoring of the system. The DHS system was operated at three different hydraulic retention times (HRTs), i.e., 6, 4, and 2 h. The available results showed that increasing the HRT significantly improved the removal of chemical oxygen demand (COD) fractions. The removal efficiencies of COD were 89, 80, and 56% at HRTs of 6, 4, and 2 h, respectively. Also, ammonia $\left({\text{NH}}_4–\text{N}\right)$ concentration significantly decreased by increasing the HRT. Ammonia removal percentages of 99, 90, and 72% were achieved when the DHS system was operated at HRTs of 6, 4, and 2 h, respectively, but decreasing HRT exerted a slightly negative effect on the removal of total phosphorous. Scanning electron microscopy observation revealed no clogging of the sponge pores after 12 months of continuous operation. Accordingly, the results suggested that the proposed system may be a competitive solution for municipal wastewater treatment under variable conditions.

This research was aimed at recovering Fe and Al compounds to produce a useful complex coagulant from fly ash using ${\text{H}}_2{\text{SO}}_4$ and ${\text{SO}}_2$ from flue gas oxidized to ${\text{SO}}_3$ by ${\text{NaClO}}_3$ . The reaction kinetics of wet ${\text{SO}}_2$ scrubbing from simulated flue gas with fly ash slurry was studied. The ${\text{SO}}_2$ scrubbing experiments were carried out in a jacketed glass reactor system with a simulated flue gas containing ${\text{SO}}_2$ and ${\text{N}}_2$ in the gas phase and fly ash slurry in the liquid phase. Sodium chlorate was added to oxidize ${\text{SO}}_2$ to ${\text{SO}}_3$ , adding ${\text{H}}_2{\text{SO}}_4$ in the slurry. The reaction orders of both ${\text{Fe}}_2{\text{O}}_3$ and ${\text{Al}}_2{\text{O}}_3$ extraction from fly ash slurry were shown to be 1.5. The empirical Arrhenius expressions were also derived from the reaction rate constants obtained at each reaction temperature. The mass transfer process of ${\text{SO}}_2$ with ${\text{ClO}}_3^{-}$ was evaluated using a two-film theory model.

The reservoir concept for flow modeling has been generalized for the purpose of the parsimonious modeling of combined sewer overflow pollution. Conceptual models have been used for the buildup and washoff of pollutants on the paved surfaces, and the transport of these pollutants in the sewer system (advection, dispersion, sedimentation, and resuspension). For the parsimonious modeling of the water quality of the sewage in the effluent of the combined sewer system, the conceptual submodels of these different processes were lumped into one single model equation. When ancillary structures such as a storage sedimentation tank are present at the combined sewer overflow, the additional effect of advection, dispersion, storage, and sedimentation is considered in a similar parsimonious conceptual way. Such a parsimonious model aims to reduce the model complexity, and therefore the number of calibration parameters. In most practical cases of urban drainage modeling, water quality data are extremely limited and consequently only a small number of parameter values can be identified from the data. The proposed model is tested on the basis of 10-min and hourly concentration measurements for total suspended solids, settleable solids, biochemical oxygen demand, and ammonia at the outlet of the combined sewer system of the village of Dessel (Belgium), which were available in this case only for six overflow events.

A new approach that links genetic algorithm (GA) as an optimization tool with Monte Carlo simulation (MCS)-based reliability program is presented for reliability-constrained optimal design of water treatment plant (WTP). The reliability of a WTP is defined as the probability that it can achieve the desired effluent water quality standard (WQS). The objective function minimizes the treatment cost, subjected to design and performance constraints, and to achieve desired reliability level for meeting the given effluent WQS. The random variables used to generate the reliability estimates are suspended solids (SS) concentration, flow rate, specific gravity of floc particle, temperature of raw water, sedimentation basin performance index, and model coefficients. The application of GA-MCS approach for design of a WTP is illustrated with a hypothetical case study. The annualized cost of WTP is affected by the number of uncertain parameters included in the analysis, coefficient of variation of uncertain parameters, effluent WQS, and target reliability level. Analysis suggests that higher reliability at lower annual cost of treatment can be achieved by limiting the fluctuation of uncertain parameters. Results show that distribution of effluent SS is also affected by the uncertainty. The suggested GA-MCS approach is efficient to evaluate treatment cost-reliability tradeoff for WTP. Results demonstrate that the combination of GA with MCS is an effective approach to obtain the reliability-constrained optimal/near-optimal solution of WTP design problem consistently.

Storage tanks are commonly installed in a combined sewer system to control the discharge of combined sewer overflows that have been identified as a leading source for receiving water pollution. The traditional approach to determine the distribution of storage tank volume in the sewer system is confined to the use of objectives within the system itself due to the limits of separate modeling of urban wastewater systems, consisting of the sewer system, wastewater-treatment plant, and receiving water. The aim of this study is to investigate the optimal distribution and control of storage tanks with an objective to mitigate the impact of new residential development on receiving water quality from an integrated modeling perspective. An integrated urban wastewater model has been used to test three optimization scenarios: optimal flow rate control, storage distribution, and a combination of these two. In addition to the cost of storage tank construction, two receiving water quality indicators, dissolved oxygen and ammonium concentration, are used as optimization objectives. Results show the benefits of direct evaluation of receiving water quality impact in the context of storage distribution optimization. Results indicate that storage allocation should be considered in conjunction with optimal flow rate control to achieve the maximum effectiveness in water pollution mitigation.

A study was conducted to evaluate the performance of locally available electric arc furnace slag (EAFS) as a substrate for removing phosphorus from wastewater. First, in a laboratory study, EAFS was found to have high phosphorus removal efficiency for three P concentrations (0.3, 3.0, and 6.0 mg/L); this resulted in nearly 100% phosphorus removal in 24 h. Next, the experiment was repeated using aeration and similar phosphorus removal was observed but in a shorter contact time of 1 h. The adsorption capacity of EAFS was determined to be 1,458 mg/kg. In a pilot-scale study, over 90% P removal took place in the first 4 h under nonaerated conditions, and nearly 100% removal in 8 h. While the P removal with aeration was relatively less initially for the shorter residence times, a 100% removal was observed for the 24-h residence time.