Journal of Environmental Engineering

Sulfur was impregnated onto activated carbon fibers (ACFs) through ${\mathrm{H}}_2\mathrm{S}$ oxidation catalyzed by the sorbent surface in a fixed-bed reactor. By changing the temperature and duration of the sulfur impregnation process, ACFs with different sulfur contents were developed. Characterization of ACFs before and after sulfur impregnation was conducted by surface area analysis, energy dispersive X-ray analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy, and temperature programmed desorption. Vapor phase mercury adsorption experiments were carried out in a fixed-bed reactor. Sulfur was impregnated mainly as elemental sulfur and the amount of sulfur deposited on the ACF increased with an increase in impregnation temperature. Higher temperature leads to more uniform sulfur distribution inside the sorbent pores. The impregnation process can be explained by a combination of pore filling and monolayer adsorption, with the former mechanism predominating at low temperatures. In the absence of sulfur, the mercury adsorption capacity can be correlated with surface area and pore volume.

Highly porous activated carbon is used in the removal of volatile organic compounds (VOCs) and the purification of room air. Since the activated carbon must be capable of removing VOCs at low concentrations through adsorption, studies on the adsorption equilibrium of trace-level concentrations of VOCs are essential. To determine the adsorption isotherm, a headspace gas chromatography (HSGC) method was used, with analysis carried out using gas chromatography or gas chromatography-mass spectroscopy. The reliability of this method was confirmed by comparison of the adsorption isotherms of methanol measured by the HSGC method with those measured by the volumetric method. Isotherms for three different types of activated carbon and eight types of VOCs were determined over a wide range of concentrations. Furthermore, the results of the HSGC method for two systems of binary adsorption equilibria $(\text{dichloromethane}+\text{trichloroethylene})$ and $(\text{benzene}+\text{toluene})$ , were found to be correlated with those of the ideal adsorbed solution theory.

An immobilized cell hollow fiber membrane bioreactor was operated continuously for the cometabolic transformation of 4-cp in the presence of phenol. In contrast to the batch operation of the bioreactor in which the immobilized cells were exposed to decreasing substrate concentrations, at high substrate concentrations, under continuous operation, dissolved oxygen was found to be a limiting nutrient. It was found that substrate degradation was enhanced by aerating the feed with pure oxygen. It was also found that the optimum number of hollow fibers in the bioreactor was 25, ca. 30% bioreactor volume. This occurred due to a balance of the pore space available for cell immobilization in the fibers against the extracapillary space available for suspension cell growth. During continuous operation, regardless of feed rate $(21–60\mathrm{mL}\bullet {\mathrm{h}}^{-1})$ , the maximum substrate loading was found to be $9\mathrm{mg}\bullet {\mathrm{h}}^{-1}$ each of phenol and 4-cp in order that both substrates were completely transformed. In anticipation of reduced provision of phenol as a specific growth substrate for 4-cp cometabolic transformation, it was concluded that complete transformation of 4-cp could be effected through a minimum substrate concentration ratio of phenol:4-cp of 1:1.8.

Treatment technologies were evaluated for application in water reuse for the textile industry. Technologies tested included electrochemical oxidation, hypochlorite oxidation, ozonation, granular activated carbon (GAC) adsorption, bisulfite catalyzed sodium borohydride reduction, Fenton’s reagent, coagulation, and anaerobic biodegradation. Bench-scale side-by-side tests were conducted using a spent dyebath wastewater from a jigg dyeing operation. The dyebath contained three reactive dyes and auxiliary chemicals (e.g., common salt, soda ash, acetic acid, and caustic). Each technology was evaluated for its effectiveness at removing color and chemical oxygen demand (COD) and anticipated operating costs. Ozone, GAC, and electrochemical oxidation produced high-quality effluent, suitable for reuse. Although hypochlorite oxidation and sodium borohydride reduction resulted in significant color removal, it was not sufficient to meet reuse criteria. Results were either insignificant or inconclusive for coagulation, Fenton’s reagent, and anaerobic biodegradation. Auxiliary chemicals had great impact on the performance of many of the alternatives evaluated.

Ozone and electrochemical oxidation treatment technologies were evaluated for wastewater recycling in the textile industry. Textile wastewater was collected from eight textile mills that use different dying processes. Both ozone and electrochemical oxidation removed the color from wastewater containing acid, reactive, and natural dyes, while mixed results were achieved with pigment and disperse dyes. The variability in color removal for the pigment and disperse dyes may be related to the concentration and type of auxiliary chemicals used. Color criteria for reusing wastewater for reactive dye was determined to be $\Delta E⩽2$ . This level of treatment provided an acceptable level of residual color for reuse in dark color dyeing operations and for rinse water. Some reformulation of the dye concentration and auxiliary chemicals is necessary for wastewater reuse in light color dyeing operations. Also, multiple reuse of the treated wastewater, as would occur in a completely closed system, would require changes in salt and other auxiliary chemicals to achieve the same fabric color as clean process water.

Human urine contributes 80% of the total nitrogen and 40–50% of the total phosphate load to municipal wastewater. This study examines the impact of separate urine collection and treatment on wastewater treatment. An integrated wastewater and urine treatment process was defined, in which single high-rate ammonium removal over nitrite and anaerobic ammonium oxidation processes and struvite recovery are at the heart of the nutrient management. The model study demonstrated that if 50% or more of urine were collected and treated separately, integrated wastewater treatment with more compact and energy-efficient processes would be possible. The integrated wastewater and urine treatment is compared to an existing state-of-the-art treatment process. The main advantage of urine separation is not only a better effluent quality. Existing processes including tertiary treatment can already produce very good effluent quality with total effluent nitrogen and phosphate concentrations of 2.5 and $0.5\mathrm{g}∕{\mathrm{m}}^3$ , respectively. The main advantage of urine separation is the production of this same good effluent quality with a remarkable saving in resources. With sufficient urine separation, generation of net primary energy is possible.

This paper presents a process for the removal of inorganic mercury from aqueous solutions using alumina nanoparticles, which were prepared by the sol-gel method. Different amounts of mercury were added to the particles until a critical concentration was achieved, thus inducing the alumina sol flocculation. Particle growth was monitored during the process using dynamic light scattering. The amount of metal ion adsorbed on the surface of the alumina sols was determined by atomic absorption spectroscopy. Initial mercury concentrations ranging between 50 and 100 ppm decreased to below 1 ppb in a short time.

This work considers the mechanisms of mass transfer in a process of dispersed sorbent injection. During experiments, an air supply was dosed with toluene vapor, at partial pressures between 4 and 15 Pa. Powdered activated carbon (PAC) was added to remove the toluene from the air, and the resulting mixture was passed through a 3-m-long, tubular, aluminum test section. Toluene concentrations were measured at seven axial locations within the test section. Comparing the measurements with mathematical models indicated the importance of adsorption kinetics. At reduced toluene inlet concentrations the PAC removed a slightly bigger fraction of toluene from the air stream. This fraction increased with PAC concentration. The effect on removal of varying the air temperature between 25 and 85°C was small. Alternative models incorporating either pore diffusion or surface diffusion were fitted to the results. The quality of the fits was fair only, but sufficient to show that the pore diffusivity that gave the best fit was far larger than would be expected from the Knudsen diffusivity in the pores. That is, surface diffusion was an important part of the intraparticle mass transfer.

Hexavalent chromium (Cr(VI)) contamination of soil and groundwater is a major environmental concern for some industrial sites and most of the U.S. Department of Energy sites. Cr(VI) is toxic and fairly mobile in groundwater. Bioreduction of Cr(VI) to less toxic and less mobile Cr(III) is considered to be a feasible option. Among the Cr(VI) reducing bacteria, Shewanella oneidensis MR-1 (MR-1) has been shown to be effective in metal reduction under anaerobic conditions. Data on bioreduction of Cr(VI) by MR-1 in a flow-through soil column that better approximates the subsurface condition are not available. The objective of this research project was to study the bioreduction of Cr(VI) by MR-1 in a continuous-flow quartz sand column system. MR-1 was found to be very effective in reducing Cr(VI) to Cr(III) for concentrations ranging from 0.055 mM $(2.85\mathrm{mg}∕\mathrm{L})$ to 0.006 mM $(0.31\mathrm{mg}∕\mathrm{L})$ . The amount of Cr(VI) reduced prior to its breakthrough was found to be inversely proportional to its concentration in the feed due to increased inhibition of microbial activity and a residual reduction of 20–45% of Cr(VI) was observed even after its breakthrough.

Oxidative treatment of H-acid (HA) and Reactive Black 5 (RB5) using Fenton reagent $({\mathrm{Fe}}^{2+}∕{\mathrm{H}}_2{\mathrm{O}}_2)$ and the electro-Fenton (EF) method is reported. Optimization of doses of ferrous iron and hydrogen peroxide was carried out in each case using HA; and the oxidation of RB5 was also carried out under the optimized conditions. Approximately 71% chemical oxygen demand (COD) was removed in 2 h using the conventional Fenton method at optimized doses: ${\mathrm{Fe}}^{2+}=0.3\mathrm{g}∕\mathrm{L}$ (5.37 mM), ${\mathrm{H}}_2{\mathrm{O}}_2=6\mathrm{mL}∕\mathrm{L}$ (53.0 mM), ${\mathrm{H}}_2{\mathrm{O}}_2∕{\mathrm{Fe}}^{2+}=10$ . In contrast, more than 92% COD was removed in 15 min using the EF method with an optimized ${\mathrm{Fe}}^{2+}$ dose of $0.130\mathrm{g}∕\mathrm{L}$ (2.34 mM) and $8\mathrm{ml}∕\mathrm{L}$ (70.6 mM) of ${\mathrm{H}}_2{\mathrm{O}}_2$ . The pseudo-first-order rate constants $\left(k\right)$ for the Fenton reagent and EF method were 0.054 and $0.38{\min }^{-1}$ . The COD removal through the EF method was seven times faster. The calculated energy requirement of the EF method was $0.82\mathrm{kg}\mathrm{COD}∕\mathrm{kW}\bullet \mathrm{h}$ at the minimum applied current (0.25 A) when approximately 92.5% COD was removed. In the case of RB5, about 67 and 87% COD was removed under optimized Fenton and electro-Fenton conditions, respectively. The higher efficiency of the EF method was attributed to incremental addition of ${\mathrm{Fe}}^{2+}$ and accompanying higher ${\mathrm{H}}_2{\mathrm{O}}_2∕{\mathrm{Fe}}^{2+}$ molar ratio. The results are discussed in the light of the mechanism for Fenton’s oxidation.

Based on a set of Chesapeake Bay Estuarine Model (CBEM) scenarios, a three-dimensional response surface of a water quality index, such as chlorophyll concentration, versus a pair of loading constituents, e.g., nitrogen and phosphorus, is constructed. The responses of water quality, such as dissolved oxygen, chlorophyll, and water clarity, to nitrogen, phosphorus, and sediment loads are analyzed. From the response surface, a water quality response is estimated under loading conditions beyond that of a limited set of scenarios. Response surfaces may be used to determine the possible universe of nutrient and sediment load reductions needed to obtain a particular water quality standard and to examine the tradeoffs among nutrient and sediment load reductions that achieve the same water quality objective.

Assessing the bioavailability of a group of polycyclic aromatic hydrocarbons (PAHs) coexisting in a field-aged contaminated sediment was examined using mild extractions by isopropanol- and ethanol-water solutions at concentrations of 5–100%, using extraction durations from $1\mathrm{h}\text{to}7\text{days}$ . At a given solvent concentration, an initial rapid phase of PAH desorption was generally observed during the first $12\mathrm{h}$ , followed by a subsequent slower phase of desorption. A similar biphasic desorption was evident with increases in solvent concentration. PAH removal by various mild extractions was compared with PAH biodegradation by indigenous microorganisms. The removal of individual PAHs using $1\text{-}\text{day}$ 70% ethanol extraction was closely correlated to corresponding PAH removal via biodegradation, suggesting the possibility of using alcohol-water solution to simultaneously predict the bioavailability of multiple PAHs in aged sediments to indigenous microorganisms.

Commons are public lands that are often used for recreational activities and are generally assumed to be free of soil contamination. However, in old industrial cities, urban commons may have accumulated heavy metal burdens from airborne contamination. This paper examines the heavy metal burdens and risk analysis results for 50 commons in the greater Cleveland, Ohio area. The U.S. Environmental Protection Agency Method 3050B and 1N HCl soil extraction results are presented for Cd, Cr, Cu, Ni, Pb, and Zn mass burdens, and are interpreted relative to Ohio residential soil guidance and “typical” values from the remediation guidance of 30 states. Results demonstrate that most of these soils have heavy metal burdens that are well above naturally occurring levels, and several (at least 8 of the 50 sites tested) have heavy metal burdens that exceed Ohio’s residential soil contamination guidance. Lead and cadmium were found to be the most significant contributors to site hazard index values.

A cluster of 50 stone crushing units located at Pammal, in suburban Chennai, the capital of Tamil Nadu State, India, is a source of high levels of dust generation in the vicinity of the crushers and in the communities surrounding them. Ambient air quality network consisting of 26 sampling locations were operated to continuously monitor the total and respirable particulate matter concentrations (TSP and ${\mathrm{PM}}_{10}$ ). The daily average ambient concentrations of TSP and ${\mathrm{PM}}_{10}$ varied from 342 to 2,470 and 90 to $\mathrm{1,200}\mu \mathrm{g}∕{\mathrm{m}}^3$ , respectively, near the source, while the average concentrations varied from 86 to 257 and 39 to $138\mu \mathrm{g}∕{\mathrm{m}}^3$ in ambient air. The average ${\mathrm{PM}}_{2.5}$ concentration varied from 41 to $388\mu \mathrm{g}∕{\mathrm{m}}^3$ at the source, whereas the concentration varied from 17 to $48\mu \mathrm{g}∕{\mathrm{m}}^3$ in ambient air. Personal samplers were also employed to quantify the TSP and RPM in the work environment and they varied from 22.5 to 80.5 and 13.5 to $53.7\mathrm{mg}∕{\mathrm{m}}^3$ , respectively. Both ambient concentrations and occupational exposure levels exceeded the Indian National Standards at most of the locations. Pulmonary function tests performed on workers showed that the average values of pulmonary function in these workers are significantly lower than the average values reported for normal South Indian healthy males.

An event mean concentration (EMC), usually collected with an automatic, flow-weighted composite sampler, is often used to characterize stormwater pollutants. Automatic samplers are not recommended for collecting oil and grease (O&G) samples due to possible biases associated with interactions with tubing and pumps. To measure the EMC without sampler interferences, a series of grab samples (often over ten samples) must be collected along with the flow measurement to compute the EMC. This paper examines 22 O&G pollutographs from small, impervious highway sites, to determine when a single O&G grab sample most closely approximates a flow-weighted composite sample. Samples collected within the first hour of a storm event overestimated the O&G EMC by $20\mathrm{mg}∕\mathrm{L}$ or more, while samples collected toward the end of the event underestimated the EMC. The best time to collect a single grab sample ranged from 1 to 6 h after the beginning of runoff, and was related to site or storm-specific factors. Results obtained from this study also showed that strong correlations $(R^2=0.9)$ exist between O&G and other organic constituents, such as chemical oxygen demand (COD) and dissolved organic carbon (DOC). Correlations also exist between O&G EMC, antecedent dry days, and total rainfall. Depending upon site and regulatory specific factors, using COD or DOC EMCs in lieu O&G samples may be a better strategy.

A single-stage phosphorylated polyvinyl alcohol immobilized-cell reactor with three operation modes was employed to investigate the efficiency of simultaneous carbon/nitrogen removal from raw swine wastewater. In continuous aeration mode, the removal efficiency of chemical oxygen demand (COD) and total nitrogen (T-N) exceeded 70 and 8%, respectively, at hydraulic retention time of $10\text{days}$ . In intermittent aeration (IA) mode, the removal efficiency of COD and T-N was more than 85 and 46%, respectively, when the reactor was set at 50% aeration duration to cycle time to operate at three aerobic-anoxic cycles per day. When oxidation-reduction-potential control was adopted to control the duration of the anoxic period in the real-time controlled (RTC) IA mode for a $4\mathrm{h}$ aeration period, the total cycle time was reduced by about 20% with a slight increase in removal efficiency of COD (87%) and T-N (47%). The system with no extra chambers required is efficient in simultaneous carbon/nitrogen removal.