Journal of Environmental Engineering

Human dose-response data from seven pathogens commonly associated with waterborne illness were used in conjunction with acceptable levels of risk specified by the United States EPA to determine an allowable particle limit for reclaimed water assuming varying degrees of pathogen association. Assuming particles contain a single pathogen, particle limits ranged from 213,000 particles/L for E. coli ETEC to 400 particles/billion L for rotavirus. Particle concentrations in the effluent from nine reclamation facilities that employed advanced filtration exceeded calculated allowable particle limits for one or more pathogens despite achieving permitted water quality standards. Hence, current methods of estimating particle densities (e.g., turbidity and suspended solids) and indicator organisms are potentially incongruent with acceptable levels of risk specified by the United States EPA. The significance of this incongruence is dependent on the uncertain frequency of pathogen association with wastewater particles.

Semivolatile hydrophobic organic contaminants (SV-HOCs) in sediments are a growing problem. Previous research in our laboratory has demonstrated that cleanup of the entire sediment may not be necessary due to sequestration of the majority of SV-HOCs like polycyclic aromatic hydrocarbons (PAHs) into the low density fraction that we hypothesize is separable from the bulk sediment hydraulically. In our current study, PAH-contaminated sediments from the Indiana Harbor Canal were hydraulically dredged and impounded in a stilling basin by the U.S. Army Corp of Engineers to evaluate a hydraulic dredge and characterize water treatment needs. This project provided an opportunity to test our hypothesis that a segregation of SV-HOC contaminated sediments would occur via hydraulic settling processes in the stilling basin at field scale. Following decommission of the basin, sediment cores were collected along transects from the basin influent immediately after removal of the overlying water, sectioned and characterized for physical and chemical parameters. As hypothesized, sediments showed large decreases in bulk density with increasing distance from the basin inlet. PAH concentrations increased up to 40-fold $(120–\mathrm{4,900}\mathrm{mg}{\mathrm{kg}}^{-1})$ and were highly correlated with the fraction of low density material in the sediment. Our results provide evidence that hydraulic dredging can result in a separation of highly contaminated sediment with high amounts of low density material from bulk sediment. This outcome may be either fortuitous or detrimental depending on the ultimate means of disposal. If subsequent dewatering occurs (such as in a confined disposal facility), prediction of PAH volatilization flux needs to be based on the in situ surface concentration which can be very high due to slow settling low density particles. Conversely, if the goal is beneficial reuse, higher density sediment with relatively low PAH levels near the inlet may be readily collected.

This study focuses on the effect of aquatic plants on the changes of enzyme activities in wetland sediments. Wetland plants play essential roles both as a carbon supplier for microbes which synthesize enzymes and as a regulator for enzyme activity by modifying hydrochemistry in the rhizosphere. Although numerous studies have been carried out on soil enzymes, little information is available on the vertical distribution and temporal variation of enzyme activities affected by the presence of plants in wetlands. Our results clearly show that sediments with wetland plants exhibit significantly higher enzyme activities of $\beta$ -glucosidase, arylsulfatase, phosphatase, and N-acetylglucosaminidase $(P<0.05)$ up to a depth of $15\mathrm{cm}$ throughout the year, whereas only lower values were observed even at the surface of sediments $(0–3\mathrm{cm})$ without plants. However, in the field, there were no statistically significant changes of enzyme activities associated with the changes of season and the vertical position along the depth $(P<0.05)$ . This indicates that the organic carbon supplemented by root exudates, root debris, and plant residue played an important role in increasing enzyme activities in the sediments with plants. The mechanisms driven by aquatic plants such as oxygen diffusion and transpiration-induced advection did not induce the short-term changes in enzyme activities. Exceptionally, the changes of sulfate availability and the increase of temperature have implications in the changes of arylsulfatase activities depending on the location (vegetated versus nonvegetated sediment) $(P=0.000)$ , season (growing season versus senescence) $(P=0.042)$ , and sediment depth $(P=0.002)$ . Since wetlands treat wastewaters with variable carbon sources, it would be beneficial to maintain increased enzyme activities in the regeneration of inorganic nutrients from organic materials. In addition, the presence of plants would vertically extend the area where the higher enzyme activities are observed and the movement of wastewater takes place and, consequently, could accelerate wetland treatment efficiency.

Experiments were performed to evaluate changes in suspended particle-size distribution as a function of variations in mixing conditions. Suspensions were taken from Lake Erie near Buffalo, N.Y., and mixed in a standard jar apparatus using six different mixing intensities. These suspensions were monitored for changes in particle size and shape using a noninvasive image analysis technique. A relationship was derived between suspended particle size and mixing intensity, based on estimates of energy dissipation rates. The regression was also compared with mixing of suspensions taken from two other systems in the Buffalo, N.Y. area, a small lake on the University at Buffalo campus, and the Buffalo River (Buffalo, N.Y.). Samples from all three sites behaved similarly in terms of particle size as a function of mixing conditions. Estimates for dissipation rates in natural systems were then used to relate the laboratory data to field conditions. Dissipation rates produced at slow mixing speeds in the jar were similar to those calculated for more energetic riverine and estuarine environments. Results of this study should be useful for understanding suspended particle-size distributions under a variety of mixing conditions, and is of direct interest in a wide range of sediment and contaminant transport problems.

Thus far, zero-valent iron has been studied mostly for the degradation of structurally simple one- and two-carbon halogenated organic contaminants such as chlorinated methanes, ethanes, and ethenes. In this research, laboratory synthesized particles of nanoscale iron were explored to degrade lindane, also known as $\gamma$ -hexachlorocyclohexane, a formerly widely utilized pesticide and well-documented persistent organic pollutant. In general, lindane disappeared from aqueous solution within $24\mathrm{h}$ in the presence of nanoiron concentrations ranging from $0.015\text{to}0.39\mathrm{g}∕\mathrm{L}$ . By comparison, approximately 40% of the initial lindane dose remained in solution after $24\mathrm{h}$ in the presence of $0.53\mathrm{g}∕\mathrm{L}$ of larger microscale iron particles. However, the surface area normalized first-order rate constants were all within the same order of magnitude regardless of dose or iron type. A key reaction intermediate, $\gamma$ -3,4,5,6-tetrachlorocyclohexene from dihaloelimination of lindane was identified and quantified. Trace levels of additional degradation products including benzene and biphenyl were detected but only in the high concentration experiments conducted in 50% ethanol. While up to 80% of the chlorine from the lindane molecules ended as chloride in water, only 38% of the expected chloride concentration was observed for the microscale iron experiment. This work together with previous published studies on the degradation of polychlorinated biphenyl, chlorinated benzenes, and phenols suggest that zero-valent iron nanoparticles can be effective in the treatment of more structurally complex and environmentally persistent organic pollutants such as lindane.

Textile wastewater containing a high level of color and refractory chemical oxidation demand (COD) is difficult to treat using traditional wastewater treatment processes. Typically, a chemical process was suggested as a pretreatment to remove color and increase biodegradability of refractory organic materials. A biological process was then used to remove organic materials and reduce chemical costs for textile wastewater treatment. Fenton oxidation is one of the most effective chemical processes for removing color and COD for textile wastewater. In Fenton processes, oxidations by generated hydroxyl radical are the key factor for color removal in textile wastewaters; thus, monitoring oxidation reduction potential (ORP) should have high potential in Fenton dosage control for color removal in textile wastewater treatment. The main object of this study is to build a Fenton dosage control strategy that uses ORP monitoring and artificial neural network (ANN) models for removing color from textile wastewaters. Two wastewaters, synthetic and real textile, were used in this study. Experimental results have shown that the ANN models precisely represent the correlation between monitoring ORP, Fenton doses, color removal efficiency, and effluent color value, and therefore can be used to control Fenton doses for removing color from textile wastewater. Finally, another series of Fenton dose-control experiments for different color removal control targets were conducted to evaluate this proposed Fenton dose control strategy. Experimental results indicate that the proposed control strategy precisely controls the required Fenton doses for different control targets for both synthetic and real textile wastewaters, and result in reduced chemical costs.

The present research deals with the production of activated carbon by chemical activation using peach stones and its adsorption behavior. The prepared activated carbon was used for the adsorption of three kinds of textile dyes, acid, reactive, and direct dyes, from aqueous solution. The results indicated that the overall adsorption process followed the pseudo-second-order kinetic model. The equilibrium data were found to be well represented by the Langmuir adsorption isotherm model. The calculated adsorption capacities for Reactive Orange 16, Acid Yellow 11, and Direct Red 23 onto activated carbon were 667, 539, and $427\mathrm{mg}{\mathrm{g}}^{-1}$ at $50°\mathrm{C}$ , respectively. Thermodynamic parameters, such as $\Delta G°$ , $\Delta H°$ , and $\Delta S°$ , were also calculated and indicated that the adsorption of dyes onto activated carbon was spontaneous and endothermic in nature.

This paper describes the preparation of new adsorbents derived from sugarcane bagasse and wood sawdust (Manilkara sp.) to remove zinc (II) ions from electroplating wastewater. The first part deals with the chemical modification of sugarcane bagasse and wood sawdust, using succinic anhydride to introduce carboxylic acid functions into the material. The obtained materials (modified sugarcane bagasse MB2 and modified wood sawdust MS2) were then characterized by infrared spectroscopy (IR) and used in adsorption experiments. The adsorption experiments evaluates ${\mathrm{Zn}}^{2+}$ removal from aqueous single metal solution and real electroplating wastewater on both batch and continuous experiments using fixed-bed columns prepared in laboratorial scale with the obtained adsorbents. Adsorption isotherms were then developed using Langmuir model and the Thomas kinetic model. The calculated ${\mathrm{Zn}}^{2+}$ adsorption capacities were found to be $145\mathrm{mg}∕\mathrm{g}$ for MS2 and $125\mathrm{mg}∕\mathrm{g}$ for MB2 in single metal aqueous solution, whereas for the industrial wastewater these values were $61\mathrm{mg}∕\mathrm{g}$ for MS2 and $55\mathrm{mg}∕\mathrm{g}$ for MB2.

The efficiency of two similar gas-lift bioreactors, a biofilm reactor and a hybrid circulating floating bed reactor (CFBR), were studied and compared. In the biofilm CFBR the biomass grew preferably adhered on a plastic granular support, whereas in the hybrid CFBR both suspended biomass and biofilms were allowed to grow in the reactor. $\mathrm{COD}∕\mathrm{N}{\mathrm{H}}_4^{+}$ ratio (COD=chemical oxygen demand) was manipulated between 0.0 and $8.0\mathrm{g}∕\mathrm{g}$ , maintaining the ammonia influent concentration around $50\mathrm{mg}$ $\mathrm{N}–\mathrm{N}{\mathrm{H}}_4^{+}∕\mathrm{L}$ , the ammonia loading rate at $0.9\mathrm{kg}$ $\mathrm{N}–\mathrm{N}{\mathrm{H}}_4^{+}∕{\mathrm{m}}^3\text{day}$ and the hydraulic retention time at $1.36\mathrm{h}$ . At low $\mathrm{COD}∕\mathrm{N}{\mathrm{H}}_4^{+}$ ratio (0 and $0.5\mathrm{g}∕\mathrm{g}$ ) both systems behaved similarly, achieving ammonia removal percentages higher than 95%. In the biofilm CFBR a reduction of the nitrification percentage from 95 to 20% was observed when a $\mathrm{COD}∕\mathrm{N}–\mathrm{N}{\mathrm{H}}_4^{+}$ ratio up to $8\mathrm{g}∕\mathrm{g}$ was applied in the influent. However, at the same operational conditions, the nitrification process in the hybrid CFBR was slightly affected. In the hybrid-CFBR reactor heterotrophs growing in suspension consumed the COD source faster than those growing in biofilms as was monitored. The growth of heterotrophic microorganism in suspension had a beneficial effect for the nitrifying population growing in the biofilm of the hybrid CFBR. Nitrifying activity of the biofilm was not limited by the presence of heterotrophs consuming dissolved oxygen, displacing the nitrifying bacteria or creating mass transfer resistance as was observed in the biofilm CFBR.

The present work provides a description and an assessment of the conversion of an odor-treating industrial chemical scrubber into a biotrickling filter and of its startup and operation during $5\text{months}$ at an empty bed residence time of about $0.9\mathrm{s}$ . The system treats a gas flow rate of around $\mathrm{50,000}{\mathrm{m}}^3∕\mathrm{h}$ , with average concentrations of volatile organic compounds, $\mathrm{N}{\mathrm{H}}_3$ and ${\mathrm{H}}_2\mathrm{S}$ , of around 10, 2, and $<1$ ppmv, respectively. The main actions undertaken during the conversion were the substitution of the recirculation pump and of the packing material and the modification of the makeup water and purge flow controls. Afterwards, the reactor was inoculated with sludge obtained from a waste water treatment facility, and immediately started up as a biotrickling filter. No significant operation issues were observed during the operation period, other than pH variations and a slight increase in pressure drop, proving that the biotrickling filter is a highly robust system. Relatively low removal efficiencies around 10 and 25% were found, for the volatile organic compounds and $\mathrm{N}{\mathrm{H}}_3$ , respectively. However, due to the low empty bed residence time, these corresponded to notable elimination capacities of around $18\mathrm{g}\mathrm{C}∕{\mathrm{m}}^3\mathrm{h}$ and $3\mathrm{g}\mathrm{N}∕{\mathrm{m}}^3\mathrm{h}$ . No nutrients were supplied to the bioreactor during the first $5\text{months}$ of operation other than those contained in the sludge employed as inoculum.

Storm-water runoff entering filters is usually aerobic and therefore the removal processes in the filter normally occur under oxidizing and aerobic conditions. However, storm-water filters differ from water and wastewater treatment filters because there are quiescent times when no influent enters the filter and the pore water stagnates. During this stagnation period, anaerobic conditions on a macro- or microscale could develop. This note presents the results of experiments conducted to determine if four potential filter media (sand, activated carbon, peat moss, and compost) could retain previously trapped pollutants when anaerobic conditions develop during interevent periods. The results indicated that permanent retention of heavy metals may occur even in an anaerobic environment (for the media and metals investigated). However, retention of some nutrients may not occur under these conditions, particularly for the organic media. This is an area of concern when the design of filters and bioretention devices includes an internal water storage zone where, between events, anaerobic conditions for nitrate removal are encouraged.

The decay of fecal bacteria in surface water often follows a biphasic pattern with the apparent first-order rate constant relatively high during a first phase and lower in a second one. This could be the result of population heterogeneity in resistance due to various mechanisms (different strains, genetically or nongenetically differentiated cells, different growth or cell cycle stage, clumping, hardening), or the specific decay rate could be directly or indirectly affected by the cell density (e.g., quorum sensing). All these mechanisms can theoretically produce a biphasic decay pattern and are consistent with the literature. However, they are fundamentally different and lead to different behavior of mechanistic total maximum daily load models, so identifying the correct mechanism is important. This technical note presents the results of a study aimed at determining if a density effect is involved. Laboratory decay experiments with pure strain Escherichia coli cells in phosphate buffer were conducted over a range of initial densities. The results show that the rate constant changes after a certain time, rather than at a certain density, which is inconsistent with a density effect. As the experiments were performed with a pure strain, the resistant fraction cannot be attributed to a different strain. Further research is needed to identify the mechanism responsible for the population heterogeneity.