Journal of Environmental Engineering

To systematically understand the effects of the culturing properties and biodegradation reactions on 4-nitrophenol (PNP)-degrading microorganisms, the bacterium YUP-3 was isolated from soil samples with no PNP-pollution history using a novel method. This bacterium was domesticated to utilize PNP as the sole source of carbon and nitrogen in mineral salt medium. Response surface methodology (RSM) was used to select the most important variables from the simultaneous study on PNP degradation after 48 h incubation. The theoretical maximum PNP degradation of 100.0% was obtained under optimized conditions, and temperature and PNP initial concentrations were concluded to be significant variables. Under carbon- and nitrogen-deficient conditions, five metabolic products of PNP were identified through gas chromatography–mass spectrometry. Hydrogenation and deoxidation were analyzed as two main reactions through PNP degradation to produce hydroquinone. These results demonstrated the importance of the novel PNP degradation pathway under nutrition deficient conditions and the potential use of this highly effective PNP degrading bacterium.

Hydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as unit operations (UOs) for particulate matter (PM) separation, are common smaller-footprint best management practices (BMPs). Test protocols and physical model results for such UOs are often assumed to only be applicable by city, state, or region. Rainfall-runoff, climate, watershed, and PM granulometry are, in part, groups of parameters identified as impacting UO behavior. As a result, UO behavior is often assumed to be nonrepresentative when the UO is ported to different environs. This study examines specific parameters with potential to alter UO behavior: (1) hydrograph unsteadiness; (2) PM particle-size distribution (PSD); (3) PM specific gravity (${\rho }_{\mathrm{sg}}$); and (4) water temperature. In this study, UO behavior as PM separation efficiency (${ß}_{\mathrm{PM}}$) is normalized for each parameter to examine if UO results can be ported across a series of urban environs. To generate normalized ${ß}_{\mathrm{PM}}$ results, computation fluid dynamics (CFD) models of the HS and RC are applied for seven flow rates, three levels of ${\rho }_{\mathrm{sg}}$, and three temperatures over a heterodisperse PSD from 1 to 2,000 μm. CFD models were validated within 10% of physical model results for measured events. Additionally, these parameters were analyzed with normalized ${ß}_{\mathrm{PM}}$ results to model three hydrographs loading the HS and RC. Results indicate the greatest impact on UO behavior is influent PSD, whereas ${\rho }_{\mathrm{sg}}$ and hydrograph characteristics have significant but less pronounced impacts. Temperature has a minor impact. Results demonstrate the normalized ${ß}_{\mathrm{PM}}$ approach for a specific UO accounts for the variability of these common parameters examined, and thus UO behavior can be portable across geographic locations. Results further suggest the potential of a more unified physical model testing protocol for UO certification and the deployment of validated CFD models to support physical testing.

In this paper, an ultraviolet light emitting diode–based immobilized photocatalytic reactor was designed, fabricated, and tested for water treatment. The performance of the reactor was evaluated by testing phenoxy pesticides and chlorophenols, and it was optimized by studying the degradation of 2,4-dichlorophenoxyacetic acid. The effect of operational parameters including light intensity, distance between light emitting diode module and photocatalytic plate, recirculation flow rate, and external electron scavengers on the reactor’s performance were investigated. Furthermore, the performance of immobilized photocatalytic plate (anodized ${\mathrm{TiO}}_2$ nanotubes) was compared with slurry ${\mathrm{TiO}}_2$ and hollow glass microspheres coated with anatase ${\mathrm{TiO}}_2$. A power law relationship between the light intensity ($2.2–17.3\mathrm{mW}/{\mathrm{cm}}^2$) and first-order kinetics rate constants for 2,4-dichlorophenoxyacetic acid degradation was observed; a suitable circulation flow rate and the distance between light emitting diode module and photocatalytic plate was determined to achieve good degradation efficiency. Enhanced performance of the reactor was observed when ${\mathrm{H}}_2{\mathrm{O}}_2$ was introduced.

Treatment process selection for compost leachate is required to carry out a pilot study because of the variability and complexity of this liquid’s composition. The main objective of the present study is to evaluate the removal of coliforms and toxic metals from real compost liquids by a flat sheet membrane bioreactor. To meet this aim, after treatment of the compost leachate in a serially connected process (anaerobic mixed baffled reactor plus anaerobic sequencing batch reactor plus sequencing batch reactor), effluent with chemical oxygen demand $(\mathrm{COD})=654\mathrm{mg}/\mathrm{L}$, biological oxygen demand $({\mathrm{BOD}}_5)=54\mathrm{mg}/\mathrm{L}$, and total suspended solids $(\mathrm{TSS})=84.5\mathrm{mg}/\mathrm{L}$ was fed to a membrane sequencing batch reactor (MSBR) that was conducted at the laboratory scale. The membrane was used to enhance the quality of the biological reactor effluent by decreasing the number of total coliform (TC) and fecal coliform (FC) bacteria to below 12 and 5 per 100 mL, respectively. Moreover, increasing pH to 9 resulted in a decrease in heavy metal concentrations. The mean values of toxic metals in the membrane filtrate were $\mathrm{Cr}=0.001–0.03$, $\mathrm{Zn}=0.004–0.08$, $\mathrm{Ni}=0.005–0.055$, $\mathrm{Cd}=0.001–0.02$, and $\mathrm{Pb}=001–0.02\mathrm{mg}/\mathrm{L}$. In this study, the biological and chemical parameters measured in the stabilized leachate fell significantly below national standard limits for discharge into the environment. Health risk assessment is needed to evaluate the treated permeates’ capability for beneficial reuse.

The production of dyes is a major source of industrial wastewater, so it is important to develop efficient ways of treating this water. In this paper, the authors describe the use of a continuous aluminum-carbon microelectrolysis process (CACMP) to treat the wastewater, and the authors describe the optimum condition for this procedure. A novel technique for preparing the aluminum-carbon microelectrolysis material (ACMM) was optimized by Box-Behnken design, and the performance of the ACMM was estimated by measuring the changes in the chemical oxygen demand (COD) and determining the efficiencies for the removal of ammonia nitrogen (${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$) and color for an alkaline dye wastewater with a pH of 12.0. The optimum conditions for the ACMM were a mass ratio of aluminum to carbon of 1.26, a sintering time of 88.5 min, a sintering temperature of 500°C and a ${\mathrm{TiO}}_2$ mass percentage of 4.78%. The conditions for the CACMP were an initial pH of 12, a hydraulic retention time of 9 h, and a dissolved oxygen concentration of $3–5\mathrm{mg}/\mathrm{L}$. During the stable operation period of the CACMP, the COD improved by more than 50%, more than 50% of the ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ was removed, color removal efficiency was higher than 68%, and the biodegradability of the wastewater significantly improved.

This study aims to investigate the effect of dielectrophoretic (DEP) force on microorganisms’ viability in a membrane bioreactor (MBR). The impact of different electrical potentials (5–150 V) and different exposure durations (20–120 min) on the viability of microorganisms were studied. An interdigitated cylindrical electrode (IDE) configuration was used in the membrane module. Each electrical potential application was operated intermittently with 10 s of the electric field on and 15 s of the electric field off. It was found that the bacteria were able to withstand voltage up to 50 V, and their activity even increased with time with the application of 5 V. At high electrical potentials (100 and 150 V), the microbial activity decreased as a result of the increased current flow and temperature build up due to the Joule heating effect. The decrease of the microbial activity caused the increase of the total organic carbon (TOC) and ammonium (${\mathrm{NH}}_4^{+}$) concentrations in the bulk solution. A comparison between the continuous and intermittent voltage supply for the 50 V further proved the Joule heating impact on the bacteria viability.

Chlortetracycline (CTC) is one of the widely used antibiotics in animal farms commonly found in wastewater and surface water and therefore development of new treatment technologies is necessary to avoid adverse effects on humans and the environment. White-rot fungi laccase is an attractive candidate for safe treatment of water and wastewater contaminated with micropollutants. In this work, Trametes versicolor laccase was produced and response surface methodology with a central composite design was employed to investigate the effects of different parameters including pH, temperature, mediator concentration, and enzyme concentration on biodegradation of CTC in the aqueous phase. A quadratic model was fitted to express the effects of each parameter including quadratic, linear, and interaction terms. The values for $R^2$ and adjusted $R^2$ were 0.85 and 0.70, respectively, indicating a reasonably good model for practical applications. Among the examined parameters, linear terms of temperature and pH had the largest effects. It was observed that the maximum degradation efficiency of approximately 95% can be achieved at pH, temperature, enzyme concentration, and mediator concentration of 5.2, 35.5°C, $62.3\mathrm{units}/\mathrm{L}$, and 10.9 μM, respectively. Also, three structures were proposed for the by-products of CTC biodegradation using mass spectroscopy data, and the yeast estrogen screen test showed that these by-products are not toxic.

Hazardous organic compounds can permeate gas pipelines and geomembranes made of organic polymer materials in landfills and leak into the surrounding environment, contaminating groundwater. The permeation of organic compounds in various organic polymer materials is explained by the molecular partition and the diffusion of organic compounds into polymer materials. The partition coefficient has two contributions resulting from size-based exclusion and molecular interaction. In this study, the authors use ab initio quantum mechanical calculations to investigate the molecular interaction between organic polymers and various organic compounds and seek the correlation with experimentally obtained partition coefficients reported in the literature. The authors examine 24 organic compounds and 4 polymer materials, including high-density polyethylene (HDPE) and polyvinyl chloride (PVC) geomembranes and casting, polybutylene (PB) pipes, and styrene-butadiene rubber (SBR) gaskets. The authors find a linear correlation between the theoretically calculated aqueous-phase free energies of interaction and experimentally obtained partition coefficients reported in the literature for HDPE, PB, and SBR. The study highlights the usefulness of free energy of interaction to predict the partition coefficients of organic compounds and provides mechanistic insight into the interaction between organic compounds and polymer materials.

Recycling of waste printed circuit boards (WPCBs) is an important subject not only for the protection of the environment, but also for the recovery of valuable materials, especially copper. In this paper, an effective and benign process for copper recovery from WPCBs is presented. In the process, copper in the WPCBs was treated through suspension electrolysis to gain copper powder. The effects of process parameters of ${\mathrm{H}}_2{\mathrm{SO}}_4$ and ${\mathrm{CuSO}}_4$ concentrations and the current density were studied. Experimental results showed that the suspension electrolysis process is an effective method to recover copper from WPCBs. The X-ray diffraction (XRD) and electronic differential system (EDS) spectra indicated no other impurities in the recycled copper. The copper recovery conditions were optimized using a Box-Behnken design of response surface methodology. The optimum conditions were observed when the solution contained $30\mathrm{g}/\mathrm{L}{\mathrm{CuSO}}_4$, $110\mathrm{g}/\mathrm{L}{\mathrm{H}}_2{\mathrm{SO}}_4$, and current density of $3\mathrm{A}/{\mathrm{dm}}^2$, resulting in a recovery efficiency of 86.46%. The results indicate the process as a promising method to recover copper from WPCBs.