Journal of Environmental Engineering

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

Methods for detecting and monitoring known and emerging viral pathogens in the environment are imperative for understanding risk and establishing regulatory standards in environmental and public health sectors. Next-generation sequencing (NGS) has uncovered the diversity of entire microbial populations, enabled discovery of novel organisms, and allowed pathogen surveillance. Metagenomics, the sequencing and analysis of all genetic material in a sample, is a detection method that circumvents the need for cell culturing and prior understanding of microbial assemblies, which are necessary in traditional detection methods. Advancements in NGS technologies have led to subsequent advancements in data analysis methodologies and practices to increase specificity, and accuracy of metagenomic studies. This paper highlights applications of metagenomics in viral pathogen detection, discusses suggested best practices for detecting the diversity of viruses in environmental systems (specifically water environments), and addresses the limitations of virus detection using NGS methods. Information presented in this paper will assist researchers in selecting an appropriate metagenomics approach for obtaining a comprehensive view of viruses in water systems.

Reverse osmosis experiments with synthetic feed waters were carried out to simulate combined fouling of salt-rejecting membranes by colloids and ${\mathrm{CaSO}}_4$ scale. Two gypsum crystallization regimes were studied: (1) surface crystallization with the saturation index smaller than 1 in the bulk and higher than 1 near the membrane surface and (2) concomitant surface and bulk crystallization with supersaturated solutions. Rapid flux decline was observed for both undersaturated and supersaturated feeds. For the supersaturated feed, scaling resulted in a dramatic flux decline only marginally affected by ${\mathrm{SiO}}_2$ colloids. For the undersaturated feed, the flux decline was significantly higher than the summation of flux declines due to colloidal fouling alone and gypsum scaling alone. Colloidal silica did not have a statistically significant effect on the amount of gypsum crystals formed on membrane, whereas the deposition of colloids was enhanced in the presence of ${\mathrm{CaSO}}_4$ scale. The synergistic increase in fouling is attributed to changes in the structure of the fouling layer. The results point to the importance of removing colloidal species at the pretreatment stage.

Continuous adsorption of copper ions on a chitosan-based fibrous adsorbent was investigated in the adsorption bed. The experiment was carried out at various flow rates (11.8, 20.2, and $30.4{\mathrm{mL}\min }^{-1}$) and inlet concentrations (50, 100, and $200{\mathrm{mg}\mathrm{L}}^{-1}$). The breakthrough time decreased with increases in flow rate and initial copper ion concentration. A Thomas model and Yoon–Nelson model were applied to the experimental data. The maximum adsorption capacity from the Thomas model was found to be $11.16{\mathrm{mg}\mathrm{g}}^{-1}$. A one-dimensional water quality model was used to investigate the migration process of copper ions in a sudden pollution accident in a river. Chitosan-based fibrous adsorbent installed in the lower reaches could reduce the harmful effects of heavy metals on the river ecosystem.

High volumes of wastewater with considerable levels of organic and phenolic compounds and solid material are produced during pistachio processing. There is not a commonly adopted treatment technology for the wastes produced during pistachio processing. The objective of this study is to evaluate the anaerobic digestability and biogas production capacity of pistachio processing wastewater in upflow anaerobic sludge blanket (UASB) reactors for the first time in the literature. The results indicated that pistachio processing wastewater can be treated anaerobically with efficiencies comparable with other high-strength agricural wastewaters. The maximum chemical oxygen demand (COD) removal efficiency and methane yield values obtained were $89.77\%\pm 2.4\%$ and $332.5\pm 104.5\mathrm{mL}{\mathrm{CH}}_4\mathrm{g}{\mathrm{COD}}^{-1}$, respectively, at an organic loading rate (OLR) of $4.56\pm 0.87\mathrm{g}{\mathrm{L}}^{-1}{\mathrm{d}\mathrm{a}\mathrm{y}}^{-1}$. If the annual pistachio processing wastewater produced in Turkey per year ($520,000{\mathrm{m}}^3$) is digested anaerobically in a UASB reactor, 13,000 t of COD could be eliminated and 3.9 million cubic meters of methane (28,200 mWh of energy) can be produced.

Mechanisms causing greenhouse gas (GHG) emission in wastewater treatment plants are of great interest among researchers, encouraging the development of new methods for wastewater management. Wastewater treatment plants (WWTPs) emit three major greenhouse gases during the treatment processes: ${\mathrm{CO}}_2$, ${\mathrm{CH}}_4$, and ${\mathrm{N}}_2\mathrm{O}$. Additional amounts of ${\mathrm{CO}}_2$ and ${\mathrm{CH}}_4$ are produced during energy consumption, which can be considered an indirect source of GHGs. Recently, several efforts have been undertaken to assess GHGs from WWTPs, with particular attention paid to the ${\mathrm{N}}_2\mathrm{O}$ assessment due to its high warming potential (300 times stronger than ${\mathrm{CO}}_2$). This study proposes an integrated model platform for WWTP simulation, including the evaluation of both direct and indirect emissions as plant performance parameters. The results of extensive research demonstrate the importance of mathematical modeling for the development of a decision support system (DSS). The project involves four research units (RUs) united in effort to minimize the environmental impact of wastewater treatment plants in terms of both energy consumption and discharged pollutants (solids, liquids, and gases).

This paper examines the effectiveness of chemically enhanced treatment wetlands (CETWs), wetlands that received water treated with coagulants, to remove dissolved organic carbon (DOC), disinfection byproduct precursors (DBPPs), nutrients, and metals from agricultural drain water. Wetlands consisted of controls with no coagulant addition, ferric sulfate dosed, and polyaluminum chloride dosed treatments. CETWs were more effective in removing DOC, DBPPs, phosphate, dissolved organic nitrogen, and metals than control wetlands. Coagulation-treated wetlands removed $245–349\mathrm{g}/{\mathrm{m}}^2/\mathrm{year}$ DOC, whereas control wetlands produced $51\mathrm{g}/{\mathrm{m}}^2/\mathrm{year}$. Wetland passage released DOC in the controls and dosed treatments; this release was directly correlated to temperature, suggesting thermally dependent mechanism(s) were partly responsible. A first-order plug flow reactor kinetic model that considered hydraulic retention time (HRT), temperature, and DOC concentration was tested for wetland DOC processing. Models indicate that operating CETWs at high coagulant dosing and low temperature can result in the lowest DOC release. Operating at the lowest HRT to meet discharge targets helps overcome wetland processes that increase DOC release and provide the smallest footprint needed for treatment.

This study investigated the impact of altering the surface characteristics of support media used in attached-growth processes on the performance of biological wastewater treatment. The surface alteration was achieved through physical and chemical treatment of high-density polyethylene (HDPE), and changes in the HDPE surface characteristics, biofilm attachment, biofilm growth, and wastewater treatment performance were evaluated. Physical treatment procedures included roughening the HDPE coupons with sandpaper, and chemical treatment processes involved exposing the HDPE coupons to hydrogen peroxide and nitric acid. Changes in the physicochemical characteristics of the HDPE surfaces were determined using a variable pressure scanning electron microscope (VPSEM), a confocal profile meter, and contact angle (CA) measurements. The biofilm attachment, growth, and thickness were monitored using VPSEM images, biofilm volatile and total solids, protein quantities, and live/dead assay. The performance of biofilms in treating synthetic wastewater was determined by measuring the changes in chemical oxygen demand, ammonia, and total phosphorus concentrations. The results showed that physical treatment of the HDPE coupons increased the surface roughness and CA, changed the surface characteristics from hydrophilic to hydrophobic, improved the biofilm attachment and growth, increased the percentage of live cells, and enhanced the wastewater treatment performance. Chemical treatment of the HDPE coupons caused some minor changes to the surface and did not lead to significant improvements in biofilm growth or wastewater treatment.

Mono metallic (Mo, Ru, Rh, Cu, and Pd) and bimetallic (Rh-Cu and Rh-Ru) catalysts supported on stainless steel (SS) were prepared for perchlorate reduction. Results showed that perchlorate reduction followed a decreasing order: $\mathrm{Rh}/\mathrm{SS}>\mathrm{Cu}/\mathrm{SS}>\mathrm{Ru}/\mathrm{SS}>\mathrm{Mo}/\mathrm{SS}>\mathrm{Pd}/\mathrm{SS}>\mathrm{SS}$. Bimetallic catalyst SS-supported electrodes exhibited significant perchlorate reduction; perchlorate reduction over Rh-Cu/SS (78% reduction) was greater than that on Rh-Ru/SS (60% reduction). Chloride production was high at 95%. The imbalance in the chlorine mass could be attributed to the adsorption of perchlorate on the electrode and chlorine formation. Metal oxides and elemental metal dominated the catalyst surface based on X-ray photoelectron spectroscopy (XPS) analysis. X-ray diffraction (XRD) spectra showed the presence of both crystalline and amorphous metallic catalysts. The free energy of perchlorate adsorption on the Rh-Cu/SS was around $25\mathrm{kJ}/\mathrm{mol}$. The activation energy ($E_a$) of perchlorate reduction on the Rh-Cu/SS electrode was $19.5\pm 1.3$ and $110.9\pm 0.8\mathrm{kJ}/\mathrm{mol}$ in the temperature range of 303–343 K and 283–298 K, respectively. A proposed perchlorate reduction pathway was developed and successfully used to predict the reaction kinetics. No other oxyanions of chlorine, such as ${\mathrm{ClO}}_3^{-}$, ${\mathrm{ClO}}_2^{-}$, or ${\mathrm{ClO}}^{-}$, were detected as intermediates during perchlorate reduction.

To resolve the contradiction between livestock development and environmental pollution, anaerobic fermentation in biogas projects has been used for more missions, such as co-generation of heat and power, production of anaerobic digested fertilizer for the prevention and control of livestock pollution. The aim of this work was to investigate the effects of combined technologies on biogas slurry treatment. Chemical flocculation can remove the total solids (TS), chemical oxygen demand (CODcr), total phosphorus (TP), and total nitrogen (TN) at rates of 89.4%, 95.9%, 98.0% and 73.9%, respectively. However, removal of ammonia nitrogen (${\mathrm{NH}}_4^{+}─\mathrm{N}$) (37.1%) and soluble potassium (3.4%) is poor. A facultative oxidation pond can remove ${\mathrm{NH}}_4^{+}─\mathrm{N}$ and soluble K at rates of 63.5% and 47.5%, respectively. In addition, an ecological forest can remove ${\mathrm{NH}}_4^{+}─\mathrm{N}$, soluble K, and TP at rates of 93.1%, 54.9%, and 70%, respectively. Heavy metal pollution is effectively controlled through the whole workflow. Ultraviolet disinfection is still required for pathogen elimination, although the combined processing has a remarkable impact on the removal of fecal coliforms and total coliforms.

Actual data of greenhouse gas (GHG) emissions from Ontario’s large landfills were compared with data generated by a first-order decay model. Different scenarios were developed and compared based on their associated GHG emissions. The life-cycle modeling was made for municipal solid waste (MSW) landfilled until 2015, and the environmental aspects were evaluated for a 100-year period after disposal. The data utilized in the calculations to model the municipal solid waste landfilling scenarios make extensive use of site-specific data from the landfills. The assessment of different scenarios showed that reduction of landfilled organic waste can lead to significant reduction in the potential environmental loads with respect to global warming when compared with the current MSW landfilling. Conventional landfilling with gas collection for electricity generation showed a better performance than the flaring scenario. Landfill gas collection and power generation resulted in a reduction in GHG emissions of up to 78% relative to the methane flaring scenario. Utilization of soil top covers to oxidize methane (use of methanotrophs) has been demonstrated to drastically reduce environmental burdens.