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.

Due to many industrial and domestic pollution sources gathered around Gehu Lake and the lack of effective reduction measures, the ammonia nitrogen and total phosphorus in a large area of the lake exceed the standard. In order to control the amount of pollutants flowing into the lake, this paper selects two allocation methods to determine the load allocation of ammonia nitrogen and total phosphorus under the constraint of environmental capacity. The environmental fluid dynamics code model is used to verify the validity of the load allocation scenarios. The results showed that the concentrations of ammonia nitrogen and total phosphorus in Gehu Lake were lower by equal proportional allocation than by the contribution ratio allocation method. For ammonia nitrogen, the area exceeding the water quality standard is reduced more by the equal proportional allocation method (up to 100%). While for total phosphorus, the area exceeding the water quality standard is reduced more according to the contribution ratio allocation method (up to 96.3%). Considering that the two pollutants should be reduced simultaneously as much as possible, the equal proportional allocation method can be selected.

De facto reuse (DFR) occurs when surface waters receiving wastewater effluent are used as source water by a downstream drinking-water treatment plant (DWTP). Wastewater effluent may contain high concentrations of N-nitrosodimethylamine (NDMA) precursors. NDMA is a toxic disinfection byproduct (DBP). Nitrification at wastewater treatment plants (WWTPs) reduces NDMA precursors in this effluent. The present work examines NDMA concentrations in the distribution systems of 31 DWTPs subject to high percentages of DFR. WWTPs contributing to this DFR were categorized by extent of nitrogen treatment: no intentional nitrogen treatment, nitrification, or nitrification followed by denitrification. The fraction of upstream effluent discharges receiving nitrogen treatment was calculated, and the relationship between this fraction and observed NDMA concentrations was assessed. Results indicate that high-DFR DWTPs with large fractions of wastewater undergoing nitrification upstream had NDMA concentrations comparable to a representative national sample of plants. High-DFR plants with little upstream nitrification had significantly higher NDMA detection rates and concentrations, with dependence on the distance between the upstream WWTPs and the downstream DWTP. High DFR low nitrification, high DFR high nitrification, and a national data set of plants had detect rates of 79%, 54%, and 50% and median detects of $8.0\mathrm{ng}/\mathrm{L}$, $4.2\mathrm{ng}/\mathrm{L}$, and $3.8\mathrm{ng}/\mathrm{L}$, respectively, when considering a 150-km cutoff. This suggests that nitrification at WWTPs may have an added benefit of reducing NDMA formation at chloraminating DWTPs located downstream in high-DFR areas.

This study evaluates the adsorption capacity of syngenetically modified lignin-derived biochar for chalcophile (zinc, Zn), siderophile (copper, Cu) and lithophile (manganese, Mn) ions in single- and multicomponent solutions. Lignin, biochar feedstock, was chosen for the research. Lignin was pyrolyzed at 450°C for 2 h. The experiments studied how adsorption depends on adsorbent dose ($0.10–0.30\mathrm{g}$), pH (2–10), contact time ($5–180\min$), temperature (25°C–45°C), and initial concentrations of elements in solution ($25–150\mathrm{mg}/\mathrm{L}$). The impact of contact time was also investigated using breakthrough curves. The adsorption of multicomponent, potentially toxic elements by lignin-derived biochar was lower than the adsorption for single-component, potentially toxic elements. In all cases, Cu(II) had the highest adsorption efficiency and capacity. The adsorption processes of Cu(II) were also the most spontaneous and thermodynamically favored. The $\mathrm{\Delta }G°$ values of these processes were almost always negative and much lower than those during the adsorption of the other elements studied. The adsorption process in single-component and multicomponent Zn(II) and Cu(II) solutions and in the multicomponent Mn(II) solution was endothermic and physical in nature. The adsorption of elements in the single-component Cu(II) solution and the single-component Zn(II) solution by lignin-derived biochar was more in line with the pseudo-second order equation model (${\mathrm{R}}^2=0.8697$ and ${\mathrm{R}}^2=0.5359$, respectively). The experimental data was modelled by various isotherm models. The results revealed that adsorption isotherm in the case of single-component Zn(II) was more in conformity with the Langmuir isotherm (${\mathrm{R}}^2=0.79$), suggesting the dominant adsorption of lignin biochar was via monolayer adsorption. Meanwhile, the adsorption isotherm in the case of single-component Mn(II) was well fitted to the Freundlich adsorption model (${\mathrm{R}}^2=0.79$), indicating adsorption was multilayer in nature.

Low impact development (LID) practices contribute to the reduction of flooding and improvement of water quality. Water crises may be a result of water scarcity and flooding due to climatic changes and the increase of impervious areas, and thus, stormwater harvesting becomes a sustainable alternative solution for relative water problems. The performance of a bioretention system with the submerged zone (SZ) and unsaturated zone (USZ) was evaluated as an alternative for stormwater harvesting. The study was carried out on a laboratory scale, using a bioretention box to simulate the processes that occur in a real system and in the field. The system was efficient in removing TP (68.5% and 76.5%), COD (71.6% and 56.9%), and ${\mathrm{NO}}_2$ (28% and 16.6%) in USZ and SZ events, respectively. ${\mathrm{NH}}_3$ removal (31%) occurred only at SZ events. ${\mathrm{NO}}_3$ was exported at all events tested but at values below the Brazilian CONAMA Resolution 357/2005 on the quality of water bodies for supply. The bioretention effluent showed relatively high values of turbidity; however, the pH parameter presented good values in all experiments ($>6.5$ and $<7.5$), and E. coli only in some cases presented satisfactory values to meet the Brazilian Standard for Rainwater Usage for nonpotable purposes ($<200\mathrm{MPN}/100\mathrm{mL}$). In general, both configurations provide different improvements for stormwater to support sustainable water resources management. This study presents a comparison between bioretention systems with and without SZ as an initial proposal for the improvement in bioretention systems in Brazil; however, more experiments must be monitored, and new improvements should be tested for reaching restrictive water reuse purposes.

To enable the evaluation of water treatment efficiency of electrochemical advanced oxidation processes (EAOPs), an approach to remove ${\mathrm{H}}_2{\mathrm{O}}_2$ as a catalytic pretreatment was investigated to avoid interference in chemical oxygen demand (COD) measurements. Four wastewater types with COD and ${\mathrm{H}}_2{\mathrm{O}}_2$ concentrations up to $\mathrm{1,300}\mathrm{mg}/\mathrm{L}$ and $90\mathrm{mmol}/\mathrm{L}$, respectively, were investigated with a novel method. The method requires the addition of sodium bicarbonate (${\mathrm{NaHCO}}_3$), which decomposes ${\mathrm{H}}_2{\mathrm{O}}_2$ at ambient temperature within 24 h without changing COD. For synthetic wastewater (SWW), this time is reduced to 1 h by heating at 70°C. A side-by-side comparison of ${\mathrm{NaHCO}}_3$ and ${\mathrm{Na}}_2{\mathrm{CO}}_3$ experiments confirmed ${\mathrm{H}}_2{\mathrm{O}}_2$ removal without changes in COD via ${\mathrm{NaHCO}}_3$, whereas a $\sim 20\%$ decrease in original COD was observed using ${\mathrm{Na}}_2{\mathrm{CO}}_3$. The change in COD during catalytical ${\mathrm{H}}_2{\mathrm{O}}_2$ decomposition in ${\mathrm{Na}}_2{\mathrm{CO}}_3$ solution was highly correlated with the high pH value.

This study conducted a facile solvothermal method along with a dip-coating process to simplify the fabrication and optimize the morphology of $\mathrm{Ti}/{\mathrm{SnO}}_2$ and $\mathrm{Ti}/\mathrm{Sb}\text{-}{\mathrm{SnO}}_2$ electrodes. Electrodes as prepared exhibit a uniform surface with scattered catalyst particles. Characterization and performance of different Sb doping ratios have been compared and discussed. The best Sb doping ratio has been confirmed at 2.5%at. Compared with the $\mathrm{Ti}/{\mathrm{SnO}}_2$ electrode, the Ti/Sb $(2.5\%)\text{-}{\mathrm{SnO}}_2$ electrode exhibited slightly lower oxygen evolution potential with up to three-fold increment for LSV current density, more than two-fold increment for ${\mathrm{C}}_{\mathrm{dl}}$, a much better electrochemical resistance and 52% longer service life. The accelerated service life of Ti/Sb $(2.5\%)\text{-}{\mathrm{SnO}}_2$ electrode reaches $22.9\mathrm{h}$, which is excellent compared with other studies with complicated manufacture. After $45\min$ of electrolysis, decolorization efficiency of reactive blue 4 on $\mathrm{Ti}/{\mathrm{SnO}}_2$ and Ti/Sb $(2.5\%)\text{-}{\mathrm{SnO}}_2$ electrodes reaches 94.0% and 96.7%, respectively. Intermediates of RB4 decolorization were identified by GC-MS. The method presented here may contribute to reducing the cost of wastewater treatment and broadening electrochemical oxidation application.

The removal of 10 pharmaceuticals and 3 of their metabolites from municipal wastewater by ultraviolet irradiation at a wavelength of 254 nm (UVC) and $\mathrm{UV}/{\mathrm{H}}_2{\mathrm{O}}_2$ were investigated in this study. Experiments were conducted at a full-scale test facility embedded in an operating wastewater treatment plant. The results give a uniquely clear representation of the effectiveness of these processes for full implementation. Parametric studies on UV intensity and ${\mathrm{H}}_2{\mathrm{O}}_2$ dosage were performed, with accompanying analysis of feed water variability. Removal by UV photolysis was compound specific, with more than 70% sulfamethoxazole, caffeine, ciprofloxacin, fluoxetine, and norfluoxetine being removed with $\mathrm{1,400}\mathrm{kJ}/{\mathrm{m}}^3$ of UV fluence. Under similar conditions, 20%–70% removal of metformin, acetaminophen, cotinine, and erythromycin occurred, while $<20\%$ removal of trimethoprim, venlafaxine, O-desmethylvenlafaxine, and carbamazepine was found. The addition of ${\mathrm{H}}_2{\mathrm{O}}_2$ provided little benefit over UV irradiation alone. Therefore, the addition of ${\mathrm{H}}_2{\mathrm{O}}_2$ to UV treatment is only marginally beneficial over UV photolysis for degradation of very low concentrations of pharmaceuticals in municipal wastewater. $\mathrm{UV}/{\mathrm{H}}_2{\mathrm{O}}_2$ is expected to be more effective in waters with higher concentrations of pharmaceuticals, such as reverse osmosis reject water.

Wet basins manage hydrologic quantities, particulate matter (PM), and chemicals. Residence time (RT) and hydraulic residence time (HRT) are common metrics to index presumptive water chemistry and PM load response. Models for the response of basin designs were studied. Basin hydrodynamics (based on geometry, inlet layout, and baffles), and PM separation based on influent particle-size distribution (PSD) were indexed with RT and HRT. PM separation and economics were examined for seven basin designs ($\mathrm{HRT}=0.25–21\mathrm{days}$). Scaled designs were patterned geometrically from an existing basin that was oversized based on flows and PSDs. Computational fluid dynamics (CFD) with continuous simulation, surface overflow rate (SOR), and first-order decay models were studied. Basin geometrics, PM separation, and constituent RT were modeled across a representative wet season. The results demonstrate that PM separation is sensitive to influent PSD and basin sizing for 1–5-day HRTs, with less sensitivity to PSD for larger volumes of 5–21-day HRT. Constituent RT (based on PM) varies in the wet season and remains below the HRT. Basin retrofit geometry and inlet layout impact constituent RT and PM separation. HRT alone, from any model tested herein, is not recommended in assessing basin treatment for less than a 5-day HRT, or if the PSD is unknown. For basins with greater than 1-day HRT, transport behavior is approximated reasonably assuming steady flow. Although PM separation is insensitive to HRT beyond a 5-day design, increasing basin size impacts economics. Results indicate that the 14-day basin HRT is not an optimal benchmark for treatment.

The present article focuses on the bioremediation of diesel from simulated wastewater at different pollutant concentrations using a novel indigenous microalgal-bacterial consortium isolated from Kovalam Beach, India. The consortium was characterized using transmission electron microscopy (TEM). The consortium was tested for its sustainability at different diesel concentrations ($150–\mathrm{1,000}\mathrm{mg}/\mathrm{L}$), at which its pollutant removal potential was assessed. Maximum (79.62%) and minimum (49.35%) removal was achieved at $500\mathrm{mg}/\mathrm{L}$ and $\mathrm{1,000}\mathrm{mg}/\mathrm{L}$ initial concentrations of pollutant, respectively. Production of biomass and biomolecules was also analyzed during the removal of diesel at its different concentrations. A logistic model was used to predict the kinetics of consortium growth during the treatment of simulated wastewater. The reusability of the previously used consortium was tested by its use in a further set of experimentations for removal of pollutants, and 90% removal of diesel having $500\mathrm{mg}/\mathrm{L}$ concentration was found. The characterization of untreated and spent biomass was done with Fourier transform infrared (FTIR) spectroscopy.

Permeable pavement (PP) can be a primary source-area component of a sustainable drainage system. PP facilitates runoff reduction and particulate matter (PM) separation. PM separated by the PP surface reduces hydraulic conductivity ($K$) and influences PP functionality and maintenance. Pragmatic and reproducible methods are necessary to identify $K$ reduction and maintenance. Because $K$ is the proportionality constant between specific discharge and hydraulic gradient (Darcy’s law), disparate test methods and conditions produce disparate $K$ results. Consequently, evaluations based solely on $K$ can lack guidance when the goal is runoff reduction. Herein, PP response is examined based on $K$, outflow time (OT) through the PP across a fixed driving head range, and volumetric runoff coefficient ($C$). The PP test matrix parameters are (1) total porosity from 0.15 to 0.25, (2) rainfall loading from 0 to $150\mathrm{mm}/\mathrm{h}$, (3) PM aerial loads from 0.5 to $2.0\mathrm{kg}/{\mathrm{m}}^2$ as a silty-sand schmutzdecke, (4) slopes from 2.5% to 7.0%, and (5) PP maintenance. Results demonstrate (1) higher PM aerial loads increase OT ($K$ decreases), (2) higher total porosity decreases OT ($K$ increases), and (3) higher rain rates inconsistently produce lower OT compared with the no-rainfall control at higher PM aerial loads. For all tests ($N=285$) with $C$ measurements, lumping all other parameters, the mean $C$ is 0.07, the standard deviation is 0.11, and the maximum is 0.67. These $C$ results are significantly lower than impervious pavements. As the PP slopes and PM aerial loads increased, $C$ increased and $K$ decreased but with no clear trend between $K$ and $C$. For tests where $K<0.01\mathrm{mm}/\mathrm{s}$ and $\mathrm{OT}<300\mathrm{s}$, $C$ was $<0.35$. An OT limit of 300 s provides guidance for PP conditions that provide runoff reduction, with $C<0.20$ for 2.0% slopes. PP conditions in this limit provide discernable runoff reduction. OT and $C$ can be pragmatic adjuvants with disparate $K$ methods.

In order to reduce process complexity and manufacturing difficulty, we proposed to use a single air distribution plate to guide the flow and achieve uniform air distribution. We established a three-dimensional model with a size ratio of $1:1$ to simulation flow pattern. The optimization results revealed that it is feasible to implement our assumption. After the asterisk plate’s optimization, the area uniformity index in the catalytic section was maintained above 0.92 with a maximum value of 0.95, the relative standard deviation was lower than 0.2, and the minimum value was 0.123; and the pressure drop was less than 3.00 Pa, which is in line with the actual use requirements. Among them, Asterisk I with a 30 mm thickness and 15 mm right shift has the best optimization effect.

The identification of E. coli bacteria is critical for the prevention of health risks. According to EPA-approved gold standard methods, 24–48 h are required to count viable cells in water. Manual counting of viable bacteria colonies on agar plates is time-consuming and can be prone to human error. The method requires experts to identify and count colonies on agar plates using a microscope. Hence, the bacterial counting procedure must be automated in order to decrease error. The main objective of this study was to develop an automatic system for bacteria colony counting. A total of 1,301 groundwater samples were collected from eight districts in Rajasthan, India, for a field investigation. The results were validated using artificial intelligence (AI) methods on this experimental data set. We automated the process of E. coli bacteria identification using a convolutional neural network (CNN). We developed a smartphone application for the rapid detection of E. coli bacteria on agar plates using CNN. We also automated the process of bacteria colony counting using faster region-based convolutional neural network (R-CNN) to overcome manual cell counting process limitations. A graphical user interface (GUI) application was created to rapidly count bacteria colony–forming units on agar plates using faster R-CNN. The developed faster R-CNN model achieved an overall accuracy of 97% and an error (loss) of 0.10. The performance of the CNN and faster R-CNN models was validated using F-score, precision, sensitivity, and accuracy statistical measures. The comparative analysis showed that the faster R-CNN model is reliable and effective in E. coli cell counting. The study developed a system for identifying and counting viable cells of E. coli bacteria in water that can be used to forecast hotspots of water contamination.

A sequencing batch reactor was constructed to realize simultaneous nitrification and denitrification (SND) and denitrifying phosphorus removal (DPR). The influence of different carbon sources (acetate, acetate and propionate, and propionate) was explored. The total nitrogen (TN) removal efficiency reached the highest value of 66.4% with acetate. The total phosphorus (TP) removal efficiency was nearly the same (97.9%–96.1%) with different carbon sources. Propionate facilitates TP removal during the hypoxic stage to weaken glycogen metabolism in phosphorus-accumulating organisms (PAOs) and promote dehydrogenase and phosphorus removal–related enzyme activities. Propionate also facilitates the competitiveness of PAOs against glycogen-accumulating organisms (GAOs). TN removal during the SND process in the hypoxic stage was maintained at 38.2%–40.2%, which is explained by the relative amount of change in nitrifying and denitrifying microorganisms. However, acetate promoted TN (from 9.2% to 17.3%) and TP (from 18.1% to 22.7%) removal during the DPR stage, thus enhancing final TN removal and maintaining TP removal. Consequently, acetate may be a better choice for a SND-DPR–coupled system.

The suspended ion exchange (SIEX) process is an emerging technology for the removal of dissolved natural organic matter (NOM). To facilitate the SIEX selection, design, and operation, a usable mechanistic model is proposed. The simple kinetic model unifies the Lagergren equation and the Glueckauf model and has analytical solutions for common SIEX processes. It is shown, through comparison with experimental data, that the proposed model describes SIEX effectively. The plug-flow and the mixed-flow processes, such as SIX and MIEX, treat the removable NOM well. At (removable NOM) removal efficiency above 50%, though, both SIEX processes increasingly run into poor resin capacity utilization due to the process thermodynamic constraint and, to a lesser extent, the kinetic effect. The choice of chloride-form or bicarbonate-form resin has little effect on the adsorption distribution constant of removable NOM. Replacing chloride with bicarbonate as the counterion, however, increases the nonremovable NOM fraction, i.e., causes an additional amount of NOM unable to access the adsorption sites. The result of counterion binding suggests that the nonremovable NOM fraction is just a mixture of the NOM compounds that have insufficient affinity to displace resin counterion from adsorption sites and raises question on the hypothesis in the literature that attributes the nonremovable NOM to the uncharged NOM species only.

A study on the adsorption capacity and mechanisms on cow manure (CM400-5) and corn stover (CS700-2) biochar to remove typical heavy ions from water has been performed. The ${\mathrm{Cd}}^{2+}$, ${\mathrm{Cu}}^{2+}$, ${\mathrm{Pb}}^{2+}$, and ${\mathrm{Zn}}^{2+}$, commonly found in the first flush of the urban/industrial stormwater runoff, were tested under controlled conditions. The obtained experimental data were modeled with the Freundlich, Langmuir, and Harkins–Jura isotherms to describe the adsorption pathways. The novel solubility-normalized Dubinin–Radushkevich (D-R) approach is introduced for the determination of the adsorption mechanisms. The solubility-normalized mode emphasizes the importance of the solubility concentration in calculating the mean free energies of adsorption used to identify removal mechanisms. The proposed model was experimentally validated for the carbon-based (biochar) adsorbers and inorganic (heavy metals) ions. Comparison of obtained results with the commonly used nonnormalized D-R model shows a likely underestimation of the mean free energy values, which could misrepresent the dominant mechanism of adsorption.

In this study, an intensive performance assessment of 36 sewage treatment plants (STPs) is carried out. The STPs were based on the process technologies: moving-bed bioreactor (MBBR), sequencing batch reactor (SBR), waste stabilization pond (WSP), and upflow anaerobic sludge blanket reactor (UASB) with posttreatment technologies of extended aeration (EA), surface aeration, and polishing ponds, with treatment capacities of 3 to 40 million L per day. The pollutant removal performance of the STPs was ranked using the gray relational analysis method, which revealed that the SBR systems ranked higher, followed by UASB with EA, whereas MBBRs, UASB with other posttreatment options, and WSP performed satisfactorily to poor. Further, the preference ranking organization method for enrichment evaluation (PROMETHEE) multiple-criteria decision-making (MCDM) approach using the fuzzy analytic hierarchy process followed by preference ranking organization method for enrichment evaluation method evaluated the major wastewater treatment technologies using three sustainability criteria: environmental, economic, and technical aspects. The MCDM method evaluation revealed that the UASB + EA method, with its lower greenhouse gas emissions, energy requirement, sludge generation, and energy and resource recovery characteristics, outranked other treatment technologies, followed by SBR. The MCDM results were later confirmed using geometrical analysis for the interactive aid method. Hence, this study summarizes that the anaerobic process followed by microaerobic technologies still possesses the capability to achieve stringent disposal standards almost equivalent to intensive aerobic technologies.

Some wastewater treatment (WWT) facilities are using magnetite in their treatment process, through a technology called BioMag, and stabilizing their wasted sludge using anaerobic digestion (AD) after recovering most of the magnetite for reuse. This research investigated whether this magnetite would benefit the AD process to assess the possibility of magnetite recovery after AD, which could reduce the loading on the recovery equipment as well as operation and maintenance costs of magnetite recovery due to decreased sludge quantities. Because some conflicting results were found in previous studies, which could be due to particle size, or to particle stability, because some studies used synthesized magnetite particles that can be unstable, which may affect the properties and behavior of the magnetite, this study used the same magnetite supplied for the BioMag process. The effects of this magnetite on biogas production, biogas composition, hydrogen sulfide gas (${\mathrm{H}}_2\mathrm{S}$) reduction, and digester effluent were investigated. Results showed an increase in the effluent dissolved iron and a 49% reduction in ${\mathrm{H}}_2\mathrm{S}$. No considerable effect was seen on the gas volume and composition.