Journal of Environmental Engineering

The application of membrane bioreactor (MBR) processes for conventional, municipal and industrial wastewater treatment [e.g., biological oxygen demand (BOD) reduction] is well established. The research and development of MBR processes for nitrogen removal is more recent. To date, no thorough review of MBR technology for nitrogen removal from wastewater has been carried out. The review presented here provides an overview of MBR process configurations for the removal of nitrogen based on conventional nitrogen-removal pathways (i.e., nitrification/denitrification) as well as alternative nitrogen-removal pathways, such as anaerobic ammonium oxidation (ANAMMOX). A wide range of system configurations have been explored for the application of MBR for nitrogen removal, including immersed or side-stream membrane configurations, single or multichamber processes, and the application of fixed and moving bed biofilms. Operating variables play an important role in controlling nitrogen removal and fouling, especially feed composition (particularly the $\mathrm{carbon}:\mathrm{nitrogen}$ ratio), membrane characteristics, solids retention time, and hydraulic retention time. Modeling approaches for predicting nitrogen removal using MBR are evolving and are better able to represent key process differences in MBRs compared to conventional activated sludge. Although several challenges remain (e.g., membrane fouling, cost, and energy consumption), a number of opportunities exist (such as new reactor configurations, new microbial pathways, and development of a better understanding of process function through metaomic approaches) that may lead to the broader application of MBR processes for nitrogen removal from municipal wastewater in the future.

This study presents a critical review of disclosed, documented, and malicious cybersecurity incidents in the water sector to inform safeguarding efforts against cybersecurity threats. The review is presented within a technical context of industrial control system architectures, attack-defense models, and security solutions. Fifteen incidents were selected and analyzed through a search strategy that included a variety of public information sources ranging from federal investigation reports to scientific papers. For each individual incident, the situation, response, remediation, and lessons learned were compiled and described. The findings of this review indicate an increase in the frequency, diversity, and complexity of cyberthreats to the water sector. Although the emergence of new threats, such as ransomware or cryptojacking, was found, a recurrence of similar vulnerabilities and threats, such as insider threats, was also evident, emphasizing the need for an adaptive, cooperative, and comprehensive approach to water cyberdefense.

India’s soil-water systems provide a vital source of freshwater and sustain the drinking water supply for the world’s second-largest population. However, groundwater within the large geographical area of India continues to be affected by geogenic pollution and industrial spills. Thus, an effort has been made to review the studies performed to investigate distributions and behaviors of major pollutants of Indian soil-water systems. Furthermore, a state-of-the-art literature survey has been performed to understand the progress in wetland hydrology and in the estimation of greenhouse gas (GHG) emissions from India’s soil-water systems. The geochemically induced health issues have been presented here. Five major observations have been noted as follows: (1) the majority of aquifers in India are highly affected by multiple pollutants, i.e., arsenic (As), fluoride (F), nitrate (N), selenium (Se), uranium (U), and hydrocarbons; (2) although there is sufficient literature on laboratory and field investigations of individual pollutants’ behavior in India soil-water systems, these investigations haven’t been performed for multipollutants; (3) scant information is available on reactive solute behaviors in Indian wetland systems; (4) significant work has been done in the past to estimate GHG emissions from Indian wetlands, dams/reservoirs, forests, and crop lands, but very limited information is available on its connectivity with local and regional hydrological processes and water quality; (5) large populations are affected by serious health issues such as dental/skeletal fluorosis, malignancy, and hyperkeratosis in areas highly contaminated with multipollutants. This is the first study to present the current status of multi-pollutants’ distributions and behaviors in Indian soil-water systems and associated health hazards. The manuscript will help policy makers, geochemists, and environmental scientists to frame management and remediation plans for polluted sites in India.

Batch and fixed-bed adsorption experiments were conducted to evaluate the feasibility of using activated carbon to remove sulfolane from aqueous media. Nine commercially available activated carbons with different particle sizes and surface characteristics were obtained, and their effectiveness in removing sulfolane from water was examined. The impact of operational parameters such as pH, temperature, water quality, and presence of cocontaminants on sulfolane adsorption was also investigated. In addition, pilot-scale experiments were conducted to assess the applicability of activated carbon adsorption under field conditions. The results indicated that coconut shell–based activated carbon had the highest sulfolane adsorption capacity. Adsorption was significantly affected by the presence of cocontaminants. The pilot study indicated that activated carbon can be used to remove sulfolane from groundwater.

Decisions to accept side-stream wastes at municipal wastewater treatment facilities require knowledge about potential impacts on plant operations. Among potential waste streams, coastal communities are increasingly asked to accept boat waste (sometimes termed boat sewage). Boat waste is black water (water from toilets) from recreational boats and yachts. Efforts to decrease the discharge of boat waste directly into natural waters have resulted in increased requests to wastewater treatment plants located near boat-waste pump-out facilities to accept this waste stream. In this study, boat waste is characterized from pump-out facilities on the Salish Sea (located in the northwest corner of Washington State, USA). Impacts on activated sludge function of shock loading up to 10% boat-waste volumes were evaluated. Measured concentrations showed boat waste to contain $60\times$ the ammonia, $10\times$ the chemical oxygen demand (COD), $20\times$ the reactive phosphorus, $15\times$ the salinity, and $7\times$ the total suspended solids (TSS) of typical sewered wastewater. When added to activated sludge, boat waste often increased oxygen uptake rates, settleability, and foaming. These responses were primarily linked to boat-waste strength, although deodorants added by boat owners were also implicated. Quadrupole time-of-flight liquid chromatography mass spectrometry (LC/Q ToF-MS) was used to compare organic compounds within boat waste and three common deodorant products. These results documented that shock-loading boat waste can create conditions leading to treatment upset and that results differ between sources of activated sludge. Continued research is required to evaluate the potential for adaptation of activated sludge microbial communities to boat-waste impacts, including high-nitrogen ammonia loadings.

The first full-scale remediation project in North America to use the direct placement of activated carbon (AC) into sediments was completed in 2013 in a 2-ha lake on the St. Jones River in Dover, Delaware. The sediment cleanup remedy at this site aims to enhance the sorption capacity of native sediments in the lake to reduce the exposure of bioaccumulative pollutants that currently contribute to fish consumption advisories in the lake. In November 2013, approximately 36 t of AC was applied to the lake over a 2-week period. Posttreatment sampling indicated an average AC concentration of 4.3% by dry weight in surface sediments. The primary monitoring was performed immediately prior to AC application and 1 and 3 years following application. Sediment porewater and surface water measurement using passive samplers showed reductions of 60%–80% of total freely dissolved polychlorinated biphenyls (PCBs), and both were reduced to below the Delaware Human Health Water Quality Criteria. Fish tissue analysis of resident fish samples collected before and 3–5 years after treatment showed reductions of approximately 70% on a lipid-normalized basis and agree with modeled predictions. In contrast, two migratory species caught in the lake showed limited changes in PCB concentrations, likely reflecting greater regional exposure while these fish migrated beyond the lake. Overall, the project demonstrates AC amendment as a viable and effective sediment remediation technology.

Filtration and backwashing during the operation of a membrane bioreactor (MBR) physically induce the cyclic attachment and detachment of microbes on the membrane surface. Thus, permeate flux and backwashing affect the microbial quorum sensing (QS) and quorum quenching (QQ) processes taking place in a biocake layer on a membrane surface. From an analysis of the time to reach a transmembrane pressure (TMP) of 40 kPa (${\mathrm{T}}_{\mathrm{TMP}}$) under different water flux levels, 20 or 40 liter per square meter per hour (LMH), with QQ beads or vacant beads in MBRs, it was found that the accelerated deposition of microbial cells on membrane surfaces at 40 LMH significantly reduced the time for bacteria to initiate QS and, thus, allowed less room for QQ compared with the results at 20 LMH. On the application of backwashing, the TMP jump with QQ beads is more delayed than that with vacant beads in both the 20 and 40 LMH cases. However, the extracellular polymeric substance (EPS) level with backwashing decreased at 20 LMH but increased at 40 LMH regardless of bead type because the reduced fouling rate caused by backwashing provided the bacteria with more time to activate QS, facilitating active EPS production when backwashing is employed at 40 LMH. A biocake porosity analysis revealed that when backwashing was applied, the porosity increased significantly at 40 LMH but remained nearly unchanged at 20 LMH. It is suggested that, at the higher flux level, backwashing allowed enough time for bacteria to initiate QS and, thus, form biofilm with a porous mushroom-like structure. Similarly, the inhibition of QS through the addition of QQ beads indicated dependence on the permeate flux and backwashing. These results suggest that a hydrodynamic condition near the membrane surface could have a considerable influence on the activation of microbial QS, which in turn can affect membrane biofouling in an MBR.

In this study, the environmental multimedia model (EMM) is extended for assessing the heavy metal in a contaminated site. Using numerical analysis, the EMM is advanced as a numerical EMM system (NEMMS) including three computational modules for the source zone, unsaturated zone, and groundwater zone. The NEMMS incorporates a finite-difference method (FDM), finite-element method (FEM), and analytical solutions to analyze the transport of heavy metals in the environment. Additionally, Monte Carlo simulation (MCS) is conducted based on sensitivity analysis to quantify the propagation of parameter uncertainty for in-depth risk assessment. In the case study, the modeling results from both the numerical and analytical methods correspond well to the measured data. The FEM provides better results than FDM under the same conditions for the case study. The most sensitive parameters in the soil and groundwater zones are found to be the retardation factor and hydraulic conductivity. This indicates that the developed NEMMS can provide better spatial and temporal accuracy in assessing the chemical risks to the connected environmental media.

Agricultural land pollution is a big threat globally, which is associated with petroleum industry activities. Hence, the exploration of remedial methods for the treatment of polluted agricultural soils is necessary. In light of this, the biodegradation of petroleum hydrocarbon pollutants is becoming very important. A hydrocarbon degrading Pseudomonas aeruginosa National Collection of Industrial Microorganisms (NCIM) 5514, isolated from crude oil-contaminated soil, has been used for soil microcosm experiments. A bioaugmentation of a contaminated agricultural soil microcosm with P. aeruginosa NCIM 5514 showed $66.07\%\pm 1.09\%$ petroleum hydrocarbons degradation in 60 days. This study has resulted in the biodegradation of a considerable amount of petroleum by using single bacteria in 60 days, employing agricultural soil microcosms. The dilution plate-counting technique indicated a population of the Pseudomonas strain to be $5.00\pm 0.05\times {10}^7$ colony forming units per gram ($\mathrm{CFU}/\mathrm{g}$) at zero day (just after bioaugmentation), which decreased to $0.10\pm 0.02\times {10}^8\mathrm{CFU}/\mathrm{g}$ at 60 days. The survival of this strain in artificially crude oil contaminated agricultural soil microcosm showed its potential to be used as a bioremediation tool toward farmland restoration.

Computational fluid dynamics (CFD) has been applied in secondary settling tank (SST) analysis for more than 30 years. Although great progresses has been achieved, there are still some uncertainties in CFD SST modeling. In this study, a numerical model is used to understand the effects of two model parameters: $r_p$, accounting for particles with poor settling properties in the Takács settling model; and ${\rho }_p$, the dry solids density. Both parameters are used in the user-defined functions to couple solids transport on settling velocity. Also, the differences in turbulence specification methods in prediction of SST performance are evaluated. The results show that the prediction of effluent suspended solids (ESS) is very sensitive to $r_p$. The incorrect specification of $r_p$ may mask real improvements in SST geometry, and may even cause clarification failure prediction under the normal inflow conditions. The value of ${\rho }_p$ has less impact on ESS prediction, and its specification is less critical to maintain ESS prediction consistently with field data. Neither return activated sludge concentration (RAS) nor sludge blanket height (SBH) is sensitive to the effects of $r_p$ and ${\rho }_p$. Additionally, the initial turbulent kinetic energy and turbulent dissipation rate specification methods produce only local effects on the hydrodynamics near the inlet boundary, and none of the performance indicators (ESS, RAS, or SBH) are sensitive to inlet boundary turbulence specification methods.