Journal of Environmental Engineering

Anaerobic membrane bioreactors (AnMBRs) have received significant attention in the field of wastewater treatment due to their lower energy demand than traditional aerobic MBRs. AnMBRs have been successfully adopted for nonpotable reuse applications. However, water-quality challenges ($\sim 4–170\mathrm{mg}/\mathrm{L}$ chemical oxygen demand (COD) in the permeate, literature value), membrane fouling, energy consumption (0.1–2.6 kWh/m³, literature value), and methane recovery from the permeate are challenges that still need to be overcome if AnMBRs are to be recognized as a sustainable wastewater reuse technology. This paper reviews state-of-the-art conventional AnMBRs, decentralized AnMBRs, and hybrid AnMBRs in the context of treating different types of wastewater for nonpotable water reuse and energy recovery. Comparisons of permeate quality and energy consumptions in different hybrid AnMBRs are performed, and the challenges of AnMBRs for nonpotable water reuse are discussed.

This study employed quantitative polymerase chain reaction (qPCR) to evaluate the occurrence and removal of five microbial surrogates at two water reuse facilities. The surrogates were (1) the 16S rRNA gene; (2) the AllBac assay for Bacteroides; (3) the Bacteroides bacteriophage $\varphi \mathrm{B}124\text{-}14$; (4) the Bacteroides bacteriophage ϕcrAssphage; and (5) the pepper mild mottle virus (PMMoV). Log removal values (LRVs) were quantified for a membrane bioreactor (MBR) and across a full advanced treatment (FAT) train. PMMoV, $\varphi \mathrm{B}124\text{-}14$, and $\varphi \mathrm{crAssphage}$ were detected in the MBR feed at concentrations of approximately ${10}^3\mathrm{gene}\mathrm{copies}(\mathrm{gc})/\mathrm{mL}$, ${10}^5\mathrm{gc}/\mathrm{mL}$, and ${10}^6\mathrm{gc}/\mathrm{mL}$, respectively. Only PMMoV was above the limit of quantification (LoQ) in the MBR filtrate ($25\pm 8\mathrm{gc}/\mathrm{mL}$), resulting in a wide range of viral LRVs: $1.4\pm 0.5$ for PMMoV, $>3.9\pm 0.3$ for $\varphi \mathrm{B}124\text{-}14$, and $>6.2\pm 0.3$ for $\varphi \mathrm{crAssphage}$. All molecular targets were above the LoQ in the biologically treated FAT feed, but only the bacterial 16S rRNA gene was $>\mathrm{LoQ}$ after ozonation and biological activated carbon (BAC) and in the reverse osmosis (RO) concentrate. The gene was $<\mathrm{LoQ}$ in the RO permeate and after the UV advanced oxidation process (AOP).

In case of failure, hazardous liquid pipelines can have adverse environmental consequences. This study presents a method to predict the occurrence of certain environmental impacts resulting from hazardous liquid pipeline accidents. Explanatory variables, including pipe diameter, commodity transported, and incident area type, are used to train an adaptive neuro-fuzzy inference system (ANFIS). Three impact types are analyzed: water contamination, soil contamination, and impact on wildlife. Results show that the model can accurately predict whether a pipeline segment with given design characteristics could lead to adverse environmental impacts due to failure (14%, 6%, and 3% error for soil and water contamination and impact on wildlife, respectively). This model can be used in pipeline design and risk management planning to minimize the potential for environmental consequences. However, more comprehensive and robust reporting requirements beyond simple occurrence would improve our ability to prioritize these mitigative actions.

To remove heavy metals from polluted water efficiently and cost-effectively is a big challenge. This paper reports on a spongy crosslinked branched polyethylenimine-grafted dithiocarbamate (CBP-G-D) adsorbing material, which was prepared by crosslinking branched polyethyleneimine (PEI) with glutaraldehyde to form a crosslinked polymer, and then reducing the resulting C = N double bonds with sodium borohydride to give a crosslinked polyamine polymer and finally grafting on it with carbon disulfide. Scanning electron microscopy (SEM) verified that it was a spongelike three-dimensional network material. At room temperature, the material can efficiently uptake heavy-metal ions such as cadmium (II), copper (II), and lead (II) from wastewater based on complexation and van der Waals force. Its adsorption capability for cadmium (II), copper (II), and lead (II) reached 1.83, 3.23, and $2.18\mathrm{mmol}/\mathrm{g}$ within 40 min, respectively; the removal percentages reached 99.85%, 99.38%, and 99.82%, respectively. Another advantage of this material is its recyclability.

In recent years, reverse osmosis (RO) systems have been highly utilized in industrial processes. One of the most important operational issues of these systems is membrane fouling, which leads to high operating costs and environmental impacts. The purpose of this research is to optimize RO systems’ operation to reduce fouling, increase membrane life span, and minimize system costs. To achieve this purpose, first, RO system characteristics are simulated using a general regression neural network (GRNN) artificial neural network. Then, the controllable factors affecting the performance of the system are optimized by the application of a single-objective optimization model with the total operating cost minimization as an objective function. The proposed method is applied to an under-operation RO system used in a car manufacturer factory in Iran. Based on the results, the optimal values of the inflow, inlet pressure, and recovery rate were $10.4{\mathrm{m}}^3/\mathrm{h}$, 7.4 × 10⁵ Pa, and 60%, respectively. Accordingly, the total operational cost of the system will be $1,525.95. Moreover, by an appropriate operation, the system can continue to work for more than 5,000 h without the need for cleaning.

Ultrahigh-volume samplers with a flow rate of approximately $500{\mathrm{m}}^3/\mathrm{h}$ are widely used for atmospheric radionuclide monitoring. These samplers are often shut down during heavy particulate pollution due to filter clogging. We proposed a solution involving sampling with an impactor to reduce the filter clogging and avoid sample loss. A multislit impactor was designed to keep its low pressure drop and to save space in the context of an ultrahigh flow rate. Nonwoven cloth was chosen as impaction substrate for a low cut size, high dust capacity, and convenient operation. An undulating jet plate was designed to reduce particle loss on its surface and this was predicted by computational fluid dynamics (CFD). The test experiment results show that the cut size of the impactor is approximately 1.5 μm, and the particle loss is only 5% with loess aerosol as the challenge. Field tests show that the atmospheric large particles collected by the impactor was average approximately 0.53; the concentrations of ${}^{131}\mathrm{I}$ and aerosol mass are consistent with those from commercial Hi-Vol total suspended particles (TSP) sampler ($63{\mathrm{m}}^3/\mathrm{h}$) by $\pm 10\%$. Results from the laboratory and field tests suggest that the impactor presented in this study constitutes a major improvement in the reduction of the filter clogging in ultrahigh-volume aerosol samplers under heavy particulate pollution.

The Combined Activated Sludge Anaerobic Digestion Model (CASADM) was configured to represent the operational results of a full-scale Cannibal wastewater treatment plant that operated over a 2-year period and had a net sludge yield that was low, approximately $0.21$ g volatile suspended solids/g chemical oxygen demand (g VSS/g COD) removed based on the model. CASADM accurately described available information on effluent quality and mixed-liquor volatile suspended solids (MLVSS) concentrations in each tank. Modeling results led to important insights into what led to the low net sludge yield of this Cannibal plant. For example, widespread net decay or slow growth [negative or very large positive values of solids retention times (SRTs)] of biomass caused total active biomass to be only 13%–21% of the MLVSS, and about 28% of the total input COD was converted to ${\mathrm{CH}}_4$ in the system. Input of active biomass and a low sludge-wasting rate proved to be key factors causing net decay or slow growth of active biomass, which, when combined with significant ${\mathrm{CH}}_4$ production, led to low net sludge yield.

Quorum quenching (QQ) vessels have been used as an effective method of biofouling control for membrane bioreactors (MBRs), but further studies on the effect of entrapped QQ bacterial levels on the antibiofouling efficacy and stability of the QQ vessel are needed. In the present study, we investigated the efficacy and stability of QQ vessels containing different doses of QQ bacteria (i.e., Rhodococcus sp. BH4) during long-term MBR operation fed with synthetic and real municipal wastewater. It was found that the degradation rate of signal molecules (e.g., $N$-acyl homoserine lactones; AHLs) depended on the numbers of BH4 bacteria in the QQ vessel. The QQ vessel supplying a dose of $135\mathrm{mg}/\mathrm{L}$ of BH4 to the reactor improved fouling mitigation while slowing down the build-up of transmembrane pressure. Biofilm formation on the membrane surface was alleviated by quenching the AHL-based signaling among microorganisms. The delay in membrane fouling had a strong linear correlation with the QQ activity rate constant, and this was more pronounced for the MBR treating real municipal wastewater with lower carbon and nutritional content. The activity of the QQ vessel supplying a dose of $135\mathrm{mg}/\mathrm{L}$ of BH4 gradually increased over time ($>\mathrm{1,200}\mathrm{d}\mathrm{a}\mathrm{y}\mathrm{s}$), confirming that it has the potential for stable long-term use. These results demonstrate that QQ vessels are effective and stable for biofouling control in MBRs treating synthetic and real wastewater.

In this study, a continuous fixed-bed column was investigated for heavy metal removal using modified wheat bran as adsorbent. Clay and chitosan were used as binders with the adsorbent to prepare adsorbent pellets in a $1:1:3$ ($\mathrm{clay}:\mathrm{chitosan}:\mathrm{adsorbent}$) ratio by weight. Clay and chitosan provide adhesiveness and mechanical strength to the pellet. The scanning electron microscopy analysis–energy dispersive X-ray spectroscopy (SEM-EDS) analysis confirms the adsorption of copper, chromium, and cadmium in the adsorbent pellet. The fixed bed was operated at a pH of 6 and temperature of 35°C for heavy metal removal. A mathematical model was prepared for continuous column and then experiments were carried out with various parameters such as bed height (0.15–0.45 m), initial concentration ($100–500\mathrm{mg}/\mathrm{L}$), and flow rate ($5–15\mathrm{mL}/\min$). The removal order for heavy metals follows $\mathrm{Cr}>\mathrm{Cu}>\mathrm{Cd}$. The optimum conditions obtained were a flow rate $5\mathrm{mL}/\min$, bed height of 0.45 m, and initial concentration of $100\mathrm{mg}/\mathrm{L}$. The breakthrough curve obtained from experimental data was compared with the curve obtained from the model. It was found that the prepared adsorbent pellets were efficient at removing heavy metals. The developed mathematical model could predict column behavior with desirable accuracy. Further, high $R^2$, low chi-squared, and mean absolute percentage error (MAPE) values of up to 0.999, 0.025%, and 0.378%, respectively, indicate that model and experimental data were well fitted.

Chromium (Cr) is a toxic contaminant and ubiquitously present in the environment. This study was conducted to investigate the removal of Cr by nano-magnetite ($\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$) in different biogeochemical environments of groundwater. Size of $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ used was in the range of 50–100 nm, and it contained Fe (58.88%) and O (31.13%). Removal rates of total Cr (${\mathrm{Cr}}_{\mathrm{T}}$) by $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ were significantly improved ($0.40–0.84{\min }^{-1}$) as the concentrations of $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ were increased ($0.25–3.75\mathrm{g}/\mathrm{L}$). However, removal rates of ${\mathrm{Cr}}_{\mathrm{T}}$ by $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ were decreased ($1.52–0.66{\min }^{-1}$) as the concentrations of ${\mathrm{Cr}}_{\mathrm{T}}$ increased ($0.5–1.5\mathrm{mg}/\mathrm{L}$). In addition, the removal rate of ${\mathrm{Cr}}_{\mathrm{T}}$ by $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ was significantly increased ($0.56–1.63{\min }^{-1}$) as the pH increased (pH 5.5–pH 9). Removal rates of ${\mathrm{Cr}}_{\mathrm{T}}$ by $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ were significantly decreased ($0.93–0.28{\min }^{-1}$) as the concentrations of humic acid (HA) increased ($0.25–3.75\mathrm{g}/\mathrm{L}$). This study revealed that the reactive surface of $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ plays an important role to enhance maximum removal of ${\mathrm{Cr}}_{\mathrm{T}}$. The surface charge of $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ with or without ${\mathrm{Cr}}_{\mathrm{T}}$ is directly related to the reactive surface area of $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$, which has not been well reported in the literature. Chemisorption reaction mechanisms may occur during the removal kinetics of ${\mathrm{Cr}}_{\mathrm{T}}$ by $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$. Experimental findings from this study proved that $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$ has the capability to remove ${\mathrm{Cr}}_{\mathrm{T}}$ and provided fundamental knowledge on the potential reaction mechanisms of ${\mathrm{Cr}}_{\mathrm{T}}$ removal by $\mathrm{nano}\text{-}{\mathrm{Fe}}_3{\mathrm{O}}_4$.

The reduction of energy consumption in industrial wastewater treatment plants (IWTPs) is an important issue because of global warming, fossil-fuel scarcity, and high energy cost. This paper studied the energy-efficiency index (EEI) of 79 IWTPs across Iran and discussed the impact of different factors on it. Data-envelopment analysis (DEA) was used, in which an efficiency score of 0–1 was allocated for every IWTP. Maximum potential saving, in terms of energy consumption and of ${\mathrm{CO}}_2$ emissions, was measured. It was found that 73.4% of IWTPs had poor energy efficiency, with EEIs lower than 0.3, and only 2.6% of IWTPs achieved an EEI of higher than 0.7. Each effective variable on the EEI of IWTPs, such as treatment plant age and size, COD removal, process type, pumping station, and aeration method, had their own effect on EEI, energy consumption, and ${\mathrm{CO}}_2$ emission. According to the results, the improvement of the EEI of IWTPs will result in 72.9% savings in energy cost, and about 52.8 t less ${\mathrm{CO}}_2$ will be emitted into the atmosphere annually. Therefore, upgrading the EEI of all IWTPs in the world can significantly reduce both energy costs and ${\mathrm{CO}}_2$ emission. The results contribute to energy management in IWTPs.

The application of supported liquid membranes (SLMs) and polymer inclusion membranes (PIMs) for the transport of Cu(II) in a continuous extraction–re-extraction system using di-(2-hethylhexyl) phosphoric acid (D2EHPA) as carrier was examined. The SLM was prepared by soaking a support in D2EHPA-chloroform solution. Furthermore, a PIM was prepared by casting solution containing cellulose triacetate (CTA) as polymer, acetylated kraft lignin as filler, and 40% by weight D2EHPA as carrier and without added plasticizer. Lignin was incorporated into PIMs to enhance the mechanical properties of CTA in acidic media. Transport of Cu(II) ions through SLMs and PIMs was determined. The effect of feed pH, ${\mathrm{HNO}}_3$ concentration in strip phase, and D2EHPA concentration in membrane phase were studied. The optimum conditions to transport more than 68% of Cu(II) are, feed $\mathrm{pH}=4.5$, ${\mathrm{HNO}}_3$ 0.5 M in strip phase and 30% (v/v) of D2EHPA concentration in membrane phase. In the same initial conditions, the PIM containing 40% by weight D2EHPA assured the transport of 74% of Cu (II). The transport of Cu(II) through the SLM and PIM was investigated by evaluating the initial fluxes through the membranes, the recovery efficiency of each, and their stability after many cycles. The experiments demonstrated that the prepared PIM has better performance than the SLM, as proved by a better initial flow, better recovery efficiency, and higher stability. We also confirmed that the interdiffusion of Cu(II) through the PIM followed a kinetic law of first order.

Geo-sequestration of carbon dioxide (${\mathrm{CO}}_2$) in saline formations is one of the feasible options for reducing the concentration of carbon in the atmosphere. This process involves the capturing of ${\mathrm{CO}}_2$ from emission sources followed by its compression and then injecting the compressed ${\mathrm{CO}}_2$ in deep geological formations for its long-term storage. The suitable geological formations for the sequestration of ${\mathrm{CO}}_2$ are normally comprised of sandstones, shales, coal beds, and carbonates. Amongst these, carbonates are the highly reactive formations of a hydrophobic nature and have complex pore structures, and hence, ${\mathrm{CO}}_2$ sequestration and its subsequent evolution in carbonates require a thorough investigation. Further, planning ${\mathrm{CO}}_2$ geo-sequestration in carbonate formations requires assessment of ${\mathrm{CO}}_2$ behavior under high salinity and pressure conditions as these factors play a major role in retaining injected ${\mathrm{CO}}_2$ safely for a long geological time period. Thus, exploring multiphase ${\mathrm{CO}}_2$-brine migration processes in carbonates using practical experiments is of great significance for estimating the storage capacity of potential geo-sequestration sites and for ensuring their storage security. The multiphase characteristic of saline carbonate formations can also get affected during their flooding with supercritical ${\mathrm{CO}}_2$. Hence, the aim of this study was to investigate the movement of ${\mathrm{CO}}_2/\mathrm{brine}$ through different saline carbonate cores under representative reservoir conditions. The laboratory-scale ${\mathrm{CO}}_2$ core flooding experiments were conducted on two different cores of carbonate formations to estimate the effect of salinity and injection pressure on ${\mathrm{CO}}_2$ migration along with the influence of cyclic brine-${\mathrm{CO}}_2$ flooding on characteristics of the considered cores. A series of practical experiments were performed considering 3% and 7.5% levels of salinity under two different injection pressures of 8 and 10 MPa for evaluating the effects of different hydrogeological parameters on the multiphase flow behavior and sequestration capacity of the carbonate formations. For this, brine and supercritical ${\mathrm{CO}}_2$ were injected through Edward white and Edward yellow carbonate cores to obtain the changes in pressure drop across the cores with time. The results show that under high salinity conditions, pressure drop in Edward white and yellow carbonate cores are 2 and 0.3 MPa, respectively, while in the case of low salinity, 1.5 and 0.2 MPa of pressure drop was observed in the selected cores. A high differential pressure (DP) trend was observed using a 10 MPa injection pressure, while a low DP trend was recorded for the 8 MPa injection pressure. An increment in pressure drop across the cores with consecutive injection cycles of brine and ${\mathrm{CO}}_2$ clearly indicates some pores clogging in cores due to the reactive nature of the selected carbonate samples. Thus, the results of this study provide a better understanding of changes that occur at ${\mathrm{CO}}_2$-brine-carbonate interfaces under reservoir like conditions of a typical site, which can help in planning the geo-sequestration of ${\mathrm{CO}}_2$ in carbonate saline formations.

Homoacetogenesis and methanogenesis, which usually occur during anaerobic trichloroethene (TCE) dechlorination, affect the removal of TCE and its daughter products. This study develops a one-dimensional, multispecies ${\mathrm{H}}_2$-based biofilm model to simulate the interactions among six solid biomass species [Dehalococcoides, Geobacter, methanogens, homoacetogens, inert biomass (IB), and extracellular polymeric substances (EPS)] and 10 dissolved chemical species [TCE, dichloroethene (DCE), vinyl chloride (VC), ethene, hydrogen (${\mathrm{H}}_2$), methane, acetate, bicarbonate, utilization associated products (UAP), and biomass associated products (BAP)]. To evaluate and parameterize the model, parameter values from the literature were input into the model to simulate conditions reported for an experiment. The biomass species distribution in the biofilm and the chemical species concentrations in the reactor effluent at a steady state were generally consistent between the experiments and the model. The predicted 15-μm biofilm consisted of three layers, each dominated by a different active biomass type: homoacetogens in the layer next to the membrane, Geobacter in the biofilm surface layer (next to the water), and Dehalococcoides in-between.

This study investigated digestibility of biological trickling filter (BTF) sludge (in terms of the mass and volume reduction of the sludge) and the effect of anaerobic digestion on sludge dewatering. Nine 20-L anaerobic digesters fed with BTF sludge were set up in a dark constant-temperature room at 20°C and operated for 6 months. The anaerobic digesters removed $\sim 33\%$ of volatile solids (VS) after 3 months of operation, and a further $\sim 19\%$ after 6 months of operation (total VS removal = 52%). The average methane production of the digesters was $0.17{\mathrm{m}}^3/\mathrm{kg}{\mathrm{VS}}_{\mathrm{added}}$, which is within the range of literature values for mesophilic (or thermophilic) sludge digestion ($0.15–0.25{\mathrm{m}}^3/\mathrm{kg}{\mathrm{VS}}_{\text{added}}$). Anaerobic digestion substantially improved dewaterability of the BTF sludge, with $\sim 3–5$ times lower specific resistance to drainage (SRD, a parameter describing sludge dewaterability) than fresh or 1-day anaerobically stored BTF sludges. Moreover, the improved SRDs achieved by anaerobic digestion resulted in a decrease in drainage time from $\sim 4$ and 7 h required for fresh and anaerobically stored BTF sludges, respectively, to less than 3 h. These results suggest that the anaerobic digestion could greatly reduce the size of subsequent sludge dewatering and disposal systems such as centrifugation or sludge treatment reed beds.

The growing global food security crisis is complicated by the need for increased crop production with less arable land and limited water resources. Reuse of treated wastewater for agricultural irrigation is becoming more common, often paired with other conservation measures such as subsurface drip irrigation (SDI). Passively injecting air into SDI systems increases crop yields and overcomes root zone wetting issues. However, when used with treated irrigation water, contaminants in the water might be taken up by the crops. This paper investigates the impact of air-injected water containing caffeine, carbamazepine, and gemfibrozil on plant uptake and soil microbial communities in Salanova lettuce (Lactuca sativa). Aerated lettuce yielded higher plant mass and root length. The use of air-injected water reduced the uptake of caffeine and gemfibrozil and increased the uptake of carbamazepine. Gemfibrozil and carbamazepine were primarily detected in leachate, while caffeine was observed in the soil samples. Injected air significantly impacted ($\mathrm{p}\text{-}\text{value}<0.001$) the fate and transport of gemfibrozil. Injection of pharmaceutically active compounds and the presence/absence of injected-air created a variation in soil microbial communities.