Dilute Wastewater Research Articles

Supported liquid membrane with selective stripping for separative recovery of copper and zinc from plating wastewater

For separation and recovery of different but chemically similar metal from dilute wastewater with reduced process complexity and cost, a supported liquid membrane (SLM) system that utilizes a single carrier together with strip dispersion for selective stripping of coextracted metal ions was proposed to enable concurrent separation and recovery. This study aims to investigate the effectiveness of the proposed SLM system for separative recovery of copper and zinc from real plating wastewater. Solvent extraction experiments were conducted to understand the effect of feed pH and carrier concentration on organic phase migration to the aqueous phase. The effect of stirring speed on the SLM transport rate was studied using synthetic feed. Combined with the insights from our previous study, appropriate settings were identified and applied to the SLM system. The SLM system could recover 83.7% copper with 91.0% purity and 85.5% Zn with 99.3% purity from the plating wastewater in 30 h. The findings indicate the feasibility of using SLM with selective stripping for the concurrent separation and recovery of copper and zinc from a dilute aqueous waste stream predominantly containing these two metals.

The Effect of Biological Secondary Treated Domestic Wastewater on Agronomic Properties and Element Content of Some Forage Plants

Aims: This study was carried out to determine the effect of domestic advanced biological treated domestik wastewater on the agronomic properties and nutritional content of some forage crops, as a result of the increasing interest in the use of treated wastewater in agriculture. Material and methods: Biologically treated domestic wastewater was diluted with 25%, 50% and 75% pure water and applied to crested wheatgrass (Agropyron cristatum Geartn), orchard grass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.) pots according to field capacity. Results: Alfalfa, orchard grass and crested wheatgrass plants were used as trial plants. The effect of the diluted wastewater application on the height of crested wheatgrass, orchard grass and alfalfa was significant. From the first mow, alfalfa and orchard grass had increased green and dry weights per pot, with the most marked increase for alfalfa. The wastewater ratios caused an increase in nutrient and metal concentrations in the three plants, while a decrease in the Se concentration in alfalfa and crested wheatgrass. Diluted wastewater not effected alfalfa Ca concentration significantly. While the dilute wastewater significantly and positively effected the relationship of orchard grass with all elements, but Se affected negatively. Soil organic matter and electrical conductivity increased and pH decreased with increasing wastewater ratio. Discussion: Diluted domestic water application played an important role in nutrient and metal concentrations by mediating increased plant element uptake associated with soil organic matter and electrical conductivity responses. Conclusions: However, long-term field studies are required to determine the dilution rate at which the salinity risk threshold can be determined.

IMPACT OF DIFFERENT ORGANIC AND INORGANIC AMENDMENTS ON GROWTH AND YIELD OF MUNG BEAN IRRIGATED WITH TEXTILE EFFLUENTS

Water is an important substance for all life on earth, and it is essential for human beings, financial improvement, and the existence of ecological units. The quality and quantity of the water supply is very important, especially during irrigation. Due to the extensive measurement of water and colour associated with the manufacturing process, textile printing, and dyeing production lines around the world pose a major environmental risk. Textile wastewater contains a lot of pollutants including pH, temperature, shade, COD, BOD, TSS, TDS, EC, and heavy metals. This textile runoff continues to irrigate agricultural land, causing contamination of soils and plant systems with heavy metals. Therefore, adding organic and inorganic modifiers to soil is an effective technique for fixing heavy metals. Irrigate pots with textile wastewater of selected concentrations (10%, 25%, 50%, and 100%) collected in specific industrial sectors. The parameters of vegetative growth are reduced by increasing the concentration of textile effluent. Note the substantial reduction in the growth of plants applying wastewater at 100% concentration. In the case of T5, a significant increase in growth parameters was observed, where only tap water was used to pressurize the sludge, while dilute wastewater also enhanced growth at concentrations of 10% and 25%. For the chlorophyll content of mung bean plants, when the wastewater concentration is 100%, the recorded decrease is greater, followed by 10% and 25% respectively. The presence of heavy metals in wastewater reduces plant growth. In the experiment, all four treatments contained organic amendments (pressed sludge, poultry manure, biogas slurry, and farmyard manure). The other four treatment methods are pressure treatment of textile wastewater and the amount of organic modifier is 2%. By adding a correcting agent, the utilization rate of Cr is reduced, as the correcting agent will increase the pH of the soil, thus reducing the solubility of the metal. In addition, Cr can form insoluble complexes with organic materials, thus reducing its solubility.

Elimination of nickel and chromium(VI) ions from industerial wastewater by electrodialysis/characteristics/impact of parameters

<p>Healthy water is a concern for the world due to rapid population growth and technological advancement. The entry of heavy metals into water as a result of various activities causes water pollution that has persistent effects. In this study, a specially designed electrodialysis cell was used to remove chromium (VI) and nickel ions from wastewater. The chambers were partitioned by Ionac MC 3470 cation exchange and Ionac MA 3475 anion exchange membranes. The cathode and anode were made of carbon fiber and stainless steel, respectively. The effects of voltage, initial pH, time, Na2SO4 concentration, feed flow rate and metal ion concentration on metal removal efficiency, energy consumption, current efficiency, current density and flux were investigated. Optimum values for 98.5% removal of 80 mg/L Cr(VI) ion in 90 min voltage 30 V, pH=3, addition of Na2SO4 0.5 g and feed flow rate 52. 8 ml/min, as observed. At the end of this period, concentration 1 mg/L, energy consumption 40 W/L, flow efficiency 30% and flux 12 x 10.-5 mol/m2s were calculated. Optimum values of 25 V, pH=3, addition of Na2SO4 0.2 g and Qf = 42.6 mL/min were observed for 94.3% removal of 50 mg/L Ni2+ ions in 90 min. At the end of this period, the nickel ion concentration was 4 mg/L, the energy consumption was 34 Wh/L, the flow efficiency was 96.51%, and the flux was calculated as 40×10-5 mol/m2s. This study shows that the electrodialysis method can be effectively used to elimonation chromium (VI) and nickel (II) ions from dilute wastewaters.</p>

Effect of Seed Germination and Early Seedling Growth Response on Two Rice (Oryza sativa) Varieties Supplied with Different Types and Concentrations of Wastewater in Thailand

With increasing concerns over water scarcity, wastewater reclamation for agricultural irrigation has gained attention. However, the use of wastewater can have both positive and negative effects on crop growth. Seed germination and early seedling growth tests are considered to accurately represent crop growth population. This study aimed to evaluate the effect of different types and concentrations of wastewater on rice seed germination and early seedling growth. Two rice varieties, SIRAJ279 and MR219, were grown in wastewater from shrimp culture, domestic sources, and cement factories at five concentrations: 0 (control), 25, 50, 75, and 100%. Seed germination percentage and germination rate index were used to evaluate seed germination analysis, while the seedling length, seedling vigor index, seedling fresh weight, seedling dry weight, and phytotoxicity percentage were used to evaluate early seedling growth analysis. Results showed that the SIRAJ279 rice variety had overall better seed quality than MR219. Rice irrigated with shrimp culture and domestic wastewater showed better results in seed germination, germination rate index, seedling length, seedling vigor index, and seedling fresh weight than those irrigated with cement factory wastewater. However, no significant difference was observed in seedling dry weight. Additionally, increased wastewater concentration had a negative effect on seed and seedling results. Seedlings grown in wastewater with a concentration of 75-100% from cement factories had the highest phytotoxicity percentage (more than 30%). Therefore, it is recommended to dilute cement factory wastewater to 50% before using it for agricultural irrigation.

Развитие методики расчёта нормативов допустимого сброса жидких производственных отходов с учётом региональных особенностей водных объектов

The problem of regulating the discharge of liquid wastes into water bodies is the most urgent task and is carried out on the basis of establishing standards of permissible discharge (SPD). Many authors note that the key problem of setting the SPD is the use of maximum allowable concentrations (MAC) as threshold values, determined without taking into account regional peculiarities of formation of natural water composition and its ability to dilute wastewater. We have proposed the development of the methodology for calculating SPD, based on the condition that ensuring the disposal of liquid wastes at the level of permissible discharge standards will not lead to a change in the water quality class determined using the specific combinatorial index of water pollution (SCIWP). In the previous publication we have substantiated territorial threshold concentrations (TTC) based on the analysis of long-term data sets of hydrochemical observations, which allow us to take into account regional features of the geochemical background of water bodies, including the content of substances of dual genesis. They also implicitly allow taking into account hydrological and hydrochemical factors that ensure the ability of natural waters to dilute liquid waste effluents. The obtained TTCs are proposed to be used for calculation of permissible concentrations of substances in wastewater instead of MAC. SPD is established by cyclic iteration of TTC values by 10%, with parallel calculation of SCIWP, until the index is transferred to another water quality class. This paper presents the results of approbation of the proposed development of the methodology of SPD calculation for liquid waste from Оpen JSC “Kazan Synthetic Rubber Plant” discharged into the Volga River. The obtained calculation results make more stringent requirements to the value of SPD for substances mainly of anthropogenic origin. For some substances of dual genesis, the value of SPD was higher, which allows us to make more adequate requirements to water users for treatment of sewage effluents.

Wastewater-based surveillance as a tool for public health action: SARS-CoV-2 and beyond.

Wastewater-based surveillance (WBS) has undergone dramatic advancement in the context of the coronavirus disease 2019 (COVID-19) pandemic. The power and potential of this platform technology were rapidly realized when it became evident that not only did WBS-measured SARS-CoV-2 RNA correlate strongly with COVID-19 clinical disease within monitored populations but also, in fact, it functioned as a leading indicator. Teams from across the globe rapidly innovated novel approaches by which wastewater could be collected from diverse sewersheds ranging from wastewater treatment plants (enabling community-level surveillance) to more granular locations including individual neighborhoods and high-risk buildings such as long-term care facilities (LTCF). Efficient processes enabled SARS-CoV-2 RNA extraction and concentration from the highly dilute wastewater matrix. Molecular and genomic tools to identify, quantify, and characterize SARS-CoV-2 and its various variants were adapted from clinical programs and applied to these mixed environmental systems. Novel data-sharing tools allowed this information to be mobilized and made immediately available to public health and government decision-makers and even the public, enabling evidence-informed decision-making based on local disease dynamics. WBS has since been recognized as a tool of transformative potential, providing near-real-time cost-effective, objective, comprehensive, and inclusive data on the changing prevalence of measured analytes across space and time in populations. However, as a consequence of rapid innovation from hundreds of teams simultaneously, tremendous heterogeneity currently exists in the SARS-CoV-2 WBS literature. This manuscript provides a state-of-the-art review of WBS as established with SARS-CoV-2 and details the current work underway expanding its scope to other infectious disease targets.

Economic and Environmental Assessment of a Novel Integrated Three-Column Extractive Distillation Process for Recycling Organics from Wastewater

For diluted wastewater with azeotropes discharged from chemical plants, it is important to design a sustainable extractive distillation process to achieve efficient separation. By separating the dilute wastewater containing isopropanol and acetonitrile, it is proved that the four-column extractive distillation processes with a preconcentration column and a novel three-column process containing an integrated column with preconcentration and solvent recovery function can achieve energy conservation and cost reduction. At the same time, heat integration and heat pump-assisted technologies were further used to intensify the proposed processes. The proposed processes are evaluated in terms of economy, energy consumption, and CO2 emissions. The results display that the double heat pump-assisted extractive distillation process can obtain 75.10% energy saving and the heat integration of the extractive distillation process with a preheater can save 69.45% cost, compared with the conventional extractive distillation process.

Effects of wastewater pre-treatment on clogging of an intermittent sand filter

Intermittent sand filters (ISFs) are widely used in rural areas to treat domestic and dilute agricultural wastewater due to their simplicity, efficacy and relative low cost. However, filter clogging reduces their operational lifetime and sustainability. To reduce the potential of filter clogging, this study examined pre-treatment of dairy wastewater (DWW) by coagulation with ferric chloride (FeCl3) prior to treatment in replicated, pilot-scale ISFs. Over the study duration and at the end of the study, the extent of clogging across hybrid coagulation-ISFs was quantified, and the results were compared to ISFs treating raw DWW without a coagulation pre-treatment, but otherwise operated under the same conditions. During operation, ISFs receiving raw DWW recorded higher volumetric moisture content (θv) than ISFs treating pre-treated DWW, which indicated that biomass growth and clogging rate was higher in ISFs treating raw DWW, which were fully clogged after 280 days of operation. The hybrid coagulation-ISFs remained fully operational until the end of the study. Examination of the field-saturated hydraulic conductivity (Kfs) showed that ISFs treating raw DWW lost approximately 85 % of their infiltration capacity in the uppermost layer due to biomass build-up versus 40 % loss for hybrid coagulation-ISFs. Furthermore, loss on ignition (LOI) results indicated that conventional ISFs developed five times the organic matter (OM) in the uppermost layer compared to ISFs treating pre-treated DWW. Similar trends were observed for phosphorus, nitrogen and sulphur, where proportionally higher values were observed for raw DWW ISFs than pre-treated DWW ISFs, with values decreasing with depth. Scanning electron microscopy (SEM) showed a clogging biofilm layer on the surface of raw DWW ISFs, while pre-treated ISFs maintained distinguishable sand grains on the surface. Overall, hybrid coagulation-ISFs are likely to sustain infiltration capacity for a longer period than filters treating raw wastewater; therefore, requiring smaller surface area for treatment and minimal maintenance.

Making waves: Why do we need ultra-permeable nanofiltration membranes for water treatment?

Over the last few decades, developing ultra-permeable nanofiltration (UPNF) membranes has been a focus research area to support NF-based water treatment. Nevertheless, there have been ongoing debates and doubts on the need for UPNF membranes. In this work, we share our perspectives on why UPNF membranes are desired for water treatment. We analyze the specific energy consumption (SEC) of NF processes under various application scenarios, which reveals the potential of UPNF membranes for reducing SEC by 1/3 to 2/3 depending on the prevailing transmembrane osmotic pressure difference. Furthermore, UPNF membranes could potentially enable new process opportunities. Vacuum-driven submerged NF-modules could be retrofitted to existing water/wastewater treatment plants, offering lower SEC and lower cost compared to conventional NF systems. Their use in submerged membrane bioreactors (NF-MBR) can recycle wastewater into high-quality permeate water, which enables energy-efficient water reuse in a single treatment step. The ability for retaining soluble organics may further extend the application of NF-MBR for anaerobic treatment of dilute municipal wastewater. Critical analysis of membrane development reveals huge rooms for UPNF membranes to attain improved selectivity and antifouling performance. Our perspective paper offers important insights for the future development of NF-based water treatment technology, which could potentially lead to a paradigm shift in this burgeoning field.

Lowering pH enables duckweed (Lemna minor L.) growth on toxic concentrations of high-nutrient agricultural wastewater

The use of duckweed species to remediate nutrient-rich wastewater has grown as a field of research and in industry; however, the need to dilute wastewater to the low ammoniacal-N concentrations tolerated by duckweed represents a barrier to commercially implementing these systems in agriculture. This study investigated the potential for acidifying anaerobically digested cattle slurry (digestate), shifting the NH4+:NH3 equilibrium towards the less toxic ionised form, thus allowing the growth of Lemna minor on less dilute wastewater. First, a study was conducted to identify the ammoniacal-N concentrations tolerated by L. minor and to confirm the positive effect of lower pH on growth in high nutrient solutions using modified Hutner's solutions at two pH levels (8.2 and 6.5). In Hutner's solution at a pH of 8.2, L. minor growth was highest at the lowest ammoniacal-N concentration of 10 mg L−1 and decreased with increasing concentrations. At a pH of 6.5, L. minor growth remained unaffected with increasing ammoniacal-N up to a concentration of 250 mg L−1. L. minor was then grown in digestate concentrations ranging from 5% (65 mg L−1 ammoniacal-N) to 30% (350 mg L−1 ammoniacal-N), based on its growth in Hutner's solutions. It was hypothesised, that growth would decrease as the digestate concentration increased at pH 8.2, and that acidifying digestate to pH 6.5 would alleviate this effect. On unamended digestate (pH 8.2), L. minor growth was prevented even in the most dilute treatment (5%); however, on acidified digestate (pH 6.5), growth rates remained positive and significantly higher than the unamended controls up to the 20% dilution (239.3 mg L−1 ammoniacal-N). Higher growth rates in the Hutner's solutions compared to digestate, particularly at pH 8.2 where no growth was recorded in digestate, suggest the presence of additional inhibitory factors in complex, high-nutrient wastewaters, and potentially sub-optimal concentrations of some of the nutrients provided in Hutner's solution. Nevertheless, correlation matrix analysis of digestate chemical properties highlighted the importance of acidification, with a strong negative correlation between pH and L. minor growth rate. For the first time, we demonstrate that by lowering pH, L. minor could be grown on dilutions of nutrient-rich agricultural wastewater that were otherwise toxic, and which make it feasible as a nutrient removal method. These findings could have important implications for implementing duckweed-based remediation systems in agriculture, increasing water- and land use efficiency, and thus, their commercial viability.

Wastewater Treatment of Solid Waste Leachate and Production of Proteinaceous Biomass Using Duckweed Vegetation ( Lemna minor )

Tekoğul, H., 2023. Wastewater treatment of solid waste leachate and production of proteinaceous biomass using duckweed vegetation (Lemna minor). Journal of Coastal Research, 39(2), 296–302. Charlotte (North Carolina), ISSN 0749-0208. Phytoremediation provides cost–effective wastewater treatment and recovery of wastewater as rich biomass by aquatic plants and produces bioenergy and various important by-products. This study was carried out to treat solid waste leachate with Lemna minor L. and convert wastewater nutrients into protein-rich biomass by this aquatic plant. To create the experimental setups, L. minor was produced in wastewater at six dilution ratios: 100% (T1), 75% (T2), 50% (T3), 25% (T4), Hoagland medium with Lemna (T5c), and 100% wastewater without Lemna (T6). At the end of the 45-day study,the pH 7.00 (T5c) and 8.81, the protein yield rate (crude protein) in the trial groups was found to be T1 = 40.10%, T2 = 67.53%, T3 = 75.24%, T4 = 42.72%, and T5c = 85.00%. In the study, the T3 group showed the best performance in terms of initial weight, final weight, total biomass, specific growth rate, relative growth rate, and protein ratio in wastewater groups. The highest and lowest removal rates in leachate ranged between 85.40% (T4) and 56.50% (T1) for the NH4 +-N value, 14.20% (T4) and 4.73% (T2) for NO2-N, 16.96% (T4) and 6.53% (T3) for NO3-N, and 23.10% (T3) and 16.08% (T1) for PO4–3-P. The total biomass of the trial groups showed an average 50.55% increase from the baseline level. Although 46% biomass was obtained in the Hoagland medium with vegetative growth, a very high biomass of 61% was obtained in the T3 group of solid waste leachate containing dilute wastewater. As a result, phytoremediation is recommended as a solid option for the management of wastewater resources. This efficiency has shown that aquatic plants can be used in the treatment of wastewater and the obtained high protein biomass can be used in various ways, such as animal feed and bioenergy.

A novel sustainable N recycling process: Upcycling ammonia to ammonium fertilizer from dilute wastewater and simultaneously realizing phenol degradation via a visible solar-driven PECMA system with efficient Ag2S-BiVO4 photoanodes

The selective recovery of NH4+ as N fertilizers from dilution wastewater is a promising but challenging topic. Herein, a novel visible-light driven photo-electrochemical membrane stripping cell (designated “PECMA”) with Ag2S-BiVO4 heterojunction photoanode was proposed to recover ammonium from dilute wastewater, which comprised an anode chamber for organics treatment, intermediate chamber for separating ammonium, cathode chamber for upcycling NH4+ into NH3, and recovery chamber for converting NH3 into (NH4)2SO4. The NH4+ is concentrated by 21.5 times and recovered as (NH4)2SO4 with a concentration of 7103 mg L−1 after 10 cycles. At a current density of 3.86 A m−2, PECMA system achieves excellent NH4+ removal and recovery rates of 97.5 and 37.2 g N m−2 d−1 in 100 mgN L−1 wastewater. Moreover, PECMA degrades refractory organic pollutants through ClO· generated by Ag2S-BiVO4 photoanode, which effectively decompose phenol to CO2 with a degradation rate of 93 %. Although tested as a proof-of-concept, the hybrid system opens up a novel field involving a sunlight-water-energy nexus, promising high efficiency NH4+ recovery and wastewater remediation.

Half-wave rectified alternating current electrochemical-assembled devices for high-capacity extraction of Pb2+ from dilute wastewater

The selective capacitive removal (SCR) of toxic but valued lead ions (Pb 2+ ) from dilute wastewater is challenging for water purification since valueless and nontoxic alkali metal ions (like Na + ) often dominate typical metal-containing industrial effluents . Herein, novel devices were assembled based on the half-wave rectified alternating current electrochemical (HWACE) method, and a self-support chitosan-modified carbon felt (Chitosan/ CF ) electrode was constructed to boost the SCR of (Pb 2+ ) from dilute wastewater. The characterization results of the Chitosan/CF electrodes indicated robust mechanical stability, good hydrophilia, and highly capacitive properties owing to the presence of abundant surface functional groups (-NH 2 , –OH). The assembled devices exhibited high extract performances under various conditions. Nearly complete removal of Pb 2+ was achieved in a binary solution containing 50 ppm Pb 2+ and 100 ppm Na + at power supply parameters of the voltage of 5 V, frequency of 600 Hz, and flow rate of 8 mL/min within 24 h with a maximum removal efficiency reaching ∼99.4% and barely changed the concentration of Na + . Here, the fast growth of lead dendrites on the electrode surface was readily visible with naked eyes after 6 h. The characterization data of the Chitosan/CF electrode after HWACE extraction showed the presence of metallic lead (Pb0), suggesting further electroreduction of Pb 2+ into neutral particles after adsorption on the electrode surface. The mechanism taking place at the cathode during the whole HWACE extraction process can best be described by Pb 2+ reduction as the dominant process in early-stage and layered double hydroxide (LDH) precipitation at the late stage. The neutralized lead particles alleviated the Coulombic repulsion for sequent Pb 2+ transformation, instantaneously leading to a nucleation mechanism for the continuous revival of lead particles. As a result, a rather high capacity >2500 mg/g was recorded, outperforming traditional SCR methods. Therefore, the constructed devices provided a new promising way for SCR of Pb 2+ from typical metal-containing wastewater. In addition, the suggested process can be scalable and integrable with dilute wastewater treatment or full resource recovery sewage treatment plant .

Experimental investigation on recovery of bio‐based protocatechuic acid using ionic liquids

AbstractBACKGROUNDThe production of protocatechuic acid (PCA) (which has significant applications in organic intermediates, chemical reagents, pharmaceuticals, dye synthesis, etc.) by fermentation is a potential replacement to the conventional petrochemical routes of carboxylic acid production. However, the extraction processes of these carboxylic acids from fermentation broths and dilute waste water using organic solvents imply additional environment hazards. Ionic liquids (ILs) have come to the focus because of their superior properties as well as environmentally friendly nature, and are being intensively used for separation processes. The equilibrium extraction efficiency for bio PCA using two imidazolium ILs – 1‐butyl‐3‐methylimidazolium tetrafluoroborate (bmimBF4) and 1‐butyl‐3‐methylimidazolium hexafluorophosphate (bmim‐PF6) – was investigated under isothermal conditions in diluent octanol. The distribution coefficient and extraction efficiency were determined to be much greater than those obtained with traditional extractants and diluents.RESULTSThis work is the first of its type to use ILs for PCA isolation. From the equilibrium extraction experiments conducted it was observed, in octanol, that the average distribution coefficients (KD) values for bmimBF4 and bmim‐PF6 were 5.3 and 5.36, respectively, with average extraction efficiencies of 83.84% and 84.08% at a lower IL concentration of 10% by volume, and the findings may be utilised to develop an extraction purification system for PCA separation from aqueous streams. Multiple stages of separation may lead to almost 100% recovery.CONCLUSIONPCA was efficiently extracted from aqueous solutions using bmimBF4 and bmim‐PF6 in octanol, providing preliminary practical information and theoretical support for PCA separation, purification and recovery. © 2022 Society of Chemical Industry (SCI).

Defective Layered Double Hydroxide Nanosheet Boosts Electrocatalytic Hydrodechlorination Reaction on Supported Palladium Nanoparticles

Electrocatalytic hydrodechlorination on Pd, utilizing the H+ of H2O as hydrogen sources, represents a promising technology to detoxify the chlorinated organic pollutants (COPs) in water bodies. However, Pd alone affords limited activity due to its low efficacy in H2O disassociation and the poor mass diffusion of COPs that are commonly of low concentrations in the environment. Herein, we demonstrate that arming Pd with OH– vacancy-bearing NiAl-layered double hydroxide nanosheets (Pd/NixAl100–x-LDH-OHv) can significantly improve its performance, benefiting from the enhanced H2O disassociation at OHv and the facilitated C–Cl cleavage on the supported Pd nanoparticles. Al3+ is also indispensable because it promotes the formation and regeneration of OHv, but an overload will reduce the number of accessible OHv and weaken its function. Pd/Ni67Al33-LDH-OHv with the optimal Ni/Al ratio delivers a peak specific activity of 0.53 min–1 m–2 and mass activity of 6.54 min–1 g–1Pd in treating 50.0 mg L–1 2,4-dichlorophenol (2,4-DCP, a probe COP) at −0.25 V versus RHE, outperforming most of the reported catalysts. To address the mass diffusion issue, Pd/Ni67Al33-LDH-OHv is integrated into a customized continuous-flow membrane cell. When fed a dilute wastewater (20.4 mg L–1), the system affords a 2,4-DCP removal rate of 3.75 g2,4-DCP gcatalyst–1 h–1 and faradaic current efficiency of 42.6%, which is 3.2 and 4.0 times that obtained in a traditional batch reaction system, respectively.

Nitrite reduction using a membrane biofilm reactor (MBfR) in a hypoxic environment with dilute methane under low pressures

Methane-based membrane biofilm reactors (MBfRs) can be an effective solution for nitrogen control in wastewater, but there is limited information on nitrite reduction for dilute wastewater (e.g., municipal wastewater) in hypoxic MBfRs. This study assessed the impacts of dilute (20 %), low-pressure methane (0.35–2.41 kPa) applied to MBfRs at hydraulic retention times (HRTs) of 2–12 h on nitrite removals, dissolved methane concentrations, and the resulting changes in the microbial community. High nitrite flux along with rapid and virtually complete (>99 %) nitrite removals were observed at methane pressures of 1.03–2.41 kPa at HRTs above 4 h, despite the use of diluted methane gas for the MBfR. The lowest methane pressure (0.35 kPa) was also able to achieve up to 98 % nitrite removals but required HRTs of up to 12 h. All scenarios had low dissolved methane concentrations (<10 mg/L), indicating that dilute methane at low supply pressures can effectively remove nitrite while meeting dissolved methane guidelines in treated effluent. Methylococcus genus was the key bacterium in MBfR biofilm grown at different HRTs and methane pressures, along with Methylocystis and other heterotrophic denitrifiers (Terrimonas and Hyphomicrobium). This study indicates that methane-based denitrification MBfRs can be a valuable tool to meet nitrogen limits for dilute wastewater coupled to partial nitrification, while limiting the release of methane to the environment.

Electrocatalytic reduction of nitrate at the stabilizedelectron-deficient Cu&amp;lt;sup&amp;gt;&amp;lt;italic&amp;gt;&amp;delta;&amp;lt;/italic&amp;gt;+&amp;lt;/sup&amp;gt; active sites

<p indent="0mm">With the extensive use of nitrogen fertilizers, sewage discharges and industrial processes that consume nitric acid, the exposure level of nitrate (NO₃⁻-N) in environmental water bodies has significantly increased in the past decades. The NO₃⁻ anion has a stable chemical structure, and is hardly removed by natrual self-cleaning. It has adverse effect, and is primarily responsible for the eutrophication in lakes as well as some physiological diseases in neighboring mammal inhabitants, such as the methemoglobinemia. Strict regulations on the maximum contaminant level of <sc>10 mg/L</sc> for NO₃⁻-N in the drinking water has then been set by the World Health Organization, the United States Environmental Protection Agency and the China Environmental Protection Administration. To minimize the adverse effects of NO₃⁻-N, various technologies, including ion exchange, electrolysis, biological denitrification, and catalytic reduction by H₂ or Fe⁰, have then been developed to eliminate the NO₃⁻-N from water. Among them, electrocatalytic reduction of nitrate (ENRR), driven by the renewable electric energy, is receiving increasing research interests, due to its substantial nitrate removal capacity, mild reaction conditions and minimal daily maintenances. Copper-based materials are favored as the ENRR catalysts by researchers because of their high activity, chemical stability and low cost. The electron-deficient Cu^{<italic>δ</italic>+} is the main active site at the catalyst surface, but it is readily to be reduced to Cu⁰ at the very negative ENRR potentials, leading to the performance deterioration during the long-term reaction process. In this paper, we reported a facile approach to construct the Cu^{<italic>δ</italic>+}-1,4-naphthalene dicarboxylic acid (1,4-NDC) catalytic active sites through the surface decoration of the Cu(OH)₂ particles with the 1,4-NDC molecule at room temperature, followed by an <italic>in-situ</italic> electrochemical activation process under a negative potential of <sc>−0.40 V</sc> vs. RHE (reversible hydrogen electrode, the same below) (the product is denoted as <sc>Cu(OH)₂/1,4-NDC-AT).</sc> In this structure, the Cu^{<italic>δ</italic>+} is confirmed by the X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) to survive under the negative working potential during the long-term ENRR, possibly due to the high electronegativity and chemical stability of the oxygen atoms in carboxyl group (the carboxyl group is chelated with the Cu^{<italic>δ</italic>+} site). The batch ENRR activity test results show that the Cu(OH)₂/1,4-NDC-AT delivers a NH₃ selectivity of &gt;90% in product, a specific activity of <sc>1034.7 mg N/(h m²)</sc> and a mass activity of <sc>89.1 mg N/(h</sc> g_Cu) in treating <sc>22.5 mg/L</sc> NO₃⁻-N solution at <sc>−0.40 V.</sc> The specific and mass activities are nearly 2.3 and 5.1 times those achieved by the ligand-free Cu(OH)-AT, respectively, and also higher than that of most reported catalysts. Optimizing the 1,4-NDC dosage and working potential can further improve the ENRR performance, and the mass activity increases to 147.1 and <sc>104.6 mg N/(h</sc> g_Cu) at the <inline-formula id="INLINE13"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub other="0"><mml:mi other="0">n</mml:mi><mml:mrow other="1"><mml:mtext other="1">1</mml:mtext><mml:mo other="1">,</mml:mo><mml:mtext other="1">4-NDC</mml:mtext></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:msub other="0"><mml:mi other="0">n</mml:mi><mml:mrow other="1"><mml:mtext other="1">Cu</mml:mtext><mml:msub other="1"><mml:mrow other="1"><mml:mrow other="1"><mml:mo other="1">(</mml:mo><mml:mrow other="1"><mml:mtext other="1">OH</mml:mtext></mml:mrow><mml:mo other="1">)</mml:mo></mml:mrow></mml:mrow><mml:mtext other="2">2</mml:mtext></mml:msub></mml:mrow></mml:msub></mml:mrow></mml:math></inline-formula> of 2.16 and the potential of <sc>−0.50 V,</sc> respectively. Finally, this paper proposed the appratus for the treatment of nitrate wastewater in different concentrations. Specifically, an integrated “ENRR+NH₃-N adsorption” technology is proposed to deal with the dilute nitrate wastewater, which enables the elimination of the nitrogen-containing species in water. For the concentrated nitrate wastewater, an integrated “ENRR+NH₃-N recovery” technology is proposed, which can recover 98.0% of the produced NH₃-N via absorption by H₂SO₄ aqueous solution. This work provides new strategies and robust materials specific for NO₃⁻-N removal, which should advance the development of ENRR technology in water pollution remediation.

Wastewater-Based SARS-CoV-2 Surveillance in Northern New England.

ABSTRACTSARS-CoV-2 viral RNA is shed in the stool of 55–70% of infected individuals and can be detected in community wastewater up to 7 days before people present with COVID-19 symptoms. The detection of SARS-CoV-2 RNA in wastewater may serve as a lead indicator of increased community transmission. Here, we monitored viral concentrations in samples collected from nine municipal wastewater facilities in New Hampshire (NH) and Vermont (VT).Twenty-four-h composite primary influent wastewater samples were collected from nine municipal wastewater treatment facilities twice per week for 5 months (late September 2020 to early February 2021). Wastewater was centrifuged for 30 min at 4600 × g, then the supernatant was frozen until further analysis. Once thawed, samples were concentrated, extracted, and tested for SARS-CoV-2 RNA using reverse transcriptase-quantitative PCR (RT-qPCR) and reverse transcriptase-droplet digital PCR (RT-ddPCR) detection methods. Active case counts for each municipality were tracked from the NH and VT state COVID-19 dashboards. We received a total of 283 wastewater samples from all sites during the study period. Viral RNA was detected in 175/283 (61.8%) samples using RT-qPCR and in 195/283 (68.9%) samples using RT-ddPCR. All nine sites showed positivity in the wastewater, with 8/9 (88.8%) sites having over 50% of their samples test positive over the course of the study. Larger municipalities, such as Nashua, Concord, and Lebanon, NH, showed that SARS-CoV-2 positivity in the wastewater can precede spikes in active COVID-19 case counts by as much as 7 days. Smaller municipalities, such as Woodsville, NH and Hartford, VT, showed sporadic SARS-COV-2 detection and did not always precede a rise in active case counts. We detected SARS-CoV-2 RNA in samples from all 9 municipalities tested, including cities and small towns within this region, and showed wastewater positivity as an early indicator of active case count increases in some regions. Some of the smaller rural municipalities with low case counts may require more frequent sampling to detect SARS-CoV-2 in wastewater before a case surge. With timely collection and analysis of wastewater samples, a community could potentially respond to results by increasing public health initiatives, such as tightening mask mandates and banning large indoor gatherings, to mitigate community transmission of SARS-CoV-2.IMPORTANCE Despite vaccination efforts, the delta and omicron variants of SARS-CoV-2 have caused global surges of COVID-19. As the COVID-19 pandemic continues, it is important to find new ways of tracking early signs of SARS-CoV-2 outbreaks. The manuscript outlines how to collect wastewater from treatment facilities, concentrate the virus in a dilute wastewater sample, and detect it using two sensitive PCR-based methods. It also describes important trends in SARS-CoV-2 concentration in wastewater of a rural region of the United States from Fall 2020 – Winter 2021 and demonstrates the utility of wastewater monitoring as a leading indicator of active SARS-CoV-2 cases. Monitoring changes in concentration of SARS-CoV-2 virus in wastewater may offer an early indicator of increased case counts and enable appropriate public health actions to be taken.

Evaluating oil removal by amphiphilic MoS2/cellulose acetate fibrous sponge in a flow-through reactor and by artificial neural network

The amphiphilic Janus-like molybdenum disulfide/cellulose acetate (MoS2/CA) fibrous sponges were synthesized and employed to remove oil from wastewater. The efficiency of treating 100 L of emulsion containing 10 mg/L of oil by MoS2/CA fibrous sponge in a one-pass flow-through reactor was examined under different flow rates, pH, and temperature conditions. The oil concentrations in the treated effluent were all below the industrial discharge requirement of 5 mg/L. The spent sponges were successfully regenerated and reused in multiple cycles. It was found that the adsorption of oil followed the Langmuir adsorption isotherm (R2 = 0.988) and pseudo-second-order kinetic (R2 = 0.995). The hydrophobic/oleophilic MoS2 component of the MoS2/CA sponges was responsible for oil removal while its hydrophilic CA component allowed the material to be stable in the water. Artificial neural networking (ANN) was developed to optimize oil removal. The trained ANN was used to predict the oil removal of two new conditions. This study proved that our Janus-like MoS2/CA sponge was both surfaces active and amphiphilic so can reach the targeted oil droplets in water. These findings provided the basis for the development of an efficient material that can treat large volumes of dilute oil-containing wastewater for water reuse.