Concentrated Wastewater Research Articles

Assessment of Natural Bentonite Efficacy for Dye Removal in Textile Wastewater Treatment : Implication for Mitigating River Citarum Pollution

Textile industries contribute significantly to the economy but release harmful pollutants into the environment, especially rivers. The effluent from the textile industry contained toxic dyes that can harm the river ecosystem. Several studies have been conducted to reduce toxic dyes in a river system using bentonite as an adsorbent to reduce river pollution effectively. However, the effectiveness of bentonite still needs to be tested again using textile liquid waste that has not gone through any waste processing at all. Citarum is one of the main rivers on Java Island, which suffers from textile effluent, especially azo dyes which are toxic, mutagenic and carcinogenic which can harm the aquatic ecosystem. Therefore, this study aims to implement natural bentonite as an adsorbent to remove dyes from textile wastewater. We performed a laboratory test to adsorption on bentonite and textile wastewater considering the variation of adsorbent weight of 10 g and 20 g in 100 mL of textile wastewater stirred in an Erlenmeyer flask at room temperature for 0-300 minutes. The initial concentration of textile wastewater used was 10%, 30%, and 50%. We found that the maximum dye removal efficiency was 91.25% with 10% initial concentration treatment, 20 g adsorbent weight, and 60 minutes contact time. Longer contact time will increase the removal efficiency and adsorption capacity, while higher adsorbent dosage will decrease the concentration of dyes in wastewater. Efficient textile wastewater treatment has improved water quality, effectively meeting river water quality standards and environmental regulations.

Enhanced water permeability and antifouling properties of cross-linked graphene oxide composite membranes with tunable d-spacings

Low flux and membrane fouling are major challenges in membrane distillation (MD) for treating concentrated wastewater. This study compared the performance of GO composite membranes with different interlayer distances, by covalently bonding the terminal amine groups of ethylenediamine (EDA) and 1,12-diaminododecane (DADD) with the carboxyl groups present on the GO sheets. The results indicated that the GO-DADD/PTFE membrane, with longer carbon chain cross-linking, achieved the highest flux and antifouling properties. At 70 °C, the pure water flux reached 68.5 kg/m2·h, and the fluxes for treating NaCl, HA containing NaCl, and BSA containing NaCl were 29.8 %, 37.1 %, and 38.5 % higher than the uncrosslinked GO/PTFE, and 95.7 %, 121.2 %, and 146.9 % higher than the PTFE membrane, respectively. Through mathematical models for mass and heat transfer, the study identified the key to this enhancement as the increased d-spacing within the GO layer due to cross-linking, which weakened the Kelvin effect and enhanced the vapor partial pressure on the hot side. The unique surface structure and electrostatic interactions induced by long-chain cross-linking further boosted the antifouling effect. These modifications not only overcome the typical trade-off between retention rates and flux but also offer a scalable and efficient solution for advanced membrane distillation applications.

Impact of dissolved organic nitrogen (DON) to the formation of disinfection byproducts (DBP) during water/wastewater treatment: A review

Disinfection byproduct (DBP) formation during water and wastewater treatment is a concern for public health and environmental preservation. Dissolved organic nitrogen (DON) serves as a recognized precursor to DBP formation, which can potentially jeopardize human health. This review article offers a comprehensive insight into DON's influence on DBP formation during water and wastewater treatment processes. It delves into DON's sources, properties, and concentrations in water and wastewater, underlining the variability dependent on water source and environmental conditions. The mechanisms of DBP formation from DON, encompassing formation pathways and influencing factors, are meticulously examined. Different treatment methods, like chlorination, ozonation, and UV disinfection, are carefully examined to see how they affect the formation of DON and DBP. Factors that sway DON's impact on DBP formation are also explored. The review also presents various DBP reduction techniques, spanning physical, chemical, and biological treatment methods, their efficacy in curtailing DON's influence, and their potential pros and cons. It addresses challenges, outlines future research directions, identifies knowledge gaps, and highlights the necessity for regulatory measures and policies, providing recommendations for prospective research avenues. It is clear from this in-depth review that more research is needed to understand how DON affects the formation of DBP entirely. It is also essential to protect human health and the environment and follow the rules first when treating wastewater. In conclusion, it analyzes DON's part in forming DBP in water and wastewater treatment. This emphasizes the need for ongoing research and mitigation strategies to protect public health and water quality.

Multi-factor normalisation of viral counts from wastewater improves the detection accuracy of viral disease in the community

The detection of viruses (e.g. SARS-CoV-2, norovirus) in wastewater represents an effective way to monitor the prevalence of these pathogens circulating within the community. However, accurate quantification of viral concentrations in wastewater, proportional to human input, is constrained by a range of uncertainties, including (i) dilution within the sewer network, (ii) degradation of viral RNA during wastewater transit, (iii) catchment population and facility use, (iv) efficiency of viral concentration and extraction from wastewater, and (v) inhibition of amplification during the RT-qPCR step. Here, we address these uncertainties by investigating several potential normalisation factors including the concentration of ammonium and orthophosphate. A faecal indicator virus (crAssphage), and the recovery of the process-control viruses (murine norovirus and bacteriophage Phi6), used for quality control during the RT-qPCR step, were also considered. We found that multi-factor normalisation of SARS-CoV-2 RT-qPCR data was optimal using a combination of crAssphage, process-control virus recovery, and concentration efficiency to improve prediction accuracy relative to clinical test data. Using multi-normalised SARS-CoV-2 RT-qPCR data, we found a lasso regression model with random forest modelled residuals lowers the prediction error of positives by 46 %, compared to a single linear regression using raw data. This multi-normalised approach enables more accurate wastewater-based predictions of clinical cases up to five days in advance of clinical data, identifying trends in disease prevalence before clinical testing, and demonstrates the potential to improve viral pathogen detection for a range of currently monitored and emerging diseases.

The treatment of high concentration wastewater in the natural gas processing industry.

The operation of the Cansolv tail gas treatment device in natural gas plants generates acidic and alkaline wastewater from the venturi unit and amine purification unit (APU), respectively. The APU wastewater is complex in composition and contains hard-to-degrade organic matter, which can adversely impact the normal functioning of the water treatment system. This study assesses the efficacy of three ozone-based advanced oxidation processes (ozone (O3), ozone/hydrogen peroxide (O3/H2O2), and ozone/Fenton (O3/Fenton)) for treating Cansolv wastewater, with chemical oxygen demand (COD) and total organic carbon (TOC) serving as indicators of organic degradation. The findings demonstrate that all three processes effectively eliminate coloration and reducible sulfur, with O3/Fenton exhibiting superior performance in removing organic substances. The treated wastewater has a clarified light-yellow appearance with residual COD levels at 43 mg L-1. Under the optimum Fenton oxidation conditions (initial pH 5, H2O2 dosage 97.8 mmol L-1, FeSO4·7H2O dosage 550 mg L-1), average TOC and COD removal rates reached 50% and 97%, respectively. After a treatment duration of 60 minutes, the wastewater demonstrated an enhanced membrane-specific flux, confirming the effectiveness of the O3/Fenton oxidation process in mitigating membrane fouling while ensuring the stable operation of the wastewater treatment system.

National-scale antimicrobial resistance surveillance in wastewater: A comparative analysis of HT qPCR and metagenomic approaches

Wastewater serves as an important reservoir of antimicrobial resistance (AMR), and its surveillance can provide insights into population-level trends in AMR to inform public health policy. This study compared two common high-throughput screening approaches, namely (i) high-throughput quantitative PCR (HT qPCR), targeting 73 antimicrobial resistance genes, and (ii) metagenomic sequencing. Weekly composite samples of wastewater influent were taken from 47 wastewater treatment plants (WWTPs) across Wales, as part of a national AMR surveillance programme, alongside 4 weeks of daily wastewater effluent samples from a large municipal hospital. Metagenomic analysis provided more comprehensive resistome coverage, detecting 545 genes compared to the targeted 73 genes by HT qPCR. It further provided contextual information critical to risk assessment (i.e. potential bacterial hosts). In contrast, HT qPCR exhibited higher sensitivity, quantifying all targeted genes including those of clinical relevance present at low abundance. When limited to the HT qPCR target genes, both methods were able to reflect the spatiotemporal dynamics of the complete metagenomic resistome, distinguishing that of the hospital and the WWTPs. Both approaches revealed correlations between resistome compositional shifts and environmental variables like ammonium wastewater concentration, though differed in their interpretation of some potential influencing factors. Overall, metagenomics provides more comprehensive resistome profiling, while qPCR permits sensitive quantification of genes significant to clinical resistance. We highlight the importance of selecting appropriate methodologies aligned to surveillance aims to guide the development of effective wastewater-based AMR monitoring programmes.

Purification of highly concentrated wastewater from tanneries

Purification of highly concentrated wastewater from tanneries

Algal consortia as the flexible bio-system for wastewater treatment: Effect of different light intensities on photosynthetic performance, anti-oxidative system and biodiesel production of consortia

Competence of microalgae consortia-1 (Chlorococcum humicola and Tetradesmus sp.) and consortia-2 (Chlorococcum humicola, Scenedesmus vacuolatus and Tetradesmus sp.) was analyzed by examining their adaptability potential in wastewater under different light intensities (20 W/m2 and 40 W/m2). The results depicted highest decline in nutrients and metal concentration (40–90%) at light intensity of 40 W/m2 by consortia-1 and consortia-2 treated with wastewater (50%, 100%). The result of metal remediation was further confirmed by fourier transform infrared spectroscopy (FTIR) which reflected occurrence of different functional groups in selected consortia. Moreover, light intensity of 40 W/m2 induced neutral-lipid accumulation (1750 cm−1) in consortia-1 as depicted in FTIR spectra. The maximum active photosystem-II reaction center (79.75%), quantum yield (26.17%) and performance index (195.8%) revealed that light intensity (40 W/m2) and wastewater augmented functioning of photosystem-II in consortia-1 than consortia-2. Further, consortia-2 appeared more sensitive to oxidative stress as the concentration of oxidative stress markers (5.73–6.39 folds) was amplified after treatment with wastewater at light intensity of 40 W/m2. The prodigious tolerance potential towards different light intensities and wastewater concentration of consortia-1 may be attributed to increased activity of ascorbic acid (1.16 folds), proline (1.32 folds), cysteine (2.80 folds), superoxide dismutase (3.44 folds), catalase (2.52 folds) and glutathione reductase (1.90 folds). However, abundance of saturated fatty acid (41.34%) together with high cetane number (59.07) indicated that consortia 2 can produce excellent quality biofuel at 20 W/m2 while consortia-2 at 40 W/m2. Overall, consortia 1 appeared competent in terms of photosynthetic performance, remediation efficiency and antioxidant defense mechanism under 20 W/m2 and 40 W/m2 while consortia-2 showed quality biodiesel production at 20 W/m2. Thus, algal consortia based on photosynthetic performance and defense responses along with excellent biodiesel quality under different light intensity and wastewater concentration can serve as the promising biosystem for biomass and bioenergy production.

A green and economically efficient adsorbent made by longan seed for the treatment of fluoroquinolone antibiotics in water

In this study, a green and economically efficient adsorbent was prepared from discarded longan seed. Hydrochloric acid-modified longan seed biochar (HNSB), as the final product, possesses excellent adsorption properties. BET characterization of HNSB demonstrates impressive porous properties with a specific surface area of 420.58 m2/g. Batch adsorption experiments were conducted with gatifloxacin (GAT), norfloxacin (NOR), and lomefloxacin (LOM) as representatives of typical fluoroquinolone antibiotics (FQs). The adsorption capacity of HNSB for FQs exceeded 40% of that of commercial activated carbon. The sustained effective time of HNSB dynamic adsorption for treating high concentrations of FQs wastewater was more than 20 h. Adsorption kinetics and isotherms were fitted by the pseudo-second-order model and the Langmuir model. The adsorption mechanism includes the pore-filling effect, electrostatic attraction, reduction reaction, hydrogen bonding, π-π interaction, and hydrophobicity. This study provides an economic and feasible strategy for the engineering application of agricultural wastes in pharmaceutical wastewater treatment.

Insights on phytoremediation of chromium from tannery wastewater contaminated soil

The study was conducted to evaluate the phytoremediation response of Arundo donax and vetiver grasses irrigated by different levels (0%, 10%, 25%, 50%, 75%, and 100%) of treated tannery wastewater. After 60 days, matured plants were harvested, sorted into root, leaf, stem and shoot, dried and digested using standard procedures and analyzed for Cr(VI) and total Cr using atomic absorption and UV-Visible spectrophotometer, respectively. Corresponding results revealed height growth of Arundo donax and vetiver grasses was greatly affected by the irrigation level of tannery wastewater. Roots of vetiver grasses accumulate the highest amount of Cr(VI) (2.76 mg/kg) compared to the shoots Cr(VI) 1.72 mg/kg. Lowering concentration of tannery wastewater used for irrigation to 10% boosted the accumulation capacity (3.99 mg/kg) of the root of Arundo donax grasses for Cr(VI). The translocation values (TF > 1) demonstrated favourability of Arundo donax grasses for phytoextraction of Cr(VI) to plant tissues above ground level. However, the bioaccumulation values (BAF > 1) of the root of vetiver grasses proved suitability for the phytostabilisation of Cr(VI). Arundo donax and vetiver grasses have demonstrated a substantial reduction in Cr contamination of soils from tanneries, and therefore, phytoremediation is potentially feasible for the decontamination of Cr-polluted environments.

Incorporation of copper ion promoted adsorption of anionic dye (Acid Yellow 36) by acrolein-crosslinked polyethyleneimine/chitosan hydrogel: Adsorption, dynamics, and mechanisms

In this study, a novel adsorbent, A-PEI/CS-Cu2+, was developed by crosslinking polyethyleneimine/chitosan hydrogel with acrolein and loading it with copper ions. The adsorption process of A-PEI/CS-Cu2+ on the anionic dye acid yellow 36 (AY36) was investigated by kinetic, isothermal and thermodynamic modeling. It was noteworthy that A-PEI/CS-Cu2+ exhibited rapid adsorption with a 90 % removal rate achieved within just 5 min, which was much faster than the adsorption rate of A-PEI/CS without load of copper ions and showed its potential for rapid adsorption applications. The maximum adsorption capacity for AY36 could reach up to 3114 mg g−1. In addition, the high concentration of saline wastewater was found to have almost no effect on the adsorption reaction in the salt effect test experiment. In five desorption-regeneration cycle experiments, the sample exhibited good recyclability and regeneration performance. The driving force of the adsorption process mainly originated from the electrostatic interaction, hydrogen bonding, and intermolecular interaction, in which the addition of copper ions led to the enhancement of the electrostatic interaction and chelation between A-PEI/CS-Cu2+ and AY36. Overall, the findings suggest the excellent potential of A-PEI/CS-Cu2+ for rapid and efficient adsorption, as well as its suitability for practical applications in wastewater treatment.

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.

Optimizing coolant oil wastewater treatment via modified air-Fenton process with bimetallic particles from auto parts manufacturing waste

This study evaluated the efficiency of aluminium (Al)/iron (Fe) bimetallic particles, produced from waste by-products of auto parts manufacturing—namely, aluminum dross (AD) and shot blast (SB)—in removing chemical oxygen demand (COD) and total organic carbon (TOC) from coolant oil wastewater originating from an auto parts manufacturer. Two different molar ratios of ADSB bimetallic particles, namely, 1:1 (ADSB1) and 2:1 (ADSB2), were investigated for their characteristics and applied in the modified air-Fenton (MAF) process which enhances the traditional Fenton method by utilizing ADSB bimetallic particles instead of Fe0 and Al0, and by incorporating aeration to stimulate the reaction. The wastewater contained an initial COD ranging from 60,000 to 120,000 mg L–1 (at 3–5 % v/v) and a TOC ranging from 10,000 to 40,000 mg L−1. The experimental design included varying reaction times, pH values, quantities of bimetallic particles, airflow rates, and wastewater concentrations were performed using the Minitab-19 software package. X-ray fluorescence (XRF) analysis revealed that the bimetallic particles have SiO2 content ranging from 39.69 % to 56.03 %, Fe2O3 ranging from 20.52 % to 30.90 % and Al2O3 ranging from 16.51 % to 16.66 %, with surface areas varying between 5 and 6 m2 g−1. As a result of XRF analysis, SiO2 can be contaminated by the sand molds used in the manufacturing process of products. Notably, ADSB1 exhibited impressive removal efficiencies of 98.70 % and 98.50 % for COD and TOC, respectively, at 0.6 g, pH 3, airflow rate of 1.5 L min–1, and reaction time of 105 min. Conversely, ADSB2 achieved removal efficiencies of 96.30 % and 98.43 % for COD and TOC, respectively, at 0.2 g, pH 9, airflow rate of 2.0 L min–1, and reaction time of 180 min. Pareto charts and 3D surface plots derived from the data showed the number of bimetallic particles as the most influential factor, followed by the initial pH. The MAF process significantly extends the pH range under diverse conditions by incorporating ADSB particles and reduces the reliance on traditional chemicals like hydrogen peroxide. This research presents a promising advancement in wastewater treatment technology.

Wastewater threshold as an indicator of COVID-19 cases in correctional facilities for public health response: A modeling study

Although prison facilities are not fully isolated from the communities in which they are located, most of the population is confined and requires high levels of health vigilance and protection. This study aimed to examine the dynamic relationship between facility-level wastewater viral concentrations and the probability of at least one positive COVID-19 case within the facility. The study period was from January 11, 2021 to May 8, 2023. Wastewater samples were collected and analyzed for SARS-CoV-2 (N1) and pepper mild mottle virus (PMMoV) three times weekly across 14 prison facilities in Kentucky (USA). Positive clinical case reports were also provided. A hierarchical Bayesian facility-level temporal model with a latent lagged process was developed. We modeled facility-specific SARS-CoV-2 (N1) normalized by the PMMoV wastewater concentration ratio threshold associated with at least one COVID-19 clinical case at an 80 % probability. The threshold differed among facilities. Across the 14 facilities, our model demonstrates a mean capture rate of 94.95 % via the N1/PMMoV ratio threshold with pts≥0.5. However, as the pts threshold was set higher, such as at ≥0.9, the mean capture rate of the model was reduced to 60 %. This robust performance underscores the effectiveness of the model for accurately detecting the presence of positive COVID-19 cases among incarcerated people. The findings of this study provide a facility-specific threshold model for public health response based on frequent wastewater surveillance.

Recovery of an Antioxidant Derived from a Phenolic Diphosphite from Wastewater during the Production of a Polypropylene Compound: A Step towards Sustainable Management.

Organic phosphoester (OPE) antioxidants are currently required due to their contribution to enhancing the quality of polymers, including polypropylene (PP). In this research, an integral methodology is presented for the efficient extraction of bis(2,4-dicumylphenyl) pentaerythritol diphosphite from industrial wastewater. Upon employing the solid-phase extraction (SPE) technique, the recovered compound is subjected to a comprehensive analysis of the recovered compound using high-performance liquid chromatography (HPLC), mass spectrometry (MS), thermal analysis (TGA), Fourier transforms infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Subsequently, purified Bis(2,4-dicumylphenyl) pentaerythritol diphosphite was evaluated as a thermo-oxidative stabilizer after incorporation into PP resins. The relative standard deviation (RSD), Error (Er), linearity (R2), and percentage (%) recovery were less than 2.6, 2.5, more significant than 0.9995, and greater than 96%, respectively, for the inter-day and intra-day tests of the chromatographic method and the SPE. Except for chloroform, which was necessary due to the solubility properties of the investigated analyte, the use of environmentally friendly solvents, such as methanol and acetonitrile, was considered during the development of this research. The OPE extracted from industrial wastewater was characterized by FTIR, UV-Vis, DSC, TGA, and MS, allowing the elucidation of the structure of Bis(2,4-dicumylphenyl) pentaerythritol diphosphite (BDPD). The recovered OPE was mixed with PP resins, allowing it to improve its thermal properties and minimize its thermo-oxidative degradation. Organophosphorus flame retardant (OPE)' concentration in wastewater is alarming, ranging from 1179.0 to 4709.6 mg L-1. These exceed toxicity thresholds for aquatic organisms, emphasizing global environmental risks. Using a validated solid-phase extraction (SPE) technique with over 94% recovery, the study addresses concerns by removing organic contaminants and supporting circular economy principles. The high economic and environmental significance of recovering BDPD underscores the need for urgent global attention and intervention.

Bioremediation of petroleum refinery wastewater using Bacillus subtilis IH-1 and assessment of its toxicity.

Environmental contamination from petroleum refinery operations has increased due to the rapid population growth and modernization of society, necessitating urgent repair. Microbial remediation of petroleum wastewater by prominent bacterial cultures holds promise in circumventing the issue of petroleum-related pollution. Herein, the bacterial culture was isolated from petroleum-contaminated sludge samples for the valorization of polyaromatic hydrocarbons and biodegradation of petroleum wastewater samples. The bacterial strain was screened and identified as Bacillus subtilis IH-1. After six days of incubation, the bacteria had degraded 25.9% of phenanthrene and 20.3% of naphthalene. The treatment of wastewater samples was assessed using physico-chemical and Fourier-transform infrared spectroscopy analysis, which revealed that the level of pollutants was elevated and above the allowed limits. Following bacterial degradation, the reduction in pollution parameters viz. EC (82.7%), BOD (87.0%), COD (80.0%), total phenols (96.3%), oil and grease (79.7%), TKN (68.8%), TOC (96.3%) and TPH (52.4%) were observed. The reduction in pH and heavy metals were also observed after bacterial treatment. V. mungo was used in the phytotoxicity test, which revealed at 50% wastewater concentration the reduction in biomass (30.3%), root length (87.7%), shoot length (93.9%), and seed germination (30.0%) was observed in comparison to control. When A. cepa root tips immersed in varying concentrations of wastewater samples, the mitotic index significantly decreased, suggesting the induction of cytotoxicity. However, following the bacterial treatment, there was a noticeable decrease in phytotoxicity and cytotoxicity. The bacterial culture produces lignin peroxidase enzyme and has the potential to degrade the toxic pollutants of petroleum wastewater. Therefore the bacterium may be immobilised or directly used at reactor scale or pilot scale study to benefit the industry and environmental safety.

Flexible bifunctional wood-derived water filtration/photo-Fenton membrane for efficient purification of mixed organic wastewater

Membrane filtration technology demonstrates excellent continuous processing capability in organic wastewater treated processes, which is usually applied in continuous industrial processes. However, it still faces a contradiction between membrane flux and treatment efficiency. In this study, a flexible wood-based photocatalytic membrane with high membrane flux and exceptional photofenton performance was developed via partial fragment wood components and uniform loading of multi-metal oxide nanocatalysts, which breaks mentioned contradiction. The homogeneous and efficient wood-based dual-function water filtration/photofenton system was established by leveraging the directional porous structure of wood in conjunction with the nanocatalysts while adjusting their ratios, enabling effective purification of highly concentrated mixed organic wastewater. Under one solar intensity and negative pressure filtration (0.03 MPa), the system treated a mixed solution containing Rhodamine B, phenol, and tetracycline at a concentration of 280 mg L−1 with the removal efficiencies of 100 %, 93.4 %, and 90.2 %, respectively, and the membrane flux could up to 315.3 Lm−2 h−1 within one hour. The membrane showed a good recycling performance, and the decay rates were all below 5 % after five cycles. This wood-based dual-function water filtration/photo-Fenton system provides a new approach for the continuous dynamic treatment of high-concentration organic wastewater on an industrial scale.

Microplastics in wastewater and sludge from centralized and decentralized wastewater treatment plants: Effects of treatment systems and microplastic characteristics

Domestic wastewater treatment plants (WWTPs) play a vital role in limiting the release of microplastics (MP) into the environment. This study examined MP removal efficiency from five centralized and four decentralized domestic WWTPs in Bangkok, Thailand. MP concentrations in wastewater and sludge were comparable between centralized and decentralized WWTPs, despite these decentralized WWTPs serving smaller populations and having limited treatment capacity. The elimination of MPs ranged from 50 to 96.8% in centralized WWTPs and 14.2–53.6% in decentralized WWTPs. It is noted that the retained MPs concentrations in sludge ranged from 20,000 to 228,100 MP/kg dry weight. The prevalence of synthetic fibers and fragments could be attributed to their pathways from laundry or car tires, and the accidental release of a variety of plastic wastes ended up in investigated domestic WWTPs. Removal of MPs between the centralized and decentralized WWTPs was influenced by several impact factors including initial MP concentrations, longer retention times, MP fragmentation, and variations of MP concentrations in sludge leading to different activated sludge process configurations. Sewage sludge has become a primary location for the accumulation of incoming microplastics in WWTPs. The MPs entering and leaving each unit process were varied due to the unique characteristics of MPs, and their different treatment efficiencies. While the extended hydraulic retention period in decentralized WWTPs decreased the MP removal efficacy, the centralized WWTP with the two-stage activated sludge process achieved the highest MP removal efficiency.

Public health policy impact evaluation: A potential use case for longitudinal monitoring of viruses in wastewater at small geographic scales

Public health policy impact evaluation is challenging to study because randomized controlled experiments are infeasible to conduct, and policy changes often coincide with non-policy events. Quasi-experiments do not use randomization and can provide useful knowledge for causal inference. Here we demonstrate how longitudinal wastewater monitoring of viruses at a small geographic scale may be used in a quasi-experimental design to evaluate the impact of COVID-19 public health policies on the spread of COVID-19 among a university population. We first evaluated the correlation between incident, reported COVID-19 cases and wastewater SARS-CoV-2 RNA concentrations and observed changes to the correlation over time, likely due to changes in testing requirements and testing options. Using a difference-in-differences approach, we then evaluated the association between university COVID-19 public health policy changes and levels of SARS-CoV-2 RNA concentrations in wastewater. We did not observe changes in SARS-CoV-2 RNA concentrations associated with most policy changes. Policy changes associated with a significant change in campus wastewater SARS-CoV-2 RNA concentrations included changes to face covering recommendations, indoor gathering bans, and routine surveillance testing requirements and availability.

Experimental study on coagulation and adsorption treatment of wastewater in combustion cavity for underground coal gasification

Underground Coal Gasification (UCG) is a promising mineral resource development technology that can transform in-situ coal into combustible gas by controlling combustion. However, wastewater generated during the UCG process can lead to environmental pollution in adjacent areas through diffusion or infiltration. In order to seek an efficient and inexpensive in-situ treatment method for underground gasification combustion zone wastewater, UCG model experiments were conducted to obtain wastewater, and the treatment effects of chemical coagulation and physical adsorption methods were compared in this work. The COD concentration in wastewater from underground combustion zone ranges between 555 ∼ 703 mg/L, with a pH value between 8.26 ∼ 8.85. The organic pollutants mainly come from the dissolution of high carbon components, mainly aromatic compounds in tar, which leads to high toxicity and pollution risk of wastewater. For chemical coagulation method, the removal effect of organic pollutants in combustion zone wastewater by ferric sulfate is better than that of aluminum sulfate due to excellent hydrolysis reaction of Fe3+. The corresponding COD removal rate and COD removal cost are 24.34 % and 0.176 ¥/g, respectively. For physical adsorption method, due to the large total pore volume and wide specific surface area of organic bentonite, it can effectively remove COD content. The COD removal rate and COD removal cost, and COD adsorption capacity are 60.23 %, 0.213 ¥/g, and 89.75 mg/g, respectively. Comprehensive comparison shows that physical adsorption is more suitable for in-situ treatment of combustion zone wastewater.