Water Environment Research最新文献

This study aims to investigate the response mechanisms of groundwater microbial-toxicological indicators, specifically total bacteria count (TBC) and total coliform count (TCC), to water quality indicators and environmental conditions. Using data from a water source in the western plateau of China, a predictive model focusing on TBC and TCC was developed. An orthogonal experimental design was employed to manipulate environmental conditions such as temperature, pH, and porosity, facilitating laboratory experiments. These experiments measured pH, chemical oxygen demand (COD), oxidation-reduction potential (ORP), TBC, and TCC at varying depths and environmental conditions. Principal component analysis elucidated the mechanisms by which water quality indicators and environmental conditions affect groundwater microbial-toxicological indicators. A prediction model for these indicators in plateau regions was established based on a backpropagation neural network (BP-NN), using TBC and TCC as target variables and the newly extracted principal components as influencing factors. The results demonstrate that environmental conditions and water quality indicators primarily influence the evolution of groundwater microbial-toxicological indicators by altering the ionic charge quantities, redox conditions, and temperature of the groundwater. The predictive model for groundwater microbial-toxicological indicators shows trends consistent with experimental outcomes, with an average relative error of less than 15%, meeting engineering requirements. PRACTITIONER POINTS: The values of total bacteria count (TBC) and total coliform count (TCC) under different conditions were obtained by column experiments. The influence mechanism of environmental conditions and groundwater indicators on TBC and TCC was elaborated by principal component analysis. TBC and TCC prediction models were established through the investigation of water sources in a plateau area and laboratory experiments.

In this study, the treatment of vegetable oil refinery plant condensate effluent (VORCE) having high total suspended solids (TSS) and chemical oxygen demand (COD) generated from acid oil unit was focused. The utilization of waste Brassica nigra meal (BNM) as protein flocculant in treating VORCE was explored. The B. nigra meal flocculant (BNMF) exhibited a crystalline nature, with the presence of amino and carboxyl functional groups, rendering it highly efficient (89.69% efficiency) in floc formation. Zeta potential and particle size (-5.6 mV and 240.68 nm, respectively) indicate BNMF's effectiveness in initiating floc formation. The interactive effects of pH, dosage, settling time on COD, and TSS removal were investigated using the Box-Behnken design. At an optimal pH of 6.9 and BNMF dosage of 0.77 g/L, a maximum removal of 85.38% COD and 72.56% TSS was obtained. The perikinetic theory for the coagulation-flocculation followed a second-order rate reaction with high K_c (0.0001 L/mg min), low settling time (37.04 min), and high collision efficiency (2.703 × 10¹⁷), indicating the model's significance in achieving maximum COD and TSS removal. These findings highlight the potential use of BNMF in the treatment of VORCE, leading to circular economy by valorizing waste from mustard oil extraction and zero discharge. PRACTITIONER POINTS: Valorization of waste Brassica nigra meal (BNM) as a potent protein flocculant Optimization for vegetable oil refinery condensate effluent (VORCE) treatment was done. Interactive effects of the process parameters were analyzed using Design expert. Perikinetic theory for VORCE treatment follows second-order reaction rate with high K_c.

Anaerobic treatment of industrial wastewater using upflow anaerobic reactors is an extended trend due to its high efficiency and biogas production potential, but its implementation in some sectors is limited due to the complexity and toxicity of the wastewaters. In this study, a two-stage expanded granular sludge bed (EGSB) reactors system has been investigated at both bench and pilot scale for the treatment of complex and toxic real wastewater from a petrochemical industry. The effect of different operational parameters including organic loading rate (OLR), hydraulic retention time (HRT) and influent characteristics over COD removal and biogas production and composition have been studied. Additionally, biomass specific methanogenic activity (SMA) and wastewater toxicity have been evaluated after long-term operation. Optimum total HRT of 24 h has been determined resulting in total COD and SO₄ ^2- removal of 56.30 ± 5.25% and 31.68 ± 14.71%, respectively, at pilot scale, and average biogas production of 93.47 ± 34.92 NL/day with 67.01 ± 10.23 %CH₄ content and 5210.11 ± 6802.27 ppmv of H₂S. SMA and toxicity tests have confirmed inhibitory and toxic effects of wastewater over anaerobic biomass with average maximum inhibition of 65.34% in the unacclimated anaerobic inoculum while chronic toxicity produced a decrease of an order of magnitude in SMA after 600 days of operation. This study demonstrates the feasibility of applying an anaerobic treatment to this wastewater using EGSB reactors between a 0.97-1.74 gCOD/L/day OLR range. Nonetheless, periodic reinoculation would be necessary for long-term operation due to chronic toxicity of the wastewater exerted on the anaerobic biomass. PRACTITIONER POINTS: A two-stage EGSB reactors system has been operated at bench and pilot scale to treat complex and toxic petrochemical wastewater. Optimal total HRT of 24 h resulted in average COD removal ranging from 40% to 60%. SMA and toxicity tests have been performed to study long-term acclimation, detecting an activity depletion of an order of magnitude.

Because of its low-lying location, urbanization, and inadequate infrastructure, Jakarta (Indonesia) has experienced an increase in annual flooding events, rising from an average of five significant floods per year in the 1990s to over 20 annually (2010-2020). With climate change exacerbating extreme weather events, Jakarta encounters escalating risks of flooding. Although the recurrent flooding is exacerbated by non-point source (NPS) of pollution such as urban runoff and agricultural discharge that contribute to 40% of total pollutants leading to flood-related issues in Jakarta, none has investigated this research gap. To reflect its novelty, this work explores the implications of climate change on the annual flooding in Jakarta by focusing on NPS and analyzes their impacts from social perspectives. This work also underscores the implications of flooding on livelihoods, health, and social cohesion in Jakarta. Focus group discussion with affected residents was used to shed light on the coping strategies employed in response to recurrent floods, ranging from community-based initiatives to reliance on informal networks. The empirical findings show that the implications of flooding extend beyond physical damages. Displacement of communities, loss of livelihoods, disruption of essential services, and increased health risks are among the social impacts experienced by local residents. Vulnerable populations, including low-income communities residing in informal settlements, bear their consequences. Economic losses from flooding amount to USD 500 million annually, impacting over 1 million residents. However, recent interventions have led to a 15% reduction in peak flood levels and a 20% reduction in flood duration in affected areas. Community resilience has also improved, with a 25% increase in flood insurance coverage and a 20% rise in community response initiatives. Overall, this study highlights that climate change exacerbates annual flooding in Jakarta, significantly impacting vulnerable communities through NPS pollution. Addressing the challenges requires integrated approaches combining effective pollution control, resilient infrastructure, and community engagement to mitigate social and long-term environmental impacts. PRACTITIONER POINTS: Climate-induced flooding disproportionately affects vulnerable communities in Jakarta. Non-point source pollution from urban runoff contributes to the severity of flooding in Jakarta. Waterborne diseases, disruption of livelihoods, and reduced access to clean water are major concerns identified in the study. The study highlights the importance of community-based adaptation strategies to mitigate the impact of flooding and pollution.

Root channel wetlands, as a new type of nature-imitating wetland system, provide a paradigm for micro-polluted water source purification; however, there is a knowledge gap on root channel wetlands' pollution removal effects and their main influencing factors after longtime operation. This study collected the turbidity, ammonia nitrogen (NH₃-N), total nitrogen (TN), total phosphorus (TP), permanganate index (COD_Mn), dissolved oxygen (DO), and chemical oxygen demand (COD) at the inlet and outlet of Shijiuyang (SJY) wetland and Guanjinggang (GJG) wetland in Jiaxing City, China, from 2019 to 2021. The results showed that root channel wetlands had better water quality improvement effects. The SJY wetland had larger removal rates for DO, COD_Mn, and turbidity compared with the GJG wetland. In contrast, other water quality indexes have similar removal rates at both wetlands. The influencing factor analysis showed that water purification agent, flow, pH, and water temperature have large influences on the removal rates of pollutants for both wetlands. To address high turbidity and excessive DO, which are the primary pollutants affecting the two wetlands, implementing the diversion river before the pretreatment area and incorporating ecological floating beds in the deep purification area are recommended solutions to mitigate these issues. Compared with conventional general constructed wetlands, root channel wetlands are a more cost-effective and sustainable technology. The research is conducive to improving understanding of root channel wetland purification for micro-polluted water sources and enhancing water supply security capability in the plains water network area of the Yangtze River Delta region. PRACTITIONER POINTS: Compared with conventional general constructed wetlands, root channel wetlands are more cost-effective and sustainable technology. The SJY wetland demonstrated better removal rates for DO, CODMn, and turbidity, indicating a higher purification capacity compared to GJG wetland. Flow rate and pH are the primary factors influencing the GJG wetland, while the waterpurification agent and water temperature are the main factors affecting water quality in the SJY wetland.

Microplastics (MPs), or tiny pieces of plastic, have become a major global environmental problem because of their ubiquitous availability and possible risks to aquatic ecosystems. Surma is one of the vital rivers in Bangladesh located in the northeast part, with higher chances of MP pollution due to different anthropogenic reasons. In this instance, we carried out the investigation on the abundance, distribution, and characteristics of MPs in the sediment and surface water of the river. Samples were collected from 15 major locations of the Surma river flowing through Sylhet municipality. MPs particles were isolated from sediments and water samples utilizing techniques like sieve analysis, wet peroxide oxidation, density separation, and filtration and then characterized using a stereomicroscope. The abundance of MPs recorded 8 to 18 items/L in water samples (mean ± SD: 12.33 ± 2.98 items/L) and 360 to 1120 items/kg in sediment samples (mean ± SD: 522.67 ± 197.84 items/kg). The prominent size, shape, and color of MPs isolated from sediments were 1-2 mm sizes (24.49%), fragments (47.71%), and black (30.65%). However, for water samples, 1-2 mm sizes (37.22%), fiber shapes (48.48%), and transparent colors (38.46%) were dominant features. Conspicuously, in both sediment and water samples, there was a higher prevalence of smaller sized particles, posing a significant threat to the ecosystem. This heightened risk stems from the increased likelihood of ingestion by microorganisms, as well as the larger surface area of these particles, which may serve as vectors for other pollutants like organic pollutants and heavy metals. A greater abundance of fibers suggests an increased presence of lightweight particles in the water and sediment. Furthermore, the transparent color of the MPs in water might be impacted by prolonged weathering in the river, while the presence of black-colored MPs in sediment points to the existence of plastic pellets originating from industrial and diverse sources. Future studies should concentrate on long-term and broad monitoring, ecological effects, and practical mitigation techniques for MPs, providing essential baseline data to guide the formulation of policies in developing nations. PRACTITIONER POINTS: 12.33 items/L in surface water and 522.67 items/kg in sediment were observed. High correlation indicates a single MP source in mainstream water, differing from sediment. Fiber shapes, black, and transparent colored MPs are dominant. Higher prevalence of smaller sized MPs, posing a significant threat to the aquatic ecosystem.

Watershed models of plastic export from rivers to oceans have large uncertainties, and improvements require direct measurements of riverine macroplastic (>5 mm) and microplastic (<5 mm). Also, plastic represents allochthonous carbon inputs to rivers but is rarely measured as carbon mass. We quantified plastic and organic matter within floating debris rafts and open water in an urban river. Macroplastics only occurred in debris rafts. Microplastics had higher concentrations in debris rafts relative to open water. Across sites, organic matter was positively correlated with microplastics and macroplastics. Last, carbon in plastic was 40% of the carbon mass in coarse particulate organic matter in debris rafts. Floating plastic litter accumulates with particulate organic matter in debris rafts. Plastic is an overlooked and ecological meaningful component of carbon standing stocks in urban rivers. Results will inform improved carbon budget calculation in rivers and watershed models of plastic export. PRACTITIONER POINTS: Plastic particles floating on the surface of an urban river accumulate in debris rafts compared to open water in terms of count and mass. Abundance and composition of plastic particles in debris rafts were distinct from those in open water areas. Plastic litter as units of carbon mass was in the same order of magnitude as carbon mass in course particulate organic matter. Plastic litter moves in similar ways to naturally occurring organic particles and should be measured as a part of the riverine carbon cycle.

In this study, the siphon-type composite vertical flow constructed wetland (Sc-VSsFCW) was constructed with anthracite and shale ceramsite chosen as the substrate bed materials. During the 90-day experiment, typical pollutant removal effects of wastewater and extracellular polymeric substance (EPS) accumulation were investigated. Meanwhile, X-ray diffraction and scanning electron microscopy were used to examine the phase composition and surface morphology to analyze adsorptive property. Additionally, we evaluated the impact of siphon effluent on clogging and depolymerization by measuring the EPS components' evolution within the system. The findings reveal that both the anthracite and shale ceramsite systems exhibit impressive removal efficiencies for total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), chemical oxygen demand (COD), ammonium nitrogen (NH₄ ⁺-N), and nitrate nitrogen (NO₃ ^--N). However, as the experiment progressed, TP removal rates in both systems gradually declined because of the saturation of adsorption sites on the substrate surfaces. Although the dissolved oxygen (DO) levels remained relatively stable throughout the experiment, pH exhibited distinct patterns, suggesting that the anthracite system relies primarily on chemical adsorption, whereas the shale ceramsite system predominantly utilizes physical adsorption. After an initial period of fluctuation, the permeability coefficient and porosity of the system gradually stabilized, and the protein and polysaccharide contents in both systems exhibited a downward trend. The study underscores that anthracite and shale ceramsite have good effectiveness in pollutant removal as substrate materials. Overall, the hydraulic conditions of the double repeated oxygen coupling siphon in the Sc-VSsFCW system contribute to enhanced re-oxygenation capacity and permeability coefficient during operation. The changes in EPS content indicate that the siphon effluent exerts a certain depolymerization effect on the EPS within the system, thereby mitigating the risk of biological clogging to a certain extent. PRACTITIONER POINTS: The system can still maintain good pollutant treatment effect in long-term operation. The re-oxygenation method of the system can achieve efficient and long-term re-oxygenation effect. The siphon effluent has a certain improvement effect on the permeability coefficient and porosity, but it cannot effectively inhibit the occurrence of clogging. The EPS content did not change significantly during the operation of the system, and there was a risk of biological clogging.

When an artificial structure is built in a river, the river changes significantly in water quality and hydraulic properties. In this study, the effects of the weirs constructed in the middle section of a river as a four major rivers restoration project in Korea on water quality and hydrological characteristics were analyzed. For multi-dimensional data analysis, a self-organizing map was applied, and statistical techniques including analysis of variation were used. As a result of analysis, the cross-sectional area of the river increased significantly after the construction of the weir compared to before the construction of the weir, and the flow velocity decreased at a statistically significant level. In the case of water quality, nitrogen, phosphorus, and suspended solids tended to improve after weir construction, and chlorophyll-a and bacteria tended to deteriorate. Some water quality parameters such as chlorophyll-a were also affected by seasonal influences. In order to improve the water quality deteriorated by the construction of the weir, it is necessary to consider how to improve the flow velocity of the river through partial opening or operation of the weir. In addition, in order to determine the effect of sedimentation of particulate matter due to the decrease in flow rate, it is necessary to conduct investigations on sediments around weirs in the future. PRACTITIONER POINTS: Compared to before the construction of the weir, there was no significant change in the flow rate of the river after the construction of the weir. In the case of chlorophyll-a and bacteria, the water quality was deteriorated after weir construction. To improve the deteriorated water quality, it is required to consider the fundamental management of each pollutant source and the flexible operation of both weirs. For some improved water quality parameters, further research is needed to determine whether these improvements are directly attributable to the construction of a weir.