Polluted River Water Research Articles

Comprehensive review of the environmental impacts of mining and smelting at the Baiyinchang Cu-Zn-Pb ore deposit, Gansu Province, China, with new inputs from the sulfide compositions

This review paper presents an in-depth synthesis of the environmental aspects associated with the mining of the Baiyinchang Cu-Zn-Pb deposit in China. The review covers contamination by atmospheric deposition and sewage irrigation, soil contamination, and ecosystem health to evaluate current environmental conditions, identify potential impacts, and suggest sustainable mitigation measures for the Baiyin district. With a focus on soil, river water, and crop pollution levels, our review indicates that several heavy metals (HMs), particularly Cd, have been gradually accumulated in soils and streams due to the natural occurrence of the deposits close to the surface and mining-smelting activities, and pose a serious environmental threat. Detailed studies on sulfide minerals have found that although Cd is mainly hosted in sphalerite, all common sulfide minerals (galena, chalcopyrite, pyrite) also contain Cd. There were significant spatial variations in HM speciation; upstream areas near ore deposits exhibited lower pH and higher Zn concentrations, due to acidic mine drainage and the presence of sphalerite. As the stream flows through the Baiyin district, the increasing influence from domestic wastewater led to a rise in pH, impacting HMs mobility. Mining-smelting activities were identified as the primary source of HM pollution. Crops grown near the ore district and irrigated with contaminated water were most susceptible to contamination due to combined soil and atmospheric HM uptake. Our review highlights the importance of stricter pollution control measures, cleaner irrigation sources, and careful crop selection to safeguard food safety and ecosystem health.

Identification of Heavy Metal Concentration in Citarum River Water Using the Heavy Metal Pollution Index Method

The Citarum River is the largest and longest river in West Java Province. The basin in that location has influenced by human activities and the industrial sector. One of the hazardous pollutants contained in industrial wastewater is heavy metals. This study aims to identify the content of dissolved heavy metals (Fe, Cd, Cr, Cu, Hg, Pb, and Zn) in Citarum River water, Purwakarta Regency, at three observation points, namely Jatiluhur Reservoir Outlet, Cilalawak Bridge, and Cilele Bridge. The Atomic Absorption Spectrophotometry Method is used to analyze the dissolved heavy metals. Determination the level of metal contamination using the Heavy Metal Pollution Index (HPI) method. The study results that three metals exceeded the standard based on Government Regulation 22 of 2021 Class II, namely Fe, Hg, and Zn. Fe metal in the range between 0.277-1.179 mg/L, Hg metal between 0.011-0.100 mg/L, and Zn metal between 0.017-0.074 mg/L. HPI analysis showed that at three points in both sampling periods, it indicated that heavy metals highly polluted river water because the results obtained exceeded the HPI pollutant index, which was > 100. The biggest contribution of dissolved heavy metals in the Citarum River water body was dominated by the Hg parameter

The Weibull Regression Model Analysis of Mahakam River Water Pollution Potential

Mahakam River has a vital role in the lives of the people of the East Kalimantan province, includingproviding a raw source of clean water. The multi-activity of the Mahakam River watershed, as a watertraffic lane, mining, fisheries, hotels, restaurants, and resident houses, has the potential to produce wasteinto the water. Increasing waste in the water flow can increase the pollution potential of river water,threatening people’s health. Therefore, precaution is necessary. In this research, statistical preventionwas proposed, providing information to the East Kalimantan people regarding the factors affecting thepollution potential of the Mahakam River through Weibull regression (WR) modeling on dissolved oxygen (DO) data 2022. Research data was secondary data provided by the Life Environmental Departmentof East Kalimantan province. The WR model is a Weibull distribution that is directly influenced by covariates. WR model consists of Weibull survival regression, cumulative distribution regression, hazardregression, and Weibull mean regression. This research aims to obtain the factors affecting the pollution potential and to provide the pollution potential information of Mahakam River 2022. The researchconcluded that factors influencing the pollution potential of the Mahakam River were watercolor degreeand nitrate concentration. Applying the WR model to DO data 2022 was able to provide the pollutionpotential information of Mahakam River, namely the probability of river water isn’t polluted is 0.6555,or the probability of the polluted river water is 0.3445, the pollution rate is 6 locations are polluted forevery 10 mg/L DO, and the DO average of river water is 5.7450 mg/L. Increasing water color degreeand nitrate concentration will decrease the probability of the Mahakam River being polluted, increasethe probability of the Mahakam River being polluted, increase the pollution rate, and reduce the DO ofMahakam River water.

Improving membrane fouling via high phyllosilicate properties of ZnO-Kaolin in pilot-scale hybrid membrane photocatalytic reactor (MPR) for superior river water treatment

A study evaluated a pilot-scale hybrid membrane photocatalytic reactor (MPR) using ZnO-Kaolin to treat polluted river water. ZnO-Kaolin was successfully synthesised and characterised using various methods, such as X-ray diffraction (XRD), fourier-transform infrared (FTIR), and field emission scanning electron microscopy (FESEM). XRD and FTIR analyses verified the purity of ZnO-Kaolin, showing no impurities, while FESEM revealed ZnO nanoparticle growth on kaolin surfaces. Additionally, the ZnO-Kaolin band gap was shifted, demonstrating enhancement of photo-degradation efficiency. Optimisation identified pH 5 as the most effective condition for treating the polluted Sembrong River via pilot-scale hybrid MPR integrated with ZnO-Kaolin, achieving significant removal of ammoniacal nitrogen (85.71 %), chemical oxygen demand (91.53 %), biochemical oxygen demand (84.93 %), and suspended solids (99 %). This innovative system also regulated water quality parameters, enhancing pH to 6 and dissolved oxygen to 6.3 mg/L while minimising membrane fouling. This innovative approach has promising potential for commercial-scale water pollution control.

Determining the Suitable Location of Constructed Wetland for the Polluted River Water Treatment Based on Analytical Hierarchy Process and Geographic Information System Analysis

The Tukad Badung River is a vital raw water source in Denpasar City and Badung Regency. Concerning the water pollution of the river, water treatment is necessary to manage the water quality. Constructed wetlands are a water treatment technology used for water purification. In this regard, information is essential regarding the appropriate location for the placement of the constructed wetland based on criteria related to the water treatment plant. The research was conducted to determine the suitability level of water treatment locations in the watershed using the Analytic Hierarchy Process method in integration with a Geographic Information System. The Geographic Information System analysis included overlaying steps of the processed and classified data from each criterion: land use, slope, and water pollution index. The Analytic Hierarchy Process method was carried out to obtain the weight of each criterion down to the sub-criteria, which were compiled through interviews with three informants from academic, government, and community representatives. Weight calculations were performed using Expert Choice 11 software to obtain weight values with a consistency ratio of < 0.1. Geographic Information System analysis using the Analytic Hierarchy Process method produces three suitable land types according to the level of suitability for water treatment locations, with constructed wetlands located in the upstream, middle, and downstream parts of the river. Information regarding suitable land is useful for planning the technical design of water treatment plants with constructed wetlands.

Assessing the relationship between river water pollution and the LULC composition of a basin in the Isthmus of Tehuantepec in Oaxaca, Mexico

Water pollution originating from land use and land cover (LULC) can disrupt river ecosystems, posing a threat to public health, safety, and socioeconomic sustainability. Although the interactions between terrestrial and aquatic systems have been investigated for decades, the scale at which land use practices, whether in the entire basin or separately in parts, significantly impact water quality still needs to be determined. In this research, we used multitemporal data (field measurements, Sentinel 2 images, and elevation data) to investigate how the LULC composition in the catchment area (CA) of each water pollution measurement station located in the river course of the Los Perros Basin affects water pollution indicators (WPIs). We examined whether the CAs form a sequential runoff aggregation system for certain pollutants from the highest to the lowest part of the basin. Our research applied statistical (correlation, time series analysis, and canonical correspondence analysis) and geo-visual analyses to identify relationships at the CA level between satellite-based LULC composition and WPI concentrations. We observed that pollutants such as nitrogen, phosphorus, coliforms, and water temperature form a sequential runoff aggregation system from the highest to the lowest part of the basin. We concluded that the observed decrease in natural cover and increase in built-up and agricultural cover in the upper CAs of the study basin between the study period (2016 to 2020) are related to elevated WPI values for suspended solids and coliforms, which exceeded the allowed limits on all CAs and measured dates.

Enhanced synergistic catalysis of bisphenol A in river water using an anti-aging photocatalytic membrane

Bisphenol A (BPA), as an endocrine disruptor, poses a potential threat to ecosystems and human health in aquatic environments. Membrane catalytic systems can accelerate the degradation of BPA and facilitate its conversion into harmless compounds. Nevertheless, the complex nature of the water environments and the limited stability of catalysts often result in challenges such as catalyst aging and deactivation. Herein, an anti-aging multifunctional AgFeO2 catalytic material with electron transfer membrane support was prepared for synergistic catalysis of low-energy LED light (12 W) excitation and peroxydisulfate (PDS) activation. The anti-aging photocatalytic membrane completely degraded 10 ppm of BPA within 30 min, and did not show significant aging after the long-term synergistic catalytic process. In addition, actual river water was employed to assess the aging process and catalytic efficiency in a practical environment. A 60.79 cm2 photocatalytic membrane completely purified 10 L of BPA polluted river water, while the total organic carbon content decreased by 50 %. This was mainly due to the synergistic catalytic effect of the membrane, which boosted photoelectron transfer through electron transfer shortcuts, thereby enhancing persulfate activation. Overall, the multifunctional membrane provides an effective strategy for achieving a long-lasting catalytic effect and controlling photocatalyst aging in practice.

Assessment and Removal Strategy of Microplastic Pollution in River Water in the Krueng Aceh River, Indonesia

Assessment and Removal Strategy of Microplastic Pollution in River Water in the Krueng Aceh River, Indonesia

Evaluation of blue textile dye decolorization by immobilized polyphenol oxidase using pumice stone under optimum conditions

Industrial dyes are major pollutants in wastewater and river water with an initial visible concentration of 1 mg/L. Recent studies have shown the possibility of using polyphenol oxidase in catalytic biological treatment due to its ability to oxidize a large number of dyes and pollutants in wastewater and the flexibility to work in wide ranges of temperature, pH and salinity. It is easy availability as well as the low economic cost resulting from its use in biological treatments, this enzyme polyphenol oxidase was used. The findings in this study showed that the extraction of polyphenol oxidase (PPO) from potato peel was homogenized with potassium phosphate buffer (0.1 M, pH 7) at a ratio of 1:10 (weight: volume) for two min. The result of enzyme purification by ion exchange chromatography showed that the yield of this step was 64 % and the specific activity was 6541.67 U/mg. The polyphenol oxidase was immobilized covalently on the functionalized pumice stone (25.2 U/gm) compared with other methods. The characterization results demonstrated that the optimum pH for immobilized and free enzyme activity was 6.0 while the pH range of free and immobilized polyphenol oxidase stability was from 4.5 -7.0 and 3.5 - 8.5 respectively. The better temperature for free and immobilized polyphenol oxidase activity was 25 ºC, whereas the free and immobilized polyphenol oxidase was stable at 15-35 and 15-50 °C respectively. The outcomes showed that the decolorization efficiency of blue textile dye employing immobilized polyphenol oxidase reached 99.85 % after 24 hr. for 100 mg/L concentration while for other concentrations 200, 300, 400, 500 and 1000 mg/L the decolorization efficiencies were 85.96, 76.15, 72.54, 66.94 and 63.5 % respectively. Based on the results, the immobilized polyphenol oxidase on pumice stone is highly efficient in removing textile dyes at large concentrations and in different environmental conditions.

Linking recharge water sources to groundwater composition in the Hindon subbasin of the Ganges River, India

Groundwater resources of the densely populated Indo-Gangetic Basin are under increasing pressure, not only from extensive groundwater abstraction, but also from contamination. In this study we aim to better understand how different recharge sources affect the hydrochemical and isotope composition of groundwater. We used the Hindon subbasin in Northern India as a case study. Recharge water sources and groundwater were analysed for hydrochemical variables and stable isotopes along a 50 km transect between the Yamuna and Ganges rivers. Groundwater samples were statistically clustered based on hydrochemical variables, and the spatial variation of the groundwater clusters was compared with recharge sources.Groundwater quality could be linked to both recharge from irrigation canal water as well as recharge from polluted river water of the Hindon and its tributaries. We could not directly link groundwater outside these related zones to their recharge source. However, we suspect that shallow polluted groundwater (< 40 m depth) is affected by recharge from agricultural areas and infiltration of municipal wastewater, whereas deeper unpolluted groundwater (40–80 m depth) originates from recharge by rain and river water under more pristine conditions. Our findings show that human activities significantly impact the quality of groundwater, as we found vertical recharge of clean irrigation canal water and polluted municipal, agricultural and river surface water (up to 40 m depth). At one location, groundwater at 75 m depth shows increased Cl, NO3 and SO4 concentrations, suggesting accelerated downward displacement of polluted shallow groundwater by pumping. Limited horizontal displacement was found. We present a conceptual model demonstrating the evolution from a previously unpolluted groundwater system discharging to the river, to a contemporary system with infiltration dominance of polluted river, municipal and agricultural water and local clean irrigation canal water. This model may be relevant for large parts of the Indo-Gangetic Basin.

Study of Bacterial Contamination in Katingan River in Katingan Hilir Subdistric

River water pollution is caused by waste, particularly bacterial contamination resulting from a variety of waste types generated by community activities on the river coast. Stream water that is sullied with microbes, whenever utilized reasonably, will be exceptionally risky for the strength of stream seaside networks. The most elevated instances of looseness of the bowels were in Katingan Rule at 4,920 individuals/year. This research aims to determine the type and value of coliform bacterial contamination in the waters of the Katingan River, Kasongan Lama Village, Katingan Hilir District. This research uses quantitative methods. The Katingan river water is cloudy brown, has no aroma, has a turbidity value of 50, which is strongly suspected to be high turbidity, and has a water pH of 3.3, which is strongly suspected to be acidic. All examples from the examination results were positive with a typical MPN worth of &gt;1100 MPN/g and had a place with bar molded gram-negative microbes (bacilli) and were thought to be explicitly Escherichia Coli. The experimental outcomes show that the waters of the Katingan Stream, Kasongan Lama Town, Katingan Hilir Region, are decidedly defiled with coliform microscopic organisms and have passed the edge for class 1 waterway prerequisites (1000 MPN/g).

Effective photocatalytic degradation of sulfamethoxazole using PAN/SrTiO3 nanofibers

Freshwater scarcity driven by pollution and climate change necessitates the development of effective water purification methods. There is an urgent need for innovative solutions that can efficiently remove contaminants from water sources. A effective material for the photocatalytic degradation of organic sulfonamide antibiotics from water was developed in this study. A composite of electrospun strontium titanate (SrTiO3) and carbon fibers polyacrylonitrile/strontium titanate (PAN/SrTiO3) was employed for the photocatalytic degradation of sulfamethoxazole (SMX). Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM-EDS), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterise the composite. The fibers had a thickness of ~250 nm and uniformly dispersed PAN and SrTiO3 particles. A PAN/SrTiO3 composite with a 1:1 mass ratio (20 mg) demonstrated excellent performance, achieving over 90 % degradation at pH 7 and a contaminant concentration of 5 mg/L under ultraviolet (UV) light irradiation during 60 min. The composite was tested for the photodegradation of the major organic pollutant (SMX) in distilled and river water. In river water, the degradation efficiency exceeded 80 % at pH 7 because of the formation of secondary radicals involved in antibiotic degradation. SMX degradation was described using a pseudo-first order kinetic equation using the Langmuir-Hinshelwood model. These results underscore the novelty and significance of the PAN/SrTiO3 composite and demonstrate its high efficiency and potential for large-scale water purification applications.

Quantifying seasonal variations in pollution sources with machine learning-enhanced positive matrix factorization

As the pace of industrialization and urbanization accelerates, water quality management faces increasing challenges, with traditional methods for pollutant source apportionment often proving inadequate in handling complex environmental data. This study enhances the precision and reliability of pollutant source identification by integrating Positive Matrix Factorization (PMF) models with diverse machine learning techniques. Utilizing data from 17 water quality monitoring stations along the Wuding River from 2017 to 2021, we employed Random Forest (RF), Support Vector Machine (SVM), Elastic Net (EN), and Extreme Gradient Boosting (XGBoost) models to predict the Water Quality Index (WQI) during dry and wet seasons. Results indicate that the RF model exhibited optimal performance in the dry season (R2 = 0.93), while the SVM was superior in the wet season (R2 = 0.94). SHAP (SHapley Additive exPlanations) value analysis identified CODMn and NH3-N as significant influencers on WQI in the dry season, whereas COD, BOD, and TP gained prominence during the wet season. SHAP values reveal the contribution of each feature to the model output, thereby enhancing the model’s transparency and interpretability. Additionally, feature importance identified by machine learning was utilized as weights to optimize the contribution rates predicted by the PMF model. The optimised model was able to identify the contribution of domestic and farm effluent discharges more accurately in the dry season, with a significant increase in the percentage of identification from 19.4 % to 45.4 %, and an increase in the percentage of contribution from agricultural non-point sources and domestic effluent in the rainy season. This research offers a novel perspective on the characteristics of river water pollution and holds significant implications for formulating data-driven environmental management strategies.

REMOVAL OF VARIOUS METAL IONS IN WATER BY DIFFERENT PRE-TREATMENTS OF FLY ASH

Rapid urbanisation in Malaysia has accelerated water pollution in rivers and other water sources, causing irreversible harm to the ecosystem. In view of that, this study aimed to work on using fly ash to address certain heavy metal components (chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn)) present in polluted water. The experiment employed three batches of fly ash. Two batches were treated with sodium hydroxide (NaOH-FA) and hydrochloric acid (HCl-FA), whereas one batch was left untreated (UFA). The three batches of adsorbents were examined by using a jar test after solutions containing 100 mg/L of Cr, Cu, Ni, and Zn ions were made. The results of various contact periods demonstrated that the fly ash had variable capacities for metal ion adsorption. The maximum adsorption of UFA was 79.958%(Cr), 80.814%(Cu), 81.580%(Ni), and 82.742%(Zn) while HCl-FA was adsorbing 77.148%(Cr), 82.546%(Cu), 78.896%(Ni), and 78.248%(Zn). NaOH-FA in this study was found to adsorb 80.828%(Cr), 79.230%(Cu), 81.692%(Ni), and 77.394%(Zn). Further to this, it was revealed that the Temkin Isotherm model was best fitted with the highest R² values (&gt; 0.98). The negative value of the slope, B indicated that the adsorption is an endothermic process which leans towards physical adsorption. In conclusion, this study demonstrated the successful application of fly ash in water or wastewater treatment of metal ions.

The evaluation of Small River water pollution caused by tailing spill in the Northeast of China using high-resolution images

The global mining sector generates billions of tons of tailings stored in thousands of tailing ponds. The occasional spills of tailings resulting from dam failures or pipe damage can have devastating consequences, threatening nearby human populations and ecosystems, particularly those located along river corridors. Satellite remote sensing technology is a vital supplementary method to traditional field methods for monitoring and evaluating the water pollution caused by spilled tailings. The researchers have developed workflows to evaluate the effect of tailing spills on water quality using low and medium-spatial satellite imagery from satellite sensors. Due to insufficient spatial resolution, these workflows were hard to apply to monitor the water pollution caused by spilled tailing in small rivers. Using valuable on-site data from a river water pollution incident caused by spilled tailing, a workflow utilizing high-resolution satellite imagery (GF1) was developed. This workflow incorporates a machine learning algorithm (improved DeepLabV3+) to extract water masks first and a novel spectral index method to determine TSM concentrations. The improved DeepLabV3+ algorithm can obtain an accurate water mask no matter the water pixels, whether influenced by the tailing spills from GF1 imagery with IoU of 82.66%, Precision of 93.21%, Recall of 87.96%, and F1-score of 90.51%. A new spectral index combination algorithm that provides reliable TSM products for an extensive TSM magnitude range was presented to assess the level of water contamination. The strong correlation (R2 = 0.97) between in situ TSM and Mo concentrations suggests that the retrieved TSM products are suitable for assessing the water pollution caused by the spilled tailing. This workflow provides a method for monitoring and evaluating water pollution resulting from spilled tailings in small rivers. It utilizes high-resolution satellite data to observe and analyze the pollution levels.

Potential of ecological water treatment elements to reduce pollution of river water used for urban agriculture in Addis Ababa, Ethiopia

Cities in developing countries, such as Addis Ababa, face enormous challenges as a result of high demand for food and clean water, as well as the generation of large amounts of urban waste that is discharged into natural water bodies, contaminating rivers, lakes, and other freshwater bodies used in urban agriculture. Farmers in Addis Ababa and nearby areas use polluted irrigation water diverted from the highly contaminated Little and Great Akaki rivers. The study aimed to assess how well a floating treatment wetland with vetiver grass could reduce irrigation water pollution at the Mekanisa-Gofa-Lafto Cooperative (MGLC) farm in Addis Ababa, Ethiopia. Additionally, the study sought to provide design recommendations that could be implemented at the farmer level. The irrigation water underwent a 7-day treatment using a Vetiver grass floating treatment wetland. A field test was also conducted to evaluate the effectiveness of the floating treatment wetland in reducing pollutants at the study site. The results showed that the floating treatment wetland was able to reduce the Biochemical Oxygen Demand (BOD) (73.68%), Chemical Oxygen Demand (COD) (73.92%), Acidity/Basicity (pH) (0.39%), Chloride (Cl−) (43.12%), Total Hardness (66.56%) and Total Suspended Solid (TSS) (96.21%) values, approaching the recommended irrigation water quality guideline values within 3 days. In contrast, there was an increase in Electro Conductivity (EC) (22.2%) and Sodium (Na) (15.2%) concentrations, which exceeded the recommended values, due to evapotranspiration or the entry of the surrounding soil into the irrigation water of the study site.

Feasibility Study of Online Treatment of Polluted River Water Using Duckweed and Modified Flow Pattern

Feasibility Study of Online Treatment of Polluted River Water Using Duckweed and Modified Flow Pattern

TARGETED SCREENING OF PHENOLIC TOXICANTS IN WATERS AND BOTTOM SEDIMENTS OF THE MIDDLE REACHES OF THE DON RIVER

The targeted screening of 11 phenolic toxicants (phenol, chlorophenols, 2,4-dichlorophenoxyacetic acid, octylphenol, nonylphenol, bisphenol A) has been carried out over river water and bottom sediments (BS) in the middle reaches of the Don river within the boundaries of the Voronezh Region. Three sampling points were selected for quantitative chemical analysis: in the zone affected by the discharge of sewage treatment plants of a large city (Voronezh), in the district centre (the city of Liski), and in an area with insignificant anthropogenic influence. The concentrations of phenolic compounds were determined using gas chromatography - mass spectrometry (GC-MS), the analytes were preconcentrated on a magnetic sorbent functionalised with aminated hypercrosslinked polystyrene. Sampling was carried out four times a year, taking into account seasonal climatic fluctuations and precipitation. The maximum concentrations were established in the spring for 2,4-dichlorophenoxyacetic acid (1022 ng/L) and 2,4-dichlorophenol (557 ng/L). In bottom sediments, the highest concentrations are achieved for alkylphenols: 1.99 and 7.84 μg/g for octylphenol and nonylphenol, respectively. Bisphenol A has not been found in detectable amounts in waters, however, a significant concentration of this compound has been found in bottom sediments: 3.18 μg/kg. The bottom sediments were also determined to contain 2,4,5-trichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol. The maximum concentrations of phenolic pollutants in river water are usually observed in spring during high water and after heavy rainfall. Phenol concentrations in bottom sediments are less susceptible to seasonal fluctuations. The hydrophobicity of substances and an increase in their stability against degradation significantly affect their accumulation in BS.

Performance of bio-nest by modified basalt fiber carriers on the enhanced remediation of low-carbon and -nitrogen urban black-smelling water

ABSTRACT Biological contact oxidation reactors employing modified basalt fiber (MBF) were constructed to systematically investigate the impact of various hydraulic retention times (HRTs) and aeration durations on nitrogen and phosphorus removal in low carbon and polluted river water. The experimental findings underscored that configuring the HRT to 36 h and maintaining an aeration ratio of 1:2 yielded the most favorable outcomes for the removal of COD, NH4+ -N, total nitrogen (TN), and TP from synthetic low carbon, source-polluted river water. Detailed microbial sequencing elucidated the predominant bacterial phylum within the MBF reactor, identified as Proteobacteria. The dominant genera encompassed Pseudomonas, Aeromonas, and SM1A02. This microbial composition, marked by a high abundance of denitrifying genera, corroborated the robust denitrification capacity exhibited by the MBF reactors. The orchestrated combination of optimal operational parameters and the prevalence of key microbial taxa substantiate the efficiency of MBF reactors in effectively mitigating nitrogen and phosphorus in low carbon source river water.

Balancing river water pollution and agricultural development: A tradeoff threshold approach

Balancing environmental protection and social-economic development in agricultural land use management is a dilemma for decision-makers. Based on the modelling of the impacts of land use changes on river water pollution by SWAT model, the tradeoff between tea plantation expansion and river water quality was detected. SWAT model performs well in simulating the non-point source (NPS) pollution in agricultural watershed. The results showed that the tea plantation area expanded dramatically from 44 km2 in 2000 to 169 km2 in 2020 at the high cost of forest land. Consequently, the mean contents of NO3−-N and TN have significantly increased by 100% and 91% respectively in the past 20 years. And the NO3−-N in river water accounted for over 80% of TN in the tea plantation area. The NO3−-N and TN concentrations were positively related with the proportions of tea plantation area (Tea%) at different periods. The high pollution levels of NO3−-N and TN are priority control targets for river water quality management. The results indicated that the proportion of tea plantation thresholds lead to abrupt changes in river water quality. When the Tea% exceeded 3.0% in 2000, the probability of N pollution increased sharply. Whereas in 2020, it is suggested that the Tea% should not exceeds 18% to avoid sudden deterioration of water quality. The critical interval value of the Tea% for sudden change in N pollution showed an obvious increase tendency. The accelerating of nutrient pollution in rivers reduced the sensitivity of water quality to tea plantation expansion. Our results can provide new insights and empirical evidence for balancing the tradeoff between agricultural development and river water quality protection by demonstrating the carrying capacity threshold of river water environment for the expansion tea plantation.