Water Environmental Quality Standards Research Articles

Assessment of medium and small river health based on macroinvertebrates habitat suitability curves: a case study in a tributary of Yangtze River, China

Abstract The health of medium and small river ecosystems is threatened by increasing hydropower development and human activities. How to properly diagnose rivers has become a global concern. As a well-accepted theory, the aquatic organism density can be an indicator of river health. A new river health assessment method based on macroinvertebrates habitat suitability curves (M-HSC) was proposed. In this study, the health of Qiaobian River (QBR), a tributary of Yangtze River, China was evaluated by investigating the distribution of macroinvertebrates, chemical and physical parameters during winter 2018 (low flow season) and summer 2019 (high flow season). Based on habitat suitability of dominant macroinvertebrates, the key habitat factors were screened by canonical correspondence analysis (CCA) and Pearson correlation analysis. Suitability curves were determined by Generalized Additive Model (GAM). Ecosystem health comprehensive index method was used to evaluate the health status. The results show most suitable conditions for Corbicula fluminea containing chemical oxygen demand (CODMn) of 1.48 mg L−1, total nitrogen (TN) of 0.27 mg L−1, dissolved oxygen (DO) of 11.17 mg L−1, pH of 8.42, turbidity of 1.76 NTU, and water depth (Dep) of 0.35 m. The health status of QBR is spatially heterogeneous with the apparently better upstream than the downstream. In general, 25, 12.5, 12.5% of the samples were classified as nature, health and sub-health status, respectively and the rest 50% were lower than sub-health. The results are consistent with the environmental quality standards for surface water in China (GB3838-2002), suggesting the applicability of macroinvertebrates habitat suitability for evaluating river health. By minimizing the temporal and spatial limitations of comprehensive evaluation method and indicator species method, this study, for the first time, used macroinvertebrates habitat suitability curves to assess the health of medium and small rivers. The study will provide new insights for future river health assessments.

The fuzzy comprehensive evaluation (FCE) and the principal component analysis (PCA) model simulation and its applications in water quality assessment of Nansi Lake Basin, China

The Fuzzy Comprehensive Evaluation (FCE) and the Principal Component Analysis (PCA) were simulated to assess water quality of the Nansi Lake Basin, China. The membership functions were established via the Nor-Half Sinusoidal Distribution Method, and the weight was calculated via the Exceeding Standard Multiple Method. To enhance the efficiency of extracting principal pollutant, the eigenequation was solved through the Jacobi Method, and the principal components were extracted based on eigenvalue, contribution ratio, accumulating contribution ratio, principal component loading and score. Water quality classification based on “National Surface Water Environmental Quality Standards of China (GB3838-2002) was used to assess the water quality. Considering the difference of the temporal and spatial distribution in average, water quality of Level I was 28.9%, 28.1%, 25.1%, 25.6%, respectively in spring, summer, autumn, and winter, which suggested that water quality in spring and summer was better than in autumn and winter. The order of water quality was Zhaoyang Lake (Level I) > Nanyang Lake (Level I) > Dushan Lake (Level III) > Weishan Lake (Level III and IV). There were four extracted principal components that can replace the fourteen pollutant indexes for assessing water quality. According to the annual mean data of the 1st principal components, the most important pollutions were heavy metals, including As (0.933), Hg (0.931), Cd (0.929), Cr(VI) (0.926), Pb (0.925), and Cu (0.534). It is proved that the combined FCE-PCA model could provide valuable information in the water quality assessment for the Nansi Lake Basin.

A novel tubular up-flow magnetic film photocatalytic system optimized by main factors control for efficient removal of chlorophenols wastewater

Chlorophenols (CPs) are still used as raw material or intermediate in some industries. Photocatalytic oxidation is free from secondary pollution, but the efficiency is restricted by some main factors. In this study, a novel high efficiency tubular up-flow magnetic film (TUMF) photocatalytic system was investigated based on the magnetic lanthanum doping core-shell Fe3O4@SiO2@TiO2 (La-FST) nanoparticles. When the dosage of La-FST was 0.4 g/L, the flow velocity was 94.2 mL/min, and the circulated irradiation of 15 W maintained 40 min, the average removal rate of 2,4-dichlorophenol (2,4-DCP) was reduced significantly from 10 mg/L to 0.0803 mg/L by TUMF system, meeting the limits of the particular items (0.093 mg/L) from national environmental quality standards for surface water, avoiding the problem of photocatalyst separation and loss. The photoinduced holes (h+) was the key active radical to oxidize 2,4-DCP, and the main factors of TUMF system could be well controlled to achieve satisfactory effluent quality. A prediction method of photocatalytic reaction time in a multistage series TUMF system was established to remove 2,4-DCP from 100 mg/L to 0.5 mg/L, saving 86 min. The novel high-efficiency TUMF system provides a technical selection for the photocatalytic degradation of CPs and other refractory organics.

The impact of natural weathering and mining on heavy metal accumulation in the karst areas of the Pearl River Basin, China

This paper presents the heavy metal content in river water, sediment and bedrock in the karst area of the Pearl River Basin in China to evaluate the long-term impact of natural weathering and mining on the ecological environment. The results show that Cd and As is 2–3 times more enriched within the carbonate bedrock of the Pearl River Basin compared to the upper continental crust (UCC), which is indicative of high geological background values. Within the river water of the upper reaches of the Diaojiang River (a tributary of the Pearl River), which flows through the Dachang super-large orefield, Zn, As, Cd and Sb exceeds the environmental quality standards for surface water (WQS) by more than an order of magnitude. Among these, Zn and Cd sharply decreases to within the WQS in the lower reaches of the river, but the content of As and Sb in the estuary is still several times higher than the WQS. Cd in the sediments of the small carbonate watersheds and in the mainstream of the Pearl River only present a low-moderate ecological risk. In contrast, severe heavy metal pollution of the sediments of the Diaojiang River Basin is observed. Even in the lower reaches, remote from the mining area, the content of Pb, Zn, As and Cd in the sediments is still two orders of magnitude higher than the soil background values. The content of both Cd and As presents a very high ecological risk, indicating that under the cumulative effect of high geological background values and mining, full restoration of the ecological environment in the Diaojiang River Basin is a complex and long-term process.

Hydrogeochemical and environmental water quality standards in the overlap between high mountainous natural protected areas and copper mining activities (Mapocho river upper basin, Santiago, Chile)

Natural hydrogeochemical backgrounds or signatures from rivers around the world show great differences depending on the geological and hydrological settings where the specific watershed is placed. This fact is especially relevant and notorious, when the metallic content of waters draining hydrothermally-altered high-mountainous regions is considered. The present study offers a hydrogeochemical perspective to improve the generation of Environmental Water Quality Standards (EWQS) in mineralized high mountain regions comprised by rivers unaffected and affected by acid rock drainage (ARD). To this end, the complex and versatile reality at the Mapocho river upper basin (comprised by a natural ARD affected sub-basin, a mining intervened sub-basin and a third sub-basin with Andean unaffected waters) was used to evaluate the effect of seasonal and long-term climatic variations on hydrothermally-altered high-mountainous regions.In addition, 22 different environmental water quality standards (EWQS) from different countries around the globe were analyzed. This information was used to define what could be understood as “an acceptable water quality for environmental use”. Also, the obtained elemental concentration and physicochemical ranges were compared with the results obtained at the Mapocho upper basin to assess the importance of regional and local geochemical backgrounds on the generation of EWQS. As a result of this information generation, compilation, analyses and intercomparison, several recommendations to consider during the generation of EWQS at heterogenous high mountainous watersheds comprised by both ARD affected and unaffected sub basins were made. Special attention was paid to the incorporation of seasonal variations and long-term effects (climate change) on the generation of more realistic and useful EWQS.

Using Principal Components Analysis and IDW Interpolation to Determine Spatial and Temporal Changes of Surface Water Quality of Xin'anjiang River in Huangshan, China.

This study was aimed at assessing the spatial and temporal distribution of surface water quality variables of the Xin’anjiang River (Huangshan). For this purpose, 960 water samples were collected monthly along the Xin’anjiang River from 2008 to 2017. Twenty-four water quality indicators, according to the environmental quality standards for surface water (GB 3838-2002), were detected to evaluate the water quality of the Xin’anjiang River over the past 10 years. Principal component analysis (PCA) was used to comprehensively evaluate the water quality across eight monitoring stations and analyze the sources of water pollution. The results showed that all samples could be analyzed by three main components, which accounted for 87.24% of the total variance. PCA technology identified important water quality parameters and revealed that nutrient pollution and organic pollution are major latent factors which influence the water quality of Xin’anjiang River. It also showed that agricultural activities, erosion, domestic, and industrial discharges are fundamental causes of water pollution in the study area. It is of great significance for water quality safety management and pollution control of the Xin’anjiang River. Meanwhile, the inverse distance weighted (IDW) method was used to interpolate the PCA comprehensive score. Based on this, the temporal and spatial structure and changing characteristics of water quality in the Xin’anjiang River were analyzed. We found that the overall water quality of Xin’anjiang River (Huangshan) was stable from 2008 to 2017, but the pollution of the Pukou sampling point was of great concern. The results of IDW helped us to identify key areas requiring control in the Xin’anjiang River, which pointed the way for further delicacy management of the river. This study proved that the combination of PCA and IDW interpolation is an effective tool for determining surface water quality. It was of great significance for the control of water pollution in Xin’anjiang River and the reduction of eutrophication pressure in Thousand Island Lake.

Effects of Artificial Destratification and Induced-natural Mixing on Water Quality Improvement in a Drinking Water Reservoir

To explore the effects of water quality improvement by artificial destratification and artificially-induced mixing, as well as realize the conditions of artificial mixing and natural mixing, the Lijiahe Reservoir was selected to monitor the indexes of water quality and hydrometeorology from June 2017 to April 2019 and to analyze the characteristics of variations in water temperature, dissolved oxygen, and pollutants during the natural and induced-mixing processes. The results demonstrated that:① The natural process had the features of a long period of thermal stratification and only a short period of mixing of about 2.5 months. Through the operation of water-lifting aerators (WLAs) during the induced-mixing process, the water body was completely mixed and entered the cooling period at the end of September, achieving the conditions of induced-natural mixing. The surface water temperature and average air temperature were 20.17℃ and 16.5℃, respectively, and the water body continued to be naturally mixed after the WLA system was shut down, which led to a natural mixing cycle of 5.5 months. ② During the natural-mixing process, the concentration of pollutants was relatively high in the whole period, and the concentration of surface pollutants in the mixing stage presented a trend of increasing first and then decreasing. The oxycline appeared with thermal stratification, and the anaerobic cycle in the bottom of water column reached 6 months. ③ Compared with the natural-mixing process, the hypolimnetic anaerobic condition was eliminated and the control effects of pollutants dominated during the induced-mixing process. Simultaneously, the concentrations of NH4+-N, TP, Fe, and Mn in the bottom of the water column were cut by 76.2%, 75.5%, 82.2%, and 82.1%, respectively, during the same period from October to March of the following year, and met the "Environmental Quality Standards for Surface Water". This study shows that the artificially-induced mixing process contributes to water quality improvement and mixing-period prolongation.

A Combination Model for Quantifying Non-Point Source Pollution Based on Land Use Type in a Typical Urbanized Area

Water pollution poses threats to urban environments and subsequently impacts the ecological health and sustainable development of urban areas. Identifying the spatiotemporal variation in non-point sources (NPS) pollution is a prerequisite for improving water quality. This paper aimed to assess the NPS pollution load and then recognized the spatiotemporal characteristics of the pollution sources in a typical urbanized area. A combination model based on land use type was used to simulate the NPS pollution load. The results showed the following: (1) ponds and farmlands had higher pollution production intensities than other land use types, but the intensity and magnitude of pollution emissions were generally greater in urban areas; (2) monthly and annual total nitrogen (TN) and total phosphorus (TP) emissions had the same pattern as rainfall, and TN and TP emissions accounted for 56.2% and 58.0%, respectively, of the total in summer; (3) TN pollution was more serious than TP pollution in the study area, especially in farmlands; (4) urban runoff (UR) and livestock and poultry breeding (LPB) were the main sources of NPS, TN and TP emissions in the study area. If these NPS pollutants cannot be removed from this area, a large amount of freshwater is needed to dilute the current rivers to meet the requirement of the fourth category of China national environmental quality standards for surface water. This problem is serious in the control of polluted rivers in many cities throughout China.

Low-impact development facilities for stormwater runoff treatment: Field monitoring and assessment in Xi’an area, China

Field studies are valuable because of the insufficient number of field performance data in low-impact development (LID)-related research. Four typical LID facilities in northwest China were built and monitored. These facilities differ in their impervious/pervious bottom, inflow underlying surface, media types, and combinations. The water volume reduction of impervious rain garden filled with native loess decreases by approximately 20% when the total daily rainfall levels gradually increase from light to heavy. Several technical measures, such as media modification, setting internal storage area, reducing drainage area, and increasing media thickness, have been taken to improve the runoff regulation effect. The volume reduction rate in light and medium-sized rainfall (daily rainfall totals < 25 mm) is above 68.2% for two improved facilities, namely, mixed media rain garden and layered media bioswale. For impervious native loess rain garden, mixed media rain garden, and layered media bioswale, the median values of inflow total suspended solid (TSS) event mean concentrations (EMC) are reduced from 43.5 to 68.5 mg/L to 22.4–24.3 mg/L. In accordance with the Class IV limits of Surface Water Environmental Quality Standards (total nitrogen (TN) = 1.5 mg/L; total phosphorus (TP) = 0.3 mg/L), the probabilities of the effluent TN concentration exceeding the IV limit are 32.7%, 42.3%, and 19.8% for the three facilities. The exceedance probabilities for TP are 18.5%, 6.5%, and 8.9%. The weighted results indicate that the annual load reduction rate is more stable than the fluctuating concentration removal, which is above 60%. An approach to estimate the total scale of LID construction was established on the basis of rainfall level proportion, land use types, and monitored data. When native loess and mixed media rain garden are applied in building areas and layered media bioswale is applied in road area, the LID implementation cost is approximately 36.0 billion CNY until 2030 for Xi’an City.

Bioaccessibility of metals/metalloids in willow catkins collected in urban parks of Beijing and their health risks to human beings

Air pollution and its resulting health risks in Beijing City have been widely investigated by scientists and administrators. However, the health risks caused by willow and poplar catkins in April and May (known as “spring snow”) have been rarely reported. Poplar and willow are the two common trees in Beijing City that generate many whirling catkins in the air. The chemical composition of catkins remains unknown. In this study, catkins and dust samples were collected in several parks in Beijing. The total concentrations of metals/metalloids in catkins measured through inductively coupled plasma mass spectrometry were generally lower than those of the corresponding dust samples, and they were lower than the risk control standard for soil contamination of development land. The simulated rain and lung fluid extraction rates of catkin samples were significantly higher than those of the dust samples. The concentration of extracted Pb and Zn using simulated rainwater exceeded the environmental quality standards for surface water (0.1 and 2.0 mg/L for Pb and Zn, respectively), indicating the possibility of runoff pollution. Scanning electron microscopy images showed that fine particles (<10 μm) are attached to the surface of catkins. Therefore, the metals/metalloids in fine particles adsorbed by the catkin samples possess higher bioaccessibility than that in the dust samples based on different sizes of particles. A significant correlation is found between Pb in catkin and Pb in dust. Therefore, attention should be paid to the possible increase in metal/metalloid concentrations in catkins planted in contaminated areas.

Combined heterotrophic and autotrophic system for advanced denitrification of municipal secondary effluent in full-scale plant and bacterial community analysis

Total nitrogen (TN) removal is the major technical challenge for wastewater treatment plants to meet the more stringent discharge standard. In this study, lab- (0.05 m3/d), pilot- (1000 m3/d) and full-scale (10,000 m3/d) combined heterotrophic and autotrophic denitrification reactors (HARs) were designed and operated to treat municipal secondary effluent. During the 110-day stable operation, the effluent TN was reduced below 2.5 mg/L without secondary pollution causing by the excessive addition of organics, close to Class IV of Environmental Quality Standards for Surface Water. The bacterial richness and diversity increased with the expansion of reactor scale. Denitrifying bacteria (DB) dominated in all reactors, however, Thiomonas (12.42%), Methylotenera (6.35%), Thiobacillus (20.62%), Methyloverstatilis (5.44%) and Thauera (8.21%) were the main genera in lab-, pilot- and full-scale reactors respectively. The denitrification efficiency temporarily deteriorated at the later stage, and redundancy analysis (RDA) indicated the obviously increased sulfate reducing bacteria (SRB) and sulfide were main contributors. Sludge supplement rapidly recovered the reactors performance in five days. This study suggests that HARs could be a promising technique for advanced denitrification of the municipal secondary effluent.

Water Quality Assessment and Variation Trends Analysis of the Min River Sea-Entry Section, China

In order to further understand the status of the water quality of Min River’s sea-entry section, the index systems for water environmental quality assessment was built based on twenty evaluation parameters including dissolved oxygen (DO), permanganate index (CODMn), chemical oxygen demand (CODCr), biochemical oxygen demand (BOD5), ammonia (NH3-N), total phosphorus (TP), and total nitrogen (TN). Water environmental quality of Min River’s sea-entry section in 2015–2017 was evaluated by utilizing the entire-array-polygon synthesis illustration method, accompanied by the time-dependent trend analysis. The results demonstrated that the water environmental quality of Min River’s sea-entry section was between the levels I and II of the Environmental Quality Standards for Surface Water (EQSSW, GB3838-2002) in 2015–2017, indicating a generally good water quality. The water quality was affected by both natural factors (such as temperature, rainfall, and runoff) and human factors and had a tendency to deteriorate at the duration of 2015–2017. The research results are of great significance for further understanding of the discharge of pollutants from the Min River basin and will be a strong support for the scientific decision-making of marine management in Fujian Province.

P-Pyridine BODIPY-based fluorescence probe for highly sensitive and selective detection of picric acid.

A novel fluorescence probe p-PBP for PA was synthesized based on a basic N atom as the electronic donor. The probe could detect PA over TNT, CE, PETN, RDX, HMX, NB, NT, DNT, NP, DNP, and common inorganic explosive ions (K+, Ba2+, NH4+, NO3-, ClO3-, and ClO4-), and common ions (Na+, Ca2+, and Mg2+) with high selectivity. The fluorescence quenching was attributed to the photo-induced electron transfer (PET) processes from the excited state of p-PBP to the ground state PA. The detection limit of probe p-PBP for PA was as low as 13.06 nmol/L, which is far lower than the concentration stipulated by the Environmental quality standards for surface water. The response time was less than 30 s. Hence, the fluorescence probe p-PBP was successfully developed to detect the concentration level of PA in real samples, which would provide a novel quantitative analysis method of PA in forensic science.

Ranking connectivity risk for phosphorus loss along agricultural drainage ditches

Agricultural drainage systems comprising both in-field pipe drains and surface ditches are typically installed to remove excess water from agricultural land. These drainage networks can provide connectivity between phosphorus (P) sources and surface waters thereby increasing the risk of P loss to rivers and streams. The objective of this study was to derive a farm-scale drainage ranking that categorises drainage ditches in terms of P loss risk based on connectivity and physic-chemical characteristics. Ten pilot farms were selected to characterise drainage networks through ground survey and, sediment and water sampling. Five drainage ditch categories were derived based on landscape setting and connectivity. Each category recorded soluble and reactive P concentrations above environmental water quality standards. To assess the risk of surface ditches as a connectivity vector between agricultural P and surface waters ditches were ranked in order of P loss risk by integrating landscape position and sediment P chemistry. Elevated sediment P with high equilibrium P concentration (EPCo) were associated with ditches connected to farm yards, and in sediment sampled at ditch outlets, suggesting P deposition over time indicative of a legacy P source. The greatest risk of P loss was attributed to ditches connecting farm yards to streams, and ditches that connected the drainage network to surface waters, or Outlets. These results rank connectivity risk for P loss along agricultural drainage ditches for farm level risk assessment to target P loss mitigation measures to the appropriate locations.

Technical study on national mandatory guideline for deriving water quality criteria for the protection of freshwater aquatic organisms in China

Water quality criteria are the basis for formulating environmental water quality standards, and are also an important part of environmental water protection and environmental management programs. The current study focused on a systematic discussion of the current research progress of water quality criteria theories and methodology for aquatic organisms both in China and internationally. This study also successfully pointed out key scientific issues which should be considered in the determination of water quality criteria guidelines from the following perspectives for a national strategy: the selection of pollutants; data collection and screening; species selection; water quality criteria derivation methods, and so on. For the first time, this study systematically introduced technology for the determination of water quality criteria guidelines for protecting aquatic organisms which was suitable for China's regional characteristics and national conditions. Furthermore, this study pointed out the key research directions which should be considered in the future construction of China's environmental criteria and management systems, in order to provide technical support for environmental protection and management projects.

Environmental risk assessment of the anionic surfactant sodium lauryl ether sulphate in site-specific conditions arising from mechanized tunnelling

Sodium lauryl ether sulphate (SLES) is the anionic surfactant commonly utilized as the main synthetic chemical component in most foaming agents used in mechanized tunnelling. This produces huge amounts of soil debris which can contain residual concentrations of SLES. The absence of environmental quality standards for soil and water and the limited information about SLES persistence in real excavated soils do not facilitate any re-use of soil debris as by-products. The environmental risk assessment (ERA) of foaming agents containing SLES can be a valid tool for this purpose. In this study, an ERA analysis of SLES in 12 commercial formulations (cf) used for tunnelling excavation was performed. Various soils from different tunnel excavation sites were conditioned with the selected foaming agents containing SLES. Predicted or measured environmental concentrations (PECs, MECs) were determined and then compared with the Predicted No Effect Concentrations (PNECs) for both the terrestrial and aquatic compartments. The results indicate a reduction of the potential risk over time for these ecosystems, with differences depending on both the commercial foaming formulation and the spoil material characteristics. However, because potential threats to the natural environment cannot be excluded, some risk management and mitigation actions are discussed.

Temporal–spatial distribution characteristics and combinatorial risk probabilities of water pollutants in the Guo River Basin, China

This study used water-quality monitoring data from seven monitoring stations in the Guo River Basin from 2003 to 2012 and three selected water-quality indexes (total phosphorus: TP, ammonium nitrogen: NH3–N, and permanganate index: CODMn) that were divided into five categories (classes I, II, III, IV, and V) according to Chinese environmental quality standards for surface water (GB 3838–2002). The results indicated that the concentrations of TP, NH3–N, and CODMn showed a significant decreasing trend at Xuanwu Sluice, Huangzhuang, Boxian Sluice, Guoyang, and Mengcheng Sluice by the Mann–Kendall trend analysis; the water pollution was worse in the upstream region, but it was relatively good in the downstream region, and the water pollutant concentrations improved significantly by the cluster analysis. In this study, a marginal distribution of water-quality indexes and a combinatorial probability distribution of the copula function are established based on the basic principle of the copula function. The Gaussian copula function was selected to calculate the combinatorial risk probability of the water pollutants by the fit test of copula function and the goodness-of-fit evaluation. Results show that the combinatorial risk probability varies substantially when the water-quality indexes reach different states under different combinations, such as the combinatorial risk probability showed a decreasing trend with increasing TP concentration when the NH3–N concentration was certain and CODMn reached the class III or class IV level at Xuanwu Sluice and Boxian Sluice; the combinatorial risk probability presented a decreasing trend with increasing TP concentration when the NH3–N and CODMn concentrations were certain at Mengcheng Sluice and Longkangji; the combinatorial risk probability presented a trend that first increased and then decreased with increasing CODMn concentration when the TP and NH3–N concentrations were certain. The temporal–spatial distribution characteristics and combinatorial risk probabilities obtained in this study will provide a basis for management, water pollution control, water resources protection, and sustainable development of the basin.

Pollution Sources and the Stratification Effects on Water Quality in Lijiahe Reservoir

An in-depth understanding of the source of pollutants and the evolution of water quality is a prerequisite for water pollution control in source water reservoirs. Lijiahe Reservoir is an important water source for Xi'an. To strengthen the protection of Lijiahe Reservoir, water quality monitoring was carried out monthly from December 2016 to December 2017. The results showed that the main pollutant source was upstream water, and its percentage contribution to the bulk pollutants was 99.52% for permanganate index, 99.41% for TN, and 99.23% for TP. The main source of pollution in the upstream Dongcaiyu was the upper reach with Gepai Primary School and the turf service area. The main source of pollution in Xicaiyu was the upper reach with a chicken farm and fishery. In summer and autumn, Lijiahe Reservoir exhibited thermal stratification. During the stable stratification period, the maximum concentrations of TN, TP, permanganate index, TOC, Fe, and Mn in the water body were as high as 3.32, 0.177, 5.21, 3.01, 0.21, 0.235 mg·L-1, respectively, under the dual effects of exogenous pollution and bottom anaerobic release. The maximum concentrations of TN, TP, Fe, and Mn exceeded the Class Ⅲ water limit of Surface Water Environmental Quality Standards (GB 3838-2002). The higher nutrient levels promoted large-scale reproduction of algae. The density of algae in the upper water reached 2.18×108 cells·L-1, and the dominant algae species were Microcystis aeruginosa and Aphanizomenon flosaquae, which pose a significant threat to water quality. Therefore, the primary goal for water pollution control in Lijiahe Reservoir is to take effective measures to control algae blooms, and at the same time, reduce the input of upstream pollutants.

Treatment of polluted surface water with nylon silk carrier-aerated biofilm reactor (CABR)

Carrier aerated biofilm reactor (CABR) with nylon silk as the biofilm growth carrier was constructed to treatment of polluted surface water, which could improve the practical application in comparison with MABR process. The results show that CABR process can effectively improve the self-purification capacity of the polluted surface water, efficient removal of COD and NH3-N, making water quality achieve the level V of Environmental Quality Standards for Surface Water (GB 3838-2002, China). Modified nylon silk can alter the community structures and increase bacteria during CABR process operation. Large pore size of nylon silk leads to the formation of special biofilm structure in CABR. Extracellular polymer (EPS) and membrane fouling resistance distribution indicated that the nylon silk fouling control ability of CABR reactor is much higher than that of membrane-aerated biofilm reactors (MABR). The results show that the CABR process can effectively purify surface water and improve the practical application.

Microalgae in two freshwater lakes and an estuary as a result of groundwater contamination from households

The increasing incidence of cyanobacterial blooms in Southern African aquatic systems is raising concern about the potential for these microorganisms to contaminate potable water with toxic secondary metabolites. This study focused on two lakes, an estuary and the sea in a small catchment in Maputaland, northern KwaZulu Natal, South Africa, fed by groundwater impacted by sewage effluent discharged from houses and residential complexes. The important effluents identified were nitrate, nitrite, ammonium-N and ortho-phosphate at concentrations above that which might be expected in a sandy catchment where all the water emanates from rainfall averaging about 1000 mm per annum. Analyses of the microalgae in two freshwater lakes showed that cyanophytes made up over 88% of the phytoplankton in the larger Lake Mgobezeleni and over 50% in the smaller Lake Shazibe. This raises concerns about the potential health risk to communities using this water for domestic, agricultural and recreational purposes. Microscope images showed the cyanophytes to be embedded in mucus. Next Generation Sequencing analysis of bacterial 16S rRNA genes showed a persistent cyanobacterial bloom in Lake Mgobezeleni, including cyanobacterial taxa closely related to species that are known to produce cyanotoxins, including Microcystis aeruginosa, which produces the hepatotoxin microcystin. Other less dominant potential cyanotoxin producers were detected in all the water bodies sampled. These results highlight the importance of identifying water systems at risk of experiencing cytotoxic cyanobacterial blooms and, most importantly, the need to monitor such vulnerable systems to ensure the safety of surrounding communities. Where the groundwater is being used by householders with boreholes, the nitrogen and phosphate concentrations were within South African drinking water quality standards but the presence of cyanophytes appears to indicate that the target environmental water quality standards published by the government are too high for this area.