Surface Water Discharge Research Articles

Key point of desert riparian forest development in the arid area: The response of phreatic water table depth to ecological water supply

Desert riparian forest vegetation maintains the fragile balance of ecosystems in extreme arid areas. Raising the phreatic water table through efficient ecological water supply is the key to the desert riparian forests in extreme arid areas. The main objective of this study is to explore an innovative framework in which the response of phreatic water table depth (PWTD) to ecological water supply flow (EWSF) can be effectively reflected. The framework is based on the computationally efficient integrated surface water - groundwater model (ISGWM), through which surface water processes, groundwater recharge and discharge processes, and PWTD changes under different EWSF can be accurately simulated. A large number of simulations were conducted to reflect the response of PWTD to EWSF, and to explore the suitable EWSF and its intra-annual process considering the efficiency of PWTD reduction. The applicability and advantages of ISGWM were evaluated for the Tarim River Basin (TRB), a typical inland river basin, northwest China. The response of PWTD to EWSF was studied in 55 gate control areas in the mainstream of TRB. The formulas of suitable EWSF of 55 gates with different initial PWTDs were fitted. It is more beneficial to concentrate the ecological water supply in flood season (Jun.-Oct.). Overall, the ISGWM can accurately describe the multi-process of surface water and groundwater interactions. This study can provide scientific support for water resources management and allocation in the TRB and other similar inland river basins.

Designing a biochar-based pretreatment method for distillery effluents entering constructed wetlands

Spent lees is an important distillation waste by-product created during whisky production, characterised by low pH and high dissolved copper (dissCu) content. Constructed wetland systems (CWs) are used in some Scotch whisky distilleries to treat spent lees prior to surface water discharge to prevent substantial environmental risks of spent lees in aquatic ecosystems, by buffering the acidic nature and decreasing the dissCu and organics content. However, as these wetland systems are biological communities (containing bacteria, fungi, plants, etc.), direct disposal of spent lees into CW ecosystems presents a challenge given its nature. This study investigates the efficacy of modified biochar (waste) sourced from whisky cask cooperage operations, as an effluent pretreatment method. The aim is to transform this raw biochar into NaOH-modified biochar, which will be capable of buffering the effluent pH and removing dissCu from spent lees before it enters CWs. To enhance raw biochar, NaOH modification and additional heat treatment were utilised which increased the alkalinity, heavy metal removal capacity and pH buffering potential. Experiments with 0.2% and 2% NaOH treated biochar demonstrated its treatment performance using a diverse range of spent lees samples with varying characteristics, including pH (4.1–4.4), dissCu concentrations (33.8–59.5 mg/L), and total organic carbon (685–754 mg/L). Column studies further supported the efficacy of the modified biochars, showing significant pH elevation and efficient dissCu removal (of 5.72 mg of Cu per g of biochar) when treating spent lees. This dissCu removal capacity compares favorably with other wood-derived biochars studied in the literature, which have reported between 2.75 and 7.44 mg/g. Surface characterisation techniques (EDX, XPS, FTIR, XRD) showed how the Cu ions microprecipitated on the modified biochar surface, validating its remediation potential. This study highlights the potential of biochar as a sustainable pretreatment solution for distillery effluents, paving the way for enhanced and more circular waste management practices within the Scotch whisky industry.

Sewage Treatment by Kolkata’s Natural Wetland System

The metropolis of Kolkata stands uniquely positioned to implement a natural sewage treatment paradigm through the utilization of waste stabilization ponds, specifically within the East Kolkata Wetlands (EKW). These shallow oxidation ponds harness solar irradiation and algae bacteria symbiotic processes to effectively treat incoming sewage. Concurrently, nutrient-rich effluents are assimilated through fish production, converting available nutrients into protein—a hallmark of nature-based treatment. A portion of raw sewage is used to cultivate a chunk of vegetables before treatment in fish ponds, and the reclaimed water after treatment is used for vegetable and paddy cultivation downstream. This investigation explains the delineation of a sewage flow system to EKW, a Ramsar-designated site. Substantively, it offers quantitative insights into the sewage volumes and quality undergoing treatment. The sewage flow is higher in the winter months (909.07 MLD) compared to the summer months (709.34 MLD). In general, the sewage from the Kolkata city flowing to the EKW is moderately polluted. Extensive scrutiny of sewage from pond inlets and outlets serves as a quantitative metric for evaluating treatment efficacy. EKW efficiently treats the sewage, demonstrating 59.1% Biological Oxygen Demand (BOD) removal and a 99.28% reduction in fecal coliform. The natural treatment system excels in removing ammoniacal nitrogen (80.38%) and phosphate (90%). The treated water’s quality along the EKW boundary, culminating at the Kulti Gong River discharge point, was systematically assessed. Analytical findings indicate that all measured concentrations in the treated water adhere to prescribed inland surface water discharge standards prescribed by the Central Pollution Control Board, India, barring a marginal elevation in BOD during winter. Evidently, the EKW system adeptly manages substantial sewage volumes, fostering efficient treatment while concurrently facilitating resource recovery through fish production, yielding economic dividends. Despite its substantial land footprint, preserving this inherently sustainable wastewater management paradigm is imperative.

Progressive melting of surface water and unequal discharge of different DOM components profoundly perturb soil biochemical cycling

Freeze-thaw (FT) events profoundly perturb the biochemical processes of soil and water in mid- and high-latitude regions, especially the riparian zones that are often recognized as the hotspots of soil-water interactions and thus one of the most sensitive ecosystems to future climate change. However, it remains largely unknown how the heterogeneously composed and progressively discharged meltwater affect the biochemical cycling of the neighbor soil. In this study, stream water from a valley in the Chinese Loess Plateau was frozen at –10°C for 12 hours, and the meltwater (at +10°C) progressively discharged at three stages (T1 ∼ T3) was respectively added to rewet the soil collected from the same stream bed (Soil+T1 ∼ Soil+T3). Our results show that: (1) Approximately 65% of the total dissolved organic carbon and 53% of the total NO3--N were preferentially discharged at the first stage T1, with enrichment ratios of 1.60 ∼ 1.94. (2) The dissolved organic matter discharged at T1 was noticeably more biodegradable with significantly lower SUVA254 but higher HIX, and also predominated with humic-like, dissolved microbial metabolite-like, and fulvic acid-like components. (3) After added to the soil, the meltwater discharged at T1 (e.g., Soil+T1) significantly accelerated the mineralization of soil organic carbon with 2.4 ∼ 8.07-folded k factor after fitted into the first-order kinetics equation, triggering 125 ∼ 152% more total CO2 emissions. Adding T1 also promoted significantly more accumulation of soil microbial biomass carbon after 15 days of incubation, especially on the FT soil. Overall, the preferential discharge of the nutrient-enriched meltwater with more biodegradable DOM components at the initial melting stage significantly promoted the microbial growth and respiratory activities in the recipient soil, and triggered sizable CO2 emission pulses. This reveals a common but long-ignored phenomenon in cold riparian zones, where progressive freeze-thaw can partition and thus shift the DOM compositions in stream water over melting time, and in turn profoundly perturb the biochemical cycles of the neighbor soil body.

Mining impacts peatland hydrology reducing discharge and water storage volumes

Peatlands cover about 3% of the Earth’s land surface, but are the largest terrestrial carbon store and are important for freshwater storage. In Australia, nationally protected peatlands (called upland swamps) exist in the catchment headwaters for Sydney’s drinking water supply. In this region, longwall mining of underground coal seams can result in subsurface fracturing, land subsidence, and, potentially, peatland drainage. This study presents the water balance modelling results for an upland peat swamp before and after it was undermined in 2020. Following a detailed field campaign, a conceptual lumped hydrology model was developed to estimate the local water balance, with a Nash Sutcliffe Efficiency of 0.85 for the modelled storage of the intact swamp. After undermining, the water balance of the swamp changed, with higher deep seepage rates and reduced surface water discharge rates. For the first time, these findings detail the hydrologic effects of longwall mining on peatland environments. Based on these findings, broader catchment management initiatives are recommended to prevent or limit further water extraction from upland swamps, including incidental water losses associated with subsidence.

Multi-objective double layer water optimal allocation and scheduling framework combing the integrated surface water – groundwater model

Balancing the water consumption of agricultural and ecological is the key point of sustainable social and economic development in an inland river basin. The growth of desert riparian forests in inland river basins mainly depends on a certain phreatic water table depth (PWTD). The main object of this study was to allocate and schedule water resources to regulate the PWTD and satisfy agricultural water demand. Therefore, a multi-objective double layer optimal allocation and scheduling framework based on the computationally efficient integrated surface water-groundwater model (ISGWM), which can simulate the surface water processes, groundwater recharge and discharge processes, and PWTD changes, was constructed and applied to the mainstream of Tarim River Basin (TRB). The top layer model of the framework is an optimal ecological water allocation model, and its optimal allocation results are used as the initial solution of the bottom layer model. The results show that under 5 different inflow frequencies, the agricultural water shortage rate is 0, 17.38 %, 17.41 %, 14.06 %, and 19.94 %, respectively. The PWTD regulation has a great performance. After the optimal scheduling, the proportions of good growth of the control area behind the gate under different inflow frequencies were 98.18 %, 98.18 %, 98.18 %, 90.91 %, and 94.55 %. Agricultural water shortage is mainly due to the non-uniformity distribution of intra-annual inflow and the lack of controlling hydraulic engineering. The regulation of PWTD can guarantee the growth of desert riparian forests on both sides of the mainstream of TRB. Besides, we explored the feasibility of exploiting groundwater to supplement agricultural water consumption. The groundwater exploitation should be controlled within the scope of not causing excessive increase of PWTD (difference between PWTD and target depth <1 m), due to the groundwater exploitation to supplement agricultural water will lead to the increase of PWTD. Overall, this framework, which regulates the PWTD with the change of ecological water supply based on the ISGWM, provides a new idea for the allocation and scheduling of agricultural and ecological water resources in arid inland river basins. It also provides a new method for the coupled cooperative operation of surface water and groundwater.

Phytoremediation of metals in oil sands process affected water by native wetland species

Process affected water and other industrial wastewaters are a major environmental concern. During oil sands mining, large amounts of oil sands process affected water (OSPW) are generated and stored in ponds until reclaimed and ready for surface water discharge. While much research has focused on organics in process waters, trace metals at high concentrations may also pose environmental risks. Phytoremediation is a cost effective and sustainable approach that employs plants to extract and reduce contaminants in water. The research was undertaken in mesocosm scale constructed wetlands with plants exposed to OSPW for 60 days. The objective was to screen seven native emergent wetland species for their ability to tolerate high metal concentrations (arsenic, cadmium, copper, chromium, copper, nickel, selenium, zinc), and then to evaluate the best performing species for OSPW phytoremediation. All native plant species, except Glyceria grandis, tolerated and grew in OSPW. Carex aquatilis (water sedge), Juncus balticus (baltic rush), and Typha latifolia (cattail) had highest survival and growth, and had high metal removal efficiencies for arsenic (81–87 %), chromium (78–86 %), and cadmium (74–84 %), relative to other metals; and greater than 91 % of the dissolved portions were removed. The native plant species were efficient accumulators of all metals, as demonstrated by high root and shoot bioaccumulation factors; root accumulation was greater than shoot accumulation. Translocation factor values were greater than one for Juncus balticus (chromium, zinc) and Carex aquatilis (cadmium, chromium, cobalt, nickel). The results demonstrate the potential suitability of these species for phytoremediation of a number of metals of concern and could provide an effective and environmentally sound remediation approach for wastewaters.

Quantitative and qualitative management of water resources with the use of treated wastewater in agriculture.

The principled utilization of treated wastewater can reduce the pollution load on the environment. Because on the one hand, treated wastewater can be a suitable fertilizer substitute, and on the other hand, using treated wastewater in irrigation prevents the discharge of polluted surface water into water sources. In the south of Tehran province, polluted surface water is used for irrigation in the agricultural sector, and this has led to environmental problems. To solve this problem, it has been decided to implement a plan to build surface water treatment plants and an irrigation and drainage network to transfer treated wastewater to farms. Therefore, the present study aimed to investigate the economic and environmental effects of this project in the region. A hydro-economic model has been used to achieve this goal. According to the results, in the case of the application of environmental constraints in the optimization model, the cultivation area and the farmers' profit will be reduced by about 5% and 36%, respectively, compared with the noncompliance of environmental constraints. However, this decline in profit can be compensated by adopting solutions such as improving the irrigation system, the application of treated wastewater, or using the fertilizer potential of water sources in the agricultural sector. PRACTITIONER POINTS: In the optimal economic-environmental situation, farmers' profit is reduced compared with the optimal economic situation. In the case of implementing the treated wastewater application, the farmers' profit will increase despite environmental constraints. In the optimal economic-environmental situation, fewer lands are cultivated with diverse crops than in optimal economic conditions.

Investigating the Hydrological Relationship between the North Taihang Tunnel and Tianshengqiao Nine Falls

The impact of a tunnel construction on the groundwater system depends on various parameters and cannot be easily predicted. Along these lines, a deep understanding of the hydrological relationship between tunnels and surface water is considered of vital importance for ensuring safety during railway construction. Upon completion, the North Taihang Tunnel will be one of four extra-long railway tunnels running through the natural ecotope and level-3 protection areas of the Tianshengqiao National Geological Park in Fuping County, Hebei Province. It will be 1 km away from the Tianshengqiao Nine Falls, which is known as a breathtaking landscape feature in Northern China. Local government, societies, and railway design units have raised concerns about whether the construction and operation of the North Taihang Tunnel will affect the Tianshengqiao Nine Falls. To effectively address this issue, in this work, hydrogeological mapping and hydraulic potential-energy calculations were performed in conjunction with hydrochemical and geological structure analyses. The groundwater system units in the study area were divided and the water source of the nine-level waterfall was determined retrospectively. In addition, the recharge of groundwater to the nine-level waterfall was calculated, the hydrogeological properties of the linear structure were analyzed, and the dominant channels of underwater discharge in surface water were compared and studied. The extracted results indicated that: (1) The Tianshengqiao Nine Falls represent a seasonal fall landscape, which is mainly supplied by surface water formed by precipitation and a low proportion of groundwater supply. (2) The water bodies of the North Taihang Tunnel project and Tianshengqiao Nine Falls belong to two independent groundwater systems. (3) No linear structure that connects these two groundwater systems has yet been discovered. It is widely accepted that a minor possibility of hydraulic connection might be present between the North Taihang Tunnel and Tianshengqiao Nine Falls. This work analyzed the water quantity of Nine Falls, determined the hydraulic relationship between the tunnel project and the waterhead of the Nine Falls, and addressed all stakeholder concerns. The conclusions could provide technological support for the scheduled construction projects.

Groundwater Recharge Assessment in Central Benin: The Case of the Collines Region (West Africa)

The objective of this study was to assess groundwater recharge in the hard-rock central region of Benin so as to compare it with the water needs of the local population. To reach this objective, we applied the Water Table Fluctuation (WTF) method, which requires long-term monitoring of groundwater level fluctuations. Groundwater level time series were used in combination with other data (including time series of surface water discharge and rainfall) to estimate groundwater recharge but also to shed further light on the relationship between surface water and groundwater. The results demonstrated that the minimum inter-annual groundwater recharge amount is about 1.09 × 109 m3, which is enough to cover the basic water needs of the local population. It should be highlighted that in sub-regions where the density of the population is high, water shortage can still occur with the above estimated groundwater recharge amount. This study has also illustrated that when applying the WTF method, sites with a highly uncertain specific yield can be detected.

Deterioration of dynamic fracture properties of granite under the coupled effects of hydrochemical solutions and freeze-thaw cycles

Fractured rock mass is a kind of complex rock mass widely existing in engineering projects, which is often subjected to erosion by different pH hydrochemical solutions such as surface water, acid rain, acidic and alkaline wastewater discharge, and deicing salts. When the rock project in a cold region suffers from the coupled effects of hydrochemical solutions and freeze-thaw (FT) cycles, the frost-heave-thaw-shrinkage characteristics of rocks are different from ordinary FT under dynamic loads, and the effect of FT cycles may be enlarged or reduced in different hydrochemical solutions. How to determine the effect of FT cycles on the expansion and changes of rock fractures, which is related to the safety and stability of many engineering rock masses in cold regions. In this study, the microstructure changes of specimens induced by hydrochemical solutions and cyclic FT were measured using nuclear magnetic resonance (NMR) and X-ray diffraction (XRD). The dynamic fracture tests were conducted using single cleavage triangle (SCT) granite specimens. Crack propagation gauge (CPG) was applied to examine crack propagation speed (CPS). The findings indicate that the mineral composition of the granite did not vary large with the hydrochemical solutions and FT cycles, but the maximum diffraction intensity of each mineral composition changed. For the granite under the coupling effect of hydrochemical solutions and FT cycles, the granite specimen in NaOH solution with 100 FT cycles has the highest dynamic fracture toughness and is 10.76 MPa·m1/2, dynamic fracture toughness of H2O, HNO3 and Na2SO4 solutions are only 0.94, 0.91 and 0.93 of that of NaOH solution. With increasing FT cycle times, the dynamic fracture toughness and crack speed decrease, whereas the porosity increases. For the specimen in NaOH solution and 100 FT cycles, dynamic fracture toughness decreased by 18.12 % without FT cycles and crack speed decreased by 34.18 %, the porosity increases by 26.42 %.

Exploring effects of carbon, nitrogen, and phosphorus on greywater treatment by polyculture microalgae using response surface methodology and machine learning

The microalgae-based wastewater treatment is a promising technique that contribute to achieving sustainable development goals (SDGs), such as SDG-6, “Clean Water and Sanitation”. However, it is strongly influenced by the initial composition of wastewater. In this study, the impact of initial organics and nutrient concentration on the removal of total organic carbon (TOC), total carbon (TC), ammonium (NH4+), total nitrogen (TN), and phosphate (PO43−) from greywater using native polyculture microalgae was explored. Response surface methodology was employed along with two machine learning approaches, AdaBoost and XGBoost, to evaluate the interactions among three main factors: TOC, NH4+, and PO43−, and their effects on treatment efficiency. The C/N ratios for achieving maximum TOC and TC removal efficiency of 99.2% and 97.7% were determined to be 10.3, and 65.4–73.6, respectively. Notably, the N/P ratio did not significantly affect their removal. The highest NH4+ removal efficiency, reaching 96.2%, was attained at C/N ratios of 4.3, 24.0, 38.2, and 212.9, coupled with N/P ratios of 0.3, 2.6, and 23.4. Highest TN removal efficiency of 77.2% was achieved at C/N and N/P ratios of 12.2 and 2.0, respectively. Highest PO43− removal of 78.8% was obtained at N/P ratio 12.8. However, C/N ratio did not affect the removal efficiency. Maintaining these specified C/N and N/P ratios in the influent greywater would ensure that the treated greywater meets the required standards for various reuse applications, including flushing, groundwater recharge, and surface water discharge. The integration of RSM with AdaBoost and XGBoost provided accurate predictions of removal efficiencies. For all the models, XGBoost had the highest R2, and lowest MAE and MSE values. The cross validation of RSM models with AdaBoost and XGBoost further reinforced the reliability of these models in predicting treatment outcomes.

Total Resource Circulation of Desalination Brine: A Review

AbstractDesalination brine is a concentrated stream that is generated during the desalination process. Brine commonly has high salinity and TDS (total dissolved ions), which contains ions such as Na+, K+, Ca2+, Mg2+, Cl−, SO42−, HCO3−, PO43−, and some critical elements. Currently, the brine treatment mainly applies direct disposal, like surface water discharge, sewer discharge, deep‐well injection, and evaporation ponds. However, these methods can cause harm to marine ecosystems, soil, and groundwater. Therefore, brine can be regarded as a resource to be reutilized. This work then aims to highlight the novel developments of brine application. For example, Na, Ca, and Mg in brine can be employed for carbon capture and utilization with ammonia, amines, and alkaline substances. With slight adjustment, brine can also be directly used as irrigation water, aquaculture water, and the activation of biochar. Furthermore, brine holds a higher concentration of critical elements, which makes many countries and scholars start to conduct element extraction, reducing the amount of ore exploitation. At last, the major obstacles related to these advancements in sustainability, expenses, and technological aspects are outlined, and promising research trends of brine reutilization are also suggested.

Effects of bed depths and the ratio of aerobic to anaerobic zone on the performance of horizontal subsurface flow macrophyte-assisted high-rate vermifilters treating synthetic brewery wastewater.

Effects of total vermibed depth, as well as the ratio of aerobic (the unsubmerged) to anaerobic (the submerged) zone on the performance of the horizontal subsurface flow macrophyte-assisted vermifilters (HSSF-MAVFs) treating synthetic brewery wastewater at a higher hydraulic loading rate (HLR), were investigated for the first time. Results showed that the HSSF-MAVF with a 50 cm total and 18 cm submerged vermibed depth yielded the optimum removal of the pollutants, ensuring a (91.2 ± 1.7)%, (81.8 ± 1.9)%, (67.4 ± 3.9)%, and (63.1 ± 2.3)% removal of chemical oxygen demand (COD), ammonium N (NH4 + -N), total N (TN), and organic N, respectively, whereas there was an increase of (142 ± 6.3)% in the effluent nitrate-N (NO3 - -N) than that in the influent. At the optimum condition, the effluent concentrations of all the pollutants including COD, NH4 + -N, NO3 - -N, TN, and organic N were well below the surface water discharge standards specified by the Central Pollution Control Board (CPCB), and thus, the effluent of the HSSF-MAVF could be safely discharged into the surface water bodies. PRACTITIONER POINTS: Total vermibed depth of HSSF-MAVFs was optimized for organic and nitrogen removal. HSSF-MAVFs were subjected to the higher HLR of synthetic brewery wastewater. Removal of COD and NH4 + -N was decreased with the increase in submerged bed depth. Removal of organic N and TN was increased with the increase in submerged bed depth. Total/unsubmerged bed depth had a positive impact on the organic and N removal.

Hyporheic exchange in a compound channel under unsteady flow: Numerical simulations

Hyporheic exchange (HE) within compound channels under unsteady surface water flow conditions plays an important role in the river-floodplain ecosystem. Numerical simulations were applied to investigate the HE in a compound channel under unsteady flow. High velocity regions were observed in the hyporheic zone near the banks of the floodplain and of the main channel, and the distribution of the pore water velocity in this region was seen to significantly change under the unsteady conditions. The velocity peaked during the rising and falling phases and had the smallest value when the inlet discharge of surface water had the maximum and minimum values. The changes in the relationship between surface groundwater recharge and discharge were observed in the context of a lateral water level threshold of approximately 1.2 m. About 75 % of the hyporheic exchange flux was due to the dynamic pressure. Comparing the hyporheic exchange in the compound channel driven by static pressure with that in a rectangular channel, it was found that the floodplain decreased the hyporheic exchange. These findings provide a better understanding of the HE driven by unsteady flow in a compound channel and may be applied in combined flood management and river ecological restoration.

Evaluation of physical and chemical characteristics of wastewater and sludge of Zahedan urban wastewater treatment plant for reuse

Following the water shortage in the world, the use of wastewater as a sustainable resource has been considered in large volume. The study conducted to evaluate the physical and chemical characteristics of the wastewater and sludge of the Zahedan urban wastewater treatment plant showed that the wastewater and sludge treatment system of the treatment plant has high efficiency and effectiveness in removing the investigated parameters. The investigated parameters in the effluent included Chemical oxygen demand (COD), Biochemical oxygen demand (BOD), and Total suspended solids (TSS), turbidity, temperature, nitrate, nitrite, phosphate, pH, zinc, cobalt, lead and copper. Also, the investigated parameters in the sludge included Mixed liquor suspended solids (MLSS), Mixed liquor volatile suspended solids (MLVSS), pH, electrical conductivity and heavy metals. The results showed that the average concentration of metals in the treated effluent is Zn > Mn > Cu > Pb > Ni > Cr > Cd ،and Chemical oxygen demand and Biochemical oxygen demand in the effluent of this treatment plant are on average 171 and 44.4 mg/L, respectively, and its discharge in surface water is limited, but it can be applied for agriculture. Also, the purified sludge had the necessary standards and could be used as soil or household fertilizer and compost for agricultural land.

The development of roadside green swales in the Chinese Sponge City Program: Challenges and opportunities

Roadside green swales have emerged as popular stormwater management infrastructure in urban areas, serving to mitigate stormwater pollution and reduce urban surface water discharge. However, there is a limited understanding of the various types, structures, and functions of swales, as well as the potential challenges they may face in the future. In recent years, China has witnessed a surge in the adoption of roadside green swales, especially as part of the prestigious Sponge City Program (SCP). These green swales play a crucial role in controlling stormwater pollution and conserving urban water resources by effectively removing runoff pollutants, including suspended solids, nitrogen, and phosphorus. This review critically examines recent research findings, identifies key knowledge gaps, and presents future recommendations for designing green swales for effective stormwater management, with a particular emphasis on ongoing major Chinese infrastructure projects. Despite the growing global interest in bioswales and their significance in urban development, China’s current classification of such features lacks a clear definition or specific consideration of bioswales. Furthermore, policymakers have often underestimated the adverse environmental effects of road networks, as reflected in existing laws and planning documents. This review argues that the construction and maintenance of roadside green swales should be primarily based on three critical factors: Wellthought- out road planning, suitable construction conditions, and sustainable long-term funding. The integration of quantitative environmental standards into road planning is essential to effectively address the challenge of pollution from rainfall runoff. To combat pollution associated with roads, a comprehensive assessment of potential pollution loadings should be carried out, guiding the appropriate design and construction of green swales, with a particular focus on addressing the phenomenon of first flush. One of the major challenges faced in sustaining funds for ongoing maintenance after swale construction. To address this issue, the implementation of a green finance platform is proposed. Such a platform would help ensure the availability of funds for continuous maintenance, thus maximizing the long-term effectiveness of green swales in stormwater management. Ultimately, the findings of this review aim to assist municipal governments in enhancing and implementing future urban road designs and SCP developments, incorporating effective green swale strategies.

Predicting wastewater treatment plant influent in mixed, separate, and combined sewers using nearby surface water discharge for better wastewater-based epidemiology sampling design

For wastewater sample collection approaches supporting public health applications, few high hydrologic activity normalizing guidelines currently consider readily available environmental flow data that may earlier capture information regarding periods of influent mixing and dilution of wastewater with groundwater and runoff. This study aimed to identify wastewater sampling rules for high hydrological activity events, allowing for an earlier decision point in the control of dilution before sample collection. We defined the sampling rules via data-driven models (Random Forest and linear regression) using environmental data (i.e., wastewater treatment facility influent rates, nearby stream discharge flow, and precipitation). These models were applied to five treatment plants in Jefferson County, Kentucky (USA) in mixed, separate, and combined sewers with different population sizes. We proposed cutoffs of 10 %, 25 %, and 50 % flow conditions for orientation towards public health samples. The results showed a strong nonlinear relationship between nearby stream discharge and treatment facility flow rates, which was used to infer the hydrological conditions that produce high volumes of diluted wastewater in the sewer system. Accumulated Local Effects and SHapley Additive exPlanations aided in deciphering the relationship between the predictors and response variables of the Random Forest models. The influent rate to the treatment plant from the previous day and two USGS stream gages were needed to adequately predict the degree of infiltration and inflow mixing on a given day. Surface water discharge data can be used to provide an earlier workflow decision point during wet weather periods to improve understanding of flow conditions for wastewater-based epidemiological studies to inform laboratory analysis and data interpretation. Not only total flow, but also the specific proportions of infiltration and inflow to wastewater volume in influent should be considered when analyzing data for normalization purposes, and our method provides a starting point for doing so rapidly and at low cost.

Water quality characteristics of Lake Tanganyika in Burundi and Lake Victoria in Uganda

Abstract Water is necessary for all biological life and industrial, municipal, agricultural, and residential processes. It is challenging to imagine living without water. Unfortunately, human and natural activities are causing the sources of useable water to become contaminated. Despite having enormous and unique natural water resources, Africa has experienced unprecedented environmental pollution because of the abuse of these resources. Additionally, population increase and urbanization brought by technological advancements have significantly worsened water pollution in Africa. The significant causes of pollution for surface waterways are untreated effluents released into the environment by humans and machines. It is still being determined if the emission goals set by several African countries for surface water discharge have been fulfilled. Wells and boreholes are essential sources of drinking water for Africans. However, because of their location in sterile areas, the natural water quality of these groundwater sources could be better. The primary sources of water pollution in Africa include agricultural activities, mining, roadside discharges, trash from companies and workshops, landfills, and e-waste. Oil leaks are a severe problem in oil-rich African countries. Lake Tanganyika is East Africa's most significant freshwater reservoir, while Lake Victoria is the second-deepest lake in the world.

Tracing surface water pollution in China’s supply chain

Decades of economic growth in China were enabled by rapid industrialization with insufficient water quality controls. Previous studies have traced water pollution discharges or grey water footprint using the multi-regional input–output (MRIO) model. However, there is a research gap in understanding the relation between surface water pollutant concentrations and final consumption of local and external basins. Here, we present the first national analysis to map surface water quality degradation in watersheds embedded in China’s supply chains. To do this, we developed a basin-specific relationship between surface water pollution concentration and discharge, and combined it with the MRIO model to trace the water pollution of different basins through the trade of products and services. We find that ∼50% chemical oxygen demand (COD) and ∼46% ammonium nitrogen (NH4+-N) discharges from production processes can be traced to consumer demands beyond the basin where the pollution was initially released. 0.3–2.2 mg/L COD and 0.03–0.31 mg/L NH4+-N water quality degradation (the range indicates pollution concentration in different basins) can be attributed to final consumption of commodities from other basins in China. International consumers contributed to increased degradation of water quality (0.43 mg/L COD in Huai River Basin and 0.07 mg/L NH4+-N in Hai River Basin). High pollution concentrations were often concentrated in dry North China, because water scarce basins in this region are more susceptible to human pollution loadings. Basins outsourcing water pollution were mainly developed economies that outsourced production and subsequent water quality impairments to other basins. This study highlights the interactions between water quality and supply chains.