Greywater Research Articles

Analysis and prediction of crop water footprints in the Fen River Basin of Shanxi Province, China

In China, the major water user is agriculture. Under the background of climate change and with the pressure of scarce water resources, the study of crop water footprints serves as a theoretical basis for regional optimization of water resource management, fine-tuning crop planting structures and actively addressing the negative impacts of climate change on agricultural production, among other critical issues. Leveraging meteorological and agricultural data, we employed Taiyuan which is situated in Fen River Basin as our focal research subject and calculated and analyzed the water footprint variations concerning six major food crops—wheat, corn, grain, sorghum, soybean, and potato—from 2000 to 2020. Through meticulous examination, we identified the predominant contribution of blue water (45 %) to the total water footprint, followed by green water (39 %), with grey water playing the smallest role (16 %), indicating that the use of water for crops in the Fen River Basin mainly consumes surface water and groundwater. Our investigation reveals a complementary association between blue water and green water, while both blue water and grey water exhibit an overall declining tendency from 2000 to 2020. Moreover, our predictive modeling of food crop water footprints, considering various SSPs-RCPs scenarios refered from IPCC, points towards a peak within the coming 10–20 years, with a growth rate of 16.2 % to 33.0 %, followed by a subsequent decline. Particularly, in SSP3-7.0 scenario, the water footprint of food crops presents the highest, with a growth rate of up to 33.0 % because of the continuous growth of population and the increase of crop sowing area, while in SSP1-2.6 scenario, the water footprint of food crops shows the lowest, with a growth rate of 16.2 % because of the decrease in population and crop sowing area, before the middle of the current century.

Assessing greywater characteristics in the sahel region and perception of the local population on its reuse in agriculture

Research on greywater reuse in water stressed areas is in full swing. However, the perception of greywater reuse is one of the least researched areas in West Africa, particularly in Sahelian countries. This study aimed to fills a significant gap in the existing literature, which has largely ignored the specific socio-demographic contexts of developing countries in the Sahelian regions. The study involved in-depth interviews with 240 rural households and the collection of 40 greywater samples in four locations for laboratory analysis. The survey focused on greywater management and household perceptions of greywater reuse in agriculture. The analyses focused on determining the physico-chemical and microbiological parameters of greywater collected from households. The results showed that over 80 % of households discharged greywater into the natural environment without prior treatment. The majority of respondents were aware that poor greywater management poses a health risk. The results also showed an association between locality, gender, education level and perceptions of poor grey water management. Respondents were willing to accept the reuse of greywater in agriculture, to consume irrigated vegetables and to install a greywater treatment system. The quality analysis showed that the greywater was not in compliance with the legal discharge limits. This study highlights that in order to promote sustainable greywater management practices within households, it is important to design effective greywater treatment systems that meet the needs of the target population. Awareness campaigns, education and training programmes on wastewater management could also be established.

The effect of chemical oxygen demand of domestic wastewater on workability, mechanical, and durability of self- compacting concrete

Due to worldwide water scarcity, especially in arid regions, and the substantial use of drinking water in concrete production, the consideration of gray water usage is growing. However, wastewater contamination adversely affects concrete's mechanical strength and durability, with Chemical Oxygen Demand(COD) as one of the indicator. In the present work, the effect of COD of different types of domestic wastewater on workability, mechanical, and durability properties of self-compacting concrete (SCC) with 400 kg/m3 and 440 kg/m3 of cement, and water-to-cement ratios of (w/c) 0.36 and 0.5 for 12 different SCC mixture designs were investigated. The results of the experiments indicated that increasing the COD of domestic wastewater negatively impacts the workability of fresh concrete. Additionally, as the COD of the wastewater increases, the compressive strength of SCC decreases at 7 and 28 days when using raw sewage, sewage sludge, and artificial wastewaters. However, by 90 days, the compressive strength showed no significant difference compared to SCC made with tap water. With increasing COD of wastewater, the 28-day tensile strengths of SCC decreased by 6–10 %. The COD of wastewater did not significantly affect the flexural strength. However, the fracture toughness, at a water-cement ratio (w/c) of 0.5, decreased with increasing COD, reaching a reduction of 36 % at a COD of 940 mg/L. As the COD concentration rises, water absorption increases. In SCC samples containing sludge water and raw sewage, capillary water absorption was at its maximum due to the presence of impurities, as well as organic and mineral materials.

Electrophoretically deposited TiO2 layers for efficient photocatalytic degradation of antibiotic mixture in greywater

Efficient removal of pharmaceuticals from greywater is crucial to enable its application for non-potable use. TiO2 photocatalysis is a promising environmentally friendly way of streamlining their complete degradation. However, dispersed TiO2 nanopowders are unsuitable for greywater treatment procedures because they require separation and may aggregate, thereby losing photocatalytic activity. Thus, TiO2 nanopowders (anatase 5 and 100 nm, AEROXIDE® P 25) were immobilized into layers by quantitative electrophoretic deposition. The layer ability to degrade the commonly used antibiotics ampicillin and sulfathiazole in deionized water was monitored using HPLC-PDA analysis and compared with that of the respective nanopowders. All layers attained total conversion of the initial antibiotics (limit of detection 50–100 μg L−1) with the highest degradation rate constant corresponding to 66 × 10−4 min−1 for AEROXIDE® P25 layer. To evaluate the efficiency of the prepared layers under more realistic conditions, collected greywater was treated in a membrane bioreactor, spiked with an equimolar antibiotic mixture, and subjected to photocatalysis. The overall reaction rate constants were calculated as 54, 15 and 75 × 10−4 min−1 for 5 and 100 nm anatase and AEROXIDE® P25 layers, respectively; the best-performing layer achieved complete removal and 68 % total mineralization of the antibiotic mixture in greywater within 7 and 24 h, respectively. For this layer, the developed regeneration method recovered min. 94 % of the original photocatalytic activity, enabling its reusability. These results suggest that our presented deposition method provides layers capable of degrading antibiotic mixtures in greywater effectively and is suitable for upscaling due to its low cost and simplicity.

Investigation of water and carbon footprint reductions employing best available techniques in the textile sector

This study includes a new approach in terms of connecting best available technique (BAT) selection/decision to water and carbon footprint evaluations in addition to economical and environmental performance criteria. This new approach was applied to an integrated textile facility mainly employing cotton fabric finishing and printing-dyeing. After potential implementation of selected 12 BATs, the reduction potentials in the existing water/carbon footprints were calculated. The blue water, grey water and total water footprint values of the facility were found to be 126, 837 and 963 L/kg product, respectively. The total carbon footprint value of the facility was found to be 7.011 kg CO2eq/kg product, and most of this comes from steam use. The optimization of resin regeneration frequency/duration and washing-rinsing steps in the water softening system via online hardness sensors provides 20–30% reductions in blue water footprint values. It was calculated that when BATs from 1 to 7 together are implemented in the facility, an average of 68.5% reduction in the total water footprint could be achieved. Alternatively, when BATs 1–5 and 8 are implemented, such reduction is 45.6%, highlighting the effectiveness of the selected BATs. BAT 9 exhibited the highest reduction in total carbon footprints due to the fact that it is related to minimization of energy losses. If all selected BATs are to be implemented in the facility, a reduction of 1.179 kg CO2eq/kg product could be achieved in the total carbon footprint, corresponding to 16.8% reduction. Significant reductions in energy consumption could be achieved through techniques/applications such as isolation of hot surfaces, reducing reprocesses by improving dyehouse-laboratory coordination, optimizing recipes and applying correct dyeing techniques at once, making lighting systems efficient, process modifications/optimizations in pre-treatment and final finishing processes, and reducing water consumption in processes requiring hot water. This study indicated that selection and application of BATs in industries should be coupled with water/carbon footprint evaluations.

Determination of the WQI Index to Evaluate the Water Quality of the Monjas River located in Quito

The study of water quality is important over time because it is an essential element for human beings, it has been vital for their survival, territorial expansion, and socioeconomic development. The water of the Monjas river present contamination issues, mainly due to human activities such as agriculture, animal husbandry, and gray water discharges that alter their chemical, biological, and physical properties. The purpose of this research is to evaluate whether the water conditions are suitable for agricultural use, applying the Water Quality Index (WQI) methodology, which requires a study in the laboratory for fecal coliforms, dissolved oxygen, pH, biological demand for oxygen, nitrates, phosphates, dissolved solids, turbidity, and temperature. Samples were taken at six sampling points along the riverbed. Results were compared with the parameters described by TULSMA (Texto Unificado de la Legislación Secundaria de Ministerio de Ambiente), and FAO (The Food and Agriculture Organization of the United Nations) environmental regulations. Higher values were obtained for fecal coliforms, and biochemical oxygen demand that exceeded the maximum permissible limits with respect to the rest of the parameters examined. In this study, the WQI ranged from 26 to 50, classifying the water quality of the Monjas river as unsuitable. It implies that it is not appropriate for agricultural use due to the contamination that it could cause to the crops. The main reasons for this could rely on the presence of fecal matter of human, and animal origin, fertilizers, pesticides, and household waste.

Spatiotemporal evolution characteristics and influencing factors of the crop water use efficiency in watersheds based on the water footprint.

Climate change has exacerbated the contradiction between water scarcity and sustainable agricultural development. Assessing the crop water use efficiency and its influencing factors could provide a decision-making reference to realize Sustainable Development Goal 2. By analyzing the temporal and spatial evolution characteristics of the crop water footprint, the blue water footprint, green water footprint, and grey water footprint were introduced into the super efficiency slack-based measure model to evaluate the crop water use efficiency in basins. The influence of the driving factors was examined by using the geographic detector model. The situation in the provinces along the Yellow River Basin from 2005 to 2020 was used as a verification case. The results indicated that (1) during the study period, crop water use in the basin was mainly based on the blue water footprint, accounting for approximately 55% of the total water footprint, the grey water footprint, accounting for approximately 30% of the total water footprint, and the green water footprint, accounting for the lowest proportion, at approximately 15%. (2) The crop water use efficiency exhibited a spatial distribution pattern of high values in the east and low values in the west, with obvious upstream provinces<midstream provinces<downstream provinces regional characteristics. (3) The driving factors of crop water use efficiency changes could be ranked as follows: effective irrigation rate (0.75) > disposable income of rural residents (0.71) > population urbanization rate (0.65) > degree of agricultural mechanization (0.63) > agricultural disaster rate (0.61). Furthermore, the interaction effects between the driving factors were greater than the effects of the single factors. The study provides an important reference for understanding the changes, driving mechanisms, and impacts of crop water use efficiency in basin areas. It promotes green agricultural transformation and development to address climate change and alleviate the pressure on water resources.

Pilot scale demonstration of an underground biological aerated filter for rural wastewater treatment in a protected area

The availability of land is one of the advantages of rural wastewater treatment. However, this advantage may be absent in protected areas. The objective of this study is to showcase pilot-scale wastewater treatment approaches specifically tailored to address challenges presented by these unique circumstances. The demonstration case presented here involves a rural campsite where ground works are restricted. A pilot-scale decentralized system that includes a rainwater recycling system for potable water production (2–3 m3/d) and an underground biological aerated filter for wastewater treatment was installed. The biological aerated filter was built under a parking area (a so-called Phytoparking® system) and did as such not use additional ground surface. The Phytoparking with an area of 44 m2 was operated for 7 months and a total of 220 m3 grey water and 127 m3 black water was treated. Good pollutants removal efficiency was achieved for total suspended solids (93 %), COD (93 %), NH4+-N (93 %), TP (99 %), E.coli (log reduction 4.3) and total coliforms (log reduction 2.4). The potential wastewater reuse is not only about technological concern but also social acceptable concern. Therefore, the campsite customers' acceptance level of this system and the reused water were surveyed by a questionnaire. Based on the results of the study's pollutant removal efficiency and questionnaire responses, it can be concluded that local and/or decentralized water treatment and reuse systems were perceived positively.

LAHAN BASAH BUATAN UNTUK PENGOLAHAN AIR LIMBAH GREY WATER MENGGUNAKAN SALVINIA ROTUNDIFOLIA

Household wastewater consists of 80% grey water and 20% black water. The decline in water quality can have adverse impacts on well-being. Constructed wetland is an engineered system designed to harness the ecological principles of natural wetlands to address water pollution issues. The Free Water Surface system within the constructed wetland involves the flow of water on the surface. An appropriate plant example for use in a constructed wetland is Salvinia rotundifolia. Plant acclimatization was carried out for 12 days. The reactor operation continued for 12 days using a continuous system. The percentage removal of parameters in the constructed wetland reactor were as follows: COD 23.40-84.38%, BOD 37.93-72.73%, TSS 43.24-85%, phosphate 59.47-65%, and nitrate 10.99-31.08%. The values of areal removal rate constant (kA) and volumetric removal rate constant (kV) for the constructed wetland reactor were as follows: for COD, 1.48-3.75 m/day and 0.80-22.28 /day; for BOD, 1.70-3.73 m/day and 1.43-15.59 /day; for TSS, 2.11-8.83 m/day and 1.70-22.77 /day; for phosphate, 1.40-6.61 m/day and 2.89-11.20 /day; and for nitrate, 0.18-2.32 m/day and 0.58-1.54 /day. This study demonstrates that the constructed wetland reactor with Salvinia rotundifolia plants achieves removal efficiencies of up to 85%, thus meeting the standards set by the Minister of Environment and Forestry Regulation No. 68 of 2016 regarding Domestic Wastewater Quality Standards.

Exploring biochar and Moringa oleifera seed proteins for greywater remediation on small farms

This study investigated the potential of using biochar and Moringa oleifera seed proteins for sustainable greywater treatment in rural Kenya. Greywater samples from washing clothes were collected from households in the Kenyan counties of Kwale and Siaya. Two treatment methods, batch stirring and filtration, were used to assess the effectiveness of using biochar and Moringa oleifera seed protein extract together to treat greywater at a household level. Both methods achieved a significant reduction in contaminants: colour was reduced by up to 43% in Kwale and 67% in Siaya, turbidity decreased by 91–98%, and surfactant levels were lowered by 89–93%. There were increases in total organic carbon and total dissolved solids post-treatment, but both methods effectively reduced levels of phosphates, nitrates and iron. This research highlights the potential of using locally available materials for greywater treatment and provides insights into sustainable water management nature-based solutions in the Global South.

Wastewater and Grey Water Footprint Assessment of the Olive Oil Production Process in Northwest Argentina

Argentina stands as the leading producer and exporter of olive products in the Americas, with the province of La Rioja as its main productive area. Since the 1990s, the olive grove cultivated area and related agro-industry in La Rioja have expanded. However, the resulting wastewater has generally been neglected. The water footprint (WF) provides information about the water volume consumed and polluted by a production process. Since the 1990s, agricultural and agro-industrial activities in La Rioja have experienced substantial growth. This study aims to analyze the generation, quality, and management of Oil Mill Wastewater (OMWW) using the grey WF of chloride and nitrate as an indicator and focusing on two olive mills (OM) in La Rioja. Additionally, it seeks to examine the relationship between the international trade of provincial olive oil and the estimated grey WF. For the diagnosis of OMWW generation, a description of the production process was made coupled with flow and physico-chemical characterization. The total grey WF was 8.69 and 45.5 L water/L olive oil for OM 1 and OM 2, respectively. Nitrate was identified as the critical pollutant. The grey virtual water export related to the export of olive oil was 5569 m3 for OM 1 and 28,000 m3 for OM 2. The provincial grey virtual water export related to olive oil was 161,955 m3 with major trade destinations including Spain, the United States, and Brazil. The article analyses for the first time the grey WF of olive oil industries and assess the related grey virtual water exports. This research represents a step forward in the knowledge of wastewater management in the olive oil sector and facilitates the search for solutions to minimize negative environmental impacts while promoting cleaner production.

Managing the kinetic energy of descending greywater in tall buildings and converting them into a valuable source

Harnessing energy from descending greywater (GW) in tall buildings (TBs) is an innovative concept that combines water management with renewable energy generation and applying simulation methods. This study proposes a novel approach to enhancing sustainable energy recovery in TBs by capitalizing on the kinetic energy inherent in descending GW. Greywater, derived from non-toilet fixtures such as showers, bathroom sinks, and washing machines, offers a readily accessible source of potential energy due to its gravity-driven flow through the plumbing system. This gravitational potential energy could feasibly be converted into useable electricity through the incorporation of specialized energy-recovery mechanisms, such as turbines, hydroelectric generators, and piezoelectric devices. The study addresses the technical, economic and environmental aspects of implementing this idea in TBs. It describes the challenges of system integration, maintenance requirements and adherence to regulatory standards, as well as the potential benefits in terms of water conservation and reduced reliance on conventional energy sources, through a comprehensive analysis encompassing modeling, experimental validation and feasibility assessments. The research offers insights into the potential viability of harnessing downward-flowing GW as an alternative and sustainable green energy resource.

Assessing the Gray Water Footprint Impact of Pesticide Use in Tommy Atkins Mango Cultivation: A case study in the Semi-Arid Region of São Francisco Valley, Brazil

Mango production, particularly of the Tommy Atkins variety, is prominent in the São Francisco Valley region of Northeast Brazil due to favorable conditions and year-round cultivation facilitated by irrigation and growth regulators. However, concerns arise over its significant water footprint and heavy pesticide usage, prompting a study on the gray water footprint of pesticides applied to Tommy Atkins mangoes in Sub-middle São Francisco Valley-Pernambuco, Brazil. Utilizing models by Hoekstra et al. (2011) and Paraiba et al. (2014), the study estimated the Gray Water Volume (GWV) and assessed potential water contamination using the GUS Index and GOSS method. Results suggest minimal groundwater pollution risk but moderate surface water contamination risk. The GWV ranged from 106 to 107 m3 ha-1, with the model of Paraiba et al. (2014) showing higher environmental sustainability due to considering toxicity to aquatic non-target organisms. Despite this, both models indicate a high gray water footprint. The pesticide ranking derived from these findings can aid in selecting environmentally safer pesticide mixtures for mango cultivation, aiming to balance water protection and agricultural productivity.

Crop grey water footprints in China: The impact of pesticides on water pollution

Agricultural water pollution is a significant challenge in China, a rapidly growing economy with a large agricultural sector. The grey water footprint (WF) is a tool for evaluating freshwater pollution. It expresses pollution in volumetric units identifying the pollutant that theoretically needs most water to be diluted to accepted water quality standards. Previous agricultural grey WF studies focused on nitrogen (N) and phosphorus (P), some studies included pesticides. This study assesses grey WFs based on N, P and 1513 pesticide combinations for twelve main crops and two crop categories in 31 Chinese provinces. Grey WFs, including the pesticide component, are far larger than estimated before, dominating total agricultural WFs (green, blue, and grey). The total grey WF of Chinese agriculture (4,900 109 m3 year−1) is determined by pesticides, while grey WFs related to N and P are 450 and 1,500 109 m3 year−1, differences of a factor of eleven and three respectively. The provinces Heilongjiang, Inner Mongolia, Hebei, Henan, and Shandong are hotspots contributing 37 % to the total grey WF. A limited number of pesticides used for maize, vegetables, fruits and potato (Mancozeb a fungicide, Acetochlor a herbicide and Cypermethrin an insecticide) dominate total grey WFs, contributing 80 % to the total grey WF. Eliminating the most polluting pesticides per category and redistributing the remaining ones with a similar function but lower grey WFs reduces national water pollution from agriculture by 64 %. Only five crops, i.e. maize, potato, soybean, rice and wheat, and the two crop categories, vegetables and fruits, contribute 94 % to this reduction. Probably grey WFs could reduce even further with a second elimination and redistribution effort. This study is the first national grey WF assessment related to pesticides in agriculture. It offers valuable insights to farmers and policymakers to enhance water quality in China and beyond.

Evaluation of residual sodium carbonate (RSC) and sodium adsorption ratio (SAR) in fresh water and laundry grey water for irrigation usage

AbstractThe current study was carried out to assess the suitability of laundry grey water (LGW) for reuse in irrigation so that it can help in the reduction of freshwater stress in irrigation sector. To address this objective, concentration of sodium (Na+), calcium (Ca2+), magnesium (Mg2+), carbonate (CO32−), bicarbonate (HCO3−), and phosphate (PO43−) were tested in fresh water (FW) collected before laundry washing and LGW generated after laundry washing from different households. The suitability of LGW for irrigation purpose was determined by using water quality indices such as Sodium adsorption ratio (SAR) and Residual Sodium Carbonate (RSC). The SAR values of FW at the rural and urban area sites varied from 0.84 to 1.10 and 0.82 to 4.30 respectively and remained in the excellent category for irrigation purpose. The SAR values of LGW at the rural and urban sites varied from 10.06 to 13.01 and 6.26 to 9.68, respectively. In contrast to the SAR values of the LGW at rural site, which remained under good quality category, SAR values remained under excellent category for irrigation purpose at urban sites. RSC values of FW and LGW were below 3.97 showing low or medium hazards associated with it for irrigation.

Low-Cost Grey Water Treatment System Design And Treatability Studies In Relation To Recycling And Reuse In Rural Area of Angul District of Odisha

As global water scarcity intensifies, there is a growing need for sustainable water management solutions, particularly in rural areas where access to clean water is often limited. This study focuses on the development of a low-cost greywater treatment system tailored for rural settings, emphasizing the recycling and reuse of greywater. The research encompasses the design, implementation, and treatability studies of the proposed system, aiming to provide an affordable and effective solution for improving water sustainability in resource-constrained communities. The designed greywater treatment system incorporates cost-effective technologies and locally available materials to ensure its feasibility in rural contexts. The treatability studies explore the system's efficiency in removing contaminants commonly found in greywater, evaluating its potential to meet water quality standards suitable for various non-potable applications. Emphasis is placed on the system's adaptability to local conditions, promoting community engagement and ownership for long-term sustainability. By addressing the unique challenges faced by rural areas, this research contributes to the broader goal of achieving water security through decentralized, affordable, and environmentally conscious greywater treatment solutions. The findings from this study can inform policymakers, engineers, and local communities on practical approaches to enhance water quality, reduce environmental impact, and promote water recycling and reuse in rural settings.

Synthetic greywater treatment using a scalable granular activated carbon bioelectrochemical reactor

Greywater reuse has emerged as a promising solution for addressing water shortages. However, greywater needs treatment before reuse to meet the required water quality standards. Conventional wastewater treatment technologies are unsuitable for recreating highly decentralized domestic greywater. This study evaluated bioelectrochemical reactors (BERs) with granular activated carbon (GAC) as a sustainable alternative for developing decentralized and low-cost biological treatment systems. BERs using GAC as the anode material and conventional GAC biofilters (BFs) for synthetic greywater treatment were operated in batch mode for 110 days in two stages: (i) with polarized anodes at −150 mV vs. Ag/AgCl and (ii) as a microbial fuel cell with an external resistance of 1 kΩ. Anode polarization produced an electrosorption effect, increasing the ion removal of the BERs. Power production during the operation and cyclic voltammetry tests of the extracted granules revealed electrochemically active biofilm development on the BERs. Although low power density (0.193 ± 0.052 µW m−3) was observed in BERs, they showed a similar performance in sCOD removal (BER = 91.6–89.6 %; BF = 96.2–93.2 %) and turbidity removal (BER = 81–82 %; BF = 30–62 %) to BFs that used 50 % aeration. Additionally, scanning electron microscopy of sampled granules showed higher biomass formation in BER granules than in BF granules, suggesting a higher contribution of sessile (vs. planktonic) cells to the treatment. Thus, the results highlight the synergistic removal effect of the GAC-based BER. The scalable design presented in this study represents a proof-of-concept for developing BERs to use in decentralized greywater treatment systems.

Environment-food nexus in trout ponds: a developed index by combining grey water footprint and life cycle assessment

Environment-food nexus in trout ponds: a developed index by combining grey water footprint and life cycle assessment

Phytoremediation of Grey Water

Greywater, generated from domestic activities excluding toilet waste, presents a significant challenge for water management due to its diverse contaminants and potential environmental impact. Conventional treatment methods often fall short in addressing the complex composition of greywater while maintaining sustainability. Phytoremediation, a green technology that utilizes plants and their associated microorganisms, offers a promising and ecofriendly alternative for greywater treatment. This paper reviews the principles, mechanisms, and applications of phytoremediation in the context of greywater treatment. Various phytoremediation techniques such as rhizofiltration, phytoextraction, and phytodegradation are discussed, highlighting their efficacy in removing pollutants such as organic matter, nutrients, pathogens, and heavy metals from greywater. The role of specific plant species with remediation potential and their physiological mechanisms in contaminant uptake and transformation are examined. Case studies and experimental findings from greywater phytoremediation projects around the world are presented to demonstrate the practicality and effectiveness of this approach. Factors influencing phytoremediation performance, including plant selection, hydraulic conditions, nutrient availability, and system design, are analysed to optimize greywater treatment efficiency.

Revealing neglected hotspots for China’s quality-induced water scarcity

A dependable assessment of quality-induced water scarcity (QualWS) is essential for tackling the issue and achieving sustainable development goals. The conventional Emission-based grey water footprint (GWF) may over- or under-estimate QualWS, as it solely focuses on local pollutant emissions while disregarding other influential factors, such as water body self-purification capacity, transboundary water flows and the potential under- or over-estimation of water pollution emissions. To address this limitation, we propose the State-based GWF to reflect the quality status of local water resources accurately. The indicator is applied in annual and monthly QualWS assessments at the provincial scale in China. In 2021, 19 provinces were identified as QualWS hotspots, comprising seven moderate and 12 slight hotspots for at least one pollutant. Notably, the State-based assessment revealed eight previously overlooked hotspots undetected by conventional methods. Furthermore, total phosphorus emerged as the most critical water pollutant, followed by total nitrogen and chemical oxygen demand. Our assessment presents an innovative perspective for understanding QualWS and establishes a scientific basis for effective aquatic environment management.