Greywater Sources Research Articles

Greywater recycling for diverse collection scales and appliances: enteric pathogen log-removal targets and treatment trains

In light of increasingly diverse greywater reuse applications, this study proposes risk-based log-removal targets (LRTs) to aid the selection of treatment trains for greywater recycling at different collection scales, including appliance-scale reuse of individual greywater streams. An epidemiology-based model was used to simulate the concentrations of prevalent and treatment-resistant reference pathogens (protozoa: Giardia and Cryptosporidium spp., bacteria: Salmonella and Campylobacter spp., viruses: rotavirus, norovirus, adenovirus, and Coxsackievirus B5) in the greywater streams for collection scales of 5-, 100-, and a 1000-people. Using quantitative microbial risk assessment (QMRA), we calculated LRTs to meet a health benchmark of 10-4 infections per person per year over 10’000 Monte Carlo iterations. LRTs were highest for norovirus at the 5-people scale and for adenovirus at the 100- and 1000-people scales. Example treatment trains were designed to meet the 95% quantiles of LRTs. Treatment trains consisted of an aerated membrane bioreactor, chlorination, and, if required, UV disinfection. In most cases, rotavirus, norovirus, adenovirus and Cryptosporidium spp. determined the overall treatment train requirements. Norovirus was most often critical to dimension the chlorination (concentration × time values) and adenovirus determined the required UV dose. Smaller collection scales did not generally allow for simpler treatment trains due to the high LRTs associated with viruses, with the exception of recirculating washing machines and handwashing stations. Similarly, treating greywater sources individually resulted in lower LRTs, but the lower required LRTs nevertheless did not generally allow for simpler treatment trains. For instance, LRTs for a recirculating washing machine were around 2-log units lower compared to LRTs for indoor reuse of combined greywater (1000-people scale), but both scenarios necessitated treatment with a membrane bioreactor, chlorination and UV disinfection. However, simpler treatment trains may be feasible for small-scale and application-scale reuse if: (i) less conservative health benchmarks are used for household-based systems, considering the reduced relative importance of treated greywater in pathogen transmission in households, and (ii) higher log-removal values (LRVs) can be validated for unit processes, enabling simpler treatment trains for a larger number of appliance-scale reuse systems.

Impact of Filtration on Grey Water Quality: A Comprehensive Analysis of Christian Hospital Taxila's Grey Water before and after Treatment

Grey water, defined as wastewater excluding toilet effluents, contains varying levels of contaminants and necessitates precise reuse strategies. This study focuses on the treatment of grey water sources with relatively lower levels of contaminants, specifically excluding those from toilets which contribute the majority of harmful substances such as chemicals, body lipids, and oils. The study evaluated the physical, chemical, and microbiological parameters of household grey water, including pH, conductivity, turbidity, and the presence of elements such as calcium, magnesium, and potassium, as well as contaminants like nitrates and sulfates. The treatment system employed consisted of multiple filtration stages using sand, coconut husk, pebbles, activated charcoal, limestone, and gravel, complemented by reverse osmosis. Results indicated significant improvements post-treatment: normalization of pH, reduced conductivity, elimination of color, and substantial reductions in major contaminants. Notably, the system achieved 100% removal of E. coli, total coliforms, and fecal coliforms. The findings underscore the effectiveness of greywater treatment in reducing water toxicity and enhancing its suitability for various applications, thereby contributing to pollution reduction and resource conservation. Such recycling initiatives can significantly address water scarcity issues and encourage sustainable water resource management.

Characterization of Wastewater and Evaluation of Recycling Technologies Using Analytical Hierarchical Process for a University Community

Characterization and treatment of greywater are major environmental issues in most nations of the world. The research aims to characterize and evaluate recycling technologies using an analytical hierarchical process for Afe Babalola University Ado-Ekiti (ABUAD) community. A survey was conducted around ABUAD to determine the number of functioning boreholes and active water systems in the area, the total population of students was derived from the total head count of each room and student in each hostel, and a population projection for the next 3 years was conducted to determine the rate at which the student body will grow in terms of future water demands, and daily water volume and questionnaires were used to collect data. Before developing the small-scale model of the greywater filter system (consisting of activated carbon, shaft sand, pebbles, cotton fiber, and gravel), water grey samples were gathered from several ABUAD locations to evaluate the pollution level of each greywater source. A total of 88 students (43 males and 45 females) replied to the survey, revealing their high need for clean water and their dissatisfaction with the water supply in their respective hostels. The water quality tests conducted in the various locations of ABUAD reveal high levels of total dissolved solids (TDS) and turbidity, particularly in the girl’s hostels, and the water was discovered to be predominantly alkaline. After passing a sample of greywater through the small-scale greywater filtering device, it was determined to be effective, since it produced clear, reusable water and a greywater filtration system in ABUAD will yield favorable outcomes.

A review of untreated household greywater quality to inform the water saving–risk trade-off in South Africa

Interest in greywater reuse is increasing in South Africa, because of the potential to supplement scarce freshwater resources in the face of increasing demand and aridity. This paper aims to inform the water saving–risk trade-off associated with residential untreated greywater use, through a statistical analysis of greywater quality results as sourced from prior South African studies. Greywater sources included in this review were the bathroom, kitchen, laundry, mixed and general residential sources. Variability in terms of each of the reported physical, chemical and microbiological constituents by source and between result sets was noted. Statistically significant differences were evident between the pH, conductivity and phosphorus values of certain sources. A risk assessment undertaken for each of the constituents revealed further variability. The constituent with the highest number of high-risk samples was total dissolved solids. The relatively high risk and negative consequences in greywater practices in terms of public health, the environment, and infrastructure, given this variability, provide insight into the trade-off with potential water savings. It is recommended that a more nuanced view of the potential potable savings associated with greywater reuse and also improved risk management is required by the user.

Photocatalytic Degradation of Recalcitrant Pollutants of Greywater

These days, many countries have a water shortage and have limited access to clean water. To overcome this, a new treatment is emerging, namely, the photocatalytic processing of greywater. Photocatalytic processes to remove the organic matter from different greywater sources are critically reviewed. Their efficiency in degrading the organic matter in greywater is scrutinized along with factors that can affect the activity of photocatalysts. Modified TiO2, ZnO and TiO2 catalysts show great potential in degrading organic materials that are present in greywater. There are several methods that can be used to modify TiO2 by using sol-gel, microwave and ultrasonication. Overall, the photocatalytic approach alone is not efficient in mineralizing the organic compounds, but it works well when the photocatalysis is combined with oxidants and Fe3+. However, factors such as pH, concentration and catalyst-loading of organic compounds can significantly affect photocatalytic efficiency.

Recycling of the Greywater from Mosques in Oman

Oman is located within Arid and Semi-Arid regions, where water resources are very scarce. The national average rainfall is just 80-100 mm per year. With high temperatures (30 ºC to above 40 ºC) the evaporation is also high. Therefore, it is absolutely necessary to conserve and recycle water in Oman. The study aims to identify ablution water (the ritual washing of the exposed parts of the body, the face, hands and feet before each prayer called ablution) and to prove that it as one of the least polluted sources of greywater, by examining the properties of greywater and comparing its results with the results of other greywater, taking into account the criteria for reusing treated water, as well as developing appropriate treatment techniques. The study dealt with the use of solar energy to operate the treatment unit, and developed an appropriate design for the treatment unit. The study recommends using the total volume of greywater generated for non-potable purposes including rinsing, car washing, gardening and irrigation purposes. In this way, the greywater from mosques is recycled in the most beneficial way and at a lower cost in order to provide fresh water for future generations.

Quantity and quality characteristics of greywater from an Indian household.

A year-long study was conducted to assess the quantity and quality characteristics of greywater generated from different sources of an Indian household. The effect of source separation on greywater quantity and pollutant load contribution was also assessed. Composite samples were collected separately over a period of 24h from each of the greywater source, namely hand basin, bathroom, kitchen, and laundry, and were analysed for different physico-chemical and microbiological parameters. The mean greywater generation averaged 62 L per person per day. Quantitatively, kitchen and bathroom greywater contributed 37 and 31% of the total greywater volume, respectively, while hand basin and laundry greywater accounted for 11 and 21% of the total greywater generation. Kitchen greywater contributed about 60% of the organic load in terms of biochemical oxygen demand (BOD) and chemical oxygen demand (COD), while laundry greywater was the major contributor of heavy metals and PO4-P loads. Hand basin and bathroom greywaters were the major sources of total coliforms. The analysis shows that separation of kitchen and laundry greywater is beneficial as it reduces pollutant load considerably.

Greywater Sources, Characteristics, Utilization and Management Guidelines: a review

Greywater is defined as a domestic wastewater that is uncontaminated by direct contact with human excreta. Sources of grey water include kitchen sinks, showers, baths, washing machines and dishwashers. Most greywater streams produce effluents high in dissolved contaminants and low in turbidity and suspended solids. As global water resource supplies are worsening and water shortages will affect 2.7 billion people by 2025, resulting in poverty and famine. Reusing greywater is a good way to solve this water shortage problem. As greywater contains fewer pathogens than domestic wastewater (black water), it is safer to handle, easier to treat and reuse onsite for toilet flushing and landscape or for crop irrigation and other non-potable uses. Greywater use in gardens or toilet systems helps to achieve some of the goals of ecologically sustainable development including: (a) reduced freshwater extraction from rivers and aquifers, (b) less impact from septic tank and treatment plant infrastructure, (c) reduced energy use and chemical pollution from treatment plants, (d) groundwater recharge and (e) reclamation of nutrients. However, the biological oxygen demand (BOD), surfactants, oil and grease, detergent residues (nitrogen, phosphorous, sulfate, ammonium, sodium, and chloride) must be considered when handling greywater streams. Several countries have developed guidelines for the reuse of treated greywater to flush toilets and irrigation systems for ornamental garden and lawn watering, depending on the type of grey water and treatment level. Many developed and developing countries have established regulations and guidelines for greywater treatment and reuse. However, some countries have strict rules compared to others. Egypt appears to be a world leader in the treatment and reuse of wastewater and has several laws in place for treatment options and selection of crops to be irrigated with treated wastewater. Given the water shortage in Egypt and the growing population, the government of Egypt imparked on several mega projects of 4-level wastewater treatment throughout the country for use in agricultural production.

AN INVESTIGATION OF GREYWATER ONSITE REUSE POTENTIAL IN AN ARID ENVIRONMENT

Wastewater originating from bathtubs, showers, hand basins, kitchen sinks, dishwashers and laundry machines is usually not as heavily polluted as toilet water and is thus given the name greywater. Greywater separation for onsite reuse has often been voiced as a viable option, particularly for areas suffering from water scarcity. Such areas include remote arid areas, such as desert cities and arid coastal zones. However, issues related to consistency in the quality and quantity of generated greywater were listed as challenges hindering the adoption of greywater reuse. Thus, the objective of this study was to characterize the different greywater sources for variations in the quality and quantity of greywater in households in the city of Al Ain, UAE over a period of 3 months. Samples were collected from 10 Households and tested for the typical water quality parameters (pH, turbidity, COD, and TDS). In addition, a questionnaire was designed to get an estimate of the greywater flow in the different households. Results indicate that the average daily greywater production was around 88 L per person per day. Even though the results of the water quality analysis for light greywater sources (laundry, showers, and hand basins) exhibited high variability, it was still suitable for direct irrigation. The quantification of greywater flow and potential water savings indicated that greywater could be sufficient for onsite reuse in non-crop irrigation in some of the households.

A contact angle study of different greywater sources with hydrophobic membranes

Abstract The wetting phenomenon is a major problem in the membrane distillation (MD) process, and it is the main reason that limits MD being used in wastewater reclamation. Active surfactant in the detergents reduces the contact angle between the liquid and the hydrophobic membrane surface, which could result in wetting. Extensive laboratory research was conducted using commercial hydrophobic flat-sheet membranes to identify the impact of anionic surfactants and surface tension forces on these membranes. The aim of this paper is to find a suitable membrane for pure water production from greywater using MD, as well as to provide a relationship between surfactant concentration and the contact angle for different types of membrane. The absorbance of each sample was measured by a spectrophotometer prior to the contact angle test on four different types of hydrophobic membranes. It was concluded that the polypropylene membrane would be unsuitable for the treatment of greywater directly due to the loss of surface tension forces upon the addition of an anionic surfactant. However, the polytetrafluoroethylene membrane could be effective in this process while the concentration of surfactant in the feed source is kept constant. The results from the experimental tests proposed a relationship between the contact angle of a water droplet on the surface of a flat-sheet membrane and the concentration of surfactant in the solution.

Characterization of segregated greywater from Indian households-part B: emerging contaminants.

Emerging contaminants (ECs) have become an increasing area of concern due to the likely impacts of these compounds on human health and the environment. Generally, products which are used for households and personal care activities contribute to major percentage of ECs in household greywater. Not much information on the presence of xenobiotic organic compounds in greywater is currently available. Therefore, the present study focused on the qualitative and quantitative analyses of emerging contaminants from different classifications of Indian households. The qualitative screening of emerging pollutants by solid-phase extraction-gas chromatography and mass spectroscopy (SPE-GC-MS) showed the presence of 78 different emerging contaminants from three different sources, which are categorized into ten different groups based on their chemical properties. The quantitative analysis of few selected target pollutants such as phthalic esters, namely diethyl hexyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, triclosan, bisphenol A, caffeine, acetaminophen, 3-methyl salicylic acid, 4-octylphenol, and 4-nonylphenol were found to be 0.38 ± 0.39 μg/L, 1.57 ± 1.54 μg/L, 4.77 ± 2.57 μg/L, 0.712 ± 0.17 μg/L, 5.82 ± 1.85 μg/L, 11.08 ± 2.64 μg/L, 2.30 ± 1.19 μg/L 13.18 ± 4.48 μg/L, 3.75 ± 1.90 μg/L, 4.95 ± 2.21 μg/L, and 5.96 μg/L, respectively. Risk assessment indicated that 63 compounds identified in the greywater can be considered priority pollutants. Based on the results obtained in the present study, effective zero-discharge liquid system can be designed for different sources of greywater and it can be recycled and reused without much risk. Graphical abstract .

Effects of direct discharge of domestic greywater to nearby water body

Domestic greywater is being directly discharged to the ditches without any treatment which affect the environment. Therefore, the investigation was conducted to assess the effects of different sources of greywater to drainage using loading rates while calculate Dissolved Oxygen (DO) level by Streeter-Phelps equation. The contribution of bathroom source from House A was higher with the average of 263.5 L/day followed by kitchen and laundry with the average of 133.04 L/day and 52.14 L/day respectively. Total pollutant produced of greywater from kitchen according to Biochemical Oxygen Demand (BOD) loading rate was high for House A, B and C with the BOD loading rates of 302.1, 194.9 and 274.2 kg/day respectively. Meanwhile, the values of Chemical Oxygen Demand (COD) were the highest by 2019 mg/L from kitchen source of House A and 1962 mg/L from laundry activity of House B. However, the highest value of Total Suspended Solid (TSS) and Turbidity were from kitchen source within 733 mg/L and 104.3 NTU respectively and the highest value of pH was from laundry source within 9.56. From Streeter-Phelps modelling, the value of measured DO at point source has low level of oxygen which was 3.29 mg/L. Therefore, this study was expected to give benefits to local authority as their references or guidelines in greywater planning system.

Investigation into untreated greywater reuse practices by suburban households under the threat of intermittent water supply

Abstract Untreated greywater reuse at the household level is an accessible water source to supplement non-potable water requirements in times of emergency water curtailments but poses various risks to the consumer, the wider community, infrastructure and the environment. Little information is known about unregulated, untreated greywater reuse practices under emergency conditions in suburban communities where consumers have become accustomed to reliable potable water supplied via a pressurised, piped distribution system. There is a lack of knowledge regarding the sources of greywater used, collection methods, storage and distribution of greywater, the application points, the level of treatment (if any) and the perceived risks associated with the greywater reuse. The City of Cape Town was selected as a case study site for research into greywater reuse under the threat of ‘Day Zero’ and stringent water restrictions, implemented during the 2017/2018 summer season. A consumer survey and analysis of relevant online forums was conducted in order to obtain the necessary information. Greywater reuse practices from a sample group of 351 consumers were identified and classified. Untreated greywater reuse was found to be common, mainly for garden irrigation and toilet flushing. The results point to high-risk activities in the study group.

Effects of Impure Water Sources on the Early-Age Properties of Calcium Sulfoaluminate (CSA) Cement

Abstract One of the benefits of calcium sulfoaluminate (CSA) cements is that these materials gain strength rapidly, and strength development is often measured in hours instead of days. This property makes these materials desirable for use in temporary, nonreinforced repairs of roadways, airfields, and navigable locks. The rapid repair of these infrastructure elements is critical to transporting supplies into regions devastated by disaster. In these austere environments, potable water may not be available in sufficient quantities to make vital repairs, and the use of impure water in the production of CSA cement–based concrete would be advantageous. However, the hydration products formed by CSA cement are significantly different from those formed by portland cement and may react differently to alkalis, chlorides, sulfates, and other contaminates that these impure water sources may contain. This article investigates the impact of calcium, sodium, potassium, and magnesium chloride and calcium, sodium, and magnesium sulfate on the early-age unconfined compressive strength development of commercially available CSA cement–based concrete. Of these salts, calcium chloride had the greatest effect on early-age concrete properties, retarding unconfined compressive strength development. The strength results obtained from CSA cement–based concrete mixed with these saline solutions are compared with those obtained from potential real-world sources of mixing water, including seawater and greywater.

Greywater in the drains of a sewered community in Ghana

Abstract With less than 5% sewerage coverage and abysmal greywater management, Ghana's environment could be highly polluted, especially water resources. The few sewered communities may be guilty of pollution from greywater discharge into stormwater drains. In this study, Asafo, Ghana, was used as a case study to assess greywater characteristics in the major drains in a sewered community. The approach involved desk study reviews and laboratory analysis of greywater samples. The findings showed some inhabitants discharge greywater into neighbourhood drains instead of sewers. Most greywater sources from reviews and sampled drains failed the discharge limits for major contaminants including turbidity (39.4–2,880 NTU), BOD5 (64–700 mg/L), COD (207–2,308 mg/L), TSS (70–4,720 mg/L), TDS (420–2,860 mg/L), nutrients – TKN, NH3-N, NO3−-N, NO2−-N (0–218.5 mg/L), total P and PO43−(1.24–26.18 mg/L), elemental species – Na, K, Mg, etc (0–1.6 mg/L), and microbiological – total and faecal coliforms, and E. coli (2.95–10.4 log CFU/100 ml). High strength greywater accounted for odour emissions where flows stagnated. Greywater characteristics are highly variable but have potential for biological treatment as the BOD5:COD ratios ≥0.5. Ghanaian greywater, including flows from a sewered community, is untreated and polluted, and our environment is unsafe.

Greywater characterization and loadings – Physicochemical treatment to promote onsite reuse

Greywater is the wastewater produced in bathtubs, showers, hand basins, kitchen sinks, dishwashers and laundry machines. Segregation of greywater and blackwater and on site greywater treatment in order to promote its reuse for toilet flushing and/or garden irrigation is an interesting option especially in water deficient areas. The objective of this study was to characterize the different greywater sources in Greek households and to evaluate the performance of alternative physicochemical treatment systems to treat several types of greywater. Based on the results average daily greywater production was equal to 98 L per person per day and accounts for approximately 70–75% of the total household wastewater production (135 L per person per day). Among the different sources, laundry and kitchen sink are the main contributors to the total greywater load of organic carbon, suspended solids and surfactants, whereas dishwasher and bathroom greywater are the main sources of phosphorus and endocrine disrupting chemicals respectively. Depending on sources, greywater accounts for as low as 15% of the total wastewater load of organic carbon (in the case of light greywater sources), to as high as 74% of the total load organic load (in the case of the heavy greywater sources). On the other hand, the nutrients load of greywater is limited. The application of a physical treatment system consisting of coagulation, sedimentation, sand filtration, granular activated carbon filtration and disinfection can provide for a final effluent with high quality characteristics for onsite reuse, especially when treating light greywater.

Alkylphenol and phthalate contamination of all sources of greywater from French households

Despite the importance of domestic wastewater, the contribution of greywater to both alkylphenol and phthalate pollution is not yet well documented. Likewise, the detailed emissions of phthalates and alkylphenols by greywater have been insufficiently studied, this work aims to fill this gap. The levels of four phthalates (DEP, DnBP, BBP and DEHP) and two alkylphenols (nonylphenol isomers and octylphenol) were quantified in six different types of greywater, namely that from washing machines, manual dishwashing, dishwashers, bathroom water (from showers and sinks) and floor cleaning. This paper presents the methodology used to characterize all sources of greywater and provides their levels of contamination. The highest concentrations were found in greywater produced by the washing machine and floor cleaning, while washing machine and shower greywater have the highest phthalate and alkylphenol loads because of the volume associated with these two sources of greywater.

Greywater characterization and handling practices among urban households in Ghana: the case of three communities in Kumasi Metropolis.

Greywater management in Ghana receives little or no attention although untreated greywater is associated with environmental and public health risks. This paper assesses greywater characteristics and handling practices among urban households in three selected communities in Kumasi, the second largest city of Ghana. The study involved in-depth surveys (interviews and observations) with 90 households, and collection of 18 greywater samples from nine greywater sources for laboratory analysis. Average greywater generation is 43.36 ± 17 litres per capita per day, equivalent to 36% of average water consumption. Greywater is untreated before disposal (≈99%), and disposal is mainly (89%) into drains and onto streets. Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) levels are high but give very low BOD/COD ratios (0.20 ± 0.07) indicating a very low biodegradability potential. Nutrient levels are high: 12 times (P) and 30 times (N) in excess of standard discharge limits. Other contaminants detected are heavy metals (Fe, Pb, Zn and Cd), microbes (total coliforms, Escherichia coli and Salmonella spp.), and organic micropollutants - benzalkonium chloride, parabens (methyl and propyl), sodium benzoate and hypochlorite - and details of the levels are discussed in the paper. Greywater reuse could be useful for biomass production, but it also presents a challenge and threat to natural biological processes and water sources.

Treatment and potential reuse of greywater from schools: a pilot study.

This study presented performance data on a low cost and easy maintenance pilot system for on-site treatment and reuse of water collected from wash sinks and fountains, as major sources of greywater (GW) at schools. Various treatment options were studied including screening, sand filtration, chlorination, and UV disinfection operated at different flow rates. Results showed that filtration operated at low rates is very effective in total suspended solids (TSS) removal, while UV proved to be more effective than chlorination for reduction of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total coliforms. Removal efficiencies up to 63%, 30% and 20% were obtained for TSS, COD and BOD, respectively and reductions of log TC (CFU/100 ml) from 6.5 to 2 were obtained at a filtration rate of 14 m3/d·m2. Treated effluent satisfied WHO standards for reclaimed water reuse in landscape irrigation and toilet flushing. The filtration-UV system is robust, showing the best and most reliable performance for low and high strength GW treatment even under a 10-fold increase in flow rate. A 5 m3/d pilot plant was developed for schools having 500 students and detailed cost-benefit analysis indicated a net saving value, a surplus of $1,600 per year, and pay back after 6 years and 11 months.

Reducing the burden of rural water supply through greywater reuse: a case study from northern Malawi

Greywater reuse has potential for non-potable applications that conserve freshwater resources in water-stressed areas especially in sub-Saharan Africa. The feasibility of reusing greywater for domestic activities in a rural area of Malawi, Africa, was evaluated from microbiological and public acceptance perspectives. Median Escherichia coli concentrations for eight domestic greywater sources (handwashing, laundry, runoff from a tap apron, bathing, cleaning a home/kitchen, cleaning a water collection container, washing plates and soaking vegetables) ranged from 100 to >20,000 colony forming units (cfu)/100 ml. Twenty-four of 47 greywater samples tested (51%) met the World Health Organization guideline for unrestricted use of greywater for irrigation. Pertinently, 80% (4/5) and 60% (3/5) of greywater samples from handwashing stations and bathing had E. coli less than the WHO guideline. Users reported greatest acceptance of reusing greywater for growing food and washing clothes, especially when the greywater source was bathing. Acceptance was closely tied to a household's economic standing, geographic location, and first-hand knowledge of reusing greywater. Greywater reuse practices in rural areas, especially targeting bathing water as suitable from bacteriological and user perception criteria, can help mitigate the impacts of water stress in sub-Saharan Africa.