Greywater characterization and generation rates in a peri urban municipality of a developing country

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.

Household water use and greywater management in Khulna city, Bangladesh

While substantial progress has been made in improving water and sanitation services in low- and middle-income countries, aligned basic services such as greywater, stormwater, and solid waste management have progressed little in recent decades. Data was collected in Khulna city, Bangladesh via a household survey (n = 192) of low-income areas exploring domestic water use and greywater volumes, characteristics, and disposal practices. Most households (71%) use a piped water supply for domestic purposes, supplemented by seasonal rainwater harvesting (26%) and greywater use (13%). Of the total water used by households (mean: 594 L/household/day and equivalent to 116 L/person/day), approximately 58% becomes greywater through bathing, dishwashing, religious practices, handwashing, laundry, and mopping. Greywater produced ranges from 61-1274 L/household/day, with a mean of 345 L/household/day and equivalent to 78.4 L/person/day. Greywater characteristics vary depending on the activity, individual behaviours and any products used during cooking, bathing, or cleaning. After generation, households dispose greywater to open drains (67%), nearby waterbodies (17%) directly to the ground (9%), or decentralised wastewater treatment system (7%). Without services for greywater management, greywater disposal may have considerable public and environmental health implications, necessitating careful attention and oversight from service-providers and stakeholders beyond the household-level.

Nutrient treatment of greywater in green wall systems: A critical review of removal mechanisms, performance efficiencies and system design parameters

Greywater has lower pathogen and nutrient levels than other mixed wastewaters, making it easier to treat and to reuse in nature-based wastewater treatment systems. Green walls (GWs) are one type of nature-based solutions (NBS) that are evolving in design to support on-site and low-cost greywater treatment. Greywater treatment in GWs involves interacting and complex physical, chemical, and biological processes. Design and operational considerations of such green technologies must facilitate these pivotal processes to achieve effective greywater treatment. This critical review comprehensively analyses the scientific literature on nutrient removal from greywater in GWs. It discusses nutrient removal efficiency in different GW types. Total nitrogen removal ranges from 7 to 91% in indirect green facades (IGF), 48-93% for modular living walls (MLW), and 8-26% for continuous living walls (CLW). Total phosphorus removal ranges from 7 to 67% for IGF and 2-53% for MLW. The review also discusses the specific nutrient removal mechanisms orchestrated by vegetation, substrates, and biofilms to understand their role in nitrogen and phosphorus removal within GWs. The effects of key GW design parameters on nutrient removal, including substrate characteristics, vegetation species, biodegradation, temperature, and operating parameters such as irrigation cycle and hydraulic loading rate, are assessed. Results show that greater substrate depth enhances nutrient removal efficiency in GWs by facilitating efficient filtration, straining, adsorption, and various biological processes at varying depths. Particle size and pore size are critical substrate characteristics in GWs. They can significantly impact the effectiveness of physicochemical and biological removal processes by providing sufficient pollutant contact time, active surface area, and by influencing saturation and redox conditions. Hydraulic loading rate (HLR) also impacts the contact time and redox conditions. An HLR between 50 and 60 mm/d during the vegetation growing season provides optimal nutrient removal. Furthermore, nutrient removal was higher when watering cycles were customized to specific vegetation types and their drought tolerances.

Greywater treatment in a green wall using different filter materials and hydraulic loading rates

Green walls in urban environments can be both an aesthetic feature and be of practical use in greywater treatment. This study evaluates the effect of different loading rates (4.5 l/d, 9 l/d, and 18 l/d) on the efficiency of treating actual greywater from a city district in a pilot-scale green wall with five different filter materials as substrates (biochar, pumice, hemp fiber, spent coffee grounds (SCG), and composted fiber soil (CFS)). Three cool climate plant species, Carex nigra, Juncus compressus, and Myosotis scorpioides, were chosen for the green wall. The following parameters were evaluated: biological oxygen demand (BOD), fractions of organic carbon, nutrients, indicator bacteria, surfactants, and salt. Three of the five materials investigated - biochar, pumice, and CFS - showed promising treatment efficiencies. The respective overall reduction efficiencies of BOD, total nitrogen (TN) and total phosphorus (TP) were 99%, 75%, and 57% for biochar; 96%, 58%, and 61% for pumice; and 99%, 82% and 85% for CFS. BOD was stable in the biochar filter material with effluent concentrations of 2 mg/l across all investigated loading rates. However, higher loading rates had a significantly negative effect on hemp and pumice for BOD. Interestingly, the highest loading rate (18 l/d) flowing over pumice removed the highest levels of TN (80%) and TP (86%). Biochar was the most effective material in removing indicator bacteria, with a 2.2-4.0 Log₁₀ reduction for E. coli and enterococci. SCG was the least efficient material, giving a higher BOD in the effluent than in the influent. Therefore, this study presents the potential of natural and waste-derived filter materials to treat greywater effectively and the results can contribute to the future development of nature-based greywater treatment and management practices in urban areas.

Granular media filtration for on-site treatment of greywater: A review

Rapid urbanization and industrialization have put pressure on water resources and centralized wastewater treatment facilities and the need for greywater treatment at decentralized levels is increasing. This paper reviews the studies that used granular filtration for the treatment of greywater. Filter media characteristics that helps in the selection of suitable sustainable and environmental friendly materials without compromising the quality of treated greywater is first reported. The effect of type of filter media, media size and media depth along with the effect of operating conditions are discussed in detail. The choice, role and effect of different pre-treatment alternatives to granular media filtration are also presented. The efficiency of the filters to remove different physicochemical and microbial parameters was compared with different reuse guidelines and standards. Reported studies indicate that not only filter media characteristics and operating conditions but also the quality of raw greywater significantly influence the filter performance. Based on the source of greywater and desired reuse option, different granular media filtration alternatives are suggested. Operation of filters with properly selected media at optimum conditions based on the source of greywater helps filter in achieve the different reuse standards.

Recent insights into greywater treatment: a comprehensive review on characteristics, treatment technologies, and pollutant removal mechanisms

With the rapid socio-economic and industrial development, the problem of water shortage is becoming increasingly serious. Seeking alternative water sources to reduce the need for freshwater resources is an increasing concern. Household greywater production is high and accounts for about 50-80% of domestic wastewater. In recent years, the in situ treatment and reuse of greywater have received widespread attention. Treated greywater can be used for non-potable purposes such as toilet flushing and irrigation, which can greatly reduce the pressure of freshwater resource shortage. This paper reviews the sources and characteristics of greywater and analyzes its quantity and quality. In addition, this paper outlines and summarizes various greywater treatment technologies commonly used, including physical, biological, and chemical treatment technologies, as well as combination technologies. Understanding the mechanisms of contaminant removal is essential for effective greywater treatment. While discussing different treatment technologies, we focus on the removal mechanisms of pollutants from greywater, including organics, nutrients, surfactants, and emerging contaminants. Finally, future perspectives on greywater management and reuse are presented. Through a comprehensive review, we expect that this review will help the reader to better understand the characteristics of greywater and to more rationally select the appropriate treatment technology based on the removal mechanism of pollutants.

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 24 h 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.

A state-of-the-art-review on grey water management: a survey from 2000 to 2020s

Water reuse can contribute to reducing pressures on water resources, as an important approach and practice, reducing the demand for potable water for purposes not requiring high quality water. With water resources being depleted and the demand for water increased, grey water reuse becomes more popular in order to preserve water worldwide. This paper presents a comprehensive review of all significant research and reviews existing case studies to review the present knowledge with respect to the characteristics of grey water. The main summary table covers 63 works that focus on the application of these methods to different fields of sustainable building design. Key fields are reviewed in detail: grey water, including water reuse; grey water recycling; water sustainability; building design optimization; and wastewater of several areas simultaneously, with particular focus on buildings. This research aims to introduce the review of the research that covered the grey water management. Various engineering databases, international journals, and conference proceedings were searched. International journals were searched for relevant research papers. This paper provides perspectives on grey water context in order to frame the breadth and multiple dimensions it encompasses, to summarize recent activities on selected relevant topics, and to highlight possible future directions in research and implementations.

Sustainable Use of Wastewater in Agriculture: A Bibliometric Analysis of Worldwide Research

It is estimated that at least one quarter of the world’s population will be affected by water shortages in the coming years and by 2030 there will be a global water deficit of 40% if urgent action is not taken. Currently, the main consumer of water globally is agriculture. In addition, it has been estimated that to meet the demand for food by 2050, the water available for agricultural irrigation would have to increase by 70%. In this context, wastewater could become a relevant water resource to meet this growing demand. This article aims to show the state of the global research on sustainable use of wastewater in agriculture. To this end, a systematic qualitative analysis and a quantitative bibliometric analysis were conducted. The search was carried out for the period 2000–2019, and the analyzed sample comprised 1986 articles. The results show that this line of research is one of the most outstanding within agriculture and has gained special relevance during the last five years. Research has improved significantly at a technical level, but problems such as energy consumption, and the elimination of heavy metals and elements of chemical and pharmacological products, still need to be refined. There is a particular lack of contributions covering social aspects. This article can serve as a reference for both researchers and stakeholders interested in this topic.

Resolving the relative contributions of cistern and pour flushing to toilet water usage: Measurements from urban test sites in India

A challenge in water reuse for toilet flushing in India and other Asian countries derives from pour flushing practices. It is a common assumption that the amount of pour flushed water used for personal cleansing is small in comparison to the cistern flush volume, however there is a knowledge gap regarding the actual contribution of each water source to the blackwater amount. In this study, digital water meters were used to measure the fraction of water from personal wash tap relative to cistern water that is used for toilet flushing. High temporal resolution measurements were carried in three different urban sites in the city of Coimbatore in the southern Indian state of Tamil Nadu where onsite sanitation treatment prototypes that may provide reclaimed water for cistern flushing are being tested. Data collected over periods of up to 2 months show that the contribution of the cistern flush to the total blackwater volume is low (14-40%). These data highlight an important factor to inform interventions designed around water reuse for flushing in world geographies where personal toilet cleansing by water is the common practice.

Quantity and quality characteristics of greywater: A review

Due to depletion of water resources and increased water demand, greywater reuse is gaining popularity as a means of water conservation all over the world. Availability of reliable data on greywater generation and quality characteristics is important in deciding the treatment system and the reuse option. This paper summarises quantity and quality characteristics of greywater reported from different parts of the world. Greywater generation from different countries is compared and its variability is discussed. Important pollutants of concern in greywater such as organic content, nutrients, microorganisms, metals and organic micropollutants from different greywater sources such as bathrooms, hand basins, kitchen and laundry are described. The review shows large variations in greywater quality and quantity with respect to time and source, and the selection of a treatment system would largely depend on this variability. The review also shows that at the levels found in greywater, heavy metals and organic micropollutants in recycled greywater generally do not pose a threat to human health if treated properly.

A review of nature-based solutions for greywater treatment: Applications, hydraulic design, and environmental benefits

Recognizing greywater as a relevant secondary source of water and nutrients represents an important chance for the sustainable management of water resource. In the last two decades, many studies analysed the environmental, economic, and energetic benefits of the reuse of greywater treated by nature-based solutions (NBS). This work reviews existing case studies of traditional constructed wetlands and new integrated technologies (e.g., green roofs and green walls) for greywater treatment and reuse, with a specific focus on their treatment performance as a function of hydraulic operating parameters. The aim of this work is to understand if the application of NBS can represent a valid alternative to conventional treatment technologies, providing quantitative indications for their design. Specifically, indications concerning threshold values of hydraulic design parameters to guarantee high removal performance are suggested. Finally, the existing literature on life cycle analysis of NBS for greywater treatment has been examined, confirming the provided environmental benefits.

Households' willingness to adopt greywater treatment technologies in a developing country - Exploring a modified theory of planned behaviour (TPB) model including personal norm

This study explored willingness of households to adopt a greywater treatment and reuse system using the theory of planned behaviour in its original form and an extended model including personal norms. The study was conducted among 478 household heads in the central region of Ghana. The results indicate the original theory of planned behaviour (TPB) model explained about 54% of the variance in respondents' intentions to adopt this system and the extended model which includes personal norms explained 59% of the intentions. The extended model turned out to be the better model to predict willingness to adopt this household greywater and treatment system. The findings of this study shed more light on the role of personal norms in households' willingness to adopt a greywater treatment and reuse system and may inform interventions aimed at promoting such systems.

What are the main factors influencing the presence of faecal bacteria pollution in groundwater systems in developing countries?

Groundwater is the major source of drinking water in most rural areas in developing countries. This resource is threatened by the potential presence of faecal bacteria coming from a variety of sources and pollution paths, the former including septic tanks, landfills, and crop irrigation with untreated, or insufficiently treated, sewage effluent. Accurately assessing the microbiological safety of water resources is essential to reduce diseases caused by waterborne faecal exposure. The objective of this study is to discern which are the most significant sanitary, hydrogeological, geochemical, and physical variables influencing the presence of faecal bacterial pollution in groundwater by means of statistical multivariate analyses. The concentration of Escherichia coli was measured in a number of waterpoints of different types in a rural area located in the coast of Kenya, assessing both a dry and a wet season. The results from the analyses reaffirm that the design of the well and their maintenance, the distance to latrines, and the geological structure of the waterpoints are the most significant variables affecting the presence of E. coli. Most notably, the presence of faecal bacteria in the study area correlates negatively with the concentration of ion Na⁺ (being an indirect indicator of fast recharge in the study site), and also negatively with the length of the water column inside the well.

Characteristics of rural agritainment sewage in Sichuan, China

As a new form of rural tourism, agritainment originating from Sichuan food and recreation establishments is now popular all over China. The physico-chemical characteristics of agritainment sewage in Sichuan were surveyed through questionnaires and sample analysis. It was found that 5.3% of agritainment sites discharged black water directly while 25.3% of sites discharged grey water directly in the environment. The annual average ratio of sewage discharge volume to agritainment operating income is 9.24 L/yuan and could be used to predict discharge volume. The annual discharge volume from agritainment in Sichuan was 124 billion litres in 2017 and was 55% higher than that of 2016. The annual sewage discharge volume from agritainment sites in Sichuan ranged from 12 thousand to 38 million litres and the total sewage discharge volume from 24% of agritainment sites represented 77% of the total annual discharge volume. The main pollutants in Sichuan agritainment sewage were total suspended solids (10-2,470 mg/L), total phosphorus (0.07-17.1 mg/L), chemical oxygen demand (144-2,580 mg/L) and anionic surfactant (3.5-411 mg/L) and the percentage of sewage exceeding the standard (Chinese standards GB8918-1996 Class II) of these environmental indicators was up to 45%, 75%, 95% and 80%, respectively. Considering the increasing volume and concentration of agritainment sewage, we urge the public and government to be aware of related water pollution issues. Based on this study, additional surveys of characteristics of agritainment sewage are suggested to be included in the third national pollution source survey in China (2027).

Greywater Characteristics, Treatment Systems, Reuse Strategies and User Perception-a Review

This paper presents a literature review of the quality of greywater generated in different, especially developing, countries, constituents found in greywater, some treatment systems, natural materials for treatment, some reuse strategies and public perception regarding greywater reuse. The review shows that generation rates are mostly influenced by lifestyle, types of fixtures used and climatic conditions. Contaminants found in greywater are largely associated with the type of detergent used and influenced by other household practices. Many of the treatment systems reviewed were unable to provide total treatment as each system has its unique strength in removing a group of targeted pollutants. The review revealed that some naturally occurring materials such as Moringa oleifera, sawdust, can be used to remove targeted pollutants in greywater. The study further showed that user perceptions towards greywater treatment and reuse were only favourable towards non-potable purposes, mostly due to perceived contamination or lack of trust in the level of treatment offered by the treatment system.