Greywater Treatment by High Rate Algal Pond under Sahelian Conditions for Reuse in Irrigation

High Rate Algal Pond (HRAP) was constructed and operated using a mixer device to investigate its capability in treating greywater for reuse in gardening. Physico-chemical and microbiological parameters were monitored. With a hydraulic retention time of 7.5 days and a solid retention time of 20 days, the average removal efficiencies (ARE) were 69% and 62% for BOD5 and COD respectively. The ARE for , and were 23%, 52% and 43% respectively. The removal of suspended solids (SS) was unsatisfactory, which could be attributed to the low average algal settling efficiencies of 9.3% and 16.0% achieved after 30 and 60 minutes respectively. The ARE of fecal coliforms, Escherichia coli and enterococci were 2.65, 3.14 and 3.17 log units respectively. In view of the results, the HRAP technology could be adapted for greywater treatment in sahelian regions. However, further studies on the diversity of the algal species growing in the HRAP unit are necessary in order to increase the removal of SS. Hazards of a reuse of the effluents are discussed on the basis of the various qualitative parameters. The residual content of E. coli was varying from 4 CFU per 100 mL. Based on WHO guidelines for greywater reuse in irrigation, the effluents could be used for restricted irrigation (E. coli < 105 CFU per 100 mL). Furthermore, the reuse potential is discussed on the basis of FAO guidelines using SAR (3.03 to 4.11), electrical conductivity (482 to 4500 μS/cm) and pH values (6.45 to 8.6).

Reclaiming Biologically Pretreated Greywater for Reuse by Photocatalytic Oxidation: Qualitative Study on the Removal of Trace Organics

This study was carried out for gathering qualitative information about the potential of photocatalytic oxidation for the removal of trace organics (analysed by gas chromatography coupled to mass spectrometry, GC/MS) from biologically pretreated greywater to make it suitable for high quality reuse applications like groundwater recharge. Additionally, fractions of bulk organics (humic substances, building blocks, and low molecular weight organic acids) were quantified by liquid chromatography with organic carbon detection. Biologically pretreated greywater was subjected to photocatalytic oxidation in open stirred vessel reactors with UV lamps positioned over the reactors. UV doses of 0, 5, and 15 Wh·L-1 and TiO2 P25 photocatalyst concentrations of 1, 5, 10, and 20 g·L-1 were investigated. Photocatalysis experiments with a 15 Wh·L-1 UV dose were also conducted in the presence of 1 g·L-1 powdered activated carbon. Subsequent to mere contact of the photocatalyst to biologically pretreated greywater without UV, GC/MS did not indicate a substantial removal of trace organics, while humic substances were increasingly adsorbed by increasing photocatalyst concentration. A UV dose of 15 Wh·L-1 and TiO2 concentrations > 5 g·L-1 were favorable conditions for photocatalytic oxidation resulting in the removal of most of the trace organics, especially chlorinated phosphate flame retardants. Also humic substances were efficiently removed under these conditions. Photocatalytic oxidation is thus a promising process for advanced greywater treatment prior to groundwater recharge. Addition of powdered activated carbon did not improve trace and bulk organics removal by photocatalysis with a UV dose of 15 Wh·L-1 and with photocatalyst concentrations > 5 g·L-1.

Greywater Management in Bahraini Schools, Jaw School-Case Study

The greywater management by treating and reusing is an important issue to provide a new source of water that will not cost as much as using clean water.In general,the water demand in the world is increasing with the increased population,thus it can lead to a water crisis.To reduce the effect of this problem,greywater treatment system can be applied.The greywater in schools is gone to waste every single day,so to provide a logical,cheap and effective solution to manage this problem is to treat and reuse greywater in irrigation,since it does not necessarily need clean water.The aim of this manuscript is to manage and reuse the greywater to reduce the water crises,design an economical greywater system that will act as an investment to the school,and decrease the pressure on sewage system.The paper also aims to identify the wastewater characteristics generated from schools.Therefore,three samples of greywater from water basins and three samples from the kitchen were collected to test and analysis.The analysed parameters are BOD(Biochemical Oxygen Demand),COD(Chemical Oxygen Demand),pH,SO4,TDSs(Total Dissolved Solids),Cl,turbidity,Ca,Mg,NO3 and TH(Total Hardness).The results showed that,the samples collected from the basins are in the accepted range,however the samples of the kitchen have a higher concentration in SO4,BOD,turbidity and nitrate,therefore the greywater generated from the kitchen has been excluded from the greywater system.In terms of the cost,the results indicated that the payback cost could be returned in three years.

Rapid Method for Greywater Treatment and Their Potential Reuse in Agriculture

Greywater, a type of wastewater, may be hazardous to human health and ecosystems. Greywater is a large fraction of wastewater that needs adequate attention for remediation and reuse in the agricultural sector so that a part of the water problem can be sorted out. This study aims to develop a rapid method for greywater treatment and reuse in agriculture. A microfilter consisting of sand, clay, organo-clay, charcoal, and biochar was designed and tested for greywater treatments. Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Kjeldahl Nitrogen (TKN), Total Dissolved Salts (TDS), Electric Conductivity (EC), turbidity and pH values were measured before and after using the microfilter. Results showed tremendous removal efficiency of BOD, COD, TKN, by using the developed microfilter. The microfilter was also effective in treating and placing pH, EC and TDS in the acceptable range for suitable agricultural use. Using the treated greywater for irrigation in corn, tomato seedlings showed increased growth compared with the control group (plants irrigated with tap water). This microfilter treatment was economical, safe, easy to handle and easily applicable. These encouraging results suggest the application of this method in many countries for solving the water scarcity problem.

Purification Potential of Local Media in the Pre-Treatment of Greywater Using Vertical Biofilters under Sahelian Conditions

Several on-site greywater treatment systems are under development including biofiltration, whose efficiency is influenced by the filter media. Therefore, the main objective of this study was to evaluate the influence of the type of filter media and their grain size in the removal of organic and microbial pollutants from greywater. Hence, three types of local filter media of different grain size were used for the pre-treatment of greywater. Their removal potential and clogging time were evaluated and compared. The results indicated that the type of filter media and the grain size have an influence on the elimination of organic and microbial pollution from greywater. Indeed, sand of 1 - 2 mm in size obtained the highest removal efficiencies of organic pollutants (67.35% and 78.04% for COD and BOD5 respectively) and microbial indicators (2.07, 1.77 and 2.27 log. units for E. coli, fecal coliforms and enterococci respectively). Although media of fine texture enhanced the removal efficiencies, they experienced significant clogging problems. To overcome these limitations while enhancing the removal efficiency, 1) pre-treatment stage with coarse materials followed by a treatment with finer materials or 2) the use of a combination of fine and coarse materials should be considered.

Performance of Common Reed(Phragmites australis)in a Constructed Wetland for Greywater Treatment in Akure,Nigeria

Shortage of freshwater is becoming a growing problem in both dry and semi-dry regions of the world,hence the need to make use of other source of water for agricultural production.The study was conducted to examine the performance of common reed in a constructed wetland for greywater treatment in Akure,Nigeria.Raw greywater was collected from Jadesola Hostel,Federal University of Technology,Akure,and pretreated through a combination of gravel of diameters<32 mm,24 mm and 16 mm with fine sand of diameter 0.2 mm arranged accordingly.The filtered water was thereafter released to a plastic constructed wetland(CW)which also consisted of same combination of layers of gravel and sand with common reed planted on it for complete treatment.The raw and treated greywater were analyzed for Biochemical Oxygen Demand(BOD),Chemical Oxygen Demand(COD),Total Dissolved Solid(TDS),and heavy metals.It was discovered that CW planted with common reed was effective in the treatment of greywater with reduction in BOD by 91.4%,COD by 91.5%and TDS by 38.7%.CW had appreciable removal effect on heavy metals with reduction in:manganese(Mn)from 0.100 ppm to 0.012 ppm,iron(Fe)from 0.014 ppm to 0.002 ppm,lead(Pb)from 0.05 ppm to 0.001 ppm and zinc(Zn)from 0.154 ppm to 0.148 ppm.Therefore,the use of common reed in constructed wetland for greywater treatment is recommended for farmers involved in irrigation with greywater,especially during dry seasons,and most importantly under the rising global water scarcity due to climate change.

Greywater reuse as a key enabler for improving urban wastewater management

Sustainable water management is essential to guaranteeing access to safe water and addressing the challenges posed by climate change,urbanization,and population growth.In a typical household,greywater,which includes everything but toilet waste,constitutes 50e80%of daily wastewater generation and is characterized by low organic strength and high volume.This can be an issue for large urban wastewater treatment plants designed for high-strength operations.Segregation of greywater at the source for decentralized wastewater treatment is therefore necessary for its proper management using separate treatment strategies.Greywater reuse may thus lead to increased resilience and adaptability of local water systems,reduction in transport costs,and achievement of fit-for-purpose reuse.After covering greywater characteristics,we present an overview of existing and upcoming technologies for greywater treatment.Biological treatment technologies,such as nature-based technologies,biofilm technologies,and membrane bioreactors(MBR),conjugate with physicochemical treatment methods,such as membrane filtration,sorption and ion exchange technologies,and ultraviolet(UV)disinfection,may be able to produce treated water within the allowable parameters for reuse.We also provide a novel way to tackle challenges like the demographic variance of greywater quality,lack of a legal framework for greywater management,monitoring and control systems,and the consumer perspective on greywater reuse.Finally,benefits,such as the potential water and energy savings and sustainable future of greywater reuse in an urban context,are discussed.

On-line batch production of ferrate with an chemical method and its potential application for greywater recycling with Al(Ⅲ) salt

Ferrate（Ⅵ ） salt is an oxidant and coagulant for water and wastewater treatment. It is considered as a possible alternative method in greywater treatment. However, challenges have existed in putting ferrate（Ⅵ ） technology into full-scale practice in water and wastewater treatment due to the instability of ferrate solution and high production cost of solid ferrate products. This study demonstrated a new approach of greywater treatment with on-line batch production of Fe（Ⅵ ） to which Fe（Ⅲ ） salt was oxidized at a weak acidity solution. A series of experiments were conducted to investigate the effect of Fe（Ⅵ ） on light greywater（total organic carbon（TOC） = 19.5 mg/L） and dark greywater（TOC = 55 mg/L）treatment under different conditions with varying p H and Fe（Ⅵ ） doses. In addition, the combination use of Fe（Ⅵ ） and Al（Ⅲ ） salts was proved to be more efficient than using the Fe（Ⅵ ） salts alone at greywater recycling. The optimum dosage of Fe（Ⅵ ）/Al（Ⅲ ） salts was 25/25 mg/L for light greywater, 90/60 mg/L for dark greywater, respectively. The TOC values of both light greywater and dark greywater were reduced to less than 3 mg/L with the dosages.The cost for treating greywater was 0.06–0.2 $/ton at ferrate（Ⅵ ） dosage of 25–90 mg/L and0.008–0.024 $/ton at AlCl3 dosage of 25–60 mg/L. The full operating cost needs further assessment before the Fe（Ⅵ ）/Al（Ⅲ ） technology could be implemented in greywater treatment.

A Cradle-to-Cradle Novel Approach for Wastewater Management in Sustainable Urban Communities

Water, a valuable resource to human lives, is being abused and driven to scarcity. This scarcity is leading some countries and areas to face difficulty in accessing drinking water. As the UN recently stated “by 2050 water shortages and harder access will be reached by around 2/3rd of the world total population” [1], thus, there is a high need to treat and reuse wastewater for domestic purposes, which will lead to less reliance on fresh water as an initial water source. Greywater—defined as the water produced in domestic houses including sinks and bathroom showers, and excluding any blackwater mix which is collected from toilets—is a type of wastewater. Greywater accounts for up to 75% of the daily water produced [2] while it has fewer contaminants when compared to blackwater. This makes greywater a focal point for treatment, and reusing to conserve fresh water and approach net zero water concept. Even though the definition of greywater is the same globally, its criteria can differ from one country to another, from one building to another, or even from the same person’s usage along the day. Accordingly, several treatment methods evolved over years aiming at treating the produced greywater for reuse mainly in irrigation and toilet flushing. The objective of this paper is to demonstrate a novel net zero wastewater approach applying cradle-to-cradle concept for urban communities;while also proposing a sustainable greywater treatment technique that is environmentally friendly, cost-effective and socially acceptable.

Commercial Laundry Water Characterisation

Surfactants are the major active ingredients of laundry detergents. Therefore, special attention should be focused on the treatment and disposal of laundry wastewater. The aim of this study was to characterise the wastewater from a commercial laundry over 30 days. Physicochemical analyses were performed, monitoring the content of nitrogen, phosphate, heavy metals, linear alkylbenzene sulphonate (LAS), volatile organic acids and alcohols. The pH was approximately 5.6 and the COD approximately 4800 mg·L-1. The average concentrations of sulphate, sulphide, N-ammoniacal organic nitrogen compounds and heavy metals were below the maximum limit, in accordance with local and national environmental legislation, and the average total suspended solids was 0.08 g·L-1. Among the metals analysed, iron was observed with the highest concentrations (0.037 mg·L-1 and 0.72 mg·L-1). Phosphate was detected in 93% of samples (94.65 mg·L-1 average). LAS was detected in all samples (12.24 mg·L-1 to 1023.7 mg·L-1). Thirty-three different xenobiotic organic compounds were identified in the laundry wastewater with the qualitative screening. The major groups of the compounds were fragrances, preservatives, solvents and some surfactants. Although the characterisation indicated low values for many parameters, this does not eliminate the need for specific treatment before its disposal at the sewage system.

Smart Sewers 1: Sewer Configuration at Rural Houses

The layout of houses and other buildings impacts the way in which foul sewer pipework is positioned internally and externally. Less water to waste through conservation measures reduces the distance that gross solids transfer in sewers and increases the number of sewer blockages. Dwelling houses are often laid out where the solids from faecal flushes are at the head of the sewer line with other flows entering downstream. Discharges from appliances such as washing machines, dishwashers, baths, showers and kitchen/utility sinks are often not utilised in the transfer of the gross solids when they enter downstream of the faecal flushes. At present, no recommendations or specific design guidance exist regarding the design of internal building layouts relating to sewer configuration requirements. Furthermore, to date, no specific research exists which examines pipeline configuration scenarios outside buildings in terms of the link between multiple grey water discharge points and solid transfer in a sewer system. The aim of this study was to investigate sewer layout at houses in terms of maximising greywater flow in relation to solid transfer. This study showed that smart sewers are needed which utilise all the foul water leaving a building as it was found that up to 100% of greywater in some instances is completely missed out in terms of solid transfer. Consequently, optimal sewer design is far from being realised and internal building layouts should be designed with consideration of the faecal flushes and greywater flows.

Sanitation By-Products Used for Lettuce (<i>Lactuca sativa</i>L.) Production: Quantitative Microbial Risk Assessment

Sanitation by-products (i.e. greywater, human urine and toilet compost) reuse for agriculture presents an opportunity to enhance food security while overcoming water scarcity and fertilizers issues in developing countries. However, the risks to health from farmers and consumers’ exposure to pathogenic micro-organisms persistent in sanitation by-products has hindered their popularity in these regions. This study was conducted to apply a quantitative microbial risk assessment to estimate the annual risk probability of Salmonella infection associated with these sanitation by-products reuse for lettuce production and explore options for health risk reduction. Risk was performed a Monte Carlo simulation for farmers and consumers. The exposure routes were contaminated soil ingestion, urine/greywater/compost ingestion and lettuce consumption without washing. Results showed that the annual infection risks of Salmonella through ingestion contaminated soil associated with urine and compost were typical scenario: 9.04 × per-person-per-year (pppy) and 2.97 × pppy, respectively, are higher than the WHO benchmark (≤1.0 × pppy). Conversely, those contaminated from greywater were 6.83 × pppy are meet the WHO benchmark. On the other hand, annual risks through lettuce consumption fertilized with urine (1.20 × pppy) were less than the risks from compost (6.20 × pppy) and greywater (7.76 × pppy). Moreover, the annual risks of infection from greywater ingestion (1.77 × pppy) exhibits a much higher risk than that urine ingestion (6.20 × pppy) approximately two orders of magnitude, and which are higher than the WHO tolerable limit of risk. The risk assessment outcomes of using sanitation by-products to lettuce production should be promoted with proper awareness of the risk by farmers and consumers.