997Environmental Technology, Vol. 25. pp 997-1008© Selper Ltd, 2004QUALITY OF INDIVIDUAL DOMESTIC GREYWATERSTREAMS AND ITS IMPLICATION FOR ON-SITETREATMENT AND REUSE POSSIBILITIESE. FRIEDLERFaculty of Civil and Environmental Engineering, Technion, Haifa 32000 Israel(Received 6 May 2004; Accepted 6 June 2004)ABSTRACTA sampling campaign was conducted in order to characterise the quality and quantity of individual domestic greywaterstreams. Based on the results, various scenarios of inclusion and / or exclusion of different greywater streams wereexplored, and their implication for on-site greywater treatment and reuse options are discussed. Domestic greywater wasfound to contribute as much as 55-70% of the specific daily load of TSS and BODt in municipal sewage. The kitchen sink wassignalled out as a major contributor of VSS, CODt, and BODt with 58%, 42% and 48%, of their total daily load respectively.The washing machine was established as a significant contributor of sodium, phosphate and CODt (40%, 37% and 22% of thetotal load). The dishwasher, although contributing only 5% of the flow, was found to be a significant contributor ofphosphate and boron. The wash basin was found to be the least polluting appliance. As "demand" for greywater within theurban environment is lower than its "production", it is logical to recycle only the less polluted greywater streams. In order toexplore the consequences of the above concept on discharge volume, pollutants loads and concentrations, 18 scenarios werestudied, in each at least one stream was excluded from the combined greywater stream. Exclusion of the joined stream of thekitchen sink plus the highly polluted streams of the washing machine (wash + 1st rinse) and dishwasher (pre-rinse + wash)significantly improved greywater quality, with the advantage of leaving enough greywater to be reused (65-70 l/c/d).Keywords: Greywater characterisation, stream separation, on-site treatment, alternative water resource, sustainable water useINTRODUCTIONUrban water demand in many regions around theworld grows continuously as a result of two main processes,namely: urbanisation and increasing specific water demand.This ever-increasing demand leads to water scarcity even inplaces that were traditionally conceived as water ampleregions (Europe, Japan, etc.). Thus, new water sources have tobe developed, e.g. exploitation of more distant (surface water)and deeper (groundwater) sources, construction of new dams,and seawater desalination. Not only that the cost of utilisingthese "new" sources is expected to be higher than the cost of“conventional” water sources, but it is expected to causeincreasing negative environmental effects. Therefore, inparallel with - or prior to - developing "new" water sources athorough revision of the urban water consumption is requiredin order to enhance utilisation efficiency, to promote watersaving measures, and to reuse water as an alternativeresource. A promising option to the latter is on-site greywaterreuse, which may have a significant role in reducing theoverall urban water consumption.Domestic in-house specific water demand inindustrialised countries approximates 100-150 l/c/d(litre/capita/day), of which 60-70% is transformed intogreywater, while most of the rest is consumed for toiletflushing and released as blackwater. Greywater reuse fortoilet flushing can reduce the in-house net water consumptionby 40-60 l/c/d, leading to 10-20% reduction of the urbanwater consumption, which is significant especially underwater scarcity situation. Additional reduction can be achievedby reusing greywater for garden irrigation which is aconsiderable water consumer in some semi arid regions(Australia, California, Israel, etc.). For example, Friedler andGalil [1] showed that in the year 2023 with a moderatepenetration ratio of greywater reuse systems of 20-30%(percentage of houses having greywater reuse units installed),reuse of greywater in the urban sector in Israel (projectedpopulation 10*106 people) could save 30-55 MCM y-1 (millioncubic meters/year) – 25-45 and 5-10 MCM y-1 in toilet flushingand garden irrigation respectively. This amounts to about 5%of the total future urban water demand in the country, andequals the capacity of a medium size seawater desalinationplant.Indeed, the concept of domestic greywater reuse has998been investigated lately especially in the EU, Japan USA andAustralia. However, since it is relatively new, full-scalesystems are not common, and even less were tested for a longtime period [2, 3, 4, 5, 6, 7].Although conceived to be “clean,” greywater may behighly polluted, with COD concentrations of up to a 1,000 mgl-1, faecal coliforms of about 104-108 CFU/100 ml, andsignificant concentrations of detergents and salts (boron,sodium and chlorides) etc. [8, 9, 10, 11, 12]. Thus, greywatermay pose health risks and exhibit negative environmental andaesthetic effects, especially in warm climates where higherambient temperatures increase organic matter degradationand enhance pathogens regrowth. As a result of the above, itis important to adequately characterise the quantity andquality of domestic greywater in order to better design andoperate on-site treatment and reuse systems which arebecoming more common worldwide.This paper describes the results of a sampling campaignconducted in order to characterise individual domesticgreywater streams and to assess their relative discharge andpollutants contribution. Based on the survey results, variousscenarios of inclusion and / or exclusion of differentgreywater streams are explored and their implication for on-site greywater treatment and reuse options are discussed.METHODSA sampling campaign was performed in order tocharacterise the quantity and quality of all greywater streamsdischarged from domestic appliances (totaling 6 appliances,details are given in Table 1). About 150 samples were taken,whereby each time a sample was taken, the discharge volumeof the event was measured. Every sample was analysed for 20parameters in accordance with Standard Methods [13]: pH,electrical conductivity (EC), chlorides, sodium, boron,ammonia, phosphate, total solids, volatile total solids,suspended solids (total & volatile), chemical oxygen demand(COD) (total & dissolved), biochemical oxygen demand(BOD) (total & dissolved), total organic carbon (TOC) (total &dissolved), total oil, anionic detergents (MBAS) and faecalcoliforms (FC). The samples were further analysed by ICP
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