Environmental Technology Vol 25 pp 997 1008 Selper Ltd 2004 QUALITY OF INDIVIDUAL DOMESTIC GREYWATER STREAMS AND ITS IMPLICATION FOR ON SITE TREATMENT AND REUSE POSSIBILITIES E FRIEDLER Faculty of Civil and Environmental Engineering Technion Haifa 32000 Israel Received 6 May 2004 Accepted 6 June 2004 ABSTRACT A sampling campaign was conducted in order to characterise the quality and quantity of individual domestic greywater streams Based on the results various scenarios of inclusion and or exclusion of different greywater streams were explored and their implication for on site greywater treatment and reuse options are discussed Domestic greywater was found to contribute as much as 55 70 of the specific daily load of TSS and BODt in municipal sewage The kitchen sink was signalled 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 the total load The dishwasher although contributing only 5 of the flow was found to be a significant contributor of phosphate and boron The wash basin was found to be the least polluting appliance As demand for greywater within the urban environment is lower than its production it is logical to recycle only the less polluted greywater streams In order to explore the consequences of the above concept on discharge volume pollutants loads and concentrations 18 scenarios were studied in each at least one stream was excluded from the combined greywater stream Exclusion of the joined stream of the kitchen 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 use industrialised countries approximates 100 150 l c d INTRODUCTION litre capita day of which 60 70 is transformed into Urban water demand in many regions around the greywater while most of the rest is consumed for toilet world grows continuously as a result of two main processes flushing and released as blackwater Greywater reuse for namely urbanisation and increasing specific water demand toilet flushing can reduce the in house net water consumption This ever increasing demand leads to water scarcity even in by 40 60 l c d leading to 10 20 reduction of the urban places that were traditionally conceived as water ample water consumption which is significant especially under regions Europe Japan etc Thus new water sources have to water scarcity situation Additional reduction can be achieved be developed e g exploitation of more distant surface water by reusing greywater for garden irrigation which is a and deeper groundwater sources construction of new dams considerable water consumer in some semi arid regions and seawater desalination Not only that the cost of utilising Australia California Israel etc For example Friedler and these new sources is expected to be higher than the cost of Galil 1 showed that in the year 2023 with a moderate conventional water sources but it is expected to cause penetration ratio of greywater reuse systems of 20 30 increasing negative environmental effects Therefore in percentage of houses having greywater reuse units installed parallel with or prior to developing new water sources a reuse of greywater in the urban sector in Israel projected thorough revision of the urban water consumption is required population 10 106 people could save 30 55 MCM y 1 million in order to enhance utilisation efficiency to promote water cubic meters year 25 45 and 5 10 MCM y 1 in toilet flushing saving measures and to reuse water as an alternative and garden irrigation respectively This amounts to about 5 resource A promising option to the latter is on site greywater of the total future urban water demand in the country and reuse which may have a significant role in reducing the equals the capacity of a medium size seawater desalination overall urban water consumption plant Indeed the concept of domestic greywater reuse has Domestic in house specific water demand in 997 been investigated lately especially in the EU Japan USA and and Zn As in most cases the concentrations of these heavy Australia However since it is relatively new full scale metals were below the detection limits the results are not systems are not common and even less were tested for a long shown can be found in 14 All information was stored in a time period 2 3 4 5 6 7 database that contains over 2 000 data entries Although conceived to be clean greywater may be highly polluted with COD concentrations of up to a 1 000 mg RESULTS AND DISCUSSION l 1 faecal coliforms of about 104 1 08 CFU 100 ml and Characteristics of Individual Greywater Streams significant concentrations of detergents and salts boron sodium and chlorides etc 8 9 10 11 12 Thus greywater may pose health risks and exhibit negative environmental and Table 2 presents the average values Avg and the aesthetic effects especially in warm climates where higher standard deviations Std for each parameter appliance ambient temperatures increase organic matter degradation combination with the exception of the washing machine and and enhance pathogens regrowth As a result of the above it the dishwasher for which only the average values are is important to adequately characterise the quantity and presented their variability is discussed later The right hand quality of domestic greywater in order to better design and side of the table shows a compilation of literature data All 4 operate on site treatment and reuse systems which are appliances BT SH WB KS exhibit high variability both in becoming more common worldwide the quantity and quality of effluents as presented by high Std and CV values Std Avg not shown This paper describes the results of a sampling campaign conducted in order to characterise individual domestic As expected the washing machine dishwasher and greywater streams and to assess their relative discharge and kitchen sink were signalled as the major pollutants pollutants contribution Based on the survey results various generators with COD concentration in the order of 1 300 mg scenarios of inclusion and or exclusion of different l 1 BOD up to 700 mg l 1 phosphate up to 500 mg l 1 and greywater streams are explored and their
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