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At present, a limited number of studies have been reported on LGW using sand filters. Ghaitidak & Yadav (2015) examined the effect of coagulants under variable pH conditions. In the present scenario, the technologies are developed just to check the efficiency of a particular system. There is a need to develop technologies by targeting the type of reuse (e.g., agriculture, gardening, flushing, washing, etc.). It is observed that a single method/technology is not capable of meeting the entire reuse standards, so there is a need to develop a flow diagram with a combination of different technologies by targeting the type of reuse. A summary of reported research on on-site GW treatment by filtration and use of coagulants is given in Table 1.

Table 1

Summary of reported research on on-site greywater treatment by filtration and use of coagulants

ReferenceMain featuresMain conclusionsRemarks
Filtration 
 Finley et al. (2009)  Tested bath, shower, washing machine GW No significant difference in contamination levels was observed between crops irrigated with tap water, untreated GW, and treated GW Results reinforce the potential of domestic GW as an alternative irrigation source 
Treatment using PST (HRT 8 h) followed by coarse filtration (HRT 24 h)  Study was not referred to any reuse standards 
Tested impact of irrigating vegetable crops  Adopted very high HRT 
 Mandal et al. (2011)  Tested bath, wash basin GW Concluded that GW generated from a household is self-sufficient to irrigate a small garden. Study conducted for 2 months (May and June) 
Treatment using filtration followed by aeration and disinfection  Tested only two samples 
 Katukiza et al. (2014)  Tested bath, kitchen, and laundry GW Escherichia coli log removal was >3 but could not satisfy WHO standards Tested in batch mode 
Treatment using PST followed by filtration  Quantity treated was limited to 40 L/d 
Coagulants 
 Friedler & Alfiya (2010)  Tested bath, washbasin GW Most of the removal occurred in the coagulation-sedimentation step, while the filter acted as a polishing unit Involves large electricity consumption 
Treatment using ferric chloride coagulation, sedimentation and filtration  Operated in semi-batch mode 
Doses reported in terms of Fe   
 Kariuki et al. (2011)  Tested kitchen, laundry, hand basin greywater GW treatment system could produce effluent complying with pathogen limit in the referred standards Alum dose was not optimized 
Pilot-scale study  Economic evaluation was not reported 
Treatment using alum coagulation followed by disinfection  Important reuse parameters like BOD5, TSS were not monitored 
ReferenceMain featuresMain conclusionsRemarks
Filtration 
 Finley et al. (2009)  Tested bath, shower, washing machine GW No significant difference in contamination levels was observed between crops irrigated with tap water, untreated GW, and treated GW Results reinforce the potential of domestic GW as an alternative irrigation source 
Treatment using PST (HRT 8 h) followed by coarse filtration (HRT 24 h)  Study was not referred to any reuse standards 
Tested impact of irrigating vegetable crops  Adopted very high HRT 
 Mandal et al. (2011)  Tested bath, wash basin GW Concluded that GW generated from a household is self-sufficient to irrigate a small garden. Study conducted for 2 months (May and June) 
Treatment using filtration followed by aeration and disinfection  Tested only two samples 
 Katukiza et al. (2014)  Tested bath, kitchen, and laundry GW Escherichia coli log removal was >3 but could not satisfy WHO standards Tested in batch mode 
Treatment using PST followed by filtration  Quantity treated was limited to 40 L/d 
Coagulants 
 Friedler & Alfiya (2010)  Tested bath, washbasin GW Most of the removal occurred in the coagulation-sedimentation step, while the filter acted as a polishing unit Involves large electricity consumption 
Treatment using ferric chloride coagulation, sedimentation and filtration  Operated in semi-batch mode 
Doses reported in terms of Fe   
 Kariuki et al. (2011)  Tested kitchen, laundry, hand basin greywater GW treatment system could produce effluent complying with pathogen limit in the referred standards Alum dose was not optimized 
Pilot-scale study  Economic evaluation was not reported 
Treatment using alum coagulation followed by disinfection  Important reuse parameters like BOD5, TSS were not monitored 

BOD5, 5-day biochemical oxygen demand; TSS, total suspended solids; PST, plain settling; HRT, hydraulic retention time.

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