Greywater treatment for reuse: comparison of reuse options using analytic hierarchy process

The objective of the present study was to: (i) examine the performance of two-stage sand filtration and the effect of coagulants on greywater (GW) characteristics; (ii) assess the quality of treated GW for reuse; and (iii) compare reuse options using the analytic hierarchy process (AHP). Four treatment options were examined on site. The first option was related to two-stage sand filtration (TSF) and the other three options were related to coagulation/flocculation using alum, polyaluminium chloride (PAC), and ferric chloride (FeCl3). The setup was constructed close to the GW source of a student hostel located at Sardar Vallabhbhai National Institute of Technology (SVNIT), Surat. Treated GW was safe for reuse in restricted access area irrigation (as per United States Environmental Protection Agency standards), for discharge into land for irrigation, and for industrial cooling (as per Central Pollution Control Board standards in India). All four treatment options were compared using AHP. Comparison was made in two ways: (1) comparison on the basis of the effluent quality produced and (2) comparison on the basis of removal of parameters. The selection string on the basis of the effluent quality was TSF-PAC treatment-alum treatment-FeCl3 treatment, and that on the basis of removal of parameters was TSF-PAC treatment-FeCl3 treatment-alum treatment.