Greywater treatment using different designs of sand filters

Different designs of sand filter as a secondary treatment step for the treatment of the primary sedimented effluent were studied. Gravel filter down flow (GFDF), gravel filter up flow (GFUF), sand filter down flow (SFDF), gravel filter followed by sand filter (GFSF), and horizontal flow sand filter (HFSF) were used as a secondary treatment step. During the study period, GFDF, GFUF, and SFDF were operated with an influent flow rate of 173 m3/m2/d, while GFSF and HFSF were operated at flow rate of 86.5 m3/m2/d. The final effluent of GFSF and HFSF were found to be complying with the National Regulatory Standards for the treated effluent reuse in irrigation. The residual concentration of COD, BOD5, and TSS for GFSF was 43, 16, and 7.5 while, the corresponding concentration for HFSF was 40, 17, and 9 mg/l, respectively.