Sand filtration for greywater treatment: long-term performance evaluation and optimization by response surface methodology.

Greywater treatment and reuse is getting increasing attention all over the world, and sand filters are one of the on-site greywater treatment alternatives. Effects of media size, media depth and flow rates on the performance of the continuously operated saturated sand filters treating greywater were evaluated in this study. River sand of three different media sizes 0.30-0.60 (fine), 0.60-0.85 (medium), and 0.85-1.18 (coarse) mm was used and sand filters with the same media size were constructed and operated at flow rates of 10 (320 L/m2/day), 20 and 30 L/d. Fine sand media filter operated at a hydraulic loading rate of 320 L/m2/day gave the best performance with 99, 94 and 95% removal of turbidity, BOD and COD, respectively. NH4-N, PO4-P and FC were reduced by 84, 99% and 1.65 log, respectively. An optimization study showed an optimum sand size of 0.68 mm and a hydraulic loading rate of 470 L/m2/day. [ABSTRACT FROM AUTHOR]