Treatment of Greywater by Geotextile Filter and Intermittent Sand Filtration

Abstract

Intermittent sand filtration (ISF) is an efficient system for treatment of greywater; however, the high quality of effluent and the simple setup contrast with the high failure rate due to clogging of surface layers. The efficacy of several polypropylene nonwoven geotextiles (apparent opening size from 0.10 to 0.18 mm) used as primary treatment filters to remove suspended particles from domestic greywater and the effects of this pretreatment in the performance of fine and small media size (0.3 and 0.6 mm) ISFs was examined. Results showed geotextile achieved SS removal rates from 25 to 85% and COD from 3 to 30%; although the portion larger than 75 µm was removed at higher rates (55–90%), particles smaller than the nominal pore size of the filter were also captured. Geotextile used as pretreatment resulted in improvement of lifetime of the ISFs over an experimental run of 60 days. The vertical profile of volatile organic matter in the ISFs was evaluated at the end of the experiment, and it showed a clear reduction in the accumulation of organic material on the top layer of the ISFs, effectively avoiding its early failure by accumulation of solids.