Treatment and Recycling Strategies for Greywater Originated from Bathrooms

Abstract

Greywater treatment and reuse have emerged as sustainable and cost-effective alternatives to address water scarcity. Conventional treatment methods, such as membrane filtration and biological systems, are often limited by high cost and sensitivity to operational variations. This study investigates an integrated treatment approach combining coagulation–flocculation, filtration, and disinfection for greywater generated from laundry and bathing sources.

Alum and a high molecular weight polyelectrolyte were used as coagulant and flocculants, respectively. Process parameters were optimized using Response Surface Methodology (RSM). The optimum dosages were found to be 9 mg/L alum and 0.8 mg/L polyelectrolyte, with mixing speeds of 140 rpm (rapid) and 18 rpm (slow), and an optimal sedimentation time of 70 minutes. A dual media filtration system comprising sand and granular activated carbon (GAC) was optimized with a GAC-to-sand ratio of 0.6.

Column studies revealed that COD removal efficiencies ranged from 62.14% to 75.73% after 1 hour, while MBAS removal reached up to 93.81% under optimal conditions. The study demonstrates that the proposed hybrid system is efficient, economical, and suitable for decentralized greywater reuse applications.

Keywords: Greywater treatment, Coagulation–flocculation, GAC, RSM