Physico-Chemical and Microbial Quality of Greywater from Various Households in Homa Bay Town

Abstract

In recent years concerns over dwindling reserves of ground water and overloaded or costly sewage treatment plants has generated much interest in the reuse or recycling of greywater. Re-use of greywater offers several advantages including a reduction in the demand on potable water supplies. Despite the prevalent direct reuse of greywater, especially in water scarce areas, its quality is not well documented. This study determined the physico-chemical and microbial quality of greywater produced by households in Homa Bay town. Most of greywater generated had a higher electrical conductivity and salinity and lower concentration of dissolved oxygen. Greywater pH values varied widely but were mostly higher than that of clean water. Biological oxygen demand varied widely (410-6250 mg L-1). Total coliform (TC) counts in greywater samples ranged from 1.3 to 7.6 colony forming units (CFU)/ 100 mL while fecal coliform (FC) counts varied between 3000 and 7.4 million CFU/ 100 mL. Field observations showed that the variation in TC and FC counts resulted from differences in the level of households’ personal hygiene, difference in the intensity of greywater reuse and duration of storage. Among the potentially pathogenic bacteria investigated, Salmonella was the most frequent, occurring in 31% of all the greywater samples collected. Vibrio occurred in the least number of samples (9%). The study concludes that greywater produced is most likely to be contaminated by pathogenic bacteria and should therefore be disinfected prior to reuse.