Removal of standard plate count bacteria from surface water with low turbidity via integrated M. oleifera seed coagulation pretreatment and two-layer cloth filtration process

Abstract

The objective of this study was to develop a two-layer cloth filtration system to remove standard plate count (SPC) bacteria from surface water having low turbidity (< 10 NTU) using M. oleifera seeds as a coagulant during pretreatment. In the first part of this study, 1 μm polystyrene particle was chosen as a surrogate for bacteria, and the effects of the type of cloth, combination of cloth, and M. oleifera seed powder dosage on filtration performance were investigated. It was found that without coagulation pretreatment, the removal efficiency of the particles was less than 40 %; however, coagulation pretreatment significantly improved the efficiency to higher than 99 % for the tightest cloth. It was also observed that the two-layer cloth filtration was effective in preventing the decrease in water permeability caused by the deposition of M. oleifera seed powder on the cloth. In the second part of this study, several coagulation-filtration treatment conditions that demonstrated good filtration performance in the first part of this study were applied to the treatment of pond water to remove SPC bacteria. Experimental data showed that the two-layer cloth filtration with M. oleifera seeds used as coagulant was capable of removing bacteria below 100 CFU mL−1, which is an acceptable drinking water quality criterion recommended by the World Health Organization (WHO). In addition, it was successfully demonstrated that M. oleifera seed powder that was deposited on the filter cloth could be easily removed by gentle surface scrubbing, after which the filter cloth recovered its water permeability.