Isolation and characterisation of bioflocculant-producing bacteria from aquaculture effluent and its performance in treating high turbid water

Turbidity is a common pollutant parameter in water and wastewater treatment that can be reduced through flocculation. This research was conducted to characterise and analyse the potential of bioflocculant-producing bacteria isolated from aquaculture effluent. Samples were taken from two different aquaculture farms that represent brackish and freshwater cultures. A total of 21 different colonies were obtained from all samples. Screening of flocculation activity showed the potential of WS5 to be a bioflocculant agent to remove turbidity from artificial turbid water. One variable at a time analysis was performed to assess the capability of WS5 in different initial turbidity and bioflocculant doses. In comparison with low turbid water with 5% v/v bioflocculant dose (in 5000 NTU turbidity), WS5 exhibited better performance in high turbid water, thereby resulting in the most optimum flocculation activity of 72.5%. The increment in bioflocculant dose of up to 10% did not contribute to the flocculation activity significantly. The increment in particle size distribution for the suspension from before to after treatment with bioflocculant provided evidence that the process of flocculation had occurred effectively. Genomic analysis of selected potential bacteria using BLAST and phylogenetic tree has identified WS5 as Serratia marcescens and has been confirmed as a rod-shaped bacterium. FT-IR spectra and zeta potential analysis indicated that the produced bioflocculant is categorised as anionic bioflocculant with polymer bridging suggested as the main mechanism during turbidity removal.