The utilisation of chemical coagulants and flocculant raised concerns, especially in the field of environment and ecology. The utilisation of chemical coagulants and flocculants also produces non-biodegradable sludge, which causes changes in pH stability in water bodies from the released sludge, toxicity to aquatic organism, decreased root elongation of plants and inhibition of seed germination. To overcome these issues, the development of biodegradable coagulants/flocculants can become a green technological solution. Bioflocculants are observed as an alternative to chemical flocculants due to their comparable efficiencies. Additionally, they are biodegradable, eco-friendly, and safe to handle. The identification and production of novel bioflocculants has gained much attention worldwide and extensively reported. Amongst all, bacteria receive the most attention because of its availability and ability to produce bioflocculants with many specialties.
Several biocoagulants/bioflocculants that originated from several sources have already been developed in the past decade to be applied in wastewater treatment. Moringa oleifera showed up to 96.23% efficiency of turbidity removal in low turbid water treatment. Chitosan extracted from mushroom exhibited its capability in COD removal of up to 98%. The characteristics of high turbidity and COD content from aquaculture effluent and the performance of Moringa oleifera in assisting the removal of COD as a bioflocculation agent has been reported. The high turbidity, suspended solids and organic compound parameters from aquaculture effluent that may contribute to surface water pollution also highlighted. In addition, the potential of algae harvesting from aquaculture effluent by using bioflocculant to produce biodegradable and readily-used sludge has also been reviewed.
Many studies also reported the production of bioflocculant from bacteria isolated from different sources, including Citrobacter youngae GTC 01314 from laboratory culture, Bacillus pumilus JX860616 from coastal area, B. agaradhaerens C9 from lake area, Streptomyces platensis from dam area and Pseudomonas aeruginosa strain IASST201 from activated sludge. Although several potential bioflocculants have already been analysed, studies on bioflocculant produced from isolated bacteria from aquaculture industry are still limited to date. Even though aquaculture effluent contributes to surface water pollution from its high suspended solid characteristic, the isolation and characterisation of potential bioflocculant-producing bacteria from aquaculture effluent, which may provide alternative technology in treating aquaculture effluent, is still rare at present.
Serratia marcescens is a gram-negative, rod-shaped bacteria that can produce red pigmentation in room temperature. This species can also produce biosurfactant while possessing capability in hydrocarbon degradation; however, its capability in producing bioflocculants has not been widely explored yet. Bioflocculant produced by this bacterium showed a great potential in removing turbidity from highly turbid water. The produced bioflocculant performed better in high-turbidity water compared with the low-turbidity water, as indicated by higher flocculation activity. Bioflocculant dose of 5% v/v at a 2:3 ratio of bioflocculant to CaCl2 was the optimum for turbidity removal. Increasing the bioflocculant dose did not contribute significantly to the flocculation activity. The highest flocculation activity of 72.5% along with the decreasing turbidity from 5000±0 to 1040±142 NTU was attained in this study. The FT-IR spectrum analysis and the value of zeta potential indicated that the produced bioflocculant can be categorised as anionic bioflocculant with particle bridging subjected as the main mechanism in turbidity removal.
Penulis: Muhammad Fauzul Imron, S.T., M.T.
Link artikel:
https://www.sciencedirect.com/science/article/abs/pii/S2214714421002816
