Formation of abiological granular sludge - a facile and bioinspired proposal for improving sludge settling performance during heavy metal wastewater treatment

Heavy metal contamination in wastewater poses a severe threat to the environment and public health. Chemical precipitation is the most conventional process for heavy metal wastewater treatment. However, the flocculent structure of chemical precipitation sludge raises the problem of poor sludge settling performance that is difficult to overcome. Inspired by the biological granular sludge (BGS) formation process, we report here a facile and effective strategy to produce abiological granular sludge (ABGS) to solve this problem. In this procedure, controlled double-jet precipitation was performed to simulate the cell multiplication process in BGS formation by controlling the solution supersaturation. Meanwhile, ZnO seeds and flocculant polyacrylamide were added to simulate the role of nuclei growth and extracellular polymeric substances in BGS formation process, respectively. This procedure generates ABGS with a dense structure, large size and regular spherical morphology. The settling velocity of ABGS can reach up to 3.0cms(-1), significantly higher than that of flocculent sludge (<1cms(-1)).