Optimization of biostimulant for bioremediation of contaminated coastal sediment by response surface methodology (RSM) and evaluation of microbial diversity by pyrosequencing

• Optimization of biostimulant for bioremediation of contaminated coastal sediment.
• RSM used for optimize the BSB size and distance with time interval.
• Biostimulant has enhance the activity of sulfate reducing bacteria.
• SRB diversity in coastal sediments were investigated by pyrosequencing.
• Bacterial diversity were identified at special level.

The present study aims to optimize the slow release biostimulant ball (BSB) for bioremediation of contaminated coastal sediment using response surface methodology (RSM). Different bacterial communities were evaluated using a pyrosequencing-based approach in contaminated coastal sediments. The effects of BSB size (1–5 cm), distance (1–10 cm) and time (1–4 months) on changes in chemical oxygen demand (COD) and volatile solid (VS) reduction were determined. Maximum reductions of COD and VS, 89.7% and 78.8%, respectively, were observed at a 3 cm ball size, 5.5 cm distance and 4 months; these values are the optimum conditions for effective treatment of contaminated coastal sediment. Most of the variance in COD and VS (0.9291 and 0.9369, respectively) was explained in our chosen models. BSB is a promising method for COD and VS reduction and enhancement of SRB diversity.