Insight on how biopolymers recovered from aerobic granular wastewater sludge can reduce the flammability of synthetic polymers

Eco-friendly flame retardants are greatly required to meet the expectations of low-toxicity, environmental compatibility and sustainability. Extracellular polymeric substances (EPS), the biopolymers recovered from excess granular wastewater sludge, have been successfully incorporated into poly(vinyl alcohol) (PVA) by a solution casting method. Self-extinguishment of EPS was observed in a vertical burn test. Positive effects of EPS on the reduction of heat release rate and CO emission of EPS/PVA composites were also demonstrated. The presence of various types of phosphates was detected in the EPS and a possible flame-retardant mechanism has been proposed. The investigation of using granular sludge EPS to reduce the flammability of synthetic polymers may open the possibility of converting wastewater sludge into bio phosphorus-based flame retardants.