Microbial removal of phenol and ammonium from acidic wastewater using recycled polyurethane: Performance and mechanism

Abstract

Using solid waste as fortifying agent can improve the efficiency of biological treatment of wastewater and solve the problem of difficult treatment of solid waste. In this study, the waste polyurethane was used as the immobilized carrier of strain, and the repair effect of the immobilized system on acidic phenol-containing wastewater was investigated under different conditions and the mechanism of microbial degradation and acid resistance enhanced by the carrier was discussed. The results showed that polyurethane immobilization improved microorganisms' resistance to harsh environments, strain growth, and pollutant removal efficiency in wastewater. Optimizing the culture conditions of the immobilized system increased the average removal efficiency of phenol and NH4+ by 68.77 % and 135.12 %, respectively, compared to the free strain. Additionally, immobilization enhanced the strain's tolerance to phenol, achieving efficient removal of high-concentration phenol-containing wastewater (2200 mg L−1) that free bacteria could not handle. In the MBBR reactor, the immobilized polyurethane-strain Hly3 system operated stably for 20 cycles, removing 95 % of 2000 mg L−1 phenol and 65 % of 100 mg L−1 NH4+. The mechanism by which the carrier improved microbial degradation and acid resistance was studied. It was found that carrier protection, accelerated material transfer, enhanced strain resistance, and increased activity of the acid-resistant reaction system were the main reasons for the improved acid resistance and degradation ability of strain Hly3. From an environmental and economic perspective, recycling polyurethane buffer materials as carriers to immobilize microorganisms offers a cost-effective wastewater treatment solution, also addressing the challenge of difficult solid plastic waste treatment.