Immobilization of phototroph-derived extracellular polymer for simultaneous removal of antibiotics and heavy metals: A sustainable approach for advanced treatment of secondary effluent

Antibiotic and heavy metal residues in secondary effluent are mainly responsible for the spread of antibiotic-heavy metal resistance genes and cannot be efficiently removed by traditional wastewater treatment processes. A sustainable approach by using alginate immobilized phototroph-derived extracellular polymer (EPS) for simultaneous inducing photolysis of antibiotic (sulfadiazine, SDZ) and adsorptive removal of heavy metal (Cd2+) from simulated secondary effluent was firstly explored. The results showed that immobilization of Rhodopseudomonas palustris-derived EPS (R-EPS-Alginate) led to the fastest SDZ photolysis due to its highest amounts of proteins (3.76 mg/g). With the optimum R-EPS-Alginate dosage of 6 g/L, 60 mg/L of immobilized EPS concentration and pH of 5.6, 86% of the SDZ was degraded within 96 h. 1O2 generated from 3EPS* was mainly responsible for the SDZ photodegradation which was decomposed into less toxic substances. 61% of Cd2+ was immediately adsorbed by R-EPS-Alginate within 60 min with a maximum adsorption capacity of 88.1 mg/g. Cd2+ adsorption moderately enhanced SDZ photolysis, probably due to the generation of CdS, while the latter almostly does not adversely impact the former.