Remediating sulfadimethoxine-contaminated aquaculture wastewater using ZVI-activated persulfate in a flow-through system

Abstract

Antibiotic resistant bacteria can result from the improper discharge of water from the aquaculture farming industry. This calls for the development of a low-cost remediation technology. Our research verified the use of ZVI-activated persulfate (PS) to treat antibiotic-contaminated aquaculture discharge water in a flow-through system. We selected sulfadimethoxine (SDM) as a representative antibiotic residual and tested SDM degradation under varying parameters: activator dose, initial pH, chloride concentration, activator dose and timing. The results demonstrated that increasing the ZVI dosage significantly decreased SDM degradation due to the scavenging effects for the persulfate radical (SO4−). SDM decomposition occurred when SO4− attacked the aniline moiety via electron transfer prior to undergoing hydrogen abstraction/addition on the sulfonamide. A high pH produced the fastest degradation with reaction rates following the order pH 11 > > pH 9 > pH 3 > pH 5. A high Cl− concentration (>100 mM) enhanced SDM degradation because of the production of chlorine radicals. The experiment results from ZVI sequential addition indicated that only a small continual input of ZVI was sufficient to generate SO4− to react with SDM. We used a flow-through concept for the real discharge water that was spiked with SDM prior to treating with PS/ZVI. The results showed that our system was able to remove approximately 68% of SDM from filtered and 74% from unfiltered discharge water. These results provide proof-of-concept that our PS/ZVI system could potentially be developed to remediate antibiotic-contaminated aquaculture wastewater.