Triclocarban removal in agricultural runoff using biochar-microbe-augmented bioretention drainage systems: Performance and role of microbial community.

Triclocarban (TCC) is a widely used antimicrobial agent and has been detected as an environmental contaminant in agricultural areas. We aimed to remediate TCC-contaminated agricultural runoff using a bioretention drainage ditch system augmented with biochar (BC), free cells (FC), and biochar-immobilized cells (IC). In a batch test, FC achieved the highest removal efficiency (83 %), followed by IC (62 %) and BC (58 %). In a long-term system, IC and FC exhibited comparable TCC removal efficiencies (33-35 %), whereas BC removed TCC only 20 %. The TCC reduction was achieved through biodegradation as well as adsorption by biochar and extracellular polymeric substances (EPS). The adaptive responses of the microbes to TCC toxicity included cell shrinkage and appendage formation. Comamonas and potentially Alcaligenes contributed to the TCC degradation. Azospira and Flavobacterium were likely involved in EPS production. Overall, our findings suggest that biochar-microbe-augmented bioretention drainage ditch systems hold promise for cleaning up contaminated agricultural runoff.