Removal of Pesticides from Water Using Anaerobic-Aerobic Biological Treatment

The biodegradability of wastewater containing priority pollutant pesticide [Vydine or triadimenol (C(14)H(18)CLN(3)O(2))] in different bio-reactor configurations was investigated. Two laboratory scale biological reactors were employed: one reactor under aerobic condition and the other under anaerobic condition. The aerobic reactor was operated at an ambient temperature [(22 +/- 2)degrees C], while the anaerobic reactor was run in the lower mesophilic range [(30 +/- 2)degrees C]. The effect of pesticide concentration, hydraulic retention time (HRT), and co-substrate on the treatment process was explored, using glucose as a supplemental carbon substrate. More than 96% pesticide was removed after an acclimation period of approximately 172 d (aerobic) and 230 d (anaerobic). The aerobic reactor achieved complete Vydine utilization at feed concentrations up to 25 mg-L(-1). On the other hand, the anaerobic reactor was able to degrade 25 mg-L(-1) of Vydine. Moreover, glucose was consumed first throughout the experiment in a sequential utilization pattern. The combination of anaerobic and aerobic biological processes yielded higher biomass concentration and lower retention time than individual units. The biomass in the combined reactors was first acclimated with the corresponding pesticide. Then, the target pesticide, at a concentration of 25 mg.L(-1), was sequentially treated in a semi batch mode in the reactors. HRT studies showed that 24 h HRT of aerobic and 12 h HRT of anaerobic were the optimum combination for the treatment of simulated wastewater containing Vydine, which produced Vydine effluent at concentration below 0.1 mg-L(-1). The optimum ratio of substrate (Vydine) to co-substrate (glucose) was 1:100.