Advanced treatment of triazole fungicides discharged water in pilot scale by integrated system: Enhanced electrochemical oxidation, upflow biological aerated filter and electrodialysis

Abstract In this work, a novel integrated system in pilot plant scale of electrochemical oxidation, upflow biological aerated filter and electrodialysis was investigated for high level standard reuse of triazole fungicides discharged water. In order to enhance biodegradable property of discharged water to be easier to recycled, a novel enhanced electrochemical oxidation reactor was designed and applied as pretreatment process. Effects of operating parameters on the performance of each process were studied with the discussion of economic evaluation. The results indicated that the optimal condition was current density of 5 mA/cm 2 , flow velocity of 3 m 3 /h, pH value of 5.0 and without supporting electrolyte. The target species including N-heterocyclic contaminants (tricyclazole, 1H-1,2,4-triazole and propiconazole) were removed over 90% from the discharged water by this process. Within upflow biological aerated filter, the remained COD would decrease further to the level less than 60 mg/L from 250 mg/L. Then the salt was removed efficiently during electrodialysis. Final effluent revealed a very low level of COD of 58.32 mg/L, TOC of 20.56 mg/L, EC 50,48h of 73.1 ± 2.1%, consistent with an excellent removal of the target species of 94.19% tricyclazole, 90.11% 1H-1,2,4-triazole and 100% propiconazole, >99% salt and a low operating cost of $0.85. The excellent performance as well as the low energy consumption confirmed that this integrated system is highly applicable for the advanced treatment of triazole fungicides discharged water.