Treatment and reuse of a pesticide-containing wastewater by a combination of physicochemical, biological and membrane processes

Abstract

Proper treatment and reuse of industrial wastewaters are efficient ways to mitigate their environmental impacts. In this work, a pesticide formulation wastewater pretreated by activated carbon was combined with sewage (4:96) and subjected to biotreatment in a lab-scale moving-bed biofilm reactor (MBBR) with 50% media filling ratio and 6h HRT. Throughout 180 days, efficient removal was achieved for organic matter (86%, tCOD) and ammonium (88%). Additionally, the MBBR effluent exhibited higher quality than the water of the river used by the pesticide industry. For evaluating the possibility of wastewater reuse, the effluents from the MBBR (M) and a lubricant industry (L, from the same industrial site) were combined with the river water (R) that feeds the industrial water treatment plant (WTP) and submitted to a lab-scale reproduced WTP: coagulation/flocculation, sedimentation, sand filtration and microfiltration. River water and two combinations (RM: 85:15 and RML: 80:15:5) were assessed. The mixtures improved the efficiency of the lab-reproduced WTP; however, the fouling potential was high (SDI15>5) for reverse osmosis at the end of the WTP. Thus, after microfiltration, two ultrafiltration (UF) membranes (10 and 50 kDa) were tested, producing similar quality water (0.02 NTU, low SDI and color). After UF, the total turbidity and color removals for R, RM and RML were, respectively, 99.87%, 99.84% and 99.81%, and 96.2%, 87.3% and 93.1%. The UF implementation produced stable high-quality water, implying a reduction of RO membrane costs and cleaning frequency, while increasing the permeate flux. Ultimately, complete wastewater reuse was enabled by the proposed chain.