Treatment of a pesticide industry wastewater mixture in a moving bed biofilm reactor followed by conventional and membrane processes for water reuse

The treatment of an industrial wastewater (Efmix) composed of sanitary wastewater (91.5%), pretreated wastewater from pesticide production (3.8%) and hazardous waste landfill leachate (4.7%) was investigated in a moving bed biofilm reactor (MBBR) at a hydraulic retention time of 6 h. Treated effluent was then mixed with surface water (EfMBBR + SW) in a 1:9 volumetric ratio and physicochemical processes (coagulation/flocculation, sedimentation, rapid sand filtration and cartridge filter) were applied in lab-scale to reproduce the industrial water treatment plant and verify the efficiency of the combined process for wastewater reclamation. During the 90 days of operation, the moving bed biofilm reactor was efficient and stable regarding the removal of organic matter (64-89% in terms of chemical oxygen demand) and ammonium nitrogen (89-98%). Even with a fluctuating inlet chemical oxygen demand (230-721 mg/L), values below 100 mg/L were always achieved after biological treatment. Ammonium nitrogen (1.3 ± 0.6 mg NH4+-N/L) and nitrate (20 ± 4 mg NO3⁻-N/L) concentrations in treated wastewater showed that nitrification took place without inhibition throughout the bioreactor operation. Advanced treatment results indicated that a microfiltration or ultrafiltration unit must be coupled to the existing conventional reverse osmosis pretreatment in the water treatment plant in order to improve water quality concerning SDI15, turbidity and color, and thus allow for total reclamation of the industrial complex wastewater. An integrated conventional-microfiltration/ultrafiltration system could achieve high turbidity (99.9%) and apparent color (96.7%) removal to produce high quality water for reverse osmosis, minimizing membrane fouling problems and, consequently, the operational costs.