Treatment of biodigested coffee processing wastewater using Fenton’s oxidation and coagulation/flocculation

摘要: Abstract Biodigested coffee processing wastewater (CPW) presents a high organic load and does not meet the limits imposed by legislation (namely in Brazil) for discharge into water bodies. Anaerobic digestion generally cannot provide satisfactory matter reduction CPW as significant fraction of recalcitrant compounds still persists treated effluent. So, this study aims to find alternative ways remove refractory from order improve biodegradability reduce toxicity, which will allow its recirculation back anaerobic digester. Three treatment approaches (Fenton’s oxidation - Approach 1, Coagulation/flocculation (C/F) 2, combination C/F with Fenton’s process 3) were selected be applied biodigested achieve that objective. The application Fenton under optimal operating conditions (initial pH = 5.0; T = 55 °C, [Fe3+] = 1.8 g L−1 [H2O2] = 9.0 g L−1) increased (the BOD5:COD ratio raised 0.34 ± 0.02 0.44 ± 0.01 after treatment) eliminated toxicity (0.0% Vibrio fischeri inhibition) along moderate removals (51.3%, 55.7% 39.7% total carbon – TOC, chemical oxygen demand COD biochemical BOD5, respectively). implementation coagulation/flocculation upstream oxidation, best (pH 10–11 [Fe3+] = 250 mg L−1), also allowed slightly increase (from 0.34 0.47) whereas providing higher removal (TOC = 76.2%, COD = 76.5 BOD5 = 66.3% both processes together). 1 3 showed ones, implying similar costs (∼74 R$ m−3/∼17 € m−3) constitute an attractive option managing CPW.