Coffee processing industrial wastewater treatment using batch electrochemical coagulation with stainless steel and Fe electrodes and their combinations, and recovery and reuse of sludge

Abstract

Abstract The efficiency of chemical oxygen demand (COD) and color removal from raw coffee processing wastewater (CPWW) using batch electrochemical coagulation (BECC) treatment process using stainless steel (SS) and iron (Fe) electrode combinations are investigated. Of the combinations: four SS, four Fe, Fe-Fe-SS-SS, Fe-SS-Fe-SS, SS-SS-Fe-Fe, and SS-Fe-SS-Fe; four SS electrodes operated at 23 V having 120 A/m2 current density was found as a good operating condition to achieve ∼87% COD removal from its initial COD of 1,984 mg/L and corresponding color removal of 97.1% (initial color 7,000 PCU). The second best electrode combination, SS-SS-Fe-Fe, had COD and color removals of 75% and 91%. When using polyaluminum chloride (PAC) as aid with different dosages of 20–100 mg/L, 50 mg/L PAC showed maximum COD and color removals of 80% and 92%. Comparison of proximate and ultimate analyses of various solid fuels with CPWW ECC sludge showed its usefulness as a soil supplement and as an adsorbent for reutilization. The solid residue obtained after BECC was characterized using energy dispersive X-ray spectroscopy and other analyses. Summarizing the results, it was concluded that BECC can be effectively used for maximum removal of organics from raw CPWW with clean water reclamations of up to ∼90% using ECC as a novel treatment technique.