Treatment of healthcare facility wastewaters by two dimensional (2D) electrochemical coagulation (ECC), settling and filterability aspects

Abstract

Healthcare facility wastewaters (HCFWWs) are highly toxic and refractory not amenable for biological treatment. Electrochemical coagulation (ECC) is capable of treating such tough and toxic waste streams offering a shortest treatment time ≥75 min with good settling and filterability characteristics. Batch ECC was applied successfully for treatment of real HCFWWs. Two dimensional (2D) aluminum (Al) and stainless steel (SS) electrodes were arranged in bipolar mode applying cell voltages 6, 12, 18 and 24 V for ≥75 min electrolysis time (ET) with an inter electrode spacing of 10 mm having an specific electrode area to volume (SA/V) of 20 m2/m3. The optimum applied cell voltage using Al electrodes was 12 V showing 88% removal of COD, 47% nitrate, 92% phosphate, 42% sulfate, 74% color and 70% odor free clear water worth a reclamation. SS electrodes removed 82% of COD, 46% nitrates, 88% phosphate, 52% sulfates, 71% color and 70% odorless supernatant. Batch ECC for optimum 12 V were conducted for discrete ET using Al and SS for 5 min time interval up to 60 min to obtain intricate technical information. COD removals of 87.5% and 87.23% were achieved meeting the pollution control limits of 250 mg/L using 2D Al and SS electrodes within 20 min ET in discrete time ECC studies with simultaneous color removal of 74.31% and 71.92% respectively. Good sludge settling patterns were obtained for SS. Sludge volume index values of 79.36 were obtained for Al and 260.80 for SS at 12 V at 10 min ET and Centrifugal settleability index values at the same voltages were 86.89% and 96.08% for Al and SS. ECC sludge obtained using 12 V with SS showed good filterability with α (specific cake resistance) value of 4.78 × 1014 m kg−1 and Rm (resistance of the filter medium) value of 5.225 × 108 m−1. Agar plate count values were <10 CFU/mL for Al and <5 CFU/mL for SS.