Treatment of high-strength pharmaceutical wastewater by electrocoagulation combined with anaerobic process

Abstract

This article discusses a combined treatment system comprising electrocoagulation (EC) as a pre-treatment followed by anaerobic fixed film fixed bed reactor (AFFBR) for treatment of high strength pharmaceutical wastewater. The effect of various operating parameters such as pH, current density and electrolysis duration on COD, BOD and colour removal was studied. The maximum removals for COD, BOD and colour under optimal operating conditions i.e. pH 7.2, current density (CD) of 80 A/m2 and electrolysis time of 25 minutes were 24%, 35% and 70.25% respectively. Increase in current density has resulted in decrease in electrolysis duration with marginal improvement in treatment efficiency. The efficiency of removal is discussed in terms of kg CODr A−1m−2h−1 and energy consumption as Wh kg−1CODr. The effluents obtained after EC were treated by AFFBR at various organic loading rates (OLRs) and hydraulic retention times (HRTs). The results indicated removals in the range of 80–90% for COD and 86–94% for BOD respectively, at OLRs between 0.6 to 4.0 Kg COD/m3 d at an HRT of 2 days. The total gas quantity increased with increase in both HRT and OLR up to a loading of 6 Kg COD/m3/d but it did not commensurate with organic load. The results indicated that the combined treatment option is competitive and can be used effectively for high strength wastewaters.