Performance of anaerobic–anoxic–aerobic batch fed moving-bed reactor at varying phenol feed concentrations and hydraulic retention time

Abstract

A simulated wastewater containing phenol (1,000–2,500 mg/L), thiocyanate (SCN−) of 800 mg/L, COD (4,200–8,150 mg/L), and ammonia–nitrogen (NH4 +–N) of 500 mg/L was treated in a sequential anaerobic (B1)–anoxic (B2)–aerobic (B3) batch fed moving-bed reactor (MBR) system. Total hydraulic retention time (HRT) was varied from 5 to 10 days with B1 2.5 to 5 days; B2 and B3: 1.25–2.5 days each. In B1, 25–63 % of phenol and 23–53 % of COD removals were achieved and feed phenol above 1,500 mg/L, inhibited COD and phenol removals in B1. In B2, more than 90 % phenol removal was achieved along with COD removal and denitrification. In B2, with increase in phenol loading, though phenol and COD removal rates increased, SCN− removal rate decreased above phenol loading of 0.28 g/L day. In B3, NH4 +–N removal efficiency decreased above loading of 0.24 g NH4 +–N/L day. The overall efficiency of the fed batch MBR system was independent of feed phenol concentration up to 2,500 mg/L at constant total HRT of 6 days. NH4 +–N removal efficiency deteriorated significantly, when total HRT of fed batch MBR was less than 6 days. Modified Stover–Kincannon model showed the best fit for removal of substrates in three reactors and Haldane’s inhibition model predicted NH4 +–N removal in B3.