Recycled paper mill effluent treatment in a modified anaerobic baffled reactor: start-up and steady-state performance

Abstract

Start-up period is considered to be the most unstable and difficult stage in anaerobic process and usually takes a long time due to slow-degree adaptation of anaerobic microorganisms. In order to achieve a shorter start-up period, a novel modified anaerobic baffled reactor (MABR) has been developed in this study, where each modified baffle has its own characteristics (form/shape) to facilitate a treatment of recycled paper mill effluent (RPME). The results of physico-chemical characteristics showed that effluent from recycled paper mill consisted of 4328 mg L−1 chemical oxygen demand (COD), 669 mg L−1 biochemical oxygen demand and 501 mg L−1 volatile fatty acid. It also consisted of variety of heavy metals such as zinc, magnesium, iron and nickel at concentrations of 1.39, 12.19, 2.39 and 0.72 mg L−1, respectively. Performance of MABR during the start-up period showed that methane production reached 34.7% with COD removal of 85% at steady state. The result indicates that MABR was successfully operated during the start-up period in treating RPME within a period of less than 30 days.