Examining the methane potential of a fiberbank sediment using two-stage anaerobic digestion system.

Abstract

Prior to the introduction of the environmental protection act by the Swedish government in 1969, the pulp and paper (P&P) industry discharged its process wastewater directly into the waterbodies, leading to an environmental impact in the form of fiberbank sediment. The fiberbank sediment consists of a high amount of biodegradable material and toxic compounds from industrial processing, posing environmental risks such as greenhouse gas (GHG) emission and the release of toxic substances into the surrounding environment. The traditional remediation methods of contaminated sediment such as dredging and landfilling are not feasible due to the potential of emission of GHG in storage. To address this issue, anaerobic digestion (AD) in two stage configurations is proposed as pre-treatment before storage. The feasibility of the proposed solution was evaluated through laboratory experiments using CSTR reactors and by co-digestion of fiber bank sediment with primary sludge from a wastewater treatment facility. In the acidogenesis stage, an 80:20 ratio of fiberbank sediment (FB) to primary sludge (PS) was found to be optimal for maximizing volatile fatty acid (VFA) production. In the methanogenesis stage, 5% of digestate from the acidogenic reactor was mixed with 95% PS on VS basis. The result showed statistically significantly higher volumetric methane production (VMP) of the test reactor (5.1 ± 0.7 L CH4 / L) compared to control reactor (4.6 ± 0.7 L CH4 / L). In contrast, the specific methane production (SMP) showed no significant difference between the test reactor (295 ± 35) compared to control reactor (306 ±37), indicating similar efficiency of biodegradability between the test reactor and control.