Methane production potential and anaerobic treatability of wastewater and sludge from medium density fibreboard manufacturing

This research evaluates the suitability of anaerobic digestion of different waste streams derived from Medium Density Fibreboard (MDF) manufacturing. Methane production potential and anaerobic treatability were firstly assessed in batch assays for raw wastewater, physical-chemical pre-treated wastewater, as well as for sludge generated by current wastewater treatment at an industrial facility. Singlefeeding and multi-feeding (semi-continuous feeding) experiments were conducted to quantify methane production and methanogenic toxicity. Digestion of the raw wastewater produced 4.0 L CH4/L, which required dilution of the wastewater to 30-40% because severe toxicity was observed at 40% raw wastewater. Digestion of current process sludge produced 21.4 mL CH4/g raw sludge, but it also required dilution to avoid toxicity. Working with these substrates, the necessary dilution led to a maximum concentration of soluble chemical oxygen demand (COD) of 4.2-4.6 g/L in the digestion medium, while the conversion of total COD to methane remained below 22%. Pre-treated wastewater in the current industrial process did not show inhibition, but gave a low methane production of only 0.8 L CH4/L. An alternative treatment scheme consisting of simple sedimentation of raw wastewater followed by preaeration showed enhanced methane production of 4-4.8 L CH4/L at higher concentrations of up to 80% wastewater in the assay medium. Sedimentation allowed increasing the soluble COD in the digestion medium up to 6.9 g/L, while the additional pre-aeration further increased the soluble COD to 12.9 g/L without inhibition of methane production. Conversion of total COD to methane during the exponential phase increased to 64%. Simple sedimentation also removed 82% of suspended solids, which would help prevent clogging and improve anaerobic treatability in continuous digesters. (C) 2020 Elsevier Ltd. All rights reserved.