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| Methane production in anaerobic digestion of paper mill sludge by alkali/biological pretreatment |
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Abstract Methane production in anaerobic digestion (AD) of the paper mill sludge (PS) and monosodium glutamate waste liquor (MGWL) after PS was pretreated with alkaline (i.e., NaOH) and biological methods (i.e., mushroom compost and cellulase) was studied. Most of the macromolecules of PS were degraded into monomers (proteins and carbohydrates) which would be easier to be decomposed by microorganism to increase the methane yield in the stage of AD. The details of the change were shown as follows: after pretreatment, PS particles in structure became more compact; the porosity of particle reduced; the crude fiber was obviously degraded into small units; the increase of soluble chemical oxygen demand (SCOD) in PS from 35.5% to 1130% was noticed; volatile suspended solids (VSS) decreased slightly (6%~19%); sludge setting ration (SV) and NH3-N concentrations increased by 32%~192% and 36%~62.4%, respectively. Moreover, the changes of PS pretreated with alkaline were greater than those with biological methods. Additionally, the methane production in AD was 0.32m3 CH4/kg VS and 0.23 m3 CH4/kg VS after NaOH and biological pretreatment, respectively, which was enhanced by 54%~88% and 12%~34% compared with control. These two pretreatments showed promising results, and more research would be carried out.
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Received: 24 September 2009
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