Resource recovery from pulp and paper mills by adaptation of their wastewater treatment to biogas production
Granström, K.
(free)
Aerobic biological treatment of wastewater from pulp and paper mills produces a biosludge with a high C:N ratio. The sludge is suitable for biogas production. Current practices aims at reducing the sludge volume by prolonged aeration which uses excessive amounts of electricity. To optimize the aeration time, from an energy perspective, sludge with solid retention times of 2, 10 or 20 days were produced from wastewater and the quality of the resulting effluents and sludges was examined. Wastewater was taken from three sulphate pulp mills with long term activated sludge wastewater technology. The wastewater purification was similar for SRT10 and SRT20. Sludge settleability was either fine or intermediate except for one mills SRT2 that had poor settleability. The microbial population showed typical high-SRT organisms at SRT20. The largest amount of sludge was produced for SRT2 although the concentration of sludge was highest for SRT20. The methane potential for the sludges was 112-251 Nml/g VS as
averaged triplicate tests, 20 days at 55 C. One mill had significantly lower methane potential at SRT 20, for the others sludge methane potential was unaffected by SRT. Ten days solid retention time combines good wastewater purification with acceptable sludge quality and high biogas production.
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• Tackling Potential Odour Problems
• Operating Experiences and Potential Problems in Digester Operation
• Ensuring Optimum Energy Recovery from Biogas
• Liquor Treatment and P Removal
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