Integrated thermophilic submerged aerobic membrane bioreactor and electrochemical oxidation for pulp and paper effluent treatment--towards system closure.
ABSTRACT A novel integrated thermophilic submerged aerobic membrane bioreactor (TSAMBR) and electrochemical oxidation (EO) technology was developed for thermomechanical pulping pressate treatment with the aim of system closure. The TSAMBR was able to achieve a chemical oxygen demand (COD) removal efficiency of 88.6 ± 1.9-92.3 ± 0.7% under the organic loading rate of 2.76 ± 0.13-3.98 ± 0.23 kg COD/(m(3) d). An optimal hydraulic retention time (HRT) of 1.1 ± 0.1d was identified for COD removal. Cake formation was identified as the dominant mechanism of membrane fouling. The EO of the TSAMBR permeate was performed using a Ti/SnO(2)-Sb(2)O(5)-IrO(2) electrode. After 6-h EO, a complete decolourization was achieved and the COD removal efficiency was increased to 96.2 ± 1.2-98.2 ± 0.3%. The high-quality effluent produced by the TSAMBR-EO system can be reused as process water for system closure in pulp and paper mill.
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ABSTRACT: A comparative study on the treatment of thermomechanical pulping (TMP) pressate was conducted under thermophilic (55 degrees C) and mesophilic (30 degrees C) temperatures to explore in-mill biological treatment, with the intention to operate under heat-efficient conditions. The experimental study involved sequencing batch reactors (SBRs) operated over 114 days. Receiving a total influent chemical oxygen demand (COD) of 3700-4100 mg L(-1), the COD removal efficiencies of 80-90% and 75-85% were achieved for the mesophilic and thermophilic SBRs, respectively, at a hydraulic retention time (HRT) of 12 and 24h. Excellent sludge settleability (sludge volume index < 100 mL g(-1) mixed liquor suspended solids) was obtained at both thermophilic and mesophilic SBRs. A higher level of effluent suspended solids was observed under thermophilic conditions. The results support the feasibility of applying thermophilic biological treatment of TMP pressate. The treated effluent has the potential for subsequent reuse as process water after polishing, thus addressing the long-standing desire to develop water system closure for the pulp and paper mill operation.Environmental Technology 01/2014; 35(9-12):1409-17. · 1.61 Impact Factor
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ABSTRACT: Effects of wastewater and mixed liquor characteristics on membrane fouling in both a submerged anaerobic membrane bioreactor and a thermophilic submerged aerobic membrane bioreactor were studied with four types of industrial wastewaters. Significant differences in particle size distribution, colloidal content, the protein to polysaccharide ratio, and soluble compounds molecular weight distribution were observed among the four types of wastewaters and mixed liquors. Differences in wastewater and mixed liquor characteristics were correlated to the changes in membrane filtration behavior in both systems. The colloidal content in feed and mixed liquor plays a dominant role and is more important than the quantity of total suspended solids in controlling membrane fouling. The ratio of proteins to polysaccharides is more important than the total quantity of soluble organic substances in controlling membrane fouling. A full characterization of feed and mixed liquor may be used as a tool to predict membrane performance.Bioresource Technology 10/2012; 128C:207-214. · 4.75 Impact Factor