Production of a Biopolymer By Using Hydrolyzate of Rice Stover and Its Application in Sludge Dewatering
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The aim of this study was to harvest a biopolymer from acid hydrolyzed rice stover with phosphate salts as pH buffer, and to enhance sludge dewatering by using this biopolymer combined with chemicals.
Rhodococcus erythropolis was first inoculated in 250 mL seed medium and incubated on a reciprocal shaker at 150 r min−1 and 35 °C for 24 h, and then, 2.0% (V/V) of the above inoculum was used to inoculate the cultivation medium and incubated in the same procedure to produce biopolymer. For sludge dewatering, the biopolymer was added into a 200 mL mixing chamber with 100 mL of sludge, and then the mixtures were stirred at the design agitation speed for 10 min, finally, dry solids (DS) and specific resistance to filtration (SRF) of the sludge were examined.
Rhodococcus erythropolis obtained its maximum biomass (OD600) of 0.79 when 5 g L−1 K2HPO4 and 2 g L−1 KH2PO4 were presented in cultivation medium. The fermented broth from the medium with phosphate salts appeared high flocculating activity of 94.6%, higher than that from the phosphate-free medium. Meanwhile, the biopolymer performed a great potential in sludge dewatering, after treated by this biopolymer, DS and SRF of the sludge reached 18.4% and 4.8 × 1012 m kg−1, respectively. Sludge dewatering was further enhanced when the biopolymer and polyaluminum chloride (PAC) were used simultaneously, under the optimal sludge treatment conditions of biopolymer of 13.5 g kg−1, PAC of 19.4 g kg−1, and pH of 8.1, sludge SRF decreased by 73.5% and DS increased to 24.1%, respectively.
It is meaningful to enhance the dewatering of the sludge by the composite use of the biopolymer and PAC.
KeywordsBiopolymer Rice stover Polyaluminum chloride (PAC) Sludge dewatering Response surface methodology (RSM)
Authors would like to acknowledge the finding support for this study by the National Natural Science Foundation of China (Grant Nos. 51508043, 51608061) and Basic Project of Science and Technology Department of Sichuan Provincial (2016JY0015, 2015JY0113).
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