Bioflocculants Produced by Gram-positive Bacillus xn12 and Streptomyces xn17 for Swine Wastewater Application

Strains xn12 and xn17 were isolated from activated sludge from a local hoggery, and preliminarily identified as Gram-positive Bacillus and Streptomyces, respectively. Their flocculating activities were mainly in the extracellular materials, and their components were mainly non-ketose polysaccharides, not proteins. Their flocculating efficiencies were over 95 % under the optimal conditions for production of xn12 and xn17 as follows: initial pH 5; inoculum volume 0.5 mL, 1.0 mL, respectively; cultivating temperature 30 °C; and cultivation time 4.5 days and 1.5 days, respectively. Each of the xn12 and xn17 had strong thermal stability under 30–80 °C. The optimal removal efficiency of turbidity for xn12 and xn17 in swine wastewater was 82 %, 87 %, respectively, their turbidity removal efficiencies were better than polyaluminium chloride alone, and that of COD was 42 %, 46 %, respectively.