Effect of bio-surfactant on municipal solid waste composting process.
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Bio-surfactant is a new type of surfactant that is produced in microbial metabolism. Adding bio-surfactant during composting process, especially to those contain some toxic substances, has been proved to be a promising way. In this study, Strains III (2), a bacterial with high activity to produce bio-surfactant, were isolated firstly. Following comparison experiments with and without adding Strains III (2), namely Run 1 and Run R, were conducted, respectively. The experimental results showed that, by adding Strains III (2), the surface tension could reduce from 46.5 mN/m to 39.8 mN/m and the corresponding time to maintain the surface tension under 50 mN/ m could prolong from 60 h to 90 h. The oxygen uptake rate and total accumulated oxygen consumption with Stains III (2) were both higher than those without Strains III (2), while the accumulation of H2S in outlet gas was reduced to around 50% of Run R. Moreover, two additional experiments were also carried out to examine the effects of strains coming from different systems. One is adding Strains III (2) with a dose of 0.4% (Run 2), and the other is seedling commercial Strains at the same conditions, the composting experiments showed that: Run 2 was more effective than Run 3, because the commercial Strains can be suppressed significantly in a complex composting system with different pH, high temperature and some of metals. The bio-surfactant was also added into the solid waste, which contained some toxic substances, the corresponding results showed that the remove rate of Hg and sodium pentachlorophenolate (PCP-Na) could be improved highly. Thus, the microenvironment, reactionrate and composting quality could be enhanced effectively by adding bio-surfactant to the composting process.
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