Preparation Of Microbial Agents And Its Application In Municipal Sludge Aerobic Composting

Sludge is produced in the process of sewage treatment,with large amount and high moisture content of up to 80%.Sludge contains complicated substances,which include recyclable components like nitrogen,phosphorus and kalium,recalcitrant and toxic organics,heavy metals and pathogens and so on.Sludge recycling can not only decrease the secondary pollution risks,but provide sufficient fertilizers for city afforestation and landscape gardening.Based on the microbiology and molecular biology technologies,a strain of Streptomyces with fast proliferation rate and high-temperature resistance was isolated and purified from fungus chaff humus.Response surface methodology was employed to optimize the culture condition,and then under optimal culture conditions,fermentation broth was obtained and mixed with dehydrated sludge and corncobs?amendments?with different mass ratios for aerobic composting,in order to shorten the duration of sludge composting.?1?A strain with fast proliferation rate and high-temperature and adversity resistance was isolated and purified from fungus chaff humus,and it was identified as Streptomyces by Biolog test and 16S rDNA sequencing.?2?By single-factor test,effects of carbon sources,nitrogen sources,trace elements,culture temperature and fermentation time on Streptomyces propagation were studied.The optimal culture conditions were at temperature of 32^oC and incubation time of 24h.The formula of fermentation medium was as follows:10.5g/L sucrose,13.5 g/L peptone,13.5 g/L yeast powder,0.3g/L K₂HPO₄,0.3g/L KH₂PO₄ and 0.05g/L MgSO₄?H₂O.?3?Plackett-Burman?P-B?experiment was conducted to determine the significant factors in fermentation process of Streptomyces,and Box-Benken?B-B?experiment was designed to optimize the fermentation conditions.Results showed that optimal fermentation was achieved at sucrose concentration of 10.2g/L,temperature of 31.5^oC and culture time of 22h,and under these conditions,mycelium dry weight reached 1.9g/L.?4?Under optimal culture conditions,fermentation broth was obtained and inoculated to the mixture of sludge and straw at the mass ratio of 0‰?referred as CK for control??5‰?10‰and15‰.Results showed that compost maturity at the ratio of 5‰outperformed that of CK or at ratio of 10‰?15‰.This indicated that proper microbial inoculum amount could facilitate aerobic composting of sludge,however excessive inoculation amount could inhibit compost,hence optimal inoculation amount was 5‰.