Isolation And Identification Of Thermophilic Strains And Their Bio-drying Characteristics

Excessive water content in untreated urban sewage treatment plant dewatered sludge can take up large space, causing bacteria to multiply, producing poisonous gas and leachate which threat the air and groundwater environment severely. So the bio-drying technology of urban sewage treatment plant dewatered sludge is very important. Conventional bio-drying technology has a long cycle and slower startup time. Isolating and screening predominant thermophilic microorganisms has an important significance for enhanced bio-drying technology of urban sewage treatment plant sludge.In this paper, six thermophilic predominant bacterias X13?FX3?DF4?DB4?Y10?XW5 were isolated and screened from urban sewage treatment plant dewatered sludge. After morphological, physiological and biochemical tests, the thermophilic bacteria X13 were identified Pseudomonas sp., the FX3 were identified thermophilic Actinomycete sp., the thermophilic lipid decomposition microbes were identified Thermoleophilum sp., the thermophilic microbes DF4?DB4?XW5 were identified Paenibacillus sp..By inoculating the thermophilic microbes to the mixed sludge, We found that the predominant thermophilic microbes X13?FX3?DF4?DB4?XW5?Y10 have obvious promotion to bio-drying. At the second day of the bio-drying, the water removal rate was apparently higher than the blank test. After 5 days bio-drying, the water removal rate, VS removal rate and TN removal rate of inoculated microbes tests were higher than the blank test. Inoculating thermophilic microbes raise the drying products'biological stability.Though the pairwise bacteria combination tests, it was found that the thermophilic microbes X13?DF4?DB4?XW5?Y10 were selected as the thermophilic predominant bacteria. By using twenty uniform experimental designs, though five days analog bio-drying test, the results showed that all the experiments promoted the effect of bio-drying. The optimal proportion of X13:DF4:DB4:Y10:XW5 is 0.10:0.11:0.14:0.21:0.44 which was used as the thermophilic predominant multiple species inoculant. The water removal rate of this proportion is 13.38%.Finally, dewatered sludge of a wastewater treatment plant in Shenyang was chosen as raw material, and straw as amendment. The bio-drying test was conducted for 5 days under an intermittent mandatory ventilation condition, with a certain addition of thermophilic predominant bacteria screened before. The study showed that the thermophilic predominant bacteria could rise the highest temperature of bio-drying to 63 ? and prolong high-temperature period. At the third day of bio-drying, the water content achieved temperature below 60%. The VS removal rate of sludge was 13.19% so that raise the drying products'biological stability. Inoculating the thermophilic microbes has not negative effects on the pH value of sludge. Over the bio-drying cycle, the pH value could remain at 6-8, the drying products meet the soil landfill criterion and suitable for microorganisms growth. The thermophilic microbes which consumed more nitrogen showed more activity in the initial stage of bio-drying. Though five days bio-drying, the total nitrogen of drying products was reduced to 3.17% which maintained scope of farmland. Bio-drying can rise the heavy mental stabilization of drying products. Inoculating the thermophilic microbes could reduce the biological toxicity of drying products and passivate heavy mental.