| With a rapid increase in domestic garbage, auxiliary facilities and garbage innocenttreatment ability in some cities are insufficient, which caused garbage siege problem.The growth of the sewage sludge makes the disposal difficult, influencing the normaloperation of the sewage plant.. Due to the limit of economic development level and thelack of relevant technical capacity, the problem of garbage and sludge treatment in smalltowns is increasingly apparent. Therefore, it is imperative to develop a effectivetreatment technology which has a low operation cost and is easy to operate and maintain.On the major principle of energy conservation and recycling, self-heatingaerobic-anaerobic integrated reactor (SHAAI) was developed based on the previousbatch-scale research results. According to the ratio of output of municipal garbage insmall town to the yield of sludge in sewage plant, the volume of garbage tank andsludge tank were determined. And the centralized treatment (municipal garbage andsewage plant sludge) was not only carried out to make full use of waste heat used tosludge anaerobic digestion, but also have advantages such as investment saving, landuse, and easy management, achieving the regional balance of garbage and sludgetreatment. Aiming at the waste in Dadukou and the sewage sludge of sewage treatmentplant in Dadukou district, the reactor was examined by a systematic study. The resultswere showed as follows:①SHAAI was composed of waste tank and sludge tank. The effective volume ofwaste tank and sludge tank were5.28m3and0.9m3, respectively. The volume ratio ofouter sludge tank to inner sludge tank was1.48:1. The research of waste tank and sludgetank were conducted using aerobic composting and anaerobic digestion, respectively.②The start-up of SHAAI was studied by dealing with200kg of garbage every dayand with a dosing ratio of10%. During the SHAAI start-up stage, the tempreturechanges in the outer sludge tank and inner sludge tank was consistent with that in wastetank. And the tempreture were slightly different indicating that waste heat has asignificant effect on waste tank tempreture and a high heat transfer efficiency. DuringSHAAI start-up, it showed a very stable operation. The pH, alkalinity, Volatile fatty acid(VFA) and Soluble chemical oxygen demand (SCOD) were in the proper range whichwere suitable for microorganisms survival. Sludge thickening showed a goodperformance with a decreased volume (by68%) of disposal sludge to raw sludge. However, the removal rate of VSS was only13.2%.③The effectiveness of SHAAI in a pilot-scale with different dosing ratios of15%,20%and25%was investigated. Results showed that the temperature changes in thesludge tank was consistent with that of waste tank. The best efficiency was obtainedunder a dosing ratio of20%with a sludge tank average temperature35.2±2.5℃. Afterstart-up, SHAAI treatment process also presented a good stability. The pH in the outersludge tank and inner tank, alkalinity, VFA and SCOD were all in the proper rangesuitable for anaerobic bacteria survival. No acidification phenomenon was found.Sludge thickening showed good performance with a fact that moisture contentdecreased from98.4±0.6%in raw sludge to89.7±1.8%in disposal sludge. The sludgevolume was decreased by84.5%. A high VSS removal efficiency was found, and theVS/TS decreased from0.393±0.02in raw sludge to0.299±0.008in disposal sludge. Theaverage removal rate of VSS was24.0±3.6%. Daily gas production was110L/d. Thevolume of methane, CO2, N2and O2accounted for61.6%,24.2%,12.5%, and0.9%,respectively. As the anaerobic digestion process was conducted, the content of EPS,protein and polysaccharide gradually reduced. The polysaccharide and protein alsochanged during anaerobic digestion.④The results of sludge anaerobic digestion under the most appropriate dosing ratiowith three ractors, including the two-phase integrated sludge thickening and digestion(TISTD) reactor under the condition of the electric heating, the two-phase integratedsludge thickening and digestion productive (TISTDP) reactor under the normalatmospheric temperature, and the SHAAI reactor under spontaneous heating, werecompared. The results showed that TISTDP reactor had the smallest fluctuation oftemperature, best efficiency, stability and the highest content of methane. TISTD has thebest removal efficiency, while SHAAI reactor took second place and was very close toTISTD reactor. TISTDP reactor had the worst removal effectiveness.⑤The PCR amplification and denaturing gradient gel electrophoresis (DGGE) testof genomic DNA of the microorganism in the sludge tank under different dosing ratiowere investigated. It showed that clear bands and high brightness, and there were nonon-specific bands and primer dimers, which indicated good effects of amplificationand the high purity of products. All the DGGE profiles had many bands, whichindicated the species diversity and a variety of microorganisms can surive in the SHAAIreactor with strong anti-shock loading capability under the condition of waste composthesting. Shannon-wiener indexs and abundant species indexs showed the microorganisms diversity of the inside and outside of sludge tank. And the two indexsof outsides were higher than that insides under the same dosing ratio.⑥Specific band from1to27in DGGE profiles of sludge in the reactor underdifferent dosing ratios was gel extraction, amplification, cloning and sequencing,comparing with the sequences in GenBank. The results showed that microbialpopulation structure was in a long stable period in the stable operation of the reactor.But dominant population was difficult to change significantly. Dominant bacteria in thereactor were mostly Clostridium acidurici which was also dominant bacteria withhydrolysis acidification functions with a homology basically above95%.⑦Finally, the kinetics of organic matter removal in SHAAI was investigated.Vmax and Ks were identified based on Michaelis-Menten equation and experimentaldata under different dosing ratios. The results elucidated that vmax achieved themaximum of0.025d-1in the dosing ratio of20%, proving that the optimum dosingratio was20%. Waste tank temperature was linear correlation with that in sludge tankwith a correlation coefficient R2=0.825, indicating that waste tank temperature had asignificant effect on sludge tank temperature.⑧It was feasible that SHAAI may treat domestic garbage and sludge in sewagetreatment plant. The results provided theory and technical support for the design,operation and control of SHAAI, and have imporatant significance in promoting theintegrated treatment technology of sludge and waste in small towns. |
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