| Energy and environment problems restrict the sustainable development of economy and society.Using urban sewage heat transfer system is an effective way to save energy and reduce emissions.But serious fouling problem has not yet been resolved.Microbial fouling is an important part of fouling.Iron bacteria(IB)and sulfate-reducing bacteria(SRB)are main fungi that form microbial fouling.An experiment system studying the microbial fouling growth characteristics was designed in this paper.The cultured IB and SRB extracted from urban sewage secondary effluent were taken as the research object.By changing external factors such as temperature,flow rate and concentration,the growth characteristics of the IB fouling and the mixed bacterial fouling after adding SRB under different working conditions were studied.Two kinds of particles were selected for fluidization to remove the microbial fouling and the effects were compared.The experiment system studying the microbial fouling growth characteristics was designed in this paper.One section of pipeline of sewage heat transfer equipment was simulated and the weighing method was used to reflect the growth of fouling.The growth characteristics of microbial fouling were studied by experimental research.Firstly,the growth characteristics of IB fouling in different external conditions were studied experimentally.The results show that with the increase of temperature,the growth rate of IB fouling increased,the total amount increased,the water content increased.The smaller the flow rate is,the smaller the growth rate of IB fouling,the smaller the total amount is,the lower the water content is.The lower the initial concentration of IB is,the faster growth rate of fouling is,water content decreased first and then increased.Electron microscopy and energy spectrum analysis showed that the structure of IB fouling was loose and the gap was more,mainly composed of iron precipitate and organic matter.The SRB solution was added to the IB solution to form a mixed bacterial solution.The growth characteristics of mixed bacterial fouling were analyzed by changing the external conditions.The results show that when the ratio of IB to SRB was 1: 1,the growth rate of mixed fouling was the fastest and the total amount of fouling was the most.The higher the proportion of SRB,the lower the moisture content of mixed fouling.As for mixed bacterial solution with the concentration ratio of 1:1,changing the temperature conditions,it was found that at 30℃,the total amount of mixed fouling was the most.At 40℃,the growth rate of mixed fouling increased first and then decreased.At 20℃,the moisture content of fouling was the lowest.When the mixed bacterial solution with concentration ratio of 1:1,changing the flow rate and found that the growth rate of mixed fouling decreased with the increase of flow rate,the total amount decreased and the water content also decreased.By electron microscopy and energy spectrum analysis,it was found that the contrast of the mixed fouling was more dense,the voids were reduced,and the number of constituent elements of the soil was increased.Using fouling formed by the mixed bacteria,two different particles were added for fluidized fouling cleaning experiments.The results show that the fluidization rate of cation exchange resin particles is 0.45m/s,the descaling rate is 62%,the fluidization rate of sand is 0.85 m/s,and the descaling rate is 87%. |
