Deep Dewatering Process Of Taihu Cyanobacteria Sludge

With the intensification of eutrophication in Lake Taihu,Cyanobacteria blooms periodically erupt,which could not be effectively controlled in a short period of time.At present,the most effective mitigation measure for Cyanobacteria blooms is salvage.A large amount of Cyanobacteria sludge would be produced after the preliminary separation of Cyanobacteria and water,which could cause secondary pollution to the environment if it was not handled in time.The government cooperated with thermal power companies to carry out deep dewatering of Cyanobacteria sludge and incinerate the dehydrated Cyanobacteria sludge,which could ultimately realize the reduction and harmlessness of Cyanobacteria sludge.However,it was found that the dewatering performance of Cyanobacteria sludge fluctuated greatly in the actual production process.The dewatering performance of Cyanobacteria sludge from different sources and at different times were quite different,which could make the workshop unable to achieve efficient dewatering of Cyanobacteria sludge by using the previous experience of municipal sludge dewatering.Due to the lack of scientific guidance method,regardless of the difference of dewatering performance of raw materials,a large amount of calcium oxide was added for dewatering,resulting in the waste of chemicals and low dewatering efficiency.The large number of inorganic matter could also reduce the effect of Cyanobacteria sludge cake incineration treatment.In view of existing problems,this paper first investigated the microbial communities in different time and space of Lake Taihu,analyzed the distribution characteristics of the microbial communities,which were related to the dewatering properties,so as to find out the reasons for the fluctuation of the dewatering properties of Cyanobacteria sludge.Then,based on the in-depth study of the dewatering status of the production workshop,a rapid evaluation method for the dewatering performance of Cyanobacteria sludge was established.The main contents and conclusions are as follows:（1）The microbial communities in different time and space in Lake Taihu were investigated,and the correlation between environmental factors and microbial communities was found by using statistical analysis tools,and the dewatering performance evaluation index was associated with the diversity of microbial community structure,so as to find the influencing factors leading to the fluctuation of Cyanobacterial sludge dewatering properties.The results show that:within the sampling range of this experiment,Cyanobacteria and Proteobacteria occupied the main abundance in the bacterial communities at all sampling points,Microcystis as the only detected genus of Cyanobacteria,may be one of the main factors leading to the difficulty of Cyanobacteria sludge dewatering.Compared with the bacterial community,the eukaryotic microbial community had lower diversity,mainly composed of unclassified eukaryotic microorganism,Chlorophyta and Rotifera.As a representative index of seasonal variation,temperature was the most important factor affecting the microbial community structure in Lake Taihu.The filter cake specific resistance was correlated with the bacterial community diversity index Chao value,but it was no significant correlation with the eukaryotic microbial community diversity,indicating that the bacterial community diversity in Taihu Lake affected the dewatering performance of Cyanobacteria sludge.（2）The production process was visualized by the calculation method of filter cake specific resistance in the production workshop,which was established by analyzing the samples in the deep dewatering workshop of Cyanobacteria sludge.There was a linear relationship between the filter cake specific resistance of laboratory and that of workshop.The specific resistance of filter cake in the workshop was 1.55 times of that in the experiment.Then,through the analysis of the influence of the proportion of municipal sludge in the current production process,it was found that the influence of municipal sludge content on the specific resistance of filter cake was linear,while the relationship between Cyanobacteria sludge content and the specific resistance of filter cake was 2.21 power,indicating that the proportion of Cyanobacteria sludge in the mixed sludge had a more significant influence on the specific resistance of filter cake.The relationship between calcium oxide dosage and filter cake specific resistance was-1.04 power,and the relationship between ferric chloride dosage and filter cake specific resistance was only-0.0371 power,which indicated that calcium oxide dosage had a greater impact on filter cake specific resistance of mixed Cyanobacteria sludge.According to the above information,the rapid evaluation equation G=0.342（SRF_d/SRF_p）^?0.962×F^?（-0.0357）was established to guide the production scientifically and efficiently.（3）The flocculation-hot press filtration process was used to optimize the mechanical dewatering of Cyanobacteria sludge,and the pilot scale production was carried out,which provided a new scheme for the improvement of the deep dewatering process of Cyanobacteria sludge.When 10%ferric chloride was added in the laboratory,the effect was the best in the experimental range,and the specific resistance of filter cake was reduced by 92.85%compared with the process without adding ferric chloride.Under the pilot test conditions,the moisture content of the Cyanobacteria sludge cake was about 65%when added 15%ferric chloride.The actual Cyanobacteria sludge volume reduction rate reached61%.Compared with 46%of the actual capacity reduction rate of Cyanobacteria sludge in the current production conditions,the efficiency of Cyanobacteria sludge treatment was effectively improved and the reduction of Cyanobacteria sludge treatment could be realized.Moreover,the obtained Cyanobacteria sludge cake has high VS/TS,which was conducive to the resource utilization of the later stage.