Experiment And Research On Microbial Treatment Of Circulated Cooling Water In Thermal Power Plant

The circulated cooling water system of inland thermal power plants in China is mainly intercooled open-type system.Due to the open environment and continuous evaporation of cooling water,scaling,corrosion and breeding of harmful bacteria and algae are inevitable.The traditional method is to add scale inhibitor,corrosion inhibitor,biocide,slime stripping agent or other chemical agents to the cooling water to solve these problems.This method has a quick effect,but it also brings side effects and secondary pollution.In addition,the national laws and regulations are getting increasingly strict with the improvement of people’s ecological consciousness,and some traditional treatments can no longer meet the new environmental protection laws and regulations.In this paper,the principle of a microbial agent that used in recirculated cooling water is introduced,and its application effects in the actual treatment of recirculated cooling water is discussed.The primary conclusions are as follows:（1）For the open-type recirculated cooling water system with surface water as water source,the cooling water generally does not contain toxic substances,and the COD content is high.The temperature,p H,dissolved oxygen and other conditions are also suitable for the reproduction of microorganisms,thus have the potential to use microbial methods for treatment.（2）Microbial agent has the effects of descaling,corrosion inhibition and sterilization,and can guarantee the stable operation of the recirculated cooling water system.Compared with the treatment with chemical agents in the same period in history,the terminal difference of the condenser and heat resistance of the heat exchange pipe during the microbial agents treatment were reduced,the condenser showed no evidence of scaling;The average concentration of total iron of cooling water was 0.73mg·L^-1,and that of copper was 27.30μg·L^-1,both were better than the national standard requirements,the system showed no signs of corrosion acceleration;The average total number of heterotrophic bacteria in cooling water was 9.3×10⁴CFU·m L^-1,and that of biological slime was 1.43m L·m^-3,both within the scope of the national standard requirements,the system did not have signs of harmful bacteria or algae bloom.（3）Microbial agent has the function of degrading organic matter,flocculating suspended matter and reducing phosphorus,which can improve the quality of recirculated cooling water and ensure the discharge of sewage in the system reach the standard.During the treatment with microbial agent,the average TP,COD and turbidity of the cooling water were 0.37mg L^-1,38.56mg L^-1and 11.45NTU,all lower than the historical level in the same period.（4）The application of microbial agent has certain requirements for the quality of supplementary water.For the system with surface water as the water source,the turbidity of supplementary water is required to be lower than 12NTU.