Field Study Of Microbial Contamination In Central Air Conditioning Cooling Systems

Cooling water has been widely used in central air conditioning systems,and the cooling water quality is associated with the cooling performance,also some pathogens which can do harm to the human.The cooling water quality receives more attentions for the policy of Energy-saving and Emission Reduction and the increasing awareness of the pathogen associated with the cooling water.The planktonic microorganisms examinated in the cooling water included the total bacteria(TBC),iron bacteria and sulfate reducing bacteria,with the concentration of 2.0×10~2 CFU/ml-4.7×1O~3 CFU/ml,0.47 piece/ml and 0.4 piece/ml,and the detection rate were 100%,83.33%and 16.67%,respectively.The microbial contamination were less than the code of the cooling water in China.The concentration of the TBC varied to the buildings,and is higher in the shopping malls.The amount of sessile microorganisms was low,and increased with the time before come to a steady situation in a month.The concentration of sessile TBC and iron bacteria were 10~4 CFU/cm~2,and 10piece/cm~2,respectively.The bacteria associated with the cooling water were of many different species with different colonies characteristics.The rod-shaped bacteria account for the large part of the samples.There's some difference between the plantonic TBC and sessile TBC,for the plantonic TBC colonies formed in 3-4 days and were mainly yellow,red,off-white and white,while the sessile TBC grew faster and were mainly off-white and white.The air-conditioning recirculating cooling water systems investigated were under a relatively low management.Phycial chean/washing was employed to clean the cooling tower pool and the cooling pipes in all the systems.Two systems used biocides to control micro-organisms,and five systems employed the electronic water treatment instruments to prevent scaling.Legionella wasn't under a scientific basic prevention and got adequate control.Managers had a weak awareness of the microorganisms cooling water system,and there's no scientific method for maintenance.