coliform bacteria, iron related bacteria, sulfate reducing bacteria, slime forming bacteria, microbiologically influenced corrosion, chlorine, biofilm


Alternative Technology for Cooling Towers:
 electrolytically generated silver and copper ions

Universidad Nacional Autónoma de Mexico
Instituto de Investigaciones Eléctricas

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A novel alternative with great potential of use is proposed to replace chlorine with another biocide in cooling systems. This alternative has a minimum environmental impact and allows the establishment of a microbiological control of cooling systems by decreasing the bacteria population commonly present in cooling water. The proposed alternative to be used as biocide is the electrolytically generated silver and copper ions. The effect of chlorine and its combination with these ions on decreasing the aggressivenees and discouraging bacterial population growth was also studied. The concentration relation of 1.2 mg L-1 silver/0.6 mg L-1 copper and 0.3 mg L-1 of chlorine combined with 0.2 mg L-1 silver/1.2 mg L-1 copper are a good alternative to replace or decrease significantly chlorine consumption in cooling systems. In this way, a minimum environmental impact will be produced with relatively low concentrations of silver and copper ions. These concentration relation showed that iron related bacteria and sulfate reducing bacteria can be killed establishing a very effective treatment with 99 % control. Chlorine at concentrations of 1.0 mg L-1 and 3.0 mg L-1 killed some of these bacteria proving to be more effective for iron related bacteria compared with conventional cooling water treatments. These systems were able to lower the bacterial population that promote the microbiologically influenced corrosion and biofilm formation to levels of 1000 ufc/ml. Coliform bacteria were also reduced below the accepted levels (1000 NMP/100 ml) under the Official Norm.


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