Factors affecting microbial dynamic in drinking waters systems and alternative approach for hot water systems disinfection
Type of activity
Microbial load and dissolved organic carbon not contributes to increase microbial levels on surfaces. In a second paper was exanimated the effect of different episodes of deficient chlorine depletion in the biofilm growth and the subsequent impact in microbiaL load in water. In this second work was demonstrated that successive episodes of chlorine depletion increase the microbial resistance to disinfection, and this major resistance is related with the increase of microbial load in water column....
Microbial load and dissolved organic carbon not contributes to increase microbial levels on surfaces. In a second paper was exanimated the effect of different episodes of deficient chlorine depletion in the biofilm growth and the subsequent impact in microbiaL load in water. In this second work was demonstrated that successive episodes of chlorine depletion increase the microbial resistance to disinfection, and this major resistance is related with the increase of microbial load in water column. As rule of thumb, the first two papers demonstrated that chorine depletion in water supply is key in microbial proliferation trough the system. In developed countries, common managing practices ensures that in most cases, when necessary chlorine levels can be maintained in appropriate levels from the production point up to end customer. However practical experience, showed that despite of the implementation of good managing practices, often during short time periods ( hours or days ) free chlorine levels could become low. These episodes not directly impact over microbiological or chemical water quality, at least under a legal point of view.
On the other hand, in private systems, the quality of water can change easily as consequence of differential flow, high residence times and structural deficiencies. Also, in theses cases the poor chlorine level or absence of disinfectant can lead to quality problems. Additionally in hot water distributions systems, water recirculation and high temperatures involves the impossibility to maintain appropriate chlorine levels trough all the pipeline.
Past and current concerts about microbiological quality of water mainly have been focused on control faecal pollution, since it could be directly related with acute diseases. By the means of monitoring the levels of some microorganisms as E.coli the fecal pollution could be well monitored. The absence of E.coli in 100 mL has been used as indicator of good quality. In order to complete this approach also have been used complementary indicators as Intestinal Enterococci and Clostridium pefringens. The faecal pollution control is accompanied by a microbiological process control focused on monitoring levels of total coliforms and controlling changes of heterotrophic plate counts (fixing in some cases a upper level of 100 ufc/mL). Both approaches have been very useful and key to supply safe potable water, nevertheless are based in a incomplete set of premises: Pathogens are form Faecal source. Pathogens could entry into the network but showing a low survival rate. The normal ecosystems not includes pathogens or at least microorganism that need to be monitored, because their presence could be related with conventional faecal pollution indicators.
During the last two decades our understanding about microbial dynamics of
drinking water has been improved, now not is under discussion the biofilms role
as pathogen reservoir and in most cases these pathogens not are from a faecal
source i.e Legionellae, Mycobacterium, Para-Chlamydia and other emerging
pathogens. Also is important to remark that the amoeba's role, in the water
network. In the last years increased the evidences that show their active
responsibility of pathogens survival, also for species from faecal source.
In all these scenarios previously descried, alternative disinfection approaches
are need. Not only for distribute safe water, also for control biofilm growth at
least for these cases of direct health risk ( i.e Legionellae presence in a