WATER TREATMENT
Figure 2 - Problems caused by biofilm and common microorganisms
biofilm with measurement accuracy of approximately 10 μm and at a resolution of +/ - 5 μm . A side stream of cooling tower water is taken and run through the analyser . Ultrasonic pulses are fired at a heated target assembly and then reflected back to the ultrasonic sensor ( Figure 3 ). A reduction in travel time indicates the presence of biofilm . Heating the target assembly and duplicating the shear stress of the heat exchanger by controlling the water flow allows the analyser not only to measure biofilm thickness , but also to calculate the insulating effect of the biofilm and the actual loss of heat transfer efficiency expected in the modelled heat exchanger . The analyser differentiates between soft deposits ( organic and biological fouling ) and hard deposits
Figure 3 - Working principle of the ultrasonic sensor
( scaling ), and it automatically corrects for variations in temperature , conductivity and pressure to ensure accurate biofilm measurement .
Biofilm control & removal
Only a few microbiological control treatments can effectively penetrate and remove biofilms . Without them , biofilm removal often requires expensive and extensive manual cleaning . Strong oxidising biocides , such as sodium hypochlorite and chlorine , have been used for decades to control microbiological activity in industrial cooling water systems ; however , although they effectively control planktonic microorganisms , they are unable to penetrate and control established biofilms caused by sessile microorganisms .
The proprietary Biosperse chlorine stabiliser chemistry is used in combination with sodium hypochlorite to produce a patented , in situstabilised active chlorine system . The resulting solution effectively controls a broad spectrum of microorganisms , including bacteria , mould , yeast , algae and molluscs . Biofilms exhibit a wide variety of defence mechanisms against biocides . Therefore , compared with the control of planktonic microorganisms , effective microbiological control of biofilms may require up to 1,000-fold higher biocide concentration than typical . The in situ-stabilised active chlorine solution effectively controls both planktonic and sessile microorganisms . Furthermore , it shows extraordinary biofilm penetration and dispersal : at normal use concentrations , it works 170 times faster than bleach . Additionally , strong oxidising biocides are highly reactive with organic and inorganic materials , causing many unwanted side effects , including increased corrosion rates , increased precipitation of heavy metals , reduced equipment performance , increased maintenance costs , increased risk of chlorine off-gassing and increased levels of adsorbable organic halogens and trihalomethanes . Because of its chemical structure , the in situ-stabilised active chlorine system produced with the chlorine stabiliser chemistry does not cause
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