WATER TREATMENT
any of these adverse side effects associated with using strong oxidising biocides .
Proof of performance
Solenis has applied the biofilm analyser and the chlorine stabiliser chemistry in many industrial cooling water systems across the world . Two case histories from the chemical processing industry provide examples of the application of these technologies and the improvements gained . The cooling water system of a speciality chemicals producer was treated with hydrogen peroxide and one of three organic biocides that were alternated . The programme required large volumes of hydrogen peroxide to keep the total bacterial counts and Legionella under control . During the summer , limits for bacterial counts and Legionella were exceeded frequently and biofilm build-up was observed throughout the cooling water system . The reduction in the cooling tower ’ s cooling capacity limited productivity . The customer faced increased costs , due to the high consumption of chemicals , and reduced productivity , due to the unreliable treatment . The biofilm analyser was installed to monitor biofilm build-up and the microbiological control treatment was switched to the chlorine stabiliser chemistry . Using a shock dose twice per day and with proper monitoring , the programme achieved stable and continuous performance resulting in consistently low bacteria counts and no Legionella . Existing biofilm was removed during the initial cleaning phase of approximately three months , resulting in improved thermal transfer and full cooling capacity . The data from the analyser confirmed that the surfaces were biofilm-free , and the analyser provided an early warning system in case of new biofilm formation .
Use of recycled wastewater
A speciality chemicals company in southern Europe operates a
Heated target assembly showing the presence of biofilm
recirculating cooling water system with four cooling towers , using as make-up mainly municipal water and , occasionally , wastewater from its own plant . The complex cooling system provides cooling water for diverse uses , but the main volume is used for chillers . The existing microbiological control treatment programme was intensive as it used high doses of a chlorine-bromine product and an additional organic biocide on a weekly basis . Because of contamination from the organic load in the wastewater , the microbiological control treatment was ineffective and expensive . The customer was obliged to perform off-line cleaning of the chillers every three months because of poor system performance . The biofilm analyser and the chlorine stabiliser chemistry were employed . Real-time measurements showed that the thickness of the biofilm rapidly decreased after the new microbiological control programme was implemented . The efficiency of the cooling system ’ s chillers improved significantly , and downtime for manual cleaning was reduced . Real-time monitoring using the analyser , combined with better microbiological control provided by the in situ-stabilised active chlorine solution , allowed the operators to use higher volumes of recycled wastewater , which generated savings of about € 25,000 / year .
Conclusion
Solenis ’ ClearPoint biofilm detection and control programme is a unique and comprehensive safeguard against microbiological activity and biofilm in industrial cooling water systems . Using the analyser to achieve the earliest detection and the most accurate biofilm measurement , combined with the proprietary chlorine stabiliser chemistry , to control both planktonic microorganisms and biofilm protects industrial cooling water systems against biofilm before cooling water systems are harmed or heat transfer efficiency is reduced . •
Christina Moering
CORPORATE INNOVATION MANAGER
14 SPECIALITY CHEMICALS MAGAZINE ESTABLISHED 1981