Biofouling is an issue for various industries including power, chemical, marine, and food processing. It can also cause problems in drinking water distribution systems. If left untreated the growth of biofilms can cause operational problems. This is can be a a significant problem for industrial and HVAC cooling systems.
Once bacterial cells adhere to a surface they undergo changes which create the biofilm. In some cases they capture inorganic matter as part of the overall matrix. With time the primary biofilm can favor the development of higher organisms leading to macro-fouling, a common problem described especially in marine systems. Biofilms cause significant energy losses by increasing surface roughness, thus pressure drop in the piping systems. With the incorporation of inorganic materials or the development of macro fouling, significnat heat trasnfer losses can also occur.
Biocides are often used to control the development of biofilms. In cooling water systems other chemical treatments are also applied to control corrosion and deposition of scale-forming salts. The addition of these chemicals has to be chosen carefully to avoid any loss in efficacy due to cross chemical reaction between the additives. The ideal biocide should kill a broad spectrum of micro organisms, relatively low toxicity to higher life forms, minimize corrosion of cooling systems materials, degrade quickly in the environment and not damage other treatment chemicals.
Chlorine has long been used as a biocide because it kills many micro organisms and has a low cost. Recently there has been concern about chlorine compounds and their by-products due concern about environmental and and human health problems issues. As a result of the issues surrounding chlorine, alternative biocides have be adopted. Ozone is one such biocide that has found application in preventing biofilms in cooling systems and other applications. Ozone is a broad spectrum biocide, decomposes rapidly in the environment and is compatible with other water treatment chemicals. Continuous dosing of 0.15-0.30 ppm is normally enough to maintain closed loop fresh water cooling systems free of biofilms.
There is less information regarding biocidal action of ozone on marine organisms. A recent article in Ozone Science and Engineering discusses the biocidal efficacy of ozone and chlorine against planktonic and biofilm cells of two marine bacteria. Biocidal Efficacy of Ozone and chlorine on Planktonic and Biofilm Cells of Two marine Bacteria Species, Sweta Swaraj, Rajesh Kumar, Y. V. Harinath & Toleti Subba Rao, pages 90-100, Volume 35, No. 2, 01 March 2013. The information is important for the use of either biocide in once through seawater cooling circuits. The study showed that both were effective in treating the subject organisms.