Antifouling Strategies and Environmental Issues in Industrial Cooling Water Systems in Marine Environment

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AbstractThe process of biofouling is ubiquitous to surfaces exposed in the marine environment. The problem is common to industries abstracting seawater for condenser cooling purpose like power plants, etc. Biofouling control and environment are two sides of a coin with respect to industrial cooling water system (CWS). Conventionally oxidizing biocides are the choice for biofouling control in CWS. Current regulatory norms for cooling water (CW) discharges in tropical marine environment stipulate a thermal threshold of ΔT of 7 °C from the ambient and a continuous biocidal discharge not exceeding 0.2 mg/L total residual oxidants (TRO) at the outfall. CWS, operating in tropical locations with high fouling pressure, have to tune their biocidal regimes to keep biofouling loads within threshold levels, such that it does not interfere with operations. Large CWS in tropical regions, with high fouling pressure, have to live with certain levels of biofouling, and the biocidal regime has to be tailor-made to treat a CWS depending on the level of cleanliness required, cost, type of organisms and seawater chemistry. Chlorine has been the cost-effective biocide of choice in most of the industrial CWS over the past few decades, due to its cost, availability, ease of handling and well-worked-out chemistry in seawater. However, their interactions with dissolved organics result in the formation of toxic halomethanes, which have been shown to persist and bioaccumulate in marine organisms. Biofouling is an interfacial or surface-associated phenomenon where treating the bulk cooling water with biocides results in requirement of huge biocide inventory and has effects on non-target organisms abstracted in CW. Surface protection in the form of AF coatings will greatly reduce the biocidal inventory and the environmental burden in the vicinity of industrial CW discharges. The two issues need to be handled in an integrated manner increasing industrial productivity as well as minimizing environmental damage.KeywordsChlorinationChlorine dioxideBiofouling controlAntifouling coatingsCooling water systemsLarval settlementBarnacles