Cooling Tower Blowdown Water

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Comparison of electrolytic oxidation v. ozone as biocide and reducing rate of TDS build-up in Cooling Tower Blow Down Water. Performed by Pureflow PtY Ltd of Singapore at Singapore Polytechnic Institute.

Open evaporative cooling systems have been widely used throughout industry to remove heat from process systems and modern buildings for the purpose of air conditioning. As a result, due to this the system design, the open type of evaporative cooling systems is subjected to potential biofouling problems due to the presence of micro-organisms from the surrounding environment. They are also prone to corrosion due to the establishment of corrosion cells and to scale formation due to the increasing concentration of scale forming hardness salts as a result of the evaporation of “pure” water from the cooling circuit.

For cooling system to have optimum performance the above problems must be minimised with heat transfer surfaces maintained in a clean condition, corrosion controlled to maintain system integrity and control of microbial activity to prevent the build-up of biofilm and the proliferation of legionella bacterium.

The larger the number of cycles (COC) – the lower the volume of make-up water, decreasing operational costs and increasing freshwater water savings to the plant and the local community.

Comparison testing was performed by Purflow Pty Ltd. of Singapore in cooperation with Aquatic Technologies LLC of Oregon, USA using their patented EOH2O® electrolytic oxidation process at the school laboratory of Singapore Polytechnic to compare electrolytic oxidation v. ozone as the biocide and control of TDS scaling. Tests were performed with and without chemical inhibitors to estimate water and cost savings using traditional municipal water and “Newater” - which is particular to Singapore and is reclaim water from municipal wastewater plants that has undergone increased treatment and filtration as a viable alternative to municipal freshwater sources. Tests included a 30% and 50% side-stream treatment as well as a 100% constant treatment of the cooling tower water.

Results denote that electrolytic oxidation alone, outperformed chemical inhibitors and ozone plus inhibitors in all three regimes (30% sides stream, 50% side stream, and 100% of flow). Estimated make-up water savings by use of EOH2O® electrolytic oxidation process was 63% over chemical alone, and 35% over a combined chemical and ozone treatment regime.

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