When a circulating cooling water system starts to foam, the rim of the collection basin is covered with foam, the fan blows it out of the tower, the suction well level is pulled down and the pumps run dry. On site people often pour a bucket of antifoam into the tower basin; the foam goes down for half a day and is back the next. Most foam in circulating water is not about the water itself: when cycles of concentration rise, inorganic salts and organic matter concentrate together, leakage from an upstream heat exchanger brings in ammonia nitrogen and oil, or biocide is dosed too much at once, and each of these takes its own handling route.
Whether the Foam Is Fine or Large and Easily Broken Tells You Where the Contamination Comes From
Large foam that breaks easily with an oily sheen on the basin surface mostly means heat exchanger leakage has brought in hydrocarbons and ammonia, with the water turning turbid and ammonia nitrogen and COD rising together. Fine, stable foam with white flocculent suspended matter means surface-active substances have entered the system, from cleaner residue or high organic matter in the make-up water. If basin make-up water suddenly increases and the blowdown valve is rarely opened, the cycles of concentration have exceeded the operating limit and the foam is a product of concentration. The same patch of foam can have different causes, so the same antifoam naturally works sometimes and not others.
Order of Handling: Check Water Balance First, Then Stop Leaks, Use Antifoam Last
First see whether make-up and blowdown match; if cycles of concentration are too high, increase blowdown to dilute the source. Then check upstream heat exchangers, starting with the ones where ammonia nitrogen and COD have risen. Then adjust how the biocide is dosed, changing a single shock dose into small frequent doses. If foam remains after these steps, that is when antifoam comes into play. Choose the dosing point in the turbulent section of the return main, not in a dead zone, start from a low ratio and confirm over one circulation cycle.
Selection Points: Look at Shear Resistance and Fouling Resistance Together
The shear from circulating water pumps and the spray fill is not light; an antifoam that breaks down quickly fails soon after dosing. When suspended matter and oil in the water increase, it is easily adsorbed and carried away, and grades with poor persistence need frequent top-ups, which costs more. Look at the acidity and alkalinity of the water: systems where the corrosion and scale inhibitor is alkaline are more stable with an alkali-resistant grade.
Chemitech's Solution
For circulating cooling water, reclaimed water reuse and industrial water treatment, Chemitech offers silicone, polyether, silicone-free and powder antifoams, covering open circulating water, closed systems and wastewater treatment sections.
By comparison, polyether types resist fouling better in high-salinity, high-turbidity water and are not easily adsorbed and carried away by suspended matter; silicone-free types suit downstream membrane treatment or silicone-sensitive processes without burdening subsequent steps; powder types are better for make-up dosing that requires dilution. The types differ considerably in persistence and applicable water quality.
When cycles of concentration are too high or oil keeps being carried in, increasing the dosage cannot sustain control; such problems have to be solved back at water balance and leak inspection. Exactly how to choose must be judged in light of the system conditions.
Report the circulating water volume, water quality indicators, cycles of concentration and main contaminants, and our technical team can judge the suitable type and arrange a sample test. Wastewater Treatment Antifoam Solutions and Industrial Cleaning Silicone-Free Antifoam Solutions are worth a look first.
Summary
When circulating water foam keeps coming back, it is mostly the system warning that something is wrong with water balance and leakage, not that there is not enough antifoam. Straighten out make-up and blowdown, plug the leaks, and the basis for foam thins out. When choosing, focus on shear resistance and fouling resistance, not just how fast it acts. Chemitech offers silicone, polyether, silicone-free and powder products in water treatment that can be matched to water quality. If you have a water quality report, our engineers can go through it with you.