Cooling Water Treatment

ENVIRODOS® 400 Series

Why cooling water treatment ?

 Why cooling water treatment ?

Reducing the impact on the environment from evaporative cooling water system operation should be a goal for every system owner/operator. However, as water treatment chemistry is a specialized field dealing in often proprietary technology, there is little reliable information with wich the owner/operator can evaluate the various means to safely reduce the envíronmental impact from operation of their cooling water system. The following information on reducing the environmental impact from operation of evaporative cooling water systems is based upon work in both environmental and water treatment fields since 2008. Basic technology is discussed along with a new technology developed specifically to reduce environmental impact and comments are provided on several misconceptions concerning water treatment chemistry, environmental impact, and the use of ENVIRODOS® water treatment products as green technology.

Blowdown - Intentional water loss from cooling systems

Evaporative cooling water systems reject 75 to 80% of their heat load by evaporation of water. As the water evaporates, removing heat from the system, the dissolved solids present in makeup water, added to replace the evaporated water, become more concentrated, at some point exceeding the solubility limit(s) of the material present (usually calcium carbonate) wich results in precipitation and formation of undesirable scale. Blowdown is water intentionally drained from the system to restrict the buildup of dissolved solids to levels below the precipitation point. Cycles is the term used to denote the concentration of dissolved solids in the system water as compared to the makeup water, thus two cycles indicate that the dissolved solids in the system water are twice the level in the makeup water.

Blowdown constitutes the major environmental impact from system operation as it is "wasted" water; water run to sewer that must be replaced with fresh water. For instance, a 1000 ton rated cooling tower running at 2 cycles will evaporate 100m³ with a blowdown of 100m³. If the cyles are increased to 4, the blowdown would be reduced to 50m³ .

Evaporation = 1000 litres/ton cooling           >            Blowdown = Evaporation/Cycles - 1

Since increasing the cycles generally results in solubility limits beeing exceeded, acid or a scale inhibitor must be added to the water to prevent scale formation. In practice, acid is not recommended due to helath/safety and controll issues, while use of scale inhibitng products generally limits the system to a maximum of 6 cycles, in the absence of a bypass filtration. Using 1000 ton system example, operating at six cycles would reduce the blowdown to just 20m³ . Operation at more than 6 cycles can seldom be justified on either environmental or cost reasons, and normally presents severe technical challenges.

ENVIRODOS® 401 chemical scale inhibitor use

A common misconception is that it is "bad" for the environment to be adding "chemicals" to cooling water. Fortunately, this is incorrect as the truth of the matter is that the effective, ENVIRODOS® used scale inhibitor compounds have no toxics and are completely biodegraded when discharged into the environment. Thus use of scale inhibitor products in cooling towers does not adversely impact  the environment. In fact, when used to increase cycles, scale inhibitor chemicals use reduces the environmental impact of system operation by lowering the amount of fresh water used and blowdown discharged.

A second environmental benefit, often very substantial, is that by keeping the heat exchange surfaces in the system free of scale. energy use, and resultant environmental polluction from energy production, is reduced. For instance, a scale thickness of just 0.2 cm (0,08 inches) can increase energy usage in a chiller condenser by as much as 12%, a waste that can be totally prevented by proper use of scale inhibitor chemicals.