The Dirty Little Secrets of Recycled Water
We all know that California has a lot of competing interests when it comes to water consumption. And recycling of almost anything (as opposed to cleanliness) is right up there next to Godliness, particularly in the Golden State. So how could it possibly be bad when municipal governments mandate the usage of recycled water in water cooled HVAC systems? To answer that question, it is necessary to understand some basics of water treatment. Water treatment has historically focused on a couple of things in its effort to protect equipment and systems: inhibiting the formation of scale; inhibiting corrosion; inhibiting organic growth; and not wasting water. The priorities have often flowed in the order just mentioned. Unfortunately, recycled water flips those priorities on their head. Saving water becomes paramount. And organic growth is often not a big problem, because recycled water tends to be highly chlorinated. But the same chlorine that helps with organic growth tends to accelerate corrosion. And as for scale…recycled water is the home of concentrated phosphates. Our society uses phosphate-heavy detergents for many things, and removal of phosphates is both difficult and expensive for our sewage treatment plants. Consequently, it is likely that recycled water in SoCal will contain a lot of phosphates. The presence of phosphates creates a serious risk to evaporative cooling equipment, and the “ripple effect” of decisions made to protect that equipment spreads in a lot of directions. When anticipating a project that will utilize recycled water, there are a lot of things to keep in mind.
If you would like to know more, this link will take you to the relevant SoCal ASHRAE chapter newsletter article: http://ashrae-socal.org/pdf/SolAir_October_Final.pdf