Hyper-chlorination
As a part of regular maintenance, a pool is shocked periodically to remove organic compounds, remove chloramines and free up the available chlorine to allow it to sanitize the water. This also, however, binds up the free chlorine and keeps it from performing its sanitizing function if not used in proper amounts.
Adding ozone to the water
Ozone, as a secondary oxidizer, destroys ammonia, helping to prevent the formation of chloramines. As a disinfectant, this technique requires a large unit to disinfect by injecting the ozone into a side stream (about 10 per cent up to 25 per cent of the water) and then returns it into the full flow.
Drain and refill
This results in refilling millions of litres of fresh water, which is not only wasteful, but also presents the task of having to chemically rebalance it—not to mention the difficulty of disposing the contaminated water, which also contains unacceptable levels of chemicals, into sewer systems.
Regular dilution of water is another means of reducing the risk of RWIs. This is already practiced by public pool facilities in Europe where there are requirements for an entire pool being diluted with fresh water over a month’s time. Some other standards suggest adding 30 L (8 gal) of fresh water per day for every bather in the pool. This is obviously not viable in most areas of North America, especially those where regular droughts occur throughout the summer months.
In some areas, chemically laden pool water cannot be put to waste as it goes directly through the aquifers and could contaminate the groundwater. UV-treated water usually has drastically reduced sanitizer levels and, as a result, can safely be drained.
Enhanced filtration
One viable and more affordable method any aquatic facility can begin using immediately is enhanced filtration. The CDC and many aquatic experts have long considered filter enhancement with the use of specialty clarifiers as another preventative method. This technology uses two opposing biopolymers that quickly and effectively entrap micro-organisms such as Escherichia coli (E. coli) and Crypto.
This preventative method has been proven through an independent study conducted at Auburn University, which was presented at the World Aquatic Health Conference (WAHC) in 2005. The study showed very stable flocs of Crypto were able to form and be held in simulated sand filters. According to a presentation on “Cryptosporidium Removal from Swimming Pools by Sand Filters” by James Amburgey, PhD, an associate professor at the University of North Carolina at Charlotte, at the 2006 WAHC, there was a 99.99 per cent removal of Crypto from pool water using sand filtration treated with the two-stage polymer.
There is a great deal of complicated physics going on in a depth filter, such as the sand bed, as it traps particulates suspended in the incoming water. Other influences include surface charge, particle size, conformation, rigidity, density, and so on, on the nature of the path taken by the particles, and the frequency of their collisions and interactions with the filter medium. However, it is simple enough to understand the overall outcome: smaller particles tend to make it through the bed and come out in the effluent, whereas the larger particles stand a greater chance of becoming stuck and trapped along the route.
