Creative Water Solutions

Natural Water Treatment for Pools, Spas, and more

Anyone who owns, cares for, or cares about pools, spas or any kind of recreational water, knows that water filtration is an integral part of every water system. Using sand for filtration is commonly used on recreational and residential pools and large spas. Here are some of my observations, thoughts and concerns about sand filtration.

The Good

Sand is cheap, plentiful, and when it is a particle, it works well as a filter medium.

The Bad

Sand filters are usually filled, sealed and the sand is forgotten. The commonly held belief is that back washing the sand periodically, “fluffs it up” and returns the sand to a particle state where it can again work its magic as a particulate filter. Some sand filters have never been opened for 5-10 years to inspect the sand.
Back-washing the sand filter is costly. Water lost during back washing needs to be replaced, heated and treated. Ideally, the pool operators backwash often enough to keep the sand working as a filter, but do not needlessly back wash so water, heat, chemicals and time aren’t wasted.

The Ugly

Inspecting and analyzing the sand from pool sand filters in both residential and commercial pools has been enlightening, to say the least. At the bottom and sides of many filters we found sandstone. Actual sand in the process of forming sandstone. It wasn’t the gravel that is often put down underneath the sand, but sandstone. The sand in those filters was anywhere from 2-10 years old. The sand that wasn’t rock was sticky and foul. When we tested it in our laboratory, we found that it was full of organic contamination.

The Hypothesis

We know that in an aqueous environment that contains bacteria, organic contamination forms on every surface. To be effective, filters have enormous surface area whether they are made from sand, charcoal, paper, glass or diatomaceous earth. The particles become covered with organic contamination over time. Organic contamination is very sticky so the particles stick together. As time and pressure continue to pack the organic contamination-coated particles together they eventually become rock. So what happens during backwashing? The water will take the path of least resistance. We observed in these filters that there were channels in the sand. We think that the water follows channels through the sand that have become established over time.
We know that backwashing will not remove organic contamination. In fact there are very few things that will remove organic contamination. Strong acid or base solutions work but they destroy the filter, pumps, valves etc. We have demonstrated that a flush used in spas removes 90% of laboratory created organic contamination in one hour, and that many other solutions that claim to remove organic contamination don’t.

Getting Better Results

We also have observed that sand in filters where the water is treated with PoolNaturally® Plus (the commercial version of the residential product PoolNaturally®) appears to remain as particles. We think this is why we needed to backwash filters with PoolNaturally Plus much less often than those with conventional water treatment.
By understanding the relationship between organic contamination, filters and water we are aiming to create organic contamination free aquatic systems that require less chemicals, maintenance, and unwanted side effects.

During our test this last summer at the St. Paul, MN outdoor aquatic park we surveyed the swimmers twice a week. One of the most striking findings was that swimmers with asthma did not need to use their inhalers when swimming in the pools that were conditioned with PoolNaturally® Plus. We then treated the indoor aquatic park in St. Paul and had similar results.

Able to Swim AgainWatch movie online The Transporter Refueled (2015)

In fact one lady wrote to me about her inability to swim indoors due to her asthma. She was a competitive swimmer in her younger years and had to stop swimming because of severe breathing problems from asthma caused by the air in the pool. She heard about the sphagnum moss treated pools and how people could swim without using their inhalers so she tried swimming again. She reported that she could do a full workout without breathing problems and thanked me for “giving her back her favorite sport”.
With a little research the relationship between recreational and home water, chlorine and asthma became clear.

The Chemical Reactions

Here is what happens when we use chlorine to sanitize water in a pool or in our municipal water supply. As it turns out chlorine is not the problem. A byproduct of chlorine and biological molecules that contain nitrogen is the formation chloramines. These chloramines come in many different forms such as mono, di, and trichloramines. One of these compounds, a molecule called trinitrochlorine, has been implicated in causing airway irritation.
Trinitrochlorine is a volatile molecule that is extremely irritating to tissues such as your eyes, skin and airways. Because the molecule is volatile, it rises to the surface of water and is easily inhaled. In fact, in a pool, the levels of trichloronitrate are highest in the air right on top of the water. So every time a swimmer takes a breath, they inhale an irritant that causes airway constriction called reactive airway disease. The smell we all associate with a chlorine pool is actually the smell of the multiple species of chloamines, not chlorine. The problem is that chlorine is so reactive, it immediately finds and combines with nitrogen containing compounds to create chloramines.

Correlation between Pools and Asthma

A recent study reported in the pediatric literature, showed that children who are repeatedly exposed to swimming pools have a significantly higher incidence of reactive airway disease or asthma, than those who aren’t exposed to pools.
In our research laboratory, we are currently studying why the pools treated with PoolNaturally® Plus don’t cause this reactive airway response, skin irritation, or burning eyes and don’t smell. We know that for chlorine to become trichloronitrate you need chlorine, nitrogen containing biological molecules and a low pH. It could be that the amount of organic contamination in the pool correlates with the amount of trichloronitrate because organic contamination contains and produces huge amounts of nitrogen containing molecules and it creates a local microenvironment that has a very low pH. It could therefore be the “engine” that drives the formation of these toxic molecules. In the laboratory we know that the moss in PoolNaturally® Plus inhibits the formation of organic contamination and if our hypothesis is correct it could greatly reduce the formation of chlorine to trichloronitrate by removing the primary nitrogen source, the organic contamination.

Creative Water Solutions President and co-founder David Knighton, MD has been recognized by Aquatics International magazine as one of their Power 25 Reinventors. Successful testing of sphagnum moss-based PoolNaturally Plus at Highland Park Aquatic Center in St. Paul, MN, during the summer of 2009 marked CWS’ entrance into the commercial side of the aquatics industry.

This last summer we added our Sphagnum moss pool product to the Highland Park Aquatic Center in St. Paul. We treated two pools. One was a 430,000 gallon Olympic pool and the other was a 22,500 gallon children’s activity pool. You can read about the results on our website.
One lesson we learned involved cyanuric acid, outdoor pools, and chlorine. The accepted dogma is that cyanuric acid is required for outdoor pools and spas to stabilize the chlorine against UV degradation. In fact, most granular or solid chlorine sold in stores is stabilized with cyanuric acid. Dichlor and Trichlor have cyanuric acid in the formula.

When cyanuric acid interferes with chlorine

We started to try and understand the chemistry and science of cyanuric acid because of its side effects. Cyanuric acid above a certain concentration (which is dependent on pH) inhibits chlorine’s (hypochlorous acid to be precise) ability to oxidize bacteria. Failure to oxidize means no killing.
We also found that cyanuric acid is denser than water so it sinks to the bottom of a body of water. Therefore, the level of cyanuric acid on the surface of the pool or spa is the lowest level in the pool and it increases from there to the bottom. It will be the highest in the deepest part of the pool.
We tested this at the Olympic-sized pool. We sampled water at the bottom, middle and top of the pool. The cyanuric acid was set for 40 ppm. At the surface the level was 30-40 ppm, in the middle it was 60-70 ppm and at the bottom it was 100 ppm. From the middle of the pool to the bottom hypochlorous acid was essentially ineffective.
The other fact about cyanuric is that it is nonvolatile. That means as you add more and more to your pool or spa the concentration continues to increase. The only way to decrease the concentration is to empty some water and replace it with fresh water without cyanuric acid so you dilute out the chemical. In places where the spa or pool is full all year long, the concentration of cyanuric acid can increase to the point where the pool has no effective chlorine. I think this is why most pools have algae outbreaks starting in the bottom of the pool. The high cyanuric acid levels inhibit hypochlorous acid so no killing of algae occurs.

The experiment

So, after we learned this, I decided to decrease the cyanuric acid level in the pools gradually to see if it is really needed. The pool engineers told me “if you do that there will be no free chlorine in this pool in the morning.” We agreed to decrease cyanuric acid by 10 ppm each week and monitor the results. The free chlorine levels never decreased and the combined chlorine remained at 0. We decreased the cyanuric acid to zero and never added any more for the rest of the summer. The levels slowly decreased to zero as makeup water diluted out the cyanuric acid. The children’s activity pool behaved exactly the same.
In another pool we treated we were able to manage the large pool all summer without any cyanuric acid and maintained free chlorine levels from 1-3 ppm with no combined chlorine all summer.

Water treated with moss doesn’t need cyanuric acid

The bottom line is that with moss treated water, cyanuric acid is not needed. The mechanism for this probably centers around organic contamination. I don’t think that cyanuric acid prevents chlorine from UV degradation or the free chlorine levels would have decreased in the outdoor pools we treated. We know the moss inhibits organic contamination formation in the laboratory and know that organic contamination absorbs chlorine. We know that free chlorine levels skyrocket when moss is added to the pool and to maintain a level of 1-3 ppm free chlorine, the chlorine added to the pool decreases by over half. So a pool with moss doesn’t need cyanuric acid. That allows the chlorine added to the pool to remain active providing effective microbial control.

In my continuing travels to dealers, shows and meetings I am frequently asked, “Does the moss work in a salt water pool? “ Or “why do I need moss since my pool doesn’t need chlorine since it is a salt pool?” So this blog is about the science and chemistry of salt-water pools.
First, definitions: I’m going to talk about pools where the sanitizer is made from salt by a generator – not about the very few pools that actually have salt water similar to that in the ocean. Second, when I talk about green pool products I’m using the word to describe a product that is sustainable, with no artificially made chemicals, that doesn’t introduce toxic chemicals to the air, water or ground.

How does a salt water pool work?

Salt is usually sodium chloride or potassium chloride. When these chemicals are in water they become positively charged sodium or potassium and negatively charged chloride ions. In a salt pool, solid or crystalline salt (like table salt) is passed through a generator that produces hypochlorous acid and delivers it to your pool.
This is the exact same chemical that results when you place chlorine in your pool. Salt generated chlorine doesn’t add cyanuric acid in addition to the chlorine, which is added when “stabilized chlorine” such as dichlor or trichlor are used.
So a salt pool is simply a different way of delivering chlorine to your pool to make hypochlorous acid. It is no greener or different than using liquid or solid chlorine. Again, the end product that works to kill bacteria in water is hypochlorous acid and whether you produce this from salt, or deliver it to the water as chlorine, it is all the same thing.

Is a salt pool greener?

The short answer is no. People who sell salt generators want customers to think it is green since it uses salt that doesn’t have a bad name vs. chlorine that had a bad reputation. The end result of each method is the same production of hypochlorous acid that causes the exact same problems with pool water regardless of how the chlorine is delivered to the water. Salt-water generation of chlorine is no greener than adding bleach or granular chlorine to the water.

Does moss work in a salt-water pool?

The short answer is yes. It works the same way whether the sanitizer is added chlorine, bromine, cooper or silver salts, or ozone. It has the same positive effects with all types of sanitizers (except biguanides).
In our customer’s experience using moss with a salt generator, the amount of salt consumed by the generator decreases by 80-90% to keep the free chlorine in the pool between 1-2 ppm. This puts much less strain on the salt generator and results in less chlorine being added to the environment. The other effects of moss, such as pH stabilization and organic contamination effects are the same.