Fighting Phosphates

The link between phosphates and algae blooms in pool water is becoming clear all the time. Here's what you need to know.

Pool service technicians face a constant battle to keep algae out of their customer's pools. Doing so means keeping a close eye on phosphate levels.

The connection between phosphates and algae growth is well documented. But what exactly are phosphates and how do they affect pool water and how should service techs cope with them? Here's some insight:

What are Phosphates?
Phosphates are biological building blocks that are formed when phosphates exist in many different forms. Most of these come from natural sources such as rivers, lakes, oceans or mined rock. The U.S. is one of the largest producers of phosphate rock.

Phosphate is termed a "pollutant" and is primarily used in soaps, detergents, shampoos and even soda pop. Other phosphate sources include fertilizers, organic debris such as leaves and bark, and some pool chemicals. Phosphate pollution in lakes and streams is caused mainly by overdevelopment, which causes extreme amounts of byproduct waste to end up in natural water systems.

Testing For Phosphates should be done regularly to help you stay ahead of algea. It takes far less effort to prevent a problem than it does to correct an existing one. By testing regularly, you will know when problems are forming giving you plenty of time to correct it before algae begins to form.

The smoking gun and the bullet
Most of the phosphate in pool water enters in the form of compound such as tri-sodium phosphate. Algae cannot use these combined phosphates as a nutrient for growth. It is not until the compounds of phosphates are broken down in the water to a free ortho-phosphate that algae can begin to thrive.

Once orth-phosphate is removed from water, it's harder for algae to obtain because it is not readily available until the phosphate compounds break down as a result of oxidation, hydrolysis enzymatic digestion.

In short, all phosphates end up as ortho-phosphate, which feeds algae. Think of it like this: Phosphate compounds are the smoking gun, but the orhto-phosphate is the bullet.

How much is too much?
The technology of phosphate removal is still new to the pool industry, and lots of erroneous information is being communicated regarding the proper phosphate levels needed to ensure a lack of algae growth.

Some information states that phosphate removal is irrelevant because algae can grow at levels as low as 10 ppb. This would be correct if you were dealing with lake water. However, extensive studies in pool water have shown that algae cannot grow in a sanitized environment, even at levels in the 200 ppb range.

However, these same studies showed that when the ortho-phosphate levels reached the 500 ppb mark, algea blooms would be present even in properly sanitized pools. The higher the phosphate level goes, the more the algea flourishes and the more resistant it becomes. It is strongly advised that the phosphate be maintained in pool water at a level of 125 ppb for an algae free pool.

Remember, when it comes to swimming pools, we are only concerned with the free ortho form of phosphate. When testing pool water for the presence of phosphates, use a test kit made specifically for free ortho-phosphate.

The Role of Algeacides
There is a belief that phosphate removal can take the place of algeacides. This needs some explaining because you must first understand that phosphate removers don't kill existing algae. To accomplish a kill, you need to superchlorinate and/or us a good algaecide.

When the existing algae has been eliminated, then the process of phosphate removal becomes crucial. As algae dies off, it exudes free ortho-phosphates that could lead to further growth even in the presence of an algeacide.

Phosphate removal has been proven as the key in preventing algea recurrence. However, anyone who has dealt with pool maintenance for a while can attest that there is no "magic pill" in the fight against algae. Basically, it takes conscientious work and a regiment that includes proper pool-water balancing, correct sanitizer levels, and regular doses of shock and algaecide. Phosphate removal is another effective, proven partner to help in the battle against stubborn, resistant algae.

Benefits of Removal
Removing phosphates and maintaining proper levels can be very beneficial. First of all, you will improve the overall quality of the water. In many cases, high levels of phosphates can tie up free chlorine (especially with pools on salt generators).

Also, using excessive amounts of algeacide can cause other problems such as foaming or staining from high mineral content. While we are continuing to learn more every day about phosphate removal, the benefits of it's removal have been soundly proven in both the laboratory and the field.