The topic of phosphates often takes center stage in the world of pool maintenance. But have you ever wondered how they find their way into the pools you service?

Sometimes, phosphates get into pools through the chemicals you introduce. Many products in the pool industry rely on phosphonic acid as their cornerstone, especially in start-up chemicals and stain or scale removers.

The second avenue through which phosphates make their entrance is organic. This can be attributed to fertilizers containing phosphorous. While you may not be directly dumping fertilizer into your pools, the natural phosphorous present in plants surrounding the pool area can be washed in during a downpour — a common occurrence.

The third source is none other than tap water itself. Drawing from a municipal water source might mean unwittingly introducing phosphonic acid, utilized to safeguard the integrity of the local pipelines. Each time you add new water, you might also be replenishing its phosphate content.

Diverse Varieties of Phosphates Did you realize that phosphates come in a multitude of varieties? In the water treatment sphere, we often employ the blanket term “phosphates” to encompass them all, but this can be somewhat misleading. The world of phosphates is diverse, with each type exhibiting distinct behaviors.

Let's begin by categorizing them into two main groups: organic phosphates and inorganic phosphates.

Organic Phosphates (Organophosphates) Organic phosphates, also known as esters of phosphoric acid, stem from a fascinating chemical transformation. Esters, which occur when an organic substance replaces a hydrogen atom in an acid, converts the substance from inorganic to organic. Think of esters as akin to fats and oils. Notably, they constitute natural fats and essential oils.These are not typically encountered in swimming pools.

Inorganic Phosphates

Now let's look into the more prevalent phosphates encountered in water treatment: inorganic phosphates.

Unlike phosphates bound in various esters, inorganic phosphate primarily comprises a mix of hydrogen phosphate (HPO42-) and dihydrogen phosphate (H2PO4-) ions.

We can further subdivide inorganic phosphates into two categories: condensed phosphates and orthophosphates.

Condensed phosphates are phosphates intertwined with salts, metals, or minerals like calcium. This category encompasses pyrophosphate, metaphosphate, and polyphosphate. For instance, calcium phosphate (Ca(H2PO4)2) serves as a prime example. These phosphates occur naturally but can also be synthetically combined for various industrial applications.

Orthophosphates, also known as reactive phosphates, feature prominently in water treatment, contributing directly to the mineral content of water.

This enrichment of nutrients can lead to issues like algae overgrowth in ecosystems. While orthophosphates exist naturally, they are also deliberately added to fertilizers. In swimming pools, orthophosphates reign supreme.

Phosphonic acid, widely used in water treatment, serves as a sequestering agent for metals and minerals like calcium. While highly effective, it leaves behind orthophosphates in the water.

Eradicating Phosphates

In water treatment, it is primarily orthophosphates that command our attention because they can make water care a challenge. Calcium phosphate, for example, has been known to wreak havoc on filters through hardening. Substantial phosphate levels in pool water can also be a contributing factor to algae proliferation.

Removing phosphates can significantly streamline water treatment, and specialized chemicals containing lanthanum salts can make this task achievable for pool service technicians.