Phosphates are salts of phosphoric acid, meaning they are compounds of phosphoric acid with specific, usually alkaline, metals.

Which phosphates are soluble in water?

Dihydrogen phosphate dissolves best in water, while hydrogen phosphate and phosphates dissolve less effectively. There are also polyphosphates, which consist of phosphate "chains," and organic phosphorus-containing compounds.

Phosphorus and nitrogen are essential biogenic elements necessary for the proper functioning of all living organisms. In water, phosphorus exists in the form of inorganic, organic, and organo-mineral compounds and is also part of the cells of aquatic organisms. Notably, inorganic compounds have the highest bioavailability.

When phosphorus and nitrogen levels in water become excessive, microorganisms receive more nutrients, leading to rapid reproduction. This process, known as eutrophication, reduces oxygen levels, kills fish, and makes water treatment more complex due to the increased biomass.

Phosphate cycle in nature

The diagram below illustrates the phosphate cycle in nature, showing how phosphorus moves through living organisms, sediment deposits, industrial processes, and the proliferation of cyanobacteria (blue-green algae), which multiply aggressively in water bodies with an excess of biogenic elements—nitrogen and phosphorus.

Regarding phosphate sources, they include wastewater, agricultural runoff, and weathering of rocks. We will analyze these in detail below.

Sources of phosphates in water

It is commonly believed that phosphates enter water bodies primarily through detergents. However, there are many more sources of phosphate pollution. As mentioned earlier, phosphorus is a microelement involved in microbial life processes. Problems arise when natural water bodies cannot cope with the volume of pollution discharged into them. Today, phosphates in marine and freshwater systems present a significant environmental challenge.

Data on the proportional sources of various pollutants in the EU vary significantly across different sources. The chart below provides an overview as of the year 2000.

Phosphate sources in water

With the introduction of legislation limiting phosphate discharge into water, the distribution of pollution sources in the EU has changed. Agriculture is now the primary contributor.

Due to the lack of regulations on detergents in Ukraine, the situation remains unchanged or has worsened. Most EU countries began imposing restrictions on phosphate use in the 1980s, but a clear visualization of the issue in Ukraine is unavailable.

One pressing concern, particularly for Kyiv residents, is the state of the Dnipro River. Over the last 20 years, phosphate concentrations in water supplied to the Bortnychi Aeration Station have increased fivefold—from 6–8 mg/L to 30 mg/L, while the maximum permissible concentration (MPC) is 8 mg/L. Given these conditions, wastewater treatment facilities fail to provide adequate purification, leading to increased phosphate discharge into surface waters and further eutrophication.

Phosphate concentration (mg/L P₂O₅) in water bodies around Kyiv:

• Nivka River – 0.1–2.29
• Irpin River – 0.26
• Dnipro River (upstream of Kyiv) – 0.2
• Discharge canal from Bortnychi Aeration Station – 4.5

The permissible concentration is 0.01 mg/L.

Determining phosphates in water

Phosphates are identified using DSTU 7525:2014, "Drinking Water. Quality Requirements and Control Methods," as well as GOST 18309-2014, "Water. Methods for Determining Phosphorus-Containing Substances" (previously used).

MPC of phosphates for different water sources (mg/L):

• Drinking water – 3.5
• Tap water – 0.4
• Flowing water bodies – 0.1
• Ponds and lakes – 0.05
• Wastewater – 0.03

Where do phosphates in water come from?

Human waste is a natural source of phosphorus. A person excretes about 1.5 g of this microelement daily. Additionally, biogenic elements enter wastewater from household chemicals.

Most households and enterprises discharge wastewater into centralized treatment facilities. These effluents contain biological phosphorus as well as phosphate components from detergents, food products, etc. Even modern water treatment systems struggle with high pollution volumes, while Ukrainian treatment plants require urgent modernization.

Weathering of rocks

Phosphorus naturally enters soil and water from minerals, a process that varies by region. Areas with phosphate and apatite deposits experience higher natural phosphate inputs into water.

Agricultural activities

Manure and fertilizers are primary sources of biogenic nitrogen and phosphorus. When plants cannot absorb all applied nutrients, they remain in the soil and are washed into nearby water bodies by rain or melting snow, leading to eutrophication. Mitigation techniques include:

• Optimizing fertilizer application based on quantity and season.
• Planting perennial crops or crop rotation to avoid bare fields, which experience higher erosion and phosphate runoff.
• Planting trees and shrubs around fields to absorb excess nutrients.
• Restricting livestock access to water bodies.

Rainwater runoff

Rainwater runoff from urban areas carries various pollutants, including biogenic elements, into water bodies, often through stormwater drainage systems without treatment.

Main applications of phosphates

Phosphates are widely used in various industries.

Detergents

Phosphates in laundry detergents, dishwashing liquids, and other cleaning agents act as chelating agents, binding calcium and magnesium ions to prevent scale formation and enhance surfactant effectiveness.

Sodium tripolyphosphate is the most common detergent ingredient, serving as a chelating agent and buffer. It also emulsifies fats. In some detergents, insoluble phosphates act as abrasives.

Due to their environmental impact, phosphate-containing detergents are banned or severely restricted in most European countries.

Fertilizers

Three main types of phosphate fertilizers are used:

1. Phosphate Rock Powder – Least water-soluble; effective only in acidic soils.
2. Superphosphate – Produced by treating phosphate rock with sulfuric acid; contains calcium sulfate as a ballast.
3. Double Superphosphate – Higher active ingredient concentration but more harmful to the environment.

Other uses of phosphates

Phosphates are widely used in the food industry, particularly in meat products, to reduce weight loss and enhance preservation properties.

In boiler water, phosphates are added to minimize scale formation.

Sodium monofluorophosphate is used in toothpaste, where it decomposes to release fluoride ions for enamel protection.

Phosphate removal from water

As mentioned earlier, traditional aerobic wastewater treatment technology does not fully remove phosphates, allowing them to enter water bodies used for drinking water intake.

The removal efficiency of phosphates using traditional methods ranges from 10-25%, depending on the season.

Modern technologies for phosphorus removal from wastewater include:

• Chemical methods: Treatment with soluble salts of sodium orthophosphate results in the formation of fine anhydrous precipitates, which coagulate into larger flocs when interacting with alkalis.

• Physicochemical methods: Treatment using magnetic fields, electrocoagulation, and crystallization.

• Biological methods: Modification of biomass to incorporate phosphorus into cellular matter for anaerobic water treatment.

These methods significantly increase the cost of treatment technology. In wealthier countries where such technologies have been implemented, restrictions on phosphate content were still introduced, as it is more cost-effective to develop and promote phosphate-free household chemicals than to treat wastewater.

Where do phosphates in drinking water come from?

Water treatment systems at municipal facilities are unable to fully remove phosphorus, allowing some of it to enter drinking water.

Modern drinking water purification technologies can achieve high levels of phosphorus removal. However, these technologies are costly and are not widely used in Ukrainian water treatment plants. A practical solution for household drinking water purification is installing reverse osmosis filtration systems.

How do phosphates affect human health?

Phosphates have two potential health effects: internal and external.

When present in water used for bathing and dishwashing, phosphates may cause dermatitis and skin irritation. Individuals with atopic skin conditions may experience flare-ups due to phosphate exposure.

Regarding phosphates in drinking water, it is important to note that phosphorus is naturally present in many foods. It is an essential element for enzyme synthesis, a component of nucleic acids and phospholipids, and a key constituent of human bones in the form of hydroxyapatite, which contains approximately 16% phosphorus. An excess or deficiency of phosphorus can lead to dysfunctions in the endocrine, urinary, and muscular systems.

Moreover, phosphorus-based additives (such as phosphoric acid, potassium phosphate, and various organophosphates) are widely used in the food industry.

Detergent regulations

In the European Union, phosphate-based household laundry detergents have been banned since 2011, and since 2017, phosphate-based dishwasher detergents have also been prohibited. Many EU countries had already phased out or significantly restricted these detergents as early as the late 1980s. Additionally, the use of phosphorus-containing fertilizers is restricted in many European countries. In the industrial sector, strict regulations and heavy fines are imposed for discharging phosphorus compounds into sewage systems.

In Canada, phosphate content in detergents was first limited in 1973 to 2.2% phosphorus (approximately 26% tripolyphosphate). In 2010, this limit was further reduced to 0.5% (approximately 6% tripolyphosphate). Today, phosphate-based detergents are no longer in use.

The situation in the United States is similar to that in Europe, although regulations were introduced later. Some U.S. states restrict only phosphate-containing laundry detergents, while others regulate even industrial chemicals. However, wastewater treatment facilities in the U.S. provide comprehensive phosphate removal.

Japan completely banned the use of phosphates in 1986.

What about Ukraine?

In Ukraine, phosphate content is regulated only by technical specifications for final products.

The issue of phosphate regulation was first raised in 2013, when the Cabinet of Ministers submitted a draft law to the Verkhovna Rada proposing a phased ban on the production, import, and sale of phosphate-based detergents and household chemicals in Ukraine. The proposed restrictions were as follows:

• 2014: Phosphate content limited to 17%

• 2016: Phosphate content limited to 10%

• 2019: Phosphate content limited to 5%

• 2021: Phosphate content limited to 0.7%

However, the bill was not passed.

The issue resurfaced in 2018 with Bill No. 8138 ("On State Regulation in the Field of Detergents"), but the Verkhovna Rada did not review it. The bill proposed banning the import of detergents containing anionic surfactants that did not comply with EU standards, limiting phosphorus content to 5%, and completely prohibiting the use of chlorine and organochlorine compounds.

By 2021, the bill suggested further restrictions:

• Production, import, and sale of detergents with more than 3% anionic surfactants and more than 0.2% phosphates would be prohibited.

In October 2019, a similar bill (No. 1173) was rejected and sent for revision.

Phosphate regulation is crucial for the ecological health of surface water bodies.

How can you reduce phosphates in water?

Avoid purchasing household chemicals that contain phosphates or opt for alternatives with low phosphate content.

How to choose the right detergent?

1. Read product labels carefully to check the ingredients.

2. European-made products generally contain fewer phosphates than domestic alternatives.

3. If one detergent produces significantly more foam than another when using regular tap water, it likely has a higher phosphate content.