Phosphates are chemicals containing the element phosphorous, and they affect water quality by causing excessive growth of algae. About 3 1/2 pounds of phosphates per person enter the environment in the United States annually from farms, yards, waste water and factory waste. Phosphates in water feed algae, which grow out of control in water ecosystems and create imbalances, which destroy other life forms and produce harmful toxins
Excess Phosphates in Water
Excess phosphates create water that’s cloudy and low in oxygen. All plants need phosphates to grow, but phosphorous is normally present in surface water at a rate of only 0.02 parts per million. Introducing additional phosphates in water results in a massive growth of algae, which are aquatic plants including many single-celled, free-floating plants. Excessive amounts of algae cloud the water in an effect called an algal bloom, which reduces the sunlight available to other plants and sometimes kills them. When the algae die, the bacteria that break them down use up dissolved oxygen in the water, depriving and sometimes suffocating other aquatic life
When the amount of total phosphorous exceeds 100 parts per billion (ppb) in streams or 50 ppb in lakes, eutrophication the effect of algal blooms is a danger. Excessive phosphate levels also affect the processes in drinking water treatment plants.
Phosphorus and water quality
Phosphorus is one of the key elements necessary for the growth of plants and animals. Phosphates PO4— are formed from this element. Phosphates exist in three forms: orthophosphate, metaphosphate (or polyphosphate) and organically bound phosphate. Each compound contains phosphorous in a different chemical formula. Ortho forms are produced by natural processes and are found in sewage. Poly forms are used for treating boiler waters and in detergents. In water, they change into the ortho form. Organic phosphates are important in nature. Their occurrence may result from the breakdown of organic pesticides which contain phosphates. They may exist in solution, as particles, loose fragments or in the bodies of aquatic organisms.
Chemical and Physical-Chemical Wastewater Treatment Methods to Remove Phosphorus Compounds
At this time, the chemical phosphorus removal method for wastewaters is both used and researched. This method has been widely used by small and medium-output plants. During chemical purification of wastewater, the reagent ions interact with soluble salts of the orthophosphoric acid, thus creating highly dispersed colloid phosphate sediment. Meanwhile, the chemical reacts with water-borne bases to produce large-flake sediment. This sediment triggers coagulation of the high-dispersion colloid phosphate sediment and suspension, it also adsorbs some of the phosphorus-bearing organic compounds, and then it is withdrawn from the system. Salts of two- and three-valent metals are used as reagents. The practice of wastewater treatment widely uses such coagulants as aluminum and iron salts, and also lime. Adding aluminum sulfate to wastewater in the presence of alkali produces the following reaction
Phosphorus elimination
- Mechanical treatment
During mechanical treatment phosphorus contained in the particulate material is removed from the waste water together with primary sludge which results in a TP removal of 10 – 15 %. Biological incorporation, enhanced biological P-removal and chemical precipitation are state-of-the-art processes to reliably reduce P-load from waste water. The total phosphorus loads removed from the waste water in most of the processes applied in practice end up in the sludge. In principle the P-content of the sludge can be recovered and reused which is of increasing relevance for the long term availability of this limited resource.
- Chemical-physical P-elimination
The most reliable and most frequently applied removal process is chemical phosphorus precipitation by addition of metal salts. Dissolved phosphorus is converted to solids which are removed from the waste water together with the sludge. If very low effluent concentrations < 0.5 mg TP/l) have to be achieved secondary effluents can be treated by flocculation filtration.
Boiler Scale Inhibitors
Boiler water chemical treatment is necessary to prevent or control scale and deposit formation. The formation of scale and sludge can cause tube failures, restrict circulation, reduce system efficiency, and compromise your boiler system’s reliability.
Boiler scale is a deposit that forms directly on heat transfer surfaces when constituent solubility limits are exceeded and the resulting compounds precipitate onto the tube surfaces. Such deposits may contain calcium, magnesium, phosphate, iron, and silica. A tenacious form of boiler scale results when calcium precipitates in the form of calcium carbonate.
