Removal of Phosphorus From Wastewater: a Review of Methods

Removal of Phosphorus From Wastewater. Wastewater generated by the industry and agriculture in many cases contains large amounts of ammonium and phosphorus. Insufficient removal of these from wastewater is a source of contamination of ground and surface water and causes eutrophication of water bodies. Biogenic elements cause proliferation of cyanobacteria. Excessive activity of algae degrades operation of water intakes and fishing, reduces the hydraulic parameters of the flow (the speed of flow near the banks); algal bloom reduces the amount of solved oxygen, has a negative impact on flora and fauna and disrupts normal functions of natural ecosystems.

High level of phosphates in wastewater has been a problem in the last decade, when the content of phosphate has grown from 6-8 mg/liter to 20-25 mg/liter. The main source of phosphates in sewage is, statistically, household wastewater and various industries, which use many synthetic detergents.

The problem of removing phosphates from wastewater has no optimal solution at this time and requires more research. Biological treatment of wastewater cannot achieve the required degree of contaminant removal, while the physical and chemical methods, while offering good results, require significant investment and create the problem of processing sediment, which forms in the process of chemical treatment.

Removal of Phosphorus From Wastewater. The biological method of phosphorous compound removal is based on the metabolism of biological sludge. Certain amounts of phosphorus are required for the formation of living cells, as well as a medium of transfer of energy, used to accumulate nutrients in a cell. The method of thorough removal of biogenic elements from wastewater is based on a traditional biological treatment combining aerobic and anaerobic processes. The biological phosphorus removal is based on the ability of several bacteria to accumulate soluble orthophosphates in cell in the form of insoluble polyphosphate. Oxidation of previously accumulated organic substances occurs in the aerobic part of the cell, and the energy is used by the bacteria to consume orthophosphate from the environment and turn it into polyphosphate to repeat the cycle of cell growth. However, the insoluble forms of phosphorus may hamper purification, since such compounds, in their solid form, cannot be consumed by microorganisms, thus requiring filtration or settling of the wastewater before biological treatment.

If the content of phosphorus is high, it may not always be possible to remove biologically. Chemical methods are used in this case. Reagent selection depends on its availability and cost in the area. The place of mixing the chemical with wastewater is determined individually based on previous laboratory research and later testing of the results in industrial applications.

обновлено: January 6, 2017 автором: dannik