Study of Phosphates Adsorption from Water by Recycled Concrete

Abstract

Phosphates pose in natural waters form of bioavailable phosphorus. Phosphorus is an important essential element, nutrient, whose incidence in surface waters promotes the growth of organisms in most ecosystems and thus is also a main and limiting cause of eutrophication. The main source of phosphates are mainly outflows from waste water treatment plants, runoff from agricultural cultivated land, rain water, etc. In addition to biologically available forms it represent especially orthophosphates and polyphosphates. The burden of surface waters with phosphorus involved outflows from waste water treatment plants (26 %), industrial waste water (3 %) and the most water from diffuse sources such as agriculture and erosion.

Phosphorus can be removed from water by chemical, biological, physico-chemical methods, and these methods are often combined with each other.

Adsorption methods are based on capture of phosphate on the surface of various structural materials. Proven e.g. blast furnace slag, fly ash, activated bentonite, activated alumina, iron oxide and others. These materials are mostly used as filter media where appropriate column with the floating filling.

Our work deals with the verification of sorption properties of recycled concrete in removing phosphates from water. For laboratory static test was used crushed railway ties concrete of different grain size, a model water prepared by dissolving a defined amount of KH₂PO₄ in distilled water and surface water, one-off collected from the Vltava river. Residual phosphate content was determined by adsorption spekrofotometry.