The Removal of Phosphate by Hydroxyapatite and Struvite Crystallisation in South Africa

Abstract

Nutrient removal by chemical means has, over the past decade, become an expensive practice owing to the scarcity of chemicals. A new method of phosphate removal by hydroxyapatite [Ca5(PO4)3OH] crystallisation has gained increasing interest as the need for the implementation of clean technology has become more apparent as we move into the environmentally conscious nineties. This method as well as another method, viz. struvite [NH4MgPO4-6H2O] crystallisation, will be discussed using results obtained from a laboratory scale study using three types of effluent, two demonstrating hydroxyapatite crystallisation and the third, struvite crystallisation. While it has been proven that phosphate crystallisation does work as a tertiary treatment (Van Dijk and Wilms, 1991) this paper will also show that the positioning of the crystalliser can vary to suit the need of the industry for which it has been designed.

Application of struvite precipitation in treating ammonium nitrogen from semiconductor wastewater

“…However, the opposite was found for high initial NH 4 -N concentrations. Struvite crystals seem to show limited growth at low ammonia nitrogen concentrations in the wastewater because the transportation of ammonium ions to the crystal surface is restricted due to the scarcity of ammonium ions in solution [30]. It is speculated based on the result obtained from Fig.…”

Removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings

“…Various physical methods have also been developed to remove phosphate from aqueous solution such as electrodialysis, reverse osmosis, and ion exchange [5,13,14]. However, most of these physical methods have proven to be either too expensive or inefficient.…”

Equilibrium and kinetic studies of adsorption of phosphate onto ZnCl2 activated coir pith carbon

“…Chemical treatments are more effective for phosphate removal; however, there are problems of sludge handling, its disposal, and neutralization of the effluent [7]. Various physical methods have been suggested including cross-flow filtration [8], crystallization [9], electrodialysis, reverse osmosis, ion exchange, and adsorption [4].…”