Phosphate removal using blast furnace slags and opoka-mechanisms
2000 (English)In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 34, no 1, 259-265 p.Article in journal (Refereed) Published
The abiotic sorption efficiency of on-site wastewater treatment systems can be improved by using a strongly sorbing filter material that, if it retains phosphorus (P) in a plant available way, can be used as fertiliser when P saturation is achieved. Two materials, blast furnace slag and the siliceous sedimentary rock opoka, have shown a high P sorption capacity and were included in a set of experiments to investigate the P retention mechanisms from model P-solution. Experiments focusing on the P sorption, capacity and calcium (Ca) and PO4 determination were carried out. The pH was also measured. The P sorption experiment showed that some slags were efficient P retainers, while the opoka was the least efficient P retainer. The pH decreased in all samples as a function of P addition. In the slag samples, the Ca concentration also decreased as a function of P addition, suggesting Ca-P precipitation as the major P removal mechanism for the slag. The Ca and PO4 speciation data ruled out the formation of amorphous calcium phosphates and/or octacalcium phosphate as the major P removal mechanism. However, the calculated ion activity products displayed clear evidence that hydroxyapatite had precipitated above a certain critical supersaturation limit. This would explain the poor P retention efficiency of the opoka samples in this study as the ion activity products were too low. The finding that direct hydroxyapatite formation is the predominant P removal mechanism might have important implications for their possible use as fertiliser due to the poor solubility of hydroxyapatite.
Place, publisher, year, edition, pages
2000. Vol. 34, no 1, 259-265 p.
blast furnace slag, fertiliser, hydroxyapatite, opoka, P removal mechanisms, phosphorus
IdentifiersURN: urn:nbn:se:kth:diva-19466ISI: 000084304300029OAI: oai:DiVA.org:kth-19466DiVA: diva2:338158
QC 201005252010-08-102010-08-10Bibliographically approved