Phosphorus Removal From Waste Water By Induced Crystallisation

People have paid great atention to the eutrophication because it deteriorated the water quality. To solve the problem of the lake eutrophication related phosphorus, the elimination of phosphorus that can be used by alga is most important. Phosphorus is an important non-renewable resource and may be exhausted in the near future. Phosphorus recovery from wastewater treatment process is one of most effective ways to solve the phosphorus resource crisis. Currently, in order to control the water eutrophicatio, people are more and more concerned about phosphorus removal from wastewater. Phosphorus removal from waste water by crystallization attracts much attention for its particular advantages, such as simply theory, easy realization, good stability, recovery of useful phosphatic deposit and so on. This paper mainly focuses on the phosphorus removal and recovery from wastewater by crystallization.This paper introduces and reviews two phosphorus removal methods including phosphorus removal through biological activity as well as chemical precipitation, the mechanisms and processes, and new development and study field of phosphorus removal; applications of phosphorus recovery by crystallization technologies in wastewater treatment including often used process flows, analysis of product components and economical benefit. Three phosphorus recovery processes are described, including Kemwater REcycling PROcess (KREPRO), fractionation including phosphorus recovery (Cambi -KREPRO) and incineration combined with phosphorus recovery (Bio-Con). In these processes 75% of phosphorus in the sludge can be recycled and reused as ferric phosphate or phosphoric acid.The experiments include two parts. In the first part, iron ion and calcium ion were compared for removing phosphorus, and the calcium ion was choosen as suitable reagent. In the second part, kinetic parameters of hydroxyapatite in wastewater containing phosphorus weer mensurated; tobermorite crystals was used as crystal seeds, and the influences of the reaction conditions on crystallization were studied. Results show that the phosphorus removal by crystallization gradually increases with the increase of pH value, and the best pH value was 9.5; the phosphorus removal increases with the dosage of calcium ions, and the optimal Ca/P (molar ratio) is 5.01; the increase of the dosage of crystal seeds and stirring time can also improve the phosphrus removal. When tobermorite crystals were used as the crystal seeds, the alkalinity of original water had little influence on the phosphate removal.With the optimal conditions, phosphorus can be stably and effectively removed with...