Phosphorus is a vital resource for sustaining agriculture and nutrition, but a limited non-renewable resource. Thus, the recovery of phosphorus from waste activated sludge(WAS) was attempted by microwave heating and magnesium ammonium phosphorus(MAP) crystallization. Polyphosphate-accumulating organisms(PAOs) in WAS release phosphate from the cell when they are exposed to high temperature environments. Microwave heating caused phosphorus and ammonia to release from WAS. The amount was increased with increasing temperature, showing that 88.5% of polyphosphate present in the cells were released in the form of phosphate at 80oC. A similar result was also observed in the release of ammonia. On the other hand, both phosphorus and ammonia were crystallized with magnesium, and then was harvested as MAP. Phosphorus recovery rate reached almost 97.8%, but the ammonia was about 13.4%. These results cleary indicate that phosphorus could be recovered from WAS using a physiological trait of PAOs. Heavy metal analyses also show that the MAP crystal is useful and safe as a phosphorus fertilizer.

인산질 비료는 인광석(Ca3(PO4)2)에 물(H2O)과 황산(H2SO4)을 처리하여 생산하고 있으나, 이와 같은 과정에서 형성된 인산･석고 혼합물은 분리･여과과정을 거쳐 인산과 석고로 분리가 되고, 이때 분리･여과에 사용된 필터를 세척하는 과정에서 발생되는 침전물인 인산슬러지 성분은 칼슘(CaO) 14.6±1%, 인(P2O5) 8.0±1%, 미량 요소로 칼륨(K), 마그네슘(Mg), 황(S)등을 포함하고 있어 비료 성분으로써 활용가치 높다. 하지만 수분(H2O)이 60±5%으로 수분 함유량이 높아 제품 생산 원료 투입이 힘든 실정이다. 인산슬러지를 건조하기에는 비용이 많이 들며, 건조 후에는 분말이라 비료시비에 불편함이 따른다. 인산슬러지(60%)에 비료로서 사용가능한 Dolomite계 폐내화물(부산고토비료, 23%), 40%인산액(17%)과 배합하여 발열 반응을 일으켜 수분을 제거하면서 원형으로 입상화하여 건조하였다. 성분 분석 및 작물 재배시험을 통하여 확인 및 비료로서 사용여부를 확인 하였다. 성분은 수분측정기(105℃, 2H) 및 ICP-OES를 이용하여 비료공정시험법으로 분석한 결과로 수분(H2O) 9.54%, 마그네슘(MgO) 11.51%, 인(P2O5) 17.01%, 캄슘(CaO) 12%로 나왔다. 유해성분은 비료공정시험법과 폐기물공정시험법으로 분석하였고, 납(Pb), 구리(Cu), 비소(As), 시안(CN-), 6가크롬(Cr-6), 카드뮴(Cd), 수은(Hg) 등은 불검출 구리(Cu)는 기준치 이하 나왔으며, 크롬(Cr), 니켈(Ni), 티탄(Ti)은 비료공정규격에 나와 있는 유해성분 기준 이하로 나타났다. 작물효과시험에서는 대조구와 시험구를 비교시 엽장, 엽폭, 생체중, 엽수 등과 같이 모든 항목에서 비슷한 생육결과를 보였다.

The hydroxyapatite(HAp) for the present study was prepared with the wastewater sludge from semiconductor fabrication process and it was crystallized in an electric furnace for 30 min at 900℃. The adsorption characteristics of HAp for phosphate ion in aqueous solution has been investigated. The adsorbed ratio of phosphate ion for HAp were investigated according to the reaction time, amount of HAp, concentration of standard solution, pH of solution, and influence of concemitant ions. The amount of adsorbed phosphate ion decreased with the increase of pH due to the mutual electrostatic repulsion between adsorbed phosphate ions and competitive adsorption between phosphate ion and OH- ion in aqueous solution. The maxium amount of the adsorption equilibrium for phosphate ion was about 24 mg/g of HAp. The HAp would likely to be a possible adsorbent for the removal of phosphate ion in the waste water.