Abstract
In order to improve the recovery rate of potassium (K) from swine wastewater in the simultaneous recovery of nitrogen (N), phosphorus (P) and potassium, a recovery experiment was carried out with a pH range from 10 to 11. Further, to evaluate biological treatment of the solution after recovery, semi-batch treatment with activated sludge was investigated. It was found that with the conditions of pH 10.5, P/(N＋K) of 1.3, and Mg/P of 1.2 in molar ratio, N and K could be recovered at a rate of over 80 % and P concentration could be kept under the discharge standard. With these conditions, an N recovery rate of 81 % was reached, much higher than the previous recovery rate of 67 % and indicating improvement of the K recovery rate. An N recovery rate of 89 % was reached, so a high recovery rate was maintained. Furthermore, the net P recovery rate was 39-79 %, indicating that more P could be recovered than was added. TOC could be removed from the solution after recovery at a pH of 10.5, the same as from swine wastewater, without neutralizing the solution. No biological denitrification was required to meet the discharge standard for nitrogen.
