Recovery of nitrogen and phosphorus from digested effluent of sludge by paper mill lime mud and fly ash addition
造纸白泥和粉煤灰的添加对污泥消化液中氮磷回收的影响

The anaerobically digested effluent of sludge has plenty of nitrogen and phosphorus, when the digested effluent of sludge is discharged into the environment directly without treatment, the water body would be polluted seriously. There are not enough Mg2+ and Ca2+ contents to form MAP in the digested effluent of sludge, which inhibit the effects of nitrogen and phosphorus recovery seriously. The paper mill lime mud (PMLM) and fly ash(FA) were introduced into the recovery of nitrogen and phosphorus from digested effluent of sludge, which could raise the pH and increase the effects of nitrogen and phosphorus recovery of anaerobically digested effluent of sludge obviously. The experimental results showed that when the dosage of PMLM was 4 g/(L·h), and the aeration time was 12 h, the recovery rates of PO43--P and NH3-N were 64% and 45%, respectively, as well as the pH value was 10.19. Besides, when the dosage of FA was 4 g/(L·h), and the aeration time was 12 h, the recovery rates of PO43--P and NH3-N were 46% and 41%, respectively, and the pH was 9.63. However, without PMLM and FA addition, when the aeration time was 12 h, the recovery rates of PO43--P and NH3-N were only 20% and 19%, respectively. Therefore, it was important to recover the nitrogen and phosphorus from anaerobically digested effluent of sludge with PMLM and FA addition. The results also showed that the lifting speed of pH accelerated when HRT increased, and the bigger the HRT was, the larger the lifting range was.