灼烧净水污泥对外源磷的吸附和固定作用

研究了不同投加方式下(混匀和覆盖)灼烧净水污泥对外源磷的累积吸附效果,以及吸附外源磷后底泥等温吸附效果和在厌氧条件下内源磷释放情况.结果表明,混匀和覆盖条件下,底泥对上覆水中磷的累积吸附量分别为11.496 mg和11.042 mg,明显高于对照实验(7.219 mg).通过对吸附外源磷后的底泥进行等温吸附实验,发现混匀条件和覆盖条件下磷最大吸附量(Smax)均有所增加,并且前者(7.795 mg·g~(-1))要高于后者(6.807 mg·g~(-1)),但磷平衡浓度(EPC0)前者(0.83mg·L~(-1))却明显大于后者(0.64 mg·L~(-1)),表明混匀条件下内源磷更容易释放.在厌氧环境下,混匀方式内源磷释放量仅为0.93 mg,不仅低于覆盖(1.49 mg),也明显低于对照实验(7.76 mg).覆盖条件下比释放速率的平均值(0.006 14)大于混匀(0.003 96),并均低于对照实验.这说明混匀对内源磷的持留能力更强.暗示了单纯用EPC0值来评价底泥对磷的固定能力是不妥的.

External Phosphorus Adsorption and Immobility with the Addition of Ignited Water Purification Sludge

The cumulative adsorption of external phosphorus (P) by water purification sludge after ignition under different addition methods (mix and cover) was investigated along with the adsorption isotherm and the release of internal P after external P adsorption. The cumulative adsorption of external P was 11.496 mg (mix) and 11.042 mg (cover) and these values were higher than those in the control (7.219 mg). The maximum sorption capacity (Smax) increased under the mix and cover and the former (7.795 mg·g^-1) was higher than the latter (6.807 mg·g^-1). However, the zero equilibrium P concentration (EPC₀) in the mix was 0.83 mg·L^-1, higher that in the cover (0.64 mg·L^-1). The result suggests that the internal P was easily released in the mix method, compared to the cover method. Under anaerobic conditions, the release of the internal P was 0.93 mg in the mix, lower than that in the cover (1.49 mg) and in the control (7.76 mg). In addition, the specific release rate in the cover method was 0.00614 (mean), higher than that (0.00396) in the mix method. Noticeably, these data were lower than those in the control, indicating that the retention of P under the mix method was higher, compared to the cover and the control and it is challenging to evaluate the P retention with EPC₀.