污泥厌氧消化液中碳酸盐对回收磷的影响
Effect of carbonate on phosphorus recovery from anaerobic digestion supernatant of sewage sludge
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摘要: 为探讨污泥厌氧消化液中碳酸盐对以磷酸钙盐形式回收磷的影响，以粉煤灰浸出液为钙源，考察了消化液中的碳酸盐对磷回收过程和磷回收产物性质的影响。实验结果表明，在反应pH为10、反应钙磷摩尔比为1.67、反应时间为10 min的条件下，消化液碳酸盐浓度为2 400 mg/L(以CaCO3计)时，磷的回收率为78.53%，回收产物中磷含量(以P2O5计)为28.93%；对消化液进行盐酸预酸化使pH达到4及以下时，磷回收率接近100%，回收产物中磷含量(以P2O5计)达到43.08%。消化液中碳酸盐的存在易形成碳酸钙沉淀，从而降低了磷回收率、回收产物中磷含量以及回收产品的纯度；预酸化能够有效地去除消化液中的碳酸盐并降低了其对磷回收的不利影响。Abstract: The influence of carbonates in the anaerobic digestion supernatant on the precipitation of calcium phosphates was studied with the leaching liquor of fly ash as the calcium source, the effects of carbonates on the precipitation of calcium phosphates and the characteristics of the product were investigated. The experimental results showed that, when the reaction pH value, the reaction Ca/P molar ratio and the reaction time were 10.0, 1.67 and 10 min, respectively, at the concentration of carbonates 2 400 mg/L (as CaCO3), the P recovery rate was 78.53%, and the P content (as P2O5) in the recovered product was 28.93%. By adding hydrochloric acid for adjusting the digestion supernatant to the pH value 4 and below, the P recovery rate approximated to 100%, and the P content (as P2O5) in the recovered product reached 43.08%. The calcium carbonate in the digestion supernatant tended to precipitate under the condition of high concentration of carbonates, and thus reduced the P recovery rate, the P content in the product and the purity of the product. The carbonates were removed effectively by the acidification, as decreased its adverse influence on the P recovery.
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