鸟粪石
磷
化学
浸出(土壤学)
镁
污水污泥
磷酸
降水
磷酸盐
铵
污水
无机化学
环境化学
环境工程
环境科学
土壤水分
有机化学
土壤科学
气象学
物理
作者
Nothando C. Shiba,Freeman Ntuli
标识
DOI:10.1016/j.wasman.2016.07.031
摘要
Raw sewage sludge from East Rand Water Care Association (ERWAT) had high phosphorus (P) content, approximately 15.2% (w/w) P2O5, which indicates a potential resource for the limiting nutrient. Leaching sewage sludge with 1M sulphuric acid at 5% solid loading for 2h resulted in an 82% phosphorus extraction. However, the phosphorus was recovered as iron phosphates, thus a further purification step using ion exchange to remove iron was required to increase the degree of P release. Magnesium oxide and ammonium hydroxide were used as magnesium and nitrogen sources, respectively, as well as pH regulators to precipitate P as struvite. 57% struvite was precipitated and the total phosphorus content of the precipitate was 25.9%. Kinetic studies showed that the leaching of phosphorus follows the Dickinson model for the first 100min with a rate of reaction of about 2×10-5s-1. The rate limiting step is controlled by diffusion. Phosphorus solubility in 2% critic acid was almost 96%, which is the amount of phosphorus available to plants if the precipitate is applied as a fertiliser. Environmental, gram-positive Bacillus subtilis were found in the precipitate, which are harmless to the environment since they already exist in the soil where the precipitate can be applied as a fertiliser.
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