Helsinki University of Technology, Water and Wastewater Engineering, P.O. Box 5200, FI-02015, TKK, Finland.
Water Sci Technol. 2009;60(9):2413-8. doi: 10.2166/wst.2009.601.
A full-scale study at Pihlajaniemi BNR plant in Savonlinna Finland investigated in detail the conditions in which phosphorus release in the secondary clarifier can occur. For this purpose nutrient and ORP profiles were taken in different process conditions from the sludge blanket in the secondary clarifiers. The results show that in anaerobic conditions secondary phosphorus release can take place in the secondary clarifiers without any addition of exogenous COD. Long sludge retention time in the secondary clarifier was a prerequisite of anaerobic conditions in the sludge blanket, but retention time required varied with seasons and process conditions. Some indications of simultaneous phosphorus release and denitrification without COD input was also found. The re-absorption of the released phosphorus was observed in those parts of the sludge blanket, where nitrates were present. Even with very long sludge retention times the released phosphorus stayed inside the sludge blanket and it did not impair the effluent quality. An 18 month follow-up of the BNR process revealed, however, that occasionally dissolved phosphorus escaped from the sludge blanket. It was suggested, that this was the consequence of the missing nitrate containing layer at the upper part of the sludge blanket.
在芬兰萨翁林纳的皮赫拉亚米 BNR 工厂进行了一项全面研究，详细研究了在二级澄清池中发生磷释放的条件。为此，从二级澄清池的污泥层中在不同的工艺条件下采集了营养物和 ORP 分布情况。结果表明，在厌氧条件下，无需外加任何外源性 COD，二级澄清池也可以发生二次磷释放。二级澄清池中的污泥停留时间长是污泥层中厌氧条件的前提条件，但所需的停留时间随季节和工艺条件而变化。还发现了在没有 COD 输入的情况下同时发生磷释放和反硝化的一些迹象。在存在硝酸盐的污泥层的某些部分观察到了释放的磷的再吸收。即使污泥停留时间非常长，释放的磷也仍留在污泥层中，并且不会影响出水质量。然而，对 BNR 工艺进行的 18 个月的后续研究表明，偶尔会有溶解态的磷从污泥层中逸出。据推测，这是由于污泥层上部缺少含硝酸盐的层所致。
