采用数学模拟评价生物营养物去除工艺的除磷效果

Model-based Evaluation of Phosphorus Removal Efficiency with BNR Processes

磷的去除与回收可以结合生物营养物的去除一并实施,通过收集厌氧池富磷上清液形成鸟粪石(MAP)沉淀的方式予以实现,这同时也可提高生物除磷效果或降低生物除磷所需的最低C/P值。为此,一种考虑了磷回收的新型生物营养物去除(BNR)工艺———BCFS(在荷兰研发并应用。然而,有关磷回收以及它对生物除磷效果影响方面的信息在运行实践中仍不够清晰。采用数学模拟技术,结合代尔夫特(TUD)生物除磷代谢模型与活性污泥2号模型(ASM2),对不同运行参数下的磷回收以及它对系统工况的影响做了评价。模拟试验结果表明,存在着最佳的上清液侧流比,当侧流比大于此值时将增大磷的回收成本,而且除磷效果也将受到影响;在保证出水水质达标(<1 mgP/L)的情况下,生物除磷所需进水COD/P(可生物降解COD)最小值可由20降低到10,此时的磷回收率为36%。动态进水(变流量或负荷)模拟试验表明,其对厌氧池上清液中磷的富集略有影响,但进行磷回收时并不影响系统出水的磷浓度。

Phosphorus removal and recovery can be combined in biological nutrient removal （BNR） process. This can be realised by struvite（MAP） precipitation from the supernatant of the sludge in anaerobic tank, and can be beneficial for either improving effluent quality of bio-P removal system or lowering the influent COD/P ratio required for bio-P removal. For this reason, a patented BNR process, BCFS, was developed and applied in the Netherlands. Several questions relating to P-recovery and behaviour of the system remain unclear and need to be ascertained. For this purpose, modelling technique was employed in this study. With the help of a previous developed model describing carbon oxidation and nutrient removal, three cases were fully simulated. The simulations demonstrate that there is an optimal stripping flow rate, P-recovery will increase in costs, and bio-P activity might be negatively affected due to decreased bio-P efficiency if this value is exceeded. The minimal CODbiod/P ratio required for the effluent standard （ 〈 1 mgP/L） can be lowered from 20 to 10 with 36% of P-recovery. A simulation with dynamic inflow reveals that the dynamic influent loads affect slightly the anaerobic supernatant phosphorus concentration but the effluent phosphorus concentration will not be affected with regular P-recovery.