Purpose

Nitrogen (N) and phosphorus (P) are the key elements leading to eutrophication, and it is important to jointly control N and P release from sediments into the water column.

Methods

Different mixed materials including P sorbent, natural organic carbon (C), and an oxidizing agent were applied in a 1-year pilot-scale experiment.

Results

The addition of iron-rich (IR) clay and Phoslock agent promoted the formation of iron bound P (Fe(OOH)~P) and calcium bound P (CaCO₃~P) in sediments, respectively. IR clay offered more advantages in immobilization of phosphorus as refractory P, and the Phoslock agent more effectively reduced the risk of P release into water, which was expressed as a low equilibrium P concentration (EPC₀). Mixtures of sugarcane (SU) detritus and IR clay exhibited high carbohydrate (CHO) contents, which further fuelled both denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This indicated that the SU dosage should be controlled to avoid DNRA over denitrification. Attention should be given to the fact that SU introduction significantly promoted the generation of an anaerobic state, leading to the desorption and release of Fe(OOH)~P, which could be alleviated by using Oxone. Multienzyme activity analysis showed that P and N transformation shifted from P desorption to organic P hydrolysis and from ammonification to denitrification and DNRA, respectively.

Conclusion

We recommend the use of P sorbent and organic C combined with oxidizing agents as effective mixed materials for sediment remediation, which could enhance P adsorption and provide electron donors for denitrification, while also avoiding the generation of anoxia.

中文翻译：

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底泥封顶技术中试氮磷联控机制及风险

 目的

氮（N）和磷（P）是导致富营养化的关键元素，共同控制沉积物向水体中氮和磷的释放非常重要。

 方法

在为期一年的中试规模实验中，采用了不同的混合材料，包括磷吸附剂、天然有机碳（C）和氧化剂。

 结果

富铁(IR)粘土和Phoslock剂的添加分别促进了沉积物中铁结合P(Fe(OOH)~P)和钙结合P(CaCO ₃ ~P)的形成。 IR粘土作为难熔P在固定磷方面具有更多优势，并且Phoslock剂更有效地降低了P释放到水中的风险，这表现为低平衡P浓度(EPC ₀ )。甘蔗（SU）碎屑和IR粘土的混合物表现出高碳水化合物（CHO）含量，这进一步促进了反硝化和异化硝酸盐还原为铵（DNRA）。这表明应控制SU投加量以避免DNRA过度反硝化。值得注意的是，SU的引入显着促进了厌氧状态的产生，导致Fe(OOH)~P的解吸和释放，这可以通过使用Oxone来缓解。多酶活性分析表明，P和N转化分别从磷解吸转向有机磷水解，从氨化转向反硝化和DNRA。

 结论

我们推荐使用P吸附剂和有机C与氧化剂结合作为沉积物修复的有效混合材料，这可以增强P吸附并为反硝化提供电子供体，同时也避免缺氧的产生。