Delivering a Resilient Approach to Tertiary Phosphorus Removal from Wastewater

污水处理厂出水排入淡水中所带来的环境风险已引起人们的关注。在这方面，随着《水框架指令》的实施，正在实施更严格的排放许可，低于1 mgP/L和低至0.1 mgP/L。在这种情况下，目前的方法，从废水中去除磷，特别是他们的能力，以满足非常低的同意正在审查，以便它可以实现在一个可持续的和经济的方式。投加金属盐，混凝，仍然是最有效的商业可用的方法，以消除磷，这些非常低的水平。然而，最近的事件也突出了凝结剂的有限可用性，并且与当前的政治局势相关，为了满足新的和更严格的同意，需要增加的化学品数量可能导致短缺以及成本的显著增加。因此，关键是要优化混凝过程，以去除废水中的磷到非常低的水平可持续。整个过程的效率直接受到絮凝物形成及其随后从水中分离的影响。最近的研究工作证明了水的特性（即固体，碱度）对该过程的显着影响，并强调了化学品选择，混合条件和絮凝分离器类型对处理性能的影响，但也强调了普遍缺乏关于废水中混凝的知识，以充分了解机制并优化所有类型条件的过程。特别强调了两个方面：（1）需要了解磷的形态如何影响混凝效果，以满足低磷标准去除浓缩磷酸盐和多聚磷酸盐。(2)絮凝过程的优化是絮凝体分布动态测量的最佳解决方案，并受到采样和运输的影响。预计要使出水磷浓度低至0.1mgP/L，分离步骤必须将悬浮固体去除至5 mg/L以下。因此，了解这些机制以确保为每种类型的分离器形成正确尺寸的沉淀聚集体并因此最大限度地降低总成本变得至关重要。因此，本项目的目的是开发一个混凝三级除磷的最佳实践指南。为了实现这一目标，该项目将实现以下目标：-确定废水特征（磷含量、硬度、碱度、竞争化合物、悬浮固体）对化学剂量、混合和分离要求的影响-研究和优化机械和水力混合配置以实现最佳的絮凝物形成，包括考虑改造操作-确定不同固液分离工艺的絮凝物尺寸发展和分离之间的联系，以使絮凝要求能够根据所使用的分离工艺进行定制。为混凝和TSR技术联合去除低水平磷提出最佳实践指南

The environmental risk associated with the discharge of phosphorus (P) from wastewater treatment plants effluent in freshwaters has been a cause for concern. In that regard,with the Water Framework Directive coming into place, stricter discharge consents below 1 mgP/L and as low as 0.1 mgP/L are being implemented. In this context, currentapproaches for phosphorus removal from wastewater effluents and, in particular, their ability to meet the very low consents are being reviewed so that it can be achieved in asustainable and economical way. The dosing of metal salts, coagulation, remains the most efficient commercially available process to remove phosphorus to these very lowlevels. However, recent events have also highlighted the limited availability of coagulants and associated to the current political situation, the increased amounts of chemical tobe required to meet new and stricter consents may lead to shortages as well as a significant increase in costs. It is then critical to optimise the coagulation-flocculation processin order to remove P from wastewater to very low levels sustainably. The efficiency of the overall process is directly affected by floc formation and their subsequent separationfrom the water. Recent research work demonstrated the significant impact water characteristics (i.e. solids, alkalinity) have on the process and emphasised the impact chemicalchoice, mixing conditions and type of floc separators have on treatment performance but also highlighted the general lack of knowledge available on coagulation in wastewaterto fully understand the mechanisms and optimise the process for all types of conditions. Two aspects are particularly highlighted: (1) the need to understand how the speciationof phosphorous impact coagulation efficacy as to meet low P standard removal of condensed and poly phosphates will be required. (2) Optimisation of the flocculationprocesses is best address with dynamic measurement of floc distributions and is impacted by sampling and transportation. It is expected that to meet effluent P concentrationsas low as 0.1 mgP/L the separation step will have to achieve suspended solids removal down to below 5 mg/L. It then becomes essential to understand these mechanisms toensure the right size precipitated aggregates are formed for each type of separator and hence minimise total costs. Consequently, the aim of the proposed project is to developa best practice guide of coagulation for tertiary phosphorus removal. To meet this aim, the project will address the following objectives:- Determine the impact of wastewater characteristics (phosphorus fractions, hardness, alkalinity, competing compounds, suspended solids) on chemical dose, mixingand separation requirements- Study and optimise mechanical and hydraulic mixing configurations for optimum floc formation including consideration for retrofit operations- Determine the connection between floc size development and separation for different solid-liquid separation processes to enable flocculation requirements to betailored to the separation processes used.- Propose a best practice guide for combined coagulation and TSR technologies for P removal to low levels