Delivering a Resilient Approach to Tertiary Phosphorus Removal from Wastewater

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, current
approaches 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 a
sustainable and economical way. The dosing of metal salts, coagulation, remains the most efficient commercially available process to remove phosphorus to these very low
levels. However, recent events have also highlighted the limited availability of coagulants and associated to the current political situation, the increased amounts of chemical to
be 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 process
in 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 separation
from the water. Recent research work demonstrated the significant impact water characteristics (i.e. solids, alkalinity) have on the process and emphasised the impact chemical
choice, mixing conditions and type of floc separators have on treatment performance but also highlighted the general lack of knowledge available on coagulation in wastewater
to 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 speciation
of phosphorous impact coagulation efficacy as to meet low P standard removal of condensed and poly phosphates will be required. (2) Optimisation of the flocculation
processes is best address with dynamic measurement of floc distributions and is impacted by sampling and transportation. It is expected that to meet effluent P concentrations
as 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 to
ensure 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 develop
a 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, mixing
and 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 be
tailored to the separation processes used.
- Propose a best practice guide for combined coagulation and TSR technologies for P removal to low levels

Graduates from the WRIC programme will produce new knowledge across the disciplinary landscape and graduate to occupy professional roles of influence and authority which require a thorough understanding of the pathways by which knowledge and technology are adopted and put to socially significant use. The people and knowledge delivered through the CDT will improve the efficiency and effectiveness of the nation's >£5bn annual spend on water and water related infrastructure (OFWAT, 2017), improving its resilience and securing its value for society for generations to come. With ambitions to nurture domain experts who can flourish at the interfaces of scientific disciplines and economic/industry sectors, the impact imperative is a significant but stimulating challenge for the WRIC CDT. Our impact strategy seeks to; (i) ensure rapid dissemination of scientific insights, (ii) maximise awareness and uptake of research sponsored through the CDT, and (iii) improve professional and lay understandings of the water infrastructure challenges facing society and the science behind candidate solutions. This strategy has been developed with project and Centre stakeholders so as to leverage additional resources, and maximise impact.
Improving the resilience of water infrastructure systems will be of benefit to a wide range of stakeholders. Given the CDT's bold intention to tackle knowledge gaps at the interfaces between disciplines and problems, new scientific understandings generated through WRIC will be of value to the knowledge users in the public sector (local authorities, regulators) and private sector (utilities, consultancies, technology providers), ultimately benefiting both lives and livelihoods across the UK and beyond. The UK economy will benefit from robust and resilient water infrastructure, in-line with the UK Government's Industrial Strategy for cleaner economic growth, the efficient use of resources, and building a regenerative circular economy. In the next Price Review PR19 (2020-25), water companies will be financially rewarded for implementing enhanced system resilience and innovation. Research outputs from WRIC will enable water companies to be able to meet these demands, alongside ambitious industry targets for zero water and wastewater quality failures, demand reduction and chemical recycling (OFWAT, 2017; UKWIR, 2017). These developments will facilitate inward international investment, development of new technology providers and supply chains, and opportunities for exporting intellectual property and know-how worldwide, further benefiting the UK economy. Project partners, including Thames Water, Severn Trent Water, Atkins, Stantec, Datatecnics also benefit from access to high quality graduates and facilities. Furthermore, regulatory agencies (Environment Agency, Drinking Water Inspectorate) and the European Commission will see benefits from improved compliance to regulations and sustainability agendas (Water Framework Directive 2008/32/EC and Drinking Water Directive 2017/0332(COD)).
The CDT programme will benefit the UK Collaboratorium for Research on Infrastructure and Cities (UKCRIC) government investments (£138M). Sheffield, Cranfield and Newcastle Universities have all received capital grants through UKCRIC to fund industrial scale test facility and observatory facilities to form an Urban Water Hub. The CDT will supply the resources to use and maximise the benefits and outputs from these facilities. Cooperation with other UKCRIC CDTs will help students better understand contemporary challenges for infrastructure and cities will catalyse horizontal innovation transfer and elevate the transformative potential of WRIC graduates.