To protect the UK’s rivers and lakes, tough new phosphorus limits have been set, but how can these be achieved without going chemical crazy? More flocculant chemicals are simply NOT the answer – so what’s the alternative?
The arrival of AMP8 marks a significant milestone for the UK water industry. This Asset Management Period carries unprecedented demands, a heavy price tag and a complex set of challenges and opportunities.
And with less than twelve months to go, the pressures are increasing on water companies to deal with high profile problems including sewer overflow discharges, flooding from antiquated sewer systems and water supply leakage.
Equally contentious is nutrient neutrality. This includes addressing phosphorus pollution. Phosphorus is an indispensable nutrient, and in correct amounts, needed to sustain life. However, excess phosphorus from WwTW discharge can lead to eutrophication and harmful algal blooms that degrade water quality.
As a result, a large number of works will need to achieve phosphorus limits as low as 0.25mg/l during AMP8. With potentially even lower limits for areas for Sites of Special Scientific Interest (SSSIs).
Achieving these levels isn’t an easy task. Ferric salts are commonly used to precipitate out phosphorus from wastewater, but throwing flocculant chemicals at the problem isn’t the solution.
Reducing reliance on flocculant chemicals
Ferric creates several issues. It’s highly corrosive and wreaks havoc with tanks and pipes, and therefore must be neutralised, bringing its own set of problems.
Chemical precipitation also significantly increases sludge volumes, which necessitates tertiary treatment of the precipitates generated – adding unwanted additional costs to the process. Huge ferric price fluctuations, quality and supply chain reliability issues must also be considered.
Enhanced biological phosphorus removal
The solution is to harness biological phosphorus removal. Creating conditions that promote the growth of beneficial microorganisms that naturally consume phosphorus as a nutrient source.
Biological methods can do the bulk of the work, and therefore minimise chemical usage, and avoiding any increased sludge generation, and additional operational costs.
The process works using a single-stage batch setup, which allows for continuous flow and eliminates the need for buffer tanks upstream or downstream. This reduces the overall site footprint as well as removing the need for mechanical mixing, therefore reducing energy costs – offering efficiency and sustainability, with fewer chemicals.
Case Study: SOUTHERN WATER – Hawkhurst WTW
Southern Water’s Hawkhurst South works, situated near the Kent High Weald National Landscape, serves a population of about 2000 PE, and this number is estimated to rise by 15% by 2030.
The aging biological trickling filters were not able to meet new ammonia and total phosphorus discharge permit limits demanded by the Water Industry National Environment Programme (WINEP).
Te-cycTM advanced cyclic activated sludge technology was selected and allows Hawkhurst to successfully achieve tight consent limits.
The technology has several benefits over conventional SBR design:
- Smaller tank volume and footprint
- Bespoke design of anaerobic selector forms larger macroflocs with improved settling velocity
- Larger macroflocs allows for simultaneous nitrification and denitrification (therefore anoxic tanks with mechanical mixers are not required)
- The anaerobic selector promotes growth of polyphosphate accumulation organisms (PAOs) within the macrofloc which provide an enhanced level of biological phosphorus removal and reduces ferric requirements.
Te-cyc satisfies multiple drivers simultaneously, and combined with the benefits listed above means that the process provides a lower whole life cost when compared to a conventional upgrade solution.
The cost savings are attributed to reduced infrastructure and space requirements. Without the need for anoxic or buffer tanks, the site footprint is reduced, and this meant Southern Water did not need to acquire any additional land. Moreover, chemical costs were reduced due to less ferric and alkalinity dosing required.
The project was completed and handed over in December 2023.
Be ready for AMP8
As the water industry prepares for AMP8, te-cyc technology, by Te-Tech Process Solutions, offers a reliable and cost-effective solution to reach ultra-low phosphorus levels.
For more information, contact: enquiries@te-tech.co.uk
Full article can be found in Water Industry Journal