Many people will be familiar with the Asset Management Period (AMP) framework which covers pricing, investment levels and water quality targets in the water and wastewater industry. Despite the fact that the current period – AMP 6 – is still in its early stages and will run until 2020, attention is already being paid to the next stage – AMP 7. With this in mind, one of the UK’s most prominent utility providers turned to Verder for assistance in planning for the future. “We had previously been involved with helping United Utilities with phosphate removal during AMP 5 so we were delighted when they asked us to help them prepare for AMP 7,” says Verder Project Manager, Philip Brown.

United Utilities and principal contractor Mott Macdonald Bentley’s (MMB) approach for help centered on a £1.3 million project to research into chemical dosing for phosphate removal – the process of mixing chemical additives into foul water, sewage or sludge which forms a critical part of the sewage treatment process. When effluent enters a treatment works it will contain material which must be cleaned, filtered and processed. This can be done by passing the effluent through filter beds and other processes, but this leaves what is, in essence, dirty water which must still be disposed of. This water can’t simply be discharged into rivers and watercourses where it would present a threat to fish and other forms of aquatic life, so chemical dosing is used to change its composition. This then allows the water to be returned to natural water courses without causing any damage to wildlife or the surrounding environment.

“The Environment Agency sets ‘milligrams per litre’ consent limits for the phosphate levels contained in water which is being discharged into streams and rivers,” explains Philip Brown.” To meet these levels, utility providers like United Utilities must dose certain chemicals to remove impurities like phosphates. Phosphates can cause the growth of algae which limits the levels of oxygen in the water and creates a threat to the wildlife in the river. Iron-based chemicals such as ferric chloride and ferric sulphate are dosed into the sewage to remove these phosphate levels. Dosing these chemicals also changes the pH level of the water and so sodium hydroxide or hydrated lime are then dosed in to restore the pH levels to meet consent level requirements.”

Even though AMP 7 is still several years away, United Utilities and MMB had been approached by the Environment Agency to help investigate the new consent levels which the new standard might eventually include. United Utilities provides water and sewerage services to some seven million people in the North West of England, so in addition to working with the Environment Agency, the company also needed to be fully confident that it will be able to meet any future consent limits. Although any new targets will need to be thoroughly researched to make sure that they are practicable, they are highly likely to be lower than those for AMP 6. This prompted United Utilities to ask for Verder’s assistance in identifying the type