HEIGHAM WATER TREATMENT WORKS

PROJECT BACKGROUND

Heigham Water Treatment Works (WTW) supplies and average 42Ml/d of water to Norwich sourced from the River Wensum at several locations. In 2017, the stretch of the River Wensum between Costessey Pits and Hellesdon Meadow was designated as a Special Area of Conservation reducing water abstraction from this location.

Following a review of the available options, a plan to upgrade the existing clarification and filtration processes at Heigham WTW was adopted. 

PROJECT SOLUTION

The higher flow regieme at Heigham allows Anglian Water to take the water needed from the river without damaging the delicate ecosystem near Costessey.  Heigham Water Treatment Works had a number of specific challenges:

• Higher flow rates make the source water suseptable to significant peaks of algae and turbidity.

• The stringent feed water supply restrictions are matched by constraints to the size of the site.

To meet these challenges a wide range of possible options were evaluated by @one Alliance including roughing filters, pre-clarification and sand ballasted lamella clarification.

A submerged and reinforced, hollow fibre ultrafiltration membrane was selected as the optimum treatment solution.

PROJECT DELIVERY

Claret Civil Engineering were engaged, through their Framework with @one Alliance, to carry out the civil engineering element of what is now the largest Membrane Plant of its kind in Europe.

The scheme initially involved the extremely careful excavation of a multitude of cables and services which were serving the existing WTW and then installation of a new duct system for diversion to take place.

The scheme then progressed to the demolition of existing buildings, large excavations for the new building foundations, installation of CFA piles, installation of sheet pile retaining walls and the construction of numerous associated concrete structures.

A key element of the project was the installation of twin 1000mm diameter DI pipework into an area that already contained both existing and diverted services, along with the installation of numerous pumped and gravity mains, all involving considerable Temporary Works requirements.