Water and wastewater treatment provider ACWA Services’ nitrate removal system has helped Yorkshire Water combat rising nitrate levels, which had previously necessitated costly plant shutdowns.
Nitrate levels at the UK’s Yorkshire Water’s Tophill Low water treatment works, which supplies half of Hull’s daily drinking water, some 68 million liters, are now well within Drinking Water Inspectorate water quality limits, thanks to the ACWA nitrate removal system.
The £7.5 million ($11.5 million) drinking water improvement initiative, led by Amey, took 24 months to design and build and involved a complete water treatment system centered around ACWA’s Nitreat process, now in use across 25 sites in the UK.
Operational since July, the system enables Yorkshire Water to combat rising nitrate levels from the river Hull.
The ACWA Ion Exchange nitrate removal plant is designed to treat 22 million liters per day in the process reducing nitrates from a maximum of 64 mg per liter to 5 mg per liter. The treated water is then blended with the remaining drinking water flow to ensure that 68 million liters of water per day are within the target nitrate concentration of 44 mg per liter or below.
The new plant is installed downstream of the plant’s existing rapid gravity filters (RGFs) in a side stream arrangement and consists of two 50 percent duty Ion Exchange skids that can cope with large variations in flow and nitrate levels, configured to provide the best possible treatment at Tophill Low.
ACWA’s Nitreat Ion Exchange solution was selected following an extensive evaluation process as the best ‘total expenditure’ solution and one that was already tried and tested at the UK’s largest nitrate removal plant (90 million liters per day) also operated by Yorkshire Water at the Keldgate WTW.
The system also offered the added benefit of the smallest plant footprint. This is important given the existing site constraints and the proximity of an adjoining SSSI, together with the environmental advantages of the lowest wastewater flow of all the technologies considered.
Constructing the solution off-line made it possible to deal with many of the detailed design elements including process, mechanical, electrical and instrumentation works, and to minimize the impact on the nature reserve, the company says. It also meant that fewer shut downs and interruptions to the plant were required particularly those required when connecting to the existing RGF outlet pipework.