Aerated wetland investment in Fife

The wetland scheme will treat the spill flows from a couple of combined sewer overflows.

SCOTTISH Water’s commitment to deliver a cleaner and fresher environment, and improve the local watercourses across Cowdenbeath, has taken one step further following its investment in a treatment wetland to improve its combined sewer network.

The water company has been working with reed bed specialists ARM Limited and Barhale Construction since September 2013 to design and construct a wetland scheme which will treat the spill flows from two Combined Sewer Overflows (CSOs) for attenuation and treatment before discharge into the Lochgelly Burn.
Located to the south of Cowdenbeath Golf Course, the £8.7million project involved the construction of two units; the first a flow-balancing shaft-settlement system for sedimentation of solids, and the second a 4,000m2, two-metre-deep saturated, vertical flow aerated wetland fitted with Forced Bed Aeration (FBA).
The new two-unit system has a 20,000m3 storage unit downstream with a controlled, pumped inflow rate to the wetland of 46l/second. The system will provide sufficient treatment to allow storm waters to flow back into the watercourses without compromising water quality.
Although the wetland is fitted with FBA technology, it only needs to be switched-on during storm events when flow increases therefore optimising energy usage.
“Scottish Water is committed to investing in its combined sewer overflows so it can continue to meet stringent discharge consents,” said Tori Sellers, director of ARM.
“The effluent quality from storm water is variable but all of it needs to be treated before re-entering the watercourse. A wetland system fitted with FBA is ideal and is fast becoming a more popular alternative method of water treatment due to its low footprint requirement, sustainability, habitat creation and versatility.
“By investing in a two-unit system, Scottish Water can reduce energy further by only using the FBA element during storm events. Now complete, it can treat approximately 230,000m3 of water per annum which means it has one of the largest treatment capacities in the UK.”
Scottish Water treats the wastewater from around 11,000 customers in Cowdenbeath. In 2011 the water company completed the first phase of its plans to improve the quality of water it provides across the region. With an increasing need to meet consents of 9.0 mg/l BOD limit and an ammonia-nitrogen limit of 1.5 mg/l an aerated system which increased oxygen availability was deemed the right choice.
“The new system will provide sufficient treatment to reach a standard where it meets SEPA requirements for us to pass the flows into the Lochgelly Burn”, said Eddie Burns, project manager at Scottish Water. “Another upside is that it creates a wildlife habitat for birds as well as insects, newts and other amphibious organisms.”