Scottish Water has invested £8.7 million in an aerated wetland scheme at Cowdenbeath 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 being discharged 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 AerationTM (FBATM).

 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 FBATM technology, it only needs to be switched-on during storm events when flow increases therefore optimising energy usage.

Scottish Water is investing in its combined sewer overflows so it can continue to meet stringent discharge consents. An increasing need to meet consents of 9.0 mg/l BOD limit and an ammonia-nitrogen limit of 1.5 mg/l lead to the conclusion that an aerated system which increased oxygen availability was the right choice.

Tori Sellers, director of ARM commented:

 “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 FBATM 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 FBATM 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.

Eddie Burns, project manager at Scottish Water commented:

“The CSOs around Cowdenbeath needed to be upgraded and as we are committed to the local environment, a natural wastewater treatment system provided the best solution.”

“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. Another upside is that it creates a wildlife habitat for birds as well as insects, newts and other amphibious organisms.

 “The wetland ARM has designed is both cost-effective and in-line with how we want to treat wastewater in the future. It requires little maintenance, saving costs year-on-year which will benefit everyone.”

 The work at Cowdenbeath’s Waste Water Treatment Works took approximately 15 weeks to complete.