The existing 35.0 mt x 13.2 mt timber frame tower structure at Rothes Sewage Works was in need of modification following removal of roof cladding and the open trough distribution system was very labour intensive and difficult to maintain. This resulted in uneven wetting of the Flocor modular media which in turn affected the quality of final effluent passing from the treatment works to the nearby river.

Sewaco Ltd was awarded the contract to remove the timber superstructure and open trough distribution channels and to install its HYCOVER distribution system, fitted with AUTOCLEANSE automatic nozzle cleansing equipment. Old timber trusses and troughing were removed and the upper section of the tower frame cleared of all unnecessary materials whilst still retaining the Flocor media. Modifications were made to stabilise the remaining framework before the exterior was re-clad. New media level walkways and pipework supports were installed on the cleared media surface ready to receive the new distribution pipework and nozzles. An elevated central walkway was installed to enable easy access to all parts of the system.

Maintenance of the new HYCOVER system is now a simple task. The AUTOCLEANSE pneumatic cleaning system ensures that nozzles are kept free from biomass build-up. Each lateral is fitted with a local isolating valve enabling the operative to service sections of the system without having to shut down the pumps. Each nozzle position is fitted with a 'Quickstrip' nozzle rodding cap to allow cleaning of the nozzle orifice in the event of solids build-up. Washout end caps are fitted to permit periodic flushing of pipelines. The overall result has been a 20% improvement in biofilter performance whilst operative attendance has been cut by over 80%.