Hydro International have completed major design and build upgrade works in the Arrabawn Nenagh WwTP site over two project phases. 

Phase 1 upgrade included a full control and automation installation and also included the installation of a new Primary Dissolved Air Flotation (DAF) system, Anoxic Tank, Tertiary DAF and Tertiary Drum Filter to reduce suspended solids in the discharge. In addition the existing aeration system was supplemented with a fine bubble diffused aeration (FBDA) lift out grid to optimise oxygen transfer.

Phase 2 provided for a major load and capacity upgrade at the WWTP to accommodate a facility expansion. Upstream 2 stage flow and load balancing tanks were provided in addition to a divert tank to cater for shock loadings as identified by on-line TOC, COD and pH monitoring on the two influent waste streams.

Additional Primary and Tertiary DAF systems were provided to cater for expanded plant capacity. A unique two stage biological process was adopted to cater for high COD / BOD loading rates from the dairy waste and ensure a robust treatment process to meet stringent final effluent standards. This involved the construction of an additional aeration tank and final clarifier as well as FBDA upgrades to the existing aeration tank.

The sludge dewatering facilities were also upgraded to provide additional capacity with the provision of a Picket Fence Thickener (PFT) and a sludge dewatering building extension complete with an additional dewatering centrifuge. The scope of works included all ancillary civil works, control and automation including the construction of a new dedicated blower / control building. All works were completed while keeping the existing plant in operation and meeting discharge consents.