TWS was awarded the contract for the Construction of Bodalla Sewerage Treatment Plant (STP). The Project commenced in February 2017 with expected completion date early 2018. TWS has also been awarded the Bodalla Pressure Sewerage Scheme (PSS) contract which is running concurrently with the STP project.
The Bodalla STP is an intermittent discharging extended aeration (IDEA) biological process, modified to include a preselector anoxic zone. The biological process includes nitrification / denitrification and chemical phosphorus removal. Preliminary treatment is provided at the inlet works and disinfection is provided after the IDEA using UV and chlorination. In addition, the plant includes biosolids processing and storage, chemical dosing systems, a control building and site services.
The STP inflows are in two stages:
Stage 1 design is for an equivalent population (EP) of 550, with an adopted average dry weather flow (ADWF) of 104 kL/day
Stage 2 is designed to receive an additional 270 EP plus holiday loadings, with an adopted total ADWF of 208 kL/d. The second IDEA tank / stage 2 process works.
The plant is designed to treat up to 3 times the ADWF. Excess influent flow is diverted to a balance tank at the inlet works, and then to foul water pumping station, with stored flows returned to the inlet works for full treatment after the high inflow has subsided.
Effluent will be adequately treated at the Bodalla STP to comply with the Australian Guidelines for Water Recycling (AGWR) for disposal via irrigation. Irrigation effluent will be stored in an onsite effluent storage pond (ESP) prior to disposal.
Effluent flows in periods of above average rainfall which are in excess of irrigation demand will be discharged via an environmental discharge stream to Borang Creek. Effluent discharged to Borang Creek will have additional chlorine disinfection to meet the requirements of the NSW Food Safety Authority (FSA) in protecting oyster farm leases downstream of Borang Creek and will be dechlorinated prior to release to have no chlorine residual.
The plant has been designed with two biological process trains for complete redundancy / standby.