Council’s sewerage situation explained
Treated effluent (waste water) from the Rainbow Beach Sewage Treatment Plant is irrigated onto woodlands near to the plant. It is important to note; no effluent is discharged into waters.
Council’s licence to operate this plant is subject to a number of conditions. The region’s treatment plants are consistently monitored and any non-compliance reported has been reported to the regulator.
Indeed, the issues around the Rainbow Beach Sewerage Treatment Plant are in fact negligible and have been brought about by the level of salt in the treated waste water which leaves the plant.
The Rainbow Beach Sewerage Treatment Plant is designed to remove nitrogen and phosphorus from raw sewage. The treatment process cannot remove salinity (salt in water) hence whatever salinity enters the plant also leaves the plant on the other end of the treatment process.
It is the electrical conductivity reading which triggers the non-compliance (electrical conductivity is the ability of water to conduct an electrical current and dissolved salts are the conductors). Hence electrical conductivity and salinity are related.
Council believes the source of the salinity is groundwater infiltration into the sewerage network.
It is a similar situation with the Tin Can Bay Sewerage Treatment Plant. Both the Tin Can Bay and Rainbow Beach Sewerage Treatment Plant consistently meet all other licence conditions.
What we are doing about it
Gympie Regional Council has an ongoing issue with high electrical conductivity limits at a number of its sewage treatment plants.
Council is currently preparing a licence amendment application for submission to the regulator, the Department of Environment and Science, for the three coastal plants (Rainbow Beach, Cooloola Cove and Tin Can Bay).
This application includes a request to increase compliance limits specifically the electrical conductivity limits.
Further work will be undertaken in Rainbow Beach and Tin Can Bay to pinpoint and rectify likely sources of groundwater infiltration.
If successful, this may remove much of the salinity at its source.
