The plant provides secondary treatment of the wastewater by the following process:
- inlet works, including fine screening and grit removal
- secondary treatment through 2 Intermittently Decanted Aeration Lagoon (IDAL) units
- treated effluent is chlorinated for pathogen removal and then dechlorinated before discharge to the environment. (Note: this effluent will in future be used to supply the Kooragang Island Recycling Scheme.)
Sludge lagoons are used at the Shortland WWTW as there is space available and the lagoons are an affective and cost effective way to digest sludge created by processing.
The lagoons have a simple balance:
- sludge moves in
- supernatants move off
- the sludge layer at the base of the lagoon is pumped out and dewatered by contracted trucking units.
After storing the dredged and dewatered biosolids in onsite mounds for about a year the biosolids are reused in land rehabilitation and agricultural pasture improvement projects.