Sth Lismore STP
Lismore City Council: South Lismore STP Ponds and Wetlands
The STP was built in the 1930s as a trickling filter system with tertiary ponds. Constructed wetlands were added in the early 1990s but design and operational problems led to compliance failures for suspended solids and phosphorus.
Challenges
- Increase in effluent flows
- Licence violations for suspended solids and phosphorus
- Wet weather flow management
Our role
- Design of constructed wetlands
- Construction supervision of constructed wetlands in partnership with Council
- Ongoing operational advice, management and reporting
Outcomes
- High and reliable performance
- Low cost sewage treatment
- Outperforming East Lismore BNR treatment plant
Our Solution
The pond and wetland system was re-designed in stages and managed for increased performance in a partnership with Council engineering staff and STP operators. Pond water levels were increased and wetland floors re-graded and planted, along with new inlet arrangements. A full redesign of the pond system is currently underway, and options for large-scale wetland expansion in concert with increased effluent reuse are under assessment.
Consistent performance at relatively low cost has been experienced, with good compliance not only with EPA licence conditions but also meeting modern technology requirements. Nitrogen, Suspended Solids and BOD5 outflow concentrations are reduced to low levels. A particular benefit is the low carbon footprint of the system, and the opportunity to postpone or save the high costs of a new steel-and-concrete plant.