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Phased upgrading for nitrogen removal--a low cost approach.
1Brisbane Water, GPO Box 1434, Brisbane, Australia 4001. ep5psbw@brisbane.qld.gov.au
Summary
Upgrading Luggage Point Wastewater Treatment Plant using a phased Bardenpho process significantly reduced total nitrogen effluent levels. This cost-effective strategy achieved substantial nitrogen removal, protecting local waterways.
Area of Science:
- Environmental Engineering
- Wastewater Treatment Technologies
- Nitrogen Removal Processes
Background:
- Luggage Point Wastewater Treatment Plant (WWTP), serving 900,000 EP, faced challenges meeting stringent effluent total nitrogen limits (<5 mg/L) mandated by the South East Queensland Wastewater Management Strategy.
- The original plant design, featuring primary settling and a nitrifying activated sludge process, resulted in high average effluent total nitrogen levels of 27 mg/L.
- Wastewater characteristics, including high COD/BOD5 ratio, TKN/COD ratio, and variable non-ammonia TKN, coupled with limited substrate for denitrification and low bioreactor HRT, posed significant upgrade challenges.
Purpose of the Study:
- To detail a phased approach for upgrading the Luggage Point WWTP to achieve effective nitrogen removal.
- To demonstrate a cost-effective solution for reducing effluent total nitrogen levels by optimizing existing infrastructure.
- To meet regulatory requirements for reduced nitrogen discharge into Moreton Bay.
Main Methods:
- Implementation of a phased upgrade strategy, focusing on retrofitting existing bioreactors without new tankage construction.
- Adoption of a five-stage Bardenpho nutrient removal process with integrated flexibility.
- Commissioning of the first phase of the upgrade to assess performance and stability.
Main Results:
- Preliminary results show effluent total nitrogen reduced below the first phase target of 8 mg/L, achieving a daily reduction of 3 tonnes of nitrogen entering Moreton Bay.
- The upgraded process demonstrated good operational stability and excellent sludge settleability.
- The first phase upgrade was completed at a low cost of 25 million AUS dollars, equating to $28 per equivalent person.
Conclusions:
- A phased approach and optimal utilization of existing assets can achieve low effluent nitrogen levels cost-effectively.
- The retrofitted five-stage Bardenpho process is a viable and economical solution for nitrogen removal in large-scale wastewater treatment plants.
- Further enhancements, including centrate treatment and advanced process control, are planned for continued optimization.