Optimisation of Phosphorus Removal in Stormwater Biofiltration Systems
(2010 – current)
High concentrations of phosphorus in stormwater pose a severe threat to the health of receiving waters. Phosphorus is a limiting nutrient which when present in excess concentrations can lead to the eutrophication of water bodies and the proliferation of cyanobacteria, the impact of which is extremely detrimental to aquatic life and water quality.
Field monitoring of existing biofiltration systems indicates that they effectively remove phosphorus from stormwater and suggests that biofilters can reliably meet load reduction targets. However, the same monitoring demonstrates that outflow pollutant concentrations are still in excess of the ANZECC guidelines.
The aim of this research is to develop a biofilter system design which facilitates effective, efficient and long–term phosphorus removal processes, without compromising the removal of other stormwater pollutants. The design specifications of an optimised system will synthesise quantitative data attained from a series of experimental investigations and a thorough understanding of the removal processes and complex interactions which occur within the biofilter environment, in particular between filter media, microbial communities and plants.
While the importance of biological processes for phosphorus removal by biofilters has been demonstrated, studies of treatment performance have been largely “black box” and our knowledge of the role of filter media in retaining phosphorus is limited and somewhat contradictory. In the natural environment, interactions between iron and phosphorus have been identified as important mechanisms for sequestering phosphorus in sediments. Investigating iron-phosphorus interactions in biofilter media is a key aspect of this research.
The experimental investigations undertaken as part of this research aim to answer the following questions:
- Does filter media play an important role in retention of phosphorus?
- Can we augment the phosphorus binding capacity of filter media in order to strongly (and possibly even permanently) bind phosphorus in the filter media?
- Can we utilise Fe-P interactions in biofilters to facilitate phosphorus removal?
- Can we improve the design of the saturated zone of biofilters in order to co-optimise nitrogen and phosphorus removal?
- How does phosphorus cycle within a biofilter and how do various processes (chemical, biological) contribute to removal over time?