Optimising saline biofilter performance through plant selection

FUNDING SOURCE: City of Melbourne, Melbourne Water (2013-2014)

RESEARCHERS: Chris Szota, Tim Fletcher and Stephen Livesley

OVERVIEW: Experimentally assessing the effect of saline stormwater on biofilter performance with a range of current and alternative plant species

WSUD DocklandsStormwater biofilters in coastal cities can often suffer from saline stormwater input which has the potential to significantly reduce biofilter performance.  Current biofilter plant species are likely to be sensitive to the enhanced water stress, will use less water and will intercept less nitrogen (N) and phosphorus (P).  This project will address two key questions: 1) will application of saline stormwater reduce the capacity of the filter media and/or vegetation to improve water quality?  2) which species will best tolerate saline stormwater and the likely levels of salt accumulation?

Plant species commonly used in biofilters, e.g. Carex appressa or Lomandra longifolia will act as ‘little or no salt tolerance’ references from which to determine the performance of more tolerant halophytes and salt-tolerant non-halophytes.  Halophytes are species which achieve optimum growth rates only under saline conditions; whereas salt-tolerant non-halophytes have adaptations which facilitate maximum growth under mild-moderate levels of salinity.  We are assessing the response of a range of salt-tolerators to increasing levels of salinity to determine critical thresholds beyond which biofilter performance is significantly reduced.