Inorganic Nitrogen Removal

  • Biological filtration for nitrate removal from storm-water drainage is impaired by highly moveable mass loadings, which requires the need to adequately supply an electron donor, and potential inhibition by dissolved oxygen.
  • A very good way to optimize the nitrate removal is to introduce Expanded Clay aggregates (ECA®) as the filter medium, this contains a mixture of ion exchange and electron donor particles, and this enable the Expanded Clay Aggregate (ECA®)  to retain nitrate at high loadings and enable biological denitrification to be more efficient. 
  • An experiment was conducted (Bench scale filtration experiment) using a 50/50 volume mixture of Expanded Clay Aggregates (ECA®) and sulfur pastille. 
  • The result showed that Nitrate reduction was at 96% under a steady flow-rate operation at 25minutes normal time and 2.0mg∕L influent NO3–N. 
  • There was a step increase in flow-rate by factors of 4, 8, and 22 and this gave rise to a maximum effluent NO3–N of 0.80, 1.42, and 1.75mg∕L, respectively. 
  • Substantial nitrate absorption occurred even when effluent dissolved oxygen was close to zero. The results show how effectively Expanded Clay Aggregate (ECA®) is designed and operated as a filter media.