Process & contact
HAIX ion exchange (LayneRTTM)
Secondary treated sewage (discharge after biological treatment)
Orthophosphate solution from which calcium phosphate is precipitated by adding lime
Selective ion exchange using HAIX (hybrid ion exchange) of hydrated ferric nanoparticles in a strong base anion (quaternary ammonium) resin, using a LayneRT resin base (this is a commercially available arsenic removal resin).
Sodium hydroxide is used to release P from the HAIX iron sites, so generating orthophosphate solution, plus water washing to regenerate the resin.
10 m3/day (58 litres, 1.6m high column) demonstration plant operated continuously for 2 ½ years (60 regeneration cycles), with automated bed regeneration, using real WWTP secondary effluent, Cranfield, UK, 2019 -2021.
Inflow 0.7 mgPtotal/l was reduced to below 0.1 mgPPO4+/l.