Ammonium removal from digested sludge liquors using ion exchange

摘要

Liquors arising from the dewatering of digested sludge typically contain ammonium levels in the range 200-700 mgl~(-1) NH_4~+-N. These liquors are frequently recycled to the head of the wastewater treatment works (WwTW) untreated and can constitute > 25% of the total nitrogen load entering the works at inlet. This paper investigates the use of a clay-based material, MesoLite, as an ion exchange medium for ammonium removal from recycle streams. Pilot-scale studies performed at Didcot WwTW, part of the Thames Water wastewater treatment network, indicate that MesoLite is highly selective for the ammonium ion. Results show that > 95% of ammonium was removed from belt press liquors with an initial ammonium nitrogen concentration > 600 mgl~(-1), with an overall ion exchange capacity > 51 g NH_4~+-N kg~(-1) medium and this resulted in an operating capacity in the range 27-36 gNH_4~+-Nkg~(-1).