Promising test results for the regeneration of filter materials for phosphorus removal

19 December 2022 - Published by Charlotte Boeckaert
The successful regeneration of filter materials after saturation is an important aspect for a sustainable use of phosphorus removal filters. VITO’s treatment tests to desorb the loaded filter materials show good results and the regenerated iron coated sands perform well in a second life at a horticultural company.

VITO focusses on the circularity of iron coated sand filter materials. The aim is to desorb P-loaded filter materials to enable reuse of the filter material. 

VITO received 500 kg of P-loaded ICS grains from the treatment of greenhouse drain water at PCS and at the horticultural business Meuninck. The goal was to investigate the desorption of phosphorus from the loaded ICS grains. In an optimized column set-up, around 11 g of P was removed per kg of sorbent, which corresponds with almost the complete amount of sorbed phosphorus on the grains.

The loaded ICS grains were treated with an alkaline NaOH solution (pH = 12.5) in a column set-up. Before reuse as a sorbent, the ICS grains were washed and their pH was decreased using a moderate acidic solution. The first test results at Meuninck showed that the regenerated ICS grains could be used again for the removal of phosphorus.

Preliminary tests have shown that the regeneration can also be performed with the use of a potassium hydroxide (KOH) solution. KOH is more expensive than NaOH but using KOH would result in an alkaline solution with K, P, Ca and trace solutions of Fe and Zn. This solution could be used in horticulture.

If the filter set-up for phosphorus sorption is made from materials that can withstand strong alkaline solutions (e.g. PP, PTFE, HDPE, FKM), the regeneration of the ICS grains can be performed in the same set-up as the phosphorus filter set-up.

undefined Figure above: the regenerated ICS grains



Figure above: The desorption column set-up


50 euro per ton

Chemical costs for the regeneration of 1 ton of P-loaded ICS grains are estimated at ±€50/ton. The regeneration technology is transferable to other iron (hydr)oxide based sorbents.

VITO is currently performing an automated desorption and washing process (both steps are automated on pH of the solution) on the loaded ICS grains. Afterwards, the data will be gathered to perform a more thorough tecno-economical assessment.