Testing different filter materials for phosphorus removal at PCS

19 December 2022 - Published by Charlotte Boeckaert
PCS Ornamental Plant research has conducted field tests on P removal since 2017. Their latest results give interesting insights in the lifespan and circular use of iron coated sand. Two filter materials from VITO based on iron oxide and aluminum oxide were also tested in horticultural drain water.

Iron Coated Sand saturated

For the removal of phosphorus from wastewater in horticulture, PCS tests 2 filter materials since 2017: ICS (Iron Coated Sand) granules and pellets of iron sludge. Both materials are by-products of drinking water companies.

Two IBC containers are filled with 80% of this material. The water runs from bottom to top through the filter. Phosphorus is removed by binding to the iron oxide in the filter material and each filter processes an average of 0.8 m³ of drain water per day. When there is no more iron oxide available on the materials to bind with the phosphorus, grains are saturated and need to be replaced. During the 4th year, analyses showed that P was less efficiently removed. Therefore, the ICS granules were replaced in the winter of 2021-2022. The 'fresh' ICS granules resulted in a good P removal again. The pellets were also saturated, but they could not be replaced since this material is no longer available.

Figure 1 (below) gives an overview of the P removal results between 2017 and 2022. From June 2020 onwards granules and pellets become saturated. When not saturated, there is a perfect P removal:



Figure 1: Overview of the P removal results between 2017 and 2022. From June 2020 onwards granules and pellets become saturated. When not saturated, there is a perfect P removal.


New filter materials for P removal

Since 2021, PCS tested 2 new P-removal materials produced by the project partner VITO. One of the materials is based on iron oxide and the other on aluminum oxide. In 2021 and 2022, both materials proved to be very efficient and removed more than 95% phosphorus (Figure 2).


Figure 2: P-removal results with aluminum-based (VITO A) and iron-based (VITO B) filter material at PCS


The use of ICS, saturated in arable fields for drain water filtration

Ghent University uses ICS granules to remove phosphorus from drainage water of agricultural fields. P levels in drainage water from tile-drains are rather low and P has time over summer to migrate to the core of the sand grain. However, after 3 years of operation, P-removal efficiency drops to below 50% so replacement of the filter materials needs to be considered. Last summer, it was investigated whether these ‘for tile-drain saturated’ granules can still be used to treat the drain water of ornamental plants, where P levels are 10-fold higher than in drainage water. Therefore, a 70 l filter was filled with 50 l of ICS granules and processed 50 l per day. The filter gave good results in the so far first 4 months of the trial setup (Figure 3).


Figure 3: Results of the P filters at PCS with ICS granules from UGent