Growers testing 2-in-1 filters for phosphorus and nitrogen removal

03 May 2023 - Published by Charlotte Boeckaert
PCS Ornamental Plant Research has been conducting tests with combined filter systems that remove both phosphorus and nitrogen from greenhouse effluent. An overview of their latest field test results.

Floristry Meuninck in Nevele

Since 2020 a nitrogen (N) and phosphorus (P) removal filter system is installed at Floristry Goderick Meuninck in Nevele. Initially, the water flew from the water silo first through the MBBR (N removal) and secondly through 2 phosphor filters but, due to clogging problems, it was decided to reverse the order. This clogging was probably due to a biofilm developed in the MBBR and disturbing the P filters. Last winter, the system was modified and now water flows through the 2 phosphor filters first and then through the MBBR. Carbo-ST is added as carbon source to the MBBR and the system is aerated every hour during 1 minute to prevent clogging. Daily, the filters process 3 m³.


2-in-1 Do-it-yourself filter system at Bloemisterij Meuninck


The adaptations to the 2-in-1 do-it-yourself filter system at Meuninck gave good nutrient removal results.

In graph 1, a nearly 100% P removal is illustrated. This is the results of no clogging issues and the replacement of saturated ICS grains by new unsaturated grains in spring 2022. Cold temperatures do not affect the P removal since the removal is based on a physical adsorption process and not a bacteriological process as is the case in the MBBR.



Graph 1: P Concentrations before and after P filter and MBBR at Meuninck in 2022


Graph 2 shows that one month after startup (July) the efficacy of the MBBR was very high and maintained high until October. In December there was no removal anymore due to the cold temperatures. We assume that a minimum temperature of 10-12°C is needed to guarantee the bacteriological denitrification


Graph 2: N-NO3 - before and after P-filter and after MBBR at Meuninck in 2022


VDS Plant in Lochristi

In July 2022, another 2-in-1 do-it-yourself filter system was installed at VDS Plant, a grower of azalea and Rhododendron-plants. One IBC is filled with new ICS grains for P removal; another IBC is the Moving Bed Bioreactor (MBBR) responsible for N removal (Photo 2). Carbo-ST is added to the MBBR as carbon source and the system is aerated every hour to prevent clogging. The 2-in-1 filter treats the wastewater from an azalea greenhouse. The wastewater is collected in an underground cittern, flows from bottom to top through the P-filter and subsequently by natural gravitation to the MBBR. Daily, the filters process 1,5 m³.




The 2-in-1 filter system at VDS Plant showed a good performance from the start (Graph 3 and 4). P removal was above 95% until October. N removal was high at the beginning of the season but decreased in October. This was probably due to a too short retention time. After adapting to a longer retention time, results improved again, but still, a good N removal efficiency can only be obtained when the water to be treated has sufficient high temperatures.


Graph 3: P concentrations before and after both filters at VDS Plant in 2022



Graph 4: N-NO3 -conc before and after both filters at VDS Plant in 2022