Vegetable grower Goni invests in a ‘NuReDrain MBBR filter system’
Since the start of the NuReDrain project in 2016, KU Leuven has been investigating the use of a denitrifying MBBR plant to address nitrate-rich water streams from agriculture. Their experience and expertise resulted in the development of a prototype and the realization of several field installations. The results can be consulted in a recent publication in Science of The Total Environment (Van Aken et al., 2022; ) Already before this publication, the first independent implementation by a horticultural company had become a reality.
Goni from Sint-Katelijne-Waver offers lettuce, cress, pak choi and cabbage lettuce of top quality and invests in innovative technology so that they can bring a sustainable product to market. The investment in an MBBR installation for the processing of their drain water fits perfectly into their business plan.
The plant consists of an above-ground buffer tank capable of collecting the daily volume of the discharged drain water and a downstream underground MBBR that is continuously fed (hydraulic retention time = 9.5h). The effluent of the MBBR is discharged into the nearby ditch. To achieve a good biological conversion of nitrate to nitrogen gas, the dosing of a molasses-based carbon source from Brenntag (CL60) is essential. Considering the maximum flow rate and the nitrate concentration, 6.1 L/day of CL60 is required to ensure the necessary COD/N ratio of 6 (= 5.2 €/day).
Start-up period
The MBBR plant was started up on 18 October 2021 and during the first 35 days, hardly any nitrate was removed from the drain water, i.e., approximately 30% removal efficiency. A start-up period of at least 3 weeks is necessary to allow the biofilm to grow on the plastic carriers. In this case, a low water temperature together with a rather low carbon source dosage resulted in a longer start-up period being required to achieve high removal efficiencies.
High efficiency
From mid-December, the nitrate removal efficiency increased to 75% to 94%, depending on the influent concentration. During this period, a reduction of approximately 100 mg NO3/L could always be maintained and clearly indicates the good performance of the denitrifying MBBR. Influent concentrations up to 150 mg NO3/L can therefore easily be reduced to below the standard of 50 mg NO3/L via the current carbon source dosage. If nitrate concentrations exceed 150 mg NO3/L, the carbon source dosing should be increased proportionally.
Reference
Van Aken, P., Lambert N. and Appels L. (2022). Low temperature Moving Bed Bioreactor denitrification as mitigation measure to reduce agricultural nitrate losses. Science of the Total Environment 810, 152110. https://doi.org/10.1016/j.scitotenv.2021.152110