Aamand, Jens

Albers, Christian Nyrop

Buhl, Torben

Ellegaard-Jensen, Lea

Hansen, Lars Hestbjerg

Hylling, Ole

Koch, Arne

Madsen, Henrik Tækker

Muff, Jens

Nikbakht Fini, Mahdi

Nilsson, Iben Kirchberg

Nissen, Steen Søndergaard

Schostag, Morten Dencher

Silkjær, Ole

English

Combined membrane filtration and biodegradation – a novel hybrid concept targeting BAM removal in drinking water productionO Hylling1, M Nikbakht Fini2, L Ellegaard-Jensen1, L Hestbjerg Hansen3, HT Madsen2,4, J Aamand5, MD Schostag5, CN Albers5, SS Nissen6, AC Koch7, T Buhl7, IK Nilsson8, O Silkjær9, J Muff2*, 1Aarhus University, Dept. Environmental Science, Section for Environmental Microbiology & Biotechnology, Roskilde, Denmark2Aalborg University, Dept. of Chemistry and Bioscience, Section of Chemical Engineering, Aalborg University, Esbjerg, Denmark3University of Copenhagen, Dept. of Plant- and Environmental Sciences, Section for Microbial Ecology and Biotechnology, Frederiksberg, Denmark4SaltpowerTM Aps, Alsion 2, DK-6400 Sønderborg, Denmark5Geological Survey of Denmark & Greenland (GEUS), Dept. of Geochemistry, Copenhagen, Denmark6Applied Biomimetics A/S, Nordborg, Denmark7Silhorko-Eurowater A/S, Skanderborg, Denmark 8DIN Forsyning, Esbjerg, Denmark9TREFOR Water, Kolding, Denmark*coresponding author: jm@bio.aau.dk Abstract: A new groundwater based drinking water production concept targeting the pesticide residue 2,6-dichlorobenzamide (BAM) is introduced. The treatment process is a combined membrane filtration and biodegradation of the retentate that is used for re-mineralization of the purified water. Lab scale studies show an improved BAM degradation by the BAM degrading bacterium Aminobacter MSH1 in membrane retentate. Preliminary pilot scale tests showed complete degradation, but only for 3-4 days and based on an extensive evaluation of the chemical and molecular analysis from the pilot test further lab and pilot scale tests are planned.   Keywords: Biodegradation, membrane filtration; groundwater treatmentSDGs addressed: 6 (6.3, 6.6), 9 (9.5), 12 (12.2, 12.4)Groundwater extracted for drinking water production is commonly treated by aeration and sand filtration. However, this simple treatment is typically unable to remove pesticide residues. As a solution, bioaugmentation of sand filter units (i.e., the addition of specific degrader strains) has been proposed as a “green” technology for targeted pesticide removal. However, the introduced degraders are challenged by (i) micropollutant concentration levels of target residue, (ii) the oligotrophic environment and (iii) competition and predation by the native microorganisms, leading to loss of population and degradation potential. To overcome these challenges, a novel hybrid treatment process is developed in the MEM2BIO project in which membrane filtration and biodegradation are combined to remove a target micropollutant. Here, the membrane filtration produces a concentrated retentate that will act as a feed to a dedicated biofilter unit, intended to promote biodegradation and stability of an introduced degrader. Subsequently, the purified retentate will be re-mixed with the permeate from the membrane filtration, for re-mineralization and downstream consumption. The pesticide residue 2,6-dichlorobenzamide (BAM), a highly persistent metabolite of the once widely used herbicide dichlobenil (2,6-dichlorobenzonitrile), is a common micropollutant found in groundwater in several countries, often exceeding the 0.1 µg L-1 EU threshold limit for pesticides. The use of Aminobacter sp. MSH1 has been investigated as a potential bioaugmentation candidate for remediating groundwater polluted by BAM. MSH1 has therefore been a model organism in studies concerning bioaugmentation and BAM removal, but suffers due to the reasons mentioned above. Alternatively, reverse osmosis (RO) membranes have been proven to be capable of retaining organic micropollutants including BAM in drinking-water resources (Nikbakht Fini, 2019). In this paper, lab and pilot scale results of BAM removal is presented using the MEM2BIO hybrid concept based on reverse osmosis (RO) membrane filtration and bioaugmentation of a sandfilter with MSH1 BAM degrader for retentate treatment. Lab scale batch experiments provided evidence of improved degradation when combining bioaugmentation with retentates from membrane filtration (Hylling et al. 2019). The effect of RO retentates on the degradation of BAM by an introduced BAM degrader was investigated and the results showed an increased degradation in retentate waters versus untreated water (Figure 1.1). Colony-forming units and qPCR showed a stable MSH1 population, despite the presence of higher concentrations of salts and metals, but also increased growth of native bacteria. In lab scale column experiments, degradation was maintained for 40 days and prolonged to 60 days with an improved innoculation strategy (Figure 1.2). Field pilot scale testing was planned on a BAM contaminated groundwater abstraction well using a dual line treatment process with or without RO membrane in front of the MSH1 biofilter (Figure 1.3). Pretreatment with aeration and sandfiltration is used for iron and manganese removal and ion exchange is used for decreasing the water hardness. Tests are still ongoing and only preliminary data is available. Results so far shows that BAM is initially efficiently removed (>90%) in both filters, but the removal declines rapidly after 5 days in both biofilters. The RO membrane performs as expected and provides an approx. x10 concentration of BAM in Biofilter 1, but the effect in terms of prolonged BAM removal is not seen as compared to Biofilter 2. A wide range of chemical and molecular analyses is used to evaluate the causes of the loss of degradation efficiency and further laboratory studies are initiated to assess the impact of potential factors of influence in parallel to planning the next pilot scale test events.In conclusion, lab scale batch experiments support the hypothesis that membrane filtration can be used to improve the subsequent MSH1 biodegradation of BAM in a sandfilter. However, preliminary pilot scale data are not at current state in the project supportive and suggests that upscaling still needs optimization before this technology can be implemented. The RO retentate composition do not inhibit biodegradation either, which makes it possible to treat up to 10 times less water in the biofilter. The pilot scale test facility provides a unique opportunity to test this technology further and parallel lab scale studies are initiated to investigate selected factors that can crack the code to a stable, efficient biodegradation. The MEM2BIO concept also may hold the potential to be used for other groundwater pesticides of concern.      AknowledgementsThis research was funded as part of the ‘MEM2BIO’ project funded by Innovation Fund Denmark (5157-00004B). The authors represent the partners in the project consortium.REFERENCESNikbakht Fini, M., Madsen, H. T., & Muff, J. 2019. The effect of water matrix, feed concentration and recovery on the rejection of pesticides using NF/RO membranes in water treatment. Separation and Purification Technology, 215, 521-527.Hylling, O., Nikbakht Fini, M., Ellegaard-Jensen, L., Muff, J., Madsen, H. T., Aamand, J., & Hestbjerg Hansen, L. (2019). A novel hybrid concept for implementation in drinking water treatment targets micropollutant removal by combining membrane filtration with biodegradation. Science of the Total Environment, 694, [133710]Figure 1.1 Results from microcosm experiments showing MSH1 BAM removal and mineralization in collected native water (CNW) from the clean water reservoirs of water works in Varde (left), Kolding (middle) and Hvidovre (right) and retentates. a – c) shows MSH1 removal and mineralization percent over time for treatments with varying BAM concentrations (setup 1). d – f) show results from treatments with same BAM concentration (setup 2). Treatments with CNW are shown as dashed lines and retentates as solid. Treatments with MSH1 inoculation are marked as follows: CNW;0.3 µg/L BAM (•, orange), x2 concentrated; 0.6 µg/L BAM (•, light gray), x5 concentrated; 1.5 µg/L BAM (•, dark gray) and x10 concentrated; 3.0 µg/L BAM (•, blue). Treatments without MSH1 (negative controls) are marked (•, red) and are used in both A-C and D-F. At t2 (dashed gray line), colour legends indicate which treatments differ significantly from CNW. Single asterisk (*); p<0.05 and double asterisk (**); p<0.01 (n=3). Error bars represent standard error of the mean (n=3), where very low errors are indiscernible on plot.Figure 1.2 Outlet BAM concentrations of samples from lab scale coloumn experiments using 2 µg/L BAM at 10 °C, a flow of 80 µl/min and retention time: 132 minutes. The legends “Old ino” and “New ino” represent tests of two different inoculation strategies.  	(a)	(b)Figure 1.3 (a) The pilot scale test trailer connected to a BAM contamination groundwater abstraction well. (b) a sketch of the dual line treatment system installed in the trailer.

Combined membrane filtration and biodegradation – a novel hybrid concept targeting BAM removal in drinking water production.

https://vbn.aau.dk/files/454627782/MUFF_IWA2020_MEM2BIO_v2.doc

Combined membrane filtration and biodegradation – a novel hybrid concept targeting BAM removal in drinking water production.

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