Breda, Inês Lousinha Ribeiro

Ramsay, Loren

Søborg, Ditte

When virgin filter media is placed in drinking water biofilters, a start-up period of some months typically ensues. During this period, the necessary inorganic coating and bacterial community are established on the filter medium, after which the treated water complies with drinking water criteria. In this study, the start-up of a full-scale biofilter using natural inherent inoculation was investigated using a thorough monitoring approach to document the changes that take occured. Results showed that interrelated physical, chemical and microbiological changes take place during specific phases and in specific strata in the filter medium. With this knowledge, it is possible to identify how to optimize the start-up process, including when and where to inoculate as well as what to inoculate with

    Aalborg UniversitetStart-up of a drinking water biofilterRamsay, Loren; Søborg, Ditte; Breda, Inês Lousinha RibeiroPublication date:2016Document VersionPublisher's PDF, also known as Version of recordLink to publication from Aalborg UniversityCitation for published version (APA):Ramsay, L., Søborg, D., & Breda, I. L. R. (2016). Start-up of a drinking water biofilter: Physical, chemical andbacteriological changes . Poster session presented at World Water Congress & Exhibition 2016, Brisbane,Australia.General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            ? You may not further distribute the material or use it for any profit-making activity or commercial gain            ? You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.Downloaded from vbn.aau.dk on: April 30, 2017INTRODUCTIONStart-up of a drinking water biofilterphysical, chemical and bacteriological changesRamsay, L.a Søborg, D.A.a Breda, I.L.a,b,ca) Via University College, Research Group for Energy and Environment, Campus Horsens, Denmark b) Skanderborg Forsyningsvirksomhed A/S, Denmarkc) Aalborg University, Department of Chemistry and Bioscience, Denmark When producing drinking water from groundwater, some waterworks use biofilters as the heart of the treatment process. In biofilters, microorganisms are allowed to populate granular filter media andto carry out the work of purifying the water (de Vet, 2009). This process is gaining attention because of a number of attractive features including 1) low price, 2) no addition of chemicals and 3)increase in the microbiological stability of the finished water.One drawback of biofilters is the long start-up period when new filter medium is commissioned. During the start-up period, an inorganic coating and a biofilm are established on the filter medium,after which the treated water complies with drinking water criteria. This period typically lasts two or more months (Cai, 2015; Stembal, 2004; Zeng, 2010). Disadvantages of a long start-up periodinclude: 1) the need to discharge water to the environment since the finished water does not comply with drinking water standards, 2) the use of energy and the waste of a precious resource, and 3)the need for an alternative drinking water source for the consumers for the duration of the start-up period. If the start-up process is to be optimized, a thorough knowledge of the development of fully-functioning biofilters is required.This poster elucidates the start-up process through a holistic monitoring approach at a newly-constructed full-scale waterworks in Denmark. This poster documents a natural start-up, using onlyinherent inoculation from microorganisms that are present in the raw water and the water used for backwash (no pro-active inoculation with old filter media or backwash water sludge was utilized).METHODS RESULTS and DISCUSSION• Using inherent inoculation, full-scale start-up was complete after a period ofapproximately 10 weeks.• The change from virgin filter media to fully functioning mature filter media is a complexmix of physical, chemical and microbiological processes. Holistic monitoring of theseprocesses using water, filter media and backwash water samples provided a more clearunderstanding of the start-up period.• Total bacteria (Eubacteria) were most abundant in the top 40 cm of Filter 1. Selectedbacterial groups (AOB, Nitrospira, Leptotrix) represented only a small percentage of thetotal bacteria.• Results from this work have important implications for optimizing the start-up processsuch as when and where to inoculate and what to inoculate with.CONCLUSIONSinspiring changeReferences: Frischherz, H, Zibuschka, F, Jung, H, Zerobin, W, 1985. Biological elimination of iron and manganese. Water Supply 3, 125, Søborg, DA, Breda, IL, Ramsay, L, 2015 Effect of oxygen deprivation on treatment processes in afull-scale drinking water biofilter, WST: Water Supply 15.4, 825-833. Breda IL, Ramsay, L, Søborg, DA, 2016. The role of backwash in start-up of full-scale drinking water biofilters. J. Water Supply: Research and Technology –AQUA 65(3), 234-243. de Vet, WWJM, Rietveld, LC, van Loosdrecht, MCM, 2009. Influence of iron on nitrification in full-scale drinking water trickling filters. Journal of Water Supply: Research and Technology – AQUA 58(4), 247. Cai, Y, Li,D, Liang, Y, Luo, Y, Zhang, J., 2015. Effective start-up biofiltration method for Fe, Mn, and ammonia removal and bacterial community analysis. Bioresource Technology 176, 149-155. Stembal, T, Markic, M., Briski, F, Sipos, L, 2004. Rapidstart-up of biofilters for removal of ammonium, iron and manganese from ground water. Journal of Water Supply: Research and Technology – AQUA 53(7), 509-518. Zeng, H, Li, D, Zhang, J, 2010. Rapid start-up of biofilter for removal ofiron and manganese from groundwater. Advanced Materials Research 113-116, 1316-1319.Acknowledgements: The authors appreciate the assistance of Aarhus Water, Silhorko-Eurowater and Xergi in connection with this work.RESULTS and DISCUSSIONwww.iwahq.orgParameter Average Std. Dev.Oxygen 0.22 mgL-1 0.12Iron 1.40 mgL-1 0.19Manganese 0.45 mgL-1 0.07Ammonium 0.21 mgL-1 0.04Magnesium 7.6 mgL-1 0.3pH 7.3 0.06Conductivity 58 mS/m 0.8Temperature 8.9°C 0.1Shading indicates concentrations not in compliance with Danish drinking water criteria.• Water samples (unfiltered) were collected from stainless steel taps at 16 locations: 13different depths on Filter 1 as well as raw water, water between filters and finishedwater.• Filter media samples were collected from 4 different depths in Filter 1 using a hollowstainless steel probe.• Backwash water samples were collected at one minute intervals during selectedbackwash events.Filtration Raw water qualitySamplingAnalysesPhysical Chemical MicrobialContinuous measurements• Flow• Temperature• Pressure• TurbidityGrab samples• Grain size, surface area and particle shape using Camsizer®64, RetchTechnology GmbHContinuous measurements• Dissolved oxygen• In-line pH• Conductivity• At-line ammoniumGrab samples• Iron, manganese and ammonium using HachDR3900 spectrophotometer• NitriteContinuous measurements• Bacterial counts (GrundfosBACMON)Grab samples• Heterotrophic plate counts• DNA isolation (PowerBiofilm, MoBio Laboratories Inc.)• qPCR (Eubacteria and relevant bacterial groups)ChemicalPhysicalBiologicalRetention time distributionTracer tests showed a medianretention time in Filter 1 of 29 min.This compares to 12 min. contactwith the filter media (green line).One of the production lines at Truelsbjerg waterworks, Denmark (Søborg et al., 2015).Flow and pressure drop for a filter run during start-up (Day 15-19)showed that values returned to initial values following a backwashevent. Note that the goal of backwashing during start-up is to avoidpressure build-up, not to ensure clean finished water.Separate phases for removal of individualcompounds during start-up were observed inthis study.Iron concentrations achieved compliancealmost immediately, complete ammoniumremoval required about 6 weeks whilecomplete manganese removal required about10 weeks.Clear stratification with depth wasobserved in water samples collectedfrom Filter 1:• Iron was removed at the top of thefilter (top 30 cm).• Ammonium was removedimmediately below the iron strata(30-70 cm).• Manganese was mainly removedclose to the bottom of the filter(130-210 cm).The central portion of Filter 1appeared to be less active.Filter media properties. Precipitation of iron oxides (redcolor) and manganese oxides (black color) were seen onfilter media samples collected over time from four depthsof each filter (Breda et al., 2016).Colour changes in filter media. Over time, thecolour of the filter media changed in the fourdepths that were sampled.day 22 day 35 day 39 day 43 day 67(Modified from Frischherz et al., 1985)The bacterial community on samples of filter medium was investigated at various timesduring the start-up period using qPCR methods. Total bacteria (Eubacteria) as well asammonium oxidizing bacteria (AOB), Nitrospira and Leptotrix were quantified.5%50%95%Numbers of specific bacterial groups increased over time, while EUB remained nearlyconstant. The highest number of EUB was found in the top layer of the filter. At the end ofthe start-up period, EUBs outnumbered the sum of the other bacterial groups by about10:1.VIA University College

Start-up of a drinking water biofilter:Physical, chemical and bacteriological changes

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Start-up of a drinking water biofilter:Physical, chemical and bacteriological changes

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