Bank filtration as practiced in Berlin, a treatment process in semi-closed water cycles. Mathias Ernst*; Steffen Grünheid**, Martin Jekel**

Transcription

1 The Berlin Water Cycle Bank filtration as practiced in Berlin, a treatment process in semi-closed water cycles Mathias Ernst*; Steffen Grünheid**, Martin Jekel** Technische Universität Berlin * Centre for Water in Urban Areas (FSP-WIB) ** Department of Water Quality Control 1 Outlook The water situation of the City of Berlin Research study on bank filtration Field site monitoring results Soil column tests Comparative analysis Conclusions 2

2 City of Berlin 3 25 German average river flow rates 228 Flow rate in m³ per s Berlin is rich in surface water but poor in water flow In dry periods the daily wastewater flow acceeds the flow rates of Berlin rivers Rhine Oder SpreeHavelWastewater discharge 4

3 Average Water Resources Average Available Water Resources 36 million m 3 per year Natural Groundwater Recharge Artificial Groundwater Recharge Bank Filtered Water * Berliner Wasserbetriebe 5 Organic compounds in domestic treated wastewater Average values, SWTP Ruhleben (12 samples Nov Jun. 25 ) 1 ng L -1 1 ng L -1,1 µg L -1 1 µg L -1 1 µg L -1 1 µg L -1 EDC: Estrone, 17β-Estradiol 17α-Ethinylestradiol Pharmaceuticals: Bezafibrate, Naproxen, Phenazone, Propyphenazone, Clofibric acid, Ketoprofene, etc. ICM: Iopamidol, etc. Pharmaceuticals: Carbamazepine, Diclofenac AOI DOC (~11 mg/l) Metabolites: AMDOPH, AMPH Metabolites: FAA, AAA 7

4 NASRI Natural and artificial systems for recharge and infiltration Microbiological Load: Viruses Bacteria Chemical Load: Polar, poorly and non-degradable organic pollutants (industrial chemicals, PhACs) Cyanobacterial toxins Organohalogens (AOX), esp. AOBr and AOI Natural Load: Background humic substances (NOM), interaction with EfOM Sulfate 9 Research overview Examined systems Field monitoring months of sampling at three different field sites for bulk organics and trace pollutants to examine the fate of the compounds at field sites Short retention columns Testing the degradability of trace organic pollutants under different redox conditions, different temperatures and retention times < 1 d in a lab-scale system Long retention columns Testing for the kinetics of degradation of bulk organics and trace pollutants in a large scale aquifer simulation column with a retention time of 3 d 1

5 Investigated organic compounds Bulk organics (DOC (SEC), AOI, UV, TON) Iopromide CH 2 O CH 3 I CO NH NH 2 CO Sulfamethoxazole I OH CH CH 2 OH NH CH 2 I OH CH CH 2 OH CO N CH2 CH 3 O S N O H O N Iodinated X-ray contrast media Iopromide is part of AOI (organic iodine) Very stable and hydrophilic Not efficiently removed in STP STP - effluent concentrations => 1-2 µg/l Antibiotic (Bacteriostactic) Not efficiently removed in STP Widely used (application 2 g/d) STP - effluent concentrations ~1 µg/l Naphthalenedisulfonates SO 3 - SO - 3 e.g. 1,5-NDSA Aromatic Sulfonates Intermediates of different industrial processes Occur in domestic sewage and are not efficiently removed in STP STP - effluent concentrations ~.2-1 µg/l 11 Situation in Berlin at Lake Tegel Drinking water wells Upper Havel 8-35 m 3 /s Tegeler Fließ.2-.8 m 3 /s Lake Tegel, ca. 4 % STP Nordgraben,7-1,8 m 3 /s (STP Schönerlinde ~1 m 3 /s) WW Tegel Groundwater recharge facility 9-38 m 3 /s 12

6 Field sites at Lake Tegel Natural system Mostly anoxic soil passage Distance bank - well ~8-1 m Retention time ~4.5 5 months Artificial system (15 Mio. m 3 /a) Mostly oxic soil passage Distance bank - well ~5-1 m Retention time ~5 days 13 Bank filtration transect Tegel W < < < TEG371OP TEG371UP 338 < Name of observation well Retention time [month] Percentage of bank filtrate [%] Redox potential [mv] 371OP U 2.8 P TEG well 13 aquifer aquitard Well 13 ~ m E m below m above ground sea-level

7 Artificial recharge facility Tegel 366 ~ ~ OP ~ OP ~ UP 169 Name of observation well Retention time [days] Percentage of recharged water [%] Redox potential [mv] 368UP ~ UP ~ Well 2 ~ Results - DOC concentrations DOC [mg/l] T[month] S[meter] Lake Tegel Bank filtration site (n=18-23) 371 UP Well , DOC [mg/l] T[days] S[meter] Basin OP GWR Facility (n=16-2) < UP OP UP 5 32 Well Stable but high DOC-concentration in Lake Tegel (6-8 mg/l) Degradation of surface water DOC down to mg/l at both field sites Faster DOC-removal under aerobic conditions (GWR, 25 d) and slower DOCremoval in anoxic aquifers (Bank filtration Tegel, 4 months plus) 16

8 Input Output analysis of anoxic bankfiltration λ H 2 O O 2 NO 3 NH 4 DOC BDOC POC =>.1 m/h => 11 mg/l => 1.8 mg/l (NO 3 -N) =>.1 mg/l (NH 4 -N) => 6 8 mg/l => mg/l =>.5 mg/l Effects at water- soil interface: Sedimentation and filtration of POC Growth and die-off of biomass Inventory Incorporation of POC in POC ~.5% w/w sediment CaCO 3 ~.2% w/w Effects in bank sediment: Mineralization of infiltrated BDOC Consumption of O 2 and NO 3 Degradation of inventory POC Dissolution of CaCO 3 Production of inorganic carbon Reduction of Mn 4+ and Fe 3+ Reduction of ph Factors of Influence: Temperature H 2 O =>.1 m/h CO 2 -C => 3.3 mg/l HCO - 3 -C => 6.9 mg/l TIC => 1 mg/l Ca => 11 mg/l => 3,3 mg/l C in CaCO 3 ph => Mn 2+ => mg/l Fe 2+ => mg/l 17 Mass balance of C and redox reactions Oxygen balance Input O 2 in infiltrating water ~ 11. mg/l O 2 equivalent in infiltrating NO 3 ~ 6.1 mg/l Sum Consumption ~ 17.1 mg/l O 2 for BDOC mineralization ~ 6.8 mg/l = 2.5 * 2.7 (mean oxidation number (MON)) O 2 for water POC mineralization ~ 1.3 mg/l =.5 * 2.7 (MON) O 2 for nitrification ~.35 mg/l =.1 * 3.5 O 2 for POC mineralization ~ 8.7 mg/l = 3.2 * 2.7 (MON) Sum ~ mg/l Input BDOC in infiltrating water ~ 2.5 mg/l POC in infiltrating water ~.5 mg/l POC in sediment inventory ~ 3.2 mg/l Carbon from CaCO 3 dissolution ~ 3.3 mg/l Sum ~ 9.5 mg/l Output Carbon in CO 2 ~ 3.3 mg/l Carbon in HCO - 3 ~ 6.9 mg/l Sum Carbon balance ~ 1.2 mg/l 18

9 Results - AOI concentrations Bank filtration site (n=18) 16 GWR Facility (n=16) AOI [µg/l] 15 1 AOI [µg/l] Lake Tegel OP 371 UP Well Recharge Basin OP UP OP UP Well AOI [µg/l] Correlation of AOI and redox potential Tegel GWR Tegel Wannsee Wannsee Redox potential [mv] Less removal of AOI at the aerobic GWR compared to the anoxic bank filtration site Relationship between redox potential due to reductive deiodination Confirmed by third site (Wannsee) 19 Results - Trace pollutants Removal of Iopromide is efficient under anoxic and aerobic conditions Sulfamethoxazole has higher removal rates at anoxic bank filtration 1,7- and 2,7 NDSA seem to be better reduced under oxic conditions 1,5-Naphthalenedisulfonate is not degraded 2

10 Summary field results Faster removal of DOC during oxic infiltration, anoxic/anaerobic infiltration require longer retention times for same DOC removal Removal of Iopromide is efficient under anoxic and aerobic conditions Some AOI degradation was found under reducing conditions Sulfamethoxazole shows better removal at bank filtration site 1,7- and 2,7 Isomers of NSA are better reduced under oxic conditions 1,5-Naphthalenedisulfonate is not degraded or adsorbed 21 Set-up - Soil Column System Target compounds X-ray contrast media Iopromide Bakteriostatica Sulfamethoxazole Naphthalenedisulfonates 1,5-; 1,7-; 2,7-NDSA Dosage µg/l Background (Lake Tegel) ng/l Comparison to field conditions: Darcy-velocity of ~1 m/d (complies with field sites in Tegel) Operated with surface water from Lake Tegel Hydraulic conductivity ( m/s) and sediment comparable to field condition POC- and calcite-content lower than in the real aquifer Average temperature ~4 C higher than in the field 22

11 Soil column studies Soil column system operated under two different dominant redox conditions oxic conditions (4/23 4/24) anoxic conditions (5/24 4/25) Oxic: Depletion of oxygen (~2.4 mg O 2 /mg DOC); no denitrification Anoxic: Clear denitrification; some reduction of iron und manganese oxides 23 Bulk organics - DOC and UVA % -33% -47% -5% More efficient reduction of DOC in aerobic state Consistency with the UVA 254 -results (different kinetics) Lake Tegel field results Faster DOC reduction under aerobic conditions After 3-6 months of infiltration the DOC-residuals were comparable under aerobic and anoxic/anaerobic conditions 24

12 Bulk organics - LC-OCD HS HS-hydrolysates Org. acids PS Neutrals Oxic Very fast degradation of polysaccharide-fraction during the first.21 m Partial degradation of other fractions Anoxic No complete degradation of polysaccharides Partial removal of other DOC constituents 25 Trace compounds - Iopromide Very good removal of Iopromide under both redox conditions Consistent with findings of the field monitoring 26

13 Trace compounds - AOI -9,1% -24,4% Oxic: no efficient removal of AOI (~9% in the infiltration zone) Anoxic: 25% removal of AOI during infiltration (reductive dehalogenation in anaerobic parts of the column) 27 65% 95% Better removal of Sulfamethoxazole under oxic conditions Conflict with field results (oxic: 5%, reducing conditions: 8%) Possible reasons: Higher concentration or temperature could affect removal mechanisms Strongly anaerobic conditions necessary for better removal 28

14 Trace compounds - Naphthalenedisulfonates 4% 12% 56% 98% No removal of 1,5-NDSA 1,7- und 2,7-NDSA: efficient degradation under oxic conditions 75% 99% Consistent with field results, removal rates slightly higher (T-effect?) 29 Summary bulk organics Fast degradation of biodegradable DOC under oxic conditions The fraction of polysaccharides is efficiently and fast degraded under oxic conditions. Only parts of the PS-fraction can be removed in anoxic state Other DOC-fractions (humics, HS-hydrolysates and low molecular weight acids) are partially degraded independently from the dominant redox conditions AOI is better removed at anaerobic (low redox) conditions 3

15 Summary trace compounds Some compounds show dependency of the elimination from redox conditions Soil column tests confirmed in general the results of field monitoring Iopromide: good removal independently from the redox conditions, Sulfamethoxazole: not consistent with field results, 1,5-NDSA 1,7- und 2,7-NDSA => persistent, no removal (tracer) => oxic degradation faster 31 Overall conclusion Natural bankfiltration for drinking water pretreatment is an effective removal step for most organics A mix of aerobic and anoxic conditions appear favorable for improved removal of a wider range of trace organic compounds Retention times recommended: Aerobic: 1 month Anoxic: 4 6 months Berlin experiences on bank filtration are currently transfered to a demonstration site in India (EU TECHNEAU project) 32

16 Acknowledgements We would like to thank all cooperation partners in the NASRI-project Berliner Wasserbetriebe, Kompetenzzentrum Wasser Berlin and Veolia Water for the financial support. Questions?? 33