Faculty of Environmental Sciences Institute of Urban Water Management, Chair of Water Supply Engineering Removal of disinfection by-product precursors by ultrafiltration in the South-West waterworks in Moscow, Russia Alexander Abe, Ekaterina Vasyukova, Wolfgang Uhl Technische Universität Dresden, Dresden, Germany Chair of Water Supply Engineering Demitri Allerdings, Gerrit Förster WTE Wassertechnik GmbH, Essen, Germany Contents 1. Natural organic matter in water treatment 2. Moscow South-West waterworks 3. Analytical and experimental methods 4. NOM removal across treatment 5. Trihalomethane formation potential due to chlorination and chloramination 6. Conclusions Natural organic matter in water treatment • Metabolic products of live organisms and degradation products of biological material (particulate and dissolved) • In North-West Russia degradation rates are low, surface waters drain peat land areas and are NOM-rich Natural organic matter in water treatment Influence on water quality: • Aesthetic (taste, odour and colour) • Precursor of potentially carcinogenic disinfection by-products during disinfection • Energy source for bacterial growth regrowth in distribution systems Natural organic matter in water treatment Influence on water treatment: • Membrane fouling • Poor particle separation during coagulation • Reduced adsorptive capacity of activated carbon Motivation • There is still a gap between theoretical/batch studies and practice • Theoretically optimal conditions are not always achievable during full-scale operation Objectives: • Evaluate the effectiveness of ultrafiltration and its pre-treatment to remove NOM and trihalomethane formation potential (THMFP) • Identify optimisation potentials of single processes with regard to NOM removal in waterworks Moscow South-West waterworks • Commissioned in December 2006 to improve the quality of the Russian capital’s drinking water supply • 250 000 m3/d treatment capacity • Among the most ambitious European projects in water technology • The first in the Russian Federation to use ultrafiltration South-West Waterworks Moscow South-West waterworks • • • • • Raw water from Moskva river Multi-barrier concept Treatment in 4 lines ca. 2 h average treatment time UF: 0.01 µm pore size Sampling points; May 2013 (n=2) Ultrafiltration at SWWW NOM characterisation • Size exclusion chromatography DOC quantification and fractionation using liquid chromatography with organic carbon detection (LC-OCD) • UV-Spectroscopy UVA254 and SUVA = UVA254 DOC • Chemical oxygen demand In Russia substitutes TOC or DOC monitoring NOM characterisation Liquid chromatography with organic carbon detection Building Blocks (BB) Humics (HS) Acids and LMW Humics Biopolymers (BP) LMW-Neutrals Inorganic Colloids Nitrate BP HS BB LMW acids LMW neutrals >> 10 kDa 400-1000 Da 300-500 Da < 350 Da < 350 Da Polysaccharides Proteins Humic and fulvic acids Hydrolysates of humic substances Carboxylic acids, Aldehydes Peptides, Amphiphylic subs. Huber et al. (2011) Determination of THM formation potential • Batch determination of THMFP in real samples taken across the waterworks • Chlorination and chloramination using chlorine and pre-formed chloramine solutions • THM measurement using Gas-chromatography NOM in raw water • COD = 6.2 mg O2/L • DOC = 6.4 mg/L • SUVA = 3.3 L/(mg·m) • NOM of terrestrial (pedogenic) origin Hydrophobic OC HOC • High biopolymer content Biopolymers BP • Good predicted NOM removability due to high humics content (60%) DOC composition 12 % 9% 4% Humics HS 16 % Building blocks BB 59 % LMWAacids LMW LMWNneutrals LMW Moskva river. Source: lopm.ru NOM removal across the treatment train Oxidierbarkeit COD SAK254 UVA 254 7 35 6 30 5 25 30 % 16 % 4 20 36 % 3 2 15 22 % 10 21 % 5 49 % 1 30 % 0 0 Raw Post-ozon. Pre-ozon./ ML-filtration Coag./Sedim. UF UVA (1/m) DOC (mg/L) COD (mg O2/L) DOC NOM removal across the treatment train BP HS BB LMW N SUVA 7 4 6 3 5 2 4 1 3 0 2 -1 1 -2 0 -3 Raw Post-ozon. Pre-ozon./ Coag./Sedim. ML-filtration UF SUVA (L/(mg·m)) DOC (mg/L) DOC Total NOM removal BP HS BB LMW N 4 3 SUVA 2 55 % 45.% 1,5 51 % 2 1 1 77 % 0 38 % 24 % Total DOC removal (cumulated) 0,5 0 removed SUVA (L/(mg·m)) removed DOC (mg/L) DOC Total removal: 60 % COD 45 % DOC 55 % SUVA Finished water: COD = 2.5 mg O2/L DOC = 3.5 mg/L SUVA = 1.5 L/(mg·m) Reduction of THM formation potential Chloramination spez. THMFP (Chloramin) 60 6 50 5 40 4 42 % 14 % 30 6% 3 20 2 10 1 0 0 Raw Post-ozon. Pre-ozon./ Coag./Sedim. ML-filtration specific chloramine-THMFP (µg TTHM/mg DOC) specific chlorine-THMFP (µg TTHM/mg DOC) Chlorination spez. THMFP (Chlor) UF pre-ozonation/coag./sedimentation > ML-filtration > UF (removal of high MW DOC and chlorine-reactive, non-settleable particulate NOM) THM formation potential after chlorination Humic substances DOC (mg/L) 0 2 4 6 8 10 Chlorine-THMFP (µg THM/L) 350 300 R² = 0,83 250 UVA254 200 R² = 0,91 150 Humic substances 100 50 0 0 2 4 6 8 10 12 14 16 18 20 UVA254 (1/m) for DOC-fractions: HS (0.83) > BP (0.4) > LMW N (0.35) > BB (0.1) Conclusions • ½ of DOC and ¾ of chlorine-activated THMFP were removed good agreement with other (conventional) waterworks • Pre-ozonation/coagulation/sedimentation (+ ML-filtration) essential pre-treatment reduction of UF fouling and THMFP reduction • DOC removal: Biopolymers > Humics > LMW neutrals > B. blocks • Ultrafiltration removed Biopolymers completely • UVA254 and LC-OCD-characterisation can be used for THMFP prediction Thank you for your attention
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