Faculty of Environmental Sciences Institute of Urban Water Management, Chair of Water Supply Engineering Title of presentation Impact of different treatment processes on concentrations of DBPs and DBP precursors in swimming pools Irene Slavik, Wolfgang Uhl, Bertram Skibinski Technische Universität Dresden, Dresden, Germany Chair of Water Supply Engineering Norsk Institutt for Vannforskning (NIVA) wolfgang.uhl@niva.no
pool water It is the bather who is to be blamed DBP Splash water Organics particles DBP recirculation Cl2 swimming pool Cl 2 DBP treatment drainage basin waste water organics particles Heat Exchange filling water backwash water
Disinfection by-products in pool water DIN 19643: free chlorine is mandadory (0.3 0.6 mg/l at ph 6.5..7.5) input of organic substances by bathers formation of disinfection by-products (DBPs) Minimization of DBP concentration removal of DBPs removal of DBP-precursors
Research objectives How can DBP concentrations be minimized? Comparison of different pool water treatment technologies (conventional, Ultrafiltration, UV) To which extent can DBPs be removed from pool water by water treatment? To which extent can DBP precursors be removed from pool water by water treatment? How is DBP-formation influenced by water treatment?
Preliminary considerations Full scale swimming pool systems are highly complex investigations under defined conditions are impossible Lab-scale experiments conditions in several processes as filter flushing and membrane operation can hardly be reproduced High volumes required for frequent analysis cannot be provided Construction of a swimming pool model defined conditions and reproducibility can provide hight sample volumes needed modular water treatment processes to implement different water treatment combinations
Experimental Design CIRCULATION PUMP STIRRED TANK FRESH WATER DOC DOSING FRESH WATER TEMPERATURE CONTROL UNIT AIR OUT BATHER LOAD DOSING AIR IN POOL (covered) FLOCCULANT DOSING PAC DOSING SAND FILTRATION GAC FILTRATION UV LAMP NaOCl DOSING ACID/BASE DOSING ULTRA FILTRATION Datenerfassung
Experimental design Model swimming pool Aeration Air space Sand & GAC filter Pool 2.6 m³ Onlinemonitoring UV Ultrafiltration + CEB
Data akquisition & control
Experimental design Bather load Fresh water DOC simulated by addition of humic acid sodium salt to carbon-free tap-water Addition of body fluid analogue to pool water (BFA, Judd & Black 2000) Simulation of human urin and sweat composition Ingredient Input [mgh -1 ] Citric acid 9.7 Uric acid 7.4 Urea 224 Creatinine 27 L-histidine 18 Hippuric acid 26 Ammonia chloride 30 Highest permitted batherload during 24 h Fresh water DOC (humic acid) 1 mg DOC L -1 8.5 Lh -1 BFA and fresh water dosing amounts Pool Volume: 2.6 m³
Experimental design - Analytics Online and semicontinuous sampling Free chlorine, ph, Redox (for control at constant concentration) Total and combined chlorine, TOC, conductivity, temperature Volatile DBPs by Membrane inlet mass spectrometry (MIMS) Manual sampling Characterization and quantification of dissolved organic matter by Liquid Chromatography organic carbon detection (LC-OCD) GC-MS as lab reference to MIMS-measurements
Experiments Experiment 1: Coagulation Sand Filtration Granular Activated Carbon Filtration ph adjustment chlorination Experiment 2: Coagulation Ultrafiltration low pressure UV ph adjustment chlorination Experiment 3: Coagulation Ultrafiltration medium pressure UV ph adjustment chlorination Experiment 4: Coagulation Powdered Activated Carbon Ultrafiltration ph adjustment chlorination Experiment 5: Coagulation Powdered Activated Carbon Sandfiltration ph adjustment chlorination Load-factor k in all experiments: 0,5
Experimental design - Operation steady state reached after > 3 weeks
Sand + GAC: chloramine and TOC 1 2 3 Free chlorine combined chlorine trichloramine TOC
UF + low pressure UV: chloramine and TOC 1 3 2 2 Free chlorine combined chlorine trichloramine TOC
UF + medium pressure UV: chloramine and TOC 2 1 Free chlorine combined chlorine trichloramine TOC
Concentrations in the basin: TOC and chlorine-species 1 2 3 5 5 4 Free chlorine combined chlorine trichloramine TOC
Summary and Conclusions Low-pressure UV can contribute to removal of trichloramine but is not suitable for removal of other chloramines Medium-pressure UV contributes to removal of trichloramine as well as other chloramines and brominated THM but: Medium-Pressure UV enhances formation of new DBPs in the pool, due to transformation of organic substances towards higher reactivity resulting in even higher concentrations of NCl3 and brominated DBPs in the basin currently we do not recommend medium-pressure UV for pool water treatment, as long as processes are not better understood and controlled Activated Carbon (both PAC and GAC) enable removal of trichloramine completely Conventional Pool Water Treatment with Granular Activated Carbon enables best results with respect to concentrations of chloramines and DBPs in the pool It needs to be kept in mind that all processes guaranteeing high removal of chloramines also require higher amounts of chlorine to be dosed
Thanks for your attention