Transformations of Organic Carbon in three Greywater Recycling Systems employing Different Post-treatments September 15, 2016 Funding provided by The Bill and Melinda Chris Ziemba Gates Foundation Odile Larivé Eberhard Morgenroth
Three water demands Hand washing Personal hygiene Flushing basin
Water recycling system overview Biologically- Activated Use Post- Storage Use Membrane Treatment Bioreactor (BAMBi) 5,9 l GAC Post- Storage Treatment
Goals for Post-Treatment 1. Remove color Transformations and removals of 2. Prevent pathogen regrowth organic carbon
Goals for Post-Treatment Transformations 1. Remove color and removals of 2. Prevent pathogen regrowth organic carbon Non-selective Post-treatment Selective Post-treatment
Three Post-Treatments to test Ozone Electrolysis GAC Oxidation: Oxidation: Sorption/ Biodegradation: Hydroxyl radical: Ozone: Selective for non-polar/ - 2.7 eV - 2.07 eV biodegradable oxidation potential oxidation potential compounds - lifetime in H 2 0 < sec. - lifetime in H 2 0~20 min. Non-Selective Selective for aromatics and double bonds
Experimental approach Batch experiments with real permeate - Targeting maximum carbon removal - Monitor DOC Color Liquid chromatography profiles (size) Assimilable Organic Carbon (AOC) Ozone Electrolysis GAC
DOC batch profile Exposure Exposure Exposure 0 67 133 200 Times passed through GAC 0 0.2 0.4 0.6 0 0.4 0.8 1.2 0 0.005 0.009 0.014 Energy (kWhr L -1 ) Energy (kWhr L -1 ) Energy (kWhr L -1 )
Color removal and DOC concentrations Color Good enough Cannot see any color Exposure
AOC and DOC AOC DOC
Liquid Chromatography – Organic Carbon Detector
Ozone – size chromatography AOC generation may be linked to increases in Building Blocks, Low Mol. Wt. Humics and Neutrals # indicated peak order ( # means size) 1 2 3 4 4 5
Electrolysis – size chromatography AOC production is not clearly linked to increases in LC-OCD fractions # indicated peak order ( # means size) 1 2 3 4 4 5
Biological stability through AOC Biological stability AOC threshold ? Exposure Exposure Exposure
Combining color removal and biological stability Biological stability AOC threshold ? Color Good enough Cannot see any color Exposure Exposure Exposure
Conclusions - Ozone, Electrolysis and GAC are able to remove color - Only GAC is able to demonstrate reliable biological stability by AOC measurement - Ozone and Electrolysis may be able to achieve biological stability through antimicrobial residual (ozone and chlorine)
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Conclusions - Ozone (more strongly) and Electrolysis demonstrate preferences for removal of color relative to DOC, and target the humic substance fraction of the LC-OCD profile. GAC treatment is non-selective. - Both Ozone and Electrolysis demonstrate AOC production at different points in the batch DOC removal profile. - The production of AOC by electrolysis may be linked to increases in Building Blocks, Low Mol. Wt. Humics and Neutrals. - Biological stability (by AOC) requires more treatment than color removal. - Ozone may be able to achieve biological stability. - Electrolysis failed to achieve biological stability. - GAC is able to achieve biological stability.
Experimental approach 1 Batch experiments with real permeate - Targeting maximum carbon mineralization / removal - Monitor DOC, Color, Chromatography (size), Assimilable Organic Carbon Ozone Electrolysis GAC - Repeated pouring - Boron-doped diamond - Corona-discharge - 14 V 2.4 A through GAC column ozone generator - 5 min. polarity reversal - 300 mg/hr at generator - 1-1.4 mm grain size (with 1 min. off) - bubbled (2 L/min air) - 3- 4 mm ø bubbles - 0.7 L/min recirculation - 0.3L GAC (170 dry g) - temperature controlled - 2 meter tall column
Current Prototype uses Electrolysis Mineralization of Carbon Production of Chloride 5,9 l GAC Cathode Anode - H 2 O + H + R= organics B H + HO* H 2 - B= Boron dopant + B HO* R H + HO*= hydroxyl rad - + RO+H + H 2 Oxidation 2.7 = potential eV e - e -
Color loss by spectrophotometer
Size exclusion chromatography
Many System Iterations 24
Liquid Chromatography – Organic Carbon Detector
Summary Ozone Electrolysis GAC Removal DOC Color DOC Color DOC Color preference Sufficient YES YES YES Color Removal Biological ??? NO YES Stability (AOC) - Ozone produces delayed AOC increase - Maybe linked to increases in specific LC-OCD fractions - Electrolysis immediately produces AOC increase - not clearly linked to a LC-OCD fraction - GAC does not produce Ozone
Impacts on full-scale bioreactor operation No Post- 5,9 l GAC treatment 1250 mg/L TOC 45-50 mg/L TOC Electrolysis ~18 mg/L TOC 1212 mg/L TOC ~12 mg/L TOC Activated Carbon ~2 mg/L TOC ~8 mg/L TOC 1202 mg/L TOC
Color contributing chemicals of Urine and Feces Urobilinogen Stercobilin
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