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Innovative Technologies for Treatment of Malodors in Sustainable - - PowerPoint PPT Presentation
Innovative Technologies for Treatment of Malodors in Sustainable - - PowerPoint PPT Presentation
Innovative Technologies for Treatment of Malodors in Sustainable Drainage System Prof King Lun Yeung Department of Chemical and Biomolecular Engineering & Division of Environment Hong Kong University of Science and Technology Tel.: 2358
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Problem:
1. H2S and other malodor compounds are nuisance and pose a health risk; 2. They are source of citizen complaints and are difficult to treat; 3. H2S in sewer can cause sewer corrosion as well as fatalities.
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Approach:
1. Control SRB (sulfur reducing bacteria) activities in sewer; 2. Room temperature catalytic treatment of malodorous compounds (i.e., H2S and NH3).
H2S + 1/2 O2 → H2O + 1/8 S8 NH3 + 3/4 O2 → 3/2 H2O + 1/2 N2
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Description of Technology:
TEOS Acid solution Hydrolysis Mixing Combine Age Gel Mixing
1. The controlled-release gel that continuously dose biocides and inhibitors that specifically target microorganisms causing malodor; 2. Only safe and U.S. FDA/EPA approved materials are used; 3. The controlled-release gel is designed to last for at least 30 days and work under aggressive environment found in sewer and drainage system.
Cu2+ Fe3+ NO -
3
Colloidal silica ClO2 Acids Combine Biocidal hydrogel
4 8 28 12 16
Time(day)
20 24 5 15 25 35
Cumulative ClO2 Released (%)
b
double-SiO2S14 double-SiO2S15
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Field Study – HKUSTCampus
Performance study of biocidal gel technology under practical useconditions
BiocidalHydrogels Pictures of the biocidal hydrogels with (a) PVA-SiO2 and (b) double-SiO2 frameworks.
Bactericidal properties of hydrogels
BactericidalReduction Day 1 Day7
Aerobic Anaerobic Aerobic Anaerobic
SiO2 99.9 99.9 99.0 98.0 PVA-SiO2 95.0 97.0 90.0 90.0 double-SiO2 95.0 94.0 92.0 95.0 Note: Bactericidal tests were carried out at room temperature using 105 CFU/ml of E. coli and 105 CFU/ml of Desulfobulbus propionicus.
3
90-160 m /h
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Field Study – HKUSTCampus
Performance study of biocidal gel technology under practical useconditions
Inhibit microbial growth
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600 400 200 800 Jan Feb Mar Apr May Jun
H2S concentration (ppb)
control control test
Field Study – HKUSTCampus
Performance study of biocidal gel technology under practical useconditions
Suppresses H2S generation
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Summary
9 weeks HKUST Site
2-weeks Background Period: Average H2S level = 180 ppb with the maximum level = 480 ppb. 5-weeks Test Period:
A 200 gram sample treats an estimated 90,000 m3 sewer water in 30 days (Average flow of 125 m3/h)
Suppress H2S below olfactory threshold (< 40 ppb) Decreases malodor generating anaerobic bacteria by 60 %. 2-weeks Post-Test Period: Average H2S level = 150 ppb with the maximum level = 250 ppb.
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Field Study – DSDSite
Performance study of biocidal gel technology under realsituation Rainwater drainage line at JordanValley
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Field Study – DSDSite
Performance study of biocidal gel technology under realsituation
upstream midstream downstream
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Field Study – DSDSite
Performance study of biocidal gel technology under realsituation
Starting date: 8th Dec End date: 19th Feb
Background
The H2S concentration in the sewer were recorded on site and bacteria growthanalysis were performed in HKUST by taking samples on-site for4-weeks.
Testing
A porous container with multi-functional gel were put into the sewer. Study was done for 5-weeks so as to investigate the duration of effectiveness on malodorremoval.
Post-testing
A 2-week study will be performed to evaluate the post-effect after removal of thegel.
H2S level was monitored by 2 HONEYWELL H2S Gas Detectors per location. 3 water samples were taken each week and measured at HKUST.
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Field Study – DSDSite
Performance study of biocidal gel technology under realsituation Midstream (location2)
midstream
Average : 3.3 ppm Maximum : 5.5 ppm 0 ppm 0 ppm 2.2 ppm 7.0 ppm
2 4 6 8 10 12 14 8 16 24 32 40 48 56 64 72 H2S concentration (ppm) Days Average Highest Background Test Post-Test
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Field Study – DSDSite
Performance study of biocidal gel technology under realsituation Midstream (location2)
midstream
Day Aerobic (*10^4cfu/ml) Anaerobic (*10^4cfu/ml) 26 40 2 3.8 18 5 9.0 7 1.2 2.3 9 2.8 4.1 13 10 6.0 15 6.8 3.0 19 15 5.8 21 87 74 28 19 15 28* 3.5 3.8 27 16 9.3 35 0.4 1.2 40 0.3 0.2 43 0.2 0.2 49 0.7 0.9 56 3.0 0.7 66 6.5 9.3 73 14.8 3.5
10 20 30 40 50 60 8 16 24 32 40 48 56 64 72 Bacteria Count (104 cfu/ml) Day Aerobic Anaerobic Background Test Post-Test
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Field Study – DSDSite
Performance study of biocidal gel technology under realsituation
Average : 3.0 ppm Maximum : 5.5 ppm 0 ppm 0 ppm 1.7 ppm 3.0 ppm
1 2 3 4 5 6 7 8 9 10 8 16 24 32 40 48 56 64 72 H2S concentration (ppm) Day Average Highest Background Test Post-Test 1 2 3 4 5 6 7 8 9 10 8 16 24 32 40 48 56 64 72 H2S concentration (ppm) Days Highest Average Background Test Post-Test
3.4 ppm 6.0 ppm 0 ppm 0 ppm 2.2 ppm 5.0 ppm
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Summary
11 weeks DSD Site
4 weeks Background Period: Average H2S level = 3.0 ppm, 3.3 ppm and 3.4 ppm in up, mid, down streams. The maximum level =7ppm. 5 weeks Test Period: H2S level dropped to below 1 ppb in all streams 2-weeks Post-Test Period: Average H2S level = 0.6ppm, 2.0ppm and 1.8 ppm in up, mid, down streams. The maximum level =3.0ppm, 7.0ppm and 4.0ppm in up, mid, down streams.
Aerobic bacterial concentration (104 CFU/ml) Anaerobic bacterial concentration (104 CFU/ml) Upstream Midstream Downstream Upstream Midstream Downstream Background 3.5 31 16 4.2 27 11 Testing 3.4 1.3 1.7 4.0 1.0 1.2 Reduction 3% 96% 89% 5% 96% 89%
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Description of Technology:
1. Novel room temperature catalysts that convert H2S and NH3 into harmless minerals, water and N2; 2. Operates under high humidity (100 % R.H.) and dark conditions; 3. Long and stable operating life under extreme
- perating conditions found in drainage system.
3
catalyst SiO2 sol Gel Humidity-resistant catalyst
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H2S Malodor Treatment
Performance study of the Novel Catalyst was carried out under:
A saturated vapor (23.76 mmHg) at 25oC (x ppm H2S, 3.05% H2O, 19.8% O2 , 76.9% N2)
300 600 900 0.1 1.0 5.0 10.0 15.0
Vanadium loading (wt. %) H2S Conversion Rate
(µ µ µ µmol1s-1g-1)
b
aerogel
Note: the reaction was carried out for a 400 sccm 33.3 ppm H2S in air at room temperature (298 K) over 25 mg catalyst. The Novel Catalysts contain 15 wt.% of vanadia catalyst (i.e., 3.75 mg catalyst). 0.2 0.4 0.6 0.8 1 10 20 30 40
Conversion [H2S] ppm
VT10, 25mg, wet 25 mg 100 mg
Novel Catalyst
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NH3 Malodor Treatment
Performance study of the Novel Catalyst was carried out under:
A saturated vapor (23.76 mmHg) at 25oC (0.22% NH3, 3.05% H2O, 19.8% O2 , 76.9% N2)
10 20 30 40 50 60 1.0 5.0 15.0
NH3 Conversion Rate
(µ µ µ µmol1s-1g-1)
Vanadium loading (wt. %)
a
aerogel
Note: the reaction was carried out for a 400 sccm 2183 ppm NH3 in air at room temperature (298 K) over 25 mg catalyst. The Novel Catalysts contain 15 wt.% of vanadia catalyst (i.e., 3.75 mg catalyst).
Olfactory threshold
Novel Catalyst
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Concluding Remarks
1. The controlled-release gel is a fast-acting and effective technology for malodor suppression for water drainage system; 2. The gel can be easily deployed in problem area and has a long lastingeffect; 3. The cost of the gel is low and 200 gram (= 0.2 L) gel is able to suppress H2S in sewer flow of 120 m3/h treating 90,000 m3 of drainagewater; 4. 10-30 % of aerobic bacteria remained viable during the 30 daytests. 5. A Novel Catalyst was shown to be effective in suppressing airborne H2S and NH3 malodor at room temperature and high humidity situation.
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Acknowledgement
We would like to acknowledge the financial supports from the Hong Kong Innovation and Technology Fund (ITS/188/01), the Hong Kong Environment and Conservation Fund/Woo Wheelock Green Fund. We are also grateful for the help and advice from the Hong Kong Drainage Services Department. This talk includes works by:
- Mr. Kei Bo CHEUNG
- Mr. Long Ting LUK
- Dr. Hao CHEN
- Prof. Wei HAN
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