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 7123, Fax: 2358 0054, E-mail: kekyeung@ust.hk

Situation: 1. Malodor is a prevalent problem in densely populated urban centers due to ageing infrastructure; 2. It is a complex problem due to large range of compounds involved, their low concentration and transient nature as well as individual sensitivity.

Problem: 1. H 2 S and other malodor compounds are nuisance and pose a health risk; 2. They are source of citizen complaints and are difficult to treat; 3. H 2 S in sewer can cause sewer corrosion as well as fatalities.

Approach : 1. Control SRB (sulfur reducing bacteria) activities in sewer; 2. Room temperature catalytic treatment of malodorous compounds (i.e., H 2 S and NH 3 ). H 2 S + 1/2 O 2 → H 2 O + 1/8 S 8 NH 3 + 3/4 O 2 → 3/2 H 2 O + 1/2 N 2

Description of Technology: 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. 35 b Cu 2+ Fe 3+ NO - double-SiO 2 S14 Cumulative ClO 2 Released (%) 3 25 double-SiO 2 S15 TEOS Acid solution Mixing Hydrolysis Combine 15 Age Gel 5 ClO 2 Biocidal Acids hydrogel 0 0 4 8 12 16 20 24 28 Combine Time(day) Colloidal Mixing silica

Field Study – HKUSTCampus Performance study of biocidal gel technology under practical useconditions Pictures of the biocidal hydrogels with (a) PVA-SiO 2 and (b) double-SiO 2 frameworks. Bactericidal properties of hydrogels BactericidalReduction BiocidalHydrogels Day 1 Day7 Aerobic Anaerobic Aerobic Anaerobic SiO 2 99.9 99.9 99.0 98.0 PVA-SiO 2 95.0 97.0 90.0 90.0 double-SiO 2 95.0 94.0 92.0 95.0 90-160 m /h 3 Note: Bactericidal tests were carried out at room temperature using 10 5 CFU/ml of E. coli and 10 5 CFU/ml of Desulfobulbus propionicus.

Field Study – HKUSTCampus Performance study of biocidal gel technology under practical useconditions Inhibit microbial growth

Field Study – HKUSTCampus Performance study of biocidal gel technology under practical useconditions 800 control H 2 S concentration (ppb) control test 600 400 200 0 Jan Feb Mar Apr May Jun Suppresses H 2 S generation

Summary 9 weeks HKUST Site 2-weeks Background Period: Average H 2 S level = 180 ppb with the maximum level = 480 ppb. 5-weeks Test Period: A 200 gram sample treats an estimated 90,000 m 3 sewer water in 30 days (Average flow of 125 m 3 /h) Suppress H 2 S below olfactory threshold (< 40 ppb) Decreases malodor generating anaerobic bacteria by 60 % . 2-weeks Post-Test Period: Average H 2 S level = 150 ppb with the maximum level = 250 ppb.

Field Study – DSDSite Performance study of biocidal gel technology under realsituation Rainwater drainage line at JordanValley

upstream Field Study – DSDSite Performance study of biocidal gel technology under realsituation midstream downstream

Field Study – DSDSite Performance study of biocidal gel technology under realsituation Starting date: 8 th Dec End date: 19 th Feb H 2 S level was monitored by 2 HONEYWELL H 2 S Gas Detectors Background per location. The H 2 S concentration in the sewer were recorded on site and bacteria growthanalysis were performed in HKUST by taking samples on-site for4-weeks. 3 water samples were taken each week and measured at HKUST. 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.

midstream Field Study – DSDSite Performance study of biocidal gel technology under realsituation Midstream (location2) Average : 3.3 ppm 0 ppm 2.2 ppm Maximum : 5.5 ppm 0 ppm 7.0 ppm 14 Background Post-Test Test H2S concentration (ppm) 12 Average Highest 10 8 6 4 2 0 0 8 16 24 32 40 48 56 64 72 Days

midstream Field Study – DSDSite Performance study of biocidal gel technology under realsituation Midstream (location2) �������������������������� ���� ������������������������������ ��� Day Aerobic Anaerobic (*10^4cfu/ml) (*10^4cfu/ml) 0 26 40 2 3.8 18 60 Background Post-Test Test Bacteria Count (10 4 cfu/ml) 5 9.0 Aerobic 7 1.2 2.3 50 9 2.8 4.1 Anaerobic 13 10 6.0 40 15 6.8 3.0 19 15 5.8 30 21 87 74 28 19 15 20 28* 3.5 3.8 27 16 9.3 10 35 0.4 1.2 40 0.3 0.2 43 0.2 0.2 0 49 0.7 0.9 0 8 16 24 32 40 48 56 64 72 56 3.0 0.7 Day 66 6.5 9.3 73 14.8 3.5

Field Study – DSDSite Performance study of biocidal gel technology under realsituation Average : 3.0 ppm 0 ppm 1.7 ppm 3.4 ppm 0 ppm 2.2 ppm Maximum : 5.5 ppm 0 ppm 3.0 ppm 6.0 ppm 0 ppm 5.0 ppm 10 10 Background Post-Test Background Post-Test Test Test 9 9 H2S concentration (ppm) H2S concentration (ppm) Average Highest Highest Average 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 0 0 0 8 16 24 32 40 48 56 64 72 0 8 16 24 32 40 48 56 64 72 Day Days

Summary 11 weeks DSD Site 4 weeks Background Period: Average H 2 S level = 3.0 ppm, 3.3 ppm and 3.4 ppm in up, mid, down streams. The maximum level = 7ppm . 5 weeks Test Period: H 2 S level dropped to below 1 ppb in all streams 2-weeks Post-Test Period: Average H 2 S level = 0.6 ppm, 2.0 ppm and 1.8 ppm in up, mid, down streams. The maximum level = 3.0 ppm, 7.0 ppm and 4.0 ppm in up, mid, down streams. Aerobic bacterial concentration Anaerobic bacterial concentration (10 4 CFU/ml) (10 4 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%

Description of Technology: 1. Novel room temperature catalysts that convert H 2 S and NH 3 into harmless minerals, water and N 2 ; 2. Operates under high humidity (100 % R.H.) and dark conditions; 3. Long and stable operating life under extreme operating conditions found in drainage system. 3 catalyst Gel Humidity-resistant catalyst SiO 2 sol

H 2 S Malodor Treatment Performance study of the Novel Catalyst was carried out under: A saturated vapor (23.76 mmHg) at 25 o C (x ppm H 2 S, 3.05% H 2 O, 19.8% O 2 , 76.9% N 2 ) 900 b Novel Catalyst 1 aerogel H 2 S Conversion Rate 100 mg 0.8 VT10, 25mg, wet 600 Conversion µ mol 1 s -1 g -1 ) 0.6 0.4 ( µ µ µ 300 0.2 25 mg 0 0 0.1 1.0 5.0 10.0 15.0 0 10 20 30 40 Vanadium loading (wt. %) [H 2 S] ppm Note: the reaction was carried out for a 400 sccm 33.3 ppm H 2 S 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).

NH 3 Malodor Treatment Performance study of the Novel Catalyst was carried out under: A saturated vapor (23.76 mmHg) at 25 o C (0.22% NH 3 , 3.05% H 2 O, 19.8% O 2 , 76.9% N 2 ) 60 Novel Catalyst aerogel a 50 NH 3 Conversion Rate 40 µ mol 1 s -1 g -1 ) 30 ( µ µ µ 20 Olfactory threshold 10 0 1.0 5.0 15.0 Vanadium loading (wt. %) Note: the reaction was carried out for a 400 sccm 2183 ppm NH 3 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).

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 H 2 S in sewer flow of 120 m 3 /h treating 90,000 m 3 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 H 2 S and NH 3 malodor at room temperature and high humidity situation.

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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