West County Treatment Plant Noise and Odor Control Project Update. June 29, 2004

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1 West County Treatment Plant Noise and Odor Control Project Update June 29, 2004

2 West County Meeting Purpose 1. Brief history of odor and noise control project 2. Describe odor and noise control systems installed 3. Review odor control follow-up testing 4. Take questions from residents

3 History of Odor and Noise Control 1. Plant odor study in August Public Meetings throughout the study process 3. Community odor surveys Sept.-Dec MSD Board approval of $1.9 million project in Noise survey in Dec Initiatives

4 History of Odor and Noise Control Project at West County (cont.) 6. Design complete in Nov Construction started in early Noise control added to project with change order of $343, Construction complete in Aug Odor testing completed in Sept and community surveys finished in May 2004

5 Primary Findings of Year 2000 Odor Study Primary odor sources were identified as Influent screen and grit building Grit tanks and grit room Influent channels to activated sludge process Activated sludge process

6 West County WTP Odor Sources Grit Building Aeration Basins (5%) & Channels (7%) Grit Tanks & Channels (4%) Screen Building (80%)

7 Primary Findings of Noise Study Primary noise sources were identified as the existing blower building, RAS building, diffused air piping and site transformer Noise control would be required for new odor control fans proposed, as well Noise reduction goal for plant were 3-5 dba near residences (requires reducing major individual sources by 10 dba)

8 Odor Control Systems Installed at the West County WWTP.

9 Existing West County WTP Odor Control Improvements Aeration Basin Biofilter Screen Building & Carbon Adsorber Conversion to Fine Bubble Aeration Grit Facilities Containment Aeration Basin Influent Channel Exhaust fan for grit tanks

10 Carbon Adsorber for Screen Bldg. 14,000 cubic feet per minute of air treated from lower level of screen room

11 Cover All Influent Channels and Grit Tanks

12 Treat Air from Covered Grit Tanks with Activated Sludge Diffusion Basins converted to fine bubble diffusers to save energy and reduce odors Odors are absorbed and oxidized

13 Cover Aeration Basin Influent Channels and Treat Air 5,900 cfm modular biofilter to treat air from under the covers All influent channels covered and air ducted to biofilter A biological process to treat odors

14 Noise Control Systems Installed at the West County WWTP are

15 Additions to West County WTP Noise Control Improvements New Sound Attenuating Louvers at RAS Building New Noise Silencer and barrier for the Aeration Basin Biofilter 17 Noise enclosure for odor control fan New Noise Abatement louvers and barrier for the Blower Building New Screen Building Noise Control for the roof top fans

16 Noise control for Biofilter Fan Sound barrier walls on 3 sides of fan Silencer on the exhaust duct

17 Aeration Blower Building Noise Control Sound attenuating louvers installed on outside Noise barrier wall Full enclosure for the new exhaust fan that pulls air from the grit tanks to the aeration blowers

18 Noise Control for Fans on Roof of Screen Building

19 Results of Follow-up Odor Testing Plant odor testing completed in May, 2003 verified significant improvements in odor emissions after odor control Carbon adsorber, biofilter and activated sludge diffusion odor control systems performed excellently Community odor surveys conducted in September, 2003 and again in May, 2004 revealed goals attained in reducing frequency and intensity of odors in residential areas

20 West County WTP Hydrogen Sulfide Emissions Pounds per day Hydrogen Sulfide Before After Hydrogen Sulfide Emissions are reduced by 97% as a result of odor control project

21 West County WTP Odor Emissions OER (cfm*dt) 30,000,000 25,000,000 20,000,000 15,000,000 10,000,000 5,000,000 0 Odor Emission Rate Before After Odor emissions are reduced by 87% as as result of the odor control project

22 Summary of Follow-up Community Six surveys conducted at 12 monitoring stations after odor control showed one faint odor from WCWTP one time Before odor control, plant odors detected 20% of time and were sometimes annoying intensity Odor Survey

23 Odor Dispersion Modeling Models used to predict odor levels and the frequency they may occur in community before odor control Models were used to plan odor control project to achieve goals Now. models are used to show improvements and concurrence with community odor survey results

24 Note peak DT is 200 at plant boundary Peak Odors (DT) Before Odor Control

25 Note DT reduced to 20 at plant boundary Peak Odor Levels (DT) After Odor Control

26 Note frequency greater than 500 at boundary Frequency of Occurrence Per Year Before Odor Control

27 Note frequency less than 50 at plant boundary Frequency of Occurrence Per Year After Odor Control

28 Results of Follow-up Noise Testing Noise emissions from individual sources reduced by dba Noise from plant at nearby residences reduced by 6 dba Plant inaudible relative to all other ambient noises, with possible exception of a resident adjacent to transformer Noise consultant concluded plant site is acceptably quiet

29 Summary of Meeting MSD is pleased with results of odor and noise control system performance testing MSD wants to continue being a good neighbor and solving nuisances What do you think of odor and noise situation now?