The Ability to Remove Pathogens Results from the International BMP Database

Transcription

1 The Ability to Remove Pathogens Results from the International BMP Database Presented by Jon Jones, P.E., Wright Water Engineers, Inc. Eric Strecker, P.E., Geosyntec Consultants

2 Fecal Coliform by Land Use National Stormwater Quality Database (Pitt et al. 2004) Values in Red are Medians.

3 BMP Database Overview BMP Database includes 470 BMP monitoring studies (about 500 EOY), including significant green infrastructure/lid and traditional BMPs From , a key focus has been to better integrate green infrastructure through: Monitoring Guidance (Updated) Reporting Protocols Analysis Protocols Data Acquisition

4 BMP Summary New Green Infrastructure BMP Categories: Bioretention Green Roofs Rainwater Harvesting Site-scale LID Adding more studies is an ongoing objective New version posted in July 2011 BMP Category Bioreten)on # 24 Deten)on Basin (dry basin) 39 Green Roof 11 Biofilter (swales & buffer strips) 82 Infiltra)on Basin 1 Manufactured Device 78 Media Filter 35 Maintenance Prac)ce 28 Porous Pavement 26 Percola)on Trench/Well 11 Reten)on Pond (wet pond) 65 Wetland Basin 29 Wetland Channel 17 LID (site- scale) 1 Composite System (series) 21 Other 2 Total 470

5 Land Use Inventory of BMP Database Light Industrial* 21 Heavy Industrial* 8 Roads/Highways** 56 Park & Ride 7 Low Density Residential 34 Open Space 43 Medium Density Residential 47 Open Space (Manicured) 3 High Density Residential 29 Vegetable Farming 4 Multi-Family Residential 28 Forest 14 Office Maintenance Station 15 Commercial 86 Rangeland 14 Automotive Services 8 Retail 12 Orchard 3 College Campus 15 Restaurants 6 Other/Unknown 41 *14 of the Industrial Sites have Bacteria Data **41 of the Roads/Highways Sites have Bacteria Data

6 Potential Strategies for Passive BMP Approach Source Controls: Control animal life on-site Eliminate pooled waters (i.e. trapped catch basins, depression storage in drainage systems) Pond or drainage system sediment removal Bacteria concentration reductions via treatment Volume control (reduce frequency of discharge) via infiltration, evapotranspiration, harvest and use

7 BMP Database Findings Regarding Fecal Indicator Bacteria Most BMP studies have historically reported fecal coliform; recent studies report E. coli and enterococcus. Additional bacteria data have been added to BMP Database since 2010 analysis was completed. Indicator Type Entero- coccus Total Studies July 2011 E. coli Fecal Coliform Fecal Strep Total Coliform

8 BMP Performance DB = Deten)on Basin GS = Grass Swale MD =Manufactured Device MF =Media Filter RP = Reten)on Pond

9 Overview of Exceedance Frequency Analysis for Fecal Coliform BMP Category (7-12 studies per category) Deten)on Basin Grass Swale Manufactured Device Media Filter Reten)on Pond Primary Contact Benchmark (Geometric Mean) 200 CFU/ 100 ml CI = Confidence Interval (95%) % Inflow Values Greater Than Threshold % OuHlow Values Greater Than Threshold 83% 65% CI: 77% - 90% CI: 57% - 73% 85% 93% CI: 77% - 94% CI: 87% - 99% 98% 99% CI: 94% - 100% CI: 97% - 100% 74% 59% CI: 65% - 83% CI: 49% - 69% 61% 36% CI: 49% - 74% CI: 24% - 48% Blue text highlights BMP types where CI do not overlap.

10 Individual BMP Performance (multiple plots by BMP category)

11 Industrial BMP Sites with Bacteria Data in the BMPDB 1,000, ,000 Fecal Coliform per 100 ml 100,000 10,000 1, E. coli per 100 ml 10,000 1, BS_Bioswale Native East BS_Bioswale Non-Native W IB_SunValleyInfiltration RP_Central Market Wet Po RP_Shawnee Ridge Retenti RP_WC- WP BMP Study Name WB_DGapWetland WB_Water Garden 1 BS_Bioswale Native East BS_Bioswale Non-Native W RP_Surge Basin WB_East Habitat Area WB_Polishing Ponds BMP Study Name WB_Water Garden WB_West Habitat Area

12

13 Reasons for Variability in Performance

14 Volume Reduction Volume reduction goals for meeting bacteria limits end of pipe would be to reduce frequency of discharges Volume is increasingly regulated as a primary or surrogate constituent of concern Volume reduction goals (or Retain on site ) are explicit in various recent regulations (e.g., EISA Section 438, TMDLs, some MS4 permits and state standards)

15 Volume Reduction Performance Summary Practice Level 2.5 BioretenLon (with Underdrains) 2.5 DetenLon Basins (Grass Lined) OuHlow (watershed- cm) OuHlow (watershed- cm) Inflow (watershed- cm) Inflow (watershed- cm) Screened Out Datapoints (n=33) Recommended Analysis Dataset (n=399) Ou^low = Inflow Screened Out Datapoints (n=56) Recommended Analysis Dataset (n=114) Ou^low = Inflow

16 Volume Reduction Performance Summary Practice Level Filter Strips Grass Swales OuHlow (watershed- cm) OuHlow (watershed- cm) Inflow (watershed- cm) Inflow (watershed- cm) Screened Out Datapoints (n=239) Recommended Analysis Dataset (n=243) Ou^low = Inflow Screened Out Datapoints (n=43) Recommended Analysis Dataset (n=83) Ou^low = Inflow

17 Volume Reduction Performance Summary Practice Level RetenLon (Wet) Ponds Wetland Basins/Wetland Channels OuHlow (watershed- cm) OuHlow (watershed- cm) Inflow (watershed- cm) Inflow (watershed- cm) Screened Out Datapoints (n=118) Recommended Analysis Dataset (n=297) Ou^low = Inflow Screened Out Datapoints (n=306) Recommended Analysis Dataset (n=114) Ou^low = Inflow

18 Volume Reduction Performance Summary Practice Level Big-picture analysis is potentially useful, however limitations should be recognized BMP Category # 25 th Percentile Median 75 th Percentile Avg. Biofilter Grass Strips 16 18% 34% 54% 38% Biofilter Grass Swales 13 35% 42% 65% 48% Bioretention (w/ underdrains) 7 45% 57% 74% 61% Detention Basins Grass Lined 11 26% 33% 43% 33%

19 Example Individual Study Analysis Site Level Total Inflow and Outflow Within Bin (L) 350, , , , , ,000 50,000 0 Greensboro G1 Bioretention 1.2 m amended soil; underdrains; 15 cm gravel layer Average Inflow and Outflow within Bin (watershed-cm) Inflow Bin (watershed-cm) Sum of Inflow (L) Average Inflow (watershed-cm) Sum of Outflow (L) Average Outflow (watershed-cm) Study Submitted by Dr. William Hunt, NC State

20 Selected Conclusions for Volume Reduction Normally-dry vegetated BMPs (filter strips, vegetated swales, bioretention, and grass lined detention basins) appear to have substantial potential for volume reduction on a long-term basis, on the order of 30 percent for filter strips and grass-lined detention Basins, 40 percent for grass swales, and greater than 50 percent for bioretention with underdrains Also can reduce frequency of discharge (with good design) Variability in volumetric performance between studies indicates that design attributes and site conditions likely play keys role in performance.

21 Conclusions Meeting Recreational Standards In most cases, an active system would be required to consistently meet standards (up to some design storm) Active systems would require significant pre-treatment, storage, pumps, etc., greatly increasing energy costs, maintenance, chemicals etc. Offsite sources in watershed must be considered. Realistic solutions need to be developed that recognize natural sources in a variety of settings. One size does not fit all. Site hydrology/design flow critical. May be able to address other stormwater problems concurrently.

22 Question and Answers Technical Memorandums (Dec 2010): Bacteria and Volume Control Download from