Introduction. Module 15: Unit Processes for Stormwater Treatment and the Development of Critical Source Area Controls

Transcription

1 Introduction Module 1: Unit Processes for Stormwater Treatment and the Development of Critical Source Area Controls Robert Pitt Department of Civil and Environmental Engineering University of Alabama Tuscaloosa, AL 3487 Pollutants in stormwater are major contributors to degradation of urban streams and rivers. Nutrients, organic matter, solids, and trace heavy metals are of concern. Knowledge of the fate of pollutants and their association with different particle sizes essential for design of stormwater treatment. A heavy metal s toxicity, bioavailability, bioaccumulation, mobility, and biodegradability can depend on the chemical species. Critical source area controls are important components of a comprehensive stormwater management program Pollution prevention, outfall controls, better site design, etc., are usually also needed In contaminated areas, infiltration should only be used cautiously, after pretreatment to minimize groundwater contamination Large parking areas, convenience stores, and vehicle maintenance facilities are usually considered critical source areas. 1

2 Storage yards, auto junk yards, and lumber yards along with industrial storage areas, loading docks, refueling areas, and manufacturing sites. Common Stormwater Controls Stormwater Unit Processes Public works practices (drainage systems, street and catchbasin cleaning) Sedimentation Infiltration/biofiltration Critical source area controls Public education Vacuuming and brushing Evapotranspiration and evaporation Chemical volatilization Reuse on site Infiltration Sedimentation Screening or filtering Floatation Flocculation and coagulation Scour Soil sorption Plant sorption/phytoremediation Biochemical reactions Ion exchange and sorption 2

3 Design Modifications to Enhance Control of Toxicants in Wet Detention Ponds Catchbasins and Catchbasin Cleaning Settling of fine particulates Photo-degradation (enhanced vertical circulation, but not complete mixing that can scour sediments) Aeration Floatation (subsurface discharges) to increase trapping of floating litter Vactor TM used to clean sewerage and inlets Modified inlet to create catchbasin, Ocean County, NJ Proprietary Stormwater Controls (Hydrodynamic Devices) that use Settling for Treatment and have been Successfully Modeled in WinSLAMM Downstream Defender Vortechs Stormceptor Select bypass option in catchbasin controls to describe hydrodynamic device bypass 3

4 HydroInternational UpFlo TM Ponds and filters have been used to treat stormwater in some areas Upflow Filter can be evaluated in WinSLAMM Bar screens and chemical addition are also used at some locations for stormwater treatment Treatability Testing and the Development of Stormwater Control Design Criteria Particle sizes and settling rates Relative toxicity after different unit processes Laboratory-scale and field pilot-scale tests Full-scale tests 4

5 Particle Size Analyses Using Video Microscope and Computer Particle Size Analyses Using Cascading Sieves Micrograph of Road Surface Sediment Washoff Particle Size Analyses Using Coulter Counter Multi-Sizer 2 Approx. 1 µm long

6 Typical Stormwater Particle Size Distributions for Outfall Samples Coulter Counter Multi-Sizer 3 used to measure particle size distribution of solids up to several hundred micrometers. Larger particles (up to several mm) are quantified using sieves. Measured Particle Sizes, Including Bed Load Component, at Monroe St. Detention Pond, Madison, WI Particle Size Distribution of Street Dirt Pitt

7 Particle Settling Rates; Stoke s and Newton s Laws Azur s Microtox Unit used for Relative Toxicity Measurements Toxicity using Microtox Test System 7

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9 Atomic Adsorption Spectrophotometer (AAS) With Graphite Furnace, Used for Ultra Low Level Measurements of Heavy Metals Gas Chromatograph/Mass Spectrophotometer (GC/MSD) used for Organic Toxicant Trace Analyses Objectives To determine: 1.If particular nutrients and trace heavy metals are associated with different-sized particles in stormwater. 2. If toxicity of pollutants is related to particle size and if it can be reduced with sequential removal of particulates. 3.Develop the use of Anodic Stripping Voltammetry (ASV) to measure dissolved Zn, Cd, Pb and Cu in stormwater. Unfiltered Total Solids (1) TDS and SS (1) Metals by ICP-MS (4) Toxicity (4) Turbidity (3) ph (1) Alkalinity () Hardness (1) Total phosphorus () Chemical Oxygen Demand (1) Particle size distribution () Min. Needed: 22 ml Original Sample Cone splitter: fractions of 1L ea , 1, 2, 1 µm 2µm 16µm (222mL min. each).4µm Total Solids (1) Metals by ICP-MS (4) Toxicity (4) Turbidity (3) ph (1) Total phosphorus () Chemical Oxygen Demand (1) Min. Needed: 222 ml each fraction (Seven fractions; 272 ml needed for 16µm fraction) UV Irradiation Toxicity Sequential Extraction (Min. 3mL needed) Metals by ASV Metals by ASV Chelex- 1 UV Metals by ASV 9

10 Dekaport/USGS Cone Splitter (Teflon and stainless steel) Side Top Bottom Cone Splitter Large sample volume (about L) separated into subsamples using Delrin cone splitter. The sample is first poured through a 1 µm screen to remove leaves and grass clippings, and coarse sediment that would clog splitter. This captured material is also weighed. Before After After Delrin Cone Splitter Trials Trial Outlet# ,2 93mL 93mL 94mL 3, , , , AVERAGE 96.mL 966.mL 983.mL STDEV COV Dekaport/USGS Cone Splitter Test Results for Total Solids ( mg/l test sediments added to tap water having about 6 mg/l TDS) tube ID avg. std coef.var (%) first second avg std coef.var (%)

11 UV Light Exposure Dekaport cone splitter used to separate sample into smaller volumes for different sieve analyses. All-plastic vacuum filtering setups are used with a series of polycarbonate membrane filters (1,, 2, 1,.4 µm) to supplement sieves. Effluent after filtering analyzed for a wide variety of constituents. Dissolved Metals using ASV Square Wave Stripping Voltammetry chosen (rapid). Allows for the determination of multiple elements in one solution. Very low detection limits can be obtained depending upon deposition time. Standard additions used to determine unknown concentrations. Anodic Stripping Voltammetry Metal ions concentrated onto hanging drop mercury electrode by reduction to metallic state: Mn + + ne - + Hg M(Hg) 11

12 Pb Cu Cd Zn Overlay of voltammograms for 1-9 µg/l all metals (in increments of 1 µg/l) using SWSV and min deposition. Cummulative Mass of Particulate Solids (% Smaller than Size Indicated) Particle Size Distributions Suspended Solids Particle Size (µm) 12

13 Total Phosphorus Tuscaloosa, AL, Stormwater Outfall Samples Residual stormwater concentrations after removal of particles larger than size indicated Potency Factors of Tuscaloosa, AL, Stormwater Outfall Particulates (mg metal/kg SS) UV Light Exposure Particle size (µm) Copper Iron Lead Zinc >2 29, to 2 2,1 22, 38 3, 4 to 16 1,3 1, 23 2,1 1 to , 23 1,6 2 to 1 4,7 19, 89 14,.4 to 2 2,9 29, 2 14, 13

14 p =.4 p =.7 Average increase of 69% Average increase of 62% Use of ASV with Chelex resin Purpose: to determine concentration of metals in ionic form versus those associated with complexes. Resin removes ionic forms of metals. UV light releases metals from organic complexes. Therefore, using Chelex + UV allows for quantification of ionic forms, organic complexes and inorganic complexes. g Chelex-1 resin per 1mL sample. Shake vigorously on shaking table for 1 hour then re-filter. 14

15 Filtered Sample Ionic and Colloidal Associations High levels of pollutant reduction require the capture of very fine particulates, and likely further capture of dissolved pollutant fractions. Analyte % Ionic % Colloidal Magnesium 1 Calcium Zinc Iron 97 3 Chromium 94.. Potassium Lead Copper Cadmium 1 9 Most of the dissolved stormwater metals are in ionic forms and are therefore potentially amenable to sorption and ion-exchange removal processes Example Stormwater Lead and Copper Reductions using Chemical Coagulation and Precipitation Lead Copper Design Modifications to Enhance Control of Toxicants in Wet Detention Ponds % reduction Toxicity Alum usually had adverse toxicity effect, while ferric chloride with microsand gave best overall reductions. Buffered Aluminum Sulfate (mg/l) FeCl 3 additions Turbidity Settling of fine particulates Photo-degradation (enhanced vertical circulation, but not complete mixing that can scour sediments) Aeration Floatation (subsurface discharges) to increase trapping of floating litter 1

16 after aeration after UV after act. carbon after um after 2 um after 1 um after FeCl initial Development of Stormwater Control Devices using Media Pilot-Scale Treatment Tests using Filtration, Carbon Adsorption,UV Disinfection, and Aeration Multiple treatment processes can be incorporated into stormwater treatment units sized for various applications. Gross solids and floatables control (screening) Capture of fine solids (settling or filtration) Control of targeted dissolved pollutants (sorption/ion exchange) Concentration With Fe Cl Copper reductions after different treatment stages Oxmoor Stormwater Toxicant Control Toxicant removal mechanisms include sedimentation, biodegradation, volatilization, sorption onto soil particles, and chemical oxidation and hydrolysis These processes are available in many urban runoff controls, but modifications should be made in their designs to increase their toxicant removal efficiencies 16

17 Stormwater Toxicant Control, cont. The most effective treatment processes included: - settling in 1 m column for at least 24 hours (4 to 9% reductions), - screening through 4 micrometer sieves (2 to 7% reductions), and - aeration and or photo-degradation for at least 24 hours (up to 8% reductions). Pilot-scale filters examining many different media. Lab and pilot-scale filters and multichambered treatment train (MCTT) 17

18 The Multi-Chambered Treatment Train (MCTT) The MCTT was developed to control toxicants in stormwater from critical source areas. Pilot-scale monitoring indicated median reductions of >9% for toxicity, lead, zinc, and most organic toxicants. Suspended solids were reduced by 83% and COD was reduced by 6%. Full-scale installations substantiated, or showed improved reductions. The MCTT most suitable for use at critical source areas, such as vehicle service facilities, industrial storage and equipment yards, convenience store parking areas, vehicle maintenance areas, and salvage yards. The MCTT is an underground device and is typically sized between. to 1. percent of the paved drainage area. The MCTT is comprised of three main sections: MCTT Cross-Section - an inlet having a conventional catchbasin with litter traps, - a main settling chamber having lamella plate separators and oil sorbent pillows (and sometimes aeration/dissolved air floatation), and - a final chamber having a mixed sorbent media (usually peat moss and sand). Long-term continuous simulations are used to size the unit for specific toxicant reduction goals based on local rain conditions 18

19 Example MCTT Sizing Curves Milwaukee, WI, Ruby Garage Public Works Maintenance Yard Minocqua, WI, MCTT Test Area Minocqua MCTT test site is a 1 ha (2. acre) newly paved parking lot for a state park and commercial area. Located in a grassed area and was a retro-fit installation. Installed capital cost was about $9, and included the installation of 3. m X 4.6 m (1 ft X 1 ft) box culverts used for the main settling chamber (13 m, or 42 ft long) and the filtering chamber (7.3 m, or 24 ft long). Costs are about equal to the costs of installation of porous pavement (about $4, per acre of pavement). 19

20 Minocqua, WI, MCTT Installation Minocqua, WI, MCTT Inlet Chamber Minocqua, WI, MCTT Sedimentation Chamber Minocqua, WI, MCTT Filter Chamber 2

21 Maintenance of MCTT Units Major maintenance items for MCTTs include removal of sediment from the sedimentation basin when the accumulation exceeds 1 mm (6 in.) and removing and replacing the filter media about every 3 years. After two wet seasons, the total accumulated sediment depth at the Caltrans installations was less than 2 mm (1 in.), indicating that sediment removal may not be needed for about 1 years. MCTT Maintenance (cont.) The sorbent pillows were replaced annually, or sooner if darkened by oily stains. Weekly general inspections were conducted during the wet season for such things as trash removal from the inlet and outlet structures. Monthly inspections were also conducted to identify and correct damage to inlet and outlet structures, and to remove graffiti. Because the Caltrans MCTT test units were above ground and not initially covered, the permanent pools were available for mosquito breeding. The Via Verde site was finally completely covered with netting to prevent mosquito access. Pilot-Scale MCTT Pollutant Control by Chamber for Selected Toxicants Pilot-Scale Test Results Main Settling Chamber Peat/Sand Chamber Overall Device Microtox TM Lead Zinc Pyrene 1-1 Bis (2- ethylhexyl) phthalate

22 Pilot-Scale Test Results Wisconsin Full-Scale MCTT Test Results (median % reductions and median effluent quality) Suspended Solids Phosphorus Copper Lead Zinc Benzo (b) fluoranthene Phenanthrene Pyrene Milwaukee (1 events) 98 (< mg/l) 88 (.2 mg/l) 9 (3 µg/l) 96 (1.8 µg/l) 91 (<2 µg/l) >9 (<.1 µg/l) 99 (<. µg/l) 98 (<. µg/l) Minocqua (7 events) 8 (1 mg/l) >8 (<.1 mg/l) 6 (1 µg/l) nd (<3 µg/l) 9 (1 µg/l) >7 <.1 µg/l) >6 (<.2 µg/l) >7 (<.2 µg/l) Caltrans Full-Scale MCTT Test Results Suspended solids TKN Total Phosphorus Copper Lead Zinc Total petroleum hydrocarbons Fecal coliforms Mean % reductions and mean effluent quality 8 (6 mg/l) 3 (.82 mg/l) 39 (.11 mg/l) 38 ( µg/l) (3 µg/l) 8 (13 µg/l) 8 (21 µg/l) 82 (171 MPN/1 ml) Water Environment Research Foundation (WERF) project on Metals Removal from Stormwater Main Project Goals: Contribute to the science of metals capture from urban runoff by filter media and grass swales. Provide guidelines to enhance the design of filters and swales for metals capture from urban runoff. Media Filtration Goals: Characterize physical properties Assess & quantify ability of media to capture metals Rank media & select media for in-depth study Evaluate effect of varying conditions on rate and extent of capture Laboratory- and pilot-scale studies of pollutant removal Disposal issues of used media (using TCLP) 22

23 Treatment Media Examined during WERF Study Traditional Media Ion Exchange Resin Granular activated carbon (GAC) Sand Metals Examined - Copper, Cadmium, Chromium, Zinc, Lead, and Iron Other Low Cost (disposable) media Compost 2 Zeolites Iron Oxide Coated Sand Agrofiber Cotton Mill Waste Peat-Sand Mix Kudzu Peanut Hull Pellets Laboratory Media Studies Rate and Extent of Metals Capture Capacities (partitioning) Kinetics (rate of uptake) Effect of ph & ph changes due to media, particle size, interfering ions, etc Packed bed filter studies Physical properties and surface area determinations Cation Exchange Capacities for Different Media Contaminant Losses during Anaerobic vs. Aerobic Conditions between Events Peat Moss Compost Activated Carbon Zeolite Cotton Waste Agrofiber Sand CEC (meq/1 g)

24 Pilot-Scale Downflow Filtration Setup Media Investigated: Activated Carbon Zeolite Sand Lightweight Sand Loamy Soil Municipal Leaf Compost Peat Moss Kenaf Fiber Cotton Textile Waste Pilot-Scale Filtration Setup after Pre-Treatment by Stormwater Pond 24

25 Clogging Problems Originally Addressed by Pre- Treatment. What about Upflow Filtration? Expected Advantages: Reduced Clogging: Sump collects large fraction of sediment load. Prolonged Life: Particles trapped on the surface of the media will fall into the sump during quiescent periods. High Flow Rates: Since large and heavy solids will be removed by way of settling in the sump prior to encountering the filter, the filters can be operated at higher flow rates. Upflow Filter Design with Sump No sump With sump Upflow Filters for Metals Removal Particulate Solids: Good removal (>9%) for all media for all runs. Particulate Metals: Generally 8-1% removal for Pb, Zn, Cd, and Fe and 6-9% removal for Cu and Cr. Peat had the best removal rates for particulate bound metals. Removal rates of compost and zeolite were about the same. Sump Pressure gage Upflow filter insert for catchbasins Upflow Filter TM patented Main features of the MCTT can be used in smaller units. The Upflow Filter TM uses sedimentation (22), gross solids and floatables screening (28), moderate to fine solids capture (34 and 24), and sorption/ion exchange of targeted pollutants (24 and 26). Successful flow tests using prototype unit and mixed media as part of EPA SBIR phase 1 project (controlled lab tests). Phase 2 tests recently completed (field tests), and 1. ETV testing just starting. Flow (gpm) 8 to 9% removal of dissolved zinc using sand/peat upflow filtration Headloss (inches) % Remova l Residence Time, minutes Series1 Series2 Series3 1 to 2 gpm/ft 2 obtained for most media tested 2

26 Test site drainage area, Tuscaloosa, AL (anodized aluminum roof, concrete and asphalt parking areas; total of.9 acres) EPA SBIR2 UpFlow TM Filter tests using Frankenstein 2 prototype EPA-funded SBIR2 Field Test Site Monitoring Equipment, Tuscaloosa, AL Support material and media 26

27 Mixed Media (Mn-Z, Bone Char and Peat) 3 3 Flow (gpm) y = 2.67x R 2 =.9799 Flow tests (3 gpm) for bypass capacity Head (in) Suspended Solids Removal Tests Media (each bag) Zeo+ Zeo Zeo+ Zeo Zeo+ Zeo Mix + Mix Mix + Mix Mix + Mix Flow (gpm) High (21) Mid (1) Low (6.3) High (27) Mid (1) Low (.8) Influent SS Conc. (mg/l) Zeo: Manganese-coated zeolite Mix: 4% Mn-Z, 4% bone char, 1% peat moss Average Effluent SS Conc. (mg/l) % SS reduc % Finer Upflow Filter Mixed Media Tests (Mn-coated Zeolite, Bone Char, Peat Moss) Performance Plot for Particle Size Distributions Particle Size (um) Influent PSD mg/l High Flow mg/l Mid Flow mg/l Low Flow 1 mg/l High Flow 1 mg/l Mid Flow 1 mg/l Low Flow 2 mg/l High Flow 2 mg/l Mid Flow 2 mg/l Low Flow mg/l High Flow mg/l Mid Flow mg/l Low Flow 27

28 concentration in particle size range (mg/l): 69 (and smaller) (and larger) 2.1 (and smaller) (and larger) 4 (and smaller) (and larger) to.4 µm (TDS) 6 gpm/ft 2 (or less).4 to 3 µm to 12 µm gpm/ft gpm/ft 2 (to overflow) (and smaller) (and larger) 6.1 (and smaller) (and larger) 4.4 (and smaller) (and larger) 12 to 3 µm to 6 µm to 12 µm Probability Plot of Concentration for Particle Range -.4 um Normal Probability Plot of Concentration for Particle Range.4-3 um Normal Probability Plot of Concentration for Particle Range 3-6 Probability um Plot of Concentration for Particle Range 6-12 um Normal Normal Percent mg/l Variable Influent (mg/l) Effluent (mg/l) 9 Mean StDev N AD 9 P Percent mg/l 2 2 Variable Influent (mg/l)_1 Effluent (mg/l)_1 Mean StDev N AD P Percent mg/l 6 8 Variable Influent (mg/l)_ Effluent (mg/l)_ Mean StDev N AD P Percent mg/l Variable Influent (mg/l)_6 Effluent (mg/l)_6 Mean StDev N AD P <. Percent Probability Plot of Concentration for Particle Range 3-12 um Normal 99 Variable Influent (mg/l)_2 Effluent (mg/l)_2 9 Mean StDev N AD 9 P Percent Probability Plot of Concentration for Particle Range 12-3 um Normal Variable Influent (mg/l)_4 Effluent (mg/l)_4 Mean StDev N AD P Percent Probability Plot of Concentration for Particle Range um Probability Plot of Concentration for Particle Range >24 um Normal Normal Variable Variable Influent (mg/l)_7 Influent (mg/l)_8 9 Effluent (mg/l)_7 9 Effluent (mg/l)_8 9 Mean StDev N 9AD P Mean StDev N AD P * * 1 8 * * * 12 * Percent mg/l mg/l mg/l mg/l

29 % Finer Performance Plot for Particle Size Distributions Particle Size (um) Activated Carbon Performance for Particle Size Distribution Influent PSD mg/l High Flow mg/l Mid Flow mg/l Low Flow 1 mg/l High Flow 1 mg/l Mid Flow 1 mg/l Low Flow 2 mg/l High Flow 2 mg/l Mid Flow 2 mg/l Low Flow mg/l High Flow mg/l Mid Flow mg/l Low Flow % Finer Mn Coated Zeolite Performance for Particle Size Distribution Particle Dia (µm) Bone Char Carbon Performance Plot for Particle Size Distribution High Mid Low Influent 7 to 9% SS reductions for influent concentrations >9 mg/l % Reduction 1 % Finer Particle Size (µm) High Mid Low Influent % Finer Particle Size (µm) High Mid Low Influent Influent Suspended Solids (mg/l) Effluent SS <1 mg/l whenever influent is < mg/l 1 UpFlow Filter 1 Effluent Suspended Solids (mg/l) Components: 1. Access Port 2. Filter Module Cap 3. Filter Module 4. Module Support. Coarse Screen 6. Outlet Module 7. Floatables Baffle/Bypass Influent Suspended Solids (mg/l) Hydro International, Ltd. 29

30 Upflow Filter Components 2 1 Hydraulic Characterization High flow tests 1. Module Cap/Media Restraint and Upper Flow Collection Chamber 2. Conveyance Slot 3. Flow-distributing Media 4. Filter Media. Coarse Screen 6. Filter Module Hydro International, Ltd Assembling Upflow Filter modules for lab tests Initial CFD Model Hydro International, Ltd. Results Operation during normal and bypass conditions 3

31 Draindown between events Conclusions The MCTT provided substantial reductions in stormwater toxicants (both in particulate and filtered phases) and suspended solids. The main settling chamber provided substantial reductions in total and dissolved toxicity, lead, zinc, certain organic toxicants, SS, COD, turbidity, and color. The sand-peat chamber also provided additional filterable toxicant reductions. ETV test setup at Penn State - Harrisburg The catchbasin/grit chamber is an important element in reducing maintenance problems by trapping bulk material. Conclusions (cont.) The bench-scale treatability tests conducted during the development of the MCTT showed that a treatment train was needed to provide redundancy because of frequent variability in sample treatability storm to storm, even for a single sampling site. Conclusions (cont.) Upflow filtration with a sump and interevent drainage provided the best combination of pre-treatment options and high flow capacity, along with sustained high contaminant removal rates. Possible to develop other stormwater controls that provide treatment train approach. 31

32 Constituent and units Particulate solids (mg/l) Phosphorus (mg/l) TKN (mg/l) Cadmium (µg/l) Copper (µg/l) Lead (µg/l) Zinc (µg/l) Conclusions (continued) Reported irreducible concentrations (conventional highlevel stormwater treatment) 1 to 4.2 to.3.9 to Effluent concentrations with treatment train using sedimentation along with sorption/ion exchange < to 1.2 to to 1 3 to 1 <2 References Barrett, M. Performance Summary Report for the Multi- Chambered Treatment Trains. Prepared for the California Department of Transportation. May 21. Clark, S., R. Pitt, and R. Raghavan. SBIR Phase 1 report for Upflow Filtration Treatment of Stormwater. U.S. EPA. Publication pending 23. Corsi, S.R., S.R. Greb, R.T. Bannerman, and R.E. Pitt. Evaluation of the Multi-Chambered Treatment Train, a Retrofit Water Quality Management Practice. U.S. Geological Survey. Open-File Report Middleton, Wisconsin. 24 pgs Johnson, P., R. Pitt, S. Clark, M. Urritta, and R. Durrans. Innovative Metal Removal for Stormwater Treatment. Water Environment Research Foundation. Publication pending 23. Pitt, R., B. Robertson, P. Barron, A. Ayyoubi, and S. Clark. Stormwater Treatment at Critical Areas: The Multi-Chambered Treatment Train (MCTT). U.S. Environmental Protection Agency, Wet Weather Flow Management Program, National Risk Management Research Laboratory. EPA/6/R-99/17. Cincinnati, Ohio. pgs. March Acknowledgements WERF Project 97-IRM-2 Project Manager: Jeff Moeller U.S. EPA Small Business Innovative Research Program (SBIR1 and SBIR2 plus ETV testing) Project Officer: Richard Field Many graduate students at the University of Alabama and Penn State-Harrisburg Industrial Partners (US Infrastructure and Hydro International) 32