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Environmental Applications of Coagulants and Flocculants

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This ebook describes best practices for utilizing coagulants and flocculants in environmental applications, such as construction, mining, erosion control. and stormwater runoff.

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Environmental Applications of Coagulants and Flocculants

  1. 1. Environmental Applications of Coagulants and Flocculants How to Know Which Tool to Use ®NATURAL FLOCCULANTS
  2. 2. Table of CONTENTS What is Coagulation & Flocculation? 3 Types of Coagulants and Flocculants 6 Advantages and Disadvantages of Each Type 8 Settling velocity, shear strength, filterability Sludge density, dewater-ability Aquatic toxicity & residual testing capability What is Enhanced Best Management Practices (eBMP)s? 17 Passive, Semi-passive, Passive w/ automation, Active Treatment Environmental concerns and responsibilities
  3. 3. 3 Flocculation & Coagulation ‹‹ Removes suspended solids from water ‹‹ Large particles can be removed by filtration or settling, as practical ‹‹ Smaller, suspended particles (e.g. colloidal particles) are stabilized in suspension & difficult to remove via mechanical methods: -- Size (~0.1 to 1µm) -- Electrically charged; repel each other; stabilize the suspension -- Examples: clay, silica, iron, pigments, and even oil ‹‹ Flocculation & Coagulation destabilize colloidal particles to enhance performance of mechanical separation processes
  4. 4. 4 Coagulation - Brings Particles Together ‹‹ Coagulation - destabilization of a colloid by charge neutralization ‹‹ Destabilized particles begin to collide and create small masses –flocs or pin flocs (> 50 microns, visible) ‹‹ Requires good mix condition (e.g. static mixer) -- Particles must come close enough to collide -- Break apart the colloidal system ‹‹ Historical, metals salt coagulation (aluminum, iron, etc.) can create excess sludge and/or toxicity
  5. 5. 5 Flocculation - Improves Filterability & Settling ‹‹ Flocculation - the gathering of flocs into a network ‹‹ Anionic, cationic, neutral ‹‹ High molecular weight ‹‹ Increases floc stability ‹‹ Mixing condition essential! -- Not to break flocs Patching Bridging
  6. 6. 6 Typical Coagulants ‹‹ Metal Salts -- Alum, Ferric Chloride, etc. -- Polymerized metal salts i.e. Polyaluminum chloride (PAC), Aluminum Chlorohydrate (ACH), etc. ‹‹ Plant Based derivatives -- Lignin, tannin, starch, etc. ‹‹ Synthetic derivatives -- Polyamine, pDADMAC, etc. ‹‹ Hybrids -- Variations or combinations of chemistries ‹‹ Synthetic derivatives -- pDADMAC – can be coagulant or flocculant depending on derivatization ‹‹ Polysaccharides / natural biopolymers -- Chitosan -- Pectin, carrageenan, alginate, etc. -- Gums – guar, xanthan, plantago, etc. ‹‹ Polyacrylamides
  7. 7. 7 Molecular Weights of Coags, Flocs & Tackifiers ‹‹ FeCl3, Alum (Al2(SO4)3 ‹‹ Polymerized metal salts – PAC, ACH ‹‹ Synthetics – pDADMAC, Polyamines ‹‹ Plant based – tannin, lignin, starch ‹‹ Chitosan biopolymer ‹‹ Gums – plantago, guar, etc… ‹‹ Polyacrylamides ‹‹ 162-342 Daltons ‹‹ 150-5,000 Da ‹‹ 150-5,000 Da* ‹‹ 500-25,000 Da ‹‹ 25,000-500,000 Da ‹‹ 1,000,000-5,000,000 Da ‹‹ 1M to 30M Daltons * Some pDADMAC can act like flocculants 25k – 1.5M Da Coagulants: Inorganic and Organic Flocculants: synthetic & natural Floc builders: act as coagulants and flocculants
  8. 8. 8 Flock Characteristics ‹‹ The following pages show characteristics to look for and awareness of treatment through design when using: -- Aluminum Sulfate - Alum -- Polyaluminum Chloride (PAC) -- Polyamine -- pDADMAC Coagulant -- Plant Based Derivatives -- Natural Chitosan Biopolymer -- aPAM blend -- Polyacrylamide ‹‹ These characteristics are: settling velocity, settled density, shear strength, filterability, and retained moisture content
  9. 9. 9 Aluminum Sulfate - Alum Very fine flocks, slow to settle Medium settled density Flocs are very hard to see with naked eye while under agitation
  10. 10. 10 Polyaluminum Chloride (PAC) Slightly larger than PAC Slightly denser flocks Flocs are a little easier to see with naked eye while under agitation
  11. 11. 11 Polyamine Larger flock structure Flocks are clearly visible with naked eye Less settled density
  12. 12. 12 pDADMAC coagulant Larger flocks than polyamine Similar settled density to polyamine
  13. 13. 13 Plant Based derivatives Similar to pDADMAC flock size Denser settled solids than pDADMAC
  14. 14. 14 Biopolymer – chitosan vs. chitosan + anionic polysaccharide Chitosan denser solids than coagulants & PAM Dual biopolymer is even denser than chitosan only
  15. 15. 15 aPAM blend Large and stable flock structure Denser settled solids than straight PAM
  16. 16. 16 Polyacrylamide Largest flock structure Settled solids is more voluminous than biopolymers or PAM blends – nearly 2x more volume than biopolymers. Best if “pressed” to release excess moisture.
  17. 17. 17 Best Management Practice (BMPs) ‹‹ How the chemistry is used in environmental applications ‹‹ We’ve laid out best management practices, how the density is used for environmental applications, including: -- Passive Treatment Systems ■■ Check Dams ■■ Baffles ■■ Slope Drains -- Semi-Passive Treatment Systems ■■ Geotextile Bags ■■ Sedimentation Ponds -- Active Treatments ■■ Sand Filtration
  18. 18. 18 Passive Treatment Systems (PTS) ‹‹ Gravitational flow – not pumped ‹‹ Dry flocculant usage is primary, very little liquid flocculant used in PTS ‹‹ Variable flowrates of stormwater run-off lead to non-optimal dose rate determination -- Requires review of aquatic toxicity or have residual polymer testing capabilities ‹‹ With proper jar testing to determine dose rate – PTS can typically achieve 50-250 NTU or 75-80% reduction in Total Suspended Solids (TSS) over same BMP without flocculant addition
  19. 19. 19 Passive – check dam channels ‹‹ Rock, wattles or filter sock Images courtesy of North Carolina State University. https://content.ces.ncsu.edu/fiber-check-dams-and- polyacrylamide-for-water-quality-improvement Photo courtesy of North Carolina State University. Apply flocculant on and around wattle. Depending on % solids – flocculant can be sprinkled on wattles & matting. More contact flocculant has with turbid water the better the dosing. Flocculant
  20. 20. 20 Sediment Basins with porous baffles Flocculant is added up stream of basin or forebay. Purpose of the baffles is to disperse the energy of flowing water and allow to settle. When combined with flocculant enhancement can improve 75-80% performance on water quality.
  21. 21. 21 Case Study – Passive wattle & porous baffle sediment basin - Raleigh NC Passive: Wattle check dam and matting channel, to sediment pond with porous baffles and floating skimmer. From Left: Influent: >4000 NTUs calc’d. 5400 End of channel: 260 NTUs Skimmer effluent: 28 NTUs
  22. 22. 22 Passive - Slope Drain flocculant application Dry flocculant sock deployed inside of slope drain, allows for high agitation of flocculant - then treated water can be directed to sediment basin, vegetated buffer or check dam channel prior to discharge. Drawing courtesy of Dober Chemical
  23. 23. 23 Semi-Passive Treatment Systems (SPTS) ‹‹ Pumped water ‹‹ Known flowrate improves dose rate calculations and thus improves flocculant performance. ‹‹ Dry or liquid flocculant used – dry is more common ‹‹ With proper jar testing to determine dose rate – PTS can typically achieve 25-150 NTU or 85-95% reduction in Total Suspended Solids (TSS) over same BMP without flocculant addition ‹‹ Flocculant enhanced geotextile dewatering/filtration -- Non-woven geotextile bags typically filter down to 150-200 microns -- Woven geotextile bags typically filter down to 500-700 microns -- With correct flocculant can improve filtration 75-80% + Bottles from right to left: 1. Influent from sediment pond 450-560 NTUs 2. Directly from geobag 56-89 NTUs 3. After 50 ft of vegetative buffer 18-27 NTUs WARNING: Do NOT over pressurize!!! Unless you want to get DIRTY and WET
  24. 24. 24 Passive Treatment Systems with automation ‹‹ Gravitational flow of water ‹‹ Automated detection of flowrate and proportionally dosed liquid flocculants greatly improves dose rate calculations and thus improves flocculant performance ‹‹ liquid flocculant typically used ‹‹ With proper jar testing to determine dose rate – PTS can typically achieve 10-25 NTU or 95-99% reduction in Total Suspended Solids (TSS) over same BMP without flocculant addition
  25. 25. 25 Passive & Semi-Passive w/automation ‹‹ Sedimentation pond with forebay and weir: ‹‹ Automation unit monitors and optimal doses liquid flocculant system Forebay and settling pond w. EDD unit and PV, battery “green power” package shown. **Generators can be added to/or in replacement of green power package**
  26. 26. 26 Automation controls dosing and records results ‹‹ Can collect data every 15 seconds ‹‹ Flow activate ‹‹ Optimal dosing ‹‹ Remote monitoring capability
  27. 27. 27 Active Treatment System ‹‹ Very high quality water results. -- Typically less than 10 – 20 NTUs, often < 5 NTUs -- Secondary remediation options (ie. GAC, ion exchange or membranes) ‹‹ Proven track record of billions of gallons treated ‹‹ Flocculant must have high filterability with depth media filtration ‹‹ Allows for flow through treatment. -- Minimize storage demands -- Can be fully automated ‹‹ Biopolymer with Sand Filtration: Drawing courtesy of Dober Chemical
  28. 28. 28 ATS is custom designed for each site Photos of various parts of treatment train including ponds, settling tanks, automation, filtration and remediation equipment
  29. 29. 29 Residual testing vs. Whole Effluent Toxicity (WET) ‹‹ Current residual polymer test commercially sold for biopolymers -- Actually crosslinking, filtering and staining of polymer ‹‹ Metal test for metal salts currently available -- Polymerized metal salts may not be detectable unless specialist testing ‹‹ Some companies have protocols using clay solution to detect any floccing in treated effluent -- Not a direct detection of polymer, only looking for the “effects of the polymer” ‹‹ Florescence “dyes or tagging” of polymers has been demonstrated in scientific research, however not aware of commercially available polymers with florescent tags If no residual testing is available and product is being dosed at or near the effect concentration for coag or floc being used, then typical is batch treatment and sending treated water out to be WET tested. ‹‹ Whole Effluent toxicity testing -- 0 – 100% of treated effluent (typical 5 dilutions) is tested for acute or chronic aquatic toxicity -- acute is usually 24-96 hrs -- Chronic is typically 7 days -- Ideally 100% survivability over control
  30. 30. www.dober.com 11230 Katherine’s Crossing | Woodridge, IL 60517 Phone: 630.410.7300 | Toll Free: 800.323.4983 info@dober.com ®NATURAL FLOCCULANTS D BER
  • ElenaRanyuk

    May. 19, 2019
  • EricBradley14

    Mar. 28, 2018

This ebook describes best practices for utilizing coagulants and flocculants in environmental applications, such as construction, mining, erosion control. and stormwater runoff.

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