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Biological Filtration

Biological Filtration. Hugh S. Hammer, PhD GSCC David Cline, ACES Ron Malone, PhD LSU. NH 3. NO 2. NO 3. Ammonia. Nitirite. Nitrate. Biological Filtration. B 1. B 2. Ammonia Sources. Decomposition of uneaten feed Decomposition of fecal materials Decomposition of dead materials

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Biological Filtration

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  1. Biological Filtration Hugh S. Hammer, PhD GSCC David Cline, ACES Ron Malone, PhD LSU

  2. NH3 NO2 NO3 Ammonia Nitirite Nitrate Biological Filtration B1 B2

  3. Ammonia Sources • Decomposition of uneaten feed • Decomposition of fecal materials • Decomposition of dead materials • By product of protein (feed) metabolism

  4. Toxic More at High Temp More at High pH Less Toxic More at Low Temp More at Low pH Ammonia Exists in 2 Forms NH3 NH4+ Total Ammonia Nitrogen (TAN)

  5. NH3 <-> NH4+Equilibrium

  6. Bacteria of Reaction #1 • Nitrosomonas sp. • Nitrosospira sp. • Nitrosolobus sp. • Nitrosovibrio sp. • Nitrosococcus sp. Grow Quickly Oxidation NH3/NH4+ NO2-

  7. Chemistry of Reaction #1 • Requires Oxygen • Results in decreasing (more acidic) pH • Requires 7 grams of alkalinity (CO3-2) for each gram of ammonia (NH3) converted to nitrate (NO3)

  8. pH = -log hydrogen ion concentration

  9. pH - What Should It Be

  10. Alkalinity (Carbonate CO3-) • Stabilizes pH around pH 7-8 • Resists changes in pH (acts as a buffer) • Required by nitrifying bacteria as a carbon source for survival

  11. NH3 NO2 NO3 Ammonia Nitrite Nitrate Biological Filtration Reaction #2 B1 B2

  12. Nitrite Conversion to Nitrate • Requires oxygen • Does not change pH • Requires alkalinity

  13. Bacteria of Reaction #2 • Nitrobacter sp. • Nitrospira sp. • Nitrospina sp. • Nitrococcus sp. Grow Slowly Oxidation NO2- NO3

  14. NH3 NO2 NO3 Ammonia Nitrite Nitrate What About Nitrate? • Non toxic in most fish up to 300 ppm • Easily solved via water change • Also managed through addition of plants • Can be toxic for many invertebrates (i.e. shrimps) B1 B2

  15. Biofiltration

  16. Optimal Nitrification Conditions • pH 7.5 • High Dissolved Oxygen • Alkalinity CO3- (Carbon Source) • Surface Area (Media) • Food (ammonia and nitrite) • Low Light (Light inhibits growth) • Ammonia oxidizing bacteria grow fast • Nitrite oxidizing bacteria grow slowly

  17. How Can You TellIf Your Filter Is Working ?

  18. Filter Media

  19. Bead Filters and Drop Filters • Probably the industry standard • Both mechanical and biological filtration • A type of fluidized bed filter • Space saving (consolidated approach) • Can be expensive • Drop filters are great for saving water, they concentrate solids • Drop filters don’t clog easily

  20. Biofiltration

  21. Propeller-washed Floating Bead Filters

  22. Filter Mode Drop Filters : Low Water Loss Floating Bead Bioclarifiers Air Bleed Builds Charge Settled Backwash Waters returned to system

  23. Backwash mode Drop Filters : Low Water Loss Floating Bead Bioclarifiers Released Air Washes Beads Internal Sludge Capture

  24. Circulation Aeration Degassing Solids Capture Biofiltration Inlet Airlift

  25. Fluidized Bed Filters • Can use any type of media (sand and beads are most common) • Uses a mixing media/water matrix • Great biological filtration • Bead filters are a type of fluidized filter that also accomplish solids capture. • Also called submerged filters when large void volume media is used.

  26. Foam Block Media Fluidized Beds Active Media

  27. Fluidized Sand Bed Filters • THESE ARE NOT RAPID SAND FILTERS • Advantages: • Tremendous surface area (the most) • Nitrite eating bacteria grow great • Best biological filters • Huge biological loads • Aquarium industry gold standard • Disadvantages: • Heavy, may require multiple pumps during power outages • Bacteria die quickly from O2 deprivation during power outages • MUST have all of the solids out of the water (solids can cause serious problems with channeling)

  28. Trickle Filters, Packed Towers, Bio-wheels, RBCs • Media is not continually submerged but moist • Efficiency depends on water distribution • Inexpensive to build • Good biological filtration • Not good for solids removal (hard to clean) • Great for aerating water and stripping carbon dioxide • Will change the temperature of water (cools it off, sometimes good and sometimes not) • Some RBCs are very expensive but are great biofilters

  29. Packed Tower • Adds Oxygen • Removes Carbon Dioxide • Biological Filtration • Easy to construct

  30. Trickle Filter Bioballs

  31. RBC Rotating Bio Contactor

  32. Screen + Trickle Filter + Fluidized Bed Filter = Wet Dry Filter Consolidated approach Good for small loads (aquariums) Advantages and Disadvantages of all the components Wet Dry Filters

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