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

2. Biological Filtration
NH3
Ammonia
NO2
Nitirite
NO3
Nitrate

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

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

5. NH3 <-> NH4+ Equilibrium

6. NH3/NH4+ NO2- Bacteria of Reaction #1 Grow Quickly 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. Biological Filtration Reaction #2
NH3
Ammonia
NO2
Nitrite
NO3
Nitrate

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

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

14. B1 B2 NH3 NO2 NO3 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
NH3
Ammonia
NO2
Nitrite
NO3
Nitrate

15. Biofiltration
The classification of heterotrophic bacteria encompasses a great number of genera/species which share the common characteristics of extracting their nourishment from the breakdown (decay) of organic matter. Biochemical oxygen demand (BOD) is largely an indirect measure of the biodegradable organic material in water. Heterotrophic bacteria reduce BOD levels, consuming oxygen in the process. About 60 percent of the organic matter consumed is converted to bacterial biomass; whereas, the balance (40 percent) is converted to carbon dioxide, water, or ammonia. Heterotrophic bacteria grow very fast, capable of doubling their population every ten to fifteen minutes. If the BOD in the water being treated is very high (> 20 mg -O2/l), the heterotrophs will quickly dominate the bead bed, overgrowing the slower growing nitrifying bacteria and consuming tremendous amounts of oxygen.
The second, yet more important, classification of bacteria is the nitrifying bacteria. These bacteria are specialists, extracting energy for growth from the chemical conversion of ammonia to nitrite and from nitrite to nitrate (Figure 3.6). Nitrate is a stable end product which, although a valuable nutrient for plants, displays little of the toxic impacts of ammonia and nitrite. Composed principally of two genera (Nitrosomonas and Nitrobacter), nitrifying bacteria are very slow growing and sensitive to a wide variety of water quality factors. It is not surprising that most bead filters used for biofiltration are managed to optimize conditions for nitrification.

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 Tell If 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

22. Propeller-washed Floating Bead Filters

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

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

26. Circulation
Aeration
Degassing
Solids Capture
Biofiltration
Inlet
Airlift

27. 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.

28. Foam Block Media
Fluidized Beds
Active Media

30. 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)

34. 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

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

37. Trickle Filter
Bioballs

38. RBC Rotating Bio Contactor

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