Title: Types of Biofilters: Advantages
1Types of BiofiltersAdvantages Disadvantages
- Timothy A. Hovanec, Ph.D.
- Chief Science Officer
- Marineland Aquatic Research Labs
- 6100 Condor Cr.
- Moorpark, CA 93021
- 805.553.4446 fax 805.529-0170
- hovanec_at_marineland.com
2Definitions
- Biofilter - The physical location where
nitrification takes place - Nitrification - The oxidation of ammonia to
nitrite and subsequent oxidation of nitrite to
nitrate by microorganisms
3Goal of a Perfect Biofilter
- Provide a high surface area per volume for the
nitrifying bacteria - Maintain a thin nitrifying biofilm
- Does not clog smothering the nitrifiers
- Low maintenance requirement
- Lower operating cost
4Sewage Treatment Facilities
- However -
- Much higher ammonia loading TAN gt 50 mg/L
- Much higher organic loading SS gt 750 ml/L
- Single pass system
5Biofilter Types and Classification
6Rapid Sand Filter
Main purpose - generally to maintain water clarity
7Sand Filters
- Advantages
- Long history in the industry - known
- Easy to operate
- Easy to construct
- Disadvantages
- Requires large water pumps
- Operation smothers the nitrifying biofilm
- Needs frequent backwashing
8Trickle Filters
9Trickle Filters
- Disadvantages
- Uneven surface wetting
- May promote solids retention be hard to clean
- Advantages
- Good air exchange
- Simple to construct
- Almost any material will work
10Rotating Biological Contractor- RBC
11Industrial RBC
- Advantages
- Good air exchange
- Least maintenance of all biofilters
- Automatically maintains a thin biofilm
- Most efficient Biofilter
- Disadvantages
- No solids removal
- Have to maintain rotation
- Needs space
12Fluidized Beds
13Cut Away of Fluidized Bed
14Fluidized Beds
- Advantages
- Constant movement of beads promotes thin biofilm
- Large surface for nitrification
- Disadvantages
- Hard to maintain constant bead movement
- Beads tend to stick together
- Loss of Beads from the filter
- May promote growth of heterotrophic bacteria
15Bead Filters
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18Traditional and Tidepool (RBC) - skimmer GAC
Berlin - skimmer, no GAC Jaubert - no skimmer,
no GAC
19Filter Comparison
20Biofilm micro-electrode probing
21Oxidation of 1mg Ammonia
22Optimal Water Conditions
- Temperature
- range 5 to 50 C
- optimal 25 to 30 C
- pH
- range 5 to 10
- optimal 7 to 8.5
- Particulate organics nitrifiers do not mix
23Some Case Studies
- Greiner Timmons. 1998. AE 18189-200
- Trickle filter nitrification rate 7.5x than
downflow microbead filter - Nitrification not affected for hydraulic loading
rates between 469 and 1,231 m3/m2/day - Biofilm growth on the microbeads expanded the
media volume between 15 and 32 - Sastry et al. AE 1998. AE 19105-117
- Studied bubble washed bead filters at 3 loading
rates (16, 24, and 32 kg/day/m3 of beads - to maintain DO gt 2mg/L needed flow gt 50
L/min/kgfeed/day - Al-Hafedh et al. 2003. AE 29139-154
- compared scrub pads, plastic hair rolls,and PVC
pipe - hair rolls best, scrub pads clog, pipe was a good
inexpensive alternative
AEAquacultural Engineering www.aesweb.org
24Ammonia Oxidation Rates
25Which Biofilter is the Best?
- Miller and Libey. 1985. J. World Mari. Soc.
16-158-168 TAN removal efficiencies - RBC 74-83
- Trickle Filter 23-51
- Fluidized Bed 8 - 32
- Westermann et al 1996. AE 39723-727
- RBC most reliable
- Bead Filter high CO2 and TAN
- Fluidized Bed clogged, beds packed
- Sand Filters clogged, poor water quality, high
maintenance