Biofilm on MBBR media.
I still like and am fascinated by trickling filter wastewater treatment systems. A simple trickling filter is a tank or tower packed with media on which biofilm grows. Trickling filter biofilm is just like the biofilms you find on Rotating Biological Contact (RBC), MBBR, and any type system where you have a support matrix for biofilm growth.
In an old tricking filter, you can see how biomass develops as the wastewater moves through the media. Early stages have heterotrophic bacteria that remove soluble BOD. Protozoa in highly loaded sections favors amoeba and flagellates. As souble BOD drops and oxgyen increases, you start to see develoment of higher indicator protozoa and appearance of slower growing bacteria such as nitrifiers and sulfur oxidizers.
Pros of Biofilm Systems
In an old tricking filter, you can see how biomass develops as the wastewater moves through the media. Early stages have heterotrophic bacteria that remove soluble BOD. Protozoa in highly loaded sections favors amoeba and flagellates. As souble BOD drops and oxgyen increases, you start to see develoment of higher indicator protozoa and appearance of slower growing bacteria such as nitrifiers and sulfur oxidizers.
Pros of Biofilm Systems
- Can support more biomass than suspended growth systems in a given tank/clarifieSor configuration
- Effective for allowing slow growing organisms such as nitrifiers to develop
- Biofilm offers some protection against hydraulic stress (washout) and limited toxic shock (pH, inhibitory chemicals)
- Less operator action required than suspended growth
- Effective for pre-treatment of high strength waste (roughing filters)
- Can be fouled by Fats, Oils, Grease (FOG) - high FOG can "coat" the biofilm
- Less ability to change operations (MCRT, F/M) than suspended growth
- Favors filmentout forms that can be difficult to remove with gravity solids separation
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