The biological filter has one primary function in aquaponics and that is to neutralize the toxic ammonia and nitrite and is done through a process known as nitrification.
An aquaponic MBBR reduces the ammonia and nitrite concentrations in aquaponics by allowing nitrifying bacteria to colonize within the media which are constantly being moved around by air bubbles produced by an air pump.
The food we feed our fishes contains protein. The protein is then metabolized and excreted through the fish gills primarily in the form of ionized ammonia. If this ammonia is allowed to build can cause the fish to die.
This is because the mechanical filter firstly removes the heavier fish waste preventing the biofilter from being overloaded and clogged.
The demand of the system is based on the amount of fish in the system and the waste they produce. This, in turn, determines the actual sizing of the biofilter
MBBR is the acronym for Moving Bed Biofilm Reactor.
What types of media to use in a MBBR?
The types of media used in a moving bed bioreactor (MBBR) are usually the ones that are small with a large surface area that can be churned around by the currents caused by the bubbles from the air pump.
K1 and K3 media are one of the main types used which features a lightweight with large surface area design.
The K1 media has a larger surface area than the K3 Media and is often used in DIY MBBR applications and aquaponics. K1 media is fluidized easily meaning that it can be churned around with little air bubbles.
For example, 10 liters of K2 media will have 25M2 of biological surface area.
The K3 media, however, has a larger surface area and is used in larger applications where the waste material is much larger such as in sewage treatment plants.
Why does an Aquaponic MBBR Need an Aeration?
Aeration is required in an aquaponic MBBR because of two main reasons.
- To add dissolved oxygen to the system
- Water agitation from currents created by the bubbles.
- Dissolved Oxygen –
The dissolved oxygen in an aquaponic system is not only required for the fishes and plants but also for the aerobic bacteria Nitrosomonas and Nitrobacter to carry out the nitrification process.
Nitrification is the oxidation of ammonia into nitrites and then to nitrates. The bacteria gets the oxygen required from the dissolved oxygen in the system and the air pump provides the required dissolved oxygen needed for them to do so.
- Water agitation –
Aeration is required for mixing the biofilm media. This helps dislodge any dead bacteria from building up within the media.
If dead bacteria is allowed to build up in the media it can cause the MBBR biofilter to emit a very foul stench. Additionally it keeps the anaerobic bacteria happy since it increases dissolved oxygen within the MBBR.
Benefits of having an Aquaponic MBBR?
An Aquaponic MBBR can handle large loads and convert large amounts of ammonia and nitrite into less harmful Nitrates for plants. It significantly increases the dissolved oxygen in the aquaponic system and removes carbon dioxide.
How to plumb an MBBR?
A Moving Bed Bio Reactor should be built such that it is a separate component attached to the aquaponic system. The piping should be arranged such that the incoming stream from the mechanical filter directs the flowing fluid downwards into the biofilter.
All piping should be connected using uniseals or bulkheads. I would recommend uniseals for aquaponic applications simply because it is easy to install, very flexible, and makes easy work when it comes to plumbing an aquaponic system.
The churning movement of the bio media would then break up any solids into smaller pieces for the nitrifying bacteria to do their job. The water is allowed to exit at the top of the biofilter after the filtration process is completed.
This water is now directed to the plant grow beds or Deep Water Culture system.
Do you have to cover the Biofilter?
The biofilter should be covered simply because the sunlight will cause moss and other microbiological plants to start colonizing the biofilter. This can lead to fouling and reduced efficiency of the biofilter which will be seen in elevated levels of ammonia in the system.
How do you know When the MBBR needs cleaning?
A simple inspection of the bio-media within the MBBR would tell if it needs cleaning. Usually, a brown mucky film can be seen building up within the sides of the media.
Another sign that the filter needs cleaning is when there are elevated amounts of ammonia in the system. This can only be seen only through testing.