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Solid Filtration: Media beds, trickle filters, foam filters, swirl filters, radial flow filters, drum filter, bead filters, sand filters, and settling tanks are all great solid removers. Some of these filters have advantages over the others such as; ease of cleaning, cost of operation, and start up. Removing all solids is key to a clean system, but is not always necessary in small systems, as the media beds can remove most solids and break them down into usable nutrients. If the media beds become anaerobic or clogged with solids there can be a build up of toxic levels of nitrites and ammonia which will affect water quality quickly.
Advantages and disadvantages of different types of solid filtration
Media beds - The media bed form of aquaponics uses containers filled with media 6 to 12 inches deep such as gravel or expanded clay (hydroton) to support the roots of plants. The media bed can be a constant water level or flooded and drained with a bell siphon or a timer on the water pump. The media bed also adds surface area to increase the biological surface area of the system.
Trickle filters - is any random or structured packed media that has water “trickling” over the top of the media. It can be made out of just about anything that will hold the media out of water while the fish water is ran through. This style filter removes fine solids and also adds to the biological surface area.
Only drawback is that a trickle filter needs to be cleaned frequently as it gets clogged with debris.
Foam filters - Generally, sponge filters are good for most aquaponic systems..... Sponge filters are
excellent due to their gentle flow. This allows for set-ups for fish fry and shrimp tanks that thrive in
low-flow filtration and also prevents the fry and shrimp larva from being sucked up into the water pump or filter. This style filter removes fine solids and also adds to the biological surface area.
Swirl filters - A swirl filter also called an aquaponics settling tank, it is often used in an aquaponics system to remove the heavier solids from the water. The swirl filter allows solids heavier than water to settle to the bottom of the tank to be removed from the system and since the output water from this filter is drawn from below the surface of the water floating debris can also be separated from the system. This filter is easy to build and maintain and has a low cost startup and works fantastic.
Radial flow filters - Very similar to the swirl filter, but instead of swirling the water around, this style uses a reverse water flow to separate the solids out of the aquaponic system. This filter allows solids heavier than water to settle to the bottom of the tank to be removed from the system and since the output water from this filter is drawn from below the surface the floating debris can be separated from the system. This filter is easy to build and maintain and has a low cost to start.
Drum filter - This is an awesome filter but the start up cost is very high. A drum filter is a rotating self cleaning screen that is almost completely automated. This style filter is used in large scale aquaculture and removes fine solids very well and it makes a great addition to any aquaponic system. Some drum filters use UV lights to help clarify the water.(UV light kills the bacteria in the water column)
Bead filters - is a filter that uses a packed area of beads as the water flows through the beads the solids are removed. These style filters can be completely automated with a backwash system and adds huge surface areas for the biological filtration. These filters are normally for high fish loads and have a higher start up cost but the ease of use can make these a great asset to any aquaponic system.
Sand Filters - is a filter that uses a packed area of sand. As the water flows through the sand, solids are removes. These style filters are not the greatest for one main reason they clog up quickly and need constant backwash to prevent channeling which bypasses the sand and reduces the filtration capability and can cause extreme loads on your water pump. Sand filters can be completely automated with a backwash system and adds huge surface areas for the biological filtration. I would not recommend using this style filter as they use a lot of water during the backwash and can cause pump damage if not maintained correctly, but if it is what you have they will work for smaller fish loads.
Settling tanks - This is one of the easiest filters to set up. Basically it is a tank that has little to no water movement which allows the solids to settle to the bottom to be removed from the system. Normally a cone shaped bottom is used so that the removal of the solids can be done with a turn of a valve. These solids make a wonderful fertilizer for any other plants you might have. You can also use flat bottom tanks but they are normally cleaned by vacuuming the solids out using a water siphon and if you have ever siphoned gas you know what can happen. A mouth full of nasty.
UV Sterilizing Light - This is not a solids remover but does allow you to control the levels of bacteria in your system. A UV light will kill bacteria, fungi, and viruses in the water column keeping your water clean and clear. This filter normally works very well with a foam fractionator as this style filter removes the dead organic matter from the system
Foam fractionator - This filter works best with saltwater biofloc aquaculture. Biofloc is a style of aquaculture that uses bacteria along with a carbon additive to consume the ammonia creating a biofloc. A biofloc is created by many live creatures which then are consumed by the filter feeders(certain fish and shrimp) but can be used after a UV light to remove very small dissolved organic debris from your system. Foam fractionation is an efficient, cost-effective way to remove small particles and dissolved organic wastes from water while at the same time increasing dissolved oxygen levels. The Foam fractionator mixes air and water together causing an attraction to the organic solids which is then removed from the system by the foam.
Next blog entry will cover biofiltration methods.
Joe Leveridge
TXUS Farms
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