Aquaponic Systems – Modern Farming in Urban Areas
An Aquaponic system is a form of modern farming that can be done even in urban areas. It basically recirculates and reuse water in an effective way and it consist of three main inputs and that is: water, feeds being given to aquatic animals and electric used to pump water between the aquaculture and hydroponics.
Aquaponic system relies in the relationship between plants and animals that will maintain a stable aquatic environment. This type of process provides a minimum fluctuation of ambient nutrient and oxygen levels. The basic component of this system is water. It is being added to replace the water loss due to absorption by plants and when it evaporates into the air or if it overflow due to rainfall and being removed by biomass such as solid waste produced in the system.
It uses at least 2% of the water that a conventionally irrigated farm consumes on the same vegetable production. The only difference is that aquaponic production can even be used in areas where water is scarce.
Another advantage for aquaponic systems is that it can imitate a controlled wetland condition that is useful for water treatment by reclaiming potable water from typical household sewage. The overflowing water can be dispersed to a catchment tank and be reused to maintain the growth of crops being grown in soil or the water can be pumped back into the aquaponic system that can replace the water being lost due to drought or dry season.
There are two categories within the aquaponic system: hydroponics that consist of plants such as vegetables and aquaculture that contains edible species among others fish. To keep the system stable, it is advised that they must be replaced from time to time.
There are two main parts in the aquaponic system and the first is the aquaculture part for aquatic animals and the hydroponics part that consist of growing plants. Aquatic waste coming from uneaten feed or raising animals like fish does accumulate in the water during the process due to the closed system recirculation of common aquaculture systems. Due to this, the effluent-rich water tends to toxic to fishes or other aquatic animals that has high concentrations but most of these effluents or water waste are nutrients that is essential for plant growth.
Aside from the two primary parts of the aquaponic system, it is also grouped into several components or subsystems to effectively remove solid wastes. That is adding bases to neutralize acids and to maintain oxygen in the water used in the system. These include the following:
- Rearing Tank – a cistern or container to raise and feed the fish;
- Solid Removal – a tool or component to entrap uneaten food and detached biofilms, and for settling our fine particles in the water;
- Biofilter – this is where the nitrification bacteria can grow and converts ammonia particles into nitrates that is being used by the plants;
- Hydroponics Subsystem – a part of the system that plants are being grown by absorbing excess nutrients in the water;
- Sump – this is the located in the lowest part of the system where the flowing water is being pumped back into the rearing tanks.
The cost of the aquaponic system may depend according to the on how the sophisticated the system is built such as the solids removal, hydroponics system and biofiltration units that are combined into a single unit or subsystem that prevents water from flowing directly to the aquaculture part of the system and even to the hydroponics part.
The nitrification process in an aquaponic system can be dependent on bacterial biofilm that is positioned in a specific biofiltering module or evenly distributed in the entire system. Proper handling for this bacterial colony is very important since it regulates the full assimilation of ammonia and nitrate for plant nutrient uptake and eradicates the presence of these metabolites that can be toxic to fish or aquatic species.
Basically, fish waste or effluents are the main source of nutrients for plants even if some minerals or nutrients such as iron are being added to the system. The most important function in the system is nitrification since it converts toxic ammonia into nitrates. Ammonia is released into the water through the excreta and gills of fish as part of their metabolism and if higher concentrations are present in the water then it can kill the fish and even plants cannot absorb it as well as nitrates. Nitrification makes it easier for plants to take up nitrogenous compounds safely and maintain a healthy population of bacteria called Nitrosomonas that can convert ammonia into nitrates. While another bacterium called Nitrobacter converts nitrites into nitrates that reduce the toxicity of the water and the remaining compounds can be removed by plants as part of their nourishment.
This method applies in the entire system since the bacteria responsible in this process forms a biofilm throughout the solid surfaces of the system that is in contact with the water and the roots of the plants or vegetable crops that is submerged in the water covers almost the entire surface area wherein most of the bacteria accumulates in this area. That is why most aquaponic systems include a biofiltering unit which helps aid the growth of microorganisms.
Normally, the level of ammonia should be in the range of .25 to 2.0 ppm while level of nitrite ranges from .25 to 1 ppm and the level of nitrate range from 2 to 150 ppm. In this system, nitrification process plays a role that acidifies the water, non-sodium bases like calcium hydroxide or potassium hydroxide could be added to neutralize the water’s pH level, if insufficient quantities are present in the water that will safeguard it against acidification.
Worms is another way to solve the buildup of solid matters in the aquaponic systems that helps liquefy the solid matter that can be utilized either by plants or marine animals.