Page 63 - fish_farms_curriculum

Fig. 5. Sedimentation basin cross section and working principle

6.3. Biological Filter

The most important element of the biological filter is the biological elements. Biological

elements are surface enhancing plastic pieces of different shapes and sizes with different
materials. These are important biological filter elements that are necessary during the

nitrification process, in which ammonia in water is converted into nitrate, and that bacteria,

which is an important creature of the geothermal system, adhere to these surfaces and that the
nitrification process takes place with the oxygen provided by aeration. Biological elements are

commercially sold under different names (bioball, bioelement, kaldnes). The most important
feature to be considered while supplying biological elements is that they must not be

produced from recycled plastics. Since the plastics used in recycling are produced from
materials that are with unknown origins and for what purpose they were used in the past, they

have a high probability of deteriorating the water quality. In addition, recycling plastics have

very low resistance to UV from sunlight. Biological elements made of plastic material with
known manufacturer and high UV resistance will be both safe and long-lasting. Another

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important property of biological elements is the amount of surface area in m . Although there
are biological elements with a surface area of 350-500 m²/m³ in the market, it is possible to

find biological elements with a surface area of 750 m²/m².

There are biological elements produced in different densities according to the density of
water. Salt water and fresh water productions have different densities. Biological elements

float in water (0.9-1.0 g/cm') when they are first released into the water, and their density

increases with the adhesion of bacteria on them over time and sinks to the bottom. In the
biological filter stage, these biological elements should be aerated and dispersed

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