Design criteria for the biological treatment
There are several factors to take into account when designing a biological treatment system.
Calculate the MBBR media surface
Amount of media to purchase:
Each bacterial support has a defined surface, expressed in m²/m³ (ft²/ft³). This represents the surface area available for biofilm colonization, the size of the building so to speak.
The larger the area, the smaller is the media investment. In fact, for the same pollutant load, less media is required.
Let’s take an example: for a project of 52,000 m²:
- With the 1h2o3 Activated Carbon Chips: 20 m³ is required.
- With 800 m² Chips: it’s 65 m³.
So, with a standard support, you buy 3.25 times more media than the 1h2o3 MBBR media. It’s a significant saving!
What materials and biological agents to choose for salt water filtration
If you work with sea water, it is essential to choose equipment that is resistant to the corrosive power of chloride ions. Otherwise you may lose your installation very quickly. Opt for materials like PVC or polyethylene that resist corrosion.
Regarding the media and biological agents, they must also have this resistance to corrosive products.
Water temperature
Water temperature will have a strong influence on bacterial efficiency. Indeed, bacteria thrive in warmth, with their activity increasing with temperature up to a certain limit. On the contrary, in colder waters, their efficiency decreases. The temperature is therefore a parameter to be taken into account when designing your installation.
Pollutant to be treated
Nitrogen
The nitrogen comes from various sources, such as fish excrement in aquaculture or industrial and agricultural pollutants. It has the unfortunate tendency to cause anoxia in the environments in which it is found in excess. So, it is vital to treat nitrogen before discharging water into the environment to protect our ecosystems.
Nitrogen is processed by bacteria that transform it into nitrite and then into nitrate. Under conditions without oxygen, other similar bacteria convert these nitrates into dinitrogen. Dinitrogen is a harmless gas for humans and constitutes 80% of the air we breathe.
Carbon
Carbon comes from various sources, such as the decomposition of organic matter or municipal, agricultural, and industrial discharges. Carbon removal is also essential. High concentrations can have harmful consequences in the water.
Dissolved carbon will reduce the availability of dissolved oxygen to aquatic organisms. Its biological breakdown requires oxygen, promoting bacterial growth. These bacteria consume oxygen, posing a risk of inducing anoxia, and can be detrimental to health.
Hence, the importance of using an MBBR system, regularly aerated, to prevent these issues.
