What is biofiltration?
Biofiltration is any biological process used for the control or treatment of a wide range of organic and inorganic contaminants, in which microorganisms are responsible for the complete degradation of contaminants contained in air or wastewater streams.
Biofilters are the simplest and oldest bioreactors used for the removal and treatment of wastewater and unwanted gases.
Traditionally, this technology has had numerous applications at the industrial level, including the elimination of odors emitted by wastewater treatment plants or animal farms.
At ProCycla we design biofilters for biogas treatment with low energy consumption and low maintenance costs.
Biofilters for biogas
Biogas typically contains dust, sludge, small water droplets, carbon dioxide (CO2), ammonia, hydrogen sulfide (H2S) and traces of other gaseous compounds. The specific use to which the biogas will be put determines the level of purification required, so pre-use treatments are needed to remove impurities. One of the technologies used to purify it is biofiltration.
Biogas biofiltration consists of previously selected species of bacteria that are inoculated into the biofilter and degrade or transform compounds such as hydrogen sulfide into sulfur.
The equipment used for biological gas purification can be divided into three types.
Fixed bed biofilter
It consists of a biological filter filled with an organic support (peat, compost or soil) whose function is to fix the biomass and serve as a source of nutrients. The gas is fed through the bed and the pollutants are absorbed in the liquid film that is formed, being degraded by the biomass.
They are suitable for treating contaminants with low water solubility.
Unlike biofilters, in scrubbers the pollutant is first absorbed in water, namely in a liquid-filled absorption tower. The operation consists of flowing the gas countercurrent through the water.
Subsequently, in the second phase, the liquid stream is treated in a reactor packed in a material covered with the microorganisms responsible for the degradation.
These systems are suitable when the contaminant is very soluble in water.
Biofilter trickling filters
It consists of a single column filled with a synthetic support (usually ceramic or plastic material) in which a biofilm (a layer of microbes that adhere to a surface) develops. A gas stream containing the pollutant to be removed is fed through the bed, and a liquid stream circulates through the upper part, which has the function of providing nutrients to the microbes, maintaining humidity and pH conditions, as well as eliminating the products degraded by the microorganisms.
The adsorption and biodegradation operation of the pollutant in the trickling filter biofilters is carried out in the same equipment, which makes them a versatile and less expensive solution.