Biological Filter

AmerAir International is a leader in supplying complete air pollution control systems in the Middle East providing proven chemical scrubbing, venture scrubbing, biological filtration and carbon adsorption technologies to our customers.

We represent major top suppliers for the pumps, fans and other peripheral equipments utilized in our system designs.

In a typical bio trickling odor control system, the odorous air from various sources such as  a sewage wet well or screen area, is ventilated to the odor control unit by a fan. The extracted air is then  passed through a biologically active packing media  to remove the odorous pollutants.

Clean air is  discharged through a stack installed on top of the bio filter. A typical removal efficency of Hydrogen Sulfide in this system is  about 99.5%.

Higher removal efficiencies are achievable if needed.

The bio filter is of a counter current design, where the gas enters the tower via the gas inlet at the bottom of the vessel. The gas moves upward and passes through the packing bed while being irrigated from above with water through the spray nozzle situated immediately above the bed. Similarly to all absorption processes the odorous gases are first dissolved into the liquid phase and then oxidized by the biomass. The microorganisms living on the packing surfaces consume the absorbed gases as food and yield by-products that are free of odor.

The filter is supplied with a water control cabinet which controls and monitors the water addition to the tower. The amount of washing liquid is controlled by a motorized valve which automatically opens and closes to adjust the irrigation rate of water over the packing media. The amount of water usage is recorded by a flow control sensor and a totalizer via a PLC unit installed in the same control cabinet.

The packing media is designed to provide the highest concentration of biomass for maximum removal efficiency of the various contaminants, i.e. Hydrogen Sulfide and Mercaptans. The media is a multilayer structured woven synthetic material that is rolled into a bundle that fits tightly in the filter. Several bundles of media are provided. Since the irrigation of fresh water takes place at the top of the tower, a pH profile is formed from the lowest point (bottom of the tower) to the highest point (top of the tower).

This allows for culturing various types of bacteria in each section. At the lowest section where acidic conditions prevail mainly autotrophic bacteria are formed which effectively remove Hydrogen Sulfide. At the top section where the pH condition is more neutral mainly heterotrophic bacteria flourish which effectively remove Mercaptan and VOC compounds.

The overall tower performance yields a minimum of 99.5% removal of Hydrogen Sulfides and about 85% of other odor causing compounds.

The main by-product of oxidation of Hydrogen sulfide is sulfuric acid while carbon dioxide and water as well as Sulfuric Acid are generated by bio oxidation of Mercaptans (i.e. Methyl Mercaptan) as shown in the reactions below:

H2S + 2 O2 + Autotrophic Bacteria → H2SO4

2 CH3SH + 7 O2 + Heterotrophic Bacteria → 2 CO2 + 2 H2SO4 + 2 H2O

This design allows for an effective removal of a range of odor causing agents in one tower enhancing overall odor efficiency at the lowest operating cost. The bacteria uses the odorous compounds in the aqueous phase as food along with other nutrients (i.e. nitrogen and phosphorous) present in the water. If potable water is used, additional nutrient shall be added automatically by a metering pump to the water being supplied. In most cases, the only consumable is water and where the utility water specification meets the criteria this cost is also minimized by the usage of utility water.

The media has an open structure, AmerAir OpeNet, which yields a low pressure drop across the media while achieving a high level of biomass elimination capacity for Hydrogen Sulfide. The OpeNet packing media structured nature reduces the possibility of any water or air channeling and therefore yielding a higher odor removal rate.

The packing material of construction is fully resistant to the reaction products and bacteria and is warranted for 10 years with an expected life of 20 years. The media also provides for an efficient sustenance of biomass to assure that sufficient biomass is retained in the media at all times.