Bio-trickling filter for H2S removal


The bio-trickling reactor holds large amount of packing materials. The surface-treated packing material offers surface area for bacterial growth. Nutrient solution is recycled over the package continuously to maintain the ideal condition for bacterial growth. In most cases, the nutrient supply can be from natural source or man-made fertilizer, such as:

  • Digested waste water

  • Liquid phase of digested sludge or manure

  • Landfill leachate

  • Artificial fertilizer NPK

When the biogas is feed into the reactor from the bottom, controlled quantity of air is mixed into the biogas. The oxygen concentration is maintained high enough for reaction while much lower than the flammable range.  

Special aerobic bacteria (i.e. Thiothrix or Thiobacillus), start growing in the nutrient solution and on the surface of packing material. The bacterial take up the H2S and O2 from the gas and convert it into elemental sulfur and sulfuric acid. Small amount of nutrient solution is wasted everyday to maintain the pH, nutrients and level. 

The raw biogas (3) enters the reactor (1) at the bottom and passes through the package from bottom to top. Air (4) is added at the gas inlet point. The air flow is controlled via the residual oxygen concentration or via the biogas flow meter signal (10). In case of no flow or extremely low gas flow, the air supply is switched off by the security flow switch (16). The water and nutrient solution (7) are stored at the bottom of the reactor and recycled through the package continuously by pump (8). The level of the nutrient solution is controlled by the level switches (13). For best activity of the bacteria, the temperature is controlled by the heat exchanger (9) and the temperature sensor (12). The quality of the nutrient solution is controlled by the pH transmitter (11). Waste nutrient solution (15) is automatically discharged while fresh water is injected to system by adding nutrient supply (5) and dilution water (6).


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Palmerston North, 4410
New Zealand

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