Alizair™ is particularly well suited to the treatment of gaseous effluents that are generally encountered in sewage/sludge treatment works. Alizair™ is designed to handle very high flow rates.

 

Alizair™ eliminates almost all malodorous compounds. Efficiency in the treatment of mercaptans may be improved by the addition of a gas filter upstream or downstream from the bioscrubber.

The filter media

Due to its experience in deodorisation using peat beds, Veolia Water Solutions & Technologies has been able to further develop the use of mineral material to greatly enhance process performance. Alizair™ can thus achieve very high filtration rates (500 m3/h) with treatment loads that may exceed 50 g/h/m3 of material.

A biological odour treatment uses microorganisms to oxidize the organic and inorganic malodorous substances to inorganic non odorous compounds. Depending on the existing substances in the odorous gas to be removed, the biodeodorization takes place using different kinds of bacteria, and so, different biofilter conditions.

The best performances for the oxidation of H2S, total sulphide, ammonia and RNH2 are obtained using an autotrophic biofilter. The filter media used in this case is Biodagene™, a mineral non-degradable material with high porosity.

If the composition of the air to be treated requires an heterotrophic biofilter treatment (because of the presence of VOC for example), another type of media can be used, like peat and vegetable filters, for example. The specific composition of the malodorous gas and the features of the plant determine the choice of support material to be used in every case.

Nutrient solution sprinkled on the filter media

As for the filter media choice, the composition of the nutrient solution sprinkled on the filter media depends on the type of bacteria and odours to be removed. For an autotrophic biofilter, with Biodagene™ as media, the necessary nutrients to be provided to the biomass are:

  • a source of mineral carbon (CO2 in the air)
  • a source of nitrogen and phosphor (generally present in the raw water in the wastewater treatment plant inlet).

Usually, the sprinkling of raw water on the filter media (and its recirculation) is enough to keep the necessary nutrient levels and humidity. No external chemical addition is then required.

The nutrient solution dosing is controlled using a PLC, according to the inlet air flowrate, the humidity of the air and the media. The dosing is usually not continuous and follows a sequence of sprinkling.