Bioscrubber

Application

Odour removal
Removal of volatiles:
- alcohols (methanol, ethanol, ...)
- aromatics (toluene, styrene, ...)
- others (aldehydes, esters, amines, sulphur and chlorinated compounds, …)

Principle

A bioscrubber consists of an absorption column (scrubber) and a bioreactor. In the scrubber, the volatiles are absorbed inthe scrubbing liquid while the dissolved compounds are subsequently biodegraded in the bioreactor. The scrubber liquid returning to the absorption column can be biological sludge or effluent from the bioreactor after sludge sedimentation. Depending on the situation, the absorption column can be an empty spray column or a packed bed column.

This biotechnique can be useful when a biological waste water treatment plant is available on-site. However, in order to prevent the need for too high circulating scrubber liquid flows, this technique is mainly used for the removal of volatiles with a rather low Henry-constant (e.g. alcohols) or for small gas flows with high pollutant concentrations (e.g. H₂S removal from biogas). When using a packed bed absorption column, attention should be paid in preventing biofouling and accumulation of biosludge on the packing material.

A more elegant biotechnique is the bioscrubber in suspension (BIS), where a liquid driven jet ejector is used to aspire the waste gases and to disperse the biosludge/gas mixture at the bottom of the bioreactor. Due to the intense mixing of the gases with the biosludge, optimal removal efficiencies can be obtained in this type of bioscrubber for compounds with a significantly higher Henry-constant as e.g. aromatics, and this provided the biosludge is adapted to the volatile compounds to be removed. Depending on the required removal efficiencies, a polishing biofilter or carbon filter can be installed downstream the bioscrubber technique.