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Charis at Work.....Anaerobic Digestion

Anaerobic digestion is a series of processes in which micro-organisms break down biodegradable material in the absence of oxygen. One major application is in the treatment of waste water but it is increasingly finding use in other fields where the breakdown of almost any organic material can be processed with anaerobic digestion. This includes biodegradable waste such as paper, grass clippings, leftover food, sewage and animal waste. The biogas produced by the process can be harnessed to power generating and heating plants, while the liquid and solid residue can be used to replace chemical fertilisers. The major benefits of anaerobic digestion includes the reduction of material sent to landfill sites, and the reduction of ozone-layer damaging methane escaping to the atmosphere.

The digestion process creates foam which needs to be controlled. By using a Charis Foam Control System a considerable saving in antifoam costs can be made as the system continuosly monitors the level of foam within the digester and adds antifoam only when required. Additionally if the level of foam is kept to a minumum a greater level of through-put is possible. Our work in this field with companies such as Southern Water, Thames Water and Anglian Water has proved that we are able to reliably meet both of these criteria.


This diagram shows a typical Charis Foam Control System for a bio-digester.

A 20mm foam sensor is inserted through the digester roof through an isolating valve. The adjustable fitting allows the sensor to be moved to the correct depth to suit the process. By using the isolating ball valve it also allows for the removal of the sensor for maintenance.


As anaerobic digesters are classed as hazardous areas the sensor is connected to the foam and liquid controller via a Zener barrier. The controller is in turn connected to the client's own process controller or an antifoam pump.
Anaerobic digestion is a very dirty process causing much fouling of the foam probe. In some systems this would cause the system to stop working but thanks the Charis's unique IMA®Sensing technology the Charis system will continue to work even under the severest fouling conditions.
Charis Technology products are designed to provide a cost effective solution to foam control in an environmentally friendly manner. Charis Technology is a member of ADBA, the trade association for the Anaerobic Digestion and Biogas industries.

If you feel that Charis Technology could help you control your foam problems in a cost effective and reliable manner please contact us.


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