Semi-continuous anaerobic digestion of a food industry wastewater in an anaerobic ®lter

The experimental results of semi-continuous tests of anaerobic digestion of confectionery industry wastewater, carried out at di€erent residence times and organic loads in an up¯ow anaerobic ®lter, are presented and discussed. Giving COD removals higher than 80% under the whole range of conditions tested, the anaerobic ®lter demonstrated not only a great ability of biomass to adapt itself to a new carbon source but also an excellent capability to deal with organic load ¯uctuations and to utilise dilute feeds. Sampling at di€erent ®lter heights demonstrated that the biogas development ensured mixing within the ®lter and that most of the organic substances were utilised at the bottom of the reactor, especially when very dilute wastewater was fed. The results of this work could be taken as a starting basis for scaling-up the process to the industrial scale