START-UP OF ANAEROBIC FIXED-FILM REACTORS - TECHNICAL ASPECTS

For two years lab-scale experiments were done to find the conditions t o enhance the start-up of anaerobic fixed film reactors. Five reactors were operated in parallel with a sythetic wastewater containing aceti c, propionic and butyric acid in a weight relation of 2:1:1 resulting in a COD of 20,000 mg/l. Using polypropylene curlers (NOR-PAC R 92/1) as support medium (substratum) and mostly digested sludge of a municip al wastewater treatment plant as inoculum, we found that the activity of the starter culture, effluent recirculation, calcium dosage and the mode of increasing the organic loading rate had a significant influen ce on start-up behaviour. Depending on the way to run the start-up spa ce loading rates of 10 to 30 g COD/(l.d) could be reached within 58 da ys. In contrast to these ''manual'' start-ups it is shown that the mos t efficient way is to run a start-up pH-statically with an automatic s ubstrate feeding regulated by the pH measured in the top of the reacto r. Within 36 days a space loading rate of 60 g COD/(l.d) with a COD re moval efficiency of 70 % could be reached.