A Scaling-up Issue: The Optimal Bioreactor Configuration for Effective Fungal Treatment of Textile Wastewaters

Real textile wastewaters were treated by a combined method with fungi and activated sludge. In this work, the white rot fungus Trametes pubescens MUT 2400 which has already showed to decolorize wastewaters, was exploited for biodegradation purposes with the aim to scale-up the system to larger working volumes. A bubble column reactor, a fixed bed reactor and a stirrer tank reactor were investigated. Colour, COD and toxicity were monitored before and after both the treatments. It was thus possible to identify the main targets towards which the two biological methods are mainly effective: colour for fungi whereas COD and toxicity for the activated sludge. Both the growth and the degradation yiedl of the fungus were highly affected by the different aeration and agitation conditions, with strong repercussion on the final process yields. Actually, DP values were very low when the bubble column reactor was used. On the contrary, the stirrer tank reactor resulted the best reactoristic configuration: the extensive decolourisation (85 %) and the COD reduction (95 %) were coupled with a significant detoxification monitored by L. sativum test. Consequentially, thanks to the combined biological treatment, the textile effluent parameters complied the Italian legal threshold limit for the discharge in surface waters.