Combined biological and physico-chemical treatment of baker's yeast wastewater including removal of coloured and recalcitrant to biodegradation pollutants

The UASB reactor (35degreesC) was quite efficient for removal of bulk COD (62-67%) even for such high strength and recalcitrant wastewater as the cultivation medium from the first separation process of baker's yeasts (the average organic loading rates varied from 3.7 to 10.3 g COD/I/d). The aerobic-anoxic biofilter (20degreesC) can be used for removal of remaining BOD and ammonia from strong nitrogenous anaerobic effluents; however, it suffered from COD-deficiency to fulfil denitrification requirements. To balance the COD/N ratio, some bypass of raw wastewater should be added to the biofilter feed. The application of iron chloride coagulation for post-treatment of aerobic effluents may fulfil the discharge limits (even for colour mainly exerted by hardly biodegradable melanoidins) under iron concentrations around 200 mg/l.