The Buoyant Filter Bioreactor (BFBR) has designed for treatment of high strength complex wastewater. BFBR converts wastewater containing a high ratio of suspended COD to total COD. Suspended organic materials that contribute to anaerobically degradable COD include starches and complex carbohydrates, proteins, fats and oils. Conventional high-rate anaerobic reactors are not efficient at retaining suspended COD. Unlike in conventional high-rate UASB, the BFBR has a high efficiency retention mechanism with forced cleaning system to retain both suspended solids and biomass, and thus achieve high efficiency for wastewaters with suspended COD. The high velocity backflow is created by periodic release of gas accumulated in the reactor (US Pat. 6592751), thereby avoiding extra pumping systems and power consumption. BFBR system has been customised and installed in different rice mill and ice-cream factories as per the effluent capacity