Biodegradation and decolourization of biomethanated distillery spent wash

Abstract

A bioremediation method was optimized to degrade and discolour the biomethanated distillery effluent. This phytoremediaion involved a dual stage microbial treatment. During primary treatment, fungal consortium was employed using fluidized film aerobic system (FFAS) and during secondary treatment, algal biomass either in free state (powder form) or in immobilized condition (alginate beads) was employed. The analyzed effluent at the end of FFAS treatment showed a reduction of ~70% in BOD and ~63% in COD without causing any color change. However, at the end of the secondary treatment with algal biomass resulted in a reduction of ~80% in COD and effected 75% decolourization. The optimized conditions for discolouration in the packed bed column were 1.5mm size of immobilized beads, 3.5cm height of packing, 300ml/l spent wash flow rate, 20 H/D ratio of column for immobilized algae and 4cm packing height, 400ml/l spent wash flow rate and 20 H/D ratio of column for algae without immobilization. The efficiency of discolourization by algal biomass remained unaffected by immobilization. An approach of this study could be used to develop a cost effective, ecofriendly biotechnology tool for the bioremediation of spent wash.