Evaluation of distillery wastewater treatability in a customized photobioreactor using blue-green microalgae – Laboratory and outdoor study

Abstract

Treatability of anaerobically digested distillery wastewater is challenging because of its high pollution load of COD up to 40,000 ppm. This research investigates the possibilities of retrofitting the effluent treatment plant (ETP) of a distillery with microalgae treatment step. For this, at first the photobioreactors of capacity 50 L and 500 L were customized for the cultivation of Spirulina sp. under xenon lamp and sunlight. The reactor supported the maximum specific growth rate up to 0.42 ± 0.03 d−1 in the 50 L reactor at laboratory and 0.10 ± 0.02 d−1 in the 500 L reactor at the outdoor for Spirulina sp. The treatability of wastewater of COD 30,000 ppm–40,000 ppm was carried out in those reactors with the Spirulina sp. of culture volume fraction 0.8 and 0.93 under xenon lamp and sunlight respectively. The chemical oxygen demand and total dissolved solids reduction were 60–70% in both the volume fractions of the culture. Ion chromatography analysis indicated the reduction of major inorganic pollutants in the wastewater by the Spirulina sp. The algae were sustainable when the culture volume fraction was increased from 0.8 to 0.93. Thus, the phycoremediation was shown the significant pollution reduction in the wastewater. The addition of this step is valuable and it benefits the distillery by not only improving the quality of wastewater but also through the generation of algae biomass that would be appropriate for animal feed or biofuel application. However, the detail biochemical study is needed for the best use of algae biomass and the treatment could be checked for the long run sustainability.