Anaerobic treatment of wastewater with high salt content from a pickled-plum manufacturing process

Abstract Anaerobic treatment of wastewater with a high salt content generated during a pickled-plum manufacturing process (TOC, 14g/l; ash, 150g/l; pH 2.7, hereafter called pickled-plum effluent) was investigated for its effect on the high salt content of the wastewater. The synthetic wastewater, including NaCl up to 30g/l, was treated anaerobically by a draw and fill method (treatment temperature, 37°C; volumetric loading rate of organic matter, 2g/l·d). The TOC removal efficiency and rate of gas evolution then gradually decreased as salt content increased, although stable operation was maintained. At NaCl concentrations above 30g/l, TOC removal efficiency decreased rapidly and stable operation could not be maintained. Five-fold-diluted pickled-plum effluent was treated by the same method at a volumetric TOC loading rate of 2.9g/l·d with a TOC removal efficiency of 71%. Five-fold-diluted pickled-plum effluent was also treated in an anaerobic fluidized-bed reactor (AFBR) at a maximum volumetric TOC loading rate of 3.0g/l·d, which gave almost the same results as the draw and fill method. However, ten-fold-diluted pickled-plum effluent could be treated in the AFBR at a maximum volumetric TOC loading rate of 11.1g/l·d with a TOC removal efficiency of 84.6%. The red pigment in the pickled-plum effluent was completely decolorized by the anaerobic treatment.