The Influences of Sodium Hexametaphosphate (SHMP) and Methyl Orange (MO) on Enzyme Hydrolysis of Excess Sludge

Abstract

The effect of Sodium Hexametaphosphate (SHMP) and Methyl Orange (MO) on the hydrolysis of sludge were investigated under the optimum condition of alkaline protease hydrolysis. The results showed that as the concentration of SHMP was increased, the content of Soluble Chemical Oxygen Demand (SCOD), protein, and polysaccharide in the sludge hydrolysate gradually raised. When the concentration of SHMP was 0.1g/g·tss, the contents of SCOD, protein, and polysaccharide increased by 17.16%, 50%, and 9.72% respectively. With the increase of MO concentration, SCOD decreased gradually. When the concentration of SHMP was 0.02g/g·tss, the SCOD decreased by 10.3%. An increase of 13% in the protein content was noted, when the concentration was 0.02g/g·tss. On the contrary, there was a slight reduction of the polysaccharide content i.e. 2.4%. The concentration of the polysaccharide was found to be the lowest at the concentration of 0.002g/g·tss. From the aforementioned results combined with three-dimensional fluorescence map of sludge EPS, it was found that SHMP promoted the hydrolysis of sludge by alkaline protease and accelerated the dissolution of intracellular organic matter. Herein, the MO inhibited alkaline protease hydrolysis of sludge, which hindered the dissolution of intracellular organics.