Performance of the lysozyme for promoting the waste activated sludge biodegradability

•Lysozyme has a strong ability to disintegrate WAS for biodegradability promotion.•Soluble protein dominated in SMP contributed to improve sludge biodegradability.•It is feasible to reclaim the carbon source from sludge by lysozyme digestion.

The fresh waste activated sludge (WAS) from a lab-scale sequencing batch reactor was used to determine the performance of the lysozyme for promoting its biodegradability. The results showed that a strict linear relationship presented between the degree of disintegration (DDM) of WAS and the lysozyme incubation time from 0 to 240 min (R2 was 0.992, 0.995 and 0.999 in accordance with the corresponding lysozyme/TS, respectively). Ratio of net SCOD increase augmented significantly by lysozyme digestion for evaluating the sludge biodegradability changes. Moreover, the protein dominated both in the EPS and SMP. In addition, the logarithm of SMP contents in supernatant presented an increasing trend similar with the ascending logarithmic relation with the lysozyme incubation time from 0 to 240 min (R2 was 0.960, 0.959 and 0.947, respectively). The SMP, especially the soluble protein, had an important contribution to the improvement of WAS biodegradability.