Study On Enhancing Sludge Dewaterability Using Lysozyme Combining With Flocculant

Focused on the sludge dewaterability, this study investigated the effect on sludge dewaterability by combining flocculant with lysozyme. ascertained the type of flocculant that combined with lysozyme and the best way and best running progress conditions of combination. This paper also investigated the mechanism of sludge dewatering by measuring sludge zeta (ζ) potential, analyzing the flocculation morphology of sludge and the quantitative of extracellular polymeric substances (EPS)The result showed that, organic coagulant-BASF was the best type of flocculant combined with lysozyme for it could overcome the weakness of sludge sedimentation performance when sludge was disposed by lysozyme, and efficiently improve its. This study determined Preliminarily that the optimal dosage of lysozyme and flocculant was0.05g/g and20mL/L respectively, and best combination way was flocculant+lysozyme, according to orthogonal experiments. In this disposing way, the sludge SV30decreased by38.2%, setting velocity in earlier stage increased11.5times, and dewatering velocity and level increased by73%and15.8%respectively compared to the control sample. It couldn’t further increase the sludge dewatering velocity, but could slightly increase its dewatering level on the original foundation when fixed the flocculant dosage as the optimal and increased the lysozyme dosage, however, the sedimentation performance of sludge became worse slightly, with the lysozyme dosage increased. Besides, it couldn’t further increase the sludge dewatering velocity, but could further increase its sedimentation performance and dewatering level when increased the flocculant dosage and fixed the lysozyme dosage as the optimal, when the dosage of flocculant was40mL/L, the sludge SV30decreased by40.2%, setting velocity in earlier stage increased by19.5times, and dewatering level increased by18.1%compared to the control sample. Furthermore, this paper also ascertained that the best disposing concentration range were20000-25000mg/L, the best temperature was20℃and the best pH was6.This study investigated the effect of sludge ζ potential, flocculation morphology and EPS on sludge dewateability. The result showed that,ζ potential wasn’t the only factor affects sludge flocculating. The most significant influencing factors of sludge sedimentation performance and dewatering velocity was the flocculation morphology of sludge. Because, before disposed, the sludge floes were tiny and loose, the size of holes on the sludge surface were big, and the average value of sludge two-dimensional fractal dimensions (D2) flocs was1.33, so that the sludge sedimentation performance was bad and dewatering velocity was slow; when sludge was disposed by lysozyme alone, the sludge flocs became tinier, which made the sludge sedimentation performance worse, however, the floe appearance and surface shapes were tight, and the value of D2increased to1.43, so that the sludge dewatering velocity became quick; when sludge was disposed by flocculant alone, the sludge floes became large, the floe appearance shapes were relatively tight, and the value of D2increased to1.61, so that the sludge sedimentation performance became better and dewatering velocity became quick, however, there were small holes between the floes, and the size of holes on the sludge surface were big; when combined flocculant with lysozyme, the sludge flocs became large, especially, when dose flocculant before lysozyme, the floe appearance and surface shapes were tight, and the value of D2increased to1.69, so the sludge sedimentation performance became better and dewatering velocity became quick. Disposed by Flocculant and lysozyme individually or together all have effect on total contents of EPS, and on polysaccharides (PS) and proteins (PN) contents both in loosely bound (LB) and tightly bound (TB), based on total contents of EPS, the ratio of LB/TB had the most important effect on sludge dewatering level for the Pearson correlations between LB/TB and dewatering level reached to0.91, the lower ratio of LB/TB, the better of the sludge dewatering level.