Stratification structure of sludge flocs with implications to dewaterability.
Sludge dewatering has proven to be an effective method to reduce the volume of sludge. In this study, a novel stratification approach aimed at better understanding the factors influencing the sludge dewaterability (as determined by capillary suction time, CST) was developed. The sludge flocs from 14 different full-scale wastewater treatment plants (WWTPs), including sewage, leachate, industry, and special-source sludge, were stratified through centrifugation and ultrasound into five layers: (1) supernatant, (2) slime, (3) loosely bound extracellular polymeric substances (LB-EPS), (4) tightly bound EPS (TB-EPS), and (5) pellet. The results showed that the distribution pattern of proteins (PN) in the sludge flocs differed from that of polysaccharides (PS). The normalized CST correlated with PN (R2 > 0.72, p < 0.01) and PN/PS (R2 > 0.51, p < 0.01) in the supernatant, slime, and LB-EPS, but not with PN and PN/ PS in the pellet and the sludge flocs as a whole or with PS in any of the fractions and or the sludge flocs as a whole. The results suggest that PN and PN/PS in the supernatant and slime layers, which are usually decanted due to their assumed lower content of organic matter, markedly impact sludge dewaterability.
Yu
Guang-Hui
GH
State Key Laboratory of Pollution Control and Resources Reuse, Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
He
Pin-Jing
PJ
Shao
Li-Ming
LM
He
Pei-Pei
PP
D005427:Flocculation; D011134:Polysaccharides / Q000032:analysis; D011506:Proteins / Q000032:analysis; D012722:Sewage; D013997:Time Factors; D014867:Water / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
D011134:Polysaccharides; D011506:Proteins; D012722:Sewage; D014867:Water