A novel treatment for amelioration of sludge dewaterability using green starch-grafted flocculant and realized mechanism

To clarify the effect of extracellular polymeric substances (EPS), protein and hydrophilic substances on the dewatering efficiency during starch-grafted flocculant (SBF) conditioning, a green and cost-saving SBF was synthesized. Dewatering performance of sludge, secondary structure of protein, change of hydrophobic sub-stances and removal of bound water were investigated. Results showed that after SBF conditioning, filter cake moisture content and specific resistance to filtration decreased from 75.63 % and 2.31 x 1012 m/kg to 66.76 % and 5.68 x 1011 m/kg, respectively. SBF neutralized the negative charges from the sludge system, promoting the increase of sludge flocs size and EPS decomposition, decreasing the compressibility of sludge and constructing a channel for water release. Moreover, the secondary structures of protein were changed through the interaction between SBF and the oxygen-containing functional groups in EPS, resulting in the reduction of hydrophilic substances and the increase of hydrophobic substances, which increased the hydrophobicity of molecules and thus improved the dewatering capacity of sludge. Meanwhile, the construction of sludge skeleton channels, charge neutralization, hydrophobic association effect were the primary mechanisms of SBF conditioning sludge dewatering. Additionally, SBF has an excellent economy as a sludge conditioner. This paper provided a new ideal for starch-based flocculants for improving the dewatering capacity of sludge treatment.

Automated summary

A green and cost-saving starch-grafted flocculant (SBF) was synthesized and its effect on the dewatering efficiency of sludge was studied. The results showed that SBF neutralized the negative charges in the sludge system, promoted sludge flocs size increase and EPS decomposition, resulting in a decrease in filter cake moisture content and specific resistance to filtration. Additionally, SBF changed the secondary structures of protein, reducing hydrophilic substances and increasing hydrophobic substances, thus improving the hydrophobicity of molecules and increasing the dewatering capacity of sludge. The construction of sludge skeleton channels, charge neutralization, and hydrophobic association effect were identified as the primary mechanisms of SBF conditioning sludge dewatering.