Physical
conditioners or skeleton builders are usually used to
improve the dewaterability of sewage sludge. In this study, low-cost
rice husk (RH) was evaluated as an alternative skeleton builder and
combined with Fe2+ and sodium persulfate (SPS) for sewage
sludge conditioning. The results show that the sewage sludge conditioned
with RH and Fe2+/SPS showed good dewaterability, and the
capillary suction time was reduced by 92.8% under optimal conditions.
With use of response surface methodology, the optimal composite conditioner
concentrations were 151.5 mg/g dry solid (DS) of SPS, 46 mg/g DS of
Fe2+, and 333 mg/g DS of RH. After the sludge was conditioned
with Fe2+/SPS, some extracellular polymeric substances
(EPS) were destroyed, which resulted in the dissolved protein and
polysaccharide amounts in the filtrate increasing. The water content
analysis indicated the bound water was converted to free water because
of the EPS degradation. The particle size analysis showed that the
sludge flocs became smaller. After the addition of RH, the sludge
formed a stratified, porous structure that improved the sludge compressibility
and provided outflow passages for free water, which enhanced the sludge
dewaterability. These results indicated that combining persulfate
oxidation with RH conditioning is a promising strategy to improve
sludge dewaterability.
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