Abstract
Carboxymethyl chitosan (CMCS), acrylamide, and methacryloxyethyltrimethyl ammonium chloride were used as co-monomers to produce a sludge dewatering agent carboxymethyl chitosan-graft-poly(acrylamide-methacryloxyethyltrimethyl ammonium chloride) (CCPAD) by UV-induced graft polymerization. Single-factor experiments and response surface methodology were employed to investigate and optimize the grafting rate, grafting efficiency, and intrinsic viscosity influenced by the total monomer concentration, CMCS concentration, cationic degree, pH value, and illumination time. The structure, surface morphology, and thermal stability of CCPAD were characterized by infrared spectroscopy, hydrogen nuclear magnetic resonance, X-ray diffraction, scanning electron microscopy, and differential thermal-thermogravimetry. The raw sludge with 97.9% water content was sourced from the concentrated tank of a sewage treatment plant and used in the sludge condition experiments. In addition, CCPAD was applied as the sludge conditioner to investigate the effects of cationic degree, intrinsic viscosity, and pH on the supernatant turbidity, moisture content, specific resistance to filtration, and sludge settling ratio. Moreover, the mechanism of sludge conditioning by CCPAD was discussed by examining the zeta potential and extracellular polymeric substance (EPS) content of the supernatant. The sludge dewatering results confirmed that CCPAD had excellent performance for improving sludge dewaterability.
Highlights
Municipal sewage treatment plant sludge has high organic content, unstable nature, fine particles, large specific surface area, and negative charge [1]
Sludge composition markedly varies depending on the source of the sewage, the sewage treatment process, and the season [2]
The treatment and disposal of sludge have become an important step in sewage treatment such that sludge treatment is an important standard for Polymers 2019, 11, 95; doi:10.3390/polym11010095
Summary
Municipal sewage treatment plant sludge has high organic content, unstable nature, fine particles, large specific surface area, and negative charge [1]. This substance can form a dispersion system with poor settling properties. Sludge composition markedly varies depending on the source of the sewage, the sewage treatment process, and the season [2]. As a by-product of wastewater treatment, the sludge contains pathogenic bacteria, parasite eggs, heavy metals, and other substances. The sludge contains heavy metals and toxic substances that pass through the food chain and eventually enter the human body with safety risks [3]. The treatment and disposal of sludge have become an important step in sewage treatment such that sludge treatment is an important standard for Polymers 2019, 11, 95; doi:10.3390/polym11010095 www.mdpi.com/journal/polymers
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