Abstract
Cocoamidopropyl betaine (CAPB), which is a biodegradable ampholytic surfactant, has recently been found to dramatically enhance the aerobic digestion of waste activated sludge (WAS) in short-time aerobic digestion (STAD) systems. Therefore, it is important to understand the mechanisms in which CAPB enhances WAS aerobic digestion performance. Results showed that CAPB could dramatically enhance the solubilization of soluble proteins (PN), polysaccharides (PS), nucleic acids (NA) and humic-like substances (HS) in the STAD system within the initial 2 h. Then PN, PS and NA gradually decreased, while HS showed only minor decease. In addition, CAPB increased the proportion of low MW fractions (<20 kDa) from 4.22% to 39.4%, which are more biodegradable. Specific oxygen uptake rates and dehydrogenase enzyme activity results indicated that CAPB markedly improved the aerobic microorganism activities. Microbial community analyses and principle coordinate analyses (PCoA) revealed that CAPB increased the proportion of some functional microorganisms, including Proteobacteria, Planctomycetales, Acinetobacter, Pseudomonas and Aeromonas. The changes driven by CAPB could explain the enhanced performance of the STAD system for WAS aerobic treatment.
Highlights
As an important treatment method of waste activated sludge (WAS), aerobic digestion has been widely applied in middle and small wastewater treatment plants (WWTPs)[1,2,3]
As a widely used surfactant, cocoamidopropyl betaine (CAPB) was found to promote the fast removal of organics in WAS and the removal efficiency of volatile suspended solids (VSS) increased to 28.3% within 1 day, while previous studies reported have not reported removal efficiency higher than 20%
CAPB was biodegraded by the system with removal efficiency of 91.2% after aerobic digestion for 1 day
Summary
As an important treatment method of waste activated sludge (WAS), aerobic digestion has been widely applied in middle and small wastewater treatment plants (WWTPs)[1,2,3]. The surfactants adsorbed in WAS, can influence the sludge properties, which effects the aerobic digestion of WAS. Lozada et al.[12] studied the effects of nonylphenol ethoxylate (NPEO) surfactants on the bacterial diversity in lab-scale activated sludge reactors. CAPB, as a nontoxic and biodegradable ampholytic surfactant, is widely used in personal care products and surface cleaners[13], which can be directly discharged to municipal WWTP. WAS produced from municipal WWTPs contain CAPB that may influence the aerobic treatment of waste activated sludge. CAPB can be biodegraded by the system, and the removal efficiency at 24 h was 91.2% (Figure S2) It is of big significance for WAS aerobic treatment to further disclose the enhancement mechanisms
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