Effects of Surfactants on the Improvement of Sludge Dewaterability Using Cationic Flocculants

PLOS ONE, Dec 2019

The effects of the cationic surfactant (cationic cetyl trimethyl ammonium bromide, CTAB) on the improvement of the sludge dewaterability using the cationic flocculant (cationic polyacrylamide, CPAM) were analyzed. Residual turbidity of supernatant, dry solid (DS) content, extracellular polymeric substances (EPS), specific resistance to filtration (SRF), zeta potential, floc size, and settling rate were investigated, respectively. The result showed that the CTAB positively affected the sludge conditioning and dewatering. Compared to not using surfactant, the DS and the settling rate increased by 8%–21.2% and 9.2%–15.1%, respectively, at 40 mg·L−1 CPAM, 10×10−3 mg·L−1 CTAB, and pH 3. The residual turbidities of the supernatant and SRF were reduced by 14.6%–31.1% and 6.9%–7.8% compared with turbidities and SRF without surfactant. Furthermore, the release of sludge EPS, the increases in size of the sludge flocs, and the sludge settling rate were found to be the main reasons for the CTAB improvement of sludge dewatering performance.

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Effects of Surfactants on the Improvement of Sludge Dewaterability Using Cationic Flocculants

et al. (2014) Effects of Surfactants on the Improvement of Sludge Dewaterability Using Cationic Flocculants. PLoS ONE 9(10): e111036. doi:10.1371/journal.pone.0111036 Effects of Surfactants on the Improvement of Sludge Dewaterability Using Cationic Flocculants Yong Liao 0 Yongjun Sun 0 Huaili Zheng 0 Jun Zhai 0 Houkai Teng 0 Chun Zhao 0 Chuanliang Zhao 0 Vishal Shah, Dowling College, United States of America 0 1 Key laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University , Chongqing , China , 2 National Centre for International Research of Low-carbon and Green Buildings, Chongqing University , Chongqing , China , 3 CNOOC Tianjin Chemical Research and Design Institute , Tianjin , China The effects of the cationic surfactant (cationic cetyl trimethyl ammonium bromide, CTAB) on the improvement of the sludge dewaterability using the cationic flocculant (cationic polyacrylamide, CPAM) were analyzed. Residual turbidity of supernatant, dry solid (DS) content, extracellular polymeric substances (EPS), specific resistance to filtration (SRF), zeta potential, floc size, and settling rate were investigated, respectively. The result showed that the CTAB positively affected the sludge conditioning and dewatering. Compared to not using surfactant, the DS and the settling rate increased by 8%-21.2% and 9.2%-15.1%, respectively, at 40 mg?L21 CPAM, 1061023 mg?L21 CTAB, and pH 3. The residual turbidities of the supernatant and SRF were reduced by 14.6%-31.1% and 6.9%-7.8% compared with turbidities and SRF without surfactant. Furthermore, the release of sludge EPS, the increases in size of the sludge flocs, and the sludge settling rate were found to be the main reasons for the CTAB improvement of sludge dewatering performance. - Funding: This research was supported by the National Natural Science Foundation of China (Project No. 21177164), Major projects on control and rectification of water body pollution (Project No. 2013ZX07312-001-03-03), and the 111 Project (Project No. B13041). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. . These authors contributed equally to this work. About 3.1026109 tons of municipal wastewater are generated in China in 2007, 49.1% of which need to be treated by some biological processes. Large amount of sewage sludge have been produced in sewage treatment facilities [1]. Raw wastewater sludge contains huge amount of water along with organic solids, which causes problems in transportation, treatment, and disposal [2]. One important stage of sludge treatment prior to disposal is the reduction of sludge volume by sludge dewatering; this process reduces transportation and handling costs [3]. Nevertheless, sludge dewatering remains expensive [4]. Chemicals, such as alum, polymeric ferric sulfate, polyacrylamide, and chitosan, are typically incorporated in sludge to improve the dewaterability [57]. Flocculants, given at the fixed dosages, are commonly used in conditioning the physical and chemical properties of sludge to improve sludge the dewatering performance, while the polyacrylamide added to sludge is a widely used pretreatment procedure in the wastewater treatment plants (WWTP). The previous reports indicate that the surfactants and polyacrylamide could be used as the dewatering reagents to substantially decrease the moisture content in filter cakes [89]. Sludge conditioned by the surfactants has gained considerable attention because of their excellent performance in improving sludge dewatering. The surfactants alter the microorganism cell structure by allowing the cell materials to leave the attached surface and simultaneously dissolve this surface in aqueous solutions to improve sludge dewaterability [10]. Huang et al. [11] found that the presence of the surfactants in alum sludge systems was able to improve the sludge quality by reducing SRF and bound water content, as well as increasing settling rate, dewatering rate, and the solid content of the sludge cakes as long as the polyacrylamides were not used. Chu et al. [12] concluded that cationic (CTAB) and anionic surfactants sodium dodecyl sulfate (SDS) enhance the filtration efficiency; however, the former and the latter respectively increase and decrease the consolidation rate, respectively. CTAB and SDS mainly interact with the aggregate surface and interior, respectively. Besra et al. [1314] reported that the mechanism of the reduction of surface tension was responsible for the enhancement of the dewatering kaolin suspensions. The mechanism of the absorption of the complex surfactants in the presence of flocculants exhibits an important function in enhancing the dewatering of kaolin suspensions. In some cases, the reduction in surface tension and the increase in hydrophobicity or a combination of both are able to (...truncated)


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Yongjun Sun, Huaili Zheng, Jun Zhai, Houkai Teng, Chun Zhao, Chuanliang Zhao, Yong Liao. Effects of Surfactants on the Improvement of Sludge Dewaterability Using Cationic Flocculants, PLOS ONE, 2014, Volume 9, Issue 10, DOI: 10.1371/journal.pone.0111036