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Integrating alum sludge with waste-activated sludge in co-conditioning and dewatering: a case study of a city in south France


The unique geographical location of waterworks and wastewater treatment plant (WWTP) in Graulhet (France) profited the environmental resource integration and “Circular Economy.” Alum sludge from a local waterworks was introduced to co-conditioning and dewatering with waste-activated sludge from a nearby WWTP to examine the role of the alum sludge in improving the dewaterability of the mixed sludge. Experiments demonstrated that the optimal mixing ratio was 1:1 (waste-activated sludge/alum sludge, v/v). Alum sludge has been shown to beneficially enhance mixed sludge dewaterability, by decreasing both the specific resistance to filtration (SRF) and the capillary suction time (CST). Moreover, the optimal polymer (Sueprfloc-492HMW) dose for the mixed sludge (mix ratio 1:1) was 200 mg/L, highlighting a huge savings (14 times) in polymer addition without alum sludge involvement. In addition, cost-effective analysis of its potential full-scale application has demonstrated that the initial investment could be returned in 11 years. The co-conditioning and dewatering strategy can be viewed as a “win-win” strategy for the Graulhet, France, water and wastewater industry.

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The first author greatly acknowledges the Ph.D. scholarship received jointly from the University College Dublin, Ireland, and China Scholarship Council (CSC). The RAPSODEE Research Centre (CNRS UMR 5302), France, and the staff in Régie Municipale de l’Eaux et de l’Assainissement de Graulhet were also gratefully acknowledged for the technological support.

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Correspondence to Baiming Ren.

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Ren, B., Lyczko, N., Zhao, Y. et al. Integrating alum sludge with waste-activated sludge in co-conditioning and dewatering: a case study of a city in south France. Environ Sci Pollut Res (2020).

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  • Alum sludge reuse
  • Circular economy
  • Jar test
  • Sewerage sludge
  • Techno-economic analysis
  • Waterworks residues