Characteristics of Changes in Particle Size and Zeta Potential of the Digestate Fraction from the Municipal Waste Biogas Plant Treated with the Use of Chemical Coagulation/Precipitation Processes

Agnieszka Urbanowska, Izabela Polowczyk, Małgorzata Kabsch-Korbutowicz and Przemysław Seruga
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Agnieszka Urbanowska: Department of Environment Protection Engineering, Faculty of Environmental Engineering, Wroclaw University of Science and Technology, 54-153 Wroclaw, Poland
Izabela Polowczyk: Department of Process Engineering, Technology of Polymer and Carbon Materials, Faculty of Chemistry, Wroclaw University of Science and Technology, 54-153 Wroclaw, Poland
Małgorzata Kabsch-Korbutowicz: Department of Environment Protection Engineering, Faculty of Environmental Engineering, Wroclaw University of Science and Technology, 54-153 Wroclaw, Poland
Przemysław Seruga: Department of Bioprocess Engineering, Wroclaw University of Economics, 53-345 Wrocław, Poland

Energies, 2020, vol. 13, issue 22, 1-12

Abstract: The organic fraction of waste is increasingly used for biogas production. However, the fermentation process used for this purpose also produces waste in the form of digestate in addition to biogas. Its liquid fraction can, among other things, be a source of water, but its recovery requires many advanced technological processes. Among the first in the treatment train is usually coagulation/chemical precipitation. Its application changes properties, including the size and zeta potential ( ζ ) of the fractions that have to be removed in subsequent processes. Changes in particle size distribution and ζ potential occurring in the liquid fraction of municipal waste biogas plant digestate and solutions after coagulation/chemical precipitation with FeCl?·6H?O, PIX 112 and CaO were analyzed. The particle size distribution of the raw digestate was wide (0.4–300 µm; up to 900 µm without ultrasound). The median particle diameter was about 12 µm. The ζ potential ranged from −25 to −35 mV in the pH range 5–12, and the isoelectric point (IEP) was at pH 2. The best treatment results obtained with the use of. 10 g FeCl??6H?O/dm³ shifted particle size distribution towards finer particles (median diameter: 8 and 6 µm, respectively, before and after ultrasound). The ζ potential decreased by about 5–10 mV in the pH range 2.5–12 without changing IEP. An amount of 20 g/dm³ of FeCl??6H?O caused the disappearance of the finest and largest fraction. d 50 was about 21.5 µm (17.3 µm after ultrasound). An amount of 20 g/dm³ of FeCl??6H?O generated a positive high electrokinetic potential in the range of pH 1.8–5. The IEP appeared at pH 8, and after reaching about −5 mV it again became positive at pH about 11.

Keywords: digestate; biogas plant; coagulation; chemical precipitation; size distribution; zeta potential (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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