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Titel |
Biochars made from agro-industrial by-products remove chlorine from water and wastewater |
VerfasserIn |
Andreas Tzachristas, Ioannis D. Manariotis, Hrissi K. Karapanagioti |
Konferenz |
EGU General Assembly 2017
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 19 (2017) |
Datensatznummer |
250137698
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Publikation (Nr.) |
EGU/EGU2017-494.pdf |
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Zusammenfassung |
Chlorination is the most common disinfection process for water and wastewater. For the
industrial use of water in food production, chlorine can add undesired taste and odor to the
final product. For this reason, dechlorination is desired for food industries that use
municipal tap water. For treated wastewater discharge or reuse, chlorine can be toxic to
the receiving aqueous systems and to the irrigated plants. In both the above cases,
dechlorination is also required. Traditionally activated carbon has been used as the
ideal material for the removal of chlorine. The main mechanisms that describe
the interaction between activated carbon and HOCl or OCl- are described by the
following equations (AWWA, 1990): HOCl + C* → C*O + H+ + Cl- (1), OCl- + C* →
C*O + Cl- (2) Where C* and C*O represent the activated carbon surface and a
surface oxide, respectively. The present study proposes the use of agro-industrial
by-products for the production of biochars that will be used for dechlorination of
tap-water used for food-industry production. Different raw materials such as malt
spent rootlets, coffee residue, olive and grape seeds, etc. are used for the production
of biochar. Various temperatures and air-to-solid ratios are tested for optimizing
biochar production. Batch tests as well as a column test are employed to study the
dechlorination kinetics of the different raw and biochar materials as well as those of
commercial activated carbons. The removal kinetics are faster during the first hour;
then, removal continues but with a slower rate. Most of the biochars tested (with 3
mg of solid in 20 mL of chlorine solution at initial concentration Co=1.5 mg/L)
demonstrated removal efficiencies with an average of 9.4 ± 0.5 mg/g. For the two
commercial activated carbons, removal efficiencies were 11.4 ± 0.2 mg/g. The
first-order constant k1 ranged between 0.001 and 0.014 (min-1) for the biosorbents
and the biochars and it was equal to 0.017 (min-1) for the commercial activated
carbons. Consequently, the half-life time ranged between 50 and 700 (min) for the
biosorbents and the biochars and it was equal to 41 (min) for the commercial activated
carbons. The column experiment also showed positive results; A breakthrough for
concentrations higher than 10(AWWA) 1990 Water quality and treatment, a handbook of
community water supplies, Fourth edition, American Water Works Association Fourth
edition. |
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