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Flocculants from wastewater
Group: Environmental Technology, Wageningen University
Promotor: prof. dr HHM Rijnaarts
Co-promotor: dr ir BG Temmink and dr ir H Bruning
The aim of this thesis was to valorise selected industrial wastewaters to extracellular polymeric substances (EPS) that can be employed as bioflocculants, heavy metal adsorbents and for other applications. To achieve this, it was important to study three aspects of the technology value chain: the production, characteristics and applications of EPS as flocculants and heavy metal adsorbents.
EPS production was combined with fresh and saline wastewater treatment, using substrates such as glycerol, glucose, acetate and ethanol to mimic different industrial wastewaters. Under nitrogen-limited conditions, as much as 30 - 69 % wastewater-COD could be recovered as EPS-COD. Moreover, EPS produced under such nitrogen-limited conditions possessed higher molecular weights (1-4 MDa) and showed better flocculation performances than EPS produced from excess nitrogen. Highly charged EPS (≥ 5 meq/g EPS) were also shown to have very high capacity to adsorb and recover heavy metals such as Cu, Pb, and Au.