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Phosphate recovery as hydroxyapatite from nitrified UASB effluent atneutral pH in a CSTR

Tijdschriftbijdrage - Tijdschriftartikel

The wastewater of the potato processing industry is typically rich in phosphorus. The effluent of a UASB of apotato processor was nitrified prior to phosphate recovery as hydroxyapatite. The nitrification of ammonium notonly removes the ammonium which avoids competing struvite formation but also consumes the double equimolaramount of dissolved inorganic carbon. The latter reduces calcium bicarbonate inhibition and carbonateprecipitation and makes the calcium available for calcium phosphate precipitation. After this biological pretreatmentphosphate was precipitated as hydroxyapatite (Ca5(PO4)3OH) at neutral pH values (7.83) in a laboratoryCSTR. This precipitation of hydroxyapatite consumed part of the inorganic carbon that remained afternitrification of the UASB effluent and the final yield was determined by the available Ca2+ ions. Both a higherpH (8.5–10.5) and a low [Ca2+]/[P] ratio initiate the coprecipitation of carbonates and magnesium phosphate.A conventional nitrification downstream the UASB facilitates phosphate recovery as a calcium phosphate salt.This calcium phosphate removal route is presented as an alternative to the currently applied struvite process.
Tijdschrift: Journal of Environmental Chemical Engineering
ISSN: 2213-2929
Issue: 4
Volume: 6
Pagina's: 4413 - 4422
Jaar van publicatie:2018