Phosphorous recovery as calcium phosphate from UASB effluent after nitrification with or without subsequent denitrification

Wastewater of potato processors contains high amounts of phosphorus and its recovery as calcium phosphate (CP) is investigated. In contrast to struvite, CP can be cotreated with phosphorous ore in phosphoric acid production, as far as it does not contain too much magnesium phosphate. The precipitation of CP was studied from the effluent of an upstream anaerobic sludge blanket reactor (UASB) after lab scale nitrification or lab scale nitrification and denitrification by batch experiments and continuous experiments. Nitrification excludes the possibility of struvite precipitation but did not result in complete removal of dissolved inorganic carbon (DIC). Only a narrow window at neutral pH is available for magnesium-free calcium phosphate precipitation. The additional denitrification caused a pH increase, which resulted in an unwanted magnesium phosphate precipitation and an increase in DIC, causing an increase of calcium carbonate contamination. The saturation index (SI) of CP can be enhanced by increasing the molar Ca/P ratio in the effluent, but this enhances also the contamination with calcium carbonate. Calcium chloride added in a tenfold molar excess relative to the phosphate-P concentration (a total molar Ca/P ratio of about 13) to nitrified effluent resulted in a phosphate recovery as CP of 83 %, but in all conditions, it was difficult to obtain carbonate-free CP.

Jaar van publicatie:2020

BOF-keylabel:ja

IOF-keylabel:ja

BOF-publication weight:6

CSS-citation score:1

Authors from:Higher Education

Toegankelijkheid:Open