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Recalcitrant nutrient removal using heterogeneous struvite precipitation in anaerobic digestion dewatering centrate

University of British Columbia

The primary objective of this research was to remove recalcitrant nutrients from anaerobically digested sludge dewatering centrate. Recalcitrant nutrients are defined as small (<0.45 µm) particles or molecules containing bound phosphorus and/or nitrogen and are commonly referred to as non-reactive dissolved phosphorus and dissolved organic nitrogen. Recalcitrant nutrients will persist through wastewater treatment processes and contaminate treated wastewater. The situation is complicated by anaerobic digestion of solid residuals, which load a wastewater treatment facility with more recalcitrant nutrients through internal sidestream recirculation loops. Recalcitrant nutrient treatment may be required for wastewater treatment facilities looking to use anaerobic digestion for energy (biogas) recovery and meet stringent nutrient discharge requirement. A struvite precipitation methodology is proposed where salt crystals are encouraged to ballast colloidal particles through heterogeneous nucleation. Four biologically unique dewatering centrates were used to test the precipitation methodology on the variety of anaerobic digester configurations that can be expected from municipal wastewater treatment plant. The effect of digestion sludge retention time (2 day, 20 day) and digestion temperature (35°C, 55°C) on the removal of dissolved unreactive phosphorus and nitrogen was monitored. Averaged across all four centrates, the precipitation methodology resulted in dissolved unreactive phosphorus and nitrogen removal of 82.4% and 66.6%, respectively. Antimicrobial contaminants (triclosan, triclocarban) were observed in the precipitates at minute concentrations (<18 ng/g-dry solids). Therefore, heterogeneous struvite nucleation can provide a means of recalcitrant nutrient treatment and reactive nutrient recovery without the micropollutant burden of biosolids land application.

Text

2017-12-22

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/64144

Civil Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/