Abstract
The objective of this research was to obtain struvite from digested matter from a bio rural digester fed with bovine manure. To determine operating variables to recover struvite (PO43- and NH4+ ions), researchers developed an experiment design in which they evaluated the combined effect of the Mg2+: PO43- molar ratio (1.5:1; 2.5:1 and 3.5:1), reaction time (10, 50 and 90 min) and stirring speed (100, 450 and 800 rpm). The recovery rates obtained were 55±4.94 % and 58±7.72 % for NH4+ and PO43- respectively. The favorable conditions were 1.5 molar ratio, 50 minute reaction time and 450 rpm stirring speed. Struvite crystal formation and composition were confirmed using petrographic microscopy and infrared radiation. Struvite yield was 295.75 mg /l from digestate employed.
Highlights
Low-cost digesters are part of an attractive technology for anaerobic waste treatments in developing countries
The highest recovery percentages can be seen from hour 16 to hour 25, about 80% to 93% and 88% to 93%for NH4+ and PO43- respectively (Lee et al, 2015; Rahman, et al, 2014; Ryu & Lee, 2010)
The optimal operation conditions to nutrients recovery from real digestate via struvite precipitation were determined by a composed central design
Summary
Low-cost digesters are part of an attractive technology for anaerobic waste treatments in developing countries. In Latin America, there are approximately 1.000 low cost digesters installed, with a capacity ranging from 2 to 100 m3 (Martí-Herrero, et al, 2016). These systems are mainly fed with cattle manure to produce biogas (a CH4-CO2 mixture) which is mainly used to cook (Kinyua, Ergas, & Rowse, 2016). Anaerobic digestion (AD) produces biogas (30% of the digestion product) and digestate or biogas sludge that corresponds to 70%. The biogas sludge contains most of the nutrients (N and P) of the original substrate (Rivera et al, 2012)
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