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Publication
A novel approach for nutrients recovery from municipal waste as biofertilizers by combining electrodialytic and gas permeable membrane technologies
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Advisor(s)
Abstract(s)
The recovery of valuable materials from waste fits the principle of circular economy and sustainable use
of resources, but contaminants in the waste are still a major obstacle. This works proposes a novel
approach to recover high-purity phosphorus (P) and nitrogen (N) from digestate of municipal solid waste
based on the combination of two independent membrane processes: electrodialytic (ED) process to
extract P, and gas permeable membranes (GPM) for N extraction. A laboratory ED cell was adapted to
accommodate a GPM. The length of waste compartment (10 cm; 15 cm), current intensity (50 mA;
75 mA) and operation time (9 days; 12 days) were the variables tested. 81% of P in the waste was successfully extracted to the anolyte when an electric current of 75 mA was applied for 9 days, and 74%
of NH4
+ was extracted into an acid-trapping solution. The two purified nutrient solutions were subsequently used in the synthesis of a biofertilizer (secondary struvite) through precipitation, achieving an
efficiency of 99.5%. The properties of the secondary struvite synthesized using N and P recovered from
the waste were similar to secondary struvite formed using synthetic chemicals but the costs were higher
due to the need to neutralize the acid-trapping solution, highlighting the need to further tune the process
and make it economically more competitive. The high recycling rates of P and N achieved are encouraging
and widen the possibility of replacing synthetic fertilizers, manufactured from finite sources, by secondary biofertilizers produced using nutrients extracted from wastes.
Description
Keywords
Phosphorus Nitrogen Struvite Nutrient recycling Waste valorization Seawate