Abstract
Nowadays, fertilizers containing nitrogen and phosphorus are indispensable for medium and large-scale industrial agriculture. To meet the growing demand of nutrients and reduce the accompanied ecological footprint of primary fertilizer production, processes and technologies for nutrient recovery are necessary and have to be developed. This study represents the basis of an extension of the ion-exchange-loop-stripping process (ILS), which is a combined stripping and ion exchange process using natural zeolite for nitrogen recovery. In batch experiments with a special zeolite filled stirrer, the mechanism and kinetics of simultaneous ammonium and phosphate recovery by natural zeolite were determined. Zeolite loadings of 6.78 mg PO43− g−1 were reached and after regeneration, phosphate recovery rates up to 75% of the initial concentration were achieved. The speed of phosphate precipitation is mostly controlled by the pH value of synthetic wastewater. Phosphate removal in simultaneous experiments does not affect ammonium sorption onto zeolite. These findings and the different removal mechanisms of ammonium and phosphate lead to versatile applications in wastewater treatment and reveal great potential of natural zeolite in simultaneous nutrient recovery processes.
Highlights
As a result of the constantly growing world population, the demand of organic and inorganic fertilizer for food production increases every year [1]
This study shows further development possibilities of the ion-exchange-loop-stripping process (ILS) process [8,9] and kinetics of a simultaneous recovery process of ammonium (NH4 + ) and phosphate (PO4 3− ) from aqueous solutions
Based on the cation kinetics, it is obvious that calcium is the dominant cation in the exchange reaction with untreated natural zeolite
Summary
As a result of the constantly growing world population, the demand of organic and inorganic fertilizer for food production increases every year [1]. Overfertilization and the resulting eutrophication of surface and subsurface water present a global and persistent environmental problem [2,3]. Nutrient amounts in organic fertilizers like animal manure or biogas digestates are subject to fluctuations in process conditions, it is hard to fertilize plants with the appropriate quantity of nutrients. Harmful components in manure and sewage sludge, such as microplastics, germs, antibiotics and heavy metals accumulate in the soil and water. As a result of those problems the direct utilization of organic fertilizers in agriculture like manure, sewage sludge or biogas digestates is restricted by legal regulations of the European Commission [4]. Nutrient recovery can save energy in the primary production and prevent the contamination of soil and water by harmful substances
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