Nutrient Recovery from Human Urine Using Pretreated Zeolite and Struvite Precipitation in Combination with Freezing‐Thawing and Plant Availability Tests on Common Wheat

Abstract

The nutrient rich fractions in wastewater originating from human urine and can be recovered as solids for more efficient recycling, facilitated handling and storage for reuse in agriculture. Freezing and thawing can be used to concentrate the urine nutrients. Phosphorus (P) and nitrogen (N) can be precipitated as struvite [(Mg,Ca)(K,NH 4 )(PO 4 ) N 6H 2 O] by adding MgO and additional nitrogen can be recovered by using zeolites. The zeolite in this study was pretreated in two ways: (i) washed and (ii) washed and thermally treated. The P recovery was high (A 97%) and the N recovery was ca. 50 to 60%. There was no significant difference in the nitrogen recovery among the different pretreated zeolites or between the pretreated and the untreated zeolite. Freezing had a positive effect on the nutrient concentration. The acute toxicity of the supernatants was tested on Daphnia magna to evaluate the possibilities of discharging the remaining supernatants to a recipient. The supernatants from the frozen treatments and from the unfrozen and washed zeolites were much less toxic than those of the original urine. The minerals acted as slow-release fertilizers in climate chamber tests on spring wheat.

Recovery of nutrients from the liquid fraction of digestate: Use of enriched zeolite and biochar as nitrogen fertilizers

“…Nutrient-enriched clinoptilolite resulted in up to a fourfold and sixfold increase in yield and N uptake, respectively. These findings were in line with studies that report N-loaded zeolite to be a good source of N (Ganrot et al, 2008) and urine-enriched clinoptilolite to be as effective as chemical fertilizer in preliminary pot trials (Beler-Baykal et al, 2011;Kocatü rk and Baykal, 2012).…”

Recovery of nutrients from biogas digestate with biochar and clinoptilolite

“…This clearly showed that N from nutrient-enriched clinoptilolite was available to the grass. These findings were in line with studies that report nitrogenloaded zeolite to be a good source of N (Ganrot et al, 2008) and urineenrichedclinoptilolite to be as effective as chemical fertiliser in preliminary pot trials (Beler-Baykal et al, 2011;. Many researchers have reported a high retention of nitrogen on the surface of biochar, even when using KCl extraction for desorption, which should replace NH4 + ions with K + and result in high desorption ratios.…”

“…Clinoptilolite has been found to be efficient at removing orthophosphate from aqueous solutions (Milan et al, 1997;Ganrot et al, 2007;Allar & Beler-Baykal, 2013;Lin et al, 2015), even though orthophosphate is an anion and cannot be removed through ion exchange by clinoptilolite. Orthophosphate removal occurs via physical adsorption on Al 3+ sites of clinoptilolite (Sakadevan & Bavor, 1998;Ganrot et al, 2008).…”

“…It has been used for nutrient recovery from human urine with high efficiencies (Ganrot et al, 2007(Ganrot et al, , 2008Allar & Beler Baykal, 2015). As a natural mineral, it can be regarded as an easily available and reasonably-priced product since there are many deposits around the world (Inglezakis, 2005).…”

“…Several studies have described the use of clinoptilolite for ammonium, potassium and orthophosphate recovery with high efficiencies from source-separated human urine (Ganrot et al, 2007(Ganrot et al, , 2008Beler-Baykal et al, 2011;Allar & Beler Baykal, 2015) and the liquid fraction of digestate (Kocatürk et al).…”