Model and experiment-based evaluation of seawater-based urine phosphorus recovery(SUPR)process

Leveraging seawater toilet flushing system in Hong Kong,China,a Seawater-based Urine Phosphorus Recovery(SUPR)process that integrates ureolysis and phosphorus(P)recovery was proposed in our earlier work.In this study,a thermodynamic model was applied to evaluate the effects of ureolysis and the seawater-to-urine mixing ratio(S/U ratio)on P precipitation in the SUPR system.The results suggested that effective P recovery was thermodynamically feasible across a wide range of S/U ratios,with elevated pH levels resulting from ureolysis being critical for P precipitation.Furthermore,a SUPR reactor was developed to validate this process.When the hydraulic retention time(HRT)exceeded 3 h and the S/U ratio was lower than 3:1,more than 98%of P could be recovered without urine storage,chemical dosage,or external mixing.Further decrease in the HRT and increase in S/U ratio caused flushing out of fine precipitates,resulting in a relatively low P recovery efficiency.However,this could be advantageous when downstream urine nitrification is implemented,as dilution of urine can alleviate the inhibitory effects of free ammonia and free nitrous acid,as well as overcome the P limitation problem,thus facilitating urine nitrification.Consequently,there is a trade-off between optimizing P recovery and nitrification efficiencies.

Diverse molecular compositions of dissolved organic matter derived from different composts using ESI FT-ICR MS

Dissolved organic matter(DOM)derived from various composts can promote significant changes of soil properties.However,little is known about the DOM compositions and their similarities and differences at the molecular level.In this study,the molecular compositions of DOM derived from kitchen waste compost(KWC),green waste compost(GWC),manure waste compost(MWC),and sewage sludge compost(SSC)were characterized by electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry(ESI FT-ICR MS).The molecular formulas were classified into four subcategories:CHO,CHON,CHOS,and CHONS.The KWC,MWC,and SSC DOM represented the highest fraction(35.8%-47.4%)of CHON subcategory,while the GWC DOM represented the highest fraction(68.4%)of CHO subcategory.The GWC DOM was recognized as the nitrogen-and sulfurdeficient compounds that were less saturated,more aromatic,and more oxidized compared with other samples.Further analysis of the oxygen,nitrogen-containing(N-containing),and sulfur-containing(S-containing)functional groups in the four subcategories revealed higher organic molecular complexity.Comparison of the similarities and differences of the four samples revealed 22.8%ubiquitous formulas and 17.4%,11.1%,10.7%,and 6.3%unique formulas of GWC,KWC,SSC,and MWC DOM,respectively,suggesting a large proportion of ubiquitous DOM as well as unique,source-specific molecular signatures.The findings presented herein provide new insight into the molecular characterization of DOM derived from various composts and demonstrated the potential role of these different compounds for agricultural utilization.