ABSTRACT
Alum sludge, an Al-oxyhydroxide rich waste product from water treatment practices, has the potential to be valorized as a P adsorbent material. However, several challenges currently prevent its application as an adsorbent in industrial setting, i.e. a limited P adsorption capacity due to saturation by organic matter and a fine nature resulting in percolation problems in adsorption bed setups. In this study, granulation and subsequent calcination of alum sludge were proposed to overcome these issues and to improve the P adsorption properties of alum-based adsorbent (ABA) materials. The effect of calcination temperature on the physicochemical properties of granular material was examined using X-ray diffraction, mass-spectroscopy coupled thermogravimetric analysis, Fourier-transform infrared spectrometry and specific surface area analysis, combined with density and crushing strength measurements. The ABA material obtained at 550 °C showed superior P adsorption properties and, therefore, this material was selected for further P adsorption testing and characterization (scanning electron microscopy and sieving). Batch P adsorption tests showed that this material had a maximum P adsorption capacity of 7.27 mg-P g-1. Kinetic adsorption tests determined the effect of the solid-to-liquid ratio and the granule particle size on the P removal. Finally, the performance of the ABA-550 material was tested in a pilot-scale adsorption setup, using a surface water stream (0.47 mg-P L-1) at a flow rate of 200 L h-1. During the test, the P removal efficiency always exceeded 86%, while the material maintained its structural stability. The results of this study illustrate the potential of granulated/calcined ABA materials for P adsorption, paving the way for the industrial application of this novel, sustainable P removal technology.
Subject(s)
Water Pollutants, Chemical , Water Purification , Adsorption , Alum Compounds , Hydrogen-Ion Concentration , Kinetics , Phosphorus , SewageABSTRACT
The Antirrhinum genus has a considerable complexity in the scent profiles produced by different species. We have analyzed the genetic differences between A. majus and A. linkianum, two species divergent in the emission of methyl benzoate, methyl cinnamate, acetophenone, and ocimene. The genetic analysis showed that all compounds segregated in a Mendelian fashion attributable to one or two loci with simple or epistatic interactions. Several lines lacked methyl benzoate, a major Volatile Organic Compound emitted by A. majus but missing in A. linkianum. Using a candidate gene approach, we found that the BENZOIC ACID CARBOXYMETHYL TRANSFERASE from A. linkianum appeared to be a null allele as we could not detect mRNA expression. The coding region did not show significant differences that could explain the loss of expression. The intron-exon boundaries was also conserved indicating that there is no alternative splicing in A. linkianum as compared to A. majus. However, it showed multiple polymorphisms in the 5' promoter region including two insertions, one harboring an IDLE MITE transposon with additional sequences with high homology to the PLENA locus and a second one with somewhat lower homology to the regulatory region of the VENOSA locus. It also had a 778 bp deletion as compared to the A. majus BAMT promoter region. Our results show that the differences in scent emission between A. majus and A. linkianum may be traced back to single genes involved in discrete biosynthetic reactions such as benzoic acid methylation. Thus, natural variation of this complex trait maybe the result of combinations of wild type, and loss of function alleles in different genes involved in discrete VOCs biosynthesis. Furthermore, the presence of active transposable elements in the genus may account for rapid evolution and instability, raising the possibility of adaptation to local pollinators.
