Nutrient removal from UASB effluent in agro-industries

Phosphorus and nitrogen are important elements, making a major contribution to agricultural and industrial development, but their release to natural water bodies are the main causes of eutrophication. Anaerobic digestion yields effluents rich in ammonium and phosphate and poor in biodegradable organic carbon, thereby making them less suitable for conventional biological nitrogen and phosphorus removal. In addition, the demand for fertilizers is increasing, energy prices are rising and global phosphate reserves are declining. This requires both changes in wastewater treatment technologies and implementation of new processes. In this contribution the combination of an ureolytic MAP (magnesium ammonium phosphate) precipitation and autotrophic nitrogen removal is described on the anaerobic effluent of a potato processing company to obtain a more sustainable and cheaper method than conventional wastewater treatment processes. The results obtained during this experiment (6 weeks period) show that it is possible to recover phosphate as struvite and remove nitrogen with the autotrophic nitrogen process from wastewater after anaerobic digestion coming from a potato processing company. However further research is necessary to obtain stable results during several months, especially for the nitrite:ammonium ratio produced by the partial nitritation reactor

Economic evaluation of the precipitation of phosphate as struvite at pilotscale

A novel approach using ureolytic induced MAP formation, for the recovery of phosphate, has been economically evaluated. The ureolytic MAP crystallizationon has been tested on anaerobic effluent of a potato processing company in a pilot plant, with MgCl2.6H2O as magnesium source. The pilot plant showed a high phosphate removal efficiency of 82 ± 9 %, resulting in a final effluent concentration of 13 ± 7 mg/L PO4-P. XRD analyses confirmed the presence of struvite in the precipitate. During operation pH and the molar magnesium : ammonium : phosphate ratio are the most important operational parameters influencing MAP crystallization. Results show that for high phosphate concentrations in wastewater (e.g. 100 mg/L PO4-P) the ureolytic phosphate precipitation is a cost effective method (6.1 € kg-1 Premoved). Moreover, the technique is competitive with the chemical phosphate precipitation of struvite (6.2 € kg-1 Premoved)

Chemoorganotrophic Bioleaching of Olivine for Nickel Recovery

Bioleaching of olivine, a natural nickel-containing magnesium-iron-silicate, was conducted by applying chemoorganotrophic bacteria and fungi. The tested fungus, Aspergillus niger, leached substantially more nickel from olivine than the tested bacterium, Paenibacillus mucilaginosus. Aspergillus niger also outperformed two other fungal species: Humicola grisae and Penicillium chrysogenum. Contrary to traditional acid leaching, the microorganisms leached nickel preferentially over magnesium and iron. An average selectivity factor of 2.2 was achieved for nickel compared to iron. The impact of ultrasonic conditioning on bioleaching was also tested, and it was found to substantially increase nickel extraction by A. niger. This is credited to an enhancement in the fungal growth rate, to the promotion of particle degradation, and to the detachment of the stagnant biofilm around the particles. Furthermore, ultrasonic conditioning enhanced the selectivity of A. niger for nickel over iron to a value of 3.5. Pre-carbonating the olivine mineral, to enhance mineral liberation and change metal speciation, was also attempted, but did not result in improvement as a consequence of the mild pH of chemoorganotrophic bioleaching

Effects of Bioleaching on the Chemical, Mineralogical and Morphological Properties of Natural and Waste-Derived Alkaline Materials

Bioleaching is a potential route for the valorisation of low value natural and waste alkaline materials. It may serve as a pre-treatment stage to mineral carbonation and sorbent synthesis processes by increasing the surface area and altering the mineralogy of the solid material and by generating an alkaline rich (Ca and Mg) aqueous stream. It may also aid the extraction of high value metals from these materials (e.g. Ni), transforming them into valuable ore reserves. The bioleaching potential of several bacteria (Bacillus circulans, Bacillus licheniformis, Bacillus mucilaginosus, Sporosarcina ureae) and fungi (Aspergillus niger, Humicola grisea, Penicillium chrysogenum) towards the alteration of chemical, mineralogical and morphological properties of pure alkaline materials (wollastonite and olivine) and alkaline waste residues (AOD and BOF steel slags, and MSWI boiler fly ash) at natural pH (neutral to basic) was assessed. Bioleaching was conducted using one-step and two-step methodologies. Increased solubilisation of alkaline earth metals and nickel were verified. Alteration in basicity was accompanied by alteration of mineralogy. AOD slag experienced solubilisation-precipitation mechanism, as evidenced by the decline of primary phases (such as dicalcium-silicate, bredigite and periclase) and the augmentation of secondary phases (e.g. merwinite and calcite). Nickel-bearing minerals of olivine (clinochlore, lizardite, nimite and willemseite) significantly diminished in quantity after bioleaching. Altered mineralogy resulted in morphological changes of the solid materials and, in particular, in increased specific surface areas. The bioleaching effect can be attributed to the production of organic acids (principally gluconic acid) and exopolysaccharides (EPS) by the microorganisms. The similarities between fungal and bacterial mediated bioleaching suggest that biogenic substances contribute mostly to its effects, as opposed to bioaccumulation or other direct action of living cells

The use of alternative physical water treatment devices for the prevention of scale build-up in an industrial freshwater heat exchange system

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Comparison of struvite and hydroxyapatite precipitation for phosphate removal in wastewater from potato and vegetable industry

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'A Single reactor' Autotrophic Nitrogen Removal Process after Ureolytic Phosphate Precipitation to remove both endogenous and exogenous nitrogen

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Phophorus reclamation by end-of-pipe recovery as calcium phosphate from effluent of wastewater treatment plants of agroindustry

Phosphorus is essential for live and must be recovered from all possible secondary resources. One of these secondary resourcesmaybetheeffluentofawastewatertreatmentplantinwhichnoobviousmeasuresaretaken to remove or recover the phosphorus. Effluent water of the wastewater treatment facility of a potato processor was spiked with 40–50 mg phosphate-P.L−1 to simulate such a water that can be subjected to an end-of-pipe recovery of phosphate. Simulations with PHREEQC were calculated and batch experiments were performed. Continuously stirred tank reactors (CSTR) were fed with P-spiked effluent. Increasing the Ca/P ratio promoted calcium phosphate precipitation but increased also the calcium carbonate contamination. With calcium added in fourfold excess relative to endogenous phosphate-P concentration, 90 % removal can be obtained. For the recovery of phosphorus from this purified effluent the same Ca/P ratio is necessary than in the case where phosphorus is recovered from nitrified UASB effluent. The recovery is stimulated by aeration, which however should not be continuous and by the addition of 5 g L−1 hydroxyapatite and reaches up to 95 %. In contrast to what was expected based upon the batch experiments, but in agreement with the simulations, the precipitates contained up to 6 m% magnesium phosphate, which probably can further be reduced by using shorter hydraulic retention times in the reactor.status: Published onlin

Heat Stability and Isomerisation of Steviol Glycosides in Acid Medium

Solutions of steviol glycosides dissolved in aqueous acid (pH = 1 or 2) rapidly convert into iso-forms at 80 °Cstatus: publishe