Effect of Major Ions on Induction Time of Struvite Precipitation

Struvite precipitation from wastewaters has gained importance as a means of nitrogen and phosphorus treatment and recovery. While the aspects of process modeling and application have been widely studied, little attention was paid to process kinetics. This study attempted to evaluate the induction time of struvite precipitation for low ammonia concentrations and in the presence of ions commonly found in natural waters. Determination of induction time was based on absorbance measurements while conductivity and pH of the solutions were also monitored during the process. Results of the experimental study indicate that the presence of foreign ions is important in determining the induction time along with the degree of supersaturation. The presence of over 50 x 10–3 mol dm–3 sodium ions retarded induction time significantly. Calcium ions at 2.5 x 10–4 mol dm–3 concentration caused no marked change in the induction time. While carbonate ions had a slight effect, sulfate ions increased the induction time. Crystal morphology was also observed to be affected by supersaturation and the presence of foreign ions

Effect of Major Ions on Induction Time of Struvite Precipitation

Struvite precipitation from wastewaters has gained importance as a means of nitrogen and phosphorus treatment and recovery. While the aspects of process modeling and application have been widely studied, little attention was paid to process kinetics. This study attempted to evaluate the induction time of struvite precipitation for low ammonia concentrations and in the presence of ions commonly found in natural waters. Determination of induction time was based on absorbance measurements while conductivity and pH of the solutions were also monitored during the process. Results of the experimental study indicate that the presence of foreign ions is important in determining the induction time along with the degree of supersaturation. The presence of over 50 x 10–3 mol dm–3 sodium ions retarded induction time significantly. Calcium ions at 2.5 x 10–4 mol dm–3 concentration caused no marked change in the induction time. While carbonate ions had a slight effect, sulfate ions increased the induction time. Crystal morphology was also observed to be affected by supersaturation and the presence of foreign ions

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Effects of Ph on Calcium Carbonate Precipitation Under Magnetic Field

Magnetic field effect on CaCO3 precipitation is the key parameter in evaluating the effectiveness of Anti-scale MagneticTreatment (AMT). The purpose of this study was to investigate magnetic fields influence on CaCO3 precipitation inhigh and low super-saturated CaCO3 solution by varied pH CaCO3 solution using circulation flow fluid system. Theobservation results in the high super saturated solution (pH 8.5) showed the increase of precipited CaCO3 in magnetizedsolutions compared to those in non-magnetic solution during circulation process. In the low super-saturated CaCO3solution (pH 6.4) it was found that magnetic treatment increased CaCO3 precipitation after circulation process. In highsuper-saturated solution, magnetic field strengthens ion interactions, which reduce precipitation during circulationprocess. However, in low super-saturated CaCO3 solution, magnetic field weakens hydrate ion interaction whichindicated by decreasing of the conductivity of solution. It increases the precipitation of CaCO3 after the circulation ofmagnetization process has completed

Performance Improvement of a Sequencing Batch Reactor for Treating Tannery Wastewaters

[EN] Tannery wastewater has a high environmental impact due to its low biodegradability. Sequencing batch reactors (SBRs) are an established method for treating highly polluted wastewater. To minimize the hydraulic retention time (HRT) of the SBRs, various HRT values were tested and the best value was chosen according to the removal efficiency of the soluble chemical oxygen demand (COD). A series of experiments was then carried out with two cationic polyelectrolytes added to the system in two different modes to improve the effluent quality. Both modes were evaluated in terms of the soluble COD, suspended solid concentration, and turbidity of the final effluent. The results showed that reducing the HRT to two days did not diminish the COD removal efficiencies.This work was supported by the Universitat Politecnica de Valencia (Project Ref.: PAID-06-10-2269).Balaguer-Arnandis, E.; Cuartas Uribe, BE.; Bes-Piá, M.; Mendoza Roca, JA.; Galiana Aleixandre, MV. (2017). Performance Improvement of a Sequencing Batch Reactor for Treating Tannery Wastewaters. Chemical Engineering & Technology. 40(9):1666-1673. https://doi.org/10.1002/ceat.201600410S1666167340

Magnetic Field Effects on Redox Potential of Reduction and Oxidation Agents

Redox potentials of two reducing (sodium dithionite and glucose) and two oxidizing (hydrogen peroxide and sodium hypochlorite) agents were monitored at various concentrations and at different temperatures for 30–75 minutes after the exposure of their water solutions (glucose and hypochlorite solutions once; sodium dithionite and hydrogen peroxide solutions one, two and/or three-times) to the static magnetic field of flux density of 0.9 V s m–2. The aim of the investigation was to suggest improvements, i.e., intensification and stability, of the reduction-oxidation ability of selected agents applicable in textile fibre processing, primarily bleaching and vat dyeing. Results of the experiments show that magnetic treatment (of solutions) raises both the reducing ability of glucose and the oxidation ability of hydrogen peroxide and sodium hypochlorite, promising some technological and economical benefits for the textile industry as well as for other fields of chemistry