|
|
Crutchik, D., Rodrigues, S., Ruddle, D., & Garrido, J. M. (2018). Evaluation of a low-cost magnesium product for phosphorus recovery by struvite crystallization. J. Chem. Technol. Biotechnol., 93(4), 1012–1021.
Abstract: BACKGROUND: The development of a cost-effective process of struvite crystallization requires the selection of appropriate sources of alkali and magnesium. In this study, the effectiveness of two industrial grade products, MgO and Mg(OH)(2), as magnesium and alkali sources to recover phosphorus as struvite were investigated and compared in a first set of experiments. Subsequently, the use of industrial Mg(OH)(2) was compared in two different struvite crystallization systems, an upflow fluidized bed reactor (FBR) and a continuous stirred tank reactor (CSTR) coupled to a settler tank. RESULTS: At the same operational conditions, the consumption of MgO was higher than Mg(OH)(2) consumption. Moreover, industrial Mg(OH)(2) consumption for FBR and the CSTR operation was 1.6 and 1.1 1 mol Mg added mol(-1) P precipitated, respectively. This difference was caused by the high mixing intensity and the higher contact time between the Mg(OH)(2) slurry and the influent in the CSTR, favouring the conversion. CONCLUSIONS: Both industrial grade magnesium products are promising options for struvite crystallization. However, Mg(OH)(2) was more effective than the starting material, MgO, to recover phosphorus. Struvite crystallization by adding an industrial grade Mg(OH)(2) could be economically viable with regard to alternative physico-chemical P removal processes using metal salts, increasing the attractiveness of this P recovery process. (C) 2017 Society of Chemical Industry.
|
|
|
|
Jara-Munoz, P., Guzman-Fierro, V., Arriagada, C., Campos, V., Campos, J. L., Gallardo-Rodriguez, J. J., et al. (2019). Low oxygen start-up of partial nitrification-anammox process: mechanical or gas agitation? J. Chem. Technol. Biotechnol., 94(2), 475–483.
Abstract: BACKGROUND Partial nitrification-anammox (PN-A) is a widely recognized technology to remove nitrogen from different types of wastewater. Low oxygen concentration is the most used strategy for PN-A start-up, but stability problems arise during the operation; thus, in the present study the effects of the type of agitation, oxygenation and shear stress on the sensitivity, energy consumption and performance were evaluated. Recognition of these parameters allows considered choice of the design of an industrial process for nitrogen abatement. RESULTS A mechanically agitated reactor (MAR) was compared to a stable, long-term operation period bubble column reactor (BCR), both started under low dissolved oxygen concentration conditions. MAR microbial assays confirmed the destruction of the nitrifying layer and an imbalance of the entire process when the oxygen to nitrogen loading ratio (O-2:N) decreased by 25%. The granule sedimentation rate and specific anammox activity were 17% and 87% higher (respectively) in BCR. Economic analysis determined that the cost of aeration for the MAR and for the BCR were 23.8% and 1% of the total PN-A energy consumption, respectively. CONCLUSIONS The BCR showed better results than the MAR. This study highlights the importance of type of agitation, oxygenation and shear stress for industrial-scale PN-A designs. (c) 2018 Society of Chemical Industry
|
|
