Design Considerations of a Packed Calcite Bed for Hardening Desalinated Water

Shemer, Hilla; Hasson, David; Semiat, Raphael

doi:10.1021/ie302975b

Cited by 13 publications

(5 citation statements)

References 15 publications

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“…CaCO3 + CO2 + H2O → Ca 2+ + 2 HCO3 -(Eq. 1) Several researches have shown that calcite filtration is a reliable remineralization method as no continuous chemical addition is required and calcite is inexpensive, readily available, safe to handle and easy to store (Shemer et al, 2013, Van Der Laan. H., 2016.…”

Section: Introductionmentioning

confidence: 99%

Impact of media coating on simultaneous manganese removal and remineralization of soft water via calcite contactor

et al. 2019

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The aim of this study was to investigate the negative impact of a newly-formed manganese (Mn)layer on calcite dissolution in the long-term operation of a calcite contactor. Simultaneous removal of Mn and remineralization of soft water in an up-flow calcite contactor was conducted and led to a progressive loading of Mn into the calcite matrix. The calcite contactor demonstrated high Mn removal; however, the hardness release decreased from 32 to 20 mg CaCO3 L -1 after 600 h of operation on a high Mn concentration (5 mg L -1 ) feed. For an elevated Mn concentration (i.e. 5 mg Mn L -1 ) in the feed water, the coated layer was mainly composed of Mn which inhibits the mass transfer from the calcite core to the liquid phase. The superficial layer was identified as 5.2% Mn oxides (MnOx) by X-ray photoelectron spectroscopy (XPS). Therefore, it is postulated that Mn removal starts with an ion exchange sorption reaction between soluble Mn 2+ from aqueous phase and Ca 2+ from the CaCO3 matrix which is followed by a slow recrystallization of MnCO3 into MnO2. On the other hand, when the Mn content in the feed water was lower (i.e. 0.5 mg Mn L -1 ), a considerably lower amount of MnOx was detected on the coated media. For all the examined conditions, the formation of this coating improved Mn removal due to the autocatalytic nature of the adsorption/oxidation of dissolved manganese by MnOx. A mechanistic model based on calcite dissolution and the progressive formation of a MnO2 layer was implemented in PHREEQC software to predict the reduction in hardness release expected in long-term operation. The model was calibrated with experimental data and resulted in realistic breakthrough curves. In order to accurately predict the pH of the effluent stream, a slow-rate recrystallization of MnCO3 into MnO2 was implemented (compared to the fast precipitation of MnO2 or the absence of MnO2 formation).

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Section: Introductionmentioning

confidence: 99%

Impact of media coating on simultaneous manganese removal and remineralization of soft water via calcite contactor

et al. 2019

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“…Prolonging the contact time of the feed water with the media is not an economically attractive option as the investment cost of the process would increase. Improved performance of the calcite beds by CO2 injection is mentioned in the literature [12,13]. However, for purpose of the domestic GW treatment, CO2 injection complicates the operation and maintenance of the process and would also add an additional cost.…”

Section: Resultsmentioning

confidence: 99%

“…Despite the wealth of information on the effectiveness of implementing a calcite contactor to remineralize desalted RO permeates [12,13] and its ability to adsorb divalent metallic cations on its surface [14,15,16], to the best of our knowledge, removal of Mn and Fe from a soft water while simultaneously adjusting its hardness level (without dosing CO2) by means of a calcite contactor is not addressed in the scientific literature. In this perspective, the aim of this research is to design a simple and compact, yet robust hybrid HFNF–calcite contactor process for domestic treatment of GWs (containing a high level of Mn, Fe and NOM).…”

Section: Introductionmentioning

confidence: 99%

Hybrid Hollow Fiber Nanofiltration–Calcite Contactor: A Novel Point-of-Entry Treatment for Removal of Dissolved Mn, Fe, NOM and Hardness from Domestic Groundwater Supplies

Haddad

Barbeau

2019

Membranes

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Groundwater (GW) is one of the main potable water sources worldwide. However, the presence of undesirable compounds and particularly manganese (Mn) and iron (Fe) (mainly co-existing in GWs) are considered as objectionable components of potable water for both health and aesthetic issues. As such, individual dwellings supplied by domestic wells are especially threatened by these issues. Current domestic treatment technologies are complicated to operate and even dangerous if improperly maintained (e.g., catalytic filtration) or consume salts and produce spent brine which pollutes the environment (i.e., ion exchange resins). Therefore, it is of prime importance to design a simple and compact, yet robust, system for Mn and Fe control of the domestic GW sources, which can reliably guarantee the desired Mn limit in the finished water ( 20 μ g/L). In the course of this study, we demonstrated, for the first time, that a hybrid hollow fiber nanofiltration (HFNF)–calcite contactor process is a promising alternative for treating domestic GWs with elevated levels of Mn, Fe, natural organic matter (NOM) and hardness. The efficacy of the HFNF membranes in terms of removal of Mn, Fe and NOM and fouling was compared with commercially available NF270 and NF90 membranes. The results revealed that HFNF (100–200 Da) and NF90 maintained considerably high rejection of Mn, Fe and NOM due to their dominant sieving effect. In contrary, the rejections of the above-mentioned components were decreased in the presence of high hardness for the looser HFNF (200–300 Da) and NF270 membranes. No membrane fouling was detected and the permeate flux was stable when the hard GW was filtered with the HFNF membranes, regardless of their molecular weight cut-off and transmembrane pressure, while the permeability of the NF270 and NF90 membranes steadily decline during the filtration. Integrating a calcite contactor, as a post filtration step, to the HFNF process yielded further Mn, Fe and NOM removals from the HFNF permeate and adjustment of its hardness level. The best performance was achieved when a blend of Calcite–CorosexTM ( 90 / 10 wt . % ) was used as a post-treatment to the tight HFNF (100–200 Da).

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“…The basic rate equation [15,19,21] is described by the difference between the calcium solution concentration [Ca +2 ] and the equilibrium calcium concentration [Ca +2 ] e on the solution-calcite interface:…”

Section: Rate Equationsmentioning

confidence: 99%