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Mineral precipitations and hydrochemical evolution of brines in graduation towers
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Accepted version
Date
2021-04-15
Authors
Ostwald, Laura-Jane
Banning, Andre
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Publisher
Springer
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Abstract
The purpose of this study is to examine hydrochemical changes of saline groundwater and precipitation of mineral phases during evaporative graduation processes. Therefore, concentrated brines and mineral precipitates were sampled at four graduation towers with differing evaporation approaches. Solid phase compositions were qualitatively and quantitatively analysed. Hydrochemistry changes of dissolved ion concentrations during successive evaporation was assessed by comparing natural with concentrated brines. PHREEQC was used to simulate sequence and quantity of mineral precipitates. Finally, a prognosis for expected precipitations of a newly built graduation tower was made using PHREEQC modelling. The identified mineral phases included calcite, aragonite, gypsum and halite in varying proportions. Concentrations of all investigated ions (except bicarbonate) increase, eventually leading to supersaturation and sequential precipitation of evaporite minerals. Modelled saturation indices show that calcite is the first and halite is one of the last precipitating phases at all sites. Further calculated precipitates include the carbonates dolomite, siderite and strontianite; manganese oxide and hematite; and the sulphates baryte, celestine and gypsum which precipitate depending on local hydrogeochemistry and graduation conditions. Calculated precipitation quantities reach a maximum of 48.6 g/L of applied natural brine at an evaporation grade of 90%. After 25 years, the total expected mass of precipitates at the new graduation tower is about 34.4 t for a graduation process up to a salt content of 19%, and about 356 t for a permanent evaporation grade of 90%.
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Keywords
Concentrated brine , Evaporite mineralogy , Germany , Graduation tower , Saline groundwater , Münsterland Cretaceous Basin
Citation
Ostwald, L. J. and Banning, A. (2021) ‘Mineral Precipitations and Hydrochemical Evolution of Brines in Graduation Towers’, Environmental Processes, 8 (2), pp. 729–746. doi: 10.1007/s40710-021-00511-5
Copyright
© The Author(s), under exclusive licence to Springer Nature Switzerland AG 2021. This version of the article has been accepted for publication, after peer review and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s40710-021-00511-5