Evaluation and comparison of centralized drinking water softening technologies: Effects on water quality indicators.

Autor: Tang C; Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet 115, 2800 Kgs. Lyngby, Denmark., Rygaard M; Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet 115, 2800 Kgs. Lyngby, Denmark. Electronic address: mryg@env.dtu.dk., Rosshaug PS; HOFOR, Greater Copenhagen Utility, Ørestads Boulevard 35, 2300 København S, Denmark., Kristensen JB; NIRAS, Sortemosevej 19, 3450 Allerød, Denmark., Albrechtsen HJ; Department of Environmental Engineering, Technical University of Denmark, Bygningstorvet 115, 2800 Kgs. Lyngby, Denmark.
Jazyk: angličtina
Zdroj: Water research [Water Res] 2021 Sep 15; Vol. 203, pp. 117439. Date of Electronic Publication: 2021 Jul 15.
DOI: 10.1016/j.watres.2021.117439
Abstrakt: Drinking water softening is often implemented to increase consumer convenience e.g. by reducing lime scaling and soap use. Softening reduces hardness, but changes also the overall mineral composition of the water, depending on the technology. A broad spectrum of effects from softening has to be considered in relation to e.g. health and corrosion when selecting softening technology and design, otherwise adverse effects may be overlooked in the attempt to increase consumer convenience. We here provided a framework for evaluating softening technologies using water quality indicators for lime scaling, soap use, corrosion, human health, taste and removal of contaminants. None of the evaluated softening technologies scored positive on all the included water quality indicators. Precipitation technologies (lime/soda-ash softening and pellet softening) reduce the predicted copper and lead release, but negatively affect stainless steel corrosion expressed by the Larson Ratio. Pellet softening does not remove magnesium, which may limit the achievable softening depth, but maintains a protective effect against cardio-vascular diseases. Strong-acid cation exchange is not expected to affect the included corrosion indicators, whereas the effects from membrane separation (nanofiltration and reverse osmosis) and weak-acid cation exchange depend on the specific source water and process design. All the evaluated technologies reduce hardness, calcium carbonate precipitation potential (CCPP) and atopic eczema, but have potential adverse effects on dental carries (expressed by DMF-S). Our framework provides a better understanding of softening and can prepare water utility planners and managers for better decisions that balance the positive and adverse effects from drinking water softening.
(Copyright © 2021. Published by Elsevier Ltd.)
Databáze: MEDLINE
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