Geothermal Water Management

Jochen Bundschuh, Barbara Tomaszewska, Jochen Bundschuh, Barbara Tomaszewska

• Publisher: CRC Press
• Year: 2018
• eBook ISBN: 9781317562573
• Topic: Technology & Engineering
• Subtopic: Environmental Management
• Index: Technology & Engineering

Availability of and adequate accessibility to freshwater and energy are two key technological and scientific problems of global significance. At the end of the 20th century, the deficit of water for human consumption and economic application forced us to focus on rational use of resources. Increasing the use of renewable energy sources and improving energy efficiency is a challenge for the 21st century. Geothermal energy is heat energy generated and stored in the Earth, accumulated in hydrothermal systems or in dry rocks within the Earth's crust, in amounts which constitute the energy resources. The sustainable management of geothermal energy resources should be geared towards optimization of energy recovery, but also towards rational management of water resources since geothermal water serves both as energy carrier and also as valuable raw material. Geothermal waters, depending on their hydrogeothermal characteristics, the lithology of the rocks involved, the depth at which the resources occur and the sources of water supply, may be characterized by very diverse physicochemical parameters. This factor largely determines the technology to be used in their exploitation and the way the geothermal water can be used. This book is focused on the effective use of geothermal water and renewable energy for future needs in order to promote modern, sustainable and effective management of water resources.

The research field includes crucial new areas of study:

• an improvement in the management of freshwater resources through the use of residual geothermal water;

• a review of the technologies available in the field of geothermal water treatment for its (re)use for energetic purposes and freshwater production, and

• the development of balneotherapy.

The book is aimed at professionals, academics and decision makers worldwide, water sector representatives and administrators, business enterprises specializing in renewable energy management and water treatment, working in the areas of geothermal energy usage, water resources, water supply and energy planning. This book has the potential to become a standard text used by educational institutions and research & development establishments involved in the geothermal water management.

Section II
Treatment of geothermal water for reuse

CHAPTER 5

Analytical procedures for ion quantification supporting water treatment processes

Ewa Kmiecik

5.1 INTRODUCTION

Rational and optimal use of existing water resources, including geothermal waters, is an extremely important issue. Geothermal waters can be used not only to extract energy but also in the context of improving the water balance and reducing or eliminating the need to inject waters into the formation as well as meet local needs (as drinking water and water for other household purposes). To this end, however, the water must be treated. The concentrate remaining after the treatment process contains valuable ingredients, which enables its use for industrial and residential purposes, in spas and/or for recreation purposes (Tomaszewska, 2011; Tomaszewska and Szczepański, 2014).

The effectiveness of the treatment process is monitored on the basis of the results of physical and chemical analyses of raw thermal waters, retentate and permeate. It is therefore important that these results be highly reliable. Obtaining sufficiently certain and reliable measurements of physicochemical parameters of water in practice entails the need for the laboratory to implement a quality assurance/quality control (QA/QC) system with respect to both field and laboratory testing.

The problem of controlling the quality of the data obtained in the process of monitoring the quality of groundwater has been discussed in both international (e.g. Fresenius et al., 1988; Garrett, 1969; Kolpin and Burkart, 1991; Kolpin et al., 1991; Nielsen, 1991, 2005; Ramsey, 1998; Ramsey and Thompson, 2007; Ramsey et al., 1992; Thompson and Howarth, 1976) and Polish literature (Kmiecik, 2011; Osmęda-Ernst et al., 1995a, 1995b, 1995c, 1996; Szczepańska and Kmiecik, 1998, 2005; Szczepańska et al., 1996; Witczak and Adamczyk, 1994, 1995) for a long time. Since there was no legislation that would make controlling the quality of such data mandatory, QA/QC programs were introduced only in exceptional cases.

The situation changed after the introduction of EU legislation: the Water Framework Directive (EU, 2000), Groundwater Directive (EU, 2006) and the so-called Technical Directive (EU, 2009). EU directives set new challenges for hydrogeologists linked to the implementation of new testing methods related to groundwater monitoring, hydrogeochemical data quality control and the methodology for assessing chemical status on the basis of verified data, taking into account their uncertainty.

The 2009 Directive (EU, 2009) clarified the technical specifications for the analysis and monitoring of the chemical status of waters, and set minimum criteria for the performance of analysis methods and the rules for demonstrating the quality of analytical results. Pursuant to its guidelines, laboratories that perform water chemical monitoring should follow the quality management system practices described in the EN ISO/IEC 17025: 2005 standard (ISO, 2005).

According to the EN ISO/IEC 17025: 2005 standard, laboratories must provide uncertainty estimates in their test reports because if uncertainty is not known, this may adversely affect the interpretation of results. ILAC (2002) recommends that uncertainty be stated in reports at least when test results must be compared to the results of other tests or to other numerical values, for example, those stated in specifications (threshold values). This is the case for example, with evaluating the suitability of geothermal waters for particular purposes (for human consumption after treatment, or for being discharged to surface waters).

The quality of geothermal waters directly in the well or within installations is evaluated on the basis of the results of chemical analyses covering a certain number of samples collected from a certain point/network/installation within a specified time interval. The results of chemical analyses obtained are dependent on the samples collected (small volumes of water that are subject to analysis). If the quality of water varies temporally or spatially, successive samples (from the point or installation in question) will exhibit different values of the physicochemical parameters measured. Each such set of results will allow the quality of the water to be assessed, but the estimates will differ.

Each single measurement is encumbered with uncertainty. In the measurement uncertainty estimation process, one must take into account all stages of hydrogeochemical data collection from sampling through sample transport, storage and analytical procedures to analysis results, since errors are generated at each of these stages.

This chapter discusses the quality control/quality assurance procedures applied to geothermal water testing. A detailed analysis has been carried out for one of the main indicators that usually determine the hydrogeochemical type of water, that is, calcium.

The main source of calcium in fresh groundwater is the leaching of rocks, and especially of carbonate minerals (calcite, dolomite) (Witczak et al., 2013). In typical drinkable water, the ratio of calcium to magnesium equivalent concentrations is around 3:4, with the exception of water circulating in dolomite rocks where this ratio approaches unity. The calcium content of water is most often controlled by the carbonate equilibrium and strongly depends on the CO₂ content and pH of water (Hem, 1989; Macioszczyk, 1987; Macioszczyk and Dobrzynski, 2007). Calcium is actively involved in the processes of sorption and ion-exchange with the clay substance contained in the rocks (Małecki et al., 2009).

Elevated levels of calcium in waters may have natural causes or may be related to anthropogenic pollution. Geogenic anomalies are mainly linked to the presence of gypsum where the Ca concentrations found are at levels of several hundred mg L⁻¹ (Motyka and Witczak, 1992).

Calcium in the form found in water is non-toxic. However, the calcium and magnesium content of water (total hardness) affects human health and can be troublesome in households and in the industry since it necessitates excessive consumption of detergents, and causes boiler scaling, etc. (WHO, 2011). Soft waters have an adverse effect on health (Selinus et al., 2005; Witczak et al., 2013). Polish regulations provide for an optimal range of concentrations resulting in a total hardness water level ranging from 60–500 mg L⁻¹ of CaCO₃. Hardness is mainly determined by calcium, so indirectly this is also the maximum allowable calcium concentration in water intended for human consumption. These are however, only additional requirements and regulations do not provide for mandatory water hardness supplementation.

In a number of countries, calcium content is not regulated directly since it is governed by the conductivity (EC) standard or, as in the United States, the standard for total dissolved solids (TDS). According to (Reimann and Birke, 2010), there are countries that regulate calcium content in water intended for consumption, for example, Austria (400 mg L⁻¹), Albania, Bosnia, Serbia (200 mg L⁻¹), Bulgaria (150 mg L⁻¹), Czech Republic (30–80 mg L⁻¹), Russia (130 mg L⁻¹), Slovakia (more than 30 mg L⁻¹) and Sweden (100 mg L⁻¹) (Witczak et al., 2013).

Calcium is also an important component of geothermal waters from the point of view of extracting them. Clogging is a problem that accompanies the extraction of thermal waters and directly influences the energy production cost for example. The intensity of this process depends mainly on the physicochemical composition of water and the presence of, inter alia, calcium ions. During the geothermal water cooling process, several physicochemical reactions take place, as a result of which the thermodynamic state of water changes. This leads to the precipitation of the minerals dissolved in the water (scaling), causing the clogging of the near-well zone and the active zone and limiting the productivity and absorption capacity of wells (Tomaszewska, 2008; Kleszcz ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• About the book series
• Editorial board
• List of contributors
• Editors’ foreword
• About the editors
• Acknowledgements
• Section I Resources, geochemical properties and environmental implications of geothermal water
• Section II Treatment of geothermal water for reuse
• Section III The uses of geothermal water in agriculture
• Section IV The uses of geothermal water in balneotherapy
• Subject index
• Book series page