Marine Impacts of Seawater Desalination

Science, Management, and Policy

Nurit Kress

• Publisher: Elsevier
• Year: 2019
• ISBN:
  9780128119549
• Topic: Sciences physiques
• Subtopic: Océanographie

Seawater desalination is increasing globally, and in light of this, it is necessary to look at the environmental and ecological impacts of desalination plants on the marine environment. Marine Impacts of Seawater Desalination: Science, Management, and Policy combines existing studies and new research into a unified work describing the interplay of seawater desalination and the marine environment. In particular, the book identifies knowledge gaps in the current data and recommends future research paths. The book also covers the established and emerging desalination processes and the policies and regulations applied to seawater desalination. Marine Impacts of Seawater Desalination is an ideal reference for engineers and developers working on environmental-related issues of seawater desalination, scientists and researchers studying these issues, as well as regulators and decision makers who can use this book as a useful guide for planning and operating desalination plants.

• A multidisciplinary approach to understanding the environmental impact of seawater desalination on the marine environment.
• Real-world data demonstrating the environmental effects of seawater desalination.
• Impact of seawater quality and marine organisms on desalination operations.
• Discussion of foreseeable future effects and significant areas for further research on seawater desalination.

Chapter 1

Introduction

Abstract

This introductory chapter provides a concise overview on topics associated with seawater desalination that are not covered in this book: a brief history of seawater desalination, the desalination market, the water-energy-food-ecosystem nexus, water policy, and the quality of desalinated water. It ends with a summary of the way forward for seawater desalination that is integrated within the book's chapters. Seawater desalination provides a new source of water, some say almost infinite, in contrast to the finite supply of fresh water from nature. However, it is expensive both financially and environmentally. Therefore, basic measures, such as reduced consumption, prevention of water loss, recycling and reuse should be implemented prior to desalination. The global demand for water is increasing and so is the water desalination market, evaluated at $13 billion in 2016. Energy and food demand are also increasing and are inextricably linked to water, giving way to the water-energy-food nexus approach. This approach addresses the integrated management of natural resources to ensure water, energy, and food security in a sustainable way, thus protecting the environment and the ecosystems functions. The establishment of seawater desalination as an economically viable and reliable freshwater source transformed water from a natural resource into a commodity. At the national level, states delegate seawater desalination to the private sector, which can handle such large-scale projects. At the international level, prior to seawater desalination there was an inherent advantage to nations being “upstream” near the water source. Seawater desalination shifted this advantage to “downstream” nations with coastal access that are now able to control their national water supply and even export the product water.

Keywords

Desalination market; Desalinated water quality; National and international water policy; Seawater desalination history; Water-energy-food-ecosystem nexus

How inappropriate to call this planet “Earth,” when it is clearly “Ocean”

Arthur C. Clarke

I chose to start this book with the ocean rather than with the obvious and more commonplace introductory statements like: “the growing global population”, “the increase in freshwater demand”, “the dwindling of the natural water sources” followed by “desalination as a solution”. This book is centered on the oceans as the source for freshwater supply through desalination and on the impact of desalination on the marine environment. However, the oceans are much more than a supplier of saline water to the desalination industry. They regulate climate and are vital for the preservation of life on Earth.

Most of the water (96.5%) on Earth is saline, undrinkable, and held within the oceans. Fresh water comprises 2.5% of the total water, with 1.7% in glaciers and ice caps, and thus inaccessible for use. Only 0.8% of the total global water is fresh and can be withdrawn for consumption. Moreover, the global distribution of fresh water is uneven; some areas are rich in water resources, such as the Amazon rainforest, while others are arid such as the Middle-East—North Africa region (Fig. 1.1). To overcome this uneven distribution, the ancient Romans transported water through aqueducts, Persian engineers constructed qanats (tunnels) to carry groundwater from high elevations down to dry areas, and, in 1991, Libya constructed the great man-made river that brought fossil groundwater from the Sahara to the coast.

Fig. 1.1 Global freshwater distribution. The uneven distribution is depicted in the total monthly rainfall in millimeters as recorded by NASA's Tropical Rainfall Measuring Mission on August 2016 (left panel) and the map of water scarcity indicator (WSI) (right panel). (Reproduced with permission from NASA Earth Observatory (left panel) and from GRID-Arendal (right panel) at http://www.grida.no/resources/5586, Philippe Rekacewicz, February 2006.)

Today, this uneven distribution of fresh water is exacerbated by population growth, increased use of water per capita, and climate change. Climate change affects weather and precipitation patterns and decreases the reliability of natural freshwater supply. Desalination is thus placed as a viable and reliable new source of water. Seawater desalination is especially appealing as half of the world's population and 75% of the large cities (> 5 million inhabitants) are located within 100 km from the coast. Desalination is recommended by the United Nations, through the goals of Agenda 2030 for Sustainable Development, as an essential tool to provide clean water and sanitation to the world's population. However, desalination is expensive. The capital expenditure to build a large seawater desalination plant ranges from $200 to $600 million, and the operating expenditure ranges from $0.5/m³ to $2/m³. Both expenses are highly dependent on the plant's individual features and on national policy.

This introductory chapter provides a concise overview on topics associated with seawater desalination that are not otherwise covered in this book: the early history of seawater desalination, the desalination market, water policy, and the quality of desalinated water.

1.1 A Brief History of Seawater Desalination

Distillation is one of mankind's earliest ways of obtaining fresh water from seawater. It mimics the hydrological cycle: when salt water is boiled, the heat causes water to evaporate, leaving the salt beyond. The vapor is cooled, recondensed and the fresh water is collected. Desalination and distillation are mentioned in biblical texts and in ancient Greek and Roman writings. In the Book of Exodus, Moses transformed the bitter waters at Marah to sweet water using a “tree”—a kind of purification method using plants—and the hydrologic cycle or distillation are mentioned in the Book of Job. Aristotle (384–322 BC) wrote: “Experiment has taught us that sea-water when converted into vapor becomes potable, and the vaporized product, when condensed, no longer resembles sea-water.” Pliny the Elder (AD 23–79) describes a method of hanging fleece over the side of a ship at night, just above the surface of the water, to collect water vapor during the evening and squeeze it out in the morning to provide fresh water.

The art of distillation advanced between the 1st and 3rd centuries AD with Maria the Jewess, the Greek Egyptian alchemist Cleopatra (both in Alexandria), and Alexander of Afrodisia. Their effort was geared mainly toward the production of scented oils and perfumes from natural products. This technology led to the development of the alembic condenser (Fig. 1.2) described by Zosimos of Panopolis. A process of boiling seawater over a fire on board a ship, with a natural sponge placed over the mouth of the container, was described in the 4th century AD. The water vapor condensed in the sponge, and water was squeezed out for drinking. The knowledge on distillation and work of early Greek, Persian, Egyptian and Islamic scholars was brought to Western Europe with the Moorish conquest.

Fig. 1.2 The Zosimos distillation apparatus, called Alembic, depicted by an unknown Byzantine Greek illustrator and reproduced by Marcelin Berthelot in 1887 (left panel, Wikimedia Commons). In the right panel is a picture of the first page of the publication by Nehemiah Grew (1641–1711) describing seawater desalination based on patents submitted by others.

Leonardo da Vinci (1452–1519) accurately described the hydrological cycle and suggested that pure water can be produced from a simple still on a kitchen stove. Seawater desalination to supply fresh water for sailors expanded from the late 1500s to 1700, the age of sea voyages. In particular, during the reign of Charles II (1660–85), patents for seawater desalination were issued in England (Fig. 1.2). Stephen Hales (1677–1761) discovered that the first product of the distillation (one-third of the seawater volume) was of much higher quality than the rest. Thomas Jefferson (1743–1826) published the “Report on the method for obtaining fresh water from salt” in 1791 stating, “And it would seem that all mankind might have observed that the earth is supplied with fresh water chiefly by exhalation from the sea, which is in fact an insensible distillation effected by the heat of the sun.”

In 1748 J.A. Nollet (1700–1770) discovered the process of osmosis in which a solvent will pass spontaneously through a membrane, in his case an animal bladder, from a dilute solution into a more concentrated one. By applying pressure to the more concentrated side, the flow of solvent could be slowed, stopped, or reversed, which led to the term reverse osmosis (RO). About two hundred years after this discovery, the process of reverse osmosis was developed for seawater desalination (see Chapter 2).

No real improvement of the distillation process occurred until the 1800s with the advent of steam engines and the need for pure water for marine boilers and trains. A patent was issued in 1897 for a mechanically driven vapor compression system and in 1900 for the concept of multi-stage flash distillation (MSF) (see Chapter 2). Distillers were installed in 1907 in Jeddah (KSA, Red Sea), in 1910 near Safaga, and in 1933 in Qusair (Egypt, Red Sea). A thermo-compression evaporator was installed in 1928 in Curacao. Membrane separation and electrodyalysis appeared between 1920 and 1930 but were not commercial because of lack of appropriate semipermeable membranes.

The first solar desalter was installed in 1872 in Las Salinas, Chile, with a capacity of 19 m³/day. Seawater distillation powered by solar energy was mentioned in 1943 and used in WWII in life rafts on ships and in 1953 as a possible water supply process in tropical islands. In addition, a chemical process was used to produce a compact, sealed, desalination kit for trans-ocean fliers forced down at sea during WWII. It was based on the addition of a base to precipitate the anions present in seawater and of acid to precipitate the cations. Each step was followed by filtration of the precipitate formed. The final product was “not unpleasant in taste.”

Desalination on a commercial scale started in 1957 using thermal processes with the onset of flash evaporation and MSF processes. The use of membrane processes (mainly RO) began to grow following the development of th...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Preface
• Acknowledgments
• Glossary
• Chapter 1: Introduction
• Chapter 2: Desalination Technologies
• Chapter 3: Seawater Quality for Desalination Plants
• Chapter 4: Theoretical Analysis of the Potential Impacts of Desalination on the Marine Environment
• Chapter 5: Early Observations of the Impacts of Seawater Desalination on the Marine Environment: From 1960 to 2000
• Chapter 6: Actual Impacts of Seawater Desalination on the Marine Environment Reported Since 2001
• Chapter 7: Policy and Regulations for Seawater Desalination
• Index