Advances in Water Purification Techniques

Meeting the Needs of Developed and Developing Countries

Satinder Ahuja

• Publisher: Elsevier
• Year: 2018
• Print ISBN:
  9780128147900
• eBook ISBN:
  9780128147917
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

Advances in Water Purification Techniques: Meeting the Needs of Developed and Developing Countries provides a variety of approaches to water purification that can help assist readers with their research and applications. Water contamination problems occur frequently worldwide, hence the most updated knowledge on water purification systems can be helpful in employing the right type of filter or other mechanism of decontamination. The problems with arsenic contamination of water in Bangladesh and the lead problem in Flint, Michigan remind us of the need to monitor water pollution rigorously, from both point and non-point sources. - Provides a valuable resource on how to solve water contamination problems or develop new approaches to water purification - Presents advanced methods for monitoring water contamination - Describes various approaches to water purification - Encourages new developments in water purification techniques - Includes methods for assessing and monitoring environmental contaminants - Covers recent advancement in molecular techniques

Chapter 1

Overview of Advances in Water Purification Techniques

Satinder Ahuja Ahuja Consulting, Calabash, NC, United States

Abstract

This chapter provides a broad overview of advances in water purification techniques. These include bioremediation, advanced oxidation and reduction processes, physical methods based on sorption, etc. In addition, separations based on capacitive deionization and nanomaterials are covered. Sustainable solutions based on green chemistry are discussed in great detail. Finally, a path is provided to develop promising separation technologies into viable commercial products.

Keywords

Flocculation; Sorption; Nanomaterials; Microbial; Cyanobacteria, Arsenic; Fluoride; Selenium; Emerging contaminants; Capacitance deionization; Remediation; Green chemistry

1.1 Introduction

Over 1 billion people in the world do not have access to safe drinking water. Even though 70% of Earth is composed of water, only 3% of the total water available to us is fresh water and a minuscule 0.06% is easily accessible. As a result, over 80 countries in the world suffer from water shortages. According to the United Nations (UN), this situation is not likely to improve much: water shortages will be faced by an estimated 2.7 billion people by 2025. These shortages can lead to major conflicts over water. To sustain humanity, we need to improve water quality by various purification techniques to achieve water sustainability [1–8]. Achievement of this goal requires we meet our needs without compromising the ability of future generations to meet theirs [9]. To attain this objective, we will have to address technical, economic, and social issues [4] relating to purification of water for drinking; this must include reclamation of wastewater. Water reclamation (the act or process of recovering) is an absolute necessity because we have managed to pollute our surface water, and even groundwater in some cases, to a point that water needs to be purified for drinking [1].

Drinking water comes mainly from rivers, lakes, wells, and natural springs. These sources are exposed to a variety of situations that can lead to contamination of water. The failure of safety measures relating to production, utilization, and disposal of thousands of inorganic and organic compounds causes pollution of our water supplies. A number of water contaminants arise from the materials we frequently use to improve the quality of life [8] including the following:

• • combustion of coal and oil
• • detergents
• • disinfectants
• • fertilizers
• • gasoline combustion products and additives
• • herbicides
• • insecticides and pesticides
• • pharmaceuticals (including endocrine disruptors)
• • phthalates
• • radionuclides

For example, a 2002 US Geological Survey (USGS) found pharmaceuticals (hormones and other drugs) in 80% of streams sampled in 30 states of the United States. A very large quantity of antimicrobials and antibiotics is administered to healthy animals on US farms each year, and these compounds end up in our water supplies when the animal waste is not handled properly. There are a number of potential sources of water contamination: volatile and semivolatile compounds; improperly disposed chemicals; animal wastes; introduction of toxic agents by terrorists; wastes injected underground; and naturally occurring substances that can all contaminate drinking water. Furthermore, some emerging contaminants can impact water quality. Similarly, drinking water that is not properly treated or disinfected, or which travels through an improperly maintained distribution system (infrastructure), may also pose a health risk. It is important to recognize that a large number of inorganic/organic compounds that cover the entire range of the alphabet, from A to Z (arsenic to zinc), can cause contamination of our water supplies [10]. All chemicals are not necessarily harmful; zinc in small amounts is desirable, whereas, arsenic at concentrations as low as 10 parts per billion (ppb) is quite harmful. A variety of pollutants can come from wastewater because it is generally recycled to surface water or groundwater after some processing. Wastewater can originate from many places: households, industries, commercial developments, road runoff, etc. In addition, we have to contend with nonpoint sources of pollution. As diverse as the sources of wastewater are, so too are their potential constituents.

Recent water disasters in Flint, MI, and Wilmington and Fayetteville, NC, are distressing reminders of what can go terribly wrong. Instead of buying Lake Huron water from Detroit in an effort to save money, the city of Flint began drawing its water from the local river in April 2014. Residents started complaining about burning skin, hand tremors, hair loss, even seizures. In 2015, high levels of lead were found in the water supply of Flint. Unsafe levels have turned up in tap water in Washington, DC, in 2001; in Columbia, SC, in 2005; in Durham and Greenville, NC, in 2006; and in Jackson, MS, and Sebring, OH, in 2015. DuPont (Chemours) introduced GenX in 2009 to replace perfluorooctanoic acid (PFOA), a compound it used to manufacture Teflon and coatings for stain-resistant carpeting and waterproof clothes. GenX has been detected in the drinking water in Brunswick County, Fayetteville, and Wilmington, NC. In Fayetteville, soil and groundwater have also been affected. Levels of GenX in the drinking water of the Cape Fear Public Utility Authority in Wilmington averaged 631 ppt (parts per trillion), according to a study published by Knappe and coworkers in Environmental Science & Technology Letters in 2016. The Environmental Protection Agency (EPA) has set drinking water standards for PFOA at 70 ppt; however, they have not set standards for GenX. Moreover, the water utility companies in this area cannot filter out GenX at this time.

Another looming disaster may arise from harmful cyanobacterial algal blooms. In aquatic environments, they are likely to be a major worldwide problem, causing a significant adverse impact on public health. Microcystins are hepatotoxins produced by cyanobacteria. They also produce a wide variety of secondary metabolites, and most important, potent toxins called cyanobacterial toxins or cyanotoxins. They are known to affect a wide range of living organisms including humans. Cylindrospermopsin (CYN) is one of the most widely distributed cyanotoxins in water bodies. The CYN is produced by large groups of cyanobacteria that are highly adaptive and invasive and have been detected in tropical, subtropical, and even in temperate areas. Compared with microcystins, CYN can be actively released into the environment, leading to higher extracellular toxin concentrations than the intracellular levels. In 2016, Unregulated Contaminant Monitoring Rule 4 (UCMR4), which covers cyanotoxins, came into effect.

There is still another impending water disaster—plastics, especially microplastics, are a major problem. Microplastics can stunt fish growth and alter their behavior. The extensive use of plastics and their careless disposal has led to the pollution of various water bodies. Large parts of the Pacific Ocean are referred to as “plastic oceans,” where enormous gyres, about the size of Texas, are covered with plastic debris. The Pacific is the largest ocean realm on our planet, approximately the size of Africa—over 10 million square miles—and it is the home to two very large gyres of plastics. The Atlantic Ocean contains two more gyres, and other plastic oceans exist in other bodies of water.

1.1.1 Monitoring Ultratrace Contaminants

Over 700 different chemicals have been found in US drinking water—as it comes out of the tap! The EPA classifies 129 of these chemicals as being particularly dangerous and it sets standards for approximately 90 contaminants in drinking water. These standards, along with each contaminant’s likely source and its health effects, are available at http://www.epa.gov/safewater/mcl.html. Even though consuming tap water can be risky, there is no assurance that bottled water is any safer.

A better understanding of wastewater constituents and their abundance at different stages is a first step in recognizing appropriate opportunities for pretreatment. The composition of wastewater affects not only the treatment processes applied but also their source recovery opportunities. It is clear that wastewater contains pollutants/contaminants that have to be removed and/or reduced to safe levels before it is directed to a surface water source (river, ocean, bay, lake...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Preface
• Chapter 1: Overview of Advances in Water Purification Techniques
• Chapter 2: Global Water Challenges and Solutions
• Chapter 3: Water Supply and Water Quality Challenges in Panama
• Chapter 4: Contaminants of Emerging Concern: Occurrence, Fate, and Remediation
• Chapter 5: Monitoring Water Contaminants With Ion Chromatography
• Chapter 6: Advanced Oxidation and Reduction Processes
• Chapter 7: Capacitive Deionization (CDI): An Alternative Cost-Efficient Desalination Technique
• Chapter 8: Remediation of Selenium in Water: A Review
• Chapter 9: Status of Arsenic Remediation in India
• Chapter 10: Addressing the Arsenic Issue in the Lower Mekong Region—The Challenges and Systematic Approaches
• Chapter 11: Development of Synthetic Hydroxyapatite-Based Household Defluoridation Unit
• Chapter 12: Addressing Groundwater Fluoride Contamination Using Inexpensively Processed Bauxite
• Chapter 13: Transforming the Global Arsenic and Fluoride Crisis Into an Economic Enterprise: Role of Hybrid Anion Exchange Nanotechnology (HAIX-Nano) in Ballia, Uttar Pradesh and Nalhati, West Bengal
• Chapter 14: Green and Sustainable Pathways for Wastewater Purification
• Chapter 15: Water Purification: Treatment of Microbial Contamination
• Chapter 16: Taking Good Ideas to Great Products: Building Bridges Across the Technology Readiness Valley for Water Purification Technologies in Singapore
• Index