Introduction to Water Treatment: A Historical Perspective on Technological Development and Future Landscape

Anirban Roy1*, Anupam Mukherjee1, Aditi Mullick2 and Siddhartha Moulik2┼

1Water-Energy Nexus Lab, Department of Chemical Engineering Goa, BITS Pilani, Goa, India

2Cavitation and Dynamics Lab, Process Engineering and Technology Transfer Division, Indian Institute of Chemical Technology, Hyderabad, India

Abstract

Efficient water production, recovery, recycling and management underlines the degree of sustainability of the resource. In the last decade, water has been considered as the "new oil" and as the popularity of non-renewable energy sources are slowly starting to fade, there is no alternative to water. In this regard, this book focuses on technological advances for water treatment in four categories: (i) advanced oxidation technologies, (ii) nanoparticles for water treatment, (iii) membrane separations, and (iv) other emerging technologies or processes. A wide variety of pollutants have also been discussed like acidic wastewater treatment, metallurgical wastewater, and textile wastewater as well as groundwater. More often than not, a stand-alone technology is not the solution for sustainability and one requires a process to be developed and technologies to be integrated. In this regard, the book will give valuable insights into both understanding of technologies as well as possible integration of technologies for a given waste stream to recycle and purify water.

Keywords: Advanced oxidation, membrane, nanoparticle, metallurgical wastewater, acidic wastewater, groundwater

Introduction

The current water crisis looming over a hapless human civilization can be attributed to (i) abuse of available sources of fresh water, (ii) wastage of water due to rapid urbanization and an improved quality of life, (iii) increased agricultural activities to feed an ever-growing population, depleting groundwater reserves, (iv) rapid industrialization, and (v) lack of coordinated policy implementations [1-3]. Adding to the woes, the current pandemic has challenged humanity like never before [4, 5]. This has posed a challenge of an entirely different nature, where water requirement for sanitization has increased manifold. The irreplaceable requirement of water in every sphere of life has made it imperative that to support an ever-increasing population, it is important to preserve, conserve, reuse and recycle the resource [6-9].

It is important to understand the technologies being employed to treat water in the current scenario. Water quality depends on the process it undergoes and therefore, depending on the constitutes of effluent stream, proper strategy can be framed and suitable process with minimum energy penalty can be designed [10]. The maturity of individual technology with its application potential and energetics involved must be considered before making a choice for a desired purpose [7, 11].

In this regard, the current volume is a collection of chapters belonging to mainly four categories of technologies: (i) Advanced Oxidation Processes (AOP), (ii) Nanoparticle-Based Treatment (NPT), (iii) Membrane-Based Treatment (MBT), and (iv) Emerging Technologies and Processes (EMT).

In Section I (comprising AOP technologies), a general overview is presented in Chapter 1, where fundamentals related to AOP are discussed along with global trends. Popular AOP technologies like Fenton process, photocatalysis, ozone, ultraviolet (UV) and H2O2 are discussed in detail. Chapter 1 ends with challenges posed in AOP technologies. Chapter 2 delves into a different genre of AOP, Hydrodynamic Cavitation (HC). This chapter discusses the mechanisms of ultrasound and HC processes and delves deep into integration of cavitation technologies with existing wastewater treatment technologies. The chapter also deals with integration of HC with adsorption and chemical oxidation processes and ends with future perspective of HC. Chapter 3 deals with a different aspect of HC, where, bubble dynamics, bubble collapse and thermodynamic effects of HC have been discussed. This gives an in-depth understanding of cavitation phenomena. The chapter also discusses various cavitating reactors and the toxicity effects of treatment process; it ends with future avenues. Chapter 4 (the last chapter in AOP) discusses fundamentals of ozonation technology. This chapter deals with various mass transfer models and mass transfer mechanism of ozone in water. The chapter handles the topic of ozone as a gas liquid contacting system and discusses the related mechanism as well as energetics associated. In the last part, the chapter deals with various sectors of application of ozone.

Section II of the book deals with NPT and in this regard, chapter 1 discusses application of Nanoparticles (NP) in fixed bed column filter system. This chapter discusses various target contaminants and the type of NP used to remove those contaminants. Then the chapter deals with design of fixed bed columns using the NP for removal of pollutants. Chapter 2 discusses the potential of NP-based water treatment processes. This chapter deals with various types of NPs employed to remove specific pollutant streams and the barriers posed in large-scale implementations.

Section III deals with membrane-based technology. In this regard, chapter 1 discusses microbial fuel cell (MFC) technology for wastewater treatment. This chapter discusses fundamentals related to working of an MFC and recent developments in anode and cathode material development. It also discusses development of membranes for MFC and challenges in MFC, and ends with case studies. Chapter 2 discusses the potential applications and challenges of ceramic membrane filtration. This chapter discusses the application of various ceramic membranes in industrial wastewater treatment as well as emerging contaminants. It also discusses the various configuration variants of ceramic membranes ultimately ending with pilot scale studies and challenges of ceramic membrane filtration units. Chapter 3 discusses an emerging area in the field of membrane separation-membrane distillation (MD). This chapter discusses the possibility of acidic wastewater treatment using MD. This chapter deals with the basics of the origin of acidic wastewater as well as various MD technologies employed in practice. This chapter also discusses various hybrid MD processes ultimately concluding with implications of MD in acidic wastewater treatment. The last chapter in this section (Chapter 4) discusses long-term assessment of vacuum membrane distillation (VMD) for textile wastewater treatment. This chapter covers the basics of transport mechanism and mass transfer involved in VMD and then discusses the influence of various operational parameters in textile wastewater treatment process in VMD.

The last section of the book is dedicated to few emerging processes in water treatment and recovery systems. Chapter 1 in this regard deals with application of zero valent iron to remove chromium and other heavy metals in metallurgical wastewater. This chapter deals with characterization of metallurgical wastewater in detail as well as preparation of zero valent iron. It then discusses in detail the batch experiments for treatment as well as detailed parametric investigations involved in treating the streams. The second chapter discusses removal of arsenic and fluoride using coagulation precipitation, ion exchange, and adsorption technologies. The chapter discusses detailed analysis of each genre of technology as well as its application and removal efficacies for arsenic and fluoride. The third chapter focuses on developing theoretical understanding of Zero Liquid Discharge (ZLD) process and its energy penalties. This chapter discusses in detail development of process flow sheet in Aspen and recovering maximum water from seawater feed using multistage flash coupled with evaporative crystallizer. This chapter discusses in detail development of the flow sheet and modeling of components along with energy analysis associated with a ZLD process for a feed whose salinity is equal to that of seawater. The fourth chapter focuses on a self-consistent approach in developing a water - energy - food nexus with an objective of highlighting the prospects and challenges in "conceptualization to technology transfer" for nutrient recovery from municipal wastewater for sustainable resource recovery and waste water management. Wastewater today is considered as a resource because of abundance of nutrients present in it. These nutrients like phosphorous and nitrogen if could be extracted economically, have the potential to solve multiple problems such as reutilization of natural resources and reduction in eutrophication in water bodies. In this regard the methods of extraction, based on the laws of thermodynamics shall be utilized for the same in order to maintain the crafted balance of water-energy-food nexus (WEFN). Throughout the chapter, nutrients, biomass, energy, and water are collectively termed as resources. The fifth and sixth chapter in this section highlights towards sustainable desalination. Desalination has largely been limited to affluent countries in the Middle East and has recently started making inroads in parts of the United States and Australia. In this regard, the initial efforts was to highlight the growing opportunities and scopes in the Indian subcontinent, while in the last chapter authors discussed on the least energy (work, heat, and fuel) required for desalination...