Advanced Water Treatment

Electrochemical Methods

Mika Sillanpää, Mika Sillanpaa, Mika Silanpää, Mika Sillanpää

• Publisher: Elsevier
• Year: 2020
• Print ISBN:
  9780128192276
• eBook ISBN:
  9780128192283
• Topic: Technology & Engineering
• Subtopic: Microbiology
• Index: Technology & Engineering

Advanced Water Treatment: Electrochemical Methods reviews the current state-of-the-art in the electrochemical-based methods for water treatment, the effectiveness of the electrochemical oxidation technique in inactivating different primary biofilm forming paper mill bacteria, as well as sulfide and organic material in pulp and paper mill wastewater in laboratory-scale batch experiments. Various electrodes are described, including boron-doped diamond, mixed metal oxide, PbO2, and their impacts on inactivation efficiency of parameters, such as current density and initial pH or chloride concentration of synthetic paper machine water.The mechanisms of action of various electrodes in different systems are reported. The book is a source of information for environmental and chemical engineers due to the number of methods and industry-focused application cases and researchers who study the transition from a laboratory environment to practical applications. - Includes the most recent research on advanced water treatment by electrochemical methods - Describes the use of electrochemical cleaning of paper mill wastewaters - Includes techniques for cleaning mining waters and removal of organic pollutants by electrochemical methods

Chapter 1

Electrocoagulation in the treatment of industrial waters and wastewaters

Mikko Vepsäläinen ¹ , and Mika Sillanpää ^{2 1} Mineral Resources, CSIRO, Clayton, VIC, Australia ² Department of Civil and Environmental Engineering, Florida International University, Miami, FL, United States

Abstract

Chemical coagulation is commonly used in raw water and wastewater treatment plants for the destabilization of pollutants so that they can be removed in the subsequent separation processes. The most commonly used coagulation chemicals are aluminum and iron metal salts. Electrocoagulation (EC) technology has also been proposed for the treatment of raw waters and wastewaters. With this technology, metal cations are produced on the electrodes via electrolysis, and these cations form various hydroxides in the water depending on the water pH. In addition to this main reaction, several side reactions, such as hydrogen bubble formation and the reduction of metals on cathodes, also take place in the cell. In this research, the applications of EC were investigated in raw water treatment and wastewater applications.

The surface water used in this research contained high concentrations of natural organic matter (NOM). The effect of the main parameters—current density, initial pH, electric charge per volume, temperature and electrolysis cell construction—on NOM removal was investigated. In the wastewater treatment studies, the removal of malodorous sulfides and toxic compounds from the wastewaters and debarking effluents were studied. In addition, the main parameters of the treatment, such as initial pH and current density, were investigated. Aluminum electrodes were selected for the raw water treatment, whereas wastewaters and debarking effluent were treated with iron electrodes.

According to results of this study, aluminum is more suitable electrode material for EC applications because it produces Al(III) species. Metal ions and hydroxides produced by iron electrodes are less effective in the destabilization of pollutants because iron electrodes produce more soluble and less charged Fe(II) species. However, Fe(II) can be effective in some special applications, such as sulfide removal. The resulting metal concentration is the main parameter affecting destabilization of pollutants. Current density, treatment time, temperature, and electrolysis cell construction affect the dissolution of electrodes and hence also the removal of pollutants. However, it seems that these parameters have minimal significance in the destabilization of the pollutants besides this effect (in the studied range of parameters). Initial pH and final pH have an effect on the dissolution of electrodes, but they also define what aluminum or iron species are formed in the solution and have an effect on the ζ-potential of all charged species in the solution. According to the results of this study, destabilization mechanisms of pollutants by EC and chemical coagulation are similar.

Optimum dissolved organic carbon removal and low residual aluminum can be obtained simultaneously with EC, which may be a significant benefit of EC in surface water treatment compared with chemical coagulation. Surface water treatment with EC can produce high quality water, which could be used as potable water or freshwater for industrial applications. In wastewater treatment applications, EC can be used to precipitate malodorous sulfides to prevent their release into air. Technology seems to be able to remove some toxic pollutants from wastewater and could be used as pretreatment before treatment at a biological wastewater treatment plant. However, a thorough economic and ecological comparison of chemical coagulation and EC is recommended, because these methods seem to be similar in pollutant destabilization mechanisms, metal consumption, and removal efficiency in most applications.

Keywords

Electrocoagulation; Wastewater treatment; Water treatment

1. List of Publications
2. Abbreviations
3. 1. Introduction
   1. 1.1 Basic concepts and theory of coagulation and flocculation with hydrolyzing metal salts
      1. 1.1.1 Interface of colloidal particles
      2. 1.1.2 Stability of colloids in aqueous solutions
      3. 1.1.3 Destabilization mechanisms of colloids
      4. 1.1.4 Commonly used metal salt coagulants
      5. 1.1.5 Applications of metal salt coagulants in industrial raw water and wastewater treatment
   2. 1.2 Theory of electrocoagulation
      1. 1.2.1 Main reactions
      2. 1.2.2 Side reactions
      3. 1.2.3 Properties of the sludge
      4. 1.2.4 Treatment parameters
      5. 1.2.5 Comparison of electrocoagulation and chemical coagulation
      6. 1.3 Practical considerations of electrocoagulation
      7. 1.3.1 Constructions of electrocoagulation systems
      8. 1.3.2 Applications of electrocoagulation
      9. 1.3.3 Combinations of electrocoagulation and other water treatment technologies
      10. 1.3.4 Economical and ecological considerations
4. 2. Objectives and Structure of the Work
   1. 2.1 Surface water treatme...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Chapter 1. Electrocoagulation in the treatment of industrial waters and wastewaters
• Chapter 2. Ultrasound-assisted electrochemical treatment of wastewaters containing organic pollutants by using novel Ti/Ta2O5–SnO2 electrodes
• Chapter 3. Sewage sludge electro-dewatering
• Chapter 4. Ultrasonic and electrokinetic remediation of low permeability soil contaminated with persistent organic pollutants
• Chapter 5. Electrooxidation treatment of pulp and paper mill circulating waters and wastewaters
• Index