Advantages And Disadvantages Of Different Water Purification Technologies

1. Distillation
Distillation is probably the oldest method of water purification. Water is first heated to boiling. The water vapor rises to a condenser where cooling water lowers the temperature so the vapor is condensed, collected and stored. Most contaminants remain behind in the liquid phase vessel. However, organics with boiling points lower than 100 °C cannot be removed efficiently and can actually become concentrated in the product water. Another disadvantage is cost. Distillation requires large amounts of energy and water.

2. Ion-Exchange
The ion-exchange process percolates water through bead-like spherical resin materials (ion-exchange resins). Ions in the water are exchanged for other ions fixed to the beads. The two most common ion-exchange methods are softening and deionization.

Softening is used primarily as a pretreatment method to reduce water hardness prior to reverse osmosis (RO) processing. The softeners contain beads that exchange two sodium ions for every calcium or magnesium ion removed from the "softened" water.

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Water Recycling Technology Through Ion exchange

Introduction

The cost and maintenance associated with recycling metal bearing waste streams has decreased in recent years. This case history will press upon the technical and financial aspects of recycling metal bearing rinse waters. It is LT Technologies' belief, that by understanding the "theory" and environmental impact of water recycling, more companies will follow this path into the new millenium.

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Ion Exchange - An Overview

Ion exchange is a process used extensively in power generation and manufacturing facilities to control the purity and pH of water by removing undesirable ions and replacing them with acceptable ones. Specifically, it is the exchange of ions between a solid substance (called a resin) and an aqueous solution (reactor coolant or makeup water). Depending on the identity of the ions that a resin releases to the water, the process may result in purification of water or in control of the concentration of a particular ion in a solution. An ion exchange is the reversible exchange of ions between a liquid and a solid. This process is generally used to remove undesirable ions from a liquid and substitute acceptable ions from the solid (resin).

The devices in which ion exchange occurs are commonly called demineralizers. This name is derived from the term demineralize, which means the process whereby impurities present in the incoming fluid (water) are removed by exchanging impure ions with H+ and OH- ions, resulting in the formation of pure water. H+ and OH- are present on the sites of resin beads contained in the demineralizer tank or column.

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How do polymers work on hydroxide wastes

In order to understand how polymers improve separation of metal hydroxides, it is first necessary to define certain terms to ensure an understanding of their usage for comparative purposes.

A polymer can be either naturally occurring (starches, gums) or synthetic.  Its high molecular weight results form the large number of regularly repeating groups of atoms in its structure.  It can be either cationic, nonionic or anionic, depending of the charge of its organic functional groups.  Anionic flocculants are used in treating plating wastes because they are more active at the higher pH's where heavy metal precipitation occurs.  A polymer can function either as a coagulant or flocculant.

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