In this article we will present the best methods to remove chloride from water or wastewater, both for domestic and industrial applications.
Even though chloride is naturally occurring in waterways, high concentrations can have negative consequences on human health.
Knowing the most efficient technology for removing chloride is especially important for production managers in factories that require high purity water or that must abide by governmental liquid discharge regulations.
What Is Chloride
Chloride is a naturally occurring element that is common in most natural waters and is most often found as a component of salt (sodium chloride) or in some cases in combination with potassium or calcium.
The presence of chloride in groundwater can result from a number of sources including the weathering of soils, salt-bearing geological formations, deposition of salt spray, salt used for road de-icing, contributions from sewages and wastewaters.
Instead, in industrial effluents chlorides can reach higher levels and these wastewaters must be treated before discharge. Chloride in wastewater can be effectively removed by various technologies.
Is Chloride the Same as Chlorine?
Chlorine and chloride are related elements with a similar chemical structure. Both elements have 17 protons and 18 electrons. However, the chloride ion has one more electron than chlorine, which makes it more electronegative. This difference makes chloride more stable compared to chlorine.
Chlorine is a powerful disinfectant that kills bacteria and viruses. It is used to disinfect water, both on a large scale and in small-scale applications. It works by disrupting the cell walls of bacteria. It also damages their proteins and enzymes, which makes them useless for the organism. However, chlorine is not good for human health, and repeated exposure to high levels can cause health problems.
On the other hand, Chloride, is not harmful to human consumption under certain levels, but it can cause serious corrosion problems to plumbing and equipment.
High Chloride Levels in Water Main Problems
High Chloride levels in water or wastewater can cause many problems:
High levels in humans can cause dehydration, kidney disease, metabolic acidosis;
Increased chloride concentration can cause salinization, which has become a serious and widespread environmental problem nowadays;
Plumbing corrosion: the wearing of pipes, pumps, hot water heaters, and fixtures by chloride;
Irreparable damages to industrial equipment;
For these reasons, removing chloride from waters is a necessity in many industries, especially for drinking water production.
What Are the Treatment Options for Chloride Removal from Water?
The most effective water and wastewater treatment methods for reducing their chloride content are Reverse Osmosis, Electrodialysis, and distillation systems.
In the following paragraphs we will present the advantages and disadvantages of each treatment methods for chloride removal from water.
1. Reverse Osmosis (RO) for Chloride Removal Treatment
Reverse Osmosis treatment removes chloride in water by pushing it through a membrane with very tiny pores. The membrane stops many contaminants, including chloride, while allowing water to pass through.
Advantages
Reverse Osmosis removes between 95 and 99 percent of the chloride in water or wastewater, mostly depending on the equipment configuration and feed water source.
Disadvantages
If chlorides levels are too high, the membranes could be easily damaged, and the efficiency of the equipment can drop drastically without proper maintenance. For this reason, a pre-treatment system is often required at the beginning of the treatment process.
2. Electrodialysis (ED) for Chloride Reduction and Removal
Electrodialysis (ED) is a very effective method for Chloride removal from water.
This technology uses a membrane stack built on the filter press principle. The stack consists of 200â400 alternate cationic and anionic membranes between two electrodes; the aqueous feed solution flows through the cells between each pair of membranes.
This technology can greatly reduce Chloride levels in waters and produce high purity diluate.
Advantages
Electrodialysis can remove up to 99% of the chloride in water or wastewater. Also, the equipment requires little to no maintenance compared to other systems.
Disadvantages
A pre-treatment system is often required at the beginning of the treatment process because calcium and silica can damage the membrane stack. If the membrane is damaged the treatment effect is greatly weakened and the stack replacement can be very costly.
3. Evaporation and Distillation for Chloride Removal from Water and Wastewater
Evaporation and distillation are processes that produce distillate water and concentrate from any water or wastewater source by removing contaminants, such as Chloride.
In the evaporations process the steam rises and leaves contaminants, such as Chloride behind. With proper operation, distillation machinery can remove nearly 100 percent of chloride in water or wastewater.
Advantages
From evaporation and distillation processes a highly pure distillate can be obtained from water with almost 100% of the chloride removed from the feed water. Furthermore, evaporators requires less maintenance than membrane systems and the treatment results are very stable for zero liquid discharge systems.
Disadvantages
The cost of industrial evaporators can be high for small companies and the energy consumption is higher than other technologies for the removal of chlorides from waters.
Some examples of evaporators and crystallizers are shown in the pictures above. Such equipment can remove almost 100% of the chloride content in water and wastewater.
Also, thanks to the new MVR evaporators, such as EVADEST, energy consumption can be reduced by 70% compared to traditional evaporators.
How to Design a Chloride Removal System
The first step to design a chloride removal treatment system is to run a complete laboratory analysis of the water and assess the precise levels of chlorides in water or wastewater.
Once the analysis is ready, we can choose and configure the best equipment for your application, whether itâs a household drinking water or industrial application.
Our most common approach is to install a pre-treatment system and then, depending on the project requirements, manufacture the treatment equipment.
For more information about our treatment systems for chloride removal and reduction kindly get in touch at:
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