Electrolysis – A Green Technology for Water Treatment
Water and Waste-Water Treatment Projects – GES
For more than one hundred years Chlorine disinfection has served as the method of choice for disinfecting drinking water around the world.
The conventional methods which have been used extensively include chlorine gas disinfection and chlorine solutions – "hypochlorite". The advantage of these methods is in the vast amount of experience gained over the years. However there are some serious disadvantages including: the cost of the material, especially in liquid chlorine (hypochlorite) facilities, the large investment required for protection and safety equipment in chlorine gas facilities, and the cost of material. Recent years have seen a rise in the importance of "green" technologies for protecting the environment and for decreasing the use of various chemicals.
GES – Global Environmental Solutions, which deals with water and waste-water treatment, acquired the Argad company in May, 2006. GES continues to expand Argad IL in this field with full cooperation and close supervision of Prof. Dor Yitzhak, Process Supervisor.
The DC electrolytic treatment method in this system is based on electrolytic separation of water. In the electrolysis process, a DC current passes through the electrolytic medium. Electrical voltage from the DC power source is run between two electrodes, one being the cathode (minus), and the other being the anode (plus). As a result of the electrical current passing between the electrodes, the electrolytic medium of water, with the various dissolved salts, separate into their constituent components in accordance with the electrochemical reactions taking place on the electrode surfaces.
There are two types of disinfection processes occurring on the surface of the anode:
- Anode oxidation reactions, which are a whole series of reactions resulting in the formation of gases and free radicals with a high oxidation potential. These products disinfect the water.
- Acid catalysis reactions, which emit dissolved CO2, while lowering alkalinity which can be expressed as transient hardness.
Reduction processes occur on the cathode surface, along with alkaline pH sediments. Removal of lime scale in the facility occurs mainly as a result of these alkaline pH sediments processes taking place around the cathode. As a result, the cathode is coated with lime scale and precipitants with a low solubility product in an alkaline environment.
Removal and ejection of the lime scale is carried out by way of timed polarity reversals.
Advantages of Electrolysis Technology:
- Prevention of lime scale accumulation in the various water systems.
- Annihilation of microbiological life forms and prevention of biophiles due to the presence of disinfectant agents in the water.
- Operation in an alkaline environment (pH greater than 8), which eliminates the need for anti-corrosive inhibitors.
- Water free of foreign chemicals.
- Continuous and automatic removal of suspended solids from the water.
- Compact and modular device.
- Treatment of cooling tower water.
Testing the Electrolytic System with "Mekorot"
As part of the technological feasibility testing, we began running a B-Site for electrolytic chlorination and disinfection of drinking water, in-situ in Well No. 14 in Yad Mordechai. Continuous observations were held for a period of six months, with the close cooperation of the Mekorot team. We examined residual chlorine levels at various capacities, electrical output and engineering efficiency. Below are the main findings and conclusions from the running period:
- Process feasibility was proven for electrolytic chlorination and disinfection in-situ for drinking water, keeping in line with standard requirements.
- At an average capacity of 55 m3/h, an average residual chlorine level of 0.33 ppm at an electrical output of 2.3kw.
- The turbidity of water treated using the electrolytic chlorinator decreased to a value of 0.20 NTU as opposed to 0.30 NTU for the feed water.
- Chlorination using an electrolytic device such as the Yad Mordechai B-Site eliminates the need for boosting pumps in drill sites using chlorine gas feeds.
- In wells where capacity is a modular product of the Yad Mordechai B-Site, it is possible to reduce chlorination costs by optimizing the ratio of the electricity source and the electrolytic reactors.
- A "green" process was used for the chlorination and disinfection of drinking water which eliminated the risks existing in the current processes which use gaseous chlorination or hypochlorite.
|
