Use of AFM from Arsenic removal from ground water –
Arsenic is often found in borehole / tube wells and ground water at varying concentrations depending upon the geology of the ground. In India western states along with certain locations in the south have fairly high contamination of Arsenic in the ground water. IN certain cases Arsenic is also found in the waste water effluent of certain industries.
1. Oxidation reactions to convert metals from soluble ionic form to insoluble oxidized precipitate, pH correction and redox correction.
2. Decantation may be required if the concentrations are above 5 mg/l, if not proceed to AFM® filtration.
3. AFM® filtration to remove the suspended metal oxide solids, there will also be adsorption reactions and surface oxidation reactions.
Oxidation: This is achieved through aeration of the water. The water is aerated for a period of no less than 60 minutes. If water flow is 50 m3/hr the aeration level is 100m3/hr of air and tank volume is 50m3 of water. Aeration also helps in removing the several dissolved gases from water and making the water to behave in a manner favourable for mechanical adsorption on AFM.
pH: The pH of the water should be increased to a value over pH 7.5
Redox: The aeration system should increase the redox potential of the water. It is important to raise the potential to as high a value as possible. Certainly it should be over 200mv.
- Arsenic oxidation also benefits from the addition of ferric to the water. Arsenic is removed by oxidation and co-precipitation with ferric, example 0.1 mg/l As requires up to 1 mg/l of ferric (as ferric chloride)
Pretreatment of the water prior to filtration by AFM® is very important. AFM® will remove the metals and metalloid by the following mechanisms;
- Oxidation and adsorption (similar to greensands and ferric media)
- Adsorption of sub-micron metal oxide particles
- Physical filtration of most particles down to 1 micron.
Arsenic removal by AFM is one of the recommended technology by the Department of science and technology. Several projects are in operation currently in the state of west Bengal for the removal of Arsenic from the ground water.
Other AFM Application Areas
AFM® reduces the biological risk from bacteria and parasites as well as the chemical risk from water and air just above the surface. The result is a safer pool for children, a healthier work place for staff in public pools and a greatly improved swimming experience for everyone. Read More…
SWRO – Sea water reverse osmosis has found a great importance today as a technology for the reclamation of brackish water or sea water and making it potable enough for human consumption or industrial applications. Read More…
UF, RO membranes & DM plant resins work best when they are new and clean. Fouling of the membranes by inorganic and organic contaminants as well as biofouling are some of the main issues effecting the performance and cost of running water treatment systems.Read More…
Iron and manganese are often found in borehole / tube wells and ground water at varying concentrations depending upon the geology of the ground. Read More…
Chromium is occasionally found in ground water in trace amount from 1 to 10 ug/l however the occurrence of chromium is usually associated with pollution from industries such a leather tanning, wood preservation and textiles. Polluted ground water may have much higher concentrations. Read More…