No products in the cart.
Why is Arsenic Removal from Wastewater important?
Arsenic is a metalloid that exists in the environment both naturally and because of human activities such as mining, smelting, combustion of fossil fuels and others. Arsenic is notorious for its toxic effect on human health and is classified as a carcinogen. Most of this notoriety has been received due to the presence of high concentrations of Arsenic in groundwater in countries such as Bangladesh and India, as well as some Latin American countries such as Mexico, Chile, and Argentina. Due to the lack of adequate treatment, Arsenic poisoning has contributed to the deaths of thousands of people in recent times.
Arsenic removal from freshwater (so that it is safe for human consumption) is of critical importance, but the removal of Arsenic from wastewater is also crucial. Many wastewater streams (both municipal and industrial) contain high levels of Arsenic. If not treated adequately, this toxic substance will be released into the environment, finding its way back into our precious water sources and destroying natural ecosystems.
What are the methods to remove arsenic from wastewater?
Many conventional methods exist for the removal of Arsenic from water that can also be applied to wastewater. However, the removal of Arsenic from wastewater is most effective after primary and secondary treatment. This is due to several factors such as:
- Wastewater treatment processes must remove many contaminants, not just Arsenic.
- Wastewater, particularly municipal, contains high levels of Phosphorus and organic matter which inhibits the removal of Arsenic.
- High doses of coagulants are required to remove Arsenic, especially during primary treatment, making it impractical and uneconomical.
Conventional primary and secondary treatment processes such as flocculation/coagulation, settling, oxidation, ion-exchange techniques, biological treatment etc. all reduce Arsenic concentrations to varying levels. However, to reduce Arsenic concentrations in the final effluent to a level where it is safe for discharge to the environment, more advanced techniques are required.
Advanced methods for arsenic removal
Advanced filtration methods such as micro/nano filtration, reverse osmosis etc., are effective at reducing Arsenic concentrations to required regulatory levels. However, these processes are renowned for their high capital and operating costs as well as concentrated toxic waste streams (brine).
Another treatment method that has been gaining popularity recently is adsorption. Adsorption is not a new method for the treatment of water/wastewater, but recent developments have made it an attractive option for Arsenic removal.
What is Adsorption in arsenic removal?
Adsorption simply works by attracting target molecules (e.g., Arsenic) in a liquid to the surface of a solid (and in some cases, liquid) substance. Adsorption is widely used in drinking water treatment, tertiary wastewater treatment, and other applications. The effectiveness of the adsorption method will depend primarily on the nature and concentration of the contaminant, choice of suitable adsorbent material, and other factors such as pH and temperature.
Adsorbents such as ferric oxide, haematite, activated carbon, activated alumina, natural substances such as clay and silica, organic polymers etc., are all effective at removing Arsenic to varying levels. Adsorption is an attractive option due to its relatively low cost compared to advanced filtration. Some adsorbents such as activated carbon can be regenerated and reused in situ.
The type of adsorbent used for Arsenic removal not only depends on inlet and (required) outlet concentrations but the form of Arsenic present as well. In addition, upstream processes which determine pH, temperature, and presence of other contaminants (which may affect Arsenic removal efficiency), must also be considered. Finally, attention must be given to the safe disposal of spent adsorbents and potential opportunities for recycling.
Conclusion – Why arsenic removal is an important consideration
Arsenic removal is a pressing issue for not only drinking water but wastewater as well. To protect our environment from the discharge of wastewater containing high levels of Arsenic, adequate treatment must be carried out to reduce Arsenic concentrations to specified regulatory levels.
Various treatment options exist for the effective removal of Arsenic in wastewater. Careful consideration must be given to several factors including the nature and load of Arsenic present, the presence of other contaminants that may inhibit Arsenic removal, the cost of treatment, and, of course, the disposal of solid waste.
For more details on storage and tanks as involved in the process to remove arsenic from wastewater including conical process tanks, sludge tanks and dosing tanks for storage of untreated and treated water, please get in touch.