How to remove Selenium from Wastewater?
Soils and groundwater in some parts of the world are now facing the emergence of a third major issue, selenium (Se) contamination, following major pollution by nitrates and pesticides.
Selenium occurrence in ecosystems occurs naturally as a result of weathering of Se-containing rocks, and is exacerbated further by human activities. Selenium is abundant in the environment, and the two most common sources of ‘Se’ exposure in humans are food and water. Because of its antioxidant, anti-inflammatory, and chemo preventive properties, Se, a metalloid, is an important micronutrient.
Elemental selenium is an essential nutrient in living beings at very low concentrations (micrograms per liter), but at high concentrations it poses a serious risk to health and the environment. Because some industrial processes can result in selenium concentrations in their wastewater exceeding permissible levels, the discharge of selenium to the environment is regulated by each country's competent environmental authorities.
The following are the current available technologies that have proven to be highly effective in removing heavy metals in general, and selenium in particular, from industrial wastewater:
· Reverse Osmosis
· Activated carbon adsorption
· The exchange of ions
· Co-precipitation and chemical precipitation
· Biological therapy (MBBR, etc.)
· Other high-complexity, high-cost processes.
Among these technologies, Reverse Osmosis, Ion-exchange and MBBR are the most commonly used for heavy metal removal in general.
Water treatment goals and wastewater characteristics
Because of the characteristics of their processes, many industries discharge wastewater containing extremely high concentrations of heavy metals. Selenium is sometimes the dominant metal.
For example, wastewater from the mining industry has been found to contain extremely high levels of selenium, ranging from 0.03 to 2 mg Se/L. When the wastewater has an average concentration of more than 2 mg/L selenium, this is considered an alarmingly high concentration.
It has been discovered that industrial wastewater contains up to 80 mg/L of selenium, with the content being highly fluctuating and difficult to predict. In these cases, the reagent dosage must be adjusted on a continuous basis to eliminate the selenium present in the water or wastewater.
Estimation of dosages and retention times
It can be difficult to determine an optimal dosage for wastewater with a high fluctuation in selenium content. It is calculated as an estimation of the dosage of iron chloride based on historical data and experience by a correlation of iron concentration - selenium elimination, and the treatment and control systems are designed based on these empirical and experienced data.
What can Netsol Water offer?
Netsol Water offers a comprehensive range of water treatment technologies (Reverse Osmosis and much more) and services to meet the demands of a variety of industries, and our skilled staff can make suggestions on the best solution. This might be as simple as optimizing current equipment and methods to achieve the desired performance or including a new phase into the treatment process.