Due to natural and human factors, toxic and carcinogenic metalloarsenic exists in our environment. The biggest hazard comes from dissolved arsenic in drinking water. Therefore, effective "arsenic filters" are crucial for safe drinking water supply.
In the early 1990s, new research showed that arsenic not only has acute toxicity, but also has carcinogenic effects even at very low concentrations, which is harmful to the human body. Therefore, the amount of arsenic in drinking water is reduced to 10 µ g/l. At that time, there was no simple technological solution for small and medium-sized water plants to reliably remove arsenic to meet the new requirements. Therefore, BK sorb adsorption particles emerged in the early 1990s. Arsenic typically dissolves in water in the form of AsV or AsIII, which is why traditional filtration materials reach their limits. The following processes are typically applicable for arsenic removal:
Adsorption arsenic removal
To adsorb arsenic onto the surface of a solid adsorbent. Before the development of iron-based adsorbents, granular alumina ("activated alumina") was mainly used for arsenic removal. Due to its low capacity and the danger of dissolving aluminum, it no longer plays a role in actual arsenic removal. Iron hydroxide based adsorbent represents a new technology for arsenic removal in drinking water production. The biggest advantage is that the adsorption filter is easy and safe to operate, and can remove arsenic below the detection limit. In addition, there will be no wastewater or contaminated sludge generated during operation. The use of granular iron hydroxide for arsenic removal has selectivity, so the natural composition of water remains unchanged. During this process, both AsV and As (III) will be removed.
Advantages:
Single device configuration structure and simple operation
Due to the high selectivity of arsenic, the capacity is very large
High equipment availability and low maintenance requirements
Established technology has been used in over 2000 locations worldwide
Easy to remove, no need to treat sludge
Disadvantages:
The residence time depends on the water quality
Adsorbents need to be replaced regularly
Removing arsenic through flocculation/filtration
The flocculation process for arsenic removal usually uses iron or aluminum salts. These salts precipitate in the raw water and are filtered. Dissolved arsenic will bind to the surface of the filterable floc, thereby being removed from the raw water. According to the arsenic concentration, a specific dosage of flocculant is required to remove arsenic. The dosage must be determined through regular analysis. The filtered sludge must be further processed according to applicable local regulations and ultimately disposed of as residue or hazardous waste based on arsenic content. Due to its high technical complexity, this process is particularly suitable for large-scale wastewater treatment plants.
Advantages:
Standard drinking water treatment process
Can simultaneously remove several turbid impurities
The chemical cost is relatively low
Disadvantages:
The arsenic removal effect depends on the dosage of flocculant added
Need to handle and dispose of arsenic containing sludge
High input costs
Factory technology is complex; We need skilled talents
Not suitable for small factories
Removing arsenic using an ion exchanger
Depending on the material, ion exchangers can remove anions or cations from raw water while releasing other ions with the same charge into the water. As long as arsenic exists in the form of As (III) in water, it carries a charge and can be removed by ion exchangers in principle; However, the removal of As (III) is impossible. However, the ion exchanger has low selectivity for As (III), resulting in relatively low practical efficiency. Therefore, in order to achieve its actual service life, it must be regenerated. This will generate toxic regeneration solution that requires further treatment. This means that ion exchangers are almost ineffective in the actual arsenic removal process.
Advantages:
Can simultaneously remove different ions
Ion exchangers can usually be regenerated
Frequently exhibiting high reaction kinetics
Disadvantages:
Low selectivity for arsenic and high interference from other ions such as sulfates
As (III) cannot be removed
Removing low capacity leads to frequent regeneration cycles
Regeneration requires the use of chemicals and generates arsenic containing solutions that require subsequent processing
High material cost
Membrane method for arsenic removal
Membrane technology utilizes high pressure to remove pollutants from water through size exclusion and membrane material interaction. The small pore size of nanofiltration or reverse osmosis membranes is necessary for reliable removal of arsenic. During this process, arsenic is intercepted along with other water pollutants that cannot pass through the membrane and discharged into the wastewater stream. During this process, the raw water is partially desalinated. The high arsenic wastewater stream is subsequently further treated. Non selective arsenic removal not only changes the arsenic content, but also alters the composition of other components in water, which may be beneficial or harmful depending on the water usage.
Advantages:
Established water treatment technology
Non selective process; Remove other pollutants together
Modular design, easy to expand
Disadvantages:
Non selective; Remove all compounds from water and remove mineral water
Usually requires pre-processing
Concentrated solution requires further processing
High energy consumption demand
Wide range of technology, high investment cost
Personnel who have undergone specialized training are required to operate the equipment