ABSTRACT/SYNOPSIS
Water is one of the most important and treasured natural resources supporting the diverse array of life on earth. Rapid depletion of fresh potable water reserves, contamination of existing sources, and generation of large amounts of wastewater due to anthropogenic activities have forced scientists worldwide to find alternate sources of potable water and to develop technologies for the treatment of seawater for drinking purposes. Many countries including the UAE have limited natural water resources and most of the population does not have easy access to clean drinking water. The UAE uses thermal desalination as the dominant technology to make seawater potable. Today, most of the country’s potable water (42 percent of the total water requirement) comes from some 70 major desalination plants, which account for around 14 percent of the world’s total production of desalinated water. Membrane Technology employing high pressure for removing high concentrations of salts and other contaminants from seawater is currently gaining momentum worldwide. This episode provides an overview of one of the most used membrane technologies – Nanofiltration and the different aspects associated with nanofiltration used for the removal of pathogens. It is the first part of a two-part series titled “Nanofiltration Membrane Technology” by Sani Water. Sani Water has been at the forefront of providing their customers with the latest products and advanced water treatment technologies available in the drinking water industry. With “Nanofiltration Membrane Technology Series”, Sani Water aims to educate and inform their customers about the fundamentals and applications of nanofiltration membrane technology and the use of nanofiltration technology as pretreatment for desalination plants.
MEMBRANE TECHNOLOGY AND NANOFILTRATION TREATMENT PROCESS
Nanofiltration (NF) membrane technique is water treatment technology to remove organic matter, color, odor, taste, residual quantities of disinfectants, and trace herbicides from large water bodies. Increasingly stringent regulations have caused membrane processes to rapidly gain acceptance as a cost-effective method for water and wastewater treatment. Membrane technology is an established part of several water treatment processes. A membrane is a permeable or semipermeable, solid-phase (polymer, inorganic or metal), which controls the relative rates of transport of certain species present in the source waters and restricts their motion. Generally, membranes work by selectively allowing some constituents to pass through the membrane while blocking the passage of others. For this to happen, the movement of material across a membrane requires a driving force. Therefore, membrane processes can normally be classified based on the type of driving force that causes components in the water to separate. The different type of driving force that initiates solute separation includes a pressure differential (micro-, ultra-, nano-filtration and reverse osmosis); a concentration difference across the membrane which initiates diffusion of a species between two solutions (dialysis); and a potential field applied to an ion-exchange membrane that initiates migration of ions through the membrane (electrodialysis, electro-electrodialysis, and electrochemical devices).
REFLECTION POINTS
NANOFILTRATION USES
The primary goal of NF membranes is to use it for water softening, desalinate brackish waters, and reduce disinfection by-product (DBP) precursors. Other objectives including advanced treatment for water reuse, NOM, the rejection of pharmaceutically active compounds (PhACs), hormones and pesticides, and specific contaminant removal including arsenic, fluoride, nitrate, nitrite, selenium, and radionuclides. NF can reject 80 – 95% of divalent ions such as Ca+2 and Mg+2. The study showed that NF can effectively reject cephalexin, tetracycline, acetaminophen, indomethacin and amoxicillin from water. Some of the key contaminants removed by NF are:
- A nanofiltration filter has a pore size of approximately 0.001 micron (pore size ranges vary by filter from 0.008 micron to 0.01 micron; Molecular Weight Cut Off (MWCO) of 200 to 2000 Daltons); Nanofiltration filters remove particles based on size, weight, and charge.
- Nanofiltration has an extremely high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia).
- Nanofiltration has an extremely high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli).
- Nanofiltration has an extremely high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus).
- Nanofiltration has a moderate effectiveness in removing chemicals.
REFERENCES
- https://www.cdc.gov/healthywater/drinking/home-water-treatment/household_water_treatment.html
- http://wcponline.com/2009/02/10/membrane-technology-break-water-treatment/
- Singh, R., Bhadouria, R., Singh, P., Kumar, A., Pandey, S., & Singh, V. K. (2020). Nanofiltration technology for removal of pathogens present in drinking water. In Waterborne Pathogens (pp. 463-489). Butterworth-Heinemann.
- Ahsan, A., & Imteaz, M. (2019). Nanofiltration membrane technology providing quality drinking water. In Nanotechnology in Water and Wastewater Treatment (pp. 291-295). Elsevier.
- Shahmansouri, A., & Bellona, C. (2015). Nanofiltration technology in water treatment and reuse: applications and costs. Water Science and Technology, 71(3), 309-319.
- Zazouli, M. A., & Bazrafshan, E. (2015). Applications, issues and futures of nanofiltration for drinking water treatment. Health Scope, 4(3).
