Groundwater supplies almost half of all drinking water in the world, with high economic value and social significance.1 Nitrate (NO3) is one of the most widespread water pollutants on earth, and levels of nitrate in groundwater sources are continuing to rise, making nitrate removal in groundwater a significant concern. While it can occur naturally in groundwater, nitrate levels can rise to unsafe concentrations as a result of fertilizer runoff, industrial activities, and wastewater discharge.
High levels of nitrate can cause methemoglobinemia ("blue baby syndrome") by competing with oxygen for binding with hemoglobin, effectively starving the body's cells of oxygen.2 This risk is of particular significance for infants, pregnant mothers, and the elderly.
Moreover, nitrate and its sister compound, nitrite (NO2), can form nitrosamines, a known factor in causing birth defects, non-Hodgkin's lymphoma, bladder and ovarian cancer, thyroid hypertrophy, and digestive tract cancers.3,4Therefore, it is important to mitigate the impact of nitrate pollution in groundwater.
Nitrate pollution impacts both industrialized and developing countries. Widespread contamination is seen across agricultural regions in the U.S., particularly in the Midwest (Figure 1 below)5.
Additional areas of concentrated nitrate pollution are found near farming communities in the Pacific Northwest, the Northeast, and Central/Southern California. In fact, studies by the EPA indicate that 3,000 wells and 10% of the groundwater in California are impacted by nitrate.
Globally, dependence on nitrate-contaminated drinking water impacts millions of people. While the World Health Organization (WHO) has set a guideline of 50 mg/L as NO3 (11 mg/L as N) for drinking water limits, communities such as the states of Andhra Pradesh and Rajasthan in India are experiencing nitrate levels as high as 1,600 mg/L.6 Thousands of drinking water wells have been shut down even in the face of severe drought and water scarcity, including hundreds of wells in California alone.
The Challenge with Nitrate Removal: Every Conventional Technology Produces Waste
Nitrate is highly mobile in groundwater and does not adsorb, volatilize, or naturally degrade in most groundwater aquifers. Often, nitrate in groundwater is not treated, but rather blended with uncontaminated water from another source, if one is available.
While this may seem attractive because of the potentially low initial capital outlay, it can become costly where uncontaminated water must be externally purchased and transported for local blending. The risk profile is also high with this strategy by leaving municipalities wholly reliant on a third party and leaving them exposed to potential cost increases or to the loss of a critical water source.
Alternatively, the treatment of nitrate-contaminated water can be achieved through two different approaches: (1) separation of nitrate from the water or (2) degradation of nitrate into harmless nitrogen gas. The first approach (nitrate separation) is typically accomplished using ion exchange or reverse osmosis. These methods can be energy-intensive and produce concentrated waste streams that require subsequent treatment.
The second approach (nitrate degradation) uses an ancient and natural process where nitrate is reduced to nitrogen gas, which is safely released into the atmosphere. This is an attractive alternative to nitrate separation since the nitrates are converted to an inert and harmless form that does not require further treatment or handling.
However, the biological technologies currently available for nitrate degradation are associated with significant drawbacks including: (1) long start-up times and long recovery times after system upsets; (2) the production of biological solids requiring costly treatment and disposal; and (3) low organism densities necessitating large footprints to achieve sufficient treatment capacity.
Microvi MNETM: A New Paradigm for Nitrate Degradation
For the past several years, Microvi – a global greentech pioneer based in the San Francisco Bay area – has been working on a new approach to overcome the challenges of treating nitrate and other water pollutants. This new approach is called the MicroNiche Engineering™ (MNE) platform, where novel materials science is used to harness and utilize natural organism populations in a way that has never been possible before.
As a result of MNE, the Microvi MNE™ process was born, using natural degraders to degrade nitrate into harmless nitrogen gas in a matter of 5-20 minutes. It does not produce sludge or secondary waste, thus overcoming the disadvantages of biological processes.
Microvi MNE represents a paradigm shift from conventional nitrate degradation. In conventional fixed-film or suspended growth processes, non-specific organisms are repeatedly grown and removed as sludge. In these conventional biological treatment systems, any attempt to artificially favor a particular species of organism requires complex and delicate control systems that can be notoriously unreliable and limits process flexibility.
On the other hand, Microvi MNE uses specially-targeted, high performance natural microorganisms that are completely incorporated at very high density within Microvi MNE polymeric composites, called biocatalysts. The natural, nitrate-degrading organisms are irreversibly retained within the biocatalysts and never leave the reactor, as they are protected from washout, overgrowth, toxicity, and abrupt changes in operation.
WesTech Engineering and Microvi entered into an exclusive alliance in 2017 to begin offering the Microvi MNE technology for nitrate removal in drinking water for the North American market. This alliance takes advantage of WesTech’s more than 40 years of successful experience in water and wastewater.
Contact us for more information about the feasibility of Microvi’s nitrate removal solution for new or existing drinking water installations.
Successful Installations of the Microvi Technology
A key motivation behind the Microvi MNE technology was to meet the urgent need of communities around the world who require a simple, effective, and waste-free solution for treatment of high nitrates. The first installation of this new technology took place in Aboriginal communities in Western Australia in 2012. The installation continues to remove nitrate from groundwater with the original biocatalysts.
Furthermore, after five years, the biocatalyst shows no signs of deterioration in performance or integrity. In this case, with such a remote site, no conventional technology had been simple enough to be effective.
In 2017, the first full-scale installation of the Microvi MNE technology began operation at the Sunny Slope Water Company in Pasadena, California. In the preceding years, the Microvi MNE technology was evaluated according to strict standards and protocols set by the California Division of Drinking Water (DDW).
This thorough evaluation required that a number of parameters be monitored such as dissolved oxygen, nitrate, turbidity, total coliform, and specific microbiological tests. During this evaluation, steady state nitrate removal was achieved in a short period of time (e.g. days), as opposed to the weeks often required for conventional biological technologies (Figure 2 below). The short start-up period was an indicator of the high biocatalytic activity available for nitrate degradation from the first day of operation.
Important Advantages of the Microvi MNE Technology
This new nitrate removal system is extraordinarily efficient. Since there is no sludge production, less water is lost or needs costly recovery processing. It is also flexible, and the system can be retrofitted into existing tanks or installed in simple, low cost systems. The start-up and recovery time is quick, providing a good solution for both continuous and intermittent use.
Using Microvi’s nitrate removal technology saves costs, compared to a traditional nitrate removal system. The Microvi MNE technology needs less energy and chemicals and requires no reactor backwashing. Economic analysis performed by a third-party engineering firm found that the Microvi MNE nitrate removal system offers cost savings of approximately 35% over the system’s lifetime, as compared to ion exchange solutions.
For the plant designer and owner, elimination of the need to find, secure, and then maintain a disposal route for the undesirable concentrated waste is highly significant. Plant owners can be assured that they are not reliant on a third party to accept their waste, and therefore, they have total control on their long-term commercial and operating costs.
For the plant operator, this new process is easier and faster than traditional solutions. With treatment rates of just minutes, the dense biomass metabolizes nitrate more efficiently, requiring smaller tanks. Short treatment times help reduce the plant’s footprint and allows for modular/standard systems. The simple reactor has minimal internal components, straightforward control, and no complex backwashing.
With the simpler operation, the system is more reliable and requires less operation time. When the biocatalysts are subjected to upset conditions or dramatic variations in influent quality, their performance is nearly unchanged.
For conscientious customers, this technology provides safe drinking water at affordable cost using a sustainable technology which protects their most precious of possessions.
The Microvi MNE technology has been permitted to run at full capacity to provide clean drinking water for 30,000 households in the Pasadena area. As one of the first full-scale biological technology to be implemented in the United States for this purpose, Microvi MNE has gathered significant interest as a step-change technology for the water industry.
With its easy operation, simple maintenance, and low energy needs, Microvi’s nitrate removal technology is providing a new paradigm for the way water managers approach nitrate treatment. From installations in Australia and California, demonstrations in Arizona and Alabama, and overwhelming interest from water companies and municipalities, this new technology is poised to dramatically impact the quality of drinking water around the world.
Fatemeh Shirazi is the CEO and CTO of Microvi, a global greentech company based in the San Francisco Bay Area. An internationally recognized pioneer in the development of bioconversion processes, Dr. Shirazi is the inventor of the MicroNiche Engineering platform with dozens of patents granted and pending. Dr. Shirazi has led Microvi since 2008 and was awarded the prestigious Jack Edward McKee Medal recognizing achievement in groundwater protection, restoration, and sustainable use. She holds a B.S. in Chemical Engineering and an M.S and Ph.D. with Honors in Civil and Environmental Engineering.
Figure 1: Red areas showest highest nitrate pollution impact due to aquifer vulnerability and high nitrogen inputs.
Figure 2: Nitrate removal performance by the Microvi MNE technology at Sunny Slope Water Company (Pasadena, CA)
1. WWAP (United Nations World Water Assessment Programme). 2015. The United Nations World Water Development Report 2015. Water for a Sustainable World – Facts and Figures. Perugia, Italy, UNESCO.
2. Fewtrell, L., 2004. Drinking-water nitrate, methemoglobinemia, and global burden of disease: a discussion. Environmental Health Perspectives, 112(14), p.1371.
3. Ward, M.H., Mark, S.D., Cantor, K.P., Weisenburger, D.D., Correa-Villasenor, A. and Zahm, S.H., 1996. Drinking water nitrate and the risk of non-Hodgkin's lymphoma. Epidemiology, 7(5), pp.465-471.
4. Wolff, I.A. and Wasserman, A.E., 1972. Nitrates, nitrites, and nitrosamines. Science, 177(4043), pp.15-19.
5. Noland, B., Ruddy, B., Hitt, K., & Helsel, D. 1998. A National Look at Nitrate Contamination of Ground Water. Water Cond. and Purif., 39(12), 76–79. Retrieved from http://water.usgs.gov/nawqa/nutrients/pubs/wcp_v39_no12/
6. Rai, S.N., 2003. Ground Water Pollution in India: An Overview. In Ground Water Pollution: Proceedings of the International Conference on Water and Environment (WE-2003), December 15-18, 2003, Bhopal, India (Vol. 3, p. 419). Allied Publishers.