Assessing Biochar for the Removal of Nitrate and Disinfection Byproducts

The Issue

The Truckee Meadows Water Authority (TMWA), not unlike other water agencies, is challenged with the formation of disinfection byproducts within the distribution system.  Chlorine, a commonly used disinfectant, is added to maintain disinfection in the distribution system and when chlorine begins to breakdown, over time, these DBP’s can develop. TMWA is seeking to embark on a groundwater recharge program but the State of Nevada requires the removal of chlorine before recharging water into the groundwater system as to avoid any adverse impacts from the formation of DBPs. Rising nitrate levels in communities relying on wells also pose significant treatment challenges across rural communities in the U.S. Nitrate, in fact, is one of the contaminants most frequently found to be in violation of health-based standards in the U.S.(1)

A wide variety of water treatment processes have been developed to assist in DBP and nitrate management in drinking water.  TMWA currently utilizes granular activated carbon (GAC) to remove the chlorine. GAC, however, does have some limitations such as its low capability to remove dissolved organic nitrogen and its inability to remove bromides, which may become precursors for other DBPs. In the same way, a variety of water treatment processes have been developed to assist the management of nitrate in drinking water, including ion exchange, reverse osmosis, and adsorption.  Nevertheless, all these technologies have limitations which has led to the need for ongoing research in the development of novel materials with enhanced capabilities and economic feasibility for a wide range of applications.

The Solution

Biochar is a cost-effective, environmentally friendly material for water treatment.  It is a highly porous, carbon-based material produced from various biomass feedstocks (usually vegetal or animal wastes) under low oxygen conditions. Of its many features, biochar has been reported to have a large specific surface area and contains a wide variety of surface functional groups, thereby capturing the attention of the scientific community as a multifunctional adsorbent with multiple environmental, agricultural, and energy related applications(2,3). The biggest challenge of biochar is the ability to manipulate its surface characteristics to ensure the selective removal of preferred contaminants, such as DBPs and nitrate.

The Pilot

WaterStart, in partnership with TWMA, funded Dr. Erick Bandala at the Desert Research Institute to assess the capability of engineered biochar to remove DPB precursors, total dissolved carbon, and nitrate along the drinking water treatment process that will ultimately provide a novel technology in support of drinking water management at the household and centralized water utility levels.  Biochar materials were acquired from Biochar Now.  Biochar Now is a Colorado-based company formed in 2011.  They have developed and patented a production technology that creates a very high-quality biochar from dead trees and waste wood.

The Results

Results from batch adsorption experiments showed that activated biochar was the best material for nitrate adsorption and a close second for natural organic matter adsorption, which was used as a proxy for DBP precursors, and outperformed activated carbon.  In the same way, activated biochar was capable of adsorbing a significant amount of DBP precursors, even though the best material for DBP precursor adsorption was the untreated biochar. Continuous flow experiments showed a reasonable performance of activated biochar for nitrate and DBP precursor adsorption, with nitrate being the limiting step in the adsorption process.

Further Development

Because of the promising results of biochar in removing DBPs and nitrate, further testing has been proposed to evaluate its effectiveness in removing poly- and perfluoroalkyl substances (PFASs) and total organic carbon.

About Biochar Now

Biochar Now is a Colorado-based company formed in 2011.  They have developed and patented a production technology that creates a very high-quality biochar from dead trees and waste wood. This material has proven effective in specialty agriculture applications, as soil amendments, for odor control,  algea removal, and in the oil and gas industry. Learn more at


  1. Schaider, L. A., Swetschinski, L., Campbell, C. & Rudel, R. A. Environmental justice and drinking water quality: Are there socioeconomic disparities in nitrate levels in U.S. drinking water? Heal. A Glob. Access Sci. Source 18, 1–15 (2019).
  2. Inyang M.I., Gao B. Yao Y., Xue Y., Zimmerman A., Mosa A., Pullammanappallil P., Ok Y.S., C. X. A review of biochar as low cost adsorbent for aqueous heavy metal removal. Rev. Environ. Sci. Technol. Sci. Technol. 46, 406–433 (2016).
  3. Tan X., Liu Y., Zeng G., Wang X., Hu X., Gu Y., Y. Z. Application of biochar for the removal of pollutants from aqueous solutions. Chemosphere 125, 70–85 (2015).



The Issue at SNWA

Ozone is a really effective oxidant to meet disinfection or contaminant removal goals. Cryptosporidium is a parasite that has caused outbreaks in places such as Las Vegas and Milwaukee, and in the past, many ozone systems were installed at drinking water treatment plants to address that issue. Ozone is much more effective against Cryptosporidium compared to other disinfectants such as chlorine. Ozone is also effective at reducing the formation of other disinfection byproducts, particularly those that form during chlorination.

The problem is that ozone also reacts with bromide in water to form bromate. This is a really common problem in drinking water utilities that implement ozonation. Bromate is a regulated disinfection byproduct of ozonation, a chemical water treatment technique based on the infusion of ozone into water. Any utility that has bromide in their source water will likely have some concern about bromate production, which is regulated and needs to be monitored by the treatment plant to ensure it stays below its maximum contaminant level of 10 g/L. Typical ways to control bromate formation include maintaining low ozone exposures, at the expense of reduced disinfection efficacy, or using other chemical control strategies. Regardless of the approach, rapid bromate detection and quantification would ensure compliance with the regulation and efficacy of any bromate control strategy.

SNWA was looking for a solution that could rapidly detect how much bromate might be formed in its full scale ozone process. Standard methods are effective but require off-line analysis and are sometimes complicated by interfering constituents.

The Solution

SNWA became aware of the Metawater technology back in 2015 through an International Ozone Association (IOA) conference discussion Eric Wert, Project Manager for Applied Water Quality Research at SNWA, had about online bromate monitoring. The Metawater technology is an online analyzer, making it different than other offline methods traditionally being used. There are currently no online analyzers for bromate available on the market, which made Metawater, a Japan based company, a pretty innovative technology and approach that continued to gain the interest of SNWA. “So, we decided to bring it to WaterStart,” said Wert.

Metawater has had some success with its bromate analyzer at several treatment plants in Japan. Although it’s been successful in Japan, there were no tests performed in the US until this pilot with SNWA.

Utilities typically use offline methods with ion chromatography to monitor for bromate. The Metawater sensor uses a similar approach but in an online configuration and with fluorescence-based detection. If successful, a plant could monitor for bromate on an approximately hourly basis, which is the big benefit of this type of technology.

The Pilot

After SNWA pitched it to WaterStart, they opted to move forward with developing an agreement between SNWA, UNLV and Metawater to conduct testing of the technology’s ability to monitor bromate levels in treated water from Lake Mead. Metawater in return sent an older bromate sensor to UNLV for a controlled bench-scale evaluation and a newer prototype to SNWA for a two-year evaluation in an actual treatment setting. The overall goal of the project was to optimize the Metawater technology to improve its accuracy and precision in the challenging Colorado River water matrix. The technology’s prior success in Japan had primarily been on source waters with lower mineral and organic matter content.

One of the issues with bromate analysis in general, with offline and online technologies, is the presence of interfering constituents within the water. For example, some ions are present at orders of magnitude higher concentrations than bromate and can interfere with ion chromatography. Particularly with fluorescence-based detection, which is the case for the Metawater technology, bulk organic matter can also create a high background signal. This was the primary concern for the Metawater sensor, since it was determined to be less robust than standard offline methods at handling potential interference.

The idea of this pilot project was to determine how the operation of the sensor could be modified for challenging water matrices, possibly with pretreatment steps targeting interfering constituents. Potential solutions were identified, integrated into the sensors, and then tested to compare their performance and potential for full-scale implementation in southern Nevada.

Pilot Results

At the conclusion of the pilot, UNLV and SNWA concluded that the pretreatment strategies tested during the project showed promise but still required further optimization to ensure reliable operation in an actual drinking water application. The analyzer showed great promise as an online sensor for high purity applications, such as in the bottled water industry or even in drinking water systems with lower background interference. For example, systems relying on relatively pure snowmelt with an overall quality similar to the previously tested Japanese source waters (e.g., San Francisco and Reno) might be ideal settings for Metawater?s current technology. However, the existing and modified sensors were not sufficiently robust for monitoring bromate in Colorado River water in southern Nevada.

Further Development

SNWA had a final meeting with Metawater and explained that they would be open to collaboration in the future if different applications popped up, “because there are applications where the Metawater technology might be effective, such as with water sources that have less interference than the Colorado River,” said Daniel Gerrity, Associate Professor at UNLV and now Principal Research Laboratory Scientist at SNWA. Metawater has taken the sensor back to Japan and are working to improve the technology on their end based on some of UNLV and SNWA’s findings from the pilot.

This WaterStart project not only helped address the Metawater sensor, but according to Daniel Gerrity of SNWA, “it also led to other collaborations between Metawater, SNWA, UNLV, and other research partners. So, we were able to expand the original collaboration beyond the original bromate problem.”

About Metawater

Metawater is a prominent Japanese company that offers optimum solutions in water resource management through machine and electric engineering. Their efforts in the U.S. are currently being developed to prolong the life of or modify water treatment and recycling facilities. They aim to promote technological development that contributes to a safe, stable and reliable water environment.