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 www.biocharnow.com.

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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).