Innovative Technologies For Nitrate Treatment

High nitrates in drinking water present health issues for infants as well as adults with compromised systems. However, the emergence of difficult-to-treat contaminants in groundwater has increasingly driven municipal water utilities to revisit wells with elevated nitrate levels that were previously taken offline. Sources that cause increased nitrate levels can include excess fertilizer runoff, septic systems leaching, and runoff from feed lots with manure storage. 

While it is possible to prevent some contamination, once nitrate gets into the source water it must be mitigated. Understanding the existing levels in the source water and the desired treatment level allows those equipment providers to select the most suitable treatment approach and technology.

The traditional approach to nitrate treatment has relied upon blending with other low-level water sources, isolating the well, or using conventional treatment equipment. The use of conventional treatment technologies, primarily ion exchange or reverse osmosis, has presented several challenges to the design and siting of facilities, including:

• Wastewater discharge volumes
• Brine usage and discharge to sanitary sewers
• Wastewater plant acceptance of discharge streams

While ion exchange and reverse osmosis for nitrate removal have been available for decades, there are several advancements that may eliminate or minimize the issues associated with the installation of a nitrate treatment system.

Examining The Technologies

Innovative technologies in drinking water have led to more sustainable approaches for the reduction of nitrate. These include biological filters, high-recovery reverse osmosis (RO) systems that can boost recovery rates above 90 percent, and ultra-low-waste ion exchange that produces a waste stream under 0.5 percent.

Biological Nitrate Treatment

Biological treatment has been around for decades in wastewater facilities to address multiple contaminants, specifically for the removal of nitrate, iron, and manganese. Many wastewater facilities are reluctant to accept wastewater streams that have concentrated levels of nitrate and brine that will impact their treatment processes. That’s because the brine and nitrate slugs that are discharged by conventional ion exchange systems may result in higher operating costs and there are concerns about brine compatibility with the facility construction materials. When a water source is treated biologically, the brine and nitrate slugs are eliminated, so the discharge is more acceptable to the wastewater treatment plants. The solids that are present in this waste stream are benign, neutral wastes that are similar in characteristics to the solids normally processed by these facilities.

Now, similar biological filters that transform nitrate into harmless nitrogen gas and a benign wastewater stream are being applied to drinking water treatment. The town of Taylorville, IL, for instance, recently installed and began operating a biottta biological nitrate treatment system to mitigate the increasing levels that had been impacting its raw water source.

Advanced RO

High-recovery RO systems are another relative newcomer to the water treatment industry, with the ability to increase recovery rates to 90 percent and greater, as compared to traditional RO systems that hover at about 75 percent. This significant increase in recovery levels allows for a substantial yield from the source while consistently rejecting 99 percent of the nitrate and other dissolved solids. When considering the design of a treatment facility, high-recovery RO systems are an excellent choice for removing nitrates as well as a variety of other contaminants.

Ultra-Low-Waste Ion Exchange

The most traditional approach to nitrate treatment has been the use of ion exchange whereby the nitrate in the water is exchanged for chloride from the ion exchange resin bed. When the resin bed has accumulated as much nitrate as it can hold, a breakpoint is reached where nitrate will begin to leak into the effluent stream. The resin bed is considered exhausted at this point and requires regeneration with a diluted brine stream (NaCl). The main drawback is the volume of waste produced that must be discharged to a sanitary sewer or hauled offsite.

By comparison, ultra-low-waste ion exchange technologies have been able to reduce the waste volume produced during regeneration by up to 90 percent. The additional benefit with this system design is the lower nitrate leakage levels, which makes it suitable for blending operations.

The treatment professionals at AdEdge Technologies can assist in the technology selection process to ensure that nitrate treatment is both an optimal and sustainable approach for municipalities.