The process of making nitrates in a chemical wastewater treatment plant is based on the decomposition of organic waste by anaerobic bacteria. Traditionally, nitrate reactors are designed to use slow flow rates over appropriate media and cultivate anaerobic bacteria. This process requires the daily feeding of a soluble carbon source based on the nitrate level. However, this process is not always reliable as it can experience "de-cycling", or the buildup of organic matter. Also, the addition of soluble carbon constantly lowers the ph of the waste, which is undesirable.

The most common method of nitrate removal is to increase the activity of anaerobic bacteria, which are beneficial for the environment. These organisms are known as "biomass" and use nitrates to convert them into less dangerous nitrates. While aerobic bacteria break down trash using oxygen, anaerobic bacteria are only effective in an oxygen-deprived environment. As a result, the bacteria residing in the nitrate reactor eliminate the nitrates produced by the trash and return them to the water.

The nitrate filter was originally designed as a simple, effective way to remove nitrates from wastewater. However, it required up to 10-12 weeks to remove the nitrates. There have been many refinements in this technology. Most newer nitrate reactors are alcohol-fed and operate with a peristaltic pump. These units sit in a cabinet and are easily operated.