You are here:
ENGINEERING DESIGN CONFIGURATIONS FOR BIOLOGICAL AMMONIA REMOVAL
Citation:
Lytle, D., C. White, AND D. Williams. ENGINEERING DESIGN CONFIGURATIONS FOR BIOLOGICAL AMMONIA REMOVAL. Presented at 2013 AWWA Biological Treatement Symposium, Denver, CO, March 28 - 29, 2013.
Impact/Purpose:
The use of biologically active filtration to oxidize ammonia as a full-scale drinking water treatment process has not been thoroughly considered in the United States. A number of concerns with biological water treatment exist including the potential release of excessive numbers of bacteria into finished waters, sensitivity of bacteria to changes in water chemistry and operating conditions, and a lack of long term documentation of the effectiveness, design and operation of biological water treatment processes. As a result, the objective of this presentation will be to demonstrate the effectiveness of a biological water treatment to remove ammonia and iron from three Midwest community water supplies. The study will also identify operating parameters necessary to meet the desired goal of complete ammonia and iron removal, and the present operating recommendations.
Description:
Many regions in the United States have excessive levels of nutrients including ammonia in their source waters. For example, farming and agricultural sources of ammonia in the Midwest contribute to relatively high levels of ammonia in many ground waters. Although ammonia in water does not pose a direct health concern, if it enters the drinking water distribution system, nitrification of significant levels of excessive ammonia may. Nitrification refers to the oxidation of ammonia to nitrite and then nitrate by bacteria in the presence of oxygen. When nitrification occurs uncontrollably in the distribution system, the biological stability of distribution system is disrupted, which can cause a number of water quality problems including taste and odor complaints, inability to maintain disinfectant residual, and corrosion of distribution system material. Excessive nitrification can also lead to elevated nitrite and nitrate levels which are regulated by the EPA at levels of 1 and 10 mg N/L, respectively. Because the MCLs apply at the entry point into the distribution system rather than within the distribution system, monitoring of nitrite and nitrate are normally not conducted at the consumer’s tap and therefore would likely be missed if elevated as a result of nitrification of ammonia by biofilm in the distribution system. Clearly, the complete oxidation of excess source water ammonia to nitrate during the treatment process (provided ammonia is below 10 mg N/L) reduces the potential negative impact (nitrification) on distribution system water quality. While physicochemical methods for ammonia removal are possible, such as ion exchange, biological methods appear to be more efficient and cost-effective. The use of biologically active filtration to oxidize ammonia as a full-scale drinking water treatment process has not been thoroughly considered in the United States. A number of concerns with biological water treatment exist including the potential release of excessive numbers of bacteria into finished waters, sensitivity of bacteria to changes in water chemistry and operating conditions, and a lack of long term documentation of the effectiveness, design and operation of biological water treatment processes. As a result, the objective of this presentation will be to demonstrate the effectiveness of a biological water treatment to remove ammonia and iron from three Midwest community water supplies. The study will also identify operating parameters necessary to meet the desired goal of complete ammonia and iron removal, and the present operating recommendations. Specifically the presentation will use a combination of data from completed full- and pilot-scale studies to demonstrate the effectiveness of three biological ammonia reduction treatment configurations. Specifically, a traditional filtration approach, “contactor” approach and “aeration-contactor” approach will be discussed. A discussion regarding the conditions appropriate for each configuration will be presented. Relationships between ammonia reduction, media size, and hydraulic loading rate will be illustrated. The impact of temperature, backwashing with chlorinated water, oxygen concentration, TOC and other factors on nitrification in biological treatment systems will be presented. Lastly a discussion regarding the nature of associated biofilm will be made.
URLs/Downloads:
http://www.awwa.org/portals/0/files/education/presenter/biological%20trmt%20tech%20program%20-final.pdf