IJERPH, Vol. 17, Pages 772: Chloramine Disinfection-Induced Nitrification Activities and Their Potential Public Health Risk Indications within Deposits of a Drinking Water Supply System (International Journal of Environmental Research and Public Health)

Microsensors were applied to study the diffusion reaction and activity of a nitrogen species of deposit sediment from a drinking water supply system. Microprofiles of dissolved oxygen (DO), NH4+-N, NO3−-N, and NO2—N in the sediment indicated that the DO concentration decreased from the highest at the sediment surface to zero at the bottom of the sediment. Similarly, with the increase of depth, NH4+-N initially increased rapidly and then decreased slowly, while the concentration of NO3--N reached a maximum at around 6000 μm and then decreased to about 0.1 mg·L–1 near the bottom of the sediment. Almost no change was observed for NO2−-N. The decrease of NH4+-N and DO corresponded well with the increase of NO3−-N. Furthermore, based on a consumption and production rate analysis, DO has always been consumed; the NH4+-N consumption rate increased rapidly within 0–1000 μm, reaching about 14 mg·L−1·S−1·10−9. A small amount of NH4+-N was produced in 2000–6000 μm, which could be attributed to denitrification activity. There was no change deeper than 6000 μm, while NO3−-N was produced at a depth between 0 and 6000 μm and was consumed in the deeper zone. At the depth of 9000 μm, the NO3−-N consumption reached a maximum of 5 mg·L−1·S−1·10−9. The consumption of DO and NH4+-N, which corresponded with the production of NO3−-N in a specific microscale range within the sediment, demonstrated nitrification and denitrification activities. In addition, the time required for the diffusion of only DO, NH4+-N, NO3−-N, and NO2−-N was estimated as 14 days; however, in the practical, even after 60 days of operation, there was still a continuous reaction, which provided further evidence towards microbial activities within the sediment.