Using qPCR as a Rapid Detection Method for Determining Nitrification and Data Incorporation into a Nitrification Potential Index (NPI) in a South Texas Distribution System
Oral Presentation
Prepared by G. Ramirez, N. Gordon, W. Fernandez Lopez, I. Luna, R. Buck
City of Corpus Christi, 13101 Leopard, Corpus Christi, TX, 78410, United States
Contact Information: Gabrielr@cctexas.com; 361-826-1202
ABSTRACT
The City of Corpus Christ, TX like many other cities across the country faces the challenge of aging infrastructure in their vast underground network of distribution lines, this coupled with prolonged residence times present a particular challenge to monochloraminated systems which are susceptible to nitrification events. The Utilities Department at the City of Corpus Christi is using molecular biology to detect nitrifying organisms in their distribution system. The disinfectant chloramine can be broken down through nitrification. Nitrification is the two-step chemical oxidation of ammonia to nitrite, then from nitrite to nitrate. Nitrifying organisms, such as bacteria and archaea, are responsible for this oxidation. Testing for chemical parameters of nitrification, such as nitrite and nitrate, is common in determining a nitrifying event. Other surrogate parameters such as heterotrophic plate count and common fecal bacterial indicators also help to determine water quality. Being able to test for the actual nitrifying organisms is ideal for determining nitrification. To test for nitrifying organisms by culture can take a few weeks as they are slow growers. Using molecular biology to test for the DNA from these organisms is a rapid method and can detect a nitrification event before water quality can degrade. After filtering 20 liters of distribution water samples through a 0.22 um filter, DNA is extracted from the filter. Afterwards, qPCR is performed using primers and probes specialized for the City of Corpus Christi distribution system. A microbial community analysis study was performed and resulted in optimized primers and probes. The data from the PCR is used in conjunction with surrogate chemical parameters, as well as the Total Coliform Rule program, to get a more complete overview of water quality. A Nitrification Potential Index (NPI) was developed using the chemical and physical parameters believed to be present during nitrification events. The NPI applies the daily Water Quality data, including the PCR data, collected from dedicated sampling sites to test for a potential nitrification event. The enhanced biological assessment of nitrifiers in the distribution system, as well as a statistical index that incorporates all of the biological and chemical data, gives the City of Corpus Christi critical tools in an early detection of a nitrification event.
Oral Presentation
Prepared by G. Ramirez, N. Gordon, W. Fernandez Lopez, I. Luna, R. Buck
City of Corpus Christi, 13101 Leopard, Corpus Christi, TX, 78410, United States
Contact Information: Gabrielr@cctexas.com; 361-826-1202
ABSTRACT
The City of Corpus Christ, TX like many other cities across the country faces the challenge of aging infrastructure in their vast underground network of distribution lines, this coupled with prolonged residence times present a particular challenge to monochloraminated systems which are susceptible to nitrification events. The Utilities Department at the City of Corpus Christi is using molecular biology to detect nitrifying organisms in their distribution system. The disinfectant chloramine can be broken down through nitrification. Nitrification is the two-step chemical oxidation of ammonia to nitrite, then from nitrite to nitrate. Nitrifying organisms, such as bacteria and archaea, are responsible for this oxidation. Testing for chemical parameters of nitrification, such as nitrite and nitrate, is common in determining a nitrifying event. Other surrogate parameters such as heterotrophic plate count and common fecal bacterial indicators also help to determine water quality. Being able to test for the actual nitrifying organisms is ideal for determining nitrification. To test for nitrifying organisms by culture can take a few weeks as they are slow growers. Using molecular biology to test for the DNA from these organisms is a rapid method and can detect a nitrification event before water quality can degrade. After filtering 20 liters of distribution water samples through a 0.22 um filter, DNA is extracted from the filter. Afterwards, qPCR is performed using primers and probes specialized for the City of Corpus Christi distribution system. A microbial community analysis study was performed and resulted in optimized primers and probes. The data from the PCR is used in conjunction with surrogate chemical parameters, as well as the Total Coliform Rule program, to get a more complete overview of water quality. A Nitrification Potential Index (NPI) was developed using the chemical and physical parameters believed to be present during nitrification events. The NPI applies the daily Water Quality data, including the PCR data, collected from dedicated sampling sites to test for a potential nitrification event. The enhanced biological assessment of nitrifiers in the distribution system, as well as a statistical index that incorporates all of the biological and chemical data, gives the City of Corpus Christi critical tools in an early detection of a nitrification event.
