Grantee Research Project Results
2011 Progress Report: Rapid Detection of Sewer Pipeline Problems Using Bacterial DNA Markers and Q-PCR Technology
EPA Grant Number: R834871Title: Rapid Detection of Sewer Pipeline Problems Using Bacterial DNA Markers and Q-PCR Technology
Investigators: Yan, Tao
Institution: University of Hawaii at Manoa
EPA Project Officer: Page, Angela
Project Period: February 1, 2011 through January 31, 2016
Project Period Covered by this Report: February 1, 2011 through January 31,2012
Project Amount: $299,956
RFA: Advancing Public Health Protection through Water Infrastructure Sustainability (2009) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
- Quantify Acidithiobacillus species to assess concrete sewer crown corrosion conditions
- Quantify wastewater lipase genes to identify FOG (Fat, Oil and Grease) deposition hotspots in sewer pipelines
Progress Summary:
The project was officially awarded on February 7, 2011, and the first task of the project involved the recruitment of a postdoctoral researcher. This project startup phase was successfully completed by August 2011 when the postdoctoral researcher arrived at the institution. Since August 2011, several research activities for Objective 1 have been initiated. The first objective was split into three tasks: (1) develop different levels of corrosion in different experimental modules, (2) analyze bacterial communities on corroded pipes to confirm the presence of Acidithiobacillus, and (3) develop Q-PCR methods using Acidithiobacillus DNA markers.
Reactors were designed and built to allow corrosion of concrete coupons thereby allowing assessment of the corrosion process over time. The reactors consisted of an air-tight glass mason jar with a concrete coupon attached to the underside of the lid. The coupons were exposed to three different concentrations of H2S (50, 200 and 550 ppm) by including an internal H2S generator. Each H2S concentration was done in triplicate. Artificial waste water filled the space around the generator and was inoculated with sewage organisms (obtained from a wastewater sample from Sand Island, Honolulu). An abiotic control was set up, which exposed coupons to H2S, but no microorganisms were added. Finally, a negative control was also set up, containing the coupons, but no H2S or microorganisms. The reactors were placed in a waterbath two degrees above room temperature (25°C) to allow condensation to occur on the coupons. A diagram of the experimental set-up is shown:
After 5 months, the pH of the coupons dropped from pH 12 to around pH 10, so we are confident that the first stage of corrosion has occurred. The negative control coupon remains at pH 12. However, 1 month ago, fresh inocula taken from a corroded sewer pipe in Moana Park, Honolulu was added to help speed the corrosion process since it was highly likely that this contained Acidithiobacillus sp.
Recent assessment of the pH of the artificial wastewater showed that a lot of the H2S was being oxidized in the wastewater, resulting in pHs as low as 1.65. The wastewater has now been removed and will instead be used as inocula added to the coupons each week. This is a long-term project, but we are confident that Objective 1.1 of the project has been completed.
In addition to this long-term project, we have addressed Objective 1.2 by sampling corroded concrete sewer pipes in Hawaii (Kamehameha Highway and Moana Park, Honolulu). Environmental conditions such as H2S, O2, CO and LEL were measured at each site. Corroded pipe samples and wastewater were assessed in the lab (pH and sulfide levels). Total community DNA was extracted from the corroded sewer pipe samples. We are now in the process of selecting further sampling sites containing corroded to heavily corroded concrete sewer pipes to analysed by deep-sequencing of the 16S rRNA gene. This will increase the understanding of how corrosion severity correlates with the presence of different bacterial groups (i.e., hetertrophs vs. neutrophilic sulfur oxidizers vs. acidophilic sulfur oxidizers) and confirm that Acidithiobacillus are the climax community for crown corrosion. Objective 1.2 will therefore be completed in the near future.
Future Activities:
The major objectives for the next reporting period are:
- Focus on analyzing the pyrosequencing data to publish immediately in a high impact journal
- Develop Q-PCR methods to quantify Acidithiobacillus in the reactors
- Construct a lab-scale sewer system for the assessment of FOG deposition
Journal Articles:
No journal articles submitted with this report: View all 7 publications for this projectSupplemental Keywords:
Sustainability, sewer pipelines, bacterial DNA markers, Q-PCR technology, public health protectionProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.