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Group 1-1aIDDE Complete
Actions Complete
Group 1-2IDDE Complete
Actions Not Complete
Group 1-3IDDE Not Complete
Actions Not Complete
Group 1-1bIDDE Complete
Actions CompleteNo Dry Flow
Group 1-1cIDDE Complete
Actions CompleteDry FIB Low
Dry Events (n=6) Wet Events (n=6) (n=3)
Mar
ker C
opie
s/10
0mL
ND
Dry Events (n=6) Wet Events (n=6)
engineers | scientists | innovators
What are DNA Markers and why are they Useful?Bacteria may originate from a variety of human and non-human fecal sources, as well as non-fecal sources. Conventional tools such as fecal indicator bacteria (e.g., E.Coli), basic chemical indicators (e.g., field test kits for ammonia, surfactants, and chlorine), dye testing, and closed-circuit television (CCTV), are often inadequate to distinguish human waste sources and properly inform management actions. Conventional tools can also be insufficiently sensitive to detect dilute quantities of sewage.
Therefore, the Commission sought advanced methods, including DNA markers, to test for these sources. Human DNA markers represent the most sensitive and specific tool for identifying human waste; they can detect sewage in a sample diluted up to one million times and can identify human waste when multiple other waste sources are present.
How was the Study Performed?This study used a hypothesis-driven approach to assess bacteria and nutrient sources to and within the Commission’s MS4. A total of 378 samples were collected from 35 outfalls located throughout Boston over a one-year period. Sampling locations represented a mixture of drainage areas, land usage, and IDDE program status – for example, IDDE investigations complete vs. not complete and IDDE corrective actions complete vs. not complete.
What are the Primary Recommended Next Steps?Based on these study results, pilot testing of modified procedures is recommended to locate remaining human waste sources in dry weather outfall discharges where conventional IDDE has been completed but elevated TMDL pollutants remain. These procedures include expanded use of E. coli and CCTV in network investigations, as well as the added use of fluorometers to detect dye and GIS analysis to locate areas having potential for sewer leaks to enter MS4s. Additional sampling is recommended within the MS4 network and on a broader set of outfalls to provide added confidence before moving forward with recommended procedures city-wide. The human DNA marker can be used during pilot testing to evaluate and document the effectiveness of the modified procedures..
Why are Results from this Study Important Regionally?To our knowledge, this is the first study to compare conventional IDDE parameters with state of the science DNA markers to determine their reliability for indicating human waste in a major urban MS4. The result is new data, specific to New England, on the reliability of field test kits and bacteria for indicating human waste, for dry and wet weather outfall screening and prioritization. The recommended modified IDDE procedures may allow New England agencies to more effectively find illicit discharges in the future, thus increasing IDDE program cost effectiveness and better protecting water quality.
Where can I Find More Information?For more information on the use of DNA markers for Microbial Source Tracking (MST):The California Microbial Source Identification Manual: A Tiered Approach to Identifying Fecal Pollution Sources to Beacheshttp://www.swrcb.ca.gov/water_issues/programs/beaches/cbi_projects/docs/sipp_manual.pdf For more information on designing a successful MST study that utilizes the toolbox approach:Pathogens in Urban Stormwater Systems – Developed for ASCEhttp://collaborate.ewrinstitute.org/ewri/ourlibrary/viewdocument?DocumentKey=fffe8a76-18b2-4f85-9b54-b0eac23f12a0 For a short video describing the benefits of a MST based strategy to address bacteria impacted waters by focusing on targeted control of high risk sources such as illicit sewage discharges, visit https://youtu.be/qDr95OAEHNY.
Project Partners and AcknowledgementsThis study involved collaboration and coordination amongst many project partners under the direction of the Boston Water and Sewer Commission.• Geosyntec Consultants led the project• CDW Consultants was responsible for all field data collection • The University of New Hampshire (UNH) Hubbard Center for Genome Studies performed the DNA community analysis with sampling coordinated by the UNH Stormwater Center. • All primary deliverables were reviewed by an expert panel of advisors consisting of Dr. Tom Ballestero from UNH, Dr. Robert Pitt from the University of Alabama, and Dr. Patricia Holden from the University of California at Santa Barbara. • Analytical laboratories included: Alpha Analytical, Northeast Environmental, Weck Laboratories, and Source Molecular.
Boston, Massachusetts Urban Water Quality Study
What was the Motivation for this Project?Over the past 30 years, the Boston Water and Sewer Commission (Commission) has made substantial progress on illicit discharge detection and elimination (IDDE) to address sewage inputs to their Municipal Separate Stormwater System (MS4). Since 1986, the Commission has eliminated over 1,700 illegal connections, removing more than 800,000 gallons of sewage per day from the MS4 and receiving waters. Previous outfall sampling indicated that in some drainage subcatchments, despite having removed illicit discharges or finding no illicit source, elevated concentrations of bacteria continued to be present.
For this study, Human DNA Markers were used to:• Explore the use and effectiveness of alternative methods to determine whether bacteria and phosphorus in collected outfall samples were due to human waste or non-human sources and
• Use findings to aid the Commission in prioritizing where (and how) future illicit discharge investigations may be directed.
Study results also demonstrate the benefit of enhanced sewage discharge abatement in terms of reducing bacteria and nutrient pollutant loads at their source, representing a lower unit cost approach for meeting TMDL requirements and restoring the condition of local impaired waters compared to wet weather control strategies, such as Green Infrastructure.
Findings demonstrate that sewage sources remain in most of the sampled sub-catchments and that continued IDDE investigation, including potentially using modified procedures (outlined below), should yield further water quality improvement.
What Were the Top Study Findings?The human DNA marker was detected at all outfalls sampled during dry weather regardless of IDDE program status (i.e., complete vs. incomplete), suggesting that human waste sources remain in the Commission’s MS4. This result demonstrates the increased ability of DNA markers to detect human waste compared to conventional methods.Human DNA marker concentrations were lower at outfalls sampled during wet weather than during dry weather, demonstrating that above-ground human waste sources (e.g., open defecation) that are washed off the land surface in wet weather may be less significant than below-ground sources (e.g., illicit sewer connections and leaks).
Human waste sources were a significant source of phosphorus and bacteria at MS4 outfalls during dry weather, therefore further removal of illicit discharges should yield considerable progress toward meeting Total Maximum Daily Load (TMDL) requirements.Bacteria (E. coli and Enterococcus) were correlated with the human marker for dry weather outfall samples thus supporting the continued utility of bacteria for MS4 outfall prioritization and screening during dry weather. For wet weather samples, the same conclusion could not be reached.
A subset of Pharmaceutical Personal Care Products (PPCPs) investigated in this study (acetaminophen, atenolol, and caffeine) were highly correlated with the human DNA marker in outfall samples taken during dry weather. While the correlations were strong, the cost of analyzing even a subset of PPCPs is similar to or higher than that of the human DNA marker. Therefore, PPCPs are not recommended for continued use as a primary indicator of human waste.
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The Boston Water and Sewer Commission recently performed an award-winning water quality study using advanced analytical tools, including human DNA markers, to determine whether bacteria and phosphorus in outfall samples were due to human waste or non-human sources.
Study Workflow
step 3DevelopSampling Plan
step 4CollectSamples
step 5AnalyzeData
step 1Formulate StudyQuestions
step 2Select SamplingLocations
Summary of Human DNA Marker concentrations at MS4 outfalls by IDDE program status, orange columns represent the median concentration of six samples and whiskers represent the range, ND = Not Detected. As indicated by the Salt Creek sample, marker concentrations in raw sewage are typically greater than > 10,000,000 copies/100 mL.
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