- Determining the Effectiveness of On-site Septic Systems foe the Removal of Viruses
Pursuant to Governor Charlie Baker’s executive order #562, Massachusetts Department of Environmental Protection (DEP) convened a stakeholder group to review public comments made regarding changes to Title 5 of the State Environmental Code. One of the comments recommended that DEP consider reduction of groundwater separation (separation between the bottom of a leach field and groundwater) in certain situations
As part of that effort, DEP teamed up with MASSTC to conduct a study to assess pathogen removal in soil absorption systems (leach fields).
The objective of the study is to evaluate pathogen removal at varying depths in the infiltrative surface beneath a wastewater dispersal unit.
Pathogen transport is a primary concern of public health regulators nationwide for the obvious concern regarding disease transmission from both ingestion and indirect exposure though recreational and other activities. When Title 5 (310 CMR 15.00) was reviewed in the early 1990’s, MassDEP looked at the World Health Organization’s recommended 5 log removal (99.999%) of pathogens and reviewed available literature on pathogen removal (reviewed in the 1991 Technical Evaluation of Title 5 by DeFeo, Wait & Associates, Inc.) in order to determine the degree of removal that occurs at varying depths to groundwater for onsite systems. The 1995 revisions to Title 5 supported the longstanding requirement of a minimum of 4 feet of separation to provide a high pathogen removal factor in order to protect public health and groundwater as a drinking water source. The 1995 revisions further required a 5-foot separation for more porous soils. DEP used 4 log removal, or 99.99%, as the basis for the 4-foot separation requirement.
The study will look at five indicator organisms:
- Escherichia coli
- Fecal (Thermotolerant) coliforms
- MS-2 male-specific coliphage
- Somatic coliphage
Fore more about this project, please explore the sections below:
More About this Project
Indicator organisms are those that are used to detect and measure fecal contamination.
35 test cells were constructed to asses pathogen removal rates across a variety of depths of sand and two different wastewater distribution methods.
To support the scale of this project, MASSTC received funding from Massachusetts DEP to procure and outfit an on-site laboratory facility capable of conducting the analyses required for the Groundwater Separation Study.
Each test cell in the study needs to receive a defined amount of wastewater each day, and that amount needs...
Due to the nature of the analytes being used in the project - bacteria and viruses - the sampling ports had to be carefully located in easy-to-manage spaces that also prevent cross-contamination.