About Us

The Greater Lawrence Sanitary District was designed for a maximum flow of 52 million gallons per day (MGD), and receives and average daily flow of 30 MGD. The District serves five communities, and a total population of approximately 216,000 people. Additionally, GLSD services 30 industries as part of the District’s Pretreatment Program. On average, it takes 12 hours for water to be treated and discharged back into the Merrimack River.

National Pollutant Discharge Elimination System (NPDES)

“The NPDES permit program addresses water pollution by regulating point sources that discharge pollutants to waters of the United States.

Created in 1972 by the Clean Water Act, the NPDES permit program is authorized to state governments by EPA to perform many permitting, administrative, and enforcement aspects of the program.”

The NPDES permits for municipal wastewater treatment facilities are renewed every five years and they “establish discharge limits and conditions for discharges from [these facilities] to waters of the U.S.”

Examples of parameters that are regulated by the NPDES Permit are:

  1. Flow
  2. Biological oxygen demand (BOD)5
  3. Total suspended solids (TSS)
  4. pH
  5. Total chlorine residual (TCR)
  6. Fecal coliform (FC)
  7. Dissolved oxygen (DO)
  8. Ammonia nitrogen, total kjeldahl nitrogen, nitrate, and nitrite
  9. Total phosphorus (TP)
  10. Whole effluent toxicity

A copy of the Greater Lawrence Sanitary District’s NPDES permit can be found here. It will be renewed in August of 2016.

For more information about the NPDES permit program, visit: https://www.epa.gov/npdes

[1] National Pollutant Discharge Elimination System (NPDES). (2015, November 16). Retrieved June 20, 2016, from https://www.epa.gov/npdes
[2] Ibid.