Discharging certain substances into the sewer system can:
interfere with the operation of the wastewater treatment facility (WWTF) by upsetting the biological process and killing the microorganisms needed for proper treatment
jeopardize the health and safety of NBC personnel
clog sewer lines
be extremely dangerous if dumped in high concentrations
mix with other chemicals to form toxic gases
WWTFs are not designed to remove heavy metals, cyanide and other toxic chemicals. Approximately 40 to 60 percent of these substances can settle out of the wastewater and into the sludge, contaminating it and preventing its reuse, while the remainder empties into Narragansett Bay and its tributaries.
Once this happens, marine life is exposed to toxic substances, which may enter the food chain and can eventually affect people. In addition, these toxics can prevent the NBC from meeting its effluent limits that are established by EPA and RI DEM.
To control toxic discharges at the source, the federal Environmental Protection Agency (EPA) requires that the NBC to implement a Pretreatment Program.
What is a Pretreatment Program?
A Pretreatment Program permits, monitors and regulates a variety of industries in order to protect NBC treatment facilities and Narragansett Bay from the discharge of harmful contaminants.
Industries that are typically regulated are:
electroplaters, metal finishers
chemical manufacturers
machine shops
laboratories
hospitals
laundromats
restaurants
other firms that are tied into the NBC's sewer system
To date, this program has had a major positive impact on the quality of treatment and discharges from the Field's Point and Bucklin Point WWTFs and has dramatically reduced the amount of metals and toxics being dumped into the sewer system and ultimately into Narragansett Bay.
For example, in 1981, local industries discharged 954,099 pounds of heavy metals and 80,440 pounds of cyanide to the Field's Point wastewater treatment facility. By
2006 significant reductions in metals (96.6%) and cyanide (96.7%) were achieved. Additionally, nearly
95% of all regulated users adhere to NBC’s environmental regulations. Because
of these great metals and cyanide reductions the Providence and Seekonk
Rivers have been removed from the EPA 303(d) list of impaired waters for
toxics.