Some Commonly Used Words and their Definitions


Bacteria – Microscopic one-celled organisms found everywhere.  Some bacteria have the potential to be a public health threat.  In Massachusetts there are defined limits for a specific bacteria, (fecal coliform) in water bodies.


Class A, B, C water quality standards- Under the Federal Clean Water Act, each state must establish specific water quality classifications with defined water quality criteria. In Massachusetts waters are assigned an A, B or C classification. A waterway’s classification reflects the water quality needed for the designated uses of a given water body (the waterways potential) and not the existing water quality.


Class B water- A waterway classified by the state as being capable of meeting the following, “suitable habitat for fish, other aquatic life and wildlife, and primary and secondary contact recreation. Can be used, when so designated, as drinking water with proper treatment and for agriculture and industry and good and consistent aesthetic value.”


Clean Water Act (CWA) – A federal law establishing comprehensive national policies for water quality management.  The essence of the CWA is to have all US waters “fishable and swim able”.


Cultural Eutrophication- When the natural process of eutrophication, growth and decay in an aquatic ecosystem, is accelerated by an increase of nutrients derived from societal sources such as lawns, roads, wastewater, and stormwater runoff.


Effluent – Wastewater as it leaves a treatment system.  Examples are discharges from sewage treatment facilities or water used in an industrial cooling system.


Eutrophication- Eutrophication is the natural process of nutrients entering a water body resulting in increased biological activity. The natural processes may be accelerated and intensified by human activities that cause excessive quantities of nutrients to flow into a water body leading to unchecked growth of aquatic plants, subsequent depleted oxygen levels and in some cases the collapse of the aquatic ecosystem and the premature succession of the area a wetland or upland.


Industrial discharge - Discharges of wastewater (it may be treated contact water or untreated non-contact process or cooling water)  from an industrial facility into the waters of the United States. Industrial discharges are regulated under a provision of the federal Clean Water Act and must obtain a permit (NPDES) to discharge.


National Pollution Discharge Elimination System (NPDES) – A federal program under the Clean Water Act created to monitor, regulate and oversee discharges, such as sewage treatment plant effluent, storm water and industrial discharges, into US waterways. Currently a permit system is used for point source discharges that sets specific limits and criteria for the discharge. Permit holders must submit monthly reports detailing their compliance with their NPDES permit


Nitrate – A form of nitrogen readily usable by vegetation.  Excessive amounts of nitrate can disrupt ecological balances in a natural system, particularly in salt water and pose some public health threats. 


Nutrients, (nitrates and phosphates)- Nutrients are essential for growth in both plants and animals with nitrogen and phosphorus being significant for growth in plants. There are several common forms of nitrogen including nitrite, nitrate, and ammonia. Nitrate is a form of nitrogen easily absorbed and used by plants and is a byproduct of the oxidation of ammonia. Phosphate usually occurs in low concentrations in water and plant growth in fresh water is limited by the amount of phosphate present in the water.  


Phosphorus – A nutrient often serving as the limit to growth in freshwater systems.  Excessive amount of phosphorus in a water body can lead to a condition of unchecked plant growth known as eutrophication.


Total Maximum Daily Load (TMDL) – A section in the Federal Clean Water Act  requiring each state to identify water bodies that are not meeting their assigned water quality standard, ascertain the cause(s) of impairment and determine the maximum amount of that pollutant(s) a waterway can receive, (total daily maximum load) yet still meet water quality standards. Using this amount, a TMDL establishes the allowable pollutant loading from all contributing sources so the total, including a margin of safety, falls at or below the maximum daily allowable pollutant load.


Total Phosphorus- Phosphorus is a nutrient essential for the growth of most plants. Phosphorus can be found in both the organic and inorganic forms. Total phosphorus is a measure of both these forms.


Tributary – A stream or river flowing into a larger, mainstream river.


Wastewater – Water that is used for some purpose then discharged or “wasted”.  Usually refers to the water used in households, business and industry.


Watershed – An area of land contributing runoff/drainage to a common point.  Large watershed may be divided into smaller sub-watersheds.


303d list- 303 d refers to a section in the federal Clean Water Act requiring all states to submit, biennially to the EPA, a list of waterways not meeting assigned water quality standards.  The 303 d is a list of the known impaired waters in a state or on tribal lands.