Uncharged building blocks of an atom that play a part in radio-activity. They can be found in the nucleus.

A biological process, during which nitrifying bacteria convert toxic ammonia to less harmful nitrate. It is commonly used to remove nitrogen substances from wastewater, but in lakes and ponds it occurs naturally.

Diffuse water pollution sources without a specific point of origin. The pollutants are generally carried off the land by storm water. Common non-point sources are agriculture and atmospheric disposal.

Water that is unsafe or unpalatable to drink because it contains pollutants, contaminants, minerals or infective agents.

The center of an atom, that contains protons and neutrons and carries a positive charge.

Constituents in water, which are not normally harmful to health but may cause offensive taste, odor, color, corrosion, foaming, or staining.

Any substance that promotes growth with living organisms. The term is generally applied to nitrogen and phosphorus in wastewater, but is also applied to other essential and trace elements.

Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern.