Terms & Definitions
The penetration of one substance into the inner structure of another.
Treatment with acid to lower the pH. Also refers to an emulsion breaking process.
Sludge particles produced in raw or settled wastewater (primary effluent) by the growth of microbiological organisms. Activate sludge is different from primary sludge in that the sludge particles contain many living organisms (bacteria, fungi & protozoa), which use the incoming wastewater as a source of food.
A biological wastewater treatment process which converts soluble organics into settable insoluble solids through the use of microorganisms. The solids are collected in a sedimentation step (see Secondary Clarifier) and returned to the aeration basin (RAS) or wasted (WAS) as the operation characteristics of the system dictate.
The chemical compound that results when one hydrogen atom in ammonia is replaced by acrylic acid.
A salt or ester of acrylic acid.
Any process that upgrades treated wastewater to meet specific reuse standards. May also be referred to as tertiary treatment.
The adherence of dissolved colloidal or finely divided solids onto the surface of solid particle or body in which they come into contact.
The process of air addition. In wastewater treatment, this process serves two purposes: 1). Mixing & 2). Oxygen addition to support microorganisms.
The tank where raw or returned activated sludge is mixed and aerated.
Bacteria that must have dissolved oxygen present to survive.
A condition in which dissolved or “free” oxygen is present in the aquatic environment.
Bacteria that live and reproduce only in an environment where dissolved oxygen is present.
The decomposition of wastes by microorganisms in the presence of dissolved oxygen.
The growth or clumping of smaller particles into larger particles or floc, which will rapidly settle.
Aluminum sulfate coagulant. Usually provided in liquid form but can be used in “dry” form as well.
A condition in which “free” or dissolved oxygen is not present.
Bacteria that live and reproduce in an environment containing no “free” or dissolved oxygen.
Wastewater solids, usually at 5% solids, that are decomposed by bacteria in the absence of dissolved oxygen.
An ionic type of cleaning product that contains a negatively charge surface-active agent.
A sterile or germ free environment.
An abbreviation for the term, Biochemical Oxygen Demand. It is the rate at which microorganisms’ use dissolved oxygen in water or wastewater for the conversion of dissolved organics into cellular material.
A laboratory procedure that measures the rate of oxygen use under controlled conditions of time and temperature.
A mass or clump of living organisms feeding on wastes, dead organisms or debris in wastewater.
Clouds of billowing sludge usually associated with algae or bacteria in secondary clarifiers when the sludge becomes too light to settle properly.
A mechanical device that uses gravitational forces at high speed to separate solids from liquids.
A measure of the rate of oxygen consumption by organic and inorganic compounds in wastewater.
Any process or combination of processes whose major purpose is reducing the concentration of suspended matter in a liquid phase.
Any chemical or substance used to assist coagulation.
The use of chemicals to cause small particles to agglomerate into larger particles, thus making separation of solids from liquid easier.
Very finely divided particles that remain dispersed in a liquid phase for long periods of time due to their electrical charge and small size.
In contact stabilization, which is a modification of the conventional activated sludge process, two (2) aeration tanks are used. One tank is used for separate re-aeration of return sludge, usually for at least four (4) hours, before it flows into the other tank where it is mixed with raw primary wastewater.
A condition in which nitrite or nitrate ions are reduce to nitrogen gas. The resulting bubbles often cause floating sludge in secondary clarifiers or gravity thickeners.
A tank in which sludge is placed to allow decomposition by micr