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 microorganisms.
A mechanical device which facilitates the separation of solids from the liquid phase be use of super-saturated air to generate floatation bubbles.
Molecular oxygen dissolved in water or wastewater and is usually abbreviates as DO.
Wastewater or other liquid flowing from a tank, process or container.
A holding basin in which variations in flow or concentration are averaged.
Bacteria that can live under aerobic or anaerobic conditions.
The gathering together of finer particles to form larger particles.
GRAS means generally recognized as safe. It is the designation given to substances that are considered safe for direct or indirect additives to foods. For a substance to be considered GRAS it had to meet certain criteria. There are two basic ways for a substance to be designated as GRAS. The criteria for this process is given in detail in the Code of Federal Regulations Title 21, Volume 3, Parts 170.30. The Federal code is searchable from: http://www.gpoaccess.gov/cfr/retrieve.html
Wastewater or other liquid flowing into a tank, container or process.
A laboratory procedure for estimation of the amount of chemical that will be needed to achieve selected water quality standards.
Material Safety Data Sheet – an MSDS provide important product information for proper handling, storage, shipping and other areas that employees dealing with said product should know.
The mixing of activated sludge with raw wastewater and return sludge in an aeration tank. Mixed liquor may also refer to the contents of aerobic and anaerobic digesters.
The suspendedsolids in the mixed liquor of an aeration tank. Comprised of volatile and non-volatile suspended solids.
The organic or volatile suspended solids in the mixed liquor of an aeration tank. Commonly used to indicate viable bacteria content when compared to MLLS.
Organisms that exhibit or are capable of movement.
NSF is the only standards development and certification organization with over 50 years of dedicated service to public health safety and environmental quality. The NSF Mark certifies a product as meeting rigorous public health safety standards.
National Pollutant Discharge Elimination Discharge System permit is the regulatory document that was designed to control all discharges of pollutants from point sources into U.S. waterways.
A process in which bacteria change ammonia or organic nitrogen in wastewater into form of oxidized nitrogen, usually nitrate.
Substances that are required for supporting living plants and organisms.
Salt or acid containing phosphorus as PO4.
Oxidation is the addition of oxygen, removal of hydrogen or the removal of electrons from an element or compound.
Water intended for drinking, or general public consumption or use.
The reciprocal of the logarithm of the hydrogen ion concentration.
A high molecular weight substance that is formed be either a natural or synthetic process. Often called a “polymer”.
Natural polymers may be of biological origin or derived from starch products, cellulose derivatives and alginates. Synthetic polyelectrolyte consist of simple substances that have been made into complex, high molecular weight substances.
The first major and in some cases the only treatment step taken in a wastewater treatment plant. Usually sedimentation.
The process of deposition of suspended matter carried by water, wastewater or other liquid by gravity.
A test used to indicate the settling ability of activated sludge in the secondary clarifier.
A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated.
A condition produced by anaerobic bacteria. If severe, the water turns black, gives off a foul odor and contains little or no dissolved oxygen.
The arrival at a process or plant of a waste that is toxic to organisms in sufficient quantity or strength to cause operational problems.
A process that removes specific wastes not generally removed by conventional treatment processes.
The quantity of solids in water, wastewater or other liquids lost on ignition of the dry solids at 600oC.