Download DEFINITIONS activated sludge process

DEFINITIONS
activated sludge process - A biological wastewater treatment process in which a mixture of
wastewater and activated sludge is agitated and aerated. The activated sludge is
subsequently separated from the treated wastewater (mixed liquor) by sedimentation and
wasted or returned to the process as needed.
aerobic - Requiring, or not destroyed by, the presence of free elemental oxygen.
ammonification - Bacterial decomposition of organic nitrogen to ammonia.
anaerobic - Requiring, or not destroyed by, the absence of air or free (elemental) oxygen.
"Animal Waste", "Manure" - Livestock, poultry, and other animal excreta and associated feed
losses, bedding, litter, and other associated materials.
"Animal Unit" - One animal unit is equivalent to 1,000 pounds of live weight.
BOD - (1) The quantity of oxygen used in the biochemical oxidation of organic matter in a
specified time, at a specified temperature, and under specified conditions.
(2) A standard test used in assessing wastewater strength.
chemical oxygen demand (COD) - A measure of oxygen-consuming capacity of inorganic and
organic matter present in water or wastewater. It is expressed as the amount of oxygen
consumed from a chemical oxidant in a specific test. It does not differentiate between
stable and unstable organic matter and thus does not necessarily correlate with
biochemical oxygen demand. Also known as OC and DOC, oxygen consumed and
dichromate oxygen consumed, respectively.
dissolved oxygen - The oxygen dissolved in water, wastewater, or other liquid, usually
expressed in milligrams per liter, parts per million, or percent of saturation.
Abbreviated DO.
effluent - (1) A liquid which flows out of a containing space.
(2) Wastewater or other liquid, partially or completely treated, or in its natural state,
flowing out of a reservoir, basin, treatment plant, or industrial treatment plant, or
part thereof.
(3) An outflowing branch of a main stream or lake.
Escherichia coli (E. coli) - One of the species of bacteria in the coliform group. Its presence is
considered indicative of fresh fecal contamination.
extended aeration - A modification of the activated sludge process which provides for aerobic
sludge digestion within the aeration system. The concept envisages the stabilization of
organic matter under aerobic conditions and disposal of the end products into the air as
gases and with the plant effluent as finely divided suspended matter and soluble matter.
facultative anaerobic bacteria - Bacteria which can adapt themselves to growth in the
presence, as well as in the absence, of oxygen. May be referred to as facultative
bacteria.
influent - Water, wastewater, or other liquid flowing into a reservoir, basin, or treatment plant, or
any unit thereof.
lagoon - A pond containing raw or partially treated wastewater in which aerobic or anaerobic
stabilization occurs. Can be an aerobic or anaerobic lagoon.
nitrification - (1)
(2)
The conversion of nitrogenous matter into nitrates by bacteria.
The treatment of a material with nitric acid.
oxidation - The addition of oxygen to a compound. More generally, any reaction which involves
the loss of electrons from an atom.
oxidation-reduction potential - The potential required to transfer electrons from the oxidant
to the reductant and used as a qualitative measure of the state of oxidation in
wastewater treatment systems.
parts per million - The number of weight or volume units of a minor constituent present with
each one million units of the major constituent of a solution or mixture. Formerly used to
express the results of most water and wastewater analyses, but more recently replaced by
the ratio milligrams per liter.
population equivalent - A means of expressing the strength of organic material in wastewater.
Domestic wastewater consumes, on an average, 0.17 pound of oxygen per capita per
day, as measured by the standard BOD test. This figure has been used to measure the
strength of organic industrial waste in terms of an equivalent number of persons. For
example, if an industry discharges 1,000 pounds of BOD per day, its waste is equivalent
to the domestic wastewater from 6,000 persons (1,000/0.17 = 6,000).
total solids - The sum of dissolved and undissolved constituents in water or wastewater,
usually stated in milligrams per liter.
water quality - The chemical, physical, and biological characteristics of water with respect to its
suitability for a particular purpose. The same water may be of good quality for one
purpose or use, and bad for another, depending on its characteristics and the
requirements for the particular use.
water standards - Definitions of water quality established as a basis of control for various
water-use classifications.