Glossary

Abbreviations

COD: CHEMICAL OXYGEN DEMAND
BOD: BIOLOGICAL OXYGEN DEMAND
TSS: TOTAL SUSPENDED SOLIDS
SS: SUSPENDED SOLIDS
FOG: FREE OIL & GREASE
TDS: TOTAL DISSOLVED SOLIDS
TKN*: TOTAL KJELLDAL NITROGEN
TBOD 5: TOTAL BIOLOGICAL DEMAND
NH3-N*: AMMONIA AS NITROGEN
AMB: ASSISTING MOVING BED (Also referred to as MBBR = Moving Bed Bio Reactor)
DO: DISSOLVED OXYGEN
MLSS: MIXED LIQUOR SUSPENDED SOLIDS
PPM: PARTS PER MILLION
MG/L: MILLIGRAM PER LITER (SAME AS PPM)
DWF: DRY WEATHER FLOW
PE: PERSON EQUIVALENTS (Loading factors related to domestic wastewater)
ALF: AIR LIFT FLOTATION
DAF: DISSOLVED AIR FLOTATION
RO: REVERSE OSMOSIS

ACIDIC: Acid forming.

ACTIVATED SLUDGE: The term "activated sludge" refers to a brownish flocculent culture of organisms developed in aeration tanks under controlled conditions. It is also Sludge floc produced in raw or settled waste water by the growth of zoological bacteria and other organisms in the presence of dissolved oxygen. Activated sludge is normally brown in colour.

AEROBIC BACTERIA: Bacteria that are living, active, or occurring only in the presence of oxygen, nitrates and nitrites.

ALKALINITY: The capacity of water to neutralize acids, a property imparted by the water's content of carbonates, bicarbonates, hydroxides, and occasionally borates, silicates, and phosphates. Alkaline fluids have a pH value over 7

ANAEROBIC BACTERIA: Bacteria that live and reproduce in an environment containing no "free" or dissolved oxygen. Anaerobic bacteria obtain their oxygen supply by breaking down chemical compounds which contain oxygen, such as sulfate (SO4).

ANOXIC: A biological environment that is deficient in molecular oxygen, but may contain chemically bound oxygen, such as nitrates and nitrites

BOD Biochemical Oxygen Demand: The rate at which microorganisms use the oxygen in water or wastewater while stabilizing decomposable organic matter under aerobic conditions. In decomposition, organic matter serves as food for the bacteria and energy results from its oxidation.

BACTERIA: Living organisms, microscopic in size, which consist of a single cell. Most bacteria utilizes organic matter for their food and produce waste products as the result of their life processes.

BIO-DEGRADATION: The process of bacteria breaking down a wide variety of compounds to obtain energy and materials for growth.

BULKING SLUDGE: A phenomenon that occurs in activated sludge plants whereby the sludge occupies excessive volumes and will not concentrate readily. This condition refers to a decrease in the ability of the sludge to settle and consequent loss over the settling tank weir. Bulking in activated sludge aeration tanks is caused mainly by excess suspended solids (SS) content. Sludge bulking in the final settling tank of an activated sludge plant may be caused by improper balance of the BOD load, SS concentration in the mixed liquor, or the amount of air used in aeration.

CATALYST: A substance that initiates a chemical reaction.

CAUSTIC: Capable of destroying or eating away by chemical action; corrosive.

COD: Chemical Oxygen Demand. A measure of the oxygen-consuming capacity of inorganic and organic matter present in wastewater. COD is expressed as the amount of oxygen consumed from a chemical oxidant in mg/L during a specific test. Results are not necessarily related to the biochemical oxygen demand because the chemical oxidant may react with substances that bacteria do not stabilize.

COMBINED SEWER: A sewer designed to carry both sanitary wastewaters and storm-water or surface-water runoff.

COMPOSITE SAMPLE: To have significant meaning, samples for laboratory tests on wastewater should be representative of the wastewater. The best method of sampling is proportional composite sampling over several hours during the day. Composite samples are collected because the flow and characteristics of the wastewater are continually changing. A composite sample will give a representative analysis of the wastewater conditions.

COMPOUND: A pure substance composed of two or more elements whose composition is constant. For example, table salt (sodium chloride-NaCl) is a compound.

DENITRIFICATION: A biological process by which nitrate is converted to nitrogen gas.

DIGESTION: The biological decomposition of organic matter in sludge resulting in partial gasification, liquefaction, and mineralization of putrescible and offensive solids.

DISINFECTION: The killing of pathogenic organisms is called disinfection

DISSOLVED SOLIDS: Solids that cannot be removed by filtering are dissolved solids.

DO: Dissolved Oxygen. The atmospheric oxygen dissolved in water or wastewater.

DEGRADATION: The conversion of a substance to simpler compounds. For example, the degradation of organic matter to carbon dioxide and water.

EFFLUENT: Wastewater or other liquid (raw, partially treated or completely treated) flowing from a basin, treatment process, or treatment plant.

ENZYMES: Organic substances which are produced by living cells and speed up chemical changes.

EXTENDED AERATION: A modification of the activated sludge process which provides for aerobic sludge digestion within the aeration system.

FACULTATIVE BACTERIA: Bacteria that can use either molecular (dissolved) oxygen or oxygen obtained from food materials such as sulfate or nitrate ions. Facultative bacteria can live under aerobic or anaerobic conditions.

FILTER MEDIA: Carbon, sand and stones.

FLOC: The aggregation of a number of fine suspended floating particles.

FOG: Fats, oils, and greases.

FORCE MAIN: A pipe that conveys wastewater under pressure from the discharge side of a pump to a point of gravity flow.

GRAVITY MAIN: A sewer line that runs downgrade. Water is pushed by gravity.

GREASE: In wastewater, a group of substances, including fats, waxes, free fatty acids, calcium and magnesium soaps, mineral oils, and certain other non-fatty materials.

HYDROGEN SULFIDE (H2S): A gas with a rotten egg odor. This gas is produced under anaerobic conditions. Hydrogen sulfide is particularly dangerous because after a while it dulls the sense of smell. The odor is also not noticeable in high concentrations. This gas is very poisonous to the respiratory system. It is explosive, flammable and colorless.

INOCULATE: To introduce a seed culture into a system.

INORGANIC WASTE: Waste material such as sand, salt, iron, calcium, and other materials which are only slightly affected by the action of organisms. Inorganic wastes are chemical substances of mineral origin; whereas organic wastes are chemical substances usually of animal or plant origin.

LEACH: To subject to the action of percolating liquid in order to separate the soluble compounds.

LIMONENE: A widely distributed terpene hydrocarbon that occurs in essential oils (such as oranges and lemons) and has a citrus odor.

MICROBE: A microorganism.

MICROBIAL: Pertaining to microorganisms.

MILLIGRAMS PER LITER (mg/L): A unit of concentration of water or wastewater constituent. It is 0.001 g of the constituent in 1000 ml of water. The unit parts per million is identical to milligrams per liter.

MIXED LIQUOR (ML): The mixture of activated sludge, wastewater, and oxygen, wherein biological assimilation occurs.

MIXED LIQUOR SUSPENDED SOLIDS (MLSS): Mixed liquor is a mixture of raw or settled wastewater and activated sludge contained in an aeration basin in the activated sludge process. Mixed liquor suspended solids (MLSS) is the concentration of suspended solids in mixed liquor, usually expressed in milligrams per liter (mg/l). The milligrams of suspended solids per liter of mixed liquor that are combustible at 550 degrees Centigrade. An estimate of the quantity of MLSS to be wasted from the aeration tank of an extended aeration plant may be determined by the rate of settling and centrifuge tests on the sludge solids.

NITRIFICATION: The conversion of nitrogen matter into nitrates by bacteria.

NITROGEN: Nitrogen is present in wastewater in many forms: total Kjeldahl nitrogen, ammonia nitrogen, organic nitrogen.

NITROGEN CYCLE: The cycle of life, death, and decay involving organic nitrogenous matter is known as the nitrogen cycle. In the nitrogen cycle ammonia is produced from proteins.

NUTRIENTS: Substances which are required to support living plants and organisms. Major nutrients are carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorous. Nitrogen and phosphorous are difficult to remove from wastewater by conventional treatment processes because they are water soluble and tend to recycle.

ORGANIC: Relating to or derived from living organisms.

ORGANIC WASTE: Waste material which comes mainly from animal or plant sources. Organic waste generally can be consumed by bacteria and other small organisms. Inorganic wastes are chemical substances of mineral origin.

ORTHOPHOSPHATE: A simple compound of phosphorous and oxygen that is soluble in water.

OXIC: A biological environment which is aerobic

PACKAGE TREATMENT PLANTS: A small wastewater treatment plant often fabricated at the manufacturer's factory, hauled to the site, and installed as one facility. The package may be either a small primary or a secondary wastewater treatment plant.

PATHOGENIC ORGANISMS: Bacteria, viruses or cysts which can cause disease (typhoid, cholera, dysentery). There are many types of bacteria which do not cause disease and which are not called pathogenic. Many beneficial bacteria are found in wastewater treatment processes actively cleaning up organic wastes.

PERCOLATION: The movement of flow of water through soil or rocks.

ph: pH is a measure of the acidity or basicity of a solution. Pure water is said to be neutral. The pH for pure water at 25 °C is close to 7.0. Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are said to be basic or alkaline. pH measurements are important for medicine, biology, chemistry, food science, environmental science, oceanography and many other applications.

POLISH: To bring to a highly developed, finished, or refined state.

POLYPHOSPHATE: A large compound formed of several orthophosphate molecules connected by phosphate-storing microorganisms.

RAW WASTEWATER: Wastewater before it receives any treatment.

REACTOR: A tank where a wastewater stream is mixed with bacterial sludge and biochemical reactions occur.

RETENTION TIME: The time required to fill a tank at a given flow, or the theoretical time required for a given flow of wastewater to pass through a tank.

RETURN SLUDGE : Settled activated sludge returned to mix with incoming raw or primary settled wastewater. When the return sludge rate in the activated sludge process is too low, there will be insufficient organisms to meet the waste load entering the aerator.

RETURN ACTIVATED SLUDGE: Activated return sludge is normally returned continuously to the aeration tank. Recycling of activated sludge back to the aeration tank provides bacteria for incoming wastewater. Its should be brown in color with no obnoxious odor and is often also returned in small portions to the primary settling tanks to aid sedimentation. Settled activated sludge is generally thinner than raw sludge. Some activated sludge will be wasted to prevent excessive solids build up.

SANITARY SEWER: A sewer intended to carry wastewater from homes, businesses, and industries. Storm-water runoff should be collected and transported in a separate system of pipes.

SCUM: Extraneous matter or impurities risen to or formed on the surface of a liquid often as a foul filmy covering.

SEPTIC: A condition produced by anaerobic bacteria. If severe, the wastewater turns black, gives off foul odors, contains little or no dissolved oxygen and creates a heavy oxygen demand.

SLUDGE: Settled solid matter produced by water and sewage treatment processes.

SLUDGE AGE: In the activated sludge process, a measure of the length of time a particle of suspended solids has been undergoing aeration, expressed in day. It is usually computed by dividing the weight of the suspended solids in the aeration tank by the weight of excess activated sludge discharged from the system per day.

SLUDGE DIGESTION: The purpose of sludge digestion is to separate the liquid from the solids to facilitate drying. The proper pH range for digested sludge is 6.8 - 7.2.

SLUDGE INDEX: Properly called sludge volume index (SVI). It is the volume in millimeters occupied by 1 g of activated sludge after settling of the aerated liquid for 30 minutes.

SLUDGE REDUCTION: The continuous aeration of sludge after initial aeration for the purpose of improving or maintaining its condition.

SPLITTER BOX: A division box that splits the incoming flow into two or more streams. A device for splitting and directing discharge from the head box to two separate points of application.

SOLVENT: A substance (usually liquid) capable of dissolving or dispersing one or more other substances.

STORM SEWER: A separate sewer that carries runoff from storms, surface drainage, and street wash, but does not include domestic and industrial wastes.

SURFACTANT: Abbreviation for surface-active agent. It is the active agent in detergents that possesses a high cleaning ability.

TDS: Total Dissolved Solids (often abbreviated TDS) is an expression for the combined content of all inorganic and organic substances contained in a liquid which are present in a molecular, ionized or micro-granular (colloidal sol) suspended form. Generally the operational definition is that the solids must be small enough to survive filtration through a sieve size of two micrometres. Total dissolved solids are normally only discussed for freshwater systems, since salinity comprises some of the ions constituting the definition of TDS.

TSS: Suspended solids refers to small solid particles which remain in suspension in water as a colloid or due to the motion of the water. It is used as one indicator of water quality. It is sometimes abbreviated SS, but is not to be confused with settleable solids, also abbreviated SS, which contribute to the blocking of sewer pipes. Suspended solids are important as pollutants and pathogens are carried on the surface of particles. The smaller the particle size, the greater the surface area per unit mass of particle, and so the greater the pollutant load that is likely to be carried.

TRUNK SEWER: A sewer that receives wastewater from many tributary branches or sewers and serves a large territory and contributing population.

TURBIDITY: Turbidity is a measure of the cloudiness of water- the cloudier the water, the greater the turbidity. Turbidity in water is caused by suspended matter such as clay, silt, and organic matter and by plankton and other microscopic organisms that interfere with the passage of light through the water (American Public Health Association, 1998). Turbidity is closely related to total suspended solids (TSS), but also includes plankton and other organisms.

Turbidity itself is not a major health concern, but high turbidity can interfere with disinfection and provide a medium for microbial growth. It also may indicate the presence of microbes. (U.S. EPA Office of Water, Current Drinking Water Standards).

VIABLE: Capable of living.

WASTEWATER: Domestic wastewater is 99.9% water and 0.1% solids. Fresh wastewater is usually slightly alkaline. If the pH of the raw wastewater is 8.0, it indicates that the sample is alkaline. If wastewater has a pH value of 6.5, it means that it is acid. Wastwater is said to be septic when it is undergoing decomposition.

WET WELL: A compartment or room in which wastewater is collected. The suction pipe of a pump may be connected to the wet well or a submersible pump may be located in the wet well.