Wastewater and Sewage Treatment
Aeration tank
A chamber for injecting air and oxygen into water; primary effluent is mixed with return activated sludge to form the mixed liquor
Floc
A clump of solids formed in sewage by biological or chemical action
Domestic wastewater
A combination of human/animal excreta (feces and urine) and "grey water" resulting from washing, bathing, & cooking
Barminutor
A device mounted on bar screens in a wastewater treatment plant to shred material, such as rags and debris, that accumulates on the bars
Chlorinator
A device that adds chlorine, in gas or liquid form, to wastewater to kill infectious bacteria
Comminutor
A device to catch and shred heavy solid matter at the headworks of the wastewater treatment plant
Ozonation
A disinfection process where ozone is generated and added to wastewater effluent to kill pathogenic organisms
UV radiation
A disinfection process where wastewater is exposed to UV light for disinfection
Wastewater treatment plant
A facility involving a series of tanks, screens, filters, and other treatment processes by which pollutants are removed from water
Trickling filter
A fixed film process that involves a tank, usually filled with a bed of rocks, stones or synthetic media, to support bacterial growth used to treat wastewater; provides a large surface area
Polymer
A long chain organic compound produced by the joining of primary units called monomers; used to improve settling of suspended solids, remove solids from wastewater, and improve dewatering of biosolids
Biochemical oxygen demand (BOD)
A measure of oxygen consumed in biological processes that break down organic matter in water
Pump
A mechanical device for raising or lifting water or other fluid, or for applying pressure to fluids in pipes
Grinder pump
A mechanical device which shreds wastewater solids and raises the fluid pressure level high enough to pass wastewater through small diameter pressure sewers
Carbon adsorption
A method to treat wastewater in which activated carbon removes trace organic matter that resists degradation
Phosphorus
A nutrient that is essential to life, but in excess, contributes to the eutrophication of lakes and other water bodies
National Pollutant Discharge Elimination System (NPDES)
A program established by the Clean Water Act (CWA) that requires all wastewater discharges into "waters of the United States" to obtain a permit issued by the US Environmental Protection Agency (EPA) or a state agency authorized by the EPA
Storm sewers
A separate system of pipes that carry rain and snow melt from buildings, streets and yards to surface waters
Lagoon
A shallow pond in which algae, aerobic and anaerobic bacterial purify wastewater
Grit chamber
A small detention basin designed to permit the settling of coarse, heavy inorganic solids, such as sand, while allowing the lighter organic solids to pass through the chamber
Soil adsorption field
A subsurface area containing a trench or bed with a minimum depth of 12 inches of clean stones and a system of piping through which treated wastewater effluent is distributed into the surrounding soil for further treatment and disposal
Activated sludge
A suspended growth process for removing organic matter from sewage by saturating it with air and microorganisms that can break down the organic matter; started in England in the early 1900s; aerobic bacteria growing in flocs degrade the material
Pressure sewers
A system of pipes in which the water, wastewater or other liquid is transported under pressure supplied by pumps
Sewers
A system of pipes that collect and deliver wastewater and/or stormwater to treatment plants or receiving waters
Diffused air
A technique by which air under pressure is forced into sewage in an aeration tank; the air is pumped into the tank through a perforated pipe and moves as bubbles through the sewage
Septic tanks
A type of onsite wastewater treatment system in which the organic waste is decomposed and solids settle out; the effluent flows out of the tank to a soil adsorption field or other dispersal system
Biotower
A unit in which the waste is allowed to fall through a tower packed with synthetic media on which there is biological growth similar to the trickling filter
Sequencing batch reactors (SBR)
A variation of the activated sludge process where all treatment processes occur in one tank that is filled with wastewater and drawn down to discharge after treatment is complete
Alternative system
A wastewater treatment or collection system utilized in lieu of a conventional system
Clarifier
Also known as a settling tank, removes solids from wastewater by gravity settling or by coagulation
Oxidation pond
An aerated man-made pond used for wastewater treatment
Mound system
An effluent disposal system involving a mound of soil built up on the original ground surface to which effluent is distributed
Algae
Aquatic organisms which grow in sunlit waters and release oxygen into the water; most are a food for fish and small aquatic animals, but some cause water quality problems
Combined sewers
Carry both sewage and stormwater runoff
Bar screen
Composed of parallel bars that remove larger objects from wastewater
Industrial wastewater
Contains nontoxic wastes from food processing and toxic wastes from petrochemical, pharmaceutical, pesticide, and other businesses
Pathogens
Disease-causing microorganisms, including pathogenic bacteria, viruses, helminths, and protozoans
Nutrients
Elements or compounds essential as raw materials for plant and animal growth and development
Organic material, pathogens
Found in agricultural and domestic wastewater
Intermittent sand filter
Involves a bed of sand or other fine-grained material to which wastewater is applied intermittently in flooding doses
Media filter
Involves a bed of sand or other fine-grained material to which wastewater is applied, generally to physically remove suspended solids from sewage; bacteria on the media decompose additional wastes; treated water drains from the bed; solids that accumulate at the surface must be removed from the bed periodically
Dispersal/percolation
Involves a volume of wastewater applied to the land, penetrating the surface, and passing through the underlying soil
Oxidation
Involves aerobic bacteria breaking down organic matter and oxygen combining with chemicals in sewage
Incineration
Involves combustion of the organic matter in sewage sludge, producing a residual inert ash
Slow rate land treatment
Involves the controlled application of wastewater to vegetated land at a few inches of liquid per week
Advanced treatment
Involves treatment levels beyond secondary treatment
Pretreatment
Involves treatment of wastes or wastewater by industries performed prior to the discharge to the sewer system
Overland flow
Land treatment which involves the controlled application of wastewater onto grass-covered gentle slopes, with impermeable surface soils; as water flows over the grass-covered soil surface, contaminants are removed and the water is collected at the bottom of the slope for reuse
Interceptors
Large sewer lines that collect the flows from smaller main and trunk sewers and carry them to the treatment plant
Clean Water Act
Originally enacted in 1948 and amended in 1972, 1981 and 1987; has as its objective the restoration and maintenance of the "chemical, physical, and biological integrity of the Nation's waters"
Aerobic treatment units
Provide wastewater treatment by injecting air into a tank, allowing aerobic bacteria to treat the wastewater
Anaerobic
Refers to a life or a process that occurs in the absence of free oxygen
Aerobic
Refers to a life or a process that occurs in the presence of oxygen
Inorganic
Refers to compounds that do not contain carbon
Gray water
Refers to domestic wastewater composed of wash water from sinks, shower, washing machines
Septage
Refers to the residual solids in septic tanks or other on-site wastewater treatment systems that must be removed periodically for disposal
Influent
Refers to water, wastewater, or other liquid flowing into a reservoir, basin or treatment plant, or any unit thereof
Impervious
Resistant to penetration by fluids or by roots
Pollution
Results when contaminants in human, animal, vegetable, mineral, chemical or thermal waste or discharges reach water, making it less desirable for domestic, recreation, industry, or wildlife uses
Lateral sewers
Small pipes that are placed in the ground to receive sewage from homes and businesses and convey it to main, trunk and interceptor sewer lines leading to the wastewater treatment plant
Settleable solids
Solids that are heavier than water and settle out of water by gravity
Digestion
Takes place in tanks where volatile organic materials are decomposed by bacteria, resulting in partial gasification, liquefaction, and mineralization of pollutants
Dissolved oxygen
The amount of free oxygen in solution in water, or wastewater effluent; adequate concentrations are necessary for fish and other aquatic organisms to live and to prevent offensive odors
Nitrification
The biochemical oxidation of ammonium to nitrate
Organic matter
The carbonaceous material contained in plants or animals and wastes
Coagulation
The clumping together of solids to make them settle out of the sewage faster; improved by the use of chemicals such as lime, alum, iron salts, or polymers
Sanitary sewer
The collection system for transporting domestic and industrial wastewater to municipal wastewater treatment facilities; stormwater is not directed into this system but is handled by a separate system
Land application
The controlledapplication of wastewater or biosolids onto the ground for treatment and/or reuse
Water table
The elevation of groundwater or saturated soil level in the ground
Primary treatment
The initial stage of wastewater treatment that removes floating material and material that easily settles out; involves screens, settling tanks and skimmers to remove suspended solids; physical separation
Disinfection
The killing of pathogenic microbes including pathogenic bacteria, viruses, helminths, and protozoans
Permeability
The measure of the ease with which water penetrates or passes through soil
Percolation
The movement of water through sub-surface soil layers, usually continuing downward to the groundwater
Compositing
The natural biological decomposition of organic material in the presence of air to form a stabilized, humus-like material
Eutrophication
The normally slow aging process by which a lake evolves into a bog or marsh and ultimately disappears; the lake becomes enriched with nutrients, especially nitrogen and phosphorus, which support the excess production of algae and other aquatic plant life; may be accelerated by many human activities
Infiltration
The penetration of water through the ground into sub-surface soil or the passing of water from the soil into a pipe, such as a sewer
25-50%
The percentage of non-water waste in domestic wastewater that consists of carbohydrates
10%
The percentage of non-water waste in domestic wastewater that consists of fats and oils, urea, and trace organics (including surfactants and pesticides); the percentage of nitrogen associated with cell biomass that is removed during. settling
40-60%
The percentage of non-water waste in domestic wastewater that consists of proteins
Flocculation
The process by which clumps of solids in sewage are made to increase in size by chemical action
Transpiration
The process by which water vapor is released to the atmosphere by living plants
Chlorination
The process of adding chlorine gas or chlorine compounds to wastewater for disinfection
Denitrification
The reduction of nitrite to nitrogen gas; carried out in wastewater treatment tanks by bacteria under anoxic conditions, i.e. anaerobic respiration by facultative anaerobes like Pseudomonas spp.
Secondary treatment
The second stage in most wastewater treatment systems in which bacteria consume the organic matter in wastewater; involves aerobic microbiological processes such as trickling filters and activated sludge; helps remove BOD and nutrients
Seepage
The slow movement of water through small cracks or pores of the soil, or out of a pond, tank or pipe
Suspended solids
The small particles suspended in water or wastewater
Black water
The term given to domestic wastewater that carries animal, human, or food wastes
Effluent
The treated liquid that comes out of a treatment plant after completion of the treatment process
Evapotranspiration
The uptake of water from the soil by evaporation and by transpiration from the plants growing thereon
Biological nutrient removal (BNR)
The use of bacteria to remove nutrients from wastewater
Groundwater
The zone beneath the ground surface saturated with water that has seeped down through soil and rock
Biosolids
Treated sewage sludge solids that have been stabilized to destroy pathogens and meet rigorous standards allowing for safe reuse of this material as a soil amendment
Mechanical aeration
Uses mechanical energy to inject air from the atmosphere into water to provide oxygen to create aerobic conditions
Nitrogenous wastes
Wastes that contain a significant concentration of nitrogen
Eligible costs
Wastewater reduction activities that can be funded with State Revolving Fund (SRF) loans
Rotating biological contactor
Wastewater treatment process involving large, closely-spaced plastic discs rotated about a horizontal shaft; the discs alternately move through the wastewater and the air, developing a biological growth on the surface of the discs that removes organic material in the wastewater
Conventional systems
Wastewater treatment systems that have been traditionally used to collect municipal wastewater in sewers and convey it to a central facility for treatment prior to discharge to surface waters; either primary or secondary treatment may be provided
Sedimentation tanks
Wastewater treatment tanks in which floating wastes are skimmed off and settled solids are removed for disposal
Receiving waters
Waterbodies (i.e. rivers, lakes, oceans, or other water courses) that receive discharges of treated or untreated wastewater
1900s
When sewage treatment began