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