Wastewater Treatment 1

Front 1

Activated Sludge Process

Back 1

A biological wastewater treatment process that speeds up the decomposition of wastes in the wastewater being treated. Activated sludge is added to wastewater and the mixture (mixed liquor) is aerated and agitated. After some time in the aeration tank, the activated sludge is allowed to settle out by sedimentation and is disposed of (wasted) or reused (returned to the aeration tank) as needed. The remaining wastewater then undergoes more treatment.

Front 2

Bulking

Back 2

Clouds of billowing sludge that occur throughout secondary clarifiers and sludge thickeners when the sludge does not settle properly. In the activated sludge process, bulking is usually caused by filamentous bacteria or bound water.

Front 3

Coagulant

Back 3

A chemical that causes very fine particles to clump (floc) together into larger particles. This makes it easier to separate the solids from the liquids by settling, skimming, draining, or filtering.

Front 4

Colloids

Back 4

Very small, finely divided solids (particles that do not dissolve) that remain dispersed in a liquid for a long time due to their small size and electrical charge. When most of the particles in water have a negative electrical charge, they tend to repel each other. This repulsion prevents the particles from clumping together, becoming heavier, and settling out.

Front 5

Composite (Proportional) Sample

Back 5

A composite sample is a collection of individual samples obtained at regular intervals, usually every one or two hours during a 24-hour time span. Each individual sample is combined with the others in proportion to the rate of flow when the sample was collected. Equal volume individual samples also may be collected at intervals after a specific volume of flow passes the sampling point or after equal time intervals and still be referred to as a composite sample. The resulting mixture (composite sample) forms a representative sample and is analyzed to determine the average conditions during the sampling period.2. To remove or drain the water from a tank or a trench. A structure may be dewatered so that it can be inspected or repaired.

Front 6

Density

Back 6

A measure of how heavy a substance (solid, liquid, or gas) is for its size. Density is expressed in terms of weight per unit volume, that is, grams per cubic centimeter or pounds per cubic foot. The density of water (at 4°C or 39°F) is 1.0 gram per cubic centimeter or about 62.4 pounds per cubic foot.

Front 7

Emulsion

Back 7

A liquid mixture of two or more liquid substances not normally dissolved in one another; one liquid is held in suspension in the other.

Front 8

Flights

Back 8

Scraper boards, made from redwood or other rot-resistant woods or plastic, used to collect and move settled sludge or floating scum.

Front 9

Flocculation

Back 9

The gathering together of fine particles after coagulation to form larger particles by a process of gentle mixing. This clumping together makes it easier to separate the solids from the water by settling, skimming, draining, or filtering.

Front 10

Freeboard

Back 10

The vertical distance from the normal water surface to the top of the confining wall.The vertical distance from the sand surface to the underside of a trough in a sand filter. This distance is also called available expansion.

Front 11

Gasification

Back 11

The conversion of soluble and suspended organic materials into gas during aerobic or anaerobic decomposition. In clarifiers, the resulting gas bubbles can become attached to the settled sludge and cause large clumps of sludge to rise and float on the water surface. In anaerobic sludge digesters, this gas is collected for fuel or disposed of using a waste gas burner.

Front 12

Hydraulic Loading

Back 12

Hydraulic loading refers to the flows (MGD or cu m/day) to a treatment plant or treatment process. Detention times, surface loadings, and weir overflow rates are directly influenced by flows.

Front 13

Hydrostatic System

Back 13

In a hydrostatic sludge removal system, the surface of the water in the clarifier is higher than the surface of the water in the sludge well or hopper. This difference in pressure head forces sludge from the bottom of the clarifier to flow through pipes to the sludge well or hopper.

Front 14

Launders

Back 14

Sedimentation basin and filter discharge channels consisting of overflow weir plates (in sedimentation basins) and conveying troughs.Sedimentation tank effluent troughs consisting of overflow weir plates.

Front 15

Lineal

Back 15

The length in one direction of a line. For example, a board 12 feet (meters) long has 12 lineal feet (meters) in its length.2. The deposits of foreign materials on the bottoms of streams or other bodies of water or on the bottoms and edges of ww collection lines and appurtenances.

Front 16

MPN

Back 16

MPN is the Most Probable Number of coliform-group organisms per unit volume of sample water. Expressed as a density or population of organisms per 100 mL of sample water.

Front 17

Masking Agents

Back 17

Substances used to cover up or disguise unpleasant odors. Liquid masking agents are dripped into the wastewater, sprayed into the air, or evaporated (using heat) with the unpleasant fumes or odors and then discharged into the air by blowers to make an undesirable odor less noticeable.2. A wall or obstruction used to control flow (from settling tanks and clarifiers) to ensure a uniform flow reate and avoid short-circuiting.

Front 18

Millimicron

Back 18

A unit of length equal to 10–3µ (one thousandth of a micron), 10–6 millimeters, or 10–9 meters; correctly called a nanometer, nm.

Front 19

Molecule

Back 19

The smallest division of a compound that still retains or exhibits all the properties of the substance.

Front 20

OSHA

Back 20

The Williams-Steiger Occupational Safety and Health Act of 1970 (OSHA) is a federal law designed to protect the health and safety of workers, including the operators of water supply and treatment systems and wastewater collection and treatment systems. The Act regulates the design, construction, operation, and maintenance of water and wastewater systems. OSHA regulations require employers to obtain and make available to workers the Material Safety Data Sheets (MSDSs) for chemicals used at industrial facilities and treatment plants. OSHA also refers to the federal and state agencies that administer the OSHA regulations.

Front 21

Package Treatment Plant

Back 21

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.

Front 22

Representative Sample

Back 22

A sample portion of material, water, or wastestream that is as nearly identical in content and consistency as possible to that in the larger body being sampled.

Front 23

Retention Time

Back 23

The length of time water, sludge, or solids are retained or held in a clarifier or sedimentation tank. Also see DETENTION TIME.

Front 24

Rotating Biological Contactor (RBC)

Back 24

A secondary biological treatment process for domestic and biodegradable industrial wastes. Biological contactors have a rotating shaft surrounded by plastic discs called the media. The shaft and media are called the drum. A biological slime grows on the media when conditions are suitable and the microorganisms that make up the slime (biomass) stabilize the waste products by using the organic material for growth and reproduction.

Front 25

Septicity

Back 25

The condition in which organic matter decomposes to form foul-smelling products associated with the absence of free oxygen. If severe, the wastewater produces hydrogen sulfide, turns black, gives off foul odors, contains little or no dissolved oxygen, and the wastewater has a high oxygen demand.

Front 26

Sloughings

Back 26

Trickling filter slimes that have been washed off the filter media. They are generally quite high in BOD and will lower effluent quality unless removed.

Front 27

Sludge Gasification

Back 27

A process in which soluble and suspended organic matter are converted into gas by anaerobic decomposition. The resulting gas bubbles can become attached to the settled sludge and cause large clumps of sludge to rise and float on the water surface.

Front 28

Sludge Volume Index (SVI)

Back 28

A calculation that indicates the tendency of activated sludge solids (aerated solids) to thicken or to become concentrated during the sedimentation/thickening process. SVI is calculated in the following manner: (1) allow a mixed liquor sample from the aeration basin to settle for 30 minutes; (2) determine the suspended solids concentration for a sample of the same mixed liquor; (3) calculate SVI by dividing the measured (or observed) wet volume (mL/L) of the settled sludge by the dry weight concentration of MLSS in grams/L.

Front 29

Specific Gravity

Back 29

Weight of a particle, substance, or chemical solution in relation to the weight of an equal volume of water. Water has a specific gravity of 1.000 at 4C (39F). Particulates with specific gravity less than 1.0 float to the surface and particulates with specific gravity greater than 1.0 sink. Wastewater particles or substances usually have a specific gravity of 0.5 to 2.5.Weight of a particular gas in relation to the weight of an equal volume of air at the same temperature and pressure (air has a specific gravity of 1.0). Chlorine gas has a specific gravity of 2.5.

Front 30

Surface Loading

Back 30

One of the guidelines for the design of settling tanks and clarifiers in treatment plants. Used by operators to determine if tanks and clarifiers are hydraulically (flow) over- or underloaded. Also called overflow rate.

Front 31

Toxic

Back 31

A substance that is poisonous to a living organism. Toxic substances may be classified in terms of their physiological action, such as irritants, asphyxiants, systemic poisons, and anesthetics and narcotics. Irritants are corrosive substances that attack the mucous membrane surfaces of the body. Asphyxiants interfere with breathing. Systemic poisons are hazardous substances that injure or destroy internal organs of the body. Anesthetics and narcotics are hazardous substances that depress the central nervous system and lead to unconsciousness.

Front 32

Trickling Filter

Back 32

A treatment process in which wastewater trickling over media enables the formation of slimes or biomass, which contain organisms that feed upon and remove wastes from the water being treated.

Front 33

Weir Diameter

Back 33

Many circular clarifiers have a circular weir within the outside edge of the clarifier. All the water leaving the clarifier flows over this weir. The diameter of the weir is the length of a line from one edge of a weir to the opposite edge and passing through the center of the circle formed by the weir.