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Wastewater Terms
Common Terms and Definitions & Abbreviations
25
Environmental Studies
03/19/2013

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Term
INFLUENT
Definition
WATER OR WASTEWATER FLOWING INTO A TANK OR FACILITY
Term
EFFLUENT
Definition
wATER OR WASTEWATER FLOWING OUT OF A TANK OR LEAVING A FACILITY
Term
RAW
Definition
UNTREATED SEWAGE OR WATER IS REFERRED TO AS RAW.
Term
MIXED LIQUOR
Definition
THE MIXTURE OF RAW SEWAGE AND ACTIVATED SLUDGE IN AN AERATION BASIN RESULTS IN A LIQUID REFERRED TO AS MIXED LIQUOR.
Term
MLSS
Definition
MIXED LIQUOR SUSPENDED SOLIDS - THE TOTAL SUSPENDED SOLIDS (NON DISSOLVED) CONCENTRATION OF THE MIXED LIQUOR IN THE AERATION BASIN.
Term
APPLIED SOLIDS
Definition
THE CONCENTRATION OF SUSPENDED SOLIDS BEING ADDED TO A CLARIFIER OR TANK.
Term
TSS
Definition
TOTAL SUSPENDED SOLIDS - THE CONCENTRATION OF SUSPENDED ( NON DISSOLVED) SOLIDS IN WATER OR SEWAGE. EITHER IN THE INFLUENT OR EFFLUENT.
Term
RAS
Definition
RETURN ACTIVATED SOLIDS - THE SOLIDS THAT ARE RETURNED TO THE AERATION TANK FROM THE SECONDARY CLARIFIERS IN THE ACTIVATED SLUDGE PROCESS.
Term
WAS
Definition
WASTE ACTIVATED SOLIDS - THE SOLIDS FROM EITHER THE PRIMARY OR SECONDARY CLARIFIERS THAT IS SENT TO SOLIDS DIGESTION AND REMOVED FROM THE PROCESS.
Term
CBOD5
Definition

CARBONACEOUS BIOLOGICAL OXYGEN DEMAND -

This is a measure of the ORGANIC strength of the wastewater. The test takes five days to measure the oxygen depletion of different dillution strengths. The comparison of influent and effluent CBOD5 results is one of the ways the effectivness of a treatment system is measured.

Term
MLVSS
Definition

MLVSS= MIXED LIQUOR VOLATILE SUSPENDED SOLIDS

The MLVSS is the amonut of organics in the MLSS, it is generally 75 to 85 percent and can be also called Percent Volatiles, or Volatiles are **%.

Term
Aerobic
Definition

Requirinig air or oxygen.

The Activated Sludge process is an example of an aerobic process.

Term
Anaerobic 
Definition

A process that takes place in the absence of free air or oxygen.

bacteria in an anaerobic zone get their oxygen from breaking down chemical compounds containing oxygen, such as Sulfates SO2.

Term
Prelimanary Treatment
Definition
Prelimanary Treatment refers to bar screens, and grit removal ahead of Primary Settling or Aeration.
Term
Sedimentation 
Definition
Sedimetation is considered a Primary Treatment.
Term
Pathogenic
Definition
Disease causing organisms are referred to as pathogenic orgamisms.
Term
Absorption
Definition

The taking in or soaking up of one substance into the body of another by molecular or chemical action.

Tree roots absorb nutrients in the soil.

Term
Activated Sludge
Definition

Sludge particles produced in raw or settled wastewater(primary effluent) by the growth of organisms ( including zoogleal bacteria) in aeration tanks in the pressence of dissolved oxygen.

Activated means the particals are teaming with bacteria, and it differs from primary sludge from primary settling basins.

Term
Adsorption
Definition
The gathering of gas, liquid, or dissolved substance on the surface or interface zone of another material.
Term
Aliquot
Definition

A representative portion of a sample.

Often an equally divided portion of a sample.

Term
Ambient Temperature
Definition
The temperature of the surroundings.
Term
Chlorine Demand, mg/L
Definition

Chlorine demand is the the difference in the  amount of chlorine added to the water or wastewater and the amount of residual chlorine remaining in the water or wastewater after a given contact time.

To find the chlorine demand you use the following equation.

Chlorine Demand, mg/L =

Chlorine Dosage, mg/L -Chlorine Residual, mg/L

Term
Chlorine Dosage, mg/L
Definition

Chlorine dosage is the total amount of chlorine applied to the water or wastewater for disinfection.

To find the dosage we add the demand and the residual.

 Chlorine Dosage, mg/L =

Chlorine Demand, mg/L + Chlorine Residual, mg/L

Term
Chlorine Residual, mg/L
Definition
Chlorine residual is the amonut of chlorine present in the water after the chlorine demand is met. The concentration is expressed in terms of total chlorine residual which includes both combined or chemically bound chlorine residualsand free chlorine residuals.