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A Cheat Sheet | Wastewater Definitions

What does that wastewater acronym stand for? And actually mean? We’ve rounded up wastewater definitions for 30+ of the industry’s most common terms.

By Pat Kneip, P.E.

There are dozens of wastewater terms that cross nearly every industry. Plus, each one is often referred to by a two or three letter abbreviation, so it’s easy to find yourself thinking, “What does that stand for again? And what does it mean?”

We’ve compiled some of the most common terminology along with brief wastewater definitions. This list spans everything from types of wastewater treatment to parameters and specific pollutants. Think of it as a quick cheat sheet for environmental health professionals.

Ag: Silver

A metal element regulated by wastewater discharge permits and common in metal finishing wastewater.

AS: Activated Sludge

A biological water treatment technology commonly used in municipal wastewater treatment systems. Sometimes private industry will harness this technique to reduce certain pollutants, such as BOD and COD (see definitions below), but usually only due to compliance concerns.

As: Arsenic

A heavy metal commonly regulated by wastewater discharge permits, but not commonly found in industrial wastewaters. Other heavy metals include: Cadmium (Cd), Chromium(Cr), Copper (Cu), Lead (Pb), Nickel (Ni), and Zinc (Zn).

 

BOD: Biochemical Oxygen on Demand

An indirect reading of the organic content present in wastewater. Specifically, it refers to the amount of oxygen consumed to biologically degrade the organic material. It’s very expensive to treat, typically requiring a biological treatment technology like activated sludge.

Cd: Cadmium

A heavy metal commonly regulated by wastewater discharge permits and typically found in the metal finishing industry.  Other heavy metals include: Arsenic (As), Chromium(Cr), Copper (Cu), Lead (Pb), Nickel (Ni), and Zinc (Zn).

CN: Cyanide

A toxic element often found in wastewater from metal finishing industries. It’s commonly regulated by wastewater permits.

COD: Chemical Oxygen Demand

An indirect reading of the organic content of wastewater. Specifically, it refers to the amount of oxygen that’s required to chemically degrade the organic material.

Cr: Chromium

A heavy metal commonly regulated by wastewater discharge permits and found in metals-related industries and products (including stainless steel). It is typically regulated in two forms: total chromium and hexavalent chromium. Other heavy metals include: Arsenic (As), Cadmium (Cd), Copper (Cu), Lead (Pb), Nickel (Ni), and Zinc (Zn).

 

Cu: Copper

A heavy metal commonly regulated by wastewater discharge permits. It is found in the metal finishing and electrical industries. Other heavy metals include: Arsenic (As), Cadmium (Cd), Chromium(Cr), Lead (Pb), Nickel (Ni), and Zinc (Zn).

 

DAF: Dissolved Air Flotation

A physical/chemical wastewater treatment technology that can be cost-effectively used by industry to remove FOG (fats, oils and grease), suspended solids, and some metals.

DO: Dissolved Oxygen

An indication of how much oxygen is present in water. If a facility discharges directly to a stream or river, it will usually have a permit limit related to dissolved oxygen.

FOG: Fats, Oils, & Grease

Food industry byproducts that can cause significant problems for sewer systems. This pollutant includes both animal/vegetable and petroleum sources and can be regulated separately by these fractions. It is important to know which fraction is regulated and what analytical method is being used to get accurate results.

GAC: Granular Activated Carbon

A material used to absorb organics from wastewater. This charcoal-like material can be used in filtration systems to remove solvent contamination.

 

GPD: Gallons Per Day

GPM: Gallons Per Minute

These terms refer to the amount of wastewater flow over a given time period. Most wastewater permits include daily flow limits, so facilities track the flow of treatment systems to stay within overall permit parameters.

LPD: Liters Per Day

LPM: Liters Per Minute

These terms refer to the amount of wastewater flow over a given time period. Most wastewater permits include daily flow limits, so facilities track the flow of treatment systems to stay within overall permit parameters.

MBR: Membrane Bio Reactor

A wastewater treatment technology that combines biological treatment with physical treatment involving membrane filtration. It’s used primarily to treat BOD, COD, and suspended solids to very low levels where effluent may be able to be reused or recycled.

Pb: Lead

A heavy metal commonly regulated by wastewater discharge permits. Other heavy metals include: Arsenic (As), Cadmium (Cd), Chromium(Cr), Copper (Cu), Nickel (Ni), and Zinc (Zn).

Ni: Nickel

A heavy metal commonly regulated by wastewater discharge permits. It can be found in metals-related industries and products, including stainless steel. Other heavy metals include: Arsenic (As), Cadmium (Cd), Chromium(Cr), Copper (Cu), Lead (Pb), and Zinc (Zn).

 

NTU: Nephelometric Turbidity Unit

The standard unit to measure turbidity or how cloudy water is. It’s used as a visual indicator for how well a wastewater treatment system is working.

O&M Plan: Operation and Maintenance Plan

This term refers to the operational procedures and maintenance plans for a wastewater treatment system.

ORP: Oxygen Reduction Potential

A measure that indicates the capacity of wastewater to gain or reduce electrons during a chemical reaction. It is used as a control parameter for treating hexavalent chromium wastewater in the metal finishing industry.

P&ID: Process and Instrumentation Diagram

An engineering drawing for a wastewater treatment system. It’s a schematic flow diagram that shows the relationship between different instrumentation and equipment.

pH: Potential Hydrogen

A measurement of how acidic or basic wastewater is on a scale of 0 to 14.

 

ppb: Parts Per Billion

A unit of concentration for pollutants in the wastewater. It’s the equivalent of one microgram in 1 liter (ug/l).

ppm: Parts Per Million

A unit of concentration for pollutants in the wastewater. It’s the equivalent of 1 milligram in 1 liter (mg/l).

POTW: Publicly Owned Treatment Work

A term to describe a city or municipal sewage treatment facility. Since most industries discharge wastewater to these facilities, they’re typically regulated by these POTWs.

PVC: Polyvinyl Chloride

The most common material used for wastewater piping. It is a type of plastic.

PSI: Pounds Per Square Inch

A measurement of pressure. It’s often used when discussing physical wastewater treatment technologies involving filtration, but is also used with pumps. Filtration system PSI can indicate when it’s time to backwash or change a filter.

RBC: Rotating Biological Contactor

A biological treatment technology most often used in city treatment systems to reduce BOD.

RO: Reverse Osmosis

A physical treatment technology based around the use of a membrane for filtration. It provides the greatest degree of filtration available and is very effective for filtering out small or even dissolved pollutants.  It is subsequently the most expensive type of filtration.

SBR: Sequencing Batch Reactors

A biological treatment technology based on the activated sludge process. It is sometimes used in small municipalities and at food processing facilities who discharge directly to streams or rivers.

TDS: Total Dissolved Solids

Total dissolved solids are inorganic molecules of metals, minerals or salts present in water at such a small size that you can’t see them. Because of their very small size, they can be difficult to remove with any technology other than fine membrane filtration technologies such as Reverse Osmosis (RO).

TKN: Total Kjeldahl Nitrogen

A pollutant found in domestic sewage that is typically a surcharge parameter for industries.

TOC: Total Organic Carbon

A direct measurement of how much organic matter is in wastewater.

TOMP: Toxic Organic Management Plan

A spill plan federally required for specific industries, including metal finishing. It outlines what specific toxic organic compounds are used and how they are disposed in a manner that prevents discharge to the sewer system.

TSS: Total Suspended Solids

Visible solids present in wastewater that can be filtered out through traditional physical treatment technologies. In the metal finishing industry, for example, FOG (fats, oils and grease) and dirt particles might make up part of the total suspended solids.

TTO: Total Toxic Organics

A wastewater parameter that refers to the entire amount of toxic organic compounds present.   EPA has developed a specific list of chemicals that are defined as toxic organic compounds.

UF: Ultrafiltration

A type of membrane filtration that’s similar to reverse osmosis, but not as restrictive. It will not remove the smallest dissolved solids from water (for example salt) unless they can be chemically treated first.

UV: Ultraviolet

In some industries, ultraviolet light is used to sterilize water treated wastewater prior to reuse or recycling. UV light keeps algae and other bacteria from growing in the recycled wastewater.

VOC: Volatile Organic Compounds

In wastewater, VOCs typically show up as cleaning solvents. These chemicals can kill the microbes in POTWs (publicly owned treatment work) if they are discharged in large quantities, so they are carefully regulated. They’re challenging to treat because they dissolve in water.

WTP: Water Treatment Facility

A city or municipal water treatment facility that’s treating water you drink or use in an industrial process.

WWTP: Wastewater Treatment Plant

A city, municipal or industrial facility that’s treating wastewater.

Zn: Zinc

A heavy metal commonly regulated by wastewater permits. It is widely present in all industries and can be difficult to treat to low levels through typical physical/chemical treatment technologies.  It is very important to determine the sources of zinc in process wastewater in order to adequately control discharge levels.  Other heavy metals include: Arsenic (As), Cadmium (Cd), Chromium(Cr), Copper (Cu), Lead (Pb), and Nickel (Ni).

By Patrick A. Kneip, P.E.