Water and Pollution Control Department

Glossary of Terms

Ammonia (NH3-N) - That portion of nitrogen in the form of ammonia which is determined by standard laboratory procedure for analysis of ammonia nitrogen, expressed as milligrams per liter. Ammonia is typically present in domestic wastewater in concentrations between 15 and 30 milligrams per liter. Ammonia is converted to nitrate in a biological treatment process, usually trickling filter or activated sludge processes.
Bacterial Analysis - Each month several samples are collected from various sites served by the Ames Water Plant. Among other parameters, the sample is tested for specific types of bacteria. When the analysis of a sample detects coliform bacteria, staff return to confirm the result by taking another sample not only at the original location but also at the next locations upstream and downstream. If the repeat analyses detect coliform bacteria from the original sample location and one of the neighboring locations, it becomes a confirmed positive result. To date, Ames has never had a confirmed positive result for coliform bacteria.
Carbon Dioxide - Carbon dioxide (CO2) is a gas naturally present in groundwater. It is removed in the first step of drinking water treatment to reduce the amount of lime required, then is later added back to help stop the softening reaction by lowering the pH of the water.
Carbonaceous Biochemical Oxygen Demand - A common method of determining the organic strength of a waste. The CBOD5 test measures the amount of oxygen that microorganisms consume over a five day period to break down a waste.
Chemical Oxygen Demand (COD) - The oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidant as determined by standard laboratory procedures for COD.
Chloramines - When chlorine is added to drinking water containing ammonia it forms chloramines. Chloramines are less powerful disinfectants, but they have the advantage of being much more stable than free chlorine. Ames uses chloramines to provide a residual disinfection protection in the drinking water distribution system.
Chlorine - Chlorine is the most common chemical used for disinfecting drinking water. Chlorine is used to destroy three categories of human enteric pathogens: bacteria, viruses, and amebic cysts.
Chlorine Residual - A practical requirement of a disinfectant for drinking water is that it provide a reasonable residual protection against possible recontamination before use. The disappearance of a chlorine residual is a warning that recontamination may have taken place.
Disinfection - Disinfection is the addition of chemicals (usually chlorine) to reduce the number of pathogenic organisms. Disinfection is not the same as sterilization. Disinfection does not completely sterilize the water. Other methods of disinfection include ozone and ultraviolet radiation.
Dissolved Oxygen (DO) - The concentration of oxygen dissolved in water. Dissolved oxygen is important for aerobic ("with air") biological treatment. An adequate DO concentration in a wastewater effluent is important for the aquatic life in the receiving stream or river.
Effluent - The flow leaving a treatment process. Often refers to the final treated wastewater that is discharged to a receiving stream or river.
Effluent Permit Limit- A numerical value that places a restriction on the quality or quantity of a discharge. Effluent permit limits are contained in either state- or federally-issued discharge permits.
Equalization - Wastewater does not flow into a wastewater treatment facility at a constant rate. Flow equalization is used to store excess wastewater when the flow rate exceeds the capacity of the treatment facility. When the flow drops to below the facilities capacity, the stored wastewater can be returned for treatment. When the excess flow exceeds the capacity of the storage basins, it must be diverted to the river. Fortunately, excess flows typically coincide with a heavy rainfall events, so the influent to the treatment facility is more dilute.
Fluoride - Fluoride is a natural component of water in many areas, and its presence in drinking water has been linked to lower dental cavity rates. For that reason, fluoride is often added to drinking water.
Hardness - Hardness is a term often used to characterize a water and is useful in softening calculations. Hardness may be expressed in milligrams per liter (mg/L) or parts per million (ppm) as calcium carbonate. Alternately, it is expressed as grains per gallon of hardness. To convert from grains per gallon to mg/L, multiply by 17.1. Total Hardness - Technically, it is the sum of all polyvalent cations. Practically, it is the amount of calcium and magnesium ions, which are the predominant minerals in natural waters. It is divided into carbonate and non carbonate hardness. Carbonate Hardness - Often called "temporary hardness" because heating the water will remove it. When the water is heated, the insoluble carbonates will precipitate and tend to form bottom deposits in water heaters. Non-Carbonate Hardness - Non-carbonate hardness is correspondingly called permanent hardness because it is not removed when the water is heated. It is much more expensive to remove non-carbonate hardness than carbonate hardness.
Hydrogen Sulfide - Hydrogen sulfide (H2S) gas is naturally present in groundwater. It produces a 'rotten-egg' odor, and is removed in the first treatment step for drinking water. Hydrogen sulfide occurs in wastewater that has had most of its oxygen consumed. It is highly corrosive to concrete structures.
Influent - The water entering a particular process. Typically refers to the raw, or untreated, wastewater entering a treatment facility.
Iron - Small amounts of iron frequently are present in groundwater because of the large amount of iron in the soil. The presence of iron in drinking water is considered objectionable because it imparts a brownish color to laundered goods and affects the taste of beverages such as tea and coffee.
Lime - Lime is the chemical used to remove the carbonate hardness from water. Most water plants, including Ames, buy quicklime (calcium oxide) which is converted to hydrated lime (calcium hydroxide) at the plant.
Maximum Weekly Average - The highest allowable seven-day average of daily discharges over a calendar week, calculated as the sum of all daily discharges measured during a calendar week divided by the number of daily discharges measured during that week.
Monthly Average - The highest allowable average of daily discharges over a calendar month, calculated as the sum of all daily discharges measured during a calendar month divided by the number of daily discharges measured during that month.
pH - pH is an expression of the hydrogen ion concentration. A neutral solution will have a pH of 7, an acidic solution will have a pH of less than 7; and a basic solution will have a pH of greater than 7.
Polyphosphate - Polyphosphate is added to drinking water to prevent the lime particles from building up on the filter media.
Total Kjeldahl Nitrogen (TKN) - That portion of nitrogen which is the sum of ammonia and organic nitrogen in the form of proteins or intermediate decomposition products as determined by standard laboratory procedures for Total Kjeldahl Nitrogen.
Total Suspended Solids (TSS) - Solids present in a water sample that are retained on the filter paper after filtering the sample. The solids that pass thru the filter are identified as Total Dissolved Solids (TDS).
Turbidity - Turbidity is the presence of suspended material such as clay, silt, and other particulate matter. It can be loosely described as the "cloudiness" of water. The unit of measure is a Nephlometric Turbidity Unit (NTU).
Volatile Suspended Solids (VSS) - The fraction of Total Suspended Solids (TSS) that can be burned off in a furnace. This seperates the TSS into organic and inorganic portions.
Whole Effluent Toxicity - A test method designed to identify discharges and receiving waters that contain toxic materials in toxic concentrations. A positive WET result means a statistical difference of mortality rates of the test species between a control and the effluent sample.
References:
	Davis, M. L. and Cornwell, D. A., Introduction to Environmental Engineering, Second Edition, McGraw-Hill, Inc., New York, NY, 1991.