Activated carbon
Adsorptive particles or granules of carbon usually obtained by heating carbon (such as wood). These particles or granules have a high capacity to selectively remove certain trace and soluble materials from water.
Alkalinity
The acid-neutralizing capacity of water or wastewater. Alkalinity in wastewater results from the presence of carbonate, bicarbonate and hydroxide. The quantitative determination of alkalinity involves neutralizing the bases found in water with standardized strong acid.
Ammonia
Ammonia is a colorless gas with a very distinct odor. This odor is familiar to many people because ammonia is used in smelling salts, many household and industrial cleaners, and window-cleaning products.
Ammonia occurs naturally and is produced by human activity, e.g. bacteria found in the intestines can produce ammonia. It is an important source of nitrogen which is needed by plants and animals. Ammonia is applied directly into soil on farm fields, and is used to make fertilizers for farm crops, lawns, and plants.
Ammonia gas can be dissolved in water. This kind of ammonia is called liquid ammonia or aqueous ammonia. Once exposed to open air, liquid ammonia quickly turns into a gas.
Ammonical Nitrogen (NH3-N)
A measure for the amount of Ammonia.
Biochemical oxygen demand (BOD)
A chemical procedure for determining how fast biological organisms use up oxygen in a body of water. It is usually performed over a 5-day period at 20° Celsius. BOD is not an accurate quantitative test, although it could be considered as an indication of the quality of a water source. BOD is used as a gauge of the effectiveness of wastewater treatment plants.
Chemical Oxygen Demand (COD)
A test commonly used to indirectly measure the amount of organic compounds in water.
Chloramines
Compounds formed by the reaction of hypochlorous acid (or aqueous chlorine) with ammonia.
Chloride (Cl-)
Chloride, in the form of Cl-, is one of the major inorganic ions in water and wastewater. The salty taste produced by chloride concentrations is variable and depends on the chemical composition of the water. Some waters containing 250 mg Cl-/L may have a detectable salty taste if the cation present is sodium. But when the predominant cations are calcium and magnesium, the salty taste may be absent in water containing as much as 1,000 mg/L.
Coagulation
The clumping together of very fine particles into larger particles (floc) caused by the use of chemicals (coagulants). The chemicals neutralize the electrical charges of the fine particles, allowing them to come closer and form larger clumps. This clumping together makes it easier to separate the solids from the water, by settling, skimming, draining or filtering.
Coagulants
Chemicals that cause very fine particles to clump (floc) together into larger particles. This makes it easier to separate the solids from the water by settling, skimming, draining or filtering.
Coliform Bacteria
A group of bacteria commonly found in the intestines of animals and humans beings. Coliform count is used as a hygiene indicator. The test is performed via membrane filtration, and filters placed onto selective agar. After incubation, plates are counted and suspect colonies confirmed with confirmation tests (lactose fermentation)
Colloids
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 the water have negative electrical charge, they tend to repel each other. This repulsion prevents the particles from clumping together, becoming heavier, and settling out.
Conductivity
A measure of the ability of an aqueous solution to carry an electric current. This phenomenon is not only shown in metals such as iron but also in water. The conductivity value of water depends on the presence of ions, total concentration, mobility of ions and valence, and also the water temperature during measurement. Ion concentration and temperature have a proportional effect on water conductivity. Solutions of most inorganic compounds are relatively good conductors, whereas molecules of organic compounds that do not dissociate in aqueous solution show poor conductivity.
Desalination
The removal of dissolved salts (such as sodium chloride, NaCl) from water by specific water treatment processes.
Disinfection
The process designed to kill or inactivate most microorganisms in water, including essentially all pathogenic (disease-causing) bacteria. There are several ways to disinfect, with chlorination being the most frequently used in water treatment.
Effluent
Liquid waste, especially chemicals produced by factories or sewage.
Flocculate
The gathering together of fine particles after coagulation to form larger particles by a process of gentle mixing.
Fluoride
Fluoride may occur naturally in water or it may be added in controlled amount. A fluoride concentration of approximately 0.5 mg/L in drinking water effectively reduces dental caries, especially in children, without harmful effects on human health. Toothpastes are normally fortified with fluoride to prevent tooth decay. However, too much fluoride causes adverse effects on teeth.
Free chlorine
That portion of the total available residual chlorine composed of dissolved chlorine gas (Cl2), hypochlorous acid (HOCl), and/or hypochlorite ion (OCl-) remaining in water after chlorination. This does not include chlorine that has combined with ammonia, nitrogen, or other compounds.
Galvanised iron
A coating of zinc on iron or steel to protect the iron from corrosion.
Heterotrophic Plate Count
This measures the general bacteria population per milliliter of water. The test is performed via pour plate method where 1 ml of water sample and/or its dilution is plated and molten agar added. The plates are incubated at 35 deg C for 48 hours before colonies are counted.
Hydrated lime
Limestone that has been “burned” and treated with water under controlled conditions until the calcium oxide portion has been converted to calcium hydroxide, Ca(OH)2. Hydrated lime is quicklime combined with water. CaO + H2O = Ca(OH)2.
Membranes
Thin barriers or films of material with a large number of small pores of a predetermined size. Membranes allow solvent and other smaller molecules, ions or particles to pass through the pores while preventing the passage of other materials.
NEWater
Treated used water that has undergone stringent purification and treatment process using advanced dual-membrane (microfiltration/ultrafiltration and reverse osmosis) and ultraviolet technologies.
Nitrate
Nitrate is part of the nitrogen cycle and is used mainly in inorganic fertilizers. Sodium nitrite is used as a food preservative, especially in cured meats. The nitrate concentration in groundwater and surface water is normally low but can reach high levels as a result of agricultural runoff, refuse dump runoff, or contamination by human or animal wastes.
Organic Matter
Organic matter in a reverse osmosis feed is customary expressed as the total organic carbon (TOC).
Ozone
Ozone (O3) is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic species O2. Ozone is a strong disinfectant.
pH
A term used to describe the hydrogen ion activity of a system. The pH scale ranges from 0-14. A solution with a pH below 7 is acidic, while a pH above 7 is basic (alkaline). A pH of 7 is neutral.
Polyelectrolyte
Often called a polymer, a polyelectrolyte is a high-molecular-weight (relatively heavy) substance having points of positive or negative electrical charges that is formed by either natural or manmade processes. Natural polyelectrolytes may be of biological origin or derived from starch products and cellulose derivatives. Manmade polyelectrolytes consist of simple substances that have been made into complex, high-molecular-weight substances. Used with other chemical coagulants to aid in binding small suspended particles to larger chemical flocs for their removal from water.
Raw water
Water in its natural state, prior to any treatment, usually the water entering the first treatment process of a water treatment plant.
Residual Chlorine
During water treatment, chlorine is added to destroy or deactivate disease-producing microorganisms. However, chlorination may produce an adverse taste and odor in the water. Chlorine applied to water in its molecular or hypochlorite form initially undergoes hydrolysis to form free chlorine consisting of aqueous molecular chlorine, hypochlorous acid and hypochlorite ion.
Salts
A chemical compound of a metal and an acid.
Sedimentation
A water treatment process in which solid particles settle out of the water being treated in a larger clarifier or sedimentation basin.
Silica
The common aqueous forms of silica are H4SiO4 and H3SiO4-. In the presence of magnesium, silica can form scale deposits in boilers and stream turbines. It is considered a nonessential trace element for most plants, but essential for most animals.
Sulphate
Sulphate is widely distributed in nature and may be present in natural waters in concentrations ranging from a few to several thousands mg/L. Mine drainage wastes may contribute large amounts of SO42- through pyrite oxidation.
Suspended matter
Matter that either floats on the surface or suspended in water, wastewater, or other liquids and which is largely removable by filtering.
Total Hardness
Water hardness is mainly contributed by calcium and magnesium ions. Originally, water hardness was understood to be a measure of the capacity to precipitate soap. Soap is precipitated chiefly by the calcium and magnesium ions. In conformity with current practice, Total Hardness is defined as the sum of the calcium and magnesium concentrations, both expressed as calcium carbonate, in mg/L. In households, high water hardness can cause scaling of heating elements, such as the heating coil in an electric kettle. The formation of scale is greatly increased with the rise of temperature; it reduces heat transfer during boiling and therefore causes more electricity to be consumed.
Total Organic Carbon (TOC)
A measure of the amount of organic materials suspended or dissolved in water. TOC is a quicker sampling method than measuring COD or BOD for determining the quality of the effluent.
Total Solids (TS)
A measure of the amount of material that is dissolved or suspended in a water sample, by weight. Total solids is determined by allowing a known volume to evaporate and then weighing the remaining residue. TS = TDS + TSS
Total Suspended Solids (TSS)
A measure of the solids found in water that can be removed by filtration.
Total Dissolved Solids (TDS)
An expression for the combined content of all inorganic and organic substances contained in a liquid or water which are present in a molecular, ionized or micro-granular suspended form that cannot be removed by filtration.
Total Trihalomethanes (THMs)
THM compounds can be found in chlorinated water samples. The formation of these compounds is a function of precursor concentration, contact time, chlorine dose and pH. Some of the common THMs are Chloroform, Bromoform, Bromodichloromethane and Dibromochloromethane.
Turbidity
A measure of the clarity of a solution often measured in Nephelometric Turbidity Units [NTU] caused by sediment or foreign particles stirred up or suspended in water. Highly turbid waters are muddy or cloudy. |