Water Treatment Terms…………….The Letter U

ULTRAFILTRATION (UF): is a type of membrane filtration that separates suspended solids and solutes of high molecular from a liquid and low molecular weight solutes. This separation process is used in industry processes, water treatment and research for purifying and concentrating macromolecular solutions.


ULTRAPURE WATER: Highly treated water that is deionized and mineral free with high resistivity and no organics; it is usually used in the semiconductor and pharmaceutical industries. Ultrapure water in NOT considered biologically pure (potable) or sterile.

ULTRAVIOLET (UV) LIGHT: Radiation (light) having a wavelength shorter than 3900 angstroms, the wavelengths of visible light, and longer than 100 angstroms, the wavelength of x-rays.

ULTRAVIOLET CHAMBER: The area where the water is irradiated with ultraviolet rays.

ULTRAVIOLET DEMAND: The amount of ultraviolet rays required to inactivate certain microorganisms.

ULTRAVIOLET DISINFECTION (UV): A disinfection method in which final wastewater effluent is exposed to ultraviolet light to kill pathogens and microorganisms.

ULTRAVIOLET DOSAGE: The amount of disinfectant ultraviolet rays delivered to the organisms in the water being disinfected. Dosage is a combination of UV intensity times the contact time and is measured in watt-seconds per square centimetre.

UNIFORM FLOW: A flow in which the feet per second velocity rates and directions are the same from point to point along the conduit.

UP FLOW: A pattern of water flow in which a solution (water or regenerant usually) enters at the bottom of the vessel or column and flows out at the top of the vessel or column during any phase of the treatment unit’s operating cycle.

USER: The product water consumer.