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Technical Resources

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Symbols and Acronyms

laboratory procedures   Modes of conducting laboratory processes and analytical tests consistent with validated standard testing techniques.

lag growth phase  The initial period following bacterial introduction during which the population grows slowly as the bacteria acclimates to the new environment.

lagoon  Any large holding or detention pond, usually with earthen dikes, used to contain wastewater while sedimentation and biological oxidation occur. See also anaerobic lagoon.

laminar flow  The flow of a viscous fluid in which particles of the fluid move in parallel layers, each of which has a constant velocity but is in motion relative to its neighboring layers. Also called streamline flow, viscous flow.

land application  The recycling, treatment, or disposal of wastewater or wastewater solids to the land under controlled conditions.

landfill  The disposal of solid wastes or sludges by placing on land, compacting, and covering with a thin layer of soil.

leachate  Liquid that has percolated through solid waste or other permeable material and extracted soluble dissolved or suspended materials from it.

leakage  Uncontrolled loss of water from artificial structures as a result of hydrostatic pressure.

leakage detector  A device or appliance, the principle of which is the audibility of water flowing through a leak. Most of these devices are marketed under descriptive trade names.

lethal concentration  The concentration of a test material that causes death of a specified percentage of a population, usually expressed as the median or 50% level (L50).

lift station  A structure that contains pumps and appurtenant piping, valves, and other mechanical and electrical equipment for pumping water, wastewater, or other liquid. Also called a pumping station.

lighting panel  An enclosure carrying numerous low-voltage breakers, switches, and fuses servings lights or receptacles in an area.

lime  Any of a family of chemicals consisting essentially of calcium hydroxide made from limestone (calcite) composed almost wholly of calcium carbonate or a mixture of calcium and magnesium carbonate; used to increase pH to promote precipitation reactions or for lime stabilization to kill parthenogenic organisms.

lining  A protective covering over all or a portion of the perimeter of a conduit or reservoir intended to prevent seepage losses, withstand pressure, or resist erosion. In the case of conduits, lining is also sometimes installed to reduce friction losses.

lipids  A group of organic compounds that make up the fats and other esters with analogous properties.

liquefaction  (1) Act or process of liquefying or of rendering or becoming liquid; reduction to a liquid state. (2) Act or process of converting a solid or a gas to a liquid by changes in temperature or pressure, or the changing of the organic matter in wastewater from a solid to a soluble state.

liquid  A substance that flows freely; characterized by free movement of the constituent molecules among themselves, but without the tendency to separate from one another, which is characteristic of gases. Liquid and fluid are often used synonymously, but fluid has the broader significance of including both liquids and gases.

liquid chlorine  Elemental chlorine converted to a liquid state by compression and refrigeration of the dry, purified gas. Liquid chlorine is shipped under pressure in steel containers.

load  The amount of electrical power required at any specified point or points on an electrical system. Load originates at the power-consuming equipment (see demand).

load center  A point at which the load of a given area is assumed to be concentrated.

load diversity  The difference between the sum of the individual maximum demands of two or more individual loads and the coincident maximum demand of those loads.

load factor  The ratio of the average load in kilowatts supplied during a designated period to the peak or maximum load in kilowatts occurring in that period. Load factor, in percent, may be derived by multiplying the kilowatt-hours used in the period by 100 and then dividing by the product of the maximum demand in kilowatts and the number of hours in the period.

log growth phase  Initial stage of bacterial growth, during which there is an ample food supply, causing bacteria to grow at their maximum rate.

loss of head  (1) The decrease in energy between two points resulting from friction, bend, obstruction, expansion, or any other cause. It does not include changes in the elevation of the hydraulic grade unless the hydraulic and energy grades parallel each other. (2) The difference between the total heads at two points in a hydraulic system.

low-rate filter  A trickling filter designed to receive a small load of BOD per unit volume of filtering material and to have a low dosage rate per unit of surface area, usually 2 to 5 mgd/ac (2.2 3 1025 to 5.4 3 1025 m3/m2·s) generally without recirculation. The organic loading (BOD) rate is usually in the range of 5 to 25 lb/1 000 cu ft (80 to 400 g/m3). Also called a standard rate filter.