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Glossary F H  L  M

Ferric chloride or sulphate
iron-containing substances used to coagulate and flocculate in effluent treatment processes

Filter press
a device that dewaters sludge by compressing it between membranes or cloth-lined plates to produce a cake

Fine bubble diffuser
an aeration device in which air is blown through a porous ceramic or synthetic membrane to create small bubbles in a liquid effluent

the agglomeration of coagulated particles to form a floc which can settle or float; may be assisted by biological, chemical or mechanical means

Fluidised bed
a body of solid particles through which gas or liquid is blown or pumped upwards causing separation and movement; a means of increasing reaction rates

Fluidised bed scrubber
a device that removes pollutant particles or trace gases from a gas stream, in which plastic spheres are wetted by a scrubbing liquor and fluidised by the contaminated gas stream

FOG (Fats Oils and Grease) wastewater components from food preparation, animal or vegetable processing; largely insoluble in water, high COD and likely to float 

solid particles smaller than 1m in a gaseous emission

Halogenated hydrocarbons
organic compounds containing carbon, hydrogen and halogen atoms (fluorine, chlorine, bromine and iodine); implicated in stratospheric ozone loss

Hazardous waste
waste that originates from a specified waste stream or has hazardous properties or contains hazardous substances as defined in the Hazardous Waste Directive

Heavy metals
certain metals, used industrially and harmful to living organisms, for which discharge and emission standards are set; including cadmium, chromium, copper, lead, mercury, nickel, zinc

High performance filter
a device that separates particles 2-500 m in size from relatively clean liquid streams

a device that separates sand, silt and suspended solid particles from a liquid using centrifugal forces generated by the liquid flow

Hydrogen sulphide (H2S)
a foul smelling gas, a product of the reduction of organic sulphur by anaerobic organisms

the controlled burning of municipal, clinical and chemical waste material and sewage sludge, commonly in two stages, to produce minimum amounts of gas and ash

substances such as sand, clay and metals whose molecular structures do not contain carbon-hydrogen (C-H) bonds except as carbonates and similar

liquid that has percolated through a solid mass; soil leachate may be high in nitrate; landfill leachate may be high in BOD, ammonia, salinity and toxic substances

Legionella pneumophila
a water-borne pathogenic bacterium which causes Legionnaires' Disease; may be present in cooling systems and spread by droplets; controlled by chlorination, ozone, silver-copper, ultraviolet light

stones, pebbles or plastic that provides a substrate for the growth of a film of microorganisms in wastewater treatment; plastic, ceramic or metal shapes or surfaces that improve gas-liquid contact in gas scrubbing

Methane (CH4)
highly calorific gas; 60 % of biogas; produced during anaerobic biological processes; may contribute to global warming

the use of microporous filters operating under pressure to remove particles or microorganisms of 01-50 m size from process and effluent liquids

microscopic living creatures; bacteria, protozoa, fungi and algae

Microwave disinfection unit
equipment that shreds clinical waste and disinfects it with steam and microwave radiation

Mist eliminator
unit that separates small droplets of liquid (mist) from gas streams by impingement on a mesh or plate surface; part of a wet scrubber

very small droplets of liquid suspended in a gas

2006 Oasis Environmental Ltd