Home
Chemical Treatment Biological
Treatment Engineering
Wastewater
Costs Glossary
Septic Tank Aid
Search Site
A to B
C to E
F to M S
to W
Glossary N O
P R
Nitrate sensitive area
a defined area, designated by statutory order, within which measures are taken
to minimise the leaching of nitrates from agriculture into groundwater
Nitrate (NO3-)
the most oxidised form of nitrogen; formed from the oxidation of ammonia by
aerobic bacteria; present in fertiliser; the preferred form of nitrogen in
discharges to rivers
Nitrifying bacteria
aerobic bacteria that convert ammonia (NH3) into nitrate
(NO3-)
Oil interceptor
used to intercept rainwater or spillages contaminated with oil and to retain the
liquid for subsequent separation
Oocysts
persistent reproductive spores of Cryptosporidium; excreted by infected animals
and spread in unfiltered water; highly resistant to chlorine but destroyed by
heat or ozone
Organic
substances such as proteins, sugars, wood and plastics with molecular structures
containing carbon-hydrogen (C-H) bonds
Organochlorines
organic compounds containing chlorine, including PCBs, DDT and lindane;
accumulate in fatty tissue and may be toxic
Oxidation
the chemical or biochemical change that occurs when a substance combines with
oxygen, for example during combustion and respiration; the release of carbon
dioxide and energy from organic compounds
Oxygen system
injects oxygen into liquid effluent; increases aerobic microbial activity and
the rate of removal of BOD, COD and ammoniacal nitrogen
Ozone (O3)
a naturally occurring unstable form of oxygen; attenuates harmful ultraviolet
light in the stratosphere; a pollutant in the atmosphere at ground level; a
powerful oxidising agent and disinfectant
Ozoniser
equipment that generates ozone from oxygen or air by electrical discharge; used
in the treatment and disinfection of water and wastewater
Packed tower scrubber
cleans gases with a scrubbing liquor as they pass through inert media; removes
soluble and noxious gases and mist droplets larger than 5 µm
PCBs
polychlorinated biphenyls; very persistent, toxic substances, stored in fatty
tissue; previously widely used as fire-resistant dielectric fluids in
transformers and capacitors; now prohibited
Pentachlorophenol (PCP)
a powerful biocide, used to preserve cotton and wood; toxic and persistent;
release to the environment now heavily restricted
pH
a logarithmic scale (0-14) that reflects acidity or alkalinity; pH 7 indicates
neutrality; acidic solutions have lower pH values; alkaline solutions have
higher values
Plate scrubbers
remove dust, noxious gases and odours from gaseous emissions by passing them
through perforated plates flooded with scrubbing liquor
Pollutant
a chemical or substance that causes harm in the environment
Polychlorinated biphenyls
see PCBs
Polyelectrolytes
natural or synthetic water-soluble macromolecules that assist in the
flocculation of dispersed solids
Potable water
water of a quality suitable for drinking
Reed Bed
Managed wetlands used for the treatment of wastewaters; commonly planted with
phragmites australis and other species to facilitate BOD removal below
soil surface
Red List
a list used in the UK that identifies the most persistent and toxic substances
so that their discharge to water and accumulation in living organisms may be
strictly controlled
Reverse osmosis
a high pressure filtration system that uses selectively permeable membranes with
extremely small pores to separate ions and particles
Rotary scrubber
a device that separates particulate contamination from a gas stream by impaction
onto a wet rotor or into a fine spray of scrubbing liquor
Rotating biological contactor
an aerobic treatment system that rotates plastic media with fixed microbial film
alternately through liquid effluent and air to reduce the BOD value
