||Metals such as
copper, zinc, cadmium, chromium and lead. In wastewater treatment they are
usually concentrated in the sludge.
||Faeces and urine.
refers to a dry toilet where the solids are combusted. Used usually in isolated
area (e.g. permanent snow).
||Combustion of sludge.
Usually in a multiple hearth or fluidised bed furnace. It is relatively costly
and may produce air pollution.
|Infiltration trench (stormwater)
||A trench into which
stormwater run-off is directed and is allowed to infiltrate to the groundwater.
See also Chamber soakway.
|Integrated waste management
||Integration of the
management of solid waste, wastewater and stromwater to achieve protection of
public health and the environment. The integration can also be seen in a wider
context with hygiene promotion, community consultation and participation and
matters associated with the above.
||Lagoons or ponds are
natural or engineered excavations in the ground and used to treat wastewater
and stormwater. Settling of solids and degradation of organic materials by
micro-organisms take place in the lagoons. They are therefore also called
stabilisation lagoons or waste stabilisation lagoons.
||A landfill is usually
an excavation in the ground where waste is buried, and landfilling refers to
the method of waste disposal by burying the waste in the ground.
|Leach pit or drain
||Pit or drain into
which the overflow from a septic tank is directed. Water leaches (infiltrates)
into the ground. The soil surrounding the pit or drain must be permeable and
not close to the water table.
refers to the addition of lime (calcium oxide) to waste (e.g. sludge). In this
way the pH of the sludge is increased usually to above 11 and hence bacteria
(including pathogens) are killed.
||The conditions of
composting where the temperature initially rises, but still below 40 oC.
uses a membrane that passes water and some salts. In this way the water passing
through (the permeate) contains less salt and bacteria. A high pressure is
required to push the water through the membrane.
wastewater treatment include bacteria, fungi, protozoa and crustaceans which
convert organic wastes to more stable less polluting substances
||See Biogeochemical cycles
in nature which remove pollutants or convert them or render them less harmful
to the environment. Examples are the removal of suspended solids in quiescent
stretches of a river and removal of organic wastes through consumption by
naturally occurring bacteria.
||Night soil refers to
human excreta that is stored in buckets and collected nightly for reuse,
treatment or disposal.
ammonium in wastewater to nitrate. This process is carried out by nitrifiers
under aerobic conditions.
||Bacteria carrying out
the nitrification process.
||An essential and
important plant nutrient. It occurs in several forms: organic nitrogen,
ammonia, nitrite and nitrate.
||Nutrients refer to
the elements that are required by plants and animals, although nitrogen and
phosphorus are generally the major nutrients of concern in wastewater. See
Eutrophication and Environmentally sensitive zones.
systems that are located where the waste is produced. See Centralised systems.
||Latrine located above
water (river or coastal water) and human excreta drops directly into the water.
||Overland flow refers
to the treatment of wastewater by passing it through land. Purification of the
wastewater takes place as it flows through the soil. Grasses growing on the
soil transpire part of the water and take up nutrients.
||Channel in the form
of a ring for the treatment of wastewater. The wastewater is moved along the
channel to assist with aeration. Treatment processes are similar to what takes
place in a lagoon.
protozoa and helminths which cause illnesses.
||pH indicates the
degree of acidity or alkalinity of water. Neutral pH is seven, whereas a value
below 7 indicates acidic conditions and above 7 alkaline conditions. Living
organisms usually tolerate a pH of between 6 and 9.
||Pit privy or latrine
is a latrine built on top of a dug pit. Human excreta is deposited into the
pit. When the pit is full the content is dug up, or the latrine relocated and
the pit covered with soil.
||Phosphorus is an essential
and important plant nutrient. It occurs as organic phosphorus and phosphate.
|Pour flush toilet
||A pour flush toilet
has a water seal and is flushed by pouring 2 to 3 L of water into the pan.
||Sludge produced from
primary treatment of wastewater.
||The treatment of
wastewater by screening and sedimentation to remove solids.
||Heating of sludge to
a very high temperature in the absence of oxygen or in the presence of
controlled small amounts of oxygen. Under these conditions the sludge is
converted into water, gas, oil and char.
|Rapid rate land application
||See Soil Aquifer Treatment
||Water from rainfall
that flows over surfaces.
||Basin or pond used to
store stormwater run-off. Flooding potential is therefore reduced. Settling of
solids and infiltration of water into the ground occur during retention.
|Return activated sludge
||Activated sludge that
is returned to the aeration tank of an activated sludge process to assist with
treatment of wastewater. See Activated Sludge.
|Rotating Biological Contactor (RBC)
||A rotating biological
contactor is used to treat wastewater and consists of rotating disks that are
partly immersed in the wastewater. In this way the wastewater is entrained in
the rotating disks and aerated, and aerobic bacteria consume organic wastes.
||See Rainfall run-off.
||The operation of
passing water through a bed of sand to remove suspended solids from the water.
refers to the treatment of wastewater after primary treatment. Aeration is
introduced to supply oxygen to the bacteria consuming the organic materials in
the wastewater. See Activated sludge and Trickling Filter.
||The removal of
suspended solids by slowing the velocity of flow of the wastewater. In this way
solids settle to the bottom of the sedimentation tank or pond.
||The sludge that
accumulates in a septic tank.
||On-site tank for the storage
of solids in wastewater. Regular emptying of the accumulated solids is required
so that it can function properly. See Septage, Leach drain/ pit and STEP.
|Septic tank effluent pumping (STEP)
||STEP refers to the
conveyance of the overflow from septic tanks by pumping it to a central
collection point. Pumping overcomes the need to have large diameter pipes which
rely on gravity flow.
|Sequencing batch reactors (SBR)
||An Activated Sludge
Process that is operated batchwise (rather than with a continuous flow of
wastewater). Each step of the Activated Sludge Process is done in sequence. Two
tanks in parallel are required to deal with continuous flow of wastewater.
||Sewerage that conveys
wastewater that has undergone settling to remove suspended solids.
||Sewage is wastewater
produced from human activities in a household, and consists of human excreta,
kitchen waste, bathing water and washing water. See Sewerage.
||Sewerage refers to
the pipes and drains which convey sewage. A sewerage system includes the pumps
that may be required if gradient for gravity flow is not sufficient. Sewerage
usually also conveys stormwater and industrial wastewater. See Sewage.
wastewater from a sewer pipe for reuse purposes. Treatment of the wastewater is
required to meet the requirement of reuse.
||See Simplified Sewerage
sewerage pipes are laid relatively shallow in the ground when traffic above is
light. Design horizon is shorter compared to conventional sewerage. As a result
pipes are smaller in size and are laid shallower compared to conventional
sewerage. Costs are correspondingly lower.
|Sludge (sewage sludge)
||Sludge is the solids
that are produced from human excreta or from the treatment of wastewater.
||Solids refer to
materials which are in solid form. They are generally in the solid phase, but
may dissolve in water (e.g. salts and sugar). Hence the reference to Dissolved
Solids or Total Dissolved Solids. See Suspended Solids.
|Solids free sewerage
||See Settled Sewerage
to the decomposition of organic materials by micro-organisms. The organic
materials are converted into more stable less biodegradable materials and
therefore do not produce as much odour and less attractive to insects.
||Stormwater is water
which results from storm and rainfall generally. See run-off.
|Suspended solids (SS)
||Suspended solids are
solid particulate matter contained in water. They are generally removed by
settling, but for light particulates by floating. See Dissolved Air Flotation.
|Suspended growth system
||A suspended growth
system retains micro-organisms in a wastewater treatment system in the form of
flocs suspended in the wastewater. An activated sludge process is an example of
a suspended growth system. See Attached Growth System.
||Long shallow channels
which intercept stormwater run-off (e.g. from a Filter strip). They act to
store the water temporarily and allow it to infiltrate to the ground.
||The treatment of
wastewater beyond secondary treatment, but may be used to refer specifically to
the removal the nutrients nitrogen and phosphorus. See Secondary Treatment.
||The conditions of
composting where the temperature is above 45 oC.
Heat is generated from the activities of
micro-organsims consuming the organic materials in the compost. Oxygen
requirement is highest in this active period. Can be taken advantage for
compost sterilisation purposes.
||The process of
removal of water/moisture from the sludge. This is usually done by allowing the
solids in the sludge to settle and decanting the excess water.
urination and defecation including the housing required for such facilities.
|Total Dissolved Solids (TDS)
|Total Suspended Solids (TSS)
||See Suspended Solids
||A trickling filter is
an example of an Attached Growth System. Wastewater is allowed to flow through
the filter bed. Organic materials in the wastewater are consumed by the
micro-organisms attached to the surfaces of the filter bed. See Attached Growth
disinfection utilised ultraviolet radiation (e.g. from the sun) to achieve
disinfection. See Disinfection.
|Upflow Anaerobic Sludge Blanket (UASB)
||An anaerobic process
for the treatment of wastewater (usually with a high BOD). Wastewater is passed
through a tank from below through a bed of sludge containing the micro-organism
which consume the organic wastes.
||A latrine where human
excreta is stored in a vault, which is emptied regularly of the sludge.
|Waste management hierarchy
||A waste management
method which considers prevention of waste as the highest priority, followed by
waste minimisation, recycling, reuse and treatment prior to disposal. The
latter is considered to be of the lowest priority.
||Wastewater refers to
water that has been used in households and also in other activities, e.g.
industry producing industrial wastewater. See Sewage.
|Waste stabilisation pond
||Water bodies that are
generally shallow and may not have permanent water. Artificial wetlands
(constructed wetlands) are wetlands that have been created to receive
stormwater, or treat wastewater.
|Waste Activated Sludge (WAS)
||Activated sludge that
is in excess of the requirement of an activated sludge process and is wasted
from the process. See Activated Sludge and Activated Sludge Process.
||The natural cycling
of water in the environment, which include evaporation of water from the
oceans, seas, rivers and lakes, the condensation of the evaporated moisture as
rainfall, the resulting rainfall run-off, water infiltration to the
groundwater, uptake by plants, and water flowing in rivers to the seas and