Sewage includes domestic, municipal, or industrial Liquid Waste Product s disposed of via a Pipe or similar structure. The physical infrastructure, including pipes, Pump s, screens, channels etc. used to convey sewage from its origin to the point of eventual treatment or disposal is termed Sewerage , a term often mistakenly used to refer to sewage.
Composition of sewage
Sewage is a variable liquid mixture comprising material from some or all of the following sources:
- Human waste ( Faeces , Paper , wipes and Urine + other bodily fluids) also known as Black Water
- Washing water (personal, clothes, floors etc.) also known as Grey Water
- Rainfall collected on roofs, yards, hard-standing etc. (traces of Oil s and Fuel but generally clean)
- Ground water infiltrated into sewage pipes
- Surplus manufactured liquids from domestic sources ( drinks, cooking oil, Pesticide s, Lubricating Oil , Paint , cleaning liquids etc.)
- General urban rainfall run-off from Road s, car-parks, roofs, side-walks or pavements (contains oils, animal faeces, Litter , fuel residues, Rubber residues, metals from vehicle exhausts etc)
- Industrial cooling waters
- Industrial process waters
- Sea water ingress
- Direct ingress of river water
- Direct ingress of man-made liquids (illegal disposal of pesticides, used oils etc.)
The composition of each sewage stream varies widely, but sewage derived from a large city can be expected to contain (the examples given here represent only a small proportion of the range of materials actually encountered):
- Water ( > 95%) and is often added during Flushing as a means to carry the waste down a Gravity Line
- Non pathogenic Bacteria (> 100,000 / ml)
- Pathogens - (Bacteria, Virus es, Prion s, Parasitic Worms ).
- Organic particles ( Faeces , Hair , food, Vomitus , paper fibres, plant material, Humus etc.)
- Soluble organic material ( Urea , fruit sugars, soluble Protein s, Drugs , pharmaceuticals etc.)
- Inorganic particles ( sand, grit, metal particles, ceramics etc)
- Soluble inorganic material ( Ammonia , road-salt, sea-salt, Cyanide , Hydrogen Sulphide , thiocyanates, thiosulphates)
- Animals ( Protozoa , Insect s, Arthropod s, small Fish , etc.)
- Macro-solids ( Sanitary Towel s, Nappies/ Diapers , Condom s, Needle s, children's toys, body parts, etc.)
- Gases (hydrogen sulphide, Carbon Dioxide , Methane )
- Emulsions ( oils in emulsion, Paint s, Adhesive s, Mayonnaise , hair colourants)
- Toxins (pesticides, Poison s, Herbicide s )
Sewage disposal
(See also Sewage Treatment )
In some urban areas, sewage is carried separately in Sanitary Sewer s while runoff from streets is carried in Storm Drain s. Access to either of these is typically through a Manhole .
Sewage may drain directly into major Watershed s with minimal or no treatment. When untreated, sewage can have serious impacts on the quality of an environment and on the health of people. Pathogen s can cause a variety of illnesses. Some chemicals pose risks even at very low concentrations and can remain a threat for long periods of time because of Bioaccumulation in animal or human tissue.
References
- Tchobanoglous, G, Burton, F L, & Stensel, H D (2003). ''Wastewater Engineering (Treatment Disposal Reuse) / Metcalf & Eddy, Inc - 4th ed.'' McGraw-Hill, USA
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