WASTE WATER / SEWAGE- Waste water is polluted water which contains all harmful solid , liquid and gaseous substances ,that alters the physical ,chemical and biological properties of water.
1. On the basis of origin it can be domestic, industrial , precipitation and radioactive sewages.
2. On the basis of harmfulness it can be directly harmful sewage (As for instance it can causes several diseases) or indirectly harmful sewage (which can affect the water quality like deplet oxygen level)
3. On the basis of stability it can be degradable ,non degradable and stable.
MICROBIOLOGY OF SEWAGE
Sewage contains all harmful bacteria, viruses algae, fungi, protozoans ,helminthes.
Bacteria – E.coli , vibrio cholera , Shigella spp.Salmonella typhi ,Salmonella paratyphi etc.
Viruses – Reo virus ,Rota virus ,entero virus, Adeno virus etc.
Algae – Microcystis aeruginosa etc and various protozoans and helminthes are also present.
Several water borne diseases take place by waster like typhoid ,paratyphoid ,gastroenteritis,diahorrea etc.
AIM OF SEWAGE TREATMENT
1. Removal of floatable and suspended solids
2. Removal of all carcinogenic and mutagenic substances.
3. Removal of harmful pathogens from it.
WASTE WATER TREATMENT PROCESSES
On the basis of mode of operation it can be
On the basis of Steps it can be of four types
1. Preliminary Treatment – removal of floatable and suspended substances.
2. Primary Treatment – it uses the principles of Sedimentation ,particles are allowed to settle down according to their gravity.
3. Secondary /Biological Treatment – Degradation of organic matter by using Aerobic and Anaerobic microbes.
4. Advanced Treatment – in this treatment process chemicals are required for precipitation of biological nitrogen and phosphorus . Destruction of all microorganisms are carried out.
It involves Chlorination ,Ozonitation etc