Conventional Wastewater Treatment Case Study

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1.4 CONVENTIONAL WASTEWATER TREATMENT PROCESS
Conventional wastewater treatment consists of a combination of physical, chemical and biological operations to remove solids, organic matter and nutrients from wastewater. The general terms used to describe different degrees of treatment, in order of increasing treatment levels are preliminary, primary, secondary and tertiary or advanced wastewater treatment.
Preliminary Treatment
The objective of preliminary treatment is removal of coarse solids and large size materials often found in raw wastewaters, to enhance the operation and maintenance of subsequent treatment units. Preliminary treatment typically include coarse screening, grit removal and in some case combination of large objects.
Primary Treatment
Primary treatment involves removal of settleable organic and inorganic solids by sedimentation, and removal of materials that float (scum) by skimming. Approximately 25-50 percent of the incoming BOD, 50-70 percent of the total suspended solids and 65 percent of the oil and grease are removed during primary treatment. Some organic nitrogen, organic phosphorous, and heavy metals associated with
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Relatively simple wastewater technologies can be designed to provide low cost sanitation and environmental protection while providing additional benefits from the reuse of water. Effluents from conventional treatment facility not only contain some unstable organic matter but also nutrients, which represent potential energy. It is therefore illogical to utilise external energy sources to dissipate energy stored within the wastewater. A natural treatment system makes use of aquatic animals and plants to improve he water quality and reclaim nutrients. In addition, persistent toxic environmental contaminants such as pesticides, aromatic hydrocarbons and

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