Environmental Engg. Notes for GATE, PSUs preparations - part 7

Hello there,
Welcome to the part 7 of the one liner notes useful for the preparation of GATE and other similar examinations.

• 5  Days BOD is less than 4 days BOD keeping other conditions same.
• If Biochemical oxygen demand(BOD) of a town is 20,000 kg/day and BOD per capita per day is 0.05 kg, then population equivalent of town is 400,000.
• The rate of BOD exerted at any time is directly proportional to BOD remaining.
• The ratio of 5 day BOD to ultimate BOD is about 2/3.
• The minimum dissolved oxygen which should always be present in water in order to save aquatic life is 4 ppm.
• The relative stability of a sewage sample, whose dissolved oxygen is same as the total oxygen required to satisfy BOD, is 100.
• Dissolved oxygen in stream is maximum at noon.
• Facultative bacteria are able to work in presence as well as in absence of oxygen.
• The means of access  for inspection and cleaning of sewer line is known as manhole.
• Sewerage system is designed for maximum and minimum flow.

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Reference: Book " Civil Engineering Objectives" by S P Gupta and S P Gupta.