Monday, January 6, 2014

Environmental Engg. Notes for GATE, PSUs preparations - part 10

Hello there,

Welcome to the part 10 of the one liner notes useful for the preparation of GATE and other similar examinations.
  • When Adiabatic Lapse Rate(ALR) is more than Environmental Lapse Rate(ELR), then the ELR can be called as Sub adiabatic lapse rate.
  • When Environment Lapse Rate(ELR) is more than Adiabatic Lapse Rate(ELR), then the environment is said to be unstable.
  • Temporary hardness in water is caused by the presence of bicarbonate of Ca and Mg.
  • Blue baby disease (mythemoglobinemia) in children is cause by the presence of excess nitrates.
  • Two samples of water A and B have pH values of 4.4 and 6.4 respectively. Sample A is 100 times more acidic than sample B.
  • If present in water, chlorination of water does not reduce the dissolved oxygen content.
  • De-chlorination of water is achieved by adding sodium thiosulphate.
  • The efficiency of sedimentation tank does not depend upon depth of tank.
  • Reverse osmosis and Electrodialysis reduces the salinity of water.
  • Cast iron pipes are joined by Spigot and socket joint.
  • Asbestos cement pipes are joined by simplex joint.
  • Plain ended pipes subjected to frequent vibrations are joined with Victaulic joint.
  • G.I. pipes are joined with Screwed joint.
  • The water supply to a house begins with the connection of the service pipe with the municipal water mains. The connection comprises Ferrule, Goose neck, Stopcock and water meter.                                                              [ES 93]
  • When the co-efficient of rugosity is increased from 0.01 to 0.02, the gradient of a pipe of a given diameter to carry the same flow at the same velocity will be increased by 4. [ES 93]
  • Trickling filter sludge has comparatively low sludge volume index.
  • BOD is preferred to COD as an index of sewage concentration  because BOD relates specifically to putrescible organic matter which is the most objectionable sewage constituent.
  • Detention time for Grit Chamber- 2 minutes; Primary sedimentation - two hours; Activated Sludge - Six hours; Sludge digestion - Twenty days.                                  [ES 93]
  • Under Indian conditions, the average per capita contribution of BOD is 50 to 70 gm/day.                                                                                                                      [ES 93]
  • Sewage sickness relates to clogging of pores in soil due to excessive application of sewage to land, obstructing aeration and leading to septic conditions.        [ES 93 & 99]
  • Waste pipe carries liquid watstes that do not include human excreta ; Soil pipe carries liquid wastes including human excreta ; Vent pipe provides flow of air to or from a drainage system in order to prevent vacuum pressure and excessive pressure and provides escape of foul gases.
  • Antisiphonage pipe preserves the water seal of traps through access to atmospheric air.

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