Wednesday, January 8, 2014

Environmental Engg. Notes for GATE, PSUs preparations - part 11

Hello there,

Welcome to the part 11 of the one liner notes useful for the preparation of GATE and other similar examinations.

  • A confined aquifer is bound at top and below by impervious strata, the pressure of water is greater than atmospheric pressure and he aquifer is fully saturated.
  • Qualitatively, slow sand filters are more efficient than rapid sand filters but their flow rate is much smaller than that of pressure filters.
  • Type II settling in water treatment is defined as settling of flocculant particles in dilute suspensions.
  • Nalgonda technique is used for fluoride removal, lime soda process for softening and ozonation for disinfection.
  • In water supply distribution networks, the dead end system is not favored because the pressure at the dead-ends becomes un-desirably low in case of the additional extensions, it is difficult to maintain the residual chlorine level at the dead ends and at the times of repair the connections beyond the point of repair are deprived of  water.
  • The ideal residual pressure at the farthest consumer's tap in a properly designed water distribution system is in the range of 0.031 to 0.035 N/mm^2.
  • Under natural conditions of flow, an unpolluted river would contain less dissolved oxygen in summer than in winter.
  • For the combined sewerage system, egg-shaped sewers are preferred because they offer good flow velocity during the dry-weather-flow condition.
  • The correct sequence of various unit operations in exit in a sewage treatment plant is 1) screening 2) Grit removal 3) primary sedimentation 4) aeration  5) Secondary sedimentation.
  • In correct sequence, the reactions which take place during anaerobic digestion of organics is 1) acid fermentation 2) acid regression  3) alkaline fermentation  4) methane production.
  • Traps are used in household drainage systems to prevent entry of foul gases in the house.
  • Coal based thermal power stations pollute the atmosphere by adding NOx, SO2 and SPM.
  • Area method of land filling is most suitable when adequate depth of cover material is available at the site.
  • Electrical conductivity(EC) of water increase with increase in Total dissolved solids(TDS) in water.
  • When two identical centrifugal pumps are operating in series on a common rising main, then pressure in the rising main will be nearly doubled, while the discharge will remain the same.
  • In transition of sewers from smaller diameter sewers to larger diameter sewers, the continuity of sewers is maintained at the crowns of the sewers.

Thanks for your visit!

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