Environmental Engg. Notes for GATE, PSUs preparations - part 5

Hello There,

How have you been? Here is the 5th part of your preparatory content, useful for GATE and PSUs.

• The suitable layout of distribution system for a city with roads of rectangular pattern is grid iron system.
• The commonly used material for water supply pipes, which has the properties of being strong, not easily corroded and long life but is heavy and brittle is cast iron.
• Hardy cross method of analysis of distribution system involves successive trials and is time consuming.
• The method of analysis of distribution system in which the domestic supply is neglected and fire demand is considered is circle method.
• The most suitable method of analysis for long and narrow pipe system is equivalent pipe method.
• Sluice valve is provided to control the flow of water in the distributed system at street corners and where the pipe lines intersect.
• Reflux valve allows water to flow in one direction but prevents its flow in the reverse direction.
• Scour valves are provided at every depression and dead ends to drain out the waste water that may collect there.
• A sewer that receives the discharge of a number of house sewers is called a lateral sewer.
• A pipe conveying sewage from plumbing system of a single building to common sewer or point of immediate disposal is called a house sewer.
• For a country like India, where rainfall is mainly confined to one season, the suitable sewerage system will be separate system.
• Average rate of water consumption per head per day as per Indian standard is 135 litres.
• Sewerage system is generally designed for 25 years.
• For combined system of sewerage, egg shaped sewer is preferred.
• The suitable system of sanitation for area of distributed rainfall throughout the year with less intensity is combined system.
• The water carriage system of collection of waste product requires treatment before disposal.
• The time of concentration is defined as the time taken by rainfall water to run from most distant point of water shed to inlet of sewer plus the time required for flow of water in sewer to the point under consideration.
• The specific gravity of sewage is slightly greater than 1.
• The self cleansing velocity for all sewers in India is usually 1.9 m/sec to 1.2 m/sec.
• The slope of sewer shall be given in the direction of natural slope of ground.
• The design discharge for the separate sewer system shall be taken as  6*DWF(dry weather flow).
• The design discharge for the combined sewer system shall be taken as rainfall + 6DWF.
• The minimum and maximum diameters of sewers shall preferably by 15 cm and 300 cm.
• The main disadvantage of concrete sewers is that they are difficult to transport due to their heavy weight.

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