environmental engineering important short one liner notes | environmental engineering notes | environmental notes

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ENVIRONMENTOL ENGINEERING-

 Use of metering system causes the decrease in

per capita consumption.

 1.5 is the hourly factor, 1.8 daily factor and

2.7 is the peak demand.

 The distribution mains are designed for

maximum hourly demand.

 Geometrical method is used for young and

rapidly developed cities for forecasting the

population.

 Arithmetical method is used for large cities.

 As compared to geometrical method

arithmetical method gives less value.

 Intakes are installed for drawing the water

from the sources.

 Reflux valve provided on the suction pipe in a

tube well.

 The maximum discharge in tube well is

50lit/sec.

 As compare to the shallow wells deep wells

have more discharge.

 Ground water is generally free from suspended

impurities.

 Malaria is not a water borne disease.

 The most common cause of acidity in water is

co2.

 The phenol compounds in water supply not

more than 0.001ppm.

 1.5mg/litre is the permissible limit of fluoride

content.

 Standard EDTA test is used to test the hardness

of water.

 Alkalinity in water is expressed in calcium

carbonate.

 The product of H and OH is 10^-14.

 PH-acidity/bascity.

 Turbidity is measured on standard silica scale.

 Colour on platinum cobalt scale.

 The turbidity of drinking water should be

10ppm.

 Residual chlorine is tested by starch iodide and

orthotolidine method.

 Total solids not more than 500ppm.

 Total chlorides not more than 250ppm.

 Iron and magnesia-0.3ppm.

 Lead and arsenic-0.05ppm

 Copper 3ppm, fluorine 1.5ppm.

 The dissolved oxygen in natural unpolluted

water is 10mg/litre.

 The length of the sedimentation tank not more

than 4 times the width.

 The over flow rate of plain sedimentation tank

is 500-750litre/hr/m^2.

 The settling velocity of a particle depends upon

surface area of tank.

 Efficiency of the sedimentation tank depends

upon surface area of the tank.

 For effective coagulation the PH value of

water found to be 6-8.5.

 The detention period of coagulation tank is 2 –

6 hour.

 The alum when added as coagulant it decreases

the PH value of water.

 Lime is used to increase the speed of the

sedimentation sewage.

 0.25-0.35 is the effective size of sand particle of

slow sand filter.

 Air binding phenomena in rapid sand filters

occurs due to excessive negative head.

 Backwashing provided in rapid sand filters.

 2-3 months is the period of cleaning of slow

sand filter.

 Time contact of chlorine is at least 30min.

 The percentage of chlorine in fresh bleaching

powder is 30 to 35%.

 The treatment of water with bleaching powder

is called hypo chlorination.

 The suitable method of disinfecting the

swimming pool water is ultraviolet rays

treatment.

 Sulphur dioxide used for dechlorination of

water.

 Disinfection efficiency reduced at higher PH

values.

 Copper sulphate is used for algae control.

 Activated carbon is used for removing odours.

 Dead end system is used for irregularly growing

towns.

 Radial system is used when the water is flowed

towards the outer periphery.

 Grid iron system is used for well planned cities.

 Circle method is used when fire demand is

considered.

 Sluice valve provided to regulate the flow of

water.

 Reflux valve provided to prevent the water flow

back in the opposite direction.

 Scour valves are provided at every depression

head and dead ends.

 House sewer-lateral sewer-common sewer-

main sewer-trunk sewer-outfall sewer.

 For country like India where rainfall is mainly

confined to one season separate system is

adopted.

 Combined system adopted when the rainfall is

distributed throughout the season.

 135litres domestic consumption.

 Sewerage system is generally designed for 25

years.

 For long and narrow pipe system equivalent

pipe method is used.

 Circular shape sewer is preferred in separate

system.

 Egg shape sewer is preferred in combined

system.

 The time of concentration –the time taken by

rainfall to run from most farthest point to the

point of disposal

 1 to 1.2m/sec is the self cleansing velocity of

sewer in Indian condition

 The slope of sewer should be in the direction of

natural slope of ground.

 6*DWF for separate system.

 Rainfall+2DWF for combined system.

 15cm &300cm is the minimum and maximum

diameter of sewer.

 The velocity of flow does not depend on length

of sewer.

 Circular brick sewer is used under culverts.

 Egg shaped sewer is suitable for both separate

and combined system.

 The characteristic of fresh and septic sewage is

alkaline and acidic.

 The pathogens likely killed by chlorination.

 Standard BOD is measured at 5 day 20 degree.

 TOD>COD>BOD.

 5 day BOD is less than 4 day BOD.

 The ratio of 5 day BOD to ultimate BOD is 2/3.

 4ppm is the minimum DO to avoid the fish kill.

 Dissolved oxygen in streams is maximum at

noon.

 The means of access for inspection and cleaning

of sewer is manhole.

 Sewerage system is designed for maximum and

minimum flow.

 Sewage treatment plant designed for average

flow only.

 Laying of sewers is usually done with the help

of boning rods and sight rails.

 In sewage oil and grease removed by skimming

tank.

 Detention period of grit chamber is 1 minute.

 Sludge digestion tank and septic tank unit

works on anaerobic condition.

 The maximum efficiency of BOD removal is

achieved in oxidation ditch.

 The working condition of imhoff tanks are

anaerobic in lower compartment and aerobic in

upper compartment.

 The detention period of oxidation pond is 10

to 15 days.

 Compositing and lagoning are the methods of

sludge disposal.

 Facultative bacteria works with or without

oxygen.

 For satisfactory working of sludge digestion

tank the PH value of water is 6-8.5.

 Normal value of sludge index is 150-350.

 Bangalore method practise anaerobic method

of disposal.

 Antisiphonage pipe is used to preserve the

water seal traps.

 In two pipe system one soil pipe, one waste

pipe and two vent pipes required.

 The gas from sludge digestion tank mainly

composed of methane.

 Most of the bacteria in sewage are saprophytic.

 Chlorine is used to separate grease.

 Shrouding is provided in slotted pipe tube well.

 Ozone layer in the outer atmosphere get

destroyed by chlorofluoro carbons.

 The intensification of green house gases is due

to CO2.

 Electrostatic precipitator is used to control

particulate emission.

 Spray tower is used to control both gaseous and

particulate pollutant.

 PAN and ozone are the secondary air pollutants.

 Sulphur dioxide and nitrogen oxide are the

primary air pollutant.

 The depletion of ozone layer in the outer

atmosphere causes the skin cancer.

 The acid rains are caused due to SO2 and

NOx.

 Blue baby disease caused due to excess of

nitrates.

 Dechlorination of water is achieved by sodium

thio sulphate.

 The efficiency sedimentation tank does not

depend upon depth of the tank.

 Ferrule-goose neck-stop cock-water meter.

 Under Indian condition the average per capita

demand is 30 to 75mg/day.

 Sewage sickness caused due to-clogging of

pores in soil due to excessive application of

sewage to land.

 Soil pipe carry human excrete.

 Screening-grit removal-primary sedimentation-

aeration-secondary sedimentation.

 Traps are used to prevent the entry of foul

smelling gases.

 Coal based thermal power stations produce

SO2,NOx and SPM.

 Zone of degradation-zone of active

decomposition-zone recovery-zone of clear

water.

 River water contain maximum amount of

turbidity.

 Ringle man scale is used to measure grade

density of smoke.

 Eutrophication of water is rich in nutrients.

 Zero hardness is achieved by ion exchange

method.

 Excess lead causes-anaemia, goitre caused due

to absence of iodide.

 Aerosol is dispersion of small solid or liquid

droplet.

 A commonly used hand pipe is reciprocating

pump.

 1st stage is carbonaceous demand 2nd stage is

nitrification demand.

 P-trap used for water closet.

 The sound level of jet air plane is 140 decibel.