The presence of calcium and magnesium chloride in water causes = hardness 

The turbidity in water is caused due to = silt clay and finally divided organic matter

Suspended impurities include = algae, Protozoa, Fungi

The presence of sodium chloride in water = softness the water

The presence of hydrogen sulphide in water causes = acidity

The turbidity of the water is expressed in terms of = silica scale

The colour of the water is expressed in a number of a = Platinum Cobalt scale

The oder of water can be determined by = Osmoscope

The commercial Osmoscope is graduated with a PO value from = 0 to 5

When the pH value of water is 5 then it has = extremely strong order

The maximum permissible temperature for domestic supply is =  10 to 15

The maximum permissible colour for domestic supply on Platinum-Cobalt scale is  = 10 to 20 PPM

The maximum permissible total solid content in water for the domestic purpose should not exceed = 500 PPM

The maximum permissible chloride content in water for domestic supplies should not exceed = 250 PPM

The product of H+ ions and OH- ions in water solution is equal – to 10 to 14

The maximum acidity in water will occur at a PH value of = 0 (zero)

The most common causes of acidity in water is = carbon dioxide

When the pH value of water is…… the water is said to be acidic = less than 7

When the pH value of water is more than 7 it represents  water = alkaline

The maximum permissible quantity of iron and manganese in water for the domestic purpose should be = 0.3 PPM

The pH value of water for public supply is limited from = 6.5 to 8

The maximum permissible quantity of lead in water for domestic supply is = 0.05 PPM

The maximum permissible chlorine content in water for domestic supply should be = 1.5 PPM

The bacteria which can survive without oxygen is called = anaerobic bacteria

The bacteria which require oxygen for their survival is known as = aerobic bacteria

Biochemical oxygen demand of safe drinking water must be = (0)  zero

 In the process of screening the screens should be inclined at an angle of = 45 degrees to 60 degree

Plain sedimentation is a process of retaining water in a basin so that the suspended particles settle down as a result of the = action of gravity and forces

The rate of setting of particles in water depends upon the = viscosity of water, density of water, specific gravity of particles

The detention time for an ordinary plain sedimentation tank is = 6 to 8 hours

In a plain sedimentation tank under normal condition, impurities are removed up to = 70%

The velocity of flow in any sedimentation tanks should not exceed = 5 mm/s

The efficiency of sedimentation tanks for a given discharge can be increased = by increasing the surface area of tank

The most common Coagulant is = alum

The alum when mixed with water as a coagulant = decreases PH value of water

The process of purifying water by passing it through a bed of fine granular material is called = filtration

The effective size of sand particles for through sand filters varies from = 0.30 to 0.35 mm

The effective size of sand particles for rapid sand filters marriage from = 0.35 to 0.60 mm

The coefficient of uniformity for a slow sand filter is = 1.75

slow sand filter required ……….. area as compared to rapid sand filter = more

the Coagulation is not required in………. filters = slow sand

The slow sand filter should be cleared if the loss of head become more than = 1.2 m

After cleaning the slow sand filter the filtered water should not be used for a period of = 24 hours to 48 hoursØ

Cleaning period for slow sand filter is taken as = 1 month to 3 month

Rate of filtration of a slow sand filter ranges from = 100 to 200 litres

Most commonly used disinfectant for drinking water throughout the world is = chlorine

The ideal method of disinfection of swimming pool water is by = Ozonisation

The treatment of water with only Chlorine is known as = plain Chlorination

Pre-chlorination improves – coagulation reduces odours, reduces tastes

when the chlorine is added beyond the breakpoint the process of treating  the water is known as = super chlorination

The process of removing excess chlorine from water is called = dechlorination

The process of dechlorination is followed by = superchlorination

The amount of chlorine used for plain colocation of water is about = 0.5 PPM

The percentage of chlorine in fresh Bleaching powder is = 30 to 35%

The temporary hardness in water is caused due to the salts  like = carbonates

The permanent hardness of water can be removed by = Zeolite process

 By lime soda process hardness can be reduced to less than = 50 PPM

Zeolite process is also known as = base exchange process,  cation exchange process

The aeration of water is done to remove = colour, odour, taste

An average adult at rest inhales about …….. kg of air per day = 16

Atmospheric temperature rises because of the release of = CO2

Atmospheric temperature decreases because of the release of = suspended particulate matter

Thermal power plants mostly produced = SO2

The oxides of Nitrogen formed at very high temperature is a = NO

The gas that forms smog is NO2

The major source of Hydrocarbons is = gasoline exhaust

Ammonia of the atmosphere = neutralises acids

The sky appears brownish  because of the = presence of excess NO2 in the atmosphere

Rubber loses elasticity and gets cracked because of = O3

Coal  having 1% sulphur produces about …… kg of SO2 per tonne = 16

the minimum dissolved oxygen which should always be present in water in order to save the aquatic life  = 4 ppm

 ph value –

Water – 7

Salt – 7

Blood – 7.4

Milk – 6.4

Alcohol – 2.8

Sea water – 8.5

Man urine- 4.8 to 8.4

Lemon -2.4


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