Public Health Engineering

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BOD of safe drinking water = __

0

count of bacteria / cm3 for domestic water

0-100 / cm3

commercial osmoscope range

0-5 PO

arsenic maximum permissible content

0.05 PPM

maximum permissible lead content

0.05 PPM

maximum permissible chlorine content

0.1 - 0.2 PPM

screen velocity

0.3 m/s min 0.75-1 m/s max

slow sand filtration particle size

0.3-0.35 mm

effective size of sand particles for filtration (slow or rapid)

0.3-0.5mm

effective size of rapid sand filter particles

0.35-0.5mm

plain chlorination amount of chlorine required

0.5 PPM

filtration sand particles uniformity coefficient varies from ___

1.3-1.75

maximum permissible fluorine

1.5 PPM

rapid sand filter particles coefficient of uniformity

1.6

slow filtration sand particles coefficient of uniformity

1.75

maximum temperature for domestic water supply

10-15 C

maximum permissible color for domestic water

10-20 PPM on platinum cobalt scale

maximum permissible hardness

100 PPM

rate of filteration of slow sand filter

100-200 liters/m2/hr

slow sand filter area requirement

100-2000 m2

how long does it take to clean a rapid sand filter?

2-3 days

sedimentation with coagulation detention period

2-6 hours

chlorination minimum time of contact

20 mins

water odour test temperature

20-25 C

after cleaning, how long should slow sand filters run without consuming the water?

24-48 hours

maximum permissible chloride content

250 ppm

maximum permissible copper content

3 PPM (small amount copper good for health)

sedimentation tank depth

3-6 meters

rate of rapid filtration compared to slow filtration

30 times

rate of rapid filtration

3000-6000 liters/m2/hour

rapid sand filters can remove up to ___ PPM turbidity?

35-40 PPM

screen angle

45-60 to the horizontal

sand for filtration should not lose more than __% of weight when placed in hydrochloric acid for 24 hours

5%

maximum allowable turbidity for domestic water

5-10 PPM silica

slow sand filter can remove up to ___PPM turbidity from water

50 PPM turbidity

maximum permissible total solids

500 ppm

ordinary plain sedimentation tank detention time

6-8 hours

pH range of domestic water

6.5-8 pH

plain sedimentation can remove ___ suspended matter and ___ bacteria?

60% suspended 75% bacteria

in plain sedimentation tank, impurities are removed up to what percent?

70%

wastewater treatment Pak Standards BOD should be less than or equal to =

80 mg/L

rapid sand filters can remove up to ____% of bacteria

80-90%

slow sand filter can remove up to ___% of bacteria from water

99%

osmoscope units

PO

units of turbidity

PPM on silica scale

Which of the following is a suspended impurity: iron, chlorine, bacteria, or all of these

bacteria (think in terms of what can be filtered out)

what are facultative bacteria?

bacteria that can survive without oxygen

chlorine and ammonia can cause what in water?

bad taste and color

manganese causes what in water?

brown color

what is the most common cause of acidity in water? - hydrogen, oxygen, carbon dioxide, or all of these?

carbon dioxide

total solids are...

chlorides, nitrates, and compounds that cause HARDNESS in water

lime and magnesium carbonate can be used for

coagulation

when you hear "finely divided", what kinds of particles/components of wastewater should you think of?

colloidal impurities

amount of collodial impurities is determined by...

color tests

fungi causes....

color, odour, and turbidity

what compound is most commonly used to control algae?

copper sulfate (CuSO4)

Spirilla are _______ shaped bacteria

corkscrew / twisted rod

oxygen can have what negative affect in water?

corrodes metal

what does the starch-iodide method do?

determines residual chlorine

bacteria causes...

disease!

PO value of 3

distinct odor

collodial impurities cause

epidemic color in water

PO value of 5

extremely strong odor

common hints to know if something is a coagulant

ferrous or ferric, alum or aluminum (can be ferrous or aluminum sulphate)

the length of rectangular sedimentation tank should not be more than ___ the width of the tank

four times

rapid sand filter uses pressure _____ than/to atmospheric pressure

greater than

when should a rapid sand filter be cleaned?

head loss of 2.5m

maximum permissible iron and manganese content

less than 0.3 PPM

sedimentation tank velocity of flow

less than 5 mm/s (or 30 cm/min)

iron and manganese ill effects

make water brownish red leads to growth of microorganisms and corrodes pipes

dissolved impurities are?

metals, gases, salts, like iron, lead, oxygen, CO2, NaCl, etc

PO value of 0

no perceptible odor

when lead is present in water, it: changes, its color, causes turbidity, causes alkalinity, or none of these

none of these

collodial impurities - how removed?

not by ordinary filters

color of water, how measured?

on a platinum cobalt scale

sulphates, chrlorides, and nitrates of calcium and magnesium cause...

permanent hardness

what causes tastes and odors?

presence of microorganisms, dissolved gases, minerals

Bacilli are what shape?

rod shaped bacteria

which kind of filter uses atmospheric pressure?

slow sand filter

NaCl causes what in water

softening

carbonate and bicarbonate cause what in water

softening

what does sodium carbonate do in water?

softens water

sodium carbonate causes ___ in water

softness

cocci are what shape?

sphere shaped bacteria

you can increase the efficiency of a sedimentation tank by increasing what physical property?

surface area

turbidity caused by?

suspended and colloidal matter

calcium and magnesium carbonates or bicarbonates cause...

temporary hardness

odour in water changes with temp (T/F)

true

the presence of calcium and magnesium bi-carbonates in water causes hardness? (t or false)

true

inorganic matter causes...

turbidity

suspended impurities determined by which quality?

turbidity

PO value of 1

very faint odor

what turbidity is plain chlorination used for?

water with turbidity less than 20-30 PPM

when should slow sand filter be cleaned?

when head loss hits 1.2 m

when is coagulation prior to sedimentation necessary?

when turbidity exceeds 45 PPM

CO2 causes what in water?

acidity

hydrogen sulphide causes what in water?

acidity

suspended impurities

algae, protozoa, fungi, silt, clay, minerals, organic and inorganic matter basically anything that can be removed by filtration or sedimentation

alkalinity in water is caused by: - sodium carbonate, potassium carbonate, calcium hydroxide, or all of these?

all of these

what is the most common coagulant?

alum


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