Public Health Engineering
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
