2024 OIT EXAM WITH CORRECT
ANSWERS
What are colloids? - CORRECT-ANSWERSVery small particles suspended in
water which are resistant to settling.
What is turbidity measured in? - CORRECT-ANSWERSNephelometric Turbidity
Units (NTU)
What is the formula for circumference? - CORRECT-ANSWERSC=2πr
What does GUDI stand for? - CORRECT-ANSWERSGroundwater Under Direct
Influence of Surface Water
What is activated carbon good for? - CORRECT-ANSWERS-very porous
material to adsorb organic compounds
-very large SA for adsorbing
-can be cleaned by intense heat and reused
What is Alum good for? - CORRECT-ANSWERS-a coagulant
-results in particles sticking together to form a floc
-can be removed via sedimentation
What is Alum short for? - CORRECT-ANSWERSAluminum sulphate
What is the most used chemical for disinfection? - CORRECT-
ANSWERSChlorine
What is another word for disinfection? - CORRECT-ANSWERSInactivation
How can you detect chlorine gas? - CORRECT-ANSWERSBy putting ammonia
on a cloth, white smoke forms when it comes into contact with Cl
What is the dosage of chlorine? - CORRECT-ANSWERSThe specific amount of
CL that should be used
What is the name for the specific amount of Cl that should be used? -
CORRECT-ANSWERSDosage
What is the name of the amount of time needed for inactivation with
chlorine? - CORRECT-ANSWERSContact time
,What will chlorine react with in water? - CORRECT-ANSWERSBoth organic and
inorganic materials
What is chlorine demand? - CORRECT-ANSWERSDifference between the
amount of Cl added (dosage) and the amount remaining (residual) after a
given contact time
What is the formula to find residual Chlorine? - CORRECT-ANSWERSCl
dosage- Cl demand= Cl residual
When does combined chlorine occur? - CORRECT-ANSWERSWhen there is
ammonia in the water, chlorine will react with it to create CC
What is the formula for total residual chlorine? - CORRECT-ANSWERSTotal CL
residual= free Cl residual+ combined Cl residual
What is the amount of free oxygen in water known as? - CORRECT-
ANSWERSDissolved O2
What is the total amount of O2 that can be dissolved in water dependent on?
- CORRECT-ANSWERSWater temp
What is BOD and what does it determine? - CORRECT-ANSWERSThe amount
of O2 required by bacteria while stabilizing decomposable organic matter.
Determines the organic strength (amount of organic pollution) in wastewater
The Higher the BOD, the higher the organic material
Why is nitrogen in water harmful? - CORRECT-ANSWERSNitrites can be toxic
to infants
What does the presence of nitrogen in water indicate
? - CORRECT-ANSWERSPollution
Why is phosphorous needed in WWT? - CORRECT-ANSWERSIt is a
requirement for plant and bacterial growth, needed to ensure nutrients for
microorganisms
What is alkalinity expressed as? - CORRECT-ANSWERSMilligrams per litre as
calcium carbonate (mg/L as CaCO3)
What could colour in water be a precursor to? - CORRECT-
ANSWERSDisinfection by-product formation
, Who is the harness of water removed by? - CORRECT-ANSWERSThe
consumer
What can the measurements of solids in water do? - CORRECT-
ANSWERSProvide a quick indication of water quality
What is the name of solids that can pass through an extremely fine mesh
filter? - CORRECT-ANSWERSDissolved solids
What are dissolved solids? - CORRECT-ANSWERSsolids that can pass through
an extremely fine mesh filter
What are settleable solids? - CORRECT-ANSWERSSolids which will settle to
the bottom of the liquid if left for a period of time
How are suspended solids measured? - CORRECT-ANSWERSBy entrapment of
on a filter
How do you measure total solids? - CORRECT-ANSWERSWeighing the residue
left when a given volume of water is evaporated
What are volatile solids? - CORRECT-ANSWERSSolids which, when a total
solid sample or suspended sample is heated to a high temp, are burnt off.
These solids approximate the amount of organic material in the water
What is the turbidity measurement that is visible to the naked eye? -
CORRECT-ANSWERS5 NTU
What is an important indicator of treatment efficiency and particularly the
efficiency of filters and disinfection processes? - CORRECT-
ANSWERSTurbidity
Why are particles that cause turbidity harmful? - CORRECT-ANSWERSThey
can hide or entrap harmful organisms so that the disinfectant is unable to
reach them. It calls increases CL demand which can be carcinogenic
What are the 2 types of sampling? - CORRECT-ANSWERSGrab samples and
composite samples
What are grab samples and when is it used? - CORRECT-ANSWERSA single
sample taken at one place and time. Used when water quality and quantity
are not variable
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