WorksheetsWATER TREATMENT
Total questions: 60
Worksheet time: 30mins
The rejection rate of a good RO membrane is usually:
40–50%
60–70%
95–99%
20–30%
Which pre-treatment is generally required before RO plant?
Softener
Multimedia filter
Activated carbon filter
All of the above
RO membrane is made of:
Polypropylene
Cellulose acetate or polyamide
PVC
Stainless steel
Which pre-treatment protects RO membrane from chlorine
Softener
Activated carbon filter
Multimedia filter
UV filter
Typical RO pressure for brackish water plants is:
5–10 psi
20–50 psi
500–800 psi
150–250 psi
Scaling in RO occurs due to:
High chlorine
High CO₂
High hardness (Ca, Mg salts)
Low pH
pH of RO permeate water is usually:
7.0–8.0
6.0–6.8
8.5–9.0
5.0–5.5
Which parameter is monitored online in RO plants?
Temperature
Conductivity
Turbidity
BOD
The main purpose of a water softener is:
To remove suspended solids
To remove bacteria
To remove calcium and magnesium ions
o remove dissolved salts
Water softening is mainly achieved by:
Reverse Osmosis
Ion Exchange process
Distillation
Sedimentation
The resin in a water softener is usually charged with:
Calcium ions
Magnesium ions
Sodium ions
Chloride ions
Regeneration of water softener is carried out using:
NaOH solution
Sodium chloride (NaCl) brine solution
Hydrochloric acid
Sodium bicarbonate
Hardness in water is caused mainly by:
Sodium and potassium salts
Calcium and magnesium salts
Iron and copper salts
Silica and sulfate salts
Which test is used to measure hardness of water?
TDS test
EDTA titration test
Turbidity test
Chlorine test
During regeneration, hardness ions (Ca²⁺, Mg²⁺) are replaced by:
Na⁺ ions
H+ ions
OH⁻ ions
cl-
The main function of a multimedia depth filter is:
removal of dissolved gases
Removal of dissolved salts
Removal of hardness
Removal of suspended solids & turbidity
Multimedia filter typically consists of layers of:
Sand, gravel, activated carbon
Anthracite, sand, gravel
Resin and carbon
Polypropylene and resin
The top layer of multimedia filter is usually made of:
Gravel
Anthracite coal
Fine sand
Carbon
Backwashing of MMF is required when:
TDS increases
Turbidity of feed decreases
Pressure drop across filter increases
Salt rejection decreases
Backwashing is done using:
Raw water in reverse direction
Air only
Brine solution
Sodium hypochlorite
The primary function of a carbon filter is
To remove hardness
To remove chlorine, taste, odor, and organics
To remove TDS
To remove turbidity
Activated carbon mainly works on the principle of:
Reverse osmosis
Sedimentation
Adsorption
Ion exchange
The main raw material used to make activated carbon is:
Anthracite coal, coconut shell, or wood
Sand and gravel
Polyamide resin
Limestone
The measure of adsorption capacity of carbon is given by:
Iodine number
Silt Density Index (SDI)
Conductivity
Turbidity
Spent (exhausted) activated carbon should be replaced when:
Chlorine appears in outlet
Pressure increases
TDS increases
pH drops
Contact time of water with carbon media is measured as:
EBCT (Empty Bed Contact Time)
LSI (Langelier Saturation Index)
SDI (Silt Density Index)
TDS
Typical EBCT (Empty Bed Contact Time) for ACF is:
< 1 hour
< 5 mints
5 hours
1 day
A DI system typically uses which type of resins?
Only cation resin
Only anion resin
Mixed-bed (cation + anion) resins
Activated carbon
In a DI system, final water purity is measured by:
TDS meter
Chlorine test
Conductivity or resistivity meter
pH meter
In dialysis water treatment, DI is usually placed:
Before RO unit
After RO unit (as polishing)
After multimedia filter
Before carbon filter
The main disadvantage of DI compared to RO is:
Produces high reject water
More expensive to install
Does not remove bacteria and endotoxins
Requires no regeneration
The main function of a UV irradiator in water treatment is:
To remove hardness
To kill or inactivate microorganisms
To remove chlorine
To reduce TDS
UV disinfection works on the principle of:
Ion exchange
Osmosis
Ultraviolet light absorption by DNA
Adsorption
The most effective wavelength for UV disinfection is:
185 nm
254 nm
365 nm
500 nm
UV irradiation inactivates microorganisms by:
Oxidizing cell walls
Destroying chlorophyll
Causing DNA mutation and preventing replication
Reducing oxygen
UV irradiator is ineffective in removing:
Bacteria
Viruses
Endotoxins and dissolved organics
Fungi
. If UV intensity decreases, the possible cause is:
Fouled quartz sleeve
Aging of UV lamp
Low flow rate
Both a and b
The usual replacement interval for UV lamps is:
Every 1–2 months
Every 6–12 months
Every 3–5 years
Never
A UV intensity monitor in the system is used to:
Monitor lamp performance
Check water pressure
Measure chlorine
Control pH
UV disinfection is often placed in dialysis water systems:
Before carbon filter
After RO or before distribution loop
After softener
After DI
Answer: b
UV lamp should not be touched with bare hands because:
It may shock the operator
Oil from fingers reduces UV transmission
It reduces lamp life by 1 month
It increases intensity
Which maintenance step is essential for UV units?
Regular cleaning of quartz sleeve
Backwashing
Chlorine dosing
Resin regeneration
The primary purpose of an endotoxin filter is to remove:
Hardness salts
Chlorine and chloramine
Bacteria and endotoxins (pyrogens)
Dissolved salts
Endotoxin filters are generally placed:
After reverse osmosis (RO)
Before multimedia filter
Before softener
Before carbon filter
Endotoxins are fragments of:
Gram-positive bacteria
Gram-negative bacterial cell walls (lipopolysaccharides)
Fungal spores
Viral capsids
Which test is commonly used to detect endotoxins in water?
pH test
Chlorine test
LAL test (Limulus Amebocyte Lysate)
TDS test
If an endotoxin filter fails, the most likely risk for dialysis patients is:
Hypertension
Pyrogenic reaction and sepsis
Dehydration
Electrolyte imbalance
In dialysis units, the distribution of RO water is generally designed as:
Dead-end system
Loop circulation system
single pass without return
Batch storage system
. A dead-end water distribution system is avoided because:
It increases flow velocity
It promotes bacterial growth and stagnation
It increases hardness
It increases pressure
The preferred piping material for RO water in dialysis is:
Copper
Galvanized iron
Stainless steel 316L or medical-grade PVC/PEX
Carbon steel
The purpose of continuous recirculation in RO water loop is to:
Prevent bacterial growth and biofilm formation
Maintain TDS
Reduce water pressure
Lower temperature
The main microbial risk in RO water piping is:
Biofilm formation
Scale formation
Chloride corrosion
Calcium precipitation
Which distribution design minimizes risk of microbial contamination?
Dead-leg design
Continuous loop with turbulent flow
Storage tank with no recirculation
Direct feed only
To ensure microbiological control, the loop piping system is regularly:
Painted
Chlorinated or heat sanitized
Acid washed only
Pressure tested only
The main purpose of tank washing in an RO water system is:
To reduce TDS
To remove biofilm, bacterial growth, and deposits
To increase hardness
To reduce conductivity
The most common chemical used for loop disinfection in dialysis RO systems is
Sodium chloride
Sodium bicarbonate
Sodium hypochlorite or peracetic acid
Citric acid only
The frequency of tank wash and loop disinfection in dialysis water systems should be:
Once a year
Once in 5 years
Only when patient infection occurs
As per AAMI/ISO standards – typically weekly or as validated
During tank washing, the drain valve is opened to:
Adjust pH
Add disinfectant
Remove residual chemicals and sediments
increase water level
After chemical disinfection of the loop, it is essential to:
Rinse thoroughly until no residual disinfectant remains
Add chlorine for safety
Reduce pressure in the loop
Increase flow velocity only
In a properly designed RO loop, disinfection is easier because:
There are no dead legs
Tank is oversized
TDS is very high
Loop runs at low velocity
