Water Supply and Environmental Engineering MCQs 2026

Leak detection in distribution uses

1. A only rainfall gauges ✓
2. B district metering, acoustic sensors and pressure monitoring ✓
3. C only wind vanes ✓
4. D only BOD test ✓

Separate sewer system carries

1. A combined flow always in same pipe ✓
2. B sanitary sewage in one set and stormwater in another ✓
3. C only irrigation water ✓
4. D only potable water ✓

Combined sewer carries

1. A sanitary waste and storm runoff in same conduit ✓
2. B only roof drainage in separate pipe always ✓
3. C only industrial cooling water always separate by law everywhere ✓
4. D only canal seepage ✓

Self-cleansing velocity in sewers prevents

1. A solids deposition in pipe invert ✓
2. B pipe corrosion only ✓
3. C air pollution only ✓
4. D water hammer in mains ✓

Sewer grade is designed for

1. A self-cleansing at minimum flow and capacity at peak ✓
2. B zero slope always ✓
3. C maximum pressure flow ✓
4. D only atmospheric open channel in streets always ✓

Manholes in sewer lines are spaced for

1. A only decoration ✓
2. B only water treatment ✓
3. C inspection, cleaning and ventilation access ✓
4. D only fire hydrants ✓

Infiltration in sewers increases

1. A treatment efficiency always ✓
2. B dissolved oxygen in influent beneficially always ✓
3. C wastewater volume and treatment load ✓
4. D zero wet weather flow ✓

Sewage is defined as

1. A only roof rainwater ✓
2. B only irrigation runoff always ✓
3. C only industrial cooling clean water ✓
4. D wastewater containing human waste and domestic activities ✓

Storm sewer design uses

1. A only crop delta ✓
2. B only canal duty ✓
3. C rational method or storm models for peak runoff ✓
4. D only drip emitter curve ✓

Biochemical Oxygen Demand (BOD) measures

1. A total solids only ✓
2. B chlorine residual ✓
3. C hardness only ✓
4. D oxygen consumed by biodegradable organic matter ✓

Chemical Oxygen Demand (COD) measures

1. A only dissolved oxygen in river ✓
2. B only nitrogen gas ✓
3. C only turbidity ✓
4. D oxygen equivalent to oxidize organic and oxidizable inorganic matter ✓

High BOD effluent discharged to river causes

1. A increased DO always ✓
2. B zero eutrophication ✓
3. C deoxygenation and fish kill ✓
4. D improved water quality ✓

BOD/COD ratio near 0.5 suggests

1. A zero treatability ✓
2. B only chemical treatment possible always ✓
3. C no organic matter ✓
4. D biodegradable wastewater suitable for biological treatment ✓

Theoretical oxygen demand relates to

1. A only suspended solids mass ✓
2. B only pipe friction ✓
3. C only rainfall ✓
4. D complete oxidation stoichiometry of known compounds ✓

Seeding in BOD test is needed when

1. A sample is too clean distilled water only always ✓
2. B wastewater lacks sufficient microorganisms ✓
3. C COD is zero ✓
4. D temperature is 20°C ✓

COD test uses

1. A only 5-day incubation ✓
2. B only membrane filtration ✓
3. C strong chemical oxidant under reflux conditions ✓
4. D only sedimentation ✓

Primary treatment of sewage removes

1. A settleable solids by screening and sedimentation ✓
2. B dissolved nutrients completely ✓
3. C all pathogens completely ✓
4. D all dissolved organics ✓

Hardy Cross method analyzes

1. A only open channel jump ✓
2. B pipe network flows by successive head balance correction ✓
3. C only unit hydrograph ✓
4. D only BOD curve ✓

Water distribution system layouts include

1. A only sewer separate system ✓
2. B only drip irrigation laterals ✓
3. C only canal minors ✓
4. D dead end, gridiron and ring systems ✓

Turbidity in raw water is removed primarily by

1. A only chlorination ✓
2. B only fluoridation ✓
3. C coagulation, sedimentation and filtration ✓
4. D only aeration alone ✓

Ozone disinfection advantage includes

1. A long pipeline residual always without booster ✓
2. B zero cost always ✓
3. C no persistent THM formation like chlorine ✓
4. D no contact time needed ✓

Economical size of rising main balances

1. A only paint cost ✓
2. B only air quality ✓
3. C only crop intensity ✓
4. D pipe cost against pumping energy cost ✓

Water hammer in distribution mains is mitigated by

1. A instant valve closure always ✓
2. B slow closure of valves and surge tanks ✓
3. C removing air valves ✓
4. D zero pipe support ✓

Service reservoir in distribution provides

1. A storage for balancing, fire demand and pumping schedule ✓
2. B only sewage treatment ✓
3. C only rainfall measurement ✓
4. D only solid waste landfill ✓

Scouring velocity in mains prevents

1. A excessive leakage always desired ✓
2. B chlorine residual rise ✓
3. C sediment deposition in pipes ✓
4. D turbidity increase in source ✓

Minimum residual pressure at consumer fixtures should typically be

1. A zero always ✓
2. B 10–15 m head in flat areas per codes ✓
3. C 1000 m always ✓
4. D negative always ✓

Per capita water demand depends on

1. A only pipe colour ✓
2. B climate, living standards and industrialization ✓
3. C only dam height ✓
4. D only wind direction ✓

Average domestic water demand in Indian/Pakistani towns may range

1. A 5 litres only ✓
2. B 5000 litres only always ✓
3. C 135–225 litres per capita per day for design ✓
4. D zero in cities ✓

Fire demand in water supply design is often governed by

1. A only irrigation duty ✓
2. B only sewer infiltration ✓
3. C only rainfall intensity ✓
4. D largest fire flow plus simultaneous domestic use ✓

Coincidence factor in water demand means

1. A not all fixtures operate simultaneously ✓
2. B all taps open always ✓
3. C zero night flow ✓
4. D infinite peak always ✓

Industrial water demand is estimated from

1. A only canal Lacey formula ✓
2. B only unit hydrograph ✓
3. C only air quality index ✓
4. D process requirements and employee facilities ✓

Unaccounted for water (UFW) includes

1. A only billed consumption ✓
2. B leakage, illegal connections and metering errors ✓
3. C only fire flow ✓
4. D only crop evapotranspiration ✓

Peak hourly demand factor relates

1. A maximum hour flow to average daily flow ✓
2. B only annual rainfall to runoff ✓
3. C BOD to population only ✓
4. D Manning n to slope ✓

Design period for water supply project is typically

1. A 30 years for components with staged capacity ✓
2. B 1 day only ✓
3. C 500 years always ✓
4. D zero planning horizon ✓

Arithmetic increase method of population forecast assumes

1. A constant percentage growth ✓
2. B zero migration ✓
3. C logarithmic decline only ✓
4. D constant absolute increase per decade ✓

Geometric increase method assumes

1. A constant absolute increase ✓
2. B population never changes ✓
3. C negative growth always ✓
4. D constant percentage growth rate ✓

Decreasing growth rate method reflects

1. A saturation as city approaches limiting population ✓
2. B unlimited exponential growth forever ✓
3. C instant zero population ✓
4. D only industrial load ✓

Migration significantly affects population forecast in

1. A closed static villages only with no change ever ✓
2. B uninhabited deserts ✓
3. C new industrial towns and provincial capitals ✓
4. D ocean platforms without residents ✓

Design population for water works is projected to

1. A only past century ✓
2. B only one day event ✓
3. C end of design period from current census trend ✓
4. D zero residents ✓

Coagulation in water treatment uses chemicals to

1. A disinfect pathogens only ✓
2. B destabilize colloidal particles for aggregation ✓
3. C add hardness ✓
4. D increase colour permanently ✓

Flocculation follows coagulation to

1. A rapid mix only without floc growth ✓
2. B filter without settling ✓
3. C disinfect without contact ✓
4. D gentle mixing forming settleable floc ✓

Alum dosage in coagulation depends on

1. A only pipe diameter ✓
2. B only wind speed ✓
3. C raw water turbidity, alkalinity and pH ✓
4. D only crop type ✓

Sedimentation tank removes

1. A dissolved salts only ✓
2. B settleable floc by gravity ✓
3. C gases only ✓
4. D colour by oxidation only ✓

Surface overflow rate in sedimentation is defined as

1. A flow divided by plan area of tank ✓
2. B depth divided by width only ✓
3. C head loss in filter ✓
4. D BOD loading ✓

Rapid gravity sand filter removes

1. A only dissolved ions without media ✓
2. B only pathogens without disinfection ✓
3. C only CO2 only ✓
4. D fine suspended particles after sedimentation ✓

Effective size of filter sand refers to

1. A largest particle only ✓
2. B size passing 10% by weight in sieve analysis ✓
3. C average of extremes only without specification ✓
4. D depth of tank ✓

Backwashing of filters is done to

1. A remove accumulated solids and restore headroom ✓
2. B compact sand permanently ✓
3. C disinfect without chlorine ✓
4. D coagulate floc ✓

Chlorine disinfection residual maintained in distribution

1. A prevents microbial regrowth in pipes ✓
2. B increases turbidity always ✓
3. C softens water alone ✓
4. D coagulates alum ✓

Slow sand filter differs from rapid filter by

1. A higher rate and pressure only always ✓
2. B biological schmutzdecke and lower loading rates ✓
3. C no removal of bacteria ever ✓
4. D chemical coagulation always required ✓

Hardness in water is mainly due to

1. A sodium chloride only ✓
2. B oxygen only ✓
3. C calcium and magnesium salts ✓
4. D suspended clay only ✓

Activated sludge process uses

1. A anaerobic pond only without oxygen ✓
2. B only chlorination ✓
3. C aerobic microorganisms in mixed liquor with recycle ✓
4. D only slow sand filter ✓

Return activated sludge (RAS) maintains

1. A microbial population in aeration tank ✓
2. B zero MLSS ✓
3. C only grit in tank ✓
4. D only algae in clarifier ✓

Mean cell residence time (θc) increase generally improves

1. A effluent quality and nitrification potential ✓
2. B sludge washout always ✓
3. C zero treatment ✓
4. D only short circuit ✓

Trickling filter treatment relies on

1. A biofilm on media contacted by applied wastewater ✓
2. B suspended pure oxygen only without biomass ✓
3. C only chemical coagulation ✓
4. D only grit chamber ✓

Sludge volume index (SVI) indicates

1. A pipe roughness ✓
2. B settleability of activated sludge ✓
3. C rainfall depth ✓
4. D wind speed ✓

Anaerobic digestion of sludge produces

1. A only chlorine gas ✓
2. B only ozone ✓
3. C only pure oxygen without CO2 ✓
4. D biogas mainly methane and stabilized sludge ✓

Extended aeration activated sludge has

1. A very high organic loading always ✓
2. B no aeration ✓
3. C low F/M and long SRT with less excess sludge ✓
4. D only primary treatment ✓

Municipal solid waste composition in urban Pakistan/India includes

1. A only liquid sewage ✓
2. B organic fraction, paper, plastics and ash ✓
3. C only industrial acids always ✓
4. D only radioactive waste ✓

Sanitary landfill is designed with

1. A liners, leachate collection and daily cover ✓
2. B open burning only ✓
3. C direct river dumping ✓
4. D zero compaction ✓

Composting of MSW stabilizes

1. A all plastics completely ✓
2. B metals into gases only ✓
3. C glass rapidly ✓
4. D biodegradable organics into humus-like product ✓

Incineration of waste reduces

1. A volume to zero ash-free always ✓
2. B need for any air pollution control ✓
3. C volume and mass while recovering energy if controlled ✓
4. D toxic metals into nothing ✓

Leachate from landfill contains

1. A only distilled water ✓
2. B dissolved organics, ammonia and metals ✓
3. C only oxygen gas ✓
4. D zero contaminants ever ✓

Suspended particulate matter (SPM) in air affects

1. A only soil fertility beneficially always ✓
2. B only groundwater head ✓
3. C only pipe friction ✓
4. D respiratory health and visibility ✓

Photochemical smog involves

1. A NOx and VOCs forming ozone in sunlight ✓
2. B only CO2 alone without sunlight ✓
3. C only BOD in river ✓
4. D only chlorine in water ✓

Noise pollution level is measured on

1. A linear percentage only ✓
2. B decibel scale logarithmic with respect to reference pressure ✓
3. C BOD scale ✓
4. D Mohs hardness ✓

Catalytic converter in vehicles reduces

1. A only water demand ✓
2. B CO, HC and NOx in exhaust ✓
3. C only BOD in sewage ✓
4. D only canal seepage ✓

Pakistan NEQS for municipal wastewater set limits on

1. A BOD, COD, TSS and heavy metals for discharge ✓
2. B only rainfall intensity ✓
3. C only crop delta ✓
4. D only canal duty ✓

WHO drinking water guideline addresses

1. A only irrigation scheduling ✓
2. B only highway noise ✓
3. C microbial, chemical and radiological quality ✓
4. D only landfill compaction ✓

Dissolved oxygen in healthy river is typically

1. A zero always ✓
2. B saturated with BOD only ✓
3. C equal to COD ✓
4. D above 5 mg/L for cold water fisheries ✓

Eutrophication in lakes is driven by

1. A only sediment deposition without nutrients ✓
2. B nutrient enrichment especially nitrogen and phosphorus ✓
3. C only wind erosion ✓
4. D only chlorine residual ✓