Water Supply and Environmental Engineering MCQs 2026

Dissolved oxygen in healthy river is typically

1. Azero always✓
2. Bsaturated with BOD only✓
3. Cequal to COD✓
4. Dabove 5 mg/L for cold water fisheries✓

WHO drinking water guideline addresses

1. Aonly irrigation scheduling✓
2. Bonly highway noise✓
3. Cmicrobial, chemical and radiological quality✓
4. Donly landfill compaction✓

Pakistan NEQS for municipal wastewater set limits on

1. ABOD, COD, TSS and heavy metals for discharge✓
2. Bonly rainfall intensity✓
3. Conly crop delta✓
4. Donly canal duty✓

Catalytic converter in vehicles reduces

1. Aonly water demand✓
2. BCO, HC and NOx in exhaust✓
3. Conly BOD in sewage✓
4. Donly canal seepage✓

Noise pollution level is measured on

1. Alinear percentage only✓
2. Bdecibel scale logarithmic with respect to reference pressure✓
3. CBOD scale✓
4. DMohs hardness✓

Photochemical smog involves

1. ANOx and VOCs forming ozone in sunlight✓
2. Bonly CO2 alone without sunlight✓
3. Conly BOD in river✓
4. Donly chlorine in water✓

Suspended particulate matter (SPM) in air affects

1. Aonly soil fertility beneficially always✓
2. Bonly groundwater head✓
3. Conly pipe friction✓
4. Drespiratory health and visibility✓

Leachate from landfill contains

1. Aonly distilled water✓
2. Bdissolved organics, ammonia and metals✓
3. Conly oxygen gas✓
4. Dzero contaminants ever✓

Incineration of waste reduces

1. Avolume to zero ash-free always✓
2. Bneed for any air pollution control✓
3. Cvolume and mass while recovering energy if controlled✓
4. Dtoxic metals into nothing✓

Composting of MSW stabilizes

1. Aall plastics completely✓
2. Bmetals into gases only✓
3. Cglass rapidly✓
4. Dbiodegradable organics into humus-like product✓

Sanitary landfill is designed with

1. Aliners, leachate collection and daily cover✓
2. Bopen burning only✓
3. Cdirect river dumping✓
4. Dzero compaction✓

Municipal solid waste composition in urban Pakistan/India includes

1. Aonly liquid sewage✓
2. Borganic fraction, paper, plastics and ash✓
3. Conly industrial acids always✓
4. Donly radioactive waste✓

Extended aeration activated sludge has

1. Avery high organic loading always✓
2. Bno aeration✓
3. Clow F/M and long SRT with less excess sludge✓
4. Donly primary treatment✓

Anaerobic digestion of sludge produces

1. Aonly chlorine gas✓
2. Bonly ozone✓
3. Conly pure oxygen without CO2✓
4. Dbiogas mainly methane and stabilized sludge✓

Sludge volume index (SVI) indicates

1. Apipe roughness✓
2. Bsettleability of activated sludge✓
3. Crainfall depth✓
4. Dwind speed✓

Trickling filter treatment relies on

1. Abiofilm on media contacted by applied wastewater✓
2. Bsuspended pure oxygen only without biomass✓
3. Conly chemical coagulation✓
4. Donly grit chamber✓

Mean cell residence time (θc) increase generally improves

1. Aeffluent quality and nitrification potential✓
2. Bsludge washout always✓
3. Czero treatment✓
4. Donly short circuit✓

Return activated sludge (RAS) maintains

1. Amicrobial population in aeration tank✓
2. Bzero MLSS✓
3. Conly grit in tank✓
4. Donly algae in clarifier✓

Activated sludge process uses

1. Aanaerobic pond only without oxygen✓
2. Bonly chlorination✓
3. Caerobic microorganisms in mixed liquor with recycle✓
4. Donly slow sand filter✓

Primary treatment of sewage removes

1. Asettleable solids by screening and sedimentation✓
2. Bdissolved nutrients completely✓
3. Call pathogens completely✓
4. Dall dissolved organics✓

COD test uses

1. Aonly 5-day incubation✓
2. Bonly membrane filtration✓
3. Cstrong chemical oxidant under reflux conditions✓
4. Donly sedimentation✓

Seeding in BOD test is needed when

1. Asample is too clean distilled water only always✓
2. Bwastewater lacks sufficient microorganisms✓
3. CCOD is zero✓
4. Dtemperature is 20°C✓

Theoretical oxygen demand relates to

1. Aonly suspended solids mass✓
2. Bonly pipe friction✓
3. Conly rainfall✓
4. Dcomplete oxidation stoichiometry of known compounds✓

BOD/COD ratio near 0.5 suggests

1. Azero treatability✓
2. Bonly chemical treatment possible always✓
3. Cno organic matter✓
4. Dbiodegradable wastewater suitable for biological treatment✓

High BOD effluent discharged to river causes

1. Aincreased DO always✓
2. Bzero eutrophication✓
3. Cdeoxygenation and fish kill✓
4. Dimproved water quality✓

Chemical Oxygen Demand (COD) measures

1. Aonly dissolved oxygen in river✓
2. Bonly nitrogen gas✓
3. Conly turbidity✓
4. Doxygen equivalent to oxidize organic and oxidizable inorganic matter✓

Biochemical Oxygen Demand (BOD) measures

1. Atotal solids only✓
2. Bchlorine residual✓
3. Chardness only✓
4. Doxygen consumed by biodegradable organic matter✓

Storm sewer design uses

1. Aonly crop delta✓
2. Bonly canal duty✓
3. Crational method or storm models for peak runoff✓
4. Donly drip emitter curve✓

Sewage is defined as

1. Aonly roof rainwater✓
2. Bonly irrigation runoff always✓
3. Conly industrial cooling clean water✓
4. Dwastewater containing human waste and domestic activities✓

Infiltration in sewers increases

1. Atreatment efficiency always✓
2. Bdissolved oxygen in influent beneficially always✓
3. Cwastewater volume and treatment load✓
4. Dzero wet weather flow✓

Manholes in sewer lines are spaced for

1. Aonly decoration✓
2. Bonly water treatment✓
3. Cinspection, cleaning and ventilation access✓
4. Donly fire hydrants✓

Sewer grade is designed for

1. Aself-cleansing at minimum flow and capacity at peak✓
2. Bzero slope always✓
3. Cmaximum pressure flow✓
4. Donly atmospheric open channel in streets always✓

Self-cleansing velocity in sewers prevents

1. Asolids deposition in pipe invert✓
2. Bpipe corrosion only✓
3. Cair pollution only✓
4. Dwater hammer in mains✓

Combined sewer carries

1. Asanitary waste and storm runoff in same conduit✓
2. Bonly roof drainage in separate pipe always✓
3. Conly industrial cooling water always separate by law everywhere✓
4. Donly canal seepage✓

Separate sewer system carries

1. Acombined flow always in same pipe✓
2. Bsanitary sewage in one set and stormwater in another✓
3. Conly irrigation water✓
4. Donly potable water✓

Leak detection in distribution uses

1. Aonly rainfall gauges✓
2. Bdistrict metering, acoustic sensors and pressure monitoring✓
3. Conly wind vanes✓
4. Donly BOD test✓

Scouring velocity in mains prevents

1. Aexcessive leakage always desired✓
2. Bchlorine residual rise✓
3. Csediment deposition in pipes✓
4. Dturbidity increase in source✓

Service reservoir in distribution provides

1. Astorage for balancing, fire demand and pumping schedule✓
2. Bonly sewage treatment✓
3. Conly rainfall measurement✓
4. Donly solid waste landfill✓

Water hammer in distribution mains is mitigated by

1. Ainstant valve closure always✓
2. Bslow closure of valves and surge tanks✓
3. Cremoving air valves✓
4. Dzero pipe support✓

Minimum residual pressure at consumer fixtures should typically be

1. Azero always✓
2. B10–15 m head in flat areas per codes✓
3. C1000 m always✓
4. Dnegative always✓

Hardy Cross method analyzes

1. Aonly open channel jump✓
2. Bpipe network flows by successive head balance correction✓
3. Conly unit hydrograph✓
4. Donly BOD curve✓

Economical size of rising main balances

1. Aonly paint cost✓
2. Bonly air quality✓
3. Conly crop intensity✓
4. Dpipe cost against pumping energy cost✓

Water distribution system layouts include

1. Aonly sewer separate system✓
2. Bonly drip irrigation laterals✓
3. Conly canal minors✓
4. Ddead end, gridiron and ring systems✓

Ozone disinfection advantage includes

1. Along pipeline residual always without booster✓
2. Bzero cost always✓
3. Cno persistent THM formation like chlorine✓
4. Dno contact time needed✓

Turbidity in raw water is removed primarily by

1. Aonly chlorination✓
2. Bonly fluoridation✓
3. Ccoagulation, sedimentation and filtration✓
4. Donly aeration alone✓

Hardness in water is mainly due to

1. Asodium chloride only✓
2. Boxygen only✓
3. Ccalcium and magnesium salts✓
4. Dsuspended clay only✓

Slow sand filter differs from rapid filter by

1. Ahigher rate and pressure only always✓
2. Bbiological schmutzdecke and lower loading rates✓
3. Cno removal of bacteria ever✓
4. Dchemical coagulation always required✓

Chlorine disinfection residual maintained in distribution

1. Aprevents microbial regrowth in pipes✓
2. Bincreases turbidity always✓
3. Csoftens water alone✓
4. Dcoagulates alum✓

Backwashing of filters is done to

1. Aremove accumulated solids and restore headroom✓
2. Bcompact sand permanently✓
3. Cdisinfect without chlorine✓
4. Dcoagulate floc✓

Effective size of filter sand refers to

1. Alargest particle only✓
2. Bsize passing 10% by weight in sieve analysis✓
3. Caverage of extremes only without specification✓
4. Ddepth of tank✓

Rapid gravity sand filter removes

1. Aonly dissolved ions without media✓
2. Bonly pathogens without disinfection✓
3. Conly CO2 only✓
4. Dfine suspended particles after sedimentation✓

Surface overflow rate in sedimentation is defined as

1. Aflow divided by plan area of tank✓
2. Bdepth divided by width only✓
3. Chead loss in filter✓
4. DBOD loading✓

Sedimentation tank removes

1. Adissolved salts only✓
2. Bsettleable floc by gravity✓
3. Cgases only✓
4. Dcolour by oxidation only✓

Alum dosage in coagulation depends on

1. Aonly pipe diameter✓
2. Bonly wind speed✓
3. Craw water turbidity, alkalinity and pH✓
4. Donly crop type✓

Flocculation follows coagulation to

1. Arapid mix only without floc growth✓
2. Bfilter without settling✓
3. Cdisinfect without contact✓
4. Dgentle mixing forming settleable floc✓

Coagulation in water treatment uses chemicals to

1. Adisinfect pathogens only✓
2. Bdestabilize colloidal particles for aggregation✓
3. Cadd hardness✓
4. Dincrease colour permanently✓

Design population for water works is projected to

1. Aonly past century✓
2. Bonly one day event✓
3. Cend of design period from current census trend✓
4. Dzero residents✓

Migration significantly affects population forecast in

1. Aclosed static villages only with no change ever✓
2. Buninhabited deserts✓
3. Cnew industrial towns and provincial capitals✓
4. Docean platforms without residents✓

Decreasing growth rate method reflects

1. Asaturation as city approaches limiting population✓
2. Bunlimited exponential growth forever✓
3. Cinstant zero population✓
4. Donly industrial load✓

Geometric increase method assumes

1. Aconstant absolute increase✓
2. Bpopulation never changes✓
3. Cnegative growth always✓
4. Dconstant percentage growth rate✓

Arithmetic increase method of population forecast assumes

1. Aconstant percentage growth✓
2. Bzero migration✓
3. Clogarithmic decline only✓
4. Dconstant absolute increase per decade✓

Design period for water supply project is typically

1. A30 years for components with staged capacity✓
2. B1 day only✓
3. C500 years always✓
4. Dzero planning horizon✓

Peak hourly demand factor relates

1. Amaximum hour flow to average daily flow✓
2. Bonly annual rainfall to runoff✓
3. CBOD to population only✓
4. DManning n to slope✓

Unaccounted for water (UFW) includes

1. Aonly billed consumption✓
2. Bleakage, illegal connections and metering errors✓
3. Conly fire flow✓
4. Donly crop evapotranspiration✓

Industrial water demand is estimated from

1. Aonly canal Lacey formula✓
2. Bonly unit hydrograph✓
3. Conly air quality index✓
4. Dprocess requirements and employee facilities✓

Coincidence factor in water demand means

1. Anot all fixtures operate simultaneously✓
2. Ball taps open always✓
3. Czero night flow✓
4. Dinfinite peak always✓

Fire demand in water supply design is often governed by

1. Aonly irrigation duty✓
2. Bonly sewer infiltration✓
3. Conly rainfall intensity✓
4. Dlargest fire flow plus simultaneous domestic use✓

Average domestic water demand in Indian/Pakistani towns may range

1. A5 litres only✓
2. B5000 litres only always✓
3. C135–225 litres per capita per day for design✓
4. Dzero in cities✓

Per capita water demand depends on

1. Aonly pipe colour✓
2. Bclimate, living standards and industrialization✓
3. Conly dam height✓
4. Donly wind direction✓

Eutrophication in lakes is driven by

1. Aonly sediment deposition without nutrients✓
2. Bnutrient enrichment especially nitrogen and phosphorus✓
3. Conly wind erosion✓
4. Donly chlorine residual✓