26 June exam

What is the peak factor recommended for a population up to 50,000 as per water demand calculation?

• 1.5
• 2.0
• 2.5
• 3.0

Answer explanation

For a population up to 50,000, the peak factor is 3.0 as per environmental engineering standards.

Which method is most suitable for population forecasting in fast developing cities?

• Arithmetic increase method
• Geometric increase method
• Incremental increase method
• Decreasing growth rate method

Answer explanation

The geometric increase method is best suited for fast-developing cities due to its assumption of a constant percentage growth rate.

Calculate the Dry Weather Flow (DWF) for a population of 80,000 with a per capita water supply of 150 LPCD, assuming 80% of water supply becomes sewage.

• 8,000,000 litres/day
• 9,600,000 litres/day
• 12,000,000 litres/day
• 15,000,000 litres/day

Answer explanation

DWF = Population x Per capita water supply x Factor = 80,000 x 150 x 0.8 = 9,600,000 litres/day.

Estimate the maximum hourly flow for a community with DWF of 15 million litres/day.

• 22.5 million litres/day
• 30 million litres/day
• 45 million litres/day
• 60 million litres/day

Answer explanation

Maximum hourly flow = 3 x DWF = 3 x 15 = 45 million litres/day.

Which water treatment process is specifically used for removing colloidal impurities?

• Screening
• Plain sedimentation
• Coagulation
• Filtration

Answer explanation

Coagulation is used to remove colloidal impurities that do not settle naturally.

Which sewer material is most suitable for resisting sulphide corrosion?

• Brick sewer
• Vitrified clay sewer
• RCC sewer
• Cast iron sewer

Answer explanation

Vitrified clay sewers are resistant to sulphide corrosion and are hydraulically efficient.

Which method is used to measure the dissolved oxygen content in water?

• Winkler’s method
• Mohr’s method
• Argentometric method
• Colorimetry using zirconium

Answer explanation

Winkler’s method is the standard procedure for measuring dissolved oxygen in water.

Which sewer joint is most suitable for connecting asbestos cement pipes in flexible curves?

• Spigot and socket joint
• Simplex joint
• Flanged joint
• Collar joint

Answer explanation

Simplex joint is a flexible joint ideal for asbestos cement pipes and allows a 12° deflection.

The primary source of offensive odours in septic sewage is due to:

• Presence of aerobic bacteria
• High dissolved oxygen levels
• Anaerobic decomposition
• Presence of sulphates

Answer explanation

Anaerobic decomposition produces objectionable gases causing offensive odours in septic sewage.

In which of the following systems is a relief vent pipe provided only for water closets?

• Two pipe system
• One pipe system
• Single stack system
• Partially ventilated single stack system

Answer explanation

Partially ventilated single stack system includes a relief vent pipe specifically for water closets.