WATER & WASTEWATER ENGINEERING Water Supply Engineering

Lecture No. 3

Surface Water Collection Works

Water Supply System

• Components1. Collection Works 2. Purification Works3. Distribution Works

River

LLP Intake

Mixing Flocculation

Sedimentation Filtration

Disinfection

Pipe Network

HLP

Water Treatment

Plant (WTP)

Collection Works• 1. Intake Structure The basic function of the

intake structure is to help in safely withdrawing water from the source and then to discharge this water into the withdrawal conduit (normally called intake conduit), through which it flows up to water treatment plant(WTP).

• 2. Sump In which water is collected to be pumped to water treatment plant.

• 3. Pump Through which water is pumped to water treatment plant.

Collection Works

• Intakes consist of the opening, strainer and the conduit conveying the water , usually by gravity, to a well sump.

• From the well the water is pumped to the treatment plant

Intake Types

Factors affecting choice of intake type: 1. Water width 2. Water depth 3. Navigation 4. Fluctuation in water level

Intake Types

1- shore intake2- pipe intake3- Tower intake4- submerged intake

Factors Governing Location of Intake

1. At a straight part of the canal to avoid silting and scouring zones.

2. Upstream any source of pollution. 3. Fix a prohibited area 150 m upstream and 50

m downstream the intake location.4. Away from the surface to avoid floating

materials and away from the bottom to avoid fine materials.

Design of Shore Intake

• Design capacity: pop. × qav. × 1.4 × 1.1Qd = 1000 × working hrs of LLP × 60 × 60Design of intake conduit:Qd = A × V × no

Assume V = 1 m/sec.

Then, Qd = (ΠD2/4) × 1 × no Get D, V actual

No. of intake conduits < 2

Design of Shore Intake

• Design of sump:Qd = V / T Assume T = 5 - 15 min.V = Qd × T Get V V = L × B × d Assume d = 1 . 0 - 3 . 0 m L = n × S

Get B

n: no. of pumps S = 2 - 3 m

B < 2 m

Design of Shore Intake

Design of Pump House: Dimensions • L1 = L + 2 m

• B1 = L1 / 2

Pumps • HP = γ × Qd × Hm

75 × η • Hm = Hd + Hs

γ = 1 Q= Lit γ = 1 Q= m3/sec

Qd= 1.4 Qavg

Design of Shore Intake

• Hd is the height from mixing tank W.L to the axis of the pump

• Hs is the height from the axis of the pump to the W.L of the sump

Hm ≈ 3m at least

Design of Shore Intake

• Σ losses = Screen losses + Hfriction + inlet & outlet losses

• Screen losses = 0.1 m • Hfriction = 4 × f × L × Vact

2 ( Intake conduit)

2 × g × Dcom

• Inlet & outlet losses = 1.5 × Vact2 2 × g

L= (30-70) cm