Page 316 - Water Engineering Hydraulics, Distribution and Treatment

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Chapter 9
Cross-Connection Control
Filter
Flocculation
Static Clearwell
mixer
Figure 9.30 For Problem 9.10.
9.10 Figure 9.30 shows a chlorine feed system at a water treat-
ment plant. What is required between the chlorine feeding cylinders Safety shower
and the chlorine feed points? The same figure also shows that one
chlorine cylinder feeds chlorine to the influent water before chem-
ical flocculation, and another chlorine cylinder feeds chlorine to
the effluent from the filter. What are the technical terms of this
chlorination system for cross-connection control? Can one chlorine
cylinder be used to feed both the influent to the flocculation influent Water Water Acid
and the filter effluent? Please explain.
9.11 Figure 9.31 shows that an air relief valve is piped directly
to a floor drain. Explain the problem and propose a solution.
Mixing tank

Air vacuum release
Figure 9.32 For Problem 9.12.
Gate valve

9.13 A 6-hour pressure–leakage test is performed on 500 ft
(152.4 m) of 8 in. (203.2 mm) plastic pipe with a test pressure
of 150 psi (1,041 kPa). The plastic pipes are 10 ft (3.048 m) long
each. According to AWWA, at 150 psi (1,041 kPa), the allowable
leakage is 1.88 gallons (7.1158 liters) per hour for each 100 joints
for an 8 in. (203.2 mm) plastic pipe. During the 6-hour test period,
Silent check 12 gallons (45.42 liters) of water were added to maintain the 150 psi
(1,041 kPa) pressure. Did the pipe pass the pressure–leakage test?
9.14 The successful promotion of a cross-connection control and
Floor drain backflow prevention program in a municipality will depend on a
legal authority to conduct such a program. Where a community has
adopted a modern plumbing code, such as the National Plumbing
Code, ASA A40.8–1955, or subsequent revisions thereof, provi-
sions of the code will govern backflow and cross-connections. It
Figure 9.31 For Problem 9.11. then remains to provide an ordinance that will establish a program
of inspection for the elimination of cross-connections and back-
9.12 Figure 9.32 shows a direct cross-connection of a potable flow connections within the community. A cross-connection control
water supply line and an acid solution feed line. Propose your ordinance should have at least three basic parts:
solution for the cross-connection control. 1. Authority for establishment of a program