Page 169 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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4.3 Water Consumption 131
Table 4.7 Water Losses in Various Cities, 1980–1990

City Water Loss (%)
Toronto, Canada 18
Munich, Germany 12
Hamburg, Germany 2
Hong Kong, China 30
Bombay, India 33
Delhi, India 18
Deagu, Korea 37
Manila, Philippines 51
Riyadh, Saudi Arabia 30
Colombo, Sri Lanka 30
Stockholm, Sweden 19
Kalmar, Sweden 5
Bangkok, Thailand 49
United Kingdom 24
Boston, MA, USA 33
Cambridge, MA, USA 18.5
Springfield, IL, USA 25
Westchester, NY, USA 16
46 Communities in 2–50
Massachusetts, USA

Leakage is detected by (a) driving rods into the ground to test for moist earth, (b) using a
sounding method in which listening devices amplify the sound of running water, (c) conduct-
ing a leak noise correlation that is based on a sonic technique, (d) tracing leaks by injecting a
gas into the network and detecting its escape by a suitable instrument to determine the location
of the leak, and (e) inspecting premises for leaky plumbing and fixtures. Leakage detection of
well-managed waterworks may be complemented by periodic and intensive but, preferably,
routine and extensive water-waste surveys. Generally involved is the isolation of compara-
tively small sections of the distribution system by closing valves on most or all feeder mains
and measuring the water entering the section at night through one or more open valves or
added piping on fire hoses. Common means of measurement are pitot tubes, bypass meters
around controlling valves, or meters on one or more hose lines between hydrants that straddle
closed valves. Table 4.7 summarizes reported water losses ranging from 2% to 50% in several
cities including developed as well as developing countries

4.3.3 Industrial Water Consumption
The amounts of water used by industry vary widely. Some industries draw in excess of
50 MGD (190 MLD); others, no more than comparably sized mercantile establishments.
On average, U.S. industry satisfies more than 60% of its water requirements by internal
reuse and less than 40% by draft through plant intakes from its own water sources or
through service connections from public water systems. Only about 7% of the water
taken in is consumed; 93% is returned to open waterways or to the ground, whence it
may be removed again by downstream users. On balance, industry’s consumptive use is
kept down to 2% of the draft of all water users in the United States. Table 4.8 shows the
relative amounts of water consumed by different industries. Not brought out is the fact
that once-through cooling, particularly by the power industry, is by far the biggest use
component and the principal contributor to the thermal pollution of receiving waters.