Environmental Engineering Reference
In-Depth Information
pipe walls, which depreciate water quality, and (2) it would make much more
sense, cost-wise and water-quality-wise, to switch to use of separate systems. This
would permit use of much-smaller-diameter piping in the distribution system for
delivering potable water, and resulting in much reduced residence time — hence
much lesser organic growths — and making it feasible to utilize stainless steel for
the drinking water piping, which would greatly reduce the problem of pipe leak-
age due to corrosion. It would also permit unrestricted use of reclaimed water for
firefighting purposes. Despite these arguments, little interest in such systems has
been expressed in the ICs and virtually none in the DCs. Some DC cities such as
Calcutta still utilize dual systems, but, unfortunately, the water for the firefighting
mains is untreated water drawn from the local river, which is replete with cholera
virus, and these mains have been commonly tapped to furnish drinking water for
the plentiful urban poor, who often have no place to sleep except on the city
streets
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. Hopefully, the recent ADB-sponsored project for improving this situa-
tion in Calcutta will ensure continuing disinfection of the water in the firefighting
mains.
Overdrafting of Groundwater and Ground Subsidence
Overpumping
of groundwater is an all-too-common practice in many DCs where the UWSSs
systems depend on use of groundwater as a major source and where the demands
by increasing population and industry have resulted in very serious damages.
This includes deterioration of the groundwater quality due to infiltration into
the fresh groundwater basin from adjacent salinity groundwater basins, and very
serious subsidence of ground levels. Outstanding examples are the situations in
the Bangkok metropolitan area
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and at Taiyuan in China
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. The only solution is
for the DC governments to sponsor much better use of the local freshwater plus
importing freshwater, thus enabling elimination of groundwater overdrafting.
The situation of the “too little/too late” approach is the situation at Bangkok,
where the seriousness of the subsidence become obvious in the 1970s, but even
now the government's importation program has enabled closing of wells only
in limited areas. Hence, subsidence (now more than 2 meters in some areas)
continues in much larger (and heavily industrialized) areas. And at Taiyuan, the
situation is almost comical in that the Chinese government, with World Bank
support, recently completed an importation system (300 km of aqueducts, tun-
nels, pumping plants) that does bring in the needed extra water, but without
provision of firm administrative mechanics (i.e., without establishing a local
“water czar” with power to control all water uses in the municipal area, includ-
ing wastewater treatment/reuse), and as a result, industries continue with more
overdrafting to avoid paying the extra costs for buying the expensive imported
water
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.
Water Hyacinths
Situation in ICs
Water hyacinth growth in waterways has been a serious
problem in virtually all tropical regions, including the tropical areas in the United
