Introduction 3Conventional waste treatment is rarely linked to waste reuse, such as irrigation,
fertilization, or aquaculture. Thus it does not generate either income or
employment, both high priorities in developing countries.
Most obviously, sewers are simply too expensive. The cost of sewers and
sewage treatment is high by the standards of the richest countries in the world. Not
only are many of the cities in the developing countries larger, but an unprecedented
number of people must be provided with hygienic sanitation in an extremely short
time. The developed countries had the luxury of almost a century to build their
sanitation systems, the developing countries must do it in a decade, on a larger
scale, often with water shortages, in extremely densely populated cities, and
sometimes with a lower level of technological development than existed in Europe
and North America at the turn of the century. And this must be done at a cost that is
affordable today.
Bangkok city, the capital of Thailand, is a typical case study to show the
difficulty of implementing sewerage scheme in a newly industrialized country. In
Bangkok, excreta disposal is generally by septic tank or cesspool; other
wastewaters from kitchens, laundries, bathrooms, etc. (grey water) are discharged
directly into nearby storm drains or canals. Because the Bangkok subsoil is
impermeable clay, overflows from septic tanks and cesspools normally find their
ways into the canals and storm drains, resulting in serious water pollution and
health hazard to the people. A master plan of sewerage, drainage and flood
protection for Bangkok city was completed in 1968; the required facilities to serve
approximately 1.5 million people would cost about US$110 million. By the year
2000, the entire program would serve about 6 million people at a cost in excess of
US$500 million. The proportions of cost by facility were: sewerage 35 percent,
drainage 27 percent, and flood protection 38 percent (Lawler and Cullivan 1972).
Since the year 2006, seven central wastewater treatment plants, which employ
primary and secondary treatment processes, are in operation and costing about US$
500 million in construction. They are able to treat 40 % of the total wastewater
volume or about 1 million cubic meters per day. The remaining wastewater, raw or
partially treated, is being discharged into nearby storm drains or water bodies.
Besides the sanitation problem, man's energy needs have also grown
exponentially, corresponding with human population growth and technological
advancements (Figures 1.1 and 1.2). Although the energy needs are being met by
the discovery of fossil fuel deposits, these deposits are limited in quantity and their
associated costs of exploration and production to make them commercially
available are high. Figure 1.2 shows the world fuel energy consumption to increase
almost linearly since 1970 and is projected to be more than double in the year 2025.
The worldwide energy crisis in the 1970s and very high oil prices in the 2000s are
examples to remind us of the need for resources conservation and the need to
develop alternative energy sources, e.g. through waste recycling.