Page 312 - Industrial Wastewater Treatment, Recycling and Reuse

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of the sewage. In India, the domestic consumption of water is rising practically
at the same rate as that for industrial water and is likely to triple between 2000
and 2050. Further, only 31% of the sewage wastewater generated from the
metro cities is treated, and thus untreated sewage is a major factor contributing
to severe water pollution. The available data on the major metro cities indicate
sewage wastewater generation of 38,400 MLD (Million Litres per Day) with
sewage treatment capacity of only 12,000 MLD. It is believed that apart
from these metro cities, the treatment facilities for sewage waters in other cities
could be as low as 10% or even less.
The untreated sewage waters largely find their way out through the rivers
close by. The Central Pollution Control Board (CPCB, 2005; CPCB,
2010), India, has identified polluted regions in 18 major rivers and, not sur-
prisingly, these are located close to urban areas (water bodies with BOD
higher than 6 mg/L are considered polluted). The data on river pollution
indicate severe pollution in many of the major rivers and nearly 14% of total
river length is believed to be severely polluted in India, 20% being
moderately polluted based on the BOD levels. Apart from high BOD
and COD levels, high levels of heavy metals, arsenic, fluorides, and hazard-
ous chemicals are also found in many places, especially in groundwater.
In recent years, a number of technologies have been made available, espe-
cially using biological treatment methods for sewage wastewaters. These are:
1. Membrane bioreactor (MBR)
2. Fluidized aerobic bed
3. Fluidized aerated bed reactor
4. Submerged aeration fixed film reactor
5. Biological filter oxygenated reactor
6. Anaerobic filter
7. Expanded granular sludge blanket
8. Sequencing batch reactor
9. Up-flow anaerobic sludge blanket (UASB).

7.2.1 Water Requirements of the Urban Population

It is estimated that about 50 billion liters of municipal water is required every
day based on the urban Indian population, which accounts for about 360
million people. By 2050, the urban population will exceed around 850 mil-
lion, and the estimated water requirements will be around 110 billion liters
per day. The rural population, which is estimated to be around 1.1 billion in
2050, will require about 44 billion liters per day (CWC, 2005). Annually,