Page 335 - Industrial Wastewater Treatment, Recycling and Reuse

Urban Wastewater Treatment 307

need, urban sectors are coming forward for joint ventures with industry to
share its water potential in the form of treated sewage to industries for cool-
ing water makeup and secondary industrial uses. The urban sectors are
benefitted by reduction in cost incurred for their own treatment and in turn
obtaining revenue for wastewater volume shared to industries. As per the
studies conducted by the Ministry of Environment and Forests (MoEF) pub-
lished in 2009, the comparison of costs of the various sewage treatment tech-
nologies depends upon various factors such as capital costs, operation and
maintenance costs, land area costs, reinvestment, energy, and outputs costs.
Data collected from the various STPs operating in India indicate that WSPs
are operated with lower-cost techniques over the other treatment methods,
3
around Rs. 1 per m , whereas WSPs require higher costs for their land area
2
requirements, around 20,000 m per MLD of wastewater, while the sequence
2
batch reactor requires low land area costs, around 600 m per MLD of sewage,
3
but it operates at high costs for treatment process, Rs. 5 per m . The conven-
tional ASP has moderate costs for the treatment process and in terms of land
requirement for the plants. This is operated at a cost of about Rs. 3.5 per m 3
2
and requires a land area of 2000 m per MLD (Table 7.9).
Apart from domestic sewage, about 13,468 MLD of wastewater is gen-
erated by industries, of which only 60% is treated. In the case of small-scale
industries that may not be able to afford the cost of a wastewater treatment
plant, common effluent treatment plants (CETPs) have been set up for clus-
ters of small-scale industries (CPCB, 2005). The treatment methods adapted
in these plants are dissolved air flotation, dual media filter, activated carbon
filter, sand filtration and tank stabilization, flash mixer, clariflocculator, sec-
ondary clarifiers, and sludge drying beds. Coarse material and settable solids
are removed during primary treatments by screening, grit removal, and sed-
imentation. Treated industrial wastewater from CETPs is mixed and dis-
posed of in rivers. For example, 10 CETPs from Delhi with capacity of
133 MLD discharge their effluents into the Yamuna River.
The conventional wastewater treatment processes are expensive and
require complex operations and maintenance. It is estimated that the total
cost for establishing a treatment system for all domestic wastewater is around
Rs. 7560 crores (CPCB, 2005), which is about 10 times the amount that the
Indian government plans to spend (Kumar, 2003). Table 7.9 illustrates the
economics of different levels of treatments through conventional measures
(CPCB, 2007). Sludge removal, treatment, and handling are the most
neglected areas in the operation of STPs in India. Due to improper design,
poor maintenance, frequent electricity breakdowns, and lack of technical