Page 340 - Industrial Wastewater Treatment, Recycling and Reuse

312 Industrial Wastewater Treatment, Recycling, and Reuse

Lime coagulant
Secondary-wastewater made suitable for discharge (can have polyelectrolyte
significant modifications for cost reduction)
Balancing Aeration Secondary Intermediate
pond tank clarifier storage pond Clarifier
Primary-wastewater made
suitable for further treatment
Sludge
thickener
(chemical)
Bio sludge
Chemical sludge Filtration
Pressure sand
CaCO 2 sludge filters
CaCO 3
thickener

Cl 2
NH 3
Pressure
Ammonia Carbonation CaCO 3 Breakpoint
stripper tower clarifier sand chlorination
filters
Air CO 2
Overall
concern-
Multimedia Cartridge Reverse Permeate Recycle & total cost &
filters filters osmosis reservoir reuse sludge
disposal
Tertiary-wastewater made suitable
Na 2 HSO 3 Na 2 HSO 3 Reject for
disposal for recycle & reuse
Figure 7.7 Flow sheet of the 12 MLD tertiary treatment plant (TTP) for Madras Refineries
Ltd., Chennai. Data from MoEF (2011).

• Chemically aided settling+pressure filtration+ammonia stripping, car-
bonation, clarification, pressure filtration
• Chlorination
• Sodium bisulfate dosing
• Multimedia filtration
• Cartridge filtration
• Reverse osmosis
• Permeate for reuse.
The rejects containing high TDS (Total DissolvedSolids) aredisposedof in the
sea through a submerged outfall. As per the 1991 estimate, the capital cost for
building the MRL plant was around Rs. 24 crores. The treatment costs for the
MRL plantare reportedto beabout Rs.35per 1000 L ofwater, which ismuch
lowerincomparisontothechargeofRs.60perlitersforfreshwatersuppliedto
industries.TheChennaiMetroWaterandSewerageBoardalsochargesamuch
higher tariffrate ofRs. 5.2 per1000 L of waterto coverits treatmentcosts up to
secondary stage. It is to be noted that the overall treatment scheme here has