Thermal Power Station, Khaperkheda, Nagpur, India
Thermal power station is the largest consumer of water. In a thermal power station water is the most important raw material which is used for various purposes, such as cooling water, boiler feed water, ash transportation, fire fighting, potable water, etc., At Khaperkheda Thermal Power Station the use of soft water for cooling purpose and for boiler feed water, demineralised water (D.M. Water) for steam generation is produced through various unit operations. The daily requirement of cooling water (soft water) makeup is approximately 20,000 m3/day and boiler feed water (D.M. Water) makeup is 600–700 m3/day (Stage I - 2 x 210 MW).
For the production of cooling water (soft water) and boiler feed water (D.M. Water) the raw water is pre-treated in the clariflocculator and gravity filters. The raw water from one day reservoir goes to the clariflocculator where the required quantity of lime, ferric alum, bleaching powder and poly-electrolytes are added. The suspended particles and colloidal particles get agglomerated and settle down in the clariflocculator in the form of sludge.
The clarified water flows through the gravity filter. The residual suspended solids are retained on the surface of filter media. Which results in the drop of the filtration rate. On backwash of gravity filter, the waste produce was analysed and compared with the results of raw water. The backwash waste is superior than the raw water hence, it is suggested that this waste should be recycled to the clariflocculator. This will result in the saving of 438,000 m3 water/year
