In a power station, effluent is generated from water treatment plant, boiler blow down, drains from heat exchangers, canteen waste water, rain water etc.

Waste water from water treatment plant is treated in neutralising pits. Boiler blow down and various other contaminated water quantities are made to pass through Efficient Treatment Plants (ETP) for separation of oil and suspended particles. Sludge water is discharged into a sludge pond for settling of sludge. Canteen waste water treatment plants have also been set up.

Finally, effluent quality is monitored and controlled to meet the effluent standards set by the Central and State Pollution control Boards, prior to discharge.Recycling of Effluents of the PF fixed power stations

RECYCLING OF EFFLUENTS OF THE PF FIRED POWER STATIONS

Coal, when burnt in boilers with the help of air, produces flue gas which is discharged in the atmosphere. This flue gas contains Nitrogen, Oxygen and Oxides of Carbon, Sulphur (SOx), Nitrogen (NOx), etc. It also carries the suspended ash particles (SPM). Most of these ash particles, however, get separated from the flue gas when  it passes through Electrostatic Precipitators (ESP) and get collected in the hoppers as fly ash. SPM, SOx and NOx in the flue gas are monitored by the stations ,recognizes external agencies as well as by the Pollution Control Board.  

CESC maintains a mobile laboratory for stack gas and ambient air monitoring,which moves between all the stations to measure and monitor stack gas and ambient air.

At Budge Budge on-line measuring facilities are available which facilitates monitoring on a continuous basis.

In PF fired boilers, a major portion of the ash is collected as fly ash, in the ESP hoppers and the rest as bottom ash collected in the boiler hoppers known as Bottom Ash Hoppers.

Dry fly ash is conveyed pneumatically to ash silos from where it is unloaded, after proper moistening, on dumpers for disposal. Fugitive emission is thus controlled. Bottom ash is pumped into de-watering bins in the form of slurry. The water from the slurry is separated by decantation and recycled to form ash slurry. This “zero discharge” system in handling bottom ash thus gives rise to no effluent at all. .

In older stations, ash from the boiler in the form of cinders is led to ash hopper where it is quenched by water and fed to ash conveyer belt by paddle ash extracter. This wet ash is conveyed to ash silos for disposal.  

In all power stations, except Budge Budge Generating Station, cooling water for condenser is taken from the Hoogly river and discharged back to the river without altering its quality.

Budge Budge cooling towers have been installed for cooling the condenser cooling water. A portion of this water which is blown down to maintain the water quality, is recycled to be used as service water.

For suppression and control of fugitive emission in coal handling plant, a dust extraction system together with water spraying at transfer and unloading points has been provided. Fugitive emission tests are also carried out periodically by the authorised agents.  

Intensity of noise is measured at regular intervals and records are maintained. Immediate necessary action is taken whenever the level at any place approaches the statutory levels.  

Each power station takes special care for developing and maintaining green belt along the boundary as well as in the vacant land
within the site.  

To keep the power stations clean and arouse competitiveness, awards for best house keeping have been introduced.  

CESC has an Ash Utilisation Division for implementation of comprehensive ash management plan on global technology search to tackle ash utilisation on short, mid-term and long-term basis.

Presently, major usages are for land reclamation, structural land filling and road making by Government and Semi-Government Bodies.
Rest is being used by local conventional brick fields . CESC is committed to supply fly ash free of cost to brick makers within 5 Km radius of the power plants and also to pay incentives to ash evacuation contractors who supply ash to users for commercial utilisation. Additionally, setting up of a centralized Ready-Mix Plant for mixing coal ash and clay (silt) Patulia near Titagarh Power Station, which would utilise ash for making bricks will commence shortly.

Stretches of road with technical guidance from the Central Road Research Institute, Govt. of India have been constructed using coal ash on experimental basis. And now considerable quantity of ash is being utilized to construct the road sub-base by Calcutta Metropolitan Development Authority for Dum dum Barackpur Highway Project, Eastern Metropolitan By-pass and also for landfill of Rajarhat New Township near Calcutta.CESC has entered into a long term agreement with Ambuja cements who utilizes the total fly-ash generated by Southern Generating station  for making of cement.

Further, CESC has entered into a firm agreement with a Dutch Consortium M/s LIWAG b. v. of Netherlands to set up a coal ash based sintered light weight aggregate (LYTAG) Plant near Budge Budge Thermal Power Station, to utilise about 1000 Tonnes of coal ash daily on a long term basis.Fly-ash from Budge Budge is now being exported to Bangladesh for cement making.

CESC is in the process of introducing an eco-friendly High Concentrated Ash Slurry Disposal (HSCD) system in transportation to its emergency ash disposal area at Budge Budge Power Station. Because of very quick solidification of the slurry at the disposal site, the process offers no air or water pollution during disposal.

CESC is also utilising the services of Bidhan Chandra Krishi Viswavidyalaya, a premiere Agricultural University for utilisation of coal ash in agriculture, with an ultimate aim of developing a soil amendment for growing edible and nonedible plants. Experimental farming showed satisfactory results.  

To strengthen the efforts, implementation of Environment Management System ISO:14001 has been initiated in Southern Generating Station which will be further extended to other units gradually.  

To create awareness and sustain the efforts, training programmes on “Pollution Control and Environmental Monitoring in Thermal Power Stations” are being conducted regularly for all levels of employees. World Environment Day is also observed in the Generating Stations and participated by all employees, when environment- friendly tree saplings are planted.

Rewards & Recognitions

The Southern Generating Station has won the 2nd Jawaharlal Nehru Memorial Award for implementing zero discharge system. It has also won CII(ER) Safety Awards for two consecutive years.

Conclusion

CESC’s environmental management system focuses on continuous improvement and upgradation, with state-of-the-art principles and equipment, setting high targets and reviewing its performances. CESC recognises its responsibility towards protecting the ecology, health and safety of the employees and consumers.