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Water Quality / Pollution
 
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Keeping in view the key role played by SSI units and the constraints in complying with pollution control norms individually by these units, the Ministry of Environment and Forests (MoEF) initiated an innovative technical and financial support scheme to ensure their growth in an environmentally compatible manner. The scheme promoted common facilities for treatment of effluents and treatment and disposal of hazardous solid waste generated from SSI units located in clusters through liberal financial assistance.

The CETP scheme was instituted initially for a period of 10 years with effect from the year 1991 but MoEF has decided to continue financial assistance under the scheme beyond this period. Most of the CETPs constructed and commissioned so far were financed under the CETP scheme of Govt. of India.

Central Pollution Control Board studied performance of 78 CETPs operating throughout the country during 2002-2005 and published a report – “Performance Statuss of Common Effluent Treatment Plants in India ”.

 
Performance status of 78 CETPs studied by CPCB during 2002-2005
State Number of CETPs studied by CPCB CETPs complying pH, BOD, COD, TSS and TDS standards CETPs complying pH, BOD, COD and TSS but not complying TDS standard
Number Name Number Name
AP 2 0   0  
Delhi 10 3 Mayapuri, GTK, Badli 6 Wazirpur, Mangolpuri, Jhilmil, SMA, Nangaloi, Okhla I.A
Gujrat 15 0   2 Ankleshwar, Sachin (0.5MLD)
Haryana 1 1* Kundli-I 0  
Karnataka 2 0   1 Pai&Pai
Maharashtra 9 0   3 Thane-Belapur, Ambernath, Patalganga
MP 1 0   0  
Punjab 1 1 Phillore 0  
Rajasthan 5 0   1 Jodhpur **
Tamilnadu 29 0   2 Thiruvai Karur***, TALCO Ambur Thuthipet
UP 3 0   0  
Total 78 5 (6.4 %)   15 (19.2 %)  

*TDS not determined but likely to be within limits; **CETP was under trial; TDS not determined but Cl exceeded;

***TSS not determined

The report gives following recommendations:
  • In general, the performance of CETPs has been found to be very unsatisfactory, largely because of poor operation and maintenance. Therefore, the State Pollution Control Boards should conduct regular monitoring of CETPs and persuade them to ensure proper operation and maintenance failing which they should initiate action against negligent agencies and wilful defaulters.
  • Achieving standards for treated effluent quality from CETPs is dependent on meeting the designed criteria of inlet quality to the CETPs that inter alia depends on effluent quality from each industry. The State Pollution Control Boards are required to prescribe standards for discharge effluent to CETP from each industry and enforce the same.
  • Optimization of neutralizing/coagulating chemicals is very important for deriving maximum benefits from primary treatment units based on physico-chemical treatment, minimizing sludge production and reducing pollutants' load on subsequent biological treatment units. Jar tests should be conducted on daily basis to decide type of coagulant and their dozing.
  • CETP operating agencies should engage experts to advice them from time to time for proper operation and maintenance of CETP besides employing skilled manpower.
  • High TDS in the raw influent reaching CETPs and, as a result, in treated effluent of CETPs is a major cause of concern, more so because it is generally caused by high salinity which requires costly treatments such as Reverse Osmosis (RO) and Nano Filtration Systems followed by Multi Stage evaporator systems (MSES) . Area specific thoughtful approach is required to tackle this problem. First attempt should be reduction in release of TDS contributing chemicals from problem industries by adopting cleaner production technologies and recovery and recycling of chemicals from the waste streams. Second option should be treatment of waste stream for TDS at the level of individual industry. Treatment of TDS at the CETP should be the last option unless some special conditions demand so. State Pollution Control Boards should investigate all the TDS related problem areas and compel the industries/CETPs for its solution.
  • The State Pollution Control Boards may consider prescribing location specific regulations for the control of TDS at the industry level. Setting time limits in future for compliance of new regulations, compliance of which requires significant investment, is an industry-friendly and effective approach. The same approach is suggested for prescribing location specific regulations for the control of TDS at the industry level.
  • Capability and limitations of filter unit in a wastewater treatment scheme, as explained in section 3.11, must be kept in mind while using these units wherever they exist in CETPs
    ( 3.11: Dual Media Filter (DMF) unit, which has been employed in treatment schemes of CETPs in Delhi and at few other places and sand filter unit which has been employed in CETPs of textile units in Tamilnadu are normally used to improve suspended solids level from near 50 mg/L in primary settling unit's effluent to near 10 mg/L. Incidentally, it also reduces the organic matter associated with the suspended matter so removed. It may also remove a small fraction of organic matter associated with colloidal matter that is coagulated and filtered during filtration. Filter units should not be depended upon to perform more than the expected function, as explained. If DMF unit or a rapid sand filter unit is over loaded, it will require frequent backwashing. )
  • Capability and limitations of activated carbon bed, as explained in section 3.12, must be considered while including it as a terminal treatment unit in wastewater treatment. In treatment schemes that already include activated carbon bed as terminal treatment unit, the dependence on this unit should be based accordingly.
    ( 3.12: Activated Carbon Filter (ACF) unit, which has been employed in treatment schemes of CETPs in Delhi and at few other places is only meant for removing trace organics, such as pesticides, phenols, etc., and heavy metals, which escape the primary treatment and therefore should not be loaded with bulk organic matter. If any treatment scheme, with ACF as its terminal treatment unit, is aimed at achieving an overall efficiency so as to give the final effluent quality of BOD<30 mg/L and COD<250 mg/L, then ACF unit is most likely to be subjected to high COD, or even high BOD, thereby resulting in an early exhaustion of its activated carbon bed. Therefore, in treatment schemes aimed to achieve this quality, ACF as a terminal treatment unit can be said to be a misfit because very frequent replacement or regeneration of the bed is neither easy nor economically affordable. )  
  • Operation of treatment units based on biological treatment (Activated Sludge Process) is sensitive and requires understanding of important controlling parameters. Use of Solid Retention Time (SRT), the ratio of solids in the system and solids wasted per day, as controlling parameter is recommended because it is most simple and treatment efficiency, sludge production, oxygen requirements and nutrients requirements are dependent on SRT.
  • Collection of wastewater from individual industries through tankers is not a foolproof system and should be discouraged in new areas and reviewed and rectified in old ones by the SPCBs unless it is technically impossible.