Highlights 2003

Hon'ble Supreme Court of India while hearing the Writ Petition "News Item on Maili Yamuna WP(C) 725/1994 and WP(C) no. 561/1994 on 24.09.2003, referred Central Pollution Control Board (CPCB) to inspect sewage treatment plants (STPs) in Delhi to verify the contents of the hearing held with Delhi Jal Board with respect to utilization of sewage treatment capacity and its performance. In compliance to the above order, Central Pollution Control Board carried out an inspection on performance evaluation and capacity utilization of all the thirty STP,s situated in Delhi during November-December 2003. The study was carried out through monitoring round the clock. Flow based composite samples were collected from the inlet and outlet of each of the STPs by mixing 3 hourly grab samples proportionate with the flow for 24 hours. The grab sample was also taken every three hours for 24 hours for analysis of COD and TSS in order to evaluate the diurnal variation in the quality of influent and effluent from each of the STPs. The composite samples were analysed for pH,TSS, conductivity, COD, BOD, Total and Faecal Coliform counts (TC & FC). The observations are as follows:

· There are 30 STPs located at 17 locations in Delhi.
· Three STPs (Ghitorni, Rohini and Keshopur I) were not found in operation at the time of inspection/monitoring.
· The total combined treatment capacity of all the STPs was observed as 2330 mld.
· The actual treatment of sewage during November-December 2003 was only 1478 mld. About 63% of the treatment capacity.
· Out of total STPs, 20 STPs are running under capacity, 5 STPs are running over capacity, 3 STPs are non functional while only 2 STPs are running to their capacity.
· Most of the STPs (21 Nos) are based on activated sludge process, three STPs are based on extended aeration process, two on high rate bio-filters, one on Trickling filters and one on UASB process based.
· Most of treatment plants working on activated sludge process, do not perform satisfactorily due to erratic F/M ratio.
· An attempt was made to evaluate the performance of the STPs in terms of percent reduction in pollution load. Average reduction in BOD, COD and TSS load computed based on the study was 86%, 79% and 91% respectively.
· It was also observed that the sludge generated from the STP's is not lifted fully from the sludge drying beds and as such flows out from sludge drying beds mix with the effluents and finds their way to Yamuna River.
· Little emphasis has been given to the sludge digestion and its utilization for biogas (methane) and manure. Only, Okhla STP and one unit at Rithala STP is collecting gas in gasholders and being utilised in electricity generation. Papankalan Sewage Treatment plant is flaring off the gas and not utilizing for useful purpose. All other plants are neither using sludge digester properly nor the gas is being collected for beneficial purposes.
· It is estimated that out of 3167 mld of sewage generated in Delhi, the treatment capacity is existing for 2330 MLD of sewage (74% of total sewage generation). However, actual treatment is received to only about 1478 mld (63%) of sewage in terms of BOD load. Out of 443 tonnes/day of BOD load generated in Delhi, 227 tonnes/day (or 51%) is reduced due to treatment.

Sl. No	STP’s Capacity (MGD)	Design capacity (MLD)	Actual flow (MLD)	Type of STP	Present Status
1	Coronation Pillar STP’s (10) (10+20)	45.46 45.46 90.92	40.87 63.46 56.55	Activated sludge process (ASP), Trickling filter & ASP	Over the Designed Capacity Under Utilized
2.	Delhi Gate (2.2)	10.00	10.00	High rate biofilters (Densadeg technology	Running on designed capacity
3.	Ghitorni (5)	22.73	Nil	-	Not in operation
4.	Keshopur STPs (12) (20) (40)	54.55 90.92 181.84	46.55 95.10 106.46	All three plants designed on activated sludge process	12 MGD not running properly sewage passes through PST. Not running Over the Designed Capacity Under- utilized
5.	Kondli STP’s (10-Phase-I) (25 -Phase-II) iii. (10-Phase-III)	45.46 113.65 45.46	56.55 57.96 28.36	All three activated sludge process	Over the capacity Under- utilized Under- utilized
6.	Mehrauli STP (5)	22.73	4.95	Extended Aeration	Under-utilized
7.	Najafgarh STP (5)	22.73	2.27	Activated Sludge Process (ASP)	Under- utilized
8.	Nilothi STP (40)	181.84	15.0	Activated Sludge Process (ASP)	Under- utilized
9.	Narela STP (10)	45.46	2.50	Activated Sludge Process (ASP)	Under- utilized
10.	Okhla STP’s (12) (16)) (30) (37) (45)	54.55 72.73 136.38 168.20 204.57	39.09 40.91 136.98 159.11 181.84	All the plants designed on Activated Sludge Process (ASP)	Under- utilized Under- utilized Running in capacity Under-utilized Under-utilized
11.	Papankalan STP (20)	90.92	37.73	Activated sludge proc.	Under-utilized
12	Rithala STP’s (40) Old (40) New	181.84 181.84	46.28 185.07	ASP UASB	Under-utilized Over the designed capacity
13.	Rohini STP (15)	68.19	Nil	Activated sludge process (ASP)	Not in operation
14.	Dr. Sen N.H. STP (2.2)	10.0	10.0	High rate Bio filter	Running on designed capacity.
15.	Timarpur O.P. (6)	27.27	4.79	Oxidation ponds	Under-utilized
16.	Yamuna Vihar STP’s Ph-I(10) Ph-II(10)	45.46 45.46	27.27 14.77	Activated sludge process	Under-utilized Under-utilized
17.	Vasant Kunj STP’s (2.2) (3.0)	10.00 13.63	3.18 4.36	Both Extended aeration	Under-utilized Under-utilized
	Total	2330	1478	-----	-----

Performance evaluation of four CETPs was carried out, one each at Mathura, Kundli (Sonipat) Unnao and Kanpur. The performance of individual CETPs are depicted below:

With change of process technology of the member units (sari printing) from earlier cotton to present synthetic, the hydraulic loading and the characteristics of influent at CETP has significantly changed. This has adversely affected the plant performance. As a whole the plant operates at less than 50% over-all efficiency. There are high content of oil in the raw effluent. The overall apathy of management in plant operation is also an important factor in poor maintenance and increased cost of treatment.

This plant exhibits reasonably satisfactory performance in term of designed efficiency with observed removal efficiency of COD, BOD and SS being 88%, 96% and 92% against 94%, 98% and 95% designed. However the inlet characteristics are diluted in terms of organic loadings and on the other hand contain equally high chromium.

This plant is poorly affected due to several factors which include poor operation, non-operation of primary treatment by member units (tanneries), disposal of chromium-rich solid waste/sludge in conveyance system and improper payment of treatment cost by tanneries as well as Municipal Corporation. Such factors are adversely affecting the plant performance and have resulted in poor state of treatment economics. As such the plant operates on 66%, 69% and 94% removal efficiency of COD, BOD and SS respectively against 82%, 84% and 88 % designed.

The plant is in utterly bad state, which has resulted from lack of co-ordination between the Industries' association and the members. The mis-match in the treatment cost projected at the conceptualization stage and the one after the plant was operational was so serious, as to cause liquidation of the Industries' association. Presently the plant is operated on contract by an agency engaged by HSIDC. As observed the backing-out of members, lack of enforcement activities, poor state of maintenance has substantially increased the treatment cost, which no-one agrees to share. Although the plant achieves the designed efficiency of treatment, yet the intermittent / irregular flow, diluted inlet characteristics and by-pass of polluted combined effluent have defeated the purpose of the CETP, for which it was conceptualized.

Performance evaluation of Sewage Treatment Plants at Varanasi, Mirzapur and Allahabad

Central Pollution Control Board with the financial assistance from National River Conservation Directorate (NRCD) is undertaking performance evaluation of the five Sewage Treatment plants in Allahabad, Mirzapur and Varanasi every month. The specific observations over past two years are as follows:

¨ The treated sewage do not conform to the discharge standards for river, specially in winter.. The performance of STP has decreased in year 2003 with respect to year 2001 particularly during summer. The Coliform contents are however appreciably high, as there is no provision for its control/treatment.
¨ The low MLSS contents and further lower content of its organic proportions (MLVSS) are indicative of the plant, yet not being properly stabilised. This may however be due to dilute inlet characteristics.
¨ The gas generation is much below the designed level and that too is not utilized optimally

Mirzapur Sewage Treatment Plant

¨ The coliform content are appreciably high as there is no provision for its control/treatment.
¨ The performance of STP in year 2003 is more or less at par with respect to year 2001. It has been noted that gas meter is not functional for the last three years.
¨ The plant lacks in optimal utilization of Biogas, which is merely flared.

Bhagwanpur Sewage Treatment Plant (Varanasi)

¨ The plant was non-operational for around 6 months due to maintenance. This needs to be planned properly so that the entire plant is not taken offline at a time
¨ In consideration of designed maximum hydraulic loading of 8 MLD the plant receives 1.5 - 2 times higher flow.
¨ High hydraulic load and diluted characteristics indicate a significant dilution.

¨ The treated sewage do not conform to the discharge standards with respect to total suspended solids (TSS) for river. The performance of STP has deteriorated in year 2003 with respect to year 2001 particularly during summer. The Coliform contents are however appreciably high.
¨ Proper provision for quantifying the gas generation, use and flaring has to be made. In consideration of designed maximum hydraulic loading of 80 mld, the plant receives 1.5-2 times higher flow.
¨ The aeration and sludge recycling/wastage require a better optimization necessitated by the observation, wherein, high MLSS and low to "nil" DO has been observed.
¨ The trickling filters in particular are poorly maintained, as obvious from their "contributing" BOD and SS, which may be due to excessive growth of microbial film over the gravels .
Diesel Locomotive Works (DLW) STP (Varanasi)
¨ In consideration of designed maximum hydraulic loading of 12 MLD, it has been observed that plant always receives lesser flow. The pumping of sewage to the plant has also been irregular.
¨ Input (raw sewage) characteristics are appreciably diluted and are not conducive for proper & sustainable bacterial population, thus rendering the treatment process a meaningless exercise.

Survey and monitoring was carried out in Daman and Silvassa Union Territories to work out the magnitude of problems and characterization of the effluent generated by different types of industries to understand the sources of effluent, their characteristics and common problems associated with treatment and disposal of the effluent. The study revealed that the most of the small scale industries are not operating the wastewater treatment plants scientifically. The small-scale industries are not having skilled and trained manpower for operation and maintenance of treatment and disposal system. Due to non-availability of receiving bodies in UTs, almost all the small-scale industries are given zero discharge condition and therefore, the industries are treating and disposing the wastewater for gardening purpose. Continuous use of the treated/partial treated wastewater for gardening purpose can definitely have adverse impact on the groundwater quality of the area. The development of infrastructure like CETP for collection, treatment of the wastewater generated and its proper disposal into deep sea with diffuser system could be the best probable solution to resolve the problem.