A Comparative Study of Sewerage Treatment Plants With Different Technologies In The Vicinity Of Chandigarh City

Abstract

Chandigarh city has a well planned underground network of pipes for the disposal of sewerage generated in the city. The sewerage system of the city has been designed by taking into account the natural slope of the city, which is from north to south. Chandigarh city hosts three Sewerage Treatment Plants (STP's) namely: STP Diggian located at sector 66 of S.A.S Nagar, Punjab Territory, Mohali, based upon MBBR (Moving Bed Biofilm Reactor) technology which is at a distance of about 4km from the nearest planned sector 47, STP Raipur Kalan located at a distance of 6km from Chandigarh adjoining to railway station based upon UASB (Upflow Anaerobic Sludge Blanket) technology and STP Raipur Khurd, based upon ASP (Activated Sludge Process) technology located on Chandigarh-Ambala highway at a distance of approximately 8 km from Interstate Bus Terminal sector 17, 1 km from Airport and 3 km from Railway Station. These plants are designed and constructed with an aim to manage waste water so as to minimize or remove organic matter, solids and other pollutants before it enters a water body. In the present study various Physico-Chemical and Biological Parameters are evaluated and are compared with the Central Pollution Control Board (CPCB) General Standards for the Discharge of Environmental Pollutants Part-A : Effluents, into Inland Surface Water according to The Environment (Protection) Rules, 1986 Schedule-VI because the Effluent from these STP's enters river Ghaggar. Also the performance of each STP was evaluated in terms of Removal/Reduction Efficiency. Since out of 30 MGD of STP, Mohali 10 MGD treated waste water is reused for Irrigation purpose in various gardens and lawns of Sector : 19, 20, 21, 29, 30, 33, 34, 36, 40, 42, 43, 44, 46, 47, 48, 51 and 52 of Chandigarh city therefore Average Effluent of this STP is compared with the CPCB Effluent Discharge Standards into Land for Irrigation. It was observed according to the results obtained that BOD value of the Effluent of STP Raipur Kalan and Raipur Khurd was not under permissible limit during the duration of study and Average Phosphate value of Raipur Khurd was exactly upto permissible limit according to Central Pollution Control Board (CPCB) General Standards for the Discharge of Environmental Pollutants Part -A: Effluents, into Inland Surface Water according to The Environment (Protection) Rules, 1986 Schedule-VI. According to the results obtained it was also revealed that all the Physico-Chemical and Biological Parameters evaluated for STP Mohali was under permissible limit according to CPCB Effluent Discharge Standards into Land for Irrigation and also into Inland Surface water. Also it was revealed from the performance study that efficiency of the three STP's mentioned above was poor with respect to removal of TDS (Total Dissolved Solids) in contrast to the removal /reduction efficiency in other parameters like TSS (Total Suspended Solids), BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand). The order of reduction efficiency was 1.TDS(39%) 2.COD(56%) 3.TSS(76%) 4.BOD(79%), 1.TDS(46%) 2.TSS(51%) 3.BOD(73%) 4.COD(78%) and 1.TDS(55%) 2.COD(75%) 3.TSS(78%) 4.BOD(88%) respectively in Raipur Kalan STP, Raipur Khurd STP and Diggian Mohali STP. In comparison with each other, out of the three STP's, Diggian STP Located at Mohali showed better results for the effluent, its reduction efficiency for BOD is 88% and is highest among Raipur Kalan STP and Raipur Khurd STP which is 79% and 73% respectively. From the evaluation it is further revealed that Mohali STP based upon MBBR technology have more stable results than Raipur Kalan STP, based upon UASB technology and Raipur Khurd STP, based upon ASP technology. The order of overall performance for the technologies studied in different STP's are: 1.MBBR 2.UASB 3.ASP which proves that MBBR technology is ahead to UASB and ASP technology in the treatment of sewage. Additionally, the working principle, problems associated with the operation and maintenance of all the three STP's is also discussed.