-By Kranti Karande
The population of Pune city located in the state of Maharashtra, India is around 31 lakhs. Imagine how much waste water such a huge number of people produces! The amount of wastewater produced at Pune City is approximately 744 MLD (millions litres per day). Out of this, the WasteWater Treatment Plants (WWTP) treats about 527 MLD of water. The waste water treatment plants aim to minimize the adverse effect of untreated wastewater on ecology, the environment and human health through its adequate treatment before release into the ecosystem. But the question is, is this treated water indeed safe for environmental and public health? Whether or not the microorganisms present in the untreated water are eradicated following treatment? How WWTP contributing in spread of antimicrobial resistance (AMR) in nature?
Dr. Om Prakash Sharma’s group from NCMR, NCCS Pune started with an interesting question as to whether there is a difference between the number of bacteria in the sample of untreated and treated waste water. Different types of antibiotics are used in human therapy, veterinary and animal farming, and huge number of antibiotics are released into municipal wastewater which ultimately finds its way into the environment. Dr. Sharma’s group also tried to answer the question of whether or not the wastewater-isolated bacteria develop antimicrobial resistance.
They collected samples from untreated and treated waste water and stored it at appropriate storage conditions for further processing. The bacterial number was estimated by total viable count and most probable number methods and efficacy of current wastewater treatment plant in reduction of bacterial load and spread of antibiotic resistant bacteria in the environment was also studied.
A total of 30 bacterial species belonging to 18 different genera were isolated from the untreated water sample. Whereas in the treated wastewater only 9 species from 6 different genera were present, all 9 species of bacteria are non-pathogenic. They also performed antimicrobial susceptibility testing using these bacteria to know the role of WWTP in spread of AMR. Twenty one antibiotics have been used for testing. All of these antibiotics are common in testing antimicrobial resistance in bacteria. The bacteria isolated from untreated water samples indicated high levels of antibiotic resistance.
The research group concluded that, untreated wastewater sample contained wide range of organisms with high levels of antibiotic resistance while bacterial load reduced drastically and pathogens were absent in the treated wastewater. Results indicated that the wastewater treatment plant was working effectively and efficiently by reducing the bacterial load in treated wastewater. Several organisms of clinical significance like Acinetobacter septicus, Citrobacter farmeri, Klebsiella oxytoca, Raoultellao rnithinolytica etc. were also reported in untreated wastewater sample.
This study demonstrated the comparison between culturable bacterial population present in influent and effluent of municipal waste water treatment plant of Pune. The researchers conclude that waste water treatment not only reduces BOD (Biochemical Oxygen Demand), COD (Chemical Oxygen Demand) and TSS (Total Suspended solids) but also bacterial load of the waste water.