The increase in sewage generation in India demands a paramount shift in the treatment technology landscape. While many sewage treatment plants (STPs) are currently equipped with conventional technologies, their effective functioning requires upgradation and enhancement. To this end, water departments and technology manufacturers are developing new technologies such as integrated fixed film activated sludge (IFAS). IFAS has proven to be an effective biological technology, leveraging the properties of microorganisms in breaking down complex organic compounds, which significantly reduces the volume of sludge. Its application is rapidly picking up pace in India and globally, as it helps in the in-situ upgradation of STPs, which is cost- and energy-effective.
Working mechanism and benefits
IFAS is primarily used in sewage treatment projects for the upgradation of existing STPs. It does not demand major infrastructural changes in the STP and the upgradation takes place by adding biofilm media in the existing aerobic reactor. This media helps in biological nutrient removal from the wastewater while ensuring the reduction of biochemical oxygen demand by around 80 per cent and suspended solids by around 60 to 80 per cent. There are a few important steps in the implementation of this technology. These include dividing the existing aeration tank into multiple sections such as anaerobic, anoxic and IFAS tanks, along with mixers and aerators; installing density baffles in the primary sedimentation tank and secondary settling tanks to improve the efficiency of clarifiers; and installing disc filters that can help achieve the total suspended solids level of less than 10 mg per litre. Further, an ultraviolet system is installed in the STP for disinfection, and an odour control unit is installed to remove odour from the plant. Moreover, repair and replacement of existing electromechanical items such as screens, grit mechanisms and clarifiers are also included in the process.
The use of this technology has multiple benefits over conventional techniques such as the activated sludge process (ASP) and sequencing batch reactor. This technology can increase the treatment capacity and efficiency of the plant in the same or smaller tanks. This is possible as the biofilm provides an additional surface area for biomass growth and a high concentration of active microorganisms. It can effectively treat complex pollutants such as ammonia and phosphorus, enabling more stable nitrification. Furthermore, the operation of the established system is easier and more efficient as monitoring individual steps is possible. Further, it requires minimal maintenance over an extended period as the set-up remains unclogged.
Among other potential areas, this technology can also work effectively in a hybrid configuration. It can be integrated with a moving bed biofilm reactor (MBBR). With hybrid configurations, better dewatering properties can be achieved. Besides, IFAS systems can operate at lower mixed liquor suspended solids concentrations than ASP, which reduces the energy consumption in the aeration process. They also offer more resistance and robustness to shock loads and changes in wastewater composition since the biofilm acts as a buffer against these changes.
Key applications in India
The hybrid combination of IFAS with other technologies is prevalent in new sewage treatment projects. Its use is still relatively new in India and is gaining attention due to its varied benefits. Many urban local bodies and water utilities are now exploring its application to improve the performance of existing sewage infrastructure. For instance, the Bangalore Water Supply and Sewerage Board is tapping its potential to upgrade its existing STPs based on the standards of the National Green Tribunal. Further, it plans to use the technology at the STP in Yelahanka, Bengaluru.
In a similar stride, the Delhi Jal Board (DJB) has undertaken the upgradation and augmentation of existing STPs with IFAS. This is being done to address the gap in their existing total treatment capacity and increase it for future requirements. Some of these projects include the rehabilitation and upgradation of the existing 10 million litres per day (mld) Phase I STP and 25 mld Phase III STP in Yamuna Vihar to 15 mld and 55 mld respectively; and the 12 mld Phase I STP in Keshopur to 18 mld. The Phase I projects in Yamuna Vihar and Keshopur are expected to be completed in March 2024, while the Phase III project in Yamuna Vihar is likely to be completed in June 2024. DJB has also successfully upgraded the 45.5 mld Phase II STP in Yamuna Vihar. With these initiatives, the Delhi government expects to treat the sewage in the existing lakes of the city and revive them. It aims to treat more than 500 million gallons per day (mgd) of sewage, and more than 150 mgd of the treated water will be transferred to lakes like Sanjay Lake.
In a related development, the Municipal Corporation of Greater Mumbai is also deploying the technology in many of its STPs. To this end, a 10 mld STP for treating municipal wastewater has been upgraded with IFAS. Several other initiatives are also being undertaken to treat industrial wastewater by using this technology in STPs. For instance, an STP at Indian Oil Corporation Limited’s refinery in Vadodara, Gujarat, was designed with this technology, capable of treating 10 mld of industrial wastewater generated at the refinery. Another such application is the STP at Nestle India Limited’s factory in Nanjangud, Karnataka, which can treat 2 mld of industrial wastewater from the food processing factory.
Global case examples
IFAS has also picked up pace globally, with its usage expanding in both new and existing wastewater treatment facilities. For instance, a wastewater treatment plant (WWTP) using an IFAS-based system was inaugurated by the French authority Syndicat Mixte pour l’Aménagement Hydraulique in the Croult and Petit Rosne Valley regions of France in October 2023. This WWTP treats wastewater from 35 municipalities in the eastern district using a Hybas biological process that combines MBBR and IFAS. The process was developed by AnoxKaldnes, a subsidiary of Veolia Water Technologies, while the plant was designed and implemented by its subsidiary, OTV. OTV will operate and maintain this WWTP till 2027. This will require less process volume to reduce organic material and nitrogen in the sewage. As a result, the water quality of the Morée river, where the treated wastewater is discharged, would also be improved.
Future potential
Many key players are tapping the potential of this technology in decentralised and containerised water treatment plants (WTPs) to meet future water demands. For instance, VA Tech Wabag Limited is leveraging IFAS in modular configurations to meet site requirements in various Indian cities such as Noida. The suitability of using this technology in limited spaces has helped it deliver small-scale projects. Similarly, Bioxgreen is exploring the technology for brownfield wastewater treatment. It manufactures microbial consortia as a product called BioActiv IFASAM. It has undertaken the upgradation of low-performing WTPs by using this product. BioActiv IFASAM has the distinct feature of enhanced surface area pre-coated with active bio-culture, facilitating effective integration of the media with the existing infrastructure. In this regard, the positive acceptance of the technology will promote collaboration between private players and city authorities. Furthermore, it can explored for setting up new plants in the future.