Bengaluru’s STP monitoring challenge

Bengaluru, a city rapidly growing in population and industrialisation, faces immense challenges in managing its wastewater. Approximately 80% of the water supplied for domestic use is returned as sewage, much of which is discharged untreated into natural drainage systems due to the lack of adequate sewerage networks. This leads to pollution in downstream areas, making effective sewage treatment essential for the city's sustainability.

The findings of a study conducted by ActionAid Association, focusing on the online monitoring of sewage treatment plants (STPs) in Bengaluru points towards the broader implications for wastewater management in urban India.

Sewage treatment and urbanisation in India

Urbanisation in India has significantly increased over the past few decades, with the urban population growing threefold since 1971. This increase in population has led to a rapid rise in sewage generation, far outpacing the development of treatment infrastructure. The gap between sewage generation and treatment capacity remains wide, as highlighted by a decadal assessment of wastewater treatment in India. As of 2014-15, sewage generation stood at 62,000 million litres per day (MLD), while treatment capacity was only 23,277 MLD.

Technological interventions for wastewater treatment

Most sewage treatment plants in India, including Bengaluru, rely on conventional technologies such as Sequential Batch Reactor (SBR) and Activated Sludge Process (ASP). These technologies are designed to treat wastewater to meet non-potable requirements. However, the performance of STPs can vary, and the effectiveness of these technologies depends largely on continuous monitoring and maintenance.

Study: Objectives and methodology

The primary objective of the study conducted by ActionAid was to analyse the performance of online monitoring systems in Bengaluru’s STPs and identify areas for improvement. The study focused on 31 STPs with a total treatment capacity of 1,042.5 MLD and collected data for a period of 45 days from the Bangalore Water Supply and Sewerage Board (BWSSB) monitoring dashboard. The dashboard captures data on six key parameters—Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), pH, Total Suspended Solids (TSS), Ammoniacal Nitrogen, and Total Nitrogen—once every five minutes, amounting to a substantial dataset of 2.4 million data points.

The study categorised data into two types: wrong/missing data and limits-breaching data. Wrong or missing data refers to instances where data is not configured, shows no variation, or remains stagnant across multiple days, indicating potential issues with the monitoring equipment. Limits-breaching data refers to instances where daily averages exceed the permissible limits set by regulatory authorities.

Key findings

• Discrepancy in limits set by BWSSB and KSPCB: The study found inconsistencies in the limits set for water quality parameters by the BWSSB and the Karnataka State Pollution Control Board (KSPCB). For example, the BWSSB has set the limit for Total Suspended Solids (TSS) at 20 mg/l, whereas the KSPCB prescribes a more stringent limit of 10 mg/l. Similarly, the pH limit is set at 6.5-9 by BWSSB, while KSPCB recommends a range of 6.5-8.5. These discrepancies highlight the need for standardised monitoring practices across regulatory bodies.

• Prevalence of wrong/missing data: A significant portion of the data collected was either wrong or missing. Thirteen STPs had wrong or missing data for more than 90% of the monitoring period, while eight STPs had wrong or missing data across all six parameters for more than 90% of the days. This indicates serious flaws in the online monitoring system, potentially due to faulty equipment or poor data management practices.

• Limits-breaching data: The study found that only two STPs exceeded permissible limits for more than 66% of the days monitored. Jakkur STP was identified as the most problematic, with COD and BOD values consistently exceeding the maximum permissible limits by four to six times. Additionally, some parameters, such as Ammoniacal Nitrogen and Total Nitrogen, were not even configured for certain STPs, further compromising the monitoring system's effectiveness.

• Performance rankings of STPs: The study ranked the STPs based on their overall performance, considering both wrong/missing data and limits-breaching data. Doddabele 40, Cubbon Park, and Yelemallappa Chetti were identified as the best-performing STPs, with minimal instances of wrong/missing data and no significant limits breaches. On the other hand, STPs like Kengeri, K&C Valley, and Hebbal were found to have not configured any parameters for monitoring, resulting in a maximum possible score of 45 for wrong/missing data.

Case study: Jakkur STP

The Jakkur STP emerged as one of the most concerning cases in the study. With the highest average limits-breaching days (17 days) and COD and BOD values significantly exceeding permissible limits, the STP poses a major environmental risk. Furthermore, key parameters such as Ammoniacal Nitrogen and Total Nitrogen were not even configured, raising questions about the adequacy of its monitoring system.

Recommendations for improvement

Based on the findings, the study offers several recommendations to improve the online monitoring of STPs in Bengaluru:

• Standardisation of monitoring parameters: All parameters prescribed by the National Green Tribunal and KSPCB should be included in the BWSSB monitoring dashboard. This includes the measurement of Faecal and Total Coliform, which is currently missing from the dashboard.

• Configuration of all parameters: Some STPs have not configured essential parameters like Ammoniacal Nitrogen and Total Nitrogen. Immediate steps should be taken to ensure that all relevant parameters are configured and monitored in real-time.

• Real-time alerts: The online monitoring system should be equipped to alert both BWSSB and KSPCB if any parameter breaches permissible limits or remains stagnant for an extended period. This would enable prompt action to address potential issues before they escalate.

• Addressing high-risk STPs: STPs with frequent limits breaches, such as Jakkur, should be prioritised for immediate intervention. Long-term breaches of COD and BOD levels could have severe environmental consequences, and steps must be taken to bring these STPs into compliance.

• Improved oversight by KSPCB: The KSPCB should regularly review the data from the online monitoring system to ensure that STPs are operating within permissible limits and that any discrepancies are addressed promptly.

Conclusion

The study on the online monitoring of Bengaluru's STPs reveals both the potential and the challenges of leveraging technology for wastewater management. While online monitoring systems provide valuable real-time data, their effectiveness is undermined by issues such as wrong/missing data, unconfigured parameters, and discrepancies in regulatory standards.

Addressing these issues will require concerted efforts from both BWSSB and KSPCB, as well as investments in upgrading the city's sewage treatment infrastructure. By improving the accuracy and reliability of online monitoring systems, Bengaluru can take a significant step towards more sustainable and efficient wastewater management.

The full report of the study can be accessed here