Wastewater Treatment Explained with Deepthi Nagappa

In the fifth episode of The WELL Labs Show, host Pavan Srinath is joined by Deepthi Nagappa (Senior Research Associate, Urban Water, WELL Labs) to unpack what really happens to wastewater after we flush the toilet.

The conversation explores how sewage treatment plants work, the difference between grey water and black water, what septic tanks actually do, and what nutrients like nitrogen and phosphorus do to our ecosystems.

Deepthi takes us inside the science and engineering of wastewater treatment – from microbes and sludge to aeration tanks, filtration systems, and the operational challenges that determine whether an STP succeeds or fails.

This episode is essential viewing for anyone working on urban water management, sanitation, environmental engineering, sustainability, or anyone curious about the invisible systems that keep cities clean and lakes alive.

Pavan Srinath is Managing Partner, Communications and Development at WELL Labs. Pavan is a communications and public policy professional who has spent over 14 years working in Bangalore’s not-for-profit sector.

Deepthi Nagappa is a Senior Research Associate in the Urban Water programme at WELL Labs, with expertise in water quality management, she has worked on lakes in and around Bengaluru, and on safe water reuse in decentralised STPs.

Resources:

1. Pavan Srinath LinkedIn, WELL Labs Website
2. Deepthi Nagappa: LinkedIn, WELL Labs Website
3. Binz, C., Nath, S., Aalbu, S., J., Miörner, J., Morgenroth, E., Rajora, C., Muraleedharan, G., Nagappa, D., Narayan, A., Singh, S. Palur, S., Prasad, H., Trikannad, S., Truffer, B., & Xue, L, Contzen, N., Kollmann. (2025). Strategies to Catalyse Safe, Efficient, and Reliable Decentralised Water Reuse in Bengaluru: Insights From Two Stakeholder Workshops Under the WaterReuseLab Project. Eawag and WELL Labs
4. Narayan, A. S.; Dorea, C.; Willetts, J.; Friedman, L.; Kalbar, P.; Chandran, K. (2024) A portfolio approach to achieving universal sanitation, Nature Water, 2(11), 1044-1047, doi:10.1038/s44221-024-00336-0
5. Kollmann, J.; Nath, S.; Singh, S.; Balasubramanian, S.; Reynaert, E.; Morgenroth, E.; Contzen, N. (2023) Acceptance of on-site wastewater treatment and reuse in Bengaluru, India: the role of perceived costs, risks, and benefits, Science of the Total Environment, 895, 165042 (11 pp.), doi:10.1016/j.scitotenv.2023.165042
6. Reynaert, E., Nagappa, D., & Morgenroth, E. (2023). Research brief: using sensors and automated chlorination to improve the microbial water quality of on-site sewage treatment plants in Bengaluru. doi:10.3929/ethz-b-000603755
7. Why Better Wastewater Management Could Help Solve Bengaluru’s Water Crisis 
8. Bengaluru has Highest Number of Decentralised STPS in the World
9. Wastewater Conference: Turning Bengaluru into the ‘Silicon Valley for Water Innovation’
10. How We Can Make Bengaluru’s Water Systems More Sustainable and Affordable
11. What We Learnt from the Water Reuse Project in 2023
12. Wastewater Reuse Policies across Indian States
13. Where Does Bengaluru Get Water from?
14. Bengaluru Has the Highest Number of Decentralised Sewage Treatment Plants Globally. Are They Effective?
15. Biological Wastewater Treatment: Principles, Modelling and Design
16. How safe is water reuse in practice? New insights from Bengaluru.
17. Research Brief: Using Sensors and Automated Chlorination to Improve the Microbial Water Quality of On-Site Sewage Treatment Plants in Bengaluru

The WELL Labs Show features rich conversations on water, environment, land and livelihoods, from the people and partners of WELL Labs. Hosted by Pavan Srinath, each episode explores complex environmental and social issues and helps you understand systems and dynamics better.

Subscribe to The WELL Labs show on the WELL Labs YouTube channel. 

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