Dr. Mallikarjuna Challa

 

Brief Details:

I am currently working as a Postdoctoral Fellow at the Zuckerberg Institute for Water Research, Ben-Gurion University of the Negev, Israel. I earned my PhD in Civil Engineering with a specialization in Environmental Engineering from the Indian Institute of Technology Bhubaneswar (2024, coursework CGPA of 9). My doctoral research focused on removing organics and nutrients from rice mill effluents using an aerobic inverse fluidized bed biofilm reactor. I also hold an M. Tech in Civil Engineering with a specialization in Environmental Engineering from NIT Tiruchirappalli (2016, CGPA: 8.39) and a B. Tech in Civil Engineering from Jawaharlal Nehru Technological University (JNTU CEA), Anantapur (2013, percentage: 77.43). My master’s project involved phosphorus recovery as hydroxyapatite using batch reactor experiments, while my B. Tech project work focused on investigations related to mini percolation tank construction.

I have diverse work experience, including positions as an Assistant System Engineer (software testing for COBOL-mainframe system products, July 2013 to August 2014) at Tata Consultancy Services and academic roles at NIT Warangal (Adhoc Lecturer, August 2016 to May 2017), NIT Tiruchirappalli (Temporary Faculty, July 2017 to May 2018), and NIT Andhra Pradesh (Ad-hoc Faculty, August 2023 to May 2024). During my teaching tenure as a faculty, I taught subjects like Introduction to Environmental Engineering (B-Tech graduates) and Industrial Wastewater Treatment (B-Tech graduates). I have also handled the Fluid Mechanics lab (B-Tech graduates) and Environmental lab courses (Both B-Tech and M-Tech graduates).

My research primarily focuses on wastewater treatment, particularly biofilm processes, optimization techniques, and sustainable recovery of nutrients like phosphorus. The results of my research work have been published in reputed civil and environmental engineering journals such as the Journal of Environmental Chemical Engineering, Process Safety and Environmental Protection, International Biodeterioration & Biodegradation, Process Biochemistry, and Journal of Hazardous, Toxic, & Radioactive Waste. I have also contributed to academic literature through book chapters in reputable publishers such as Elsevier and Wiley. My expertise in wastewater treatment processes is showcased through oral and poster presentations at national and international conferences.

Research: Biofilm-based bioreactors for water and wastewater treatment

The remediation of water and wastewater is crucial for safeguarding the environment and promoting human health. Recently, innovative biofilm-based technologies, such as aerobic inverse fluidized bed biofilm reactors (AIFBBR) and hybrid Donnan-Membrane Biofilm Reactor (MBfR), have demonstrated their effectiveness in addressing the evolving challenges of water and wastewater treatment.

In this presentation, I will discuss two biofilm-based bioreactors' applications in water and wastewater treatment. The first application uses an Aerobic Inverse Fluidized-Bed Biofilm Reactor (AIFBBR) for treating rice mill effluent, which typically contains high concentrations of organic material and nutrients. In the AIFBBR, biofilm develops on buoyant carrier particles, facilitating efficient interaction between the biofilm and contaminants. Our study centered on enhancing the performance of the AIFBBR, leading to effective pollutant removal and a significant reduction in organic matter (as measured by COD: 92%) and nutrient levels (NH₄⁺-N: 97% and PO₄^3--P: 32%). Subsequently, the treated effluent can be safely discharged into the surrounding environment with minimal additional polishing required for phosphate removal.

In the second part of the talk, I will talk about the hybrid MBfR and its application for removing nitrate (NO₃^-) and perchlorate (ClO₄^-) from surface and groundwater. MBfR integrates a Donnan dialysis membrane with a biofilm reactor, allowing selective ion exchange and biological treatment to occur simultaneously. In this study, The Donnan membrane process was applied to effectively remove NO₃^- and ClO₄^- from synthetic water. This Donnan membrane reduced NO₃^- concentrations from an initial level of 160 mg/L to nearly 2 mg/L within two hours of reactor operation. In the case of the ClO₄^- the membrane yielded 3 mg/L from an initial concentration of 50 mg/L over six hours of operation. Additionally, when operated in batch mode, the MBfR achieved an impressive NO₃^- removal rate of 95% (Initial NO₃^-: 60 mg/L and Final NO₃^-: 3 mg/L) over six days.

The results from both the AIFBBR and hybrid MBfR applications clearly indicate that biofilm processes can be effective and sustainable solutions for treating wastewater and polluted surface water sources.

Teaching: Submerged aerated filter for robust and reliable high-rate tertiary nitrification

Numerous municipal wastewater treatment plants worldwide will have to be extended or upgraded to satisfy discharge standards of nutrients (particularly nitrogen). Nitrogen and phosphorus removal is essential to avoid algal blooms & eutrophication issues in lakes or enclosed coastal waters and to preserve water resources. However, this task is very challenging because it requires a lot of space, money, and time. Simple chemical precipitation can remove phosphorus, whereas nitrogen removal needs novel processes. Biofiltration has been suggested as a promising sustainable technique for tertiary nitrification due to its energy and resource-intensive nature. Without causing secondary pollution, biological filters (biofilters) effectively convert NH₄⁺-N to nitrate.

Biofilters contain biofilm support media submerged in wastewater to produce a sizable contact area for biological treatment. Biological aerated filters (BAF) commonly demonstrated nearly 100% nitrogen removal efficiency. Nevertheless, head losses and clogging are the significant limitations of BAFs. This can be overcome in another biofilter, i.e., a submerged aerated filter (SAF). SAF typically uses random/structured plastic media (typically small-sized: 0.7–8.0 mm, granular media in fully submerged conditions). The SAF term came from the combination of air and the filtering action of the bacteria. A SAF typically consists of a medium that treats carbonaceous and nitrogenous matter using biomass fixed to the media and capturing the suspended solids in the media.

SAF is a relatively low-cost technique that efficiently transforms NH₄⁺-N without secondary pollution. Installing SAF for tertiary treatment is a practical alternative to extending nitrification and denitrification processes. Adding it to an existing plant where little space is available is easy. The capital cost of adding tertiary treatment is much lower than constructing a new advanced treatment system. Furthermore, construction does not require any stoppage or interference with the operation of existing reactors. SAF’s nitrification performance greatly depends on the filter's water and air velocities. Additionally, ammonia loading rates (specifically shock loadings) have considerably affected the system’s nitrification performance.

Google Scholar Link:

https://scholar.google.com/citations?user=u9BnzCQAAAAJ&hl=en