Faculty Publications
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Item Photobioreactors for wastewater treatment: Recent advances(Nova Science Publishers, Inc., 2017) Lavanya, A.; Raval, K.; Raval, R.Sustainability of any waste treatment process depends on how a waste, particularly wastewater, is handled. Wastewater treatment is greatly important for the welfare of the environment and of the Earth in general. An integrative approach involving CO2 sequestration, effluent treatment and biomass generation presents a tremendous potential as the overall process in wastewater treatment and is more sustainable compared with conventional treatment. Research on the use of photobioreactors (PBRs) in wastewater treatment has gained momentum in the past decade. The use of photosynthetic microorganisms, such as microalgae and cyanobacteria, in wastewater treatment offers advantages, such as low energy requirement, biomass production and CO2sequestration. A large amount of inorganic species present in wastewater promotes the growth of various photosynthetic microorganisms. Removal of high concentrations of inorganic compounds is the major requisite in any wastewater treatment process. Some photosynthetic organisms, especially microalgae, play an important role in a treatment process that involves reduction of nitrates, phosphates and sulfates. Literature suggests that the use of PBRs in wastewater treatment considerably reduces the cost of microalgal cultivation and consequently controls water pollution, conserves freshwater resources and produces useful chemicals and biomass. This chapter focuses on research advances in wastewater treatment using PBRs. Different types of wastewater handled, mixed culture systems (e.g., algal.bacterial system employed in wastewater treatment), types of PBRs used, and bottlenecks that must be addressed to scale-up the wastewater treatment process are discussed. © 2017 by Nova Science Publishers, Inc. All rights reserved.Item Continuous operation of fluidized bed bioreactor for biogenic sulfide oxidation using immobilized cells of Thiobacillus sp(Asian Network for Scientific Information, 2007) Ravichandra, P.; Mugeraya, G.; Anupoju, G.R.; Ramakrishna, M.; Jetty, A.In the present study, obligate autotrophic Thiobacillus sp. was isolated from aerobic sludge distillery effluent treatment plant and the experiments were conducted in a fluidized bed bioreactor for the biological oxidation of sulfide using Ca-alginate immobilized Thiobacillus sp. All the experiments were conducted in continuous mode at different sulfide loading rates 0.018, 0.02475, 0.03375, 0.03825 and 0.054 and different hydraulic retention times 5, 3.67, 2.67, 2.35 and 1.67 h by varying flow rates 2.4×10-4, 3.3×10-4, 4.5×10-4, 5.1 × 10-4 and 7.2×10-4. Sulfide conversions higher than 90% were obtained at almost all sulfide loading rates and hydraulic retention times. All the experiments were conducted at constant pH of around 6 and temperature of 30±5°C. © 2007 Asian Network for Scientific Information.Item Reuse of incinerated textile mill sludge as adsorbent for dye removal(Springer Verlag service@springer.de, 2015) Jahagirdar, S.S.; Shrihari, S.; Manu, B.Textile industry is one of the largest and oldest industries in India. Textile mill uses large quantities of water for its variety of wet processes, which in turn generates a large amount of waste water. Effluent treatment plants treat textile mill waste water using a variety of chemical coagulants thus producing greater amount sludge. Disposal of sludge is a challenging problem. In this study Textile mill sludge was incinerated at 800°C and used as an adsorbent without any activation. SEM images confirmed that, sludge ash was porous in nature and could be used as an adsorbent. For the entire study, Remazol blue dye was used. Experimental studies were carried out in an acidic pH range, showed good dye removal by using incinerated textile mill sludge ash. Experimental results obtained fitted well in Langmuir and Freundlich isotherms. © 2015, Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.Item Optimum Operating Conditions for Subcritical/Supercritical Fluid-Based Natural Circulation Loops(American Society of Mechanical Engineers (ASME) infocentral@asme.org, 2016) Yadav, A.K.; Bhattacharyya, S.; Ram Gopal, M.R.Natural circulation loop (NCL) is simple and reliable due to the absence of moving components and is preferred in applications where safety is of foremost concern, such as nuclear power plants and high-pressure thermal power plants. In the present study, optimum operating conditions based on the maximum heat transfer rate in NCLs have been obtained for subcritical as well as supercritical fluids. In recent years, there is a growing interest in the use of carbon dioxide (CO2) as loop fluid in NCLs for a variety of heat transfer applications due to its excellent thermophysical environmentally benign properties. In the present study, three-dimensional (3D) computational fluid dynamics (CFD) analysis of a CO2-based NCL with isothermal source and sink has been carried out. Results show that the heat transfer rate is much higher in the case of supercritical phase (if operated near pseudocritical region) than the subcritical phase. In the subcritical option, higher heat transfer rate is obtained in the case of liquid operated near saturation condition. Correlations for optimum operating condition are obtained for a supercritical CO2-based NCL in terms of reduced temperature and reduced pressure so that they can be employed for a wide variety of fluids operating in supercritical region. Correlations are also validated with different loop fluids. These results are expected to help design superior optimal NCLs for critical applications. © 2016 by ASME.Item Artificial intelligence models for predicting the performance of biological wastewater treatment plant in the removal of Kjeldahl Nitrogen from wastewater(Springer Verlag, 2017) Manu, D.S.; Thalla, A.K.The current work demonstrates the support vector machine (SVM) and adaptive neuro-fuzzy inference system (ANFIS) modeling to assess the removal efficiency of Kjeldahl Nitrogen of a full-scale aerobic biological wastewater treatment plant. The influent variables such as pH, chemical oxygen demand, total solids (TS), free ammonia, ammonia nitrogen and Kjeldahl Nitrogen are used as input variables during modeling. Model development focused on postulating an adaptive, functional, real-time and alternative approach for modeling the removal efficiency of Kjeldahl Nitrogen. The input variables used for modeling were daily time series data recorded at wastewater treatment plant (WWTP) located in Mangalore during the period June 2014–September 2014. The performance of ANFIS model developed using Gbell and trapezoidal membership functions (MFs) and SVM are assessed using different statistical indices like root mean square error, correlation coefficients (CC) and Nash Sutcliff error (NSE). The errors related to the prediction of effluent Kjeldahl Nitrogen concentration by the SVM modeling appeared to be reasonable when compared to that of ANFIS models with Gbell and trapezoidal MF. From the performance evaluation of the developed SVM model, it is observed that the approach is capable to define the inter-relationship between various wastewater quality variables and thus SVM can be potentially applied for evaluating the efficiency of aerobic biological processes in WWTP. © 2017, The Author(s).Item Performance evaluation of horizontal and vertical flow constructed wetlands as tertiary treatment option for secondary effluents(Springer Verlag, 2019) Thalla, A.K.; Devatha, C.P.; Anagh, K.; Sony, E.Constructed wetlands (CWs) are simple low-cost wastewater treatment units that use natural process to improve the effluent water quality and make it possible for its reuse. In the present study, a comparison is made between horizontal subsurface flow (HSSF-CW) and vertical flow (VFCW) constructed wetland in effectively post-treating the effluents from the secondary biological treatment system. Locally available plants, viz. Pennisetum pedicellatum and Cyperus rotundus, which are abundantly available in the Western Ghats, were used in the wetland. A pilot-scale study was undertaken in National Institute of Technology, Karnataka Campus. The experiments were conducted at two hydraulic retention times, i.e., 12 h and 24 h. The experimental study was carried out in February 2018 to May 2018. Concentration-based average removal efficiencies for HSSF-CW and VFCW were BOD, 77% and 83%; COD, 60% and 65%; NH4 +–N, 67% and 84.47%; NO3–N, 69% and 66.75%; and PO4–P, 85% and 90%, respectively. VFCW showed a better overall removal efficiency than HSSF-CW by 7.14%. Thus, constructed wetland can be considered as a sustainable alternative to the tertiary conventional treatment of domestic wastewater, thus making it possible for reuse. © 2019, The Author(s).Item Removal of ametryn and organic matter from wastewater using sequential anaerobic-aerobic batch reactor: A performance evaluation study(Academic Press, 2019) Mahesh, G.B.; Manu, B.The present study was aimed to investigate biodegradation of 2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine (ametryn) in a laboratory-scale anaerobic sequential batch reactor (ASBR) and followed by aerobic post-treatment. Co-treatment of ametryn with starch is carried out at ambient environmental conditions. The treatment process lasted up to 150 days of operation at a constant hydraulic retention time (HRT) of 24 h and an organic loading rate (OLR) of 0.21–0.215 kg-COD/m3/d. Ametryn concentration of 4 and 6 mg/L was removed completely within 48–50 days of operation with chemical oxygen demand (COD) removal efficiencies >85% at optimum reactor conditions. Ametryn acted as a nutrient/carbon source rather causing toxicity and contributed to methane gas production and sludge granulation in the anaerobic reactor. Biotransformation products of ametryn to cyanuric acid, biuret, and their further conversion to ammonia nitrogen and CO2 are monitored during the study. Adsorption of ametryn on to reactor sludge was negligible, sludge granulation, presence of ANAMMOX bacteria, and low MLVSS/MLSS ratio between 0.68 and 0.72. The study revealed that ametryn removal occurred mainly due to biodegradation and co-metabolism processes. Aerobic post-treatment of anaerobic effluent was able to remove COD up to 95%. The results of this study exhibit that anaerobic-aerobic treatment is feasible due to easy operation, economic, and highly efficient. © 2019 Elsevier LtdItem Electrochemical synthesis of ZnO-WO3 nanocomposites and their photocatalytic activity(Springer editorial@springerplus.com, 2020) Goveas, J.J.; Shetty, S.; Mascarenhas, N.P.; D’Souza, R.M.; Gonsalves, R.A.Abstract: Heterometal oxide nanoparticles of ZnO-WO3 (ZWO) were synthesized using a facile dual step hybrid electrochemical–thermal technique. The role of surfactant additives during synthesis was investigated by introducing three different surfactants:Cetyltrimethyl ammonium bromide (Cetrimide), sodium dodecyl sulphate (SDS), and polyethylene glycol (PEG) into the electrolytic bath. X-ray diffraction and surface morphology studies indicate that the nanoparticles are cubic with an average crystallite size of 30–40 nm. Photocatalytic behaviour of these nanomaterials was tested using Methylene Blue (MB) and Eriochrome Black-T (EBT) as sample pollutants. The best results were observed for the photocatalyst generated in the presence of SDS as an additive and calcined at 650 ?C. High degree of decolourisation of both dyes resulting in complete mineralisation is due to the photocatalytic activity of ZWO which is greater than that of commercially obtained TiO2-P25 photocatalysts. This proves that the electrochemical synthetic route with its low cost and high efficiency is an excellent technique for the bulk synthesis of heterometal oxide photocatalysts which could effectively be used in effluent water treatment. Graphic Abstract: [Figure not available: see fulltext.]. © 2020, Springer Nature B.V.Item Instability mitigation by integrating twin Tesla type valves in supercritical carbon dioxide based natural circulation loop(Elsevier Ltd, 2021) Wahidi, T.; Yadav, A.K.Flow instability in supercritical fluid based natural circulation loop (NCL) is still an investigation aspect of physical and mathematical problems to comprehend. Therefore, NCLs require precise design assessment that focuses on the interaction of all the transient responses of buoyancy and friction forces which can ensure a stable zone of operation. To promote the uni-directional circulatory movement of loop fluid and to decrease the magnitude of instability, this research emphasizes the development of NCL integrated with two modified Tesla type valves. In this article, numerical simulations have been carried out for a range of supercritical pressures (80–100 bar) and heat inputs (500–2000 W) to do the comparative investigation of instability phenomenon in supercritical carbon dioxide based regular natural circulation loop and a new modified twin Tesla NCL. Results show that the use of modified Tesla valves leads to better stabilization for all supercritical pressures and heat inputs considered in the study. It is also found that the proposed Tesla NCL mitigates the temperature and velocity oscillations with a marginal drop of ?3% in the heat transfer performance. Using asymmetrical flow resistance to stimulate directional circulation is an efficient technique to combat this instability issue. Obtained results are validated with the existing correlations, and a good agreement is obtained. © 2020 Elsevier LtdItem Optimizing Solid Waste Management: A Holistic Approach by Informed Carbon Emission Reduction(Institute of Electrical and Electronics Engineers Inc., 2024) Hegde, S.; Sumith, N.; Pinto, T.; Shukla, S.; Patidar, V.Reducing carbon monoxide (CO) emissions is imperative for safeguarding human health and environment. CO adversely affects respiratory health, contributing to respiratory problems and, in severe cases, fatalities. Its reduction aligns with the broader efforts to combat climate change, as CO is often emitted alongside other greenhouse gases. Environmental consequences include air pollution and its detrimental impact on ecosystems. Compliance with emission standards is essential, and reducing Carbon emissions can lead to social and economic benefits, such as increased productivity and reduced healthcare costs. Moreover, the focus on emission reduction drives technological innovation, fostering the development of cleaner and sustainable technologies. In essence, addressing CO emissions is vital for creating a healthier, more sustainable future. However, in most of the cases, there has been no much importance given in scientific management of solid wastes. This has therefore resulted in large magnitude of carbon emission causing serious implications. This paper presents a novel approach to solid waste management, combining carbon emission assessment with advanced object detection technology. We develop an integrated waste management model that employs machine learning techniques for the identification and categorization of metals, non-metals, and plastics within the solid waste stream. To optimize waste sorting and recycling processes, we implement an efficient object detection system that leverages computer vision algorithms. This system enhances the precision of material identification within solid waste, thereby improving sorting accuracy. Additionally, we establish a database to quantify carbon emissions associated with distinct waste management methods, encompassing incineration, composting, recycling, bioremediation, and landfills is used for this work. The novelty of the work lies in the integration of CO2 emissions data and object detection resulting into a decision-making model, providing a holistic evaluation of the environmental impact of varied waste management scenarios. The formulation of recommendations for sustainable waste management practices based on the integrated assessment of carbon footprints and material identification is easy to implement in real world.The technical framework proposed here, aims to inform decision-makers on adopting environmentally conscious strategies for waste management. © 2024 The Authors. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.