Browsing by Author "Thalla, Arun Kumar"

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Hybrid Biological Systems for Wastewater Treatment
(National Institute of Technology Karnataka, Surathkal, 2018) D S, Manu; Thalla, Arun Kumar
The current trend in sustainable development deals majorly with the environmental management. There is a need for economically affordable, advanced treatment methods for the proper treatment and management of domestic wastewater containing excess nutrients (such as nitrogen and phosphorous) which otherwise may lead to eutrophication. In the present study, the effect of carbon to nitrogen (C/N) ratio, suspended biomass concentration (X), hydraulic retention time (HRT), and dissolved oxygen (DO) on nutrients removal in a lab-scale activated sludge biofilm (AS-biofilm) reactor was monitored. Based on various trials, it was seen that ASbiofilm reactor achieved good removal efficiencies with respect to COD-92%, NH4+- N- 93%, TN- 86% and TP-52%. Further, in order to improve the quality of the treated wastewater, photocatalysis by TiO2 was investigated as a post-treatment technology, using solar and UV irradiations. The UV photocatalysis was found to be better than solar photocatalysis during the comparative analysis. The maximum removal efficiencies of COD, MPN and phosphorous at optimum conditions in the case of UV and solar irradiations were 72%, 95%, 52% and 71%, 99%, 50% respectively. Similarly, to enhance the performance of the system in terms of nitrogen and phosphorous in addition to carbon removal integrated anaerobic/anoxic/oxic activated sludge biofilm (A2O-AS-biofilm) reactor was designed and operated by varying operating conditions such as C/N ratio, suspended biomass (X), HRT and DO. Based on various trials, it was seen that the A2O-AS-biofilm reactor achieved good removal efficiencies of COD-95.5%, TP-93.1%, NH4+-N-98% and TN-80% when the reactor maintained C/N ratio - 4, suspended biomass (X) - 3 to 3.5 g/L, HRT-10hr, and DO - 1.5 to 2.5mg/L. Applicability of soft computing techniques viz, Adaptive Neuro Fuzzy Inference System (ANFIS), Genetic Algorithm Adaptive Neuro Fuzzy Inference System (GA-ANFIS) and Particle Swarm Optimization Adaptive Neuro Fuzzy Inference System (PSO-ANFIS) to performance prediction of hybrid system was studied. ANFIS was applied on real time WWTP of 43.5 MLD capacity. ANFIS models showed better efficiency while modeling wastewater using multivariate analysis. So in the current study, in order to improve the prediction ability of ANFIS,ii hybrid models such as GA-ANFIS and PSO-ANFIS have been applied for the prediction of effluent TN, COD and TP concentration yielded from a hybrid ASbiofilm reactor. From the results, both GA-ANFIS and PSO-ANFIS proved capable to predict the effluent parameters of the reactor with varying operation conditions and can be adopted for modeling the nonlinear data.
Investigations on the Role of Green Synthesized Iron Nanoparticles in the Fenton’s Oxidation of Triclosan in Wastewater
(National Institute of Technology Karnataka, Surathkal, 2024) K N, Rashmishree; Shrihari, S.; Thalla, Arun Kumar
Resource Recovery and Value- Added Products From Agricultural Waste
(National Institute of Technology Karnataka, Surathkal, 2022) V, Adhirashree; Thalla, Arun Kumar
Lignocellulosic biomass resources such as agri-wastes are utilized as suitable feedstock to produce bioenergy and value-added products. In the present study, the Arecanut husk (AH) (Areca catechu) was selected as the feedstock to recover and produce value-added products. The study was carried out in three phases, (i) evaluation and ranking of various pretreatments methods using multiple attribute decision-making (MADM) approach, (ii) pretreatment and co-digestion of AH for biogas yield, and (iii) synthesis of AH derived lignin-carbon material for oil-water separation. In phase I, the objective is to evaluate and rank different pretreatment methods and select the best pretreatment method using MADM approaches to facilitate the increased biogas yield. The evaluation was done using Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and integrated Design of Experiments (DoE) - TOPSIS. Seven alternatives with five relevant attributes were adopted for this study. Based on the above decision-making framework, the alkaline pretreatment (NaOH (8%)) option was ranked first, followed by Ca(OH)2 and NH3.H2O (10%) pretreatment as second and third options. The integrated DoE - TOPSIS method has reduced the uncertainty in results by considering different weights and replications. The model portrayed the best pretreatment method employed in anaerobic digestion; thus, minimizing the experiments done during the downstream pretreatment process aided anaerobic digestion. Phase II of the study aims to evaluate the reduction of the recalcitrance of the AH by two approaches, (i) applying various pretreatment methods to access the cellulosic content and (ii) co-digesting it with food waste for the biogas production. The study evaluates the feasibility of utilizing chemically pretreated AH for biogas production. The effects of various pretreatment methods on the material solubilization to enhance biogas production from AH were checked. The AH was pretreated by four methods viz., acidic (H2SO4), alkaline (NaOH), oxidative (H2O2), and organosolv (ethanol in 1% H2SO4). The dosing of chemicals in acidic, alkaline, and oxidative pretreatments were 2, 4, 6, 8, and 10% (w/v), whereas, in organosolv, the dosage was varied from 25%, 50%, 75%, and 100% (v) for the batch hydrolysis. The batch hydrolysis trials were conducted at two different temperatures, i.e., 25⁰C and 90⁰C, and solids/liquid ratio of 1:10 ratio for 24 hours. The obtained experimental data from the ii solubilization study were analyzed using the TOPSIS technique, which showed that alkaline pretreatment at a temperature of 90⁰C had favoured the material solubilization among the four pretreatment methods. The pretreated AH was carried further for anaerobic digestion maintained at mesophilic condition. A maximum biogas yield of 683.89mL/gVS was obtained with 2.3 times more when compared with raw AH. Four kinetic models viz., First-order exponential, Logistic, Transference function, and Modified Gompertz model, were used to fit the experimental cumulative biogas production data. The Modified Gompertz model and logistic model (correlation coefficient > 0.99) were obtained as best fit to the cumulative biogas curve. The overall process performance is represented by the kinetic parameters obtained from these models. Furthermore, a multiple linear regression equation for the biodegradability index (BI) is formulated as a technical tool to predetermine biomethane production. It is depicted as a function of biomass compositions (cellulose, hemicellulose, and lignin) with a high correlation (> 0.95). The suitability of AH as the co-substrate with food waste (FW) for biogas production was examined in this research. The substrate mix ratio (AH: FW) was varied as 0:1, 1:3, 1:1, 3:1 and 1:0 in terms of volatile solids (VS) for a batch mode enclosed reactor (1L) at mesophilic (35⁰C) condition for 34 days. The 1:1 mix ratio, which yielded the highest biogas (321.12mL/gVS), is fixed for further experiment for optimizing the S/I ratio. The phase III lignin extracted from AH was used as an additive in lignin-carbon foam synthesis as a potential adsorbent for the oil-water separation. The lignin yield from the AH increased as the husk fibre size reduced. The extracted lignin and lignin-carbon foam were characterized by morphological, structural, compositional, and thermal degradation examinations. The synthesized carbon foam exhibited ultralight weight (density=0.0294 g/cm3), excellent hydrophobicity (water contact angle from 110°~ 132°), mesoporous structure (3D cell-like), good fire-retarding capacity and thermally stability due to lignin addition. The foam showed an excellent sorption capacity for different oils, and the highest sorption was observed for diesel oil (7842.71mg/g). The optimization of contact time, carbon foam dosage, and initial oil concentration were done for the diesel oil sorption. The isotherm study and kinetic model evaluation were done for the diesel adsorption on the lignin-carbon foam. Temkin model was found the best fit for the adsorption isotherm. The adsorption kinetics of the lignin-carbon foam iii for diesel oil was best described by pseudo-second-order kinetics. The thermodynamic parameters showed that the adsorption was endothermic and spontaneous (ΔH°=+4926.46 J/mol and ΔS°= 25.249 J/mol/K). The proposed mechanism depicts that the adsorption primarily influenced H-bonding and n-π interactions. The enduring adsorption of oil into the lignin-carbon foam within few seconds shows the material oleophilicity and confirms their application prospect in oil spill clean-ups.
Small Scale Decentralized Systems for Greywater Treatment and Recycling
(National Institute of Technology Karnataka, Surathkal, 2022) Chandra, Pragada Sarath; Thalla, Arun Kumar
As the world's freshwater supply becomes more limited, a greater focus on alternative water resources is required. Wastewater reuse promotes sustainability by lowering global environmental pollution and economic concerns. Greywater reuse and recycling can be essential practices to decrease the demand for clean water. Greywater refers to all domestic wastewater, excluding restroom effluents. Because of the lower levels of contaminants, greywater is easier to treat and recycle than sewage. Thus, greywater reuse is a promising alternative water source that can be used continuously for non- potable purposes. Greywater treatment methods vary depending on site and greywater characteristics. The water quality, quantity to be treated, and reuse applications determine a greywater treatment system design. The present study develops a pilot- scale multi-stage greywater treatment system to treat it to recyclable levels. The study is carried out in two phases. In the first phase, the performance evaluation of a primary treatment unit consisting of an anaerobic-aerobic biological system, followed by a sand filter, was done to remove COD, nutrients, and surfactants. In the second phase, post- treatment of biologically treated greywater by immobilized TiO2 based solar photocatalytic system is evaluated for removing triclosan effectively. In Phase I, the performance of the integrated anaerobic-aerobic-sand filter (pilot plant) is assessed based on the results obtained over 12 months of operation of the system. The removal efficiencies of the pilot plant for COD, BOD, anionic surfactants, TN, TSS, and TP are 89%, 95%, 99%, 85%, 88.5, and 87%, respectively Greywater, predominantly being wash water, where cleansers, mainly composed of surfactants, create huge shock loads and hamper the efficacy of the conventional treatment systems. Therefore, in the present study, experiments were conducted under surfactant shock loads (SSL) to study the reactors’ stability in handling the same. Results revealed that anionic surfactants were removed with efficiencies of 96.02%, 96.21%, 94.81%, and 98.42% for hydraulic retention times (HRT) of 32 h, 24 h, 16 h, and 8 h, respectively. The maximum effluent anionic surfactant concentrations obtained are 44.28, 59.12, 73.35, and 88.36 mg/L under the SSL of 85.94, 121.2, 155, and 180.5 mg /L, respectively. The reactor is recovered to steady-state conditions in about 8, 16, 20, and 28 h after removing the SSL of 85.94, 121.2, 155, and 180.5 mg/L, respectively. A linear relationship with R2= 0.95 indicates that recovery time is proportional to surfactant loading rate increase. Furthermore, the optimum surfactant-loading rate on the integrated system is 19.38 g/m3/h, with a removal efficiency is 91.8%. However, the effluent from the biological treatment unit needs further treatment to eliminate leftover pollutants. Phase II of the study involves developing a novel solar photoreactor. A ternary film of Fe2O3-TiO2/PVP is coated on the glass tube that stands in a parabolic trough concentrator (PTC) for an effective post-treatment of biologically treated greywater effluents. This ternary film of Fe2O3-TiO2/PVP coated on the glass tube is characterized by Field Emission Scanning Electron Microscope (FESEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-visible spectroscopy, and thermogravimetric analysis (TGA). Furthermore, the scratch hardness of photocatalysts at different Fe2O3/TiO2 compositions is investigated based on the width measurement of scratch using FESEM analysis. Results show that at an optimum coating of 5% of Fe2O3/TiO2 composition catalytic film, the maximum scratch hardness (7.984 GPa) is obtained. The photocatalyst has the highest cohesive bond strength and wearing resistance. The degradation of triclosan (TCS) in treated (anaerobic-aerobic treatment system) greywater has been investigated using a solar photocatalytic reactor. Box Behnken design (BBD) has been employed to screen the significant parameters (such as contact time, pH solution, and initial H2O2 concentration) and identify the most relevant interactions between the operating parameters. After carrying out the different trials of the various operational parameters, the response surface analysis has led to the optimal conditions for the yield of TCS degradation, resulting in an 83.27% removal. Based on LC-MS results, it is evident that the photocatalytic degradation of TCS has resulted in eleven intermediate products.
Solid-State Anaerobic Co-digestion of Organic Substrates for Biogas Production
(National Institute of Technology Karnataka, Surathkal, 2019) Uma, S.; Thalla, Arun Kumar; Devatha, C. P.
Solid waste management is an important problem in the developing countries due to the rapid quantity of waste generation as they urbanize. As the demand increases for bioenergy, biofuels produced from waste biomass replicates as a supplementary energy resource to satisfy the requirements. Most of these generated wastes consist of biodegradable organic matter, which could be utilized as a source for biofuel generation. These biodegradable wastes are highly opted by suitable treatment method, which is known by anaerobic biodegradation. This study investigated the performance of organic waste digestion in laboratory-scale for biogas production. Also, it focuses on the effects of process parameters such as pH, alkalinity and volatile acids on biogas yield performance by batch and semi-continuous digestion. Food waste and switchgrass is used as the feedstock in the present study, which is collected from NITK campus. The objective (1) of this study aimed to investigate the effects of pretreatment of switchgrass on biogas production. Switchgrass is used as a feedstock, which is subjected to physical and chemical pretreatment for batch digestion at mesophilic condition. Batch experimental results from raw switchgrass yields 248 mL CH4/g VS at mesophilic condition. The biomethane potential of pretreated SG is 53%, 52% and 12% higher for alkali, organosolv and thermal pretreatments respectively, and 44% and 20% lower at acid and liquid hot water pretreatments in comparison to raw SG yield. Highest biomethane yield confirms the enhanced biodegradability of switchgrass by alkaline and organosolv pretreatments. The objective (2) aimed at co-digesting the food waste (FW) and switchgrass (SG) by batch and semi-continuous mode for biogas production. The performance of batch codigestion is determined with FW and SG as a feedstock with different mix ratio (0:1; 1:1; 0:1 FW: SG) at mesophilic and thermophilic temperatures. Semi-continuous digestion is conducted by varying the loading from 4-8 g/L with mix ratios (100:0, 12:88, 25:75, 50:50 and 0:100 FW: SG) at mesophilic conditions. The process parameters (pH, alkalinity and volatile fatty acids) are monitored frequently for their interactive effects on biogas production by batch and semi-continuous digestion.iv The highest methane yield is observed with 1:1 FW: SG as 267 mL/g VS at mesophilic (32-day retention time) and 234 mL/g VS at thermophilic (18-day retention time) condition during batch digestion. Methane yield has a positive response on co-digestion and confirmed by digestion performance index (DPI). Results reveal that co-digestion at 1:1 ratio yields an enhanced performance with both FW and SG in mesophilic as well as thermophilic condition. This study confirms that the presence of slow and fast biodegradable organic matters has an equal contribution to methane yield. A t-VFA/Alk ratio maintains the consistency between acidification and methanation phase. The t-VFA/alk ratio is 0.2 to 0.9 for mesophilic and 0.3-1.5 for thermophilic condition. The release of volatile acids at shorter retention time is observed with thermophilic owing to, faster hydrolysis than at mesophilic conditions. The maximum biogas yield is 628 mL/g VS for 4 g /L loading for semi-continuous mode. The methane content obtained is around 65% that shows the stable performance at varying ratios of FW and SG. Average value of methane yield is 320 mL CH4/g VS which is estimated about 32,000 m3 that produces the energy of 320, 000 kW-h. Results well agreed to implement the combined heat and power system, as electrical and thermal efficiencies by 35% and 50% are widespread across many countries for the energy conversion.
Toxicity Study of Endocrine Disrupting Chemicals (EDCs) on Freshwater Fish Cyprinus Carpio
(National Institute of Technology Karnataka, Surathkal, 2018) Rao, Rekha; Manu, B.; Thalla, Arun Kumar
Water. It is one of the basic needs of all living creatures; be it man, plant or animal. The pharmaceutical waste dumping in the freshwater bodies in one of the main problems. These wastes contain many chemicals, antibiotics and other substances that degrade the water quality; and make it unworthy of human use and/or aquatic life. This work focuses on one of the main pollutants: Endocrine Disrupting Chemicals (EDCs). Some main examples are: Amoxicillin, Paracetamol and Diclofenac. These are Antibiotics and thus more commonly used. The chosen freshwater fish species for this study was Cyprinus carpio at fingerlings, juveniles and adult life-stages. This species is moderately tolerant to adverse conditions, hence an ideal choice. Also, it is very commonly found in the freshwaters of South Asian regions. The study comprised of two sets of experiments: Enzyme Assays and Predictive Toxicological Analysis. The Enzyme Assays comprise of (a) studying the Behavioral, Physical and Biochemical Responses induced by the pollutant exposure and (b) understanding the effects of presence and/or absence of water plants. The Predictive Toxicological Analysis gives an estimation of the impact of the same pollutants on some other freshwater species. From our experiments (Enzyme Assays), we have come to believe that, the newborn fishes are more susceptible to the pollutants than the adults. Also, one more interesting phenomenon was observed. The juvenile fishes showed more resistance to toxicity than both new-born and adult fishes. Literature says that, the enzymes and their activity at this growth stage is so active that it manages to get acclimatized with the toxic conditions. So, the situation imitates a vaccination procedure where the subject is given lower doses of pathogens (toxins, in this case) to help develop immunity to the higher loads of same pathogens (toxins, in this case). The Amoxicillin affected the liver most, whereas Paracetamol and Diclofenac paralyzed the muscle and brain tissues. The Predictive Toxicological Analysis provided that the genetically closer species (to C. carpio) were more endangered by these pollutants than the taxonomically related ones. The farther the relation from C. carpio, lesser the chances of almost same reactions and toxic effects.
Utilisation of Nutmeg Seed Shell-Based Materials for Micropollutant Remediation
(National Institute of Technology Karnataka, Surathkal, 2023) Thomas, Teema; Thalla, Arun Kumar
Waste management of both solid and liquid fractions is gaining priority due to urbanisation, industrialisation, and increased resource demand. Agricultural waste, one of the components of solid waste, has huge potential to convert into several by-products. Nutmeg seed shell (NSS) is an agricultural waste obtained from the cultivation of nutmeg (Myristica Fragrans) spice that can convert into useful products due to its high calorific value and lignin content. NSS can find applications as in refuse-derived fuel (RDF) in the form of briquettes and adsorbents for wastewater treatment. An in-depth research and development in NSS waste valorisation can find its whole potential in wastewater treatment. Removal of micropollutants in wastewater is a significant challenge due to their diverse chemical properties. Even after numerous treatment processes, treated water still contains micropollutants, which include hazardous synthetic dyes; this shows the importance of including advanced treatment techniques in wastewater treatment. Thermally modified NSS can be used as an adsorbent for wastewater treatment. The higher phenolic and lignin content in NSS can be utilised to prepare biomass-based catalysts for wastewater treatment. The current research examines the removal of anionic dye: Remazol Brilliant Blue Reactive (RBBR), cationic: Methyl Violet 10B (MV), and zwitterionic dye: Rhodamine B (RhB), using NSS-based materials to evaluate the removal efficiency of textile wastewater treatment that contains dyes with various ionic states. Thermally modified NSS (NSS Biochar) was identified with micropores and nanopores, resulting in 93.41% RBBR dye removal, but it was less efficient in the case of other dyes. Due to the presence of reducing and capping agents in NSS aqueous extract, it is used to synthesise silver nanoparticles (AgNPs). The optimised synthesis process resulted in the formation of AgNPs with a size 10–60 nm and a surface area of 88.16 m2/g. The best radical scavenging activity was seen at 200 g/mL for AgNPs. The application of these AgNPs in antibacterial uses is supported by their bacterial inhibition against both gram-positive and gram-negative bacteria (IZD≥ 15 mm) when ii compared to ampicillin (IZD ≤ 13 mm) at a concentration of 50 μg/mL. Synthesised AgNPs were used to study their feasibility in dye removal, and the results showed a better photocatalytic degradation (>90%) of RhB (10 mg/L), RBBR (100 mg/L), and MV (100 mg/L) when exposed to UV light. According to the degradation process, AgNP's affinity towards dye and their radical action impacts how effectively the dye degrades. The degradation mechanism was found by analysing the degradation products using HRLC-MS. In the presence of AgNP, the fluorescent dye RhB could not degrade at higher concentrations. The NSS's higher lignin and phenolic content are also utilised to prepare the catalyst for dye degradation. Lignin was extracted from NSS using alkali; the optimal extraction was achieved with 12% sodium hydroxide, resulting in 33% of lignin yield. To separate the catalyst after the treatment process, a composite built on NSS lignin and silver with magnetic property (Ag/Fe/Lignin) is used for dye degradation. Ag/Fe/Lignin resulted in improved degradation for all category dyes, even at higher concentrations. The research was also done on a mixture of cationic, anionic, and zwitterionic dyes. Ag/Fe/Lignin accomplished 94% degradation for a dye mixture at 100 mg/L concentration under UV light. It degraded more quickly and efficiently at greater concentrations when H2O2 was added as an activator in the presence of UV light. The processes that degrade dyes into simple organic molecules include deamination, demethylation, dihydroxylation, and cleavage of the aromatic ring by radical action. The degradation efficiency for the reusability study was >95% even after five cycles of experiments. The dye degradation capacity NSS-based composite (Ag/Fe/Lignin) demonstrated an improved method of utilising lignocellulosic waste components, such as NSS with high lignin content, in wastewater treatment.