Browsing by Author "Mandal, Pubali"

Now showing 1 - 13 of 13

Analgesics in wastewater matrix: a comprehensive review on occurrence, toxicity, and sustainability assessment of biological, tertiary, and hybrid treatment processes
(Elsevier, 2025-06) Mandal, Pubali
Over the past few decades, increased consumption of pharmaceuticals has led to the prevalence of the pharmaceuticals and their metabolites in various wastewater matrices. Amongst, analgesics are one of the most consumed classes of medicines. These analgesics have complex molecular structures and physicochemical properties that do not favor degradation by conventional biological processes. Furthermore, they pose significant toxicity towards the non-target species and have the potential to disrupt the aquatic environment. Hence, researchers have focused on advanced or tertiary treatment processes, such as adsorption, photocatalysis, and the Fenton process, to remove these recalcitrant analgesics. Although these processes can remove analgesics with a high removal efficiency of around 85%, they fail to perform well with raw wastewater. Hence, hybrid processes have emerged as a wholesome treatment solution for pharmaceutical-contaminated wastewater. In this context, this review paper covers the performance assessment and sustainability of different biological, advanced, and hybrid processes in treating analgesic-contaminated wastewater. It was observed that the biological process alone could only remove around 60–70%, while the average analgesic removal from synthetic water using adsorption, Fenton, and photocatalysis was more than 80%. However, hybrid processes like a combination of constructed wetlands and photocatalysis exhibited more than 80% removal from real wastewater and were more financially and environmentally sustainable. This review provides a comprehensive idea of how analgesics, in particular, are ubiquitous in the aqueous environment and suggests how they can be removed sustainably by providing a comprehensive overview of all existing treatment systems.
Application of nanomaterials synthesized using agriculture waste for wastewater treatment
(Elsevier, 2024) Mandal, Pubali
Global water security is a pressing issue confronting the water sector. The high-water usage, discharge of untreated wastewater, and different anthropogenic pursuit pose severe threats to water quality. Wastewater treatment is inevitable to fight freshwater scarcity and to protect human health, aquatic fauna and flora, etc. High reactivity, surface-to-volume ratio, and versatility in material development (nanosorbents, nanocatalysts, and nanodisinfectants) made a promising platform for nanomaterials in wastewater remediation. Currently, wastewater treatment using green-based materials and processes is obtaining immense attention. The usage of green materials will reduce resource consumption, cost, and chances of secondary pollutant generation. The aim of this chapter is to understand the status of the development of nanosorbents, nanocatalysts, and nanodisinfectants using agricultural waste. The chapter highlights current trends in applying green nanomaterials modified using agriculture waste to treat wastewater. Agricultural wastes, which are used for nanosorbent, nanocatalyst, and nanodisinfectant synthesis, are documented. The applications of prepared nanomaterials in removing several recalcitrant organic contaminants such as dyes, phenolic compounds, antibiotics, and pathogenic bacteria are discussed. The discussion also includes heavy metals removal as well as disinfection using agro-waste-based nanomaterials. The mechanism of pollutant removal is described. The chapter aims to improve the understanding of agricultural waste that can be used in the green synthesis of nanomaterials. The applicability of all these nanomaterials for specific pollutant removal will help in selecting industries for large-scale implementations. The comparative assessment of pollutant removal efficacies is expected to help the researchers in selecting alternative agro-waste to prepare nanomaterials exhibiting better performance.
Chlorine mediated indirect electro-oxidation of ammonia using non-active PbO2 anode: Influencing parameters and mechanism identification
(Elsevier, 2020-09) Mandal, Pubali
Removal of ammonia-nitrogen from wastewater has gained considerable attention in recent years to reduce the critical problems arising in the water bodies receiving ammonia containing wastewater. Eutrophication and formation of odors due to wastewater discharging, the formation of undesirable by-products during the disinfection process can be significantly reduced using various treatment technologies. Although biological processes are mainly implemented to reduce ammonia-nitrogen concentration, several studies demonstrated electro-oxidation process as a potential alternative for ammonia-nitrogen removal. Among the non-active anodes, the majorly studied anode for chlorine mediated ammonia oxidation is boron-doped diamond anode. In this study, a non-active but comparatively low-cost graphite/PbO2 anode has been proposed for removing ammonia-nitrogen from wastewater. The study describes the effects of three influencing factors; current intensity, initial Cl− and NH3-N concentration on the oxidation efficiency of ammonia using graphite/PbO2 anode. The ammonia removal efficiency was found to be dependent on all the three parameters selected. The NH3-N removal efficiency of 96.5 ± 0.4% was achieved after 120 min of electro-oxidation of 100 mg L−1 NH3-N and 900 mg L−1Cl− containing solution at a current intensity of 0.3 A. Nitrate ion, and nitrogen gas were found as the stable end-products of the ammonia removal process. The formation of desirable end-product, N2, increased from 11.6% to 28.9% with increase in Cl− concentration from 300 to 1500 mg L−1. The steady-state concentrations of chloramine indicate formation of chloramine as an intermediate step of ammonia-nitrogen removal. The total chloramine concentration was <2.5% of the initial nitrogen content throughout the reaction.
A comprehensive review on the treatment of pesticide-contaminated wastewater with special emphasis on organophosphate pesticides using constructed wetlands
(Elsevier, 2024-09) Mandal, Pubali
Pesticides pose a significant threat to aquatic ecosystems due to their persistent nature and adverse effects on biota. The increased detection of pesticides in various water bodies has prompted research into their toxicological impacts and potential remediation strategies. However, addressing this issue requires the establishment of robust regulatory frameworks to determine safe thresholds for pesticide concentrations in water and the development of effective treatment methods. This assessment underscores the complex ecological risks associated with organophosphate pesticides (OPPs) and emphasizes the urgent need for strategic management and regulatory measures. This study presents a detailed examination of the global prevalence of OPPs and their potential adverse effects on aquatic and human life. A comprehensive risk assessment identifies azinphos-methyl, chlorpyrifos, and profenfos as posing considerable ecological hazard to fathead minnow, daphnia magna, and T. pyriformis. Additionally, this review explores the potential efficacy of constructed wetlands (CWs) as a sustainable approach for mitigating wastewater contamination by diverse pesticide compounds. Furthermore, the review assess the effectiveness of CWs for treating wastewater contaminated with pesticides by critically analyzing the removal mechanism and key factors. The study suggests that the optimal pH range for CWs is 6–8, with higher temperatures promoting microbial breakdown and lower temperatures enhancing pollutant removal through adsorption and sedimentation. The importance of wetland vegetation in promoting sorption, absorption, and degradation processes is emphasized. The study emphasizes the importance of hydraulic retention time (HRT) in designing, operating, and maintaining CWs for pesticide-contaminated water treatment. The removal efficiency of CWs ranges from 38% to 100%, depending on factors like pesticide type, substrate materials, reactor setup, and operating conditions.
Hybrid advanced oxidation processes for treatment of wastewater from the pharmaceutical industry
(CRC Press, 2024) Mandal, Pubali
Ever increasing health issues and rapid development of the healthcare sector causes discharge of pharmaceuticals in different water matrices. Conventional treatment processes are unable to remove the compounds from wastewater. The known and suspected toxicity and biological stability of these compounds led to the search for alternative technologies. Advanced oxidation processes (AOPs) involving a hydroxyl or sulphate radical has emerged to solve the issues of degrading recalcitrant compounds. Hybrid AOPs are mainly adopted to obtain faster kinetics and complete mineralization of the pharmaceutical compounds. The risk associated with the improper disposal and negligence in handling is addressed. The efficiency of the conventional treatment processes in removing pharmaceuticals are discussed and the need for hybrid AOPs are highlighted. Several hybrid AOPs used to remove analgesics, anti-inflammatory drugs, antibiotics, antiepileptic drugs, etc., and their efficiencies are documented. The chapter also circumscribes several challenges associated with the implementation of hybrid AOPs in removing pharmaceuticals. The chapter may provide an outlook on the current status of hybrid AOPs in the field of pharmaceutical compounds removal from several types of wastewaters.
Landfill leachate-induced ultraviolet quenching substances
(IWA, 2023-09) Mandal, Pubali
Landfill leachate is a complex wastewater with a wide range of pollutants and requires proper treatment before discharge. Landfill leachate is either treated on-site by biological and membrane processes or treated transported to nearby wastewater treatment plant for co-treatment with municipal wastewater. Recalcitrant organics, especially for stabilized leachate will not be removed or degraded by conventional biological processes. Some of these pollutants may absorb ultraviolet (UV) lights and decrease the UV transmittance. The UV quenching substances (UVQS) can be broadly classified as hydrophobic substances (humic acid + fulvic acid) and hydrophilic substances. The UVQS may interfere with the UV disinfection process and make it less effective. It may also protect any co-pollutant from being degraded by UV. Therefore, understanding of the treatment methods capable of removing UVQS is necessary. The aim of this chapter is to present overview of different treatment technologies available to remove/degrade UVQS. The composition of solid waste responsible for the formation of UVQS, characteristics, chemical composition, distribution and problems of UVQS has also been discussed.
A novel approach towards multivariate optimization of graphite/PbO2 anode synthesis conditions: Insight into its enhanced oxidation ability and physicochemical characteristics
(Elsevier, 2018-08) Mandal, Pubali
Electrochemical oxidation has drawn great interest for its potential application in degrading persistent organic pollutants (POPs) through electrogenerated hydroxyl radical at the surface of anode. This study aims at the preparation of an inexpensive graphite/PbO2 anode. For enhancing oxidation performance, preparation process parameters viz. Pb(NO3)2 concentration, potential, and time of electrodeposition of a graphite/PbO2 anode, electrodeposited from acidic electrolyte bath, were optimized targeting a POP, 2,4-dinitrophenol removal. The changes in morphological properties of the developed oxide films were analyzed using scanning electron microscopy (SEM) which manifested significant impacts of selected anode preparation process parameters. Furthermore, PbO2 film prepared at optimum conditions were characterized using SEM, atomic force microscopy (AFM), energy dispersive X-ray spectroscope (ESD) elemental mapping, and X-ray diffraction (XRD) for thorough investigation of crystal structures, elemental distribution over surface, and phase of PbO2. Angular structures in both SEM and AFM analysis and appearance of β-PbO2 characteristic peaks in XRD analysis confirmed formation of electrocatalytically active phase of PbO2. For further enhancing the oxidation ability, influencing experimental parameters viz. current intensity, pH, and NaCl concentration were optimized. After 2 h of electrolysis at optimum experimental conditions, COD and total organic carbon removal efficiency of 93.6 ± 0.63% and 71.7 ± 1.52% were obtained respectively.
Occurrence and detection of pharmaceuticals in wastewater and its subsequent treatment using constructed wetlands, bioelectrochemical systems and their combination
(IWA, 2024-04) Mandal, Pubali
Pharmaceutically active compounds (PhAC) are pervasive in aqueous environments, and their presence poses an ever-increasing threat to aquatic creatures and all associated living forms. Most PhACs are extremely hydrophilic and have a complicated molecular structure, preventing them from being destroyed by traditional wastewater treatment methods. In addition, these contaminants are present at such a low concentration that their detection poses a significant challenge. Researchers have utilized advanced oxidation processes to degrade these chemicals over time. However, most studies have been conducted on the lab scale and do not function well for real wastewater since many interfering substances are present. In addition, these techniques are expensive and result in the production of harmful byproducts. To combat the PhACs, it is vital to develop a sustainable economic strategy. This book chapter discusses the occurrence of PhACs in wastewater, their potential environmental impacts, and the necessary procedures for accurately quantifying these compounds. The book addresses the possibilities of biological systems, such as constructed wetlands (CW) and bioelectrochemical systems (BES), in the hunt for a sustainable method of eliminating PhACs. CWs have been selected because they are robust systems with several simultaneous removal mechanisms. BES have also demonstrated considerable potential for treating these substances in wastewater and producing bioelectricity. In addition, the chapter discusses an emerging technology, that is, hybrid CW–BES systems, which utilize the benefits of both CW and BES and may prove to be an efficient approach to treating wastewater, removing PhACs, and generating electricity simultaneously.
Review on landfill leachate treatment by electrochemical oxidation: Drawbacks, challenges and future scope
(Elsevier, 2017-11) Mandal, Pubali
Various studies on landfill leachate treatment by electrochemical oxidation have indicated that this process can effectively reduce two major pollutants present in landfill leachate; organic matter and ammonium nitrogen. In addition, the process is able to enhance the biodegradability index (BOD/COD) of landfill leachate, which make mature or stabilized landfill leachate suitable for biological treatment. The elevated concentration of ammonium nitrogen especially observed in bioreactor landfill leachate can also be reduced by electrochemical oxidation. The pollutant removal efficiency of the system depends upon the mechanism of oxidation (direct or indirect oxidation) which depends upon the property of anode material. Applied current density, pH, type and concentration of electrolyte, inter-electrode gap, mass transfer mode, total anode area to volume of effluent to be treated ratio, temperature, flow rate or flow velocity, reactor geometry, cathode material and lamp power during photoelectrochemical oxidation may also influence the system performance. In this review paper, past and present scenarios of landfill leachate treatment efficiencies and costs of various lab scale, pilot scale electrochemical oxidation studies as a standalone system or integrated with biological and physicochemical processes have been reviewed with the conclusion that electrochemical oxidation can be employed as a complementary treatment system with biological process for conventional landfill leachate treatment as well as a standalone system for ammonium nitrogen removal from bioreactor landfill leachate. Furthermore, present drawbacks of electrochemical oxidation process as a landfill leachate treatment system and relevance of incorporating life cycle assessment into the decision-making process besides process efficiency and cost, have been discussed.
A review on presence, survival, disinfection/removal methods of coronavirus in wastewater and progress of wastewater-based epidemiology
(Elsevier, 2020-10) Mandal, Pubali
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the global pandemic coronavirus 2019 disease (COVID-19). The outbreak of COVID-19 as Public Health Emergency of International Concern is declared by World Health Organization on January 30, 2020. The known route of transmission is due to direct contact or via respiratory droplets. Recently, several studies reported SARS-CoV-2 ribonucleic acid (RNA) in wastewater treatment plant samples. The presence of SARS-CoV-2 RNA in wastewater may predict COVID-19 occurrence qualitatively and quantitatively. The concept is known as wastewater-based epidemiology (WBE) or sewage epidemiology. The present study reviewed the presence of coronavirus in wastewater and investigations relating to WBE development as a tool to detect COVID-19 community transmission. Few articles reported a correlation of SARS-CoV-2 RNA concentration in wastewater with the number of COVID-19 cases, whereas few reported higher prediction by wastewater surveillance than confirmed cases. The application of WBE is still in a preliminary stage but has the potential to indicate an early sign of transmission. The knowledge of persistence of coronavirus in municipal and hospital wastewater is needed for the application of WBE and to understand the chances of transmission. The studies reported more prolonged survival of coronavirus in low-temperature wastewater. Studies relating to the inactivation of coronavirus by disinfectants and removal of coronavirus are also presented. Research on the performance of the commonly adopted disinfection technologies in inactivating SARS-CoV-2 in municipal and hospital wastewater is required to reduce the risk associated with municipal and hospital wastewater.
Role of inorganic anions on the performance of landfill leachate treatment by electrochemical oxidation using graphite/PbO2 electrode
(Elsevier, 2020-02) Mandal, Pubali
The influences of sulfate, chloride, nitrate, and bicarbonate ions on the electrochemical treatment performances of landfill leachate have been investigated. The concentrations of SO42−, Cl−, NO3− ions, and bicarbonate alkalinity of landfill leachate were 252 mg L-1, 1244 ± 22.3 mg L-1, 12 mg L-1, and 1750 ± 40.8 mg L-1 as CaCO3 without any external salt addition. The concentrations of anions were analyzed after 2 h of electrochemical oxidation to understand any conversion of externally added anions. Chemical oxygen demand (COD), dissolved organic carbon (DOC), and ammonia-nitrogen removal efficiencies after 2 h of electrolysis were 35.1 ± 2.3 %, 25.6 ± 2.9 %, and 97.6 ± 0.7 % respectively. Although no effect was observed for COD and DOC removal, increasing sulfate ion adversely affected NH3-N removal efficiency; the removal percentage decreased to 87.7 ± 0.5 % for 6082 mg L-1 of SO42− containing leachate. Addition of chloride improved the overall system performance. Obtained COD and DOC removal efficiencies were 67.2 ± 1.5 % and 55.8 ± 2.1 % for Cl− concentration of 4361 mg L-1 in leachate. Very low NH3-N removal (60 ± 2.1 %) for 1483 mg L-1 of nitrate containing leachate was obtained in this study due to the regeneration of ammonia by cathodic reduction of nitrate. Nitrate formation was observed as part of reactions for ammonia removal; for instance, the nitrate concentration increased from 12 mg L-1 to 39.3 ± 4 mg L-1 after electrolysis. For the leachate treatment containing 6000 mg L-1 of externally added HCO3−, the COD and DOC removal efficiencies decreased to 19.6 ± 0.6 % and 17.8 ± 1.1 %, but the more adverse effect was observed for NH3-N removal efficiency which was only 7.4 ± 1.8 %.
Simultaneous ammonia and organics degradation from municipal landfill leachate by electrochemical oxidation
(Taylor & Francis, 2024-03) Mandal, Pubali
The two primary issues for wide implementation of the electrochemical oxidation of wastewater are the significant cost of electrode and high energy consumption. On the other side, conventional biological processes and membrane technology have several drawbacks for recalcitrant landfill leachate (LL) treatment. To address these issues, graphite/PbO2 anode was used to treat medium to mature age (biodegradability index, 5-day biochemical oxygen demand/chemical oxygen demand: 0.25) LL. To reduce the cost of the oxidation process and maximize the efficiency, operating conditions were optimized. The optimum parameter values were obtained as 24.7 mA cm−2, 180 ± 3 rpm, and 1.9 cm of current density, stirring rate, and electrode gap, respectively. Dissolved organic carbon (DOC), chemical oxygen demand (COD), and ammonia-N removal efficiencies of 55 ± 1.4%, 81 ± 1.9%, and 56 ± 3% were obtained after 8 h of degradation at optimum conditions. The decrease in aromatic substances and ultraviolet (UV) quenching materials were evaluated by UV-Visible spectroscopy and Specific UV absorbance. The conversion of aromatic compounds into simpler molecule compounds was also verified by Fourier-transform infrared spectroscopy analysis. The lab-scale anode synthesis cost was evaluated as 0.42 USD.
Synthesis of graphite/PbO2 anode: electrodeposition process modeling for improved landfill leachate treatment using RSM and ANN approach
(Springer, 2019-07) Mandal, Pubali
Based on the hypothesis that the electrodeposition conditions may have effects on the developed electrode’s oxidation performance, the present study aimed at investigating the effects of a graphite/PbO2 anode preparation conditions (current intensity, Pb(NO3)2 concentration, HNO3 concentration, and temperature) on leachate treatment efficiency. Synthesis conditions were varied to improve the performance of the electrode, and leachate treatment efficiencies were evaluated using anodes prepared at different conditions. The Box–Behnken design was used as an experimental design for achieving the goal. The effect of variables on the system’s outcome was modeled by response surface methodology and artificial neural network. The variation in chemical oxygen demand (COD) removal efficiency from 7.81 to 24.58% for 2 h of electrolysis demonstrates significant influences of anode preparation conditions on its performance. The optimum conditions were attained as 0.64 A of current intensity, 0.16 mol L−1 of Pb(NO3)2, 0.16 mol L−1 of HNO3, and 76.98 °C of temperature. The PbO2 electrode developed at optimum conditions yielded 79 ± 1.7% COD removal efficiency of leachate at 8 h. The study results show that electrode synthesis conditions affect the oxidation ability of the electrode, and optimization of the same can significantly improve the treatment performance.