Per- and polyfluoroalkyl substances (PFAS) are a group of persistent organic compounds that present significant risks to both environmental systems and human health. The increasing concentration of PFAS in landfill leachate has been an emerging concern for waste management. This article presents a critical review of the current state-art of the technologies and processes for PFAS removal from landfill leachate. The article primarily addresses two aspects: (a) identifying the primary sources contributing to PFAS leaching, which includes examining various waste streams such as municipal solid waste (food packaging products, household consumer goods, cosmetics, electronic components), construction and demolition debris, and industrial waste (bio-solids, incineration ash, and manufacturing waste); (b) evaluating different technological options for PFAS removal from leachate, such as adsorption techniques, membrane filtration, electrochemical oxidation, photocatalytic oxidation, and biological treatment. The findings showed that the PFAS concentrations across different MSW components varied significantly, ranging from as low as 0.1 ng/L to as high as 150,000 ng/L, depending on the PFAS type and source. Additionally, the article explores the factors influencing the performance of these treatment technologies based on the experimental results, development stage, reaction time, and removal efficiency. Adsorption (granular and magnetic activated carbon) and membrane filtration processes have demonstrated higher PFAS removal efficiency ranging from 70% to 95%. This study emphasized the need for effective PFAS treatment strategies while addressing ongoing challenges and future research directions in mitigating their environmental impact.

Rapid urbanization and population growth have led to a significant rise in municipal solid waste litter (MSWL) generation. The traditional manual collection process are labour-intensive, timeconsuming, and often inadequate for addressing the growing volume of MSWL in cities. Advanced vacuum suction devices (VSDs) have emerged as an effective solution for indoor litter collection. However, limited studies has been reported to understand the feasibility of these devices for outdoor applications. Therefore, this study proposes a mobile street cleaner (mSC), a VSD specifically designed and engineered for MSWL collection from diverse urban settings. The study highlights the design methodology and model assumptions for developing a mechanical suction unit (MSU) for the mSC, demonstrating a 70% performance efficacy at 5000 m3/h (S1) suction flow rate. Batch-scale experimental simulations with varying hose pipe diameter (D) (0.3-0.15 m), suction flow rate (S) (2500-5000 m3/h) and litter characteristic was conducted to optimize mSC. At S1, the nozzle inlet velocity of 23-40 m/s was found to be more effective in collecting larger and heavier litter particles compared to S2. Therefore, the hose pipe diameter of 0.25 (D2) and 0.20 m (D3) at S1 was found to be most efficient and less time consuming in MSWL collection. Finally, the study highlights the potential benefits of proposed mSC in automating collection process, reducing operational costs, improving source segregation and recycling opportunities. The findings of this study offer valuable insights for technocrats and researchers in enhancing application of VSDs for sustainable urban waste management.

The rapid transition towards modernization and industrialization led to an increase in urban population, resulting in paramount challenge to municipal sewage sludge management. Anaerobic digestion (AD) serves as a promising venue for energy recovery from waste-activated sludge (WAS). Addressing the challenge of breaking down floc structures and microbial cells is crucial for releasing extracellular polymeric substances and cytoplasmic macromolecules to facilitate hydrolysis and fermentation process. The present study aims to introduce a combined process of alkaline/acid pre-treatments and AD to enhance sludge digestion and biogas production. The study investigates the influence of alkali pretreatment at ambient temperature using four alkali reagents (NaOH, Ca(OH)2, Mg(OH)2, and KOH). The primary goal is to provide insights into the intricate interplay of alkali dosages (0.04-0.12 g/gTS) on key physic-chemical parameters crucial for optimizing the pre-treatment dosage. Under the optimized alkaline/acid pre-treatment condition, the TSS reduction of 18%-30% was achieved. An increase in sCOD concentration (24%-50%) signifies the enhanced hydrolysis and solubilization rate of organic substrate in WAS. Finally, the biomethane potential test (BMPT) was performed for pre-treated WAS samples. The maximum methane (CH4) yield was observed in combination A1 (244 mL/g) and D1 (253 mL/g), demonstrating the pivotal role of alkali optimization in enhancing AD efficiency. This study serves as a valuable resource to policymakers, researchers, and technocrats in addressing challenges associated to sludge management.

Methane (CH4) and carbon dioxide (CO2) are the primary greenhouse gases released due to the open dumping of Municipal Solid Waste (MSW). Studies have proved that continuous emission of these greenhouse gases may result in a significant climate change over a long term. The overall percentage ratio of these gases ranges from 40 to 60% of CH4 and the remaining being CO2. CH4 causes environmental issues such as air pollution and landfill fire. In developed countries, 14.1% of all CH4 emissions are from landfill sites. Therefore, it is essential to reduce emissions of these gases from open dumpsites to prevent the risk of global warming and human health. The capping of these dumpsites with an appropriate bio-cover (also called as final cover) is one of alternative method towards a sustainable management of environment. The present review represents lab-scale and field-scale studies carried across the globe to develop an efficient bio-cover layer. The scope of the study includes the impact of physical parameters such as type of material, particle size, permeability, soil texture, moisture content, density, nutrients, temperature, and pH on bio-cover. Finally, the adaptability of different waste materials such as sewage sludge, bio-compost, crushed wood, gravel sand, rice husk, soil, bio char and wood pellets etc. for choosing appropriate design of bio-cover has been presented.

The proliferation of decentralized biogas plants (DBPs) in emerging economies offers a compelling avenue for sustainable energy production and waste management. The community-based application of DBPs servers as the potential solution to curb the increasing energy demand in the modern-day era. This manuscript aims to discuss some major issues, facts, and suggestions related to the sustainable management of DBPs in urban and rural areas. The review methodology adopted is based on an extensive literature review, consolidating insights from various scholarly articles, websites, and reported documents. The review examined the significance of different feedstock characteristics, such as moisture content, carbon/biomass ratio, carbon/nitrogen ratio, total solids, total volatile solid and particle size to enhance biogas production yield. It was found that the co-digestion process for two or more categories of feedstock had higher efficacy compared to the single-use feedstock. The study also dissected potential sites for DBPs, which can serve benefits related to resources and logistics to multiple stockholders (suppliers, producers, and buyers). However, the primary aim of the present study was to highlight practical challenges related to planning, designing, monitoring-control systems, cost-benefit analysis, resource management, and optimization aspects for DBPs. It was also found that the transformation process (separation, drying, pelletizing, composting, blending, and packaging) of waste residues to bio-fertilizers is an energy intensive process. Therefore, the aim of the study is to overcome challenges for potential end-users, such as households, farms, or industries, which can ensure direct benefits to communities via clean and renewable energy sources. It also gives an opportunity to technocrats, policy makers, practitioners, and researchers to come-up with indigenous technology and management strategies to promote DBPs.

The study presents a comprehensive analysis of the prevailing conditions of municipal solid waste litter (MSWL) management within the Indian context. The article explores the intricate web of challenges (such as increasing population, poor public awareness and policy framework) faced by urban local bodies (ULBs) in the collection, transportation, and disposal of MSWL. It also highlights the concomitant environmental threats such as health hazardous and marine pollution associated with poor MSWL management. This review elucidates the shortcomings in MSWL infrastructure, underscoring issues such as deficient waste segregation practices, inadequate disposal facilities, and the prominence of the informal waste sector. Additionally, it provides a meticulous examination of the environmental ramifications, emphasizing the dissemination of contaminants into the atmosphere, water bodies, and soil, thereby delineating the resultant health implications. Moreover, it also accentuates the significance of public participation and awareness campaigns as catalysts for MSWL reduction and segregation. Finally, the article offers a scientifically grounded resource, catering to the exigencies of policymakers, researchers, and environmentalists. It offers an empirically supported elucidation of the present state of MSWL management in India, complete with a strategic blueprint for addressing extant challenges, leveraging latent opportunities, and attenuating the scientifically substantiated environmental threats arising from MSWL.

This study aims to imply different machine learning (ML) (artificial neural network (ANN), linear regression, XGBoost, random forest (RF), support vector machine (SVM)) models to predict and optimize biogas production yield from organic fractions of municipal solid waste (MSW). The data set for six key input variables, including moisture content, C/N ratio, lignocellulose content and MSW age was analyzed and processed using ML models. Further, data exploratory analysis (EDA) analysis was performed using various steps such as data preprocessing, feature selection, train-test-validation splitting, model testing and evaluation. The results revealed that XGBoost and RF regression model exhibited superior performance efficacy. Both the models achieved a higher R2 2 values of 0.88 and 0.68, and low root mean square error (RMSE) values of 305 and 496, respectively. Furthermore, feature importance analysis was performed to identify the relative significance of input variables in biogas prediction. SVM model revealed significant contributions of moisture content (20.86 %), cellulose (60.21 %), hemicellulose (34.91 %), lignin content (62.84 %), and MSW age (17.23 %) in predicting biogas production. The findings of the study can be a resource for techno-crates/researchers to develop an efficient ML based decision-making tools for accurate predictions and process optimization.

The increase in municipal solid waste (MSW) generation rate has been a growing concern for the modern-day era. On-site composting has been the promising clean-tech alternative to managing biodegradable organic waste (BOW) in MSW. It allows sustainable and compact solutions for the in-house treatment of MSW, reducing the overall burden on landfill and treatment facilities. In this manuscript, a batch and pilot scale performance assessment study were conducted for BOW using a three-stage vertical drum composter (R1, R2, R3). The study aims to determine the impact of aeration, turning mechanisms, bulking agents, degradation rate, and process parameters on compost quality. It was found that physical-chemical properties such as bulk density (0.3 g/cm3), pH (∼7), temperature (<50 °C), moisture content (<20 %), total volatile solids (33 %), electrical conductivity (<4 dS/m) and carbon/nitrogen ratio (∼16) of final compost was under the prescribed limit. We conclude that the provision for aeration via perforated vents and regular turning mechanisms substantially impacted the quality of compost. Compost maturity was determined using humic to fulvic acid (HA/FA) ratio and germination index (GI). The HA/FA and GI of final compost in R1, R2, and R3 were found to be 6.21, 7.22, and 6.90; and 85.3 %, 90.4 %, and 87.6 %, respectively. During the degradation process, the increasing trend of HA/FA ratio (5-8) and GI (>85 %) showed that the compost quality was rich in nutrients and soil-conditioning properties. Based on the kinetic study, it was conclusive that adding bulking agents in R3 (0.0078 day-1) and R4 (0.0098 day-1) contributed to high degradation rates, underlining the value of creating a porous structure that enhances microbial activity. The findings can be a resource for waste generators, managers, technocrats, and policymakers to tackle the issues related to in-house management and treatment of MSW.

The rapid increase in quantities and the mismanagement of municipal solid waste (MSW) in developing countries are increasing the environmental impacts such as air, water and soil contamination. The present scenario of MSW management deals with numerous issues such as lack of technological resources, strategical management, social awareness, public participation, etc. Globally, numerous efforts in the form of new policies, schemes and regulatory acts have been made to develop a systematic collection and transportation (C&T) method using advanced, integrated technologies. However, very few studies have addressed this issue for low- and middle-income countries due to the lack of availability of reliable resources and data sets. This paper addresses the present challenges in C&T methods and highlights the application of information communication technology in monitoring, capturing, data management, planning, live tracking and communication. This systematic mini-review is based on the availability of technical resources, consumer acceptance and cost-effectiveness of different technologies in managing the processes. The study revealed that the C&T methods in most developed countries are designed based on their geographical stretch, climatic factors, waste characteristics and compatible technology, resulting in sustainable MSW management. However, developing countries have followed the same monotonous approach in managing their MSW, which fails in C&T process. The case study provides a valuable resource for researchers and policymakers to frame a better C&T process based on the recent technological interventions, infrastructure development, and social and economic status.

The municipal solid waste litter (MSWL) generation has been a growing concern for urban areas. It causes unpleasant aesthetic environment and health hazardous for pedestrian and residents living nearby. Although several studies related to the impact of littering on beaches and water bodies have been reported, there is insufficient information on MSWL in the urban settings. Therefore, the study was aimed to access the present status of MSWL generation and its management scheme in Nagpur, a tier two city of India. The characterization of MSWL and environmental assessment for five different categories of street was carried out using common weighted (CW) method. An environmental status index (ESI) model was developed to evaluate the existing scenario of MSWL management in urban settings. The MSWL generation rate varied from 1.5 to 4.6 kg per 100 m. The average MSWL generation rate from shopping street (SS), market street (MKS), major street (MS), residential and commercial streets (RCS), open spaces (OS) and hilly terrains streets (HTS) was found to be 62, 82, 53, 47, 78 and 42 kg/month, respectively. The ESI score for SS, MKS, MS, OS and HTS was found to be 382, 448.5, 301, 773.5 and 404, respectively. Further, the collected MSWL data set was analyzed using exploratory data analysis (EDA) to group similar data points together based on their attributes. The application of cluster (K) algorithm was found to be efficient to identify areas or regions with higher MSWL generation rate.

There is a tremendous increase in the demand for efficient and productive food supply chain due to rapid in-crease in the world population. At the same time, anaerobic digestion (AD) of discarded food waste residue (FWR) along with buffer substrate (BS) could be a sustainable way to transform waste to energy. In this study, substrate combinations (SCs) were prepared using pre (OFPre), and post (OFPost) processed FWR; anaerobic sludge (AS) as BS. The Biochemical methane potential test (BMPT) was performed for SCs prepared at varying proportion. The decline in substrate biodegradability ratio (SBR) and C/N ratio was also determined. The study was performed under three different temperature condition ranging from 35 degrees C to 73 degrees C over 90 days. It was found that SC of C5 and C6 had maximum biogas generation potential (BGP) under thermophilic (45 degrees C to 52 degrees C) temperature condition, and the cumulative CH4 production was 997 and 880 ml/g of VS. The artificial neural network (ANN) and random forest regression (RFR) were the two-machine learning (ML) tools used to predict and correlated the CH4 yield using input data series of SCs, SBR and C/N ratio. The ANN-CH4 prediction model was found to have best possible prediction efficiency.

Biofuel production can be classified into four major generations based on the type of feedstocks utilized. The first generation utilizes edible crops and involves benefits in terms of reduced CO2 emissions and secured rural energy supply; still it invites food versus fuel controversy. In this context, second-generation biofuels came to the fore, wherein the abundant lignocellulosic biomass are used, and hence it is considered as the most viable option for commercializing biofuels. However, these processes suffer from low conversion yield and long processing time. Thus, third-generation biofuels have been adopted, which have added advantage of carbon sequestration for biomass production amenable for conversion into biofuel, e.g., biofuels from microalgae. Still these technologies are not cost-competitive with their fossil counterparts owing to low biomass productivity. Thus, metabolic engineering approaches are being targeted (fourth generation) for improving the microbial strains/feedstock to make the overall process cost-competitive with fossil fuels. Metabolic engineering approaches have been targeted to improve the photosynthetic efficiency of microalgae, to enhance the light penetration, to reduce photoinhibition, and to increase the lipid content of oleaginous microbes.

The rapid increase and mismanagement of municipal solid waste (MSW) in developed and developing countries lead to environmental pollution. MSW at its initial stage can be easily converted into value-added products through an integrated approach of recycling, reuse and recovery (3R). Worldwide numerous efforts have been made to develop a systematic collection scheme using advanced integrated technologies. This paper aims to discuss the challenges and advancements in existing collection containers (household, community, and smart containers) and technological intervention in vehicle systems (front, rear, side-loading mechanism) preferably used for MSW management. The study is based on three major aspects, i.e., availability of technical resources and consumer acceptance, cost-effectiveness to manage the process, recent up-gradation and advancements. It reveals that the collection vehicles with the rear, front and side-loading lifting mechanisms are most commonly preferred in developed countries, comprising broad alleys, streets and well-planned city infrastructure. However, the handheld manual equipment (handcart and tricycle) and heavy duty vehicles (dumper/mini trucks) are primarily preferred in developing and less developing countries. The applications and working principles deliberated in this study will provide a valuable resource for researchers and policy makers to design and develop existing collection tools and technologies depending on the country's infrastructure development, social and economic status.

The application of compressed biogas (CBG) in day-to-day livelihood has garnered significant attention in modern day era. It is considered as a potential solution to curb the increasing energy demand and other environmental concerns. The process involves anaerobic digestion (AD) (hydrolysis, acidogenesis, acetogenesis and methanogenesis) of organic substrate under an optimum operating condition (pH, temperature, etc.) via anaerobic microorganisms. This paper aims to describe some major facts about different technological options related to pre-treatment, AD, cleaning and up-gradation system. It also highlights the practical challenges related to high investment cost, inadequate infrastructure, clearance and approval issues, poor feedstock supply chain management etc. in adaption of CBG plants in India. The review examines the significance of both dry and wet continuous digester systems, which includes its advantages and challenges, considering factors, such as feedstock characteristics, process stability, and operational efficiency. It was also found that the type of feedstock and its availability in existing market plays a vital role in smooth functioning of CBG plants. Therefore, the study presents a comprehensive review discussing potential feedstock readily available for CBG plants in Indian market. It was concluded that the usage of agricultural waste (such as Napier grass) has higher CBG potential compared to other feedstock. At the same time, the study presents a broader aspect to policy makers and governing authorities to reframe the existing structure for financial assistantship, regulatory laws, subsidiary schemes etc. for CBG plant owners. It also gives an opportunity to technocrats, industrialist and investors to come-up with an indigenous technology with in-house manufacturing units to promote CBG production in India.

Technological advancement has increased the usage of smart appliances which has leads to the increase in electronic waste (E-waste) generation. Informal recycling process has inefficient waste management practices compared to the formal recycling around the world. Only a very small amount of E-waste is treated with formal methods; the remaining major amount is recycled using informal methods, and the leftover are incinerated or directly dumped at dumpsites. Adults and children are involved in informal recycling of electronic and electrical equipments to reclaim value-added metals. This causes direct exposure to toxic compounds and heavy metals. If the E-waste is not treated with appropriate scientific methods, the heavy metals (lead, barium, arsenic, nickel, cadmium, etc.) and other toxic compounds can directly penetrate into the blood vessels of E-waste handlers and recyclers. This can further result in health issues such as cancer, skin disease, etc. The open dumping and recycling of E-waste using nonscientific methods have negative impact on environment and human being, which results in water, soil, and air contamination, etc. This lack of treatment and disposal technique could lead to environmental hazards that can pose a serious threat to public health and safety. Therefore, there is a urgent need to study and implement proper formal recycling methods to mitigate the environmental threats associated due to the incongruous E-waste management.

Landfills/open dump sites are the final disposal facilities for municipal solid waste (MSW). These sites undergo continuous process of biochemical reactions and anaerobic degradation, which make them prone to generation of landfill gas (LFG) and leachate. Worldwide, the quantitative and qualitative assessment for leachate treatment and management has been a growing concern. The present study investigated the physico-chemical character-istics and heavy metal parameters for fresh, 3-month, 6-month and 3-year old landfill leachate samples. The total dissolved solids (13280 mg/l), alkalinity (13000 mg/l), chemical oxygen demand (42000 mg/l) and total organic carbon (16500 mg/l) was found to be maximum in 3-year old leachate sample. While, the 3 and 6-month old leachate samples had maximum heavy metal concentration. The attempt was also made to identify the key parameters responsible to enhance biogas production yield from different ages of MSW. The substrate combi-nations of MSW and 3-year old leachate samples was prepared at varying proportion. The study was performed in three cycles and the volume of leachate diffused in each cycle was kept constant. The control samples with no leachate diffusion was also prepared to compare the percentage increase in biogas production rate. It was found that the cumulative methane (CH4) production from fresh (358 ml/g) and 3-month old MSW (273 ml/g) was maximum, and the overall percentage increase was 43% and 32%. It was also conclusive that the excess leachate diffusion of >15 ml results in low calcination behaviour and CH4 production rate. The response surface meth-odology was used to correlate and validate independent input variables (volatile solids, C/N ratio and leachate concentration) responsible for maximum CH4 yield.

The waste receiving capacity of most municipal solid waste (MSW) landfill sites in India is exhausted, resulting in the formation of larger waste heaps. In the majority of Indian cities, these old waste heaps are prone to frequent smoldering and ignition resulting into fires. In this study, the potential risk of spontaneous ignition of landfilled waste at landfill surface was analyzed based on the physico-chemical characteristics of waste, carbon monoxide (CO) levels, landfill surface temperature (LST). The leachate pollution index was also determined to analyze the leachate quality for three different seasons (monsoon, pre-monsoon and post-monsoon). The regression analysis was carried out to understand the thermal properties (smoldering temperature, smoldering time, ignition temperature etc.) of MSW. The results showed that old waste has a higher tendency to undergo ignition compared to fresh waste. It has also been observed that the lower MC of old waste samples in the range of 3.4% and 18.2% is the most likely cause of early smoldering (106.6-109.5 degrees C) and ignition (198.6-208.4 degrees C) of old waste. In pre-monsoon season, CO concentrations for sub-surface (10-30 cm depth) smoldering events (SSE) were observed to be between similar to 150 to 200 ppm. This CO level substantially dropped to 10 +/- 1 ppm in the post-monsoon season. The estimation of the leachate pollution index (LPI) showed an index score of 27.35, 30.47 and 10.71 for pre-monsoon, monsoon and post-monsoon seasons, respectively. The determination of CO levels, increased LST and physico-chemical properties of landfilled waste will greatly assist in the abatement of environmental pollution arising from landfill fires.

Open municipal solid waste (MSW) dumpsites in India are significant hotspots of spontaneous fire and associated air and ground water pollution. Unscientific dumping of MSW poses a major threat to the surrounding environment and human health. One-year-old biodegradable waste components comprised of paper, cardboard, newspaper, textile, wood, grass leaves and coconut shell were analyzed for the determination of the moisture content (MC), smoldering temperature, ignition temperature, and ignition time. Principal component analysis of the old waste components revealed that cardboard, paper, newspaper and leaves are most susceptible waste components for spontaneous ignition. In contrast, MC was the most influential parameter for resulting changes in ignition temperature (C-0) on ignition time (min). A numerical equation was developed to estimate the time required for the spontaneous waste ignition at MSW dumpsite. The results of the study showed that the aged waste (age & GE; 3 year) having MC below 6 % and initial surface temperature of 78 C-0 might smolder and ignite during the hottest time of the day in ~ 6 and ~ 26 days, respectively. Estimates showed that the time required for spontaneous waste ignition of aged waste is moderately dependent on waste MC (~5-55 %), surface temperature (~40-100 C-0), monthly pattern of average high temperature (~36.6-42.6 C-0), biodegradable waste components having smoldering temperature <= 150 C-0 and ignition temperature <= 270 & nbsp;C-0. The present study also showed that the occurrence of landfill fire events at MSW dumpsites is more prominent during the pre-monsoon season i.e. during the elevated temperature level.