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In India, majority of the generated municipal solid waste (MSW) was dumped in poorly managed landfills and dumpsites over the past decades and is an environmental and health hazard. Landfill mining is a promising solution to reclaim these sites along with the recovery of resources (materials and energy). During landfill mining operations, the combustible fraction is one of the major components recovered and needs proper management for maximizing resource recovery. For the identification of appropriate resource recovery options, knowledge of the physicochemical characteristics is required. The present study aims to assess the depth-wise change in the composition of legacy waste and the physicochemical characteristics of the combustible fraction. Furthermore, a material flow analysis considering the incineration of combustible fraction was performed to estimate the energy generation potential and the associated greenhouse gas (GHG) emissions. The results of the compositional analysis of dry legacy waste revealed that the fine fraction (<4 mm soil-like material) was dominating with a share of 36%. The depth-wise analysis showed a decrease in the calorific value with increasing landfill depth, while no specific trend was observed for the other parameters analyzed, including proximate and ultimate analysis, and chlorine content. The material flow analysis performed for 100 tonnes of wet legacy waste indicated that 52 tonnes of waste is combustible fraction. The GHG emissions through incineration of one tonne of dry combustible fraction would be 1389 kg CO 2 -eq, with 1125 kWh of electrical energy generation potential. [Display omitted] • Changes in physicochemical characteristics with landfill depth were assessed. • The legacy waste had a high share of combustible fraction accounting for 52%. • The combustible fraction was found to be suitable for WtE treatment and use as RDF. • One tonne of legacy waste showed a potential to generate 428 kWh of electricity. • Incinerating one ton of combustible waste can emit 1389 kg CO 2 -eq of GHG emissions. [ABSTRACT FROM AUTHOR]

Increasing water stress and high energy requirements in urban water systems (UWSs) makes it imperative to reduce water demand by adopting wastewater reuse. However, there is a gap in the existing literature about analysing the operation of hilly urban water systems (UWSs) and suggesting energy efficient and environmentally benign wastewater reuse strategies. The objective of this study is to investigate the water-energy-greenhouse gas (GHG) nexus for different wastewater reuse strategies in UWS located in the Indian Himalayan region. Potential scenarios for the direct potable and non-potable reuse in the region were analysed. The system boundary consisted of the construction and operation phase inputs. The functional unit of the study was 1 m3 of water supplied to the UWS. The data inventory was developed using process designs, site specific information, engineering calculations and commercial databases. The total embodied energy and total GHG emissions were estimated using the existing models based on mass balance approach. The hilly UWS uses 17.6 kWh/m3 of total embodied energy and emits 6.2 kgCO 2 eq/m3 GHG emissions in its present operation. Over 90% of energy and GHG emissions were associated with pumping, which is required to cover over 1000 m of elevation head. The combined reuse scenario comprising both non-potable and direct potable reuse had the lowest embodied energy use and GHG emissions with a magnitude of 12.9 kWh/m3 and 4.3 kgCO 2 eq/m3. By comparative assessment of potential reuse scenarios, the study provides rationale for adopting appropriate strategy based on water savings, energy use, and environmental interventions. [Display omitted] • Assessment of urban water system in hilly terrain integrated with wastewater reuse. • Analysis of non-potable reuse, direct potable reuse and hybrid reuse scenarios. • Water pumping was the energy and GHG emission hotspot. • All but direct potable reuse had less energy and GHG emissions compared to baseline. • Hybrid reuse from the STP close to township had the lowest energy and GHG emissions. [ABSTRACT FROM AUTHOR]

• Life cycle cost (LCC) analysis of MSW treatment systems was conducted for Mumbai. • Scenario with recycling and landfill was economically preferred than others. • Scenario with recycling, composting and incineration was the most cost-intensive. • Sensitivity analysis was done to measure the impact of crucial factors on net LCC. This study quantifies and compares the cost of municipal solid waste (MSW) management systems under different scenarios using life cycle cost (LCC) analysis approach. LCC analysis was performed for six integrated MSW management scenarios for Mumbai city, India which generates over 9000 metric tonnes of MSW daily and disposes most of it in open dumps. The scenarios are the combinations of recycling, composting, anaerobic digestion, incineration with electricity generation, and landfill with biogas recovery. To perform LCC analysis of scenarios, present worth method was used. The present worth of operations and maintenance (O&M) cost and revenue generated was estimated using a discount rate of 11.25% for a 20-year life span. Results show that the incineration based scenario is the most cost-intensive option with a net LCC of US$38 per tonne of MSW due to the high capital cost involved in case of incineration. While the scenario with a combination of recycling and sanitary landfill was the most economically viable option with a net LCC of US$19 per tonne of MSW due to comparative lower operating cost. The sensitivity analysis shows that the O&M cost was the most sensitive parameter and a change of ±10% and ±20% in O&M cost, the net LCC of scenarios changes in the range of 14–33% and 29–65%, respectively. This study provides an economic comparison of MSW treatment scenarios from a life cycle perspective, which facilitates the decision-making process for improvement in cost estimation and planning of waste management strategies in India. [ABSTRACT FROM AUTHOR]

The utilization of municipal solid waste (MSW) and sewage sludge (SS) as a source of renewable energy is crucial in achieving sustainable and integrated MSW management. SS and organic fraction of municipal solid waste (OFMSW) can be anaerobically digested to produce methane for energy. However, anaerobic digestion of specific substrates is challenging with respect to substrate characteristics. The problem of mono-digestion can be mitigated by co-digestion of these two major organic wastes because of their complementary characteristics. Moreover, there is a lack of studies on optimization of different mix ratios of organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) based on total solids (TS). The study aims to optimize the mix ratio for anaerobic co-digestion of OFMSW and SS. The study further elucidates synergistic effects associated with the co-digestion process. Different mix ratios of SS and OFMSW (0:100, 20:80, 40:60, 60:40, 80:20, 100:0) at 5, 7.5 and 10% TS were assessed for biomethane potential assessment. The results showed that with an increase in SS in the mix ratio feed the methane yield increased by 91% and 50% as compared to mono digestion of sewage sludge and OFMSW respectively at TS 7.5%. Based on the kinetic analysis, it was observed that the lag phase reduced for 60:40 mix ratio leading to higher rate of biodegradation. Positive synergistic effects were observed for 40:60, 60:40 and 80:20 mix ratio of SS:OFMSW based on co-digestion impact factor value. Response surface modelling was used to get the optimized mix ratio and TS %. The optimum mix ratio with the highest methane yield (388 ml/gVS added) was 70:30 (SS: OFMSW) at TS 7.5% with a desirability value of 0.98. These findings demonstrate that co-digesting SS and OFMSW is a preferable alternative for harnessing renewable energy and managing organic waste in a sustainable manner. [Display omitted] • Co-digestion of sewage sludge (SS) and organic fraction of municipal solid waste (OFMSW). • Six mix ratios and three total solid (TS) concentration analyzed. • Synergistic affects observed in co-digestion of different mix ratios. • Highest methane yield at 7.5 TS% with 60:40 (SS:OFMSW). • Response surface modelling provides the optimized mix ratio and TS%. [ABSTRACT FROM AUTHOR]

• Effect of ageing on different physicochemical characteristics of the excavated waste. • Fine fraction (<4 mm) accounted highest ∼45%, while metal content was <1%. • Assessment for the valorisation of the recovered waste streams. This paper assesses the effect of ageing on physicochemical characteristics of excavated municipal solid waste from Mulund dumpsite in Mumbai, India. Based on disposal year, waste was excavated from different zones in the dumpsite. The excavated waste was screened into five different size categories and further sorted into different streams. Physicochemical characteristics, i.e., pH, bulk density, ultimate and proximate analysis, calorific value and heavy metal concentration of excavated waste were also determined. The results indicate a change in the characteristics and composition of waste with age. The particle size distribution of waste revealed that waste above 80 mm was mostly plastic and textile, whereas <4 mm (fine fraction) composed of soil-like material. Above 80 mm fraction shows a decreasing trend with age and depth, suggesting particle size reduction with time. Parameters like volatile matter, total and organic carbon and calorific value of excavated waste also reduced with the age. A significant portion of waste was fine fraction (∼45%) emphasising on its valorisation for success of landfill mining. Furthermore, metal content in the dumpsite was <1%. The findings from this study can be used to reclaim dumpsites and suggest possible valorisation routes for excavated waste in developing countries like India. [ABSTRACT FROM AUTHOR]

The study evaluates mobility and chemical speciation of heavy metals (HMs) in fine fraction (<4 mm) collected from municipal solid waste dumpsite located in Mumbai, India to assess its reclamation feasabilty. A total of fifteen samples were collected from five zones (named chronologically, zone A to zone E, with the increasing waste age) at 1-m depth interval to understand temporal variation in mobility and potential pollution risk of heavy metals. The results depicted that Zn had the highest concentration in the fine fraction, followed by Cu > Cr > Pb > Ni > Cd. Furthermore, HMs concentration showed increasing trend with the waste age. According to hiererachial cluster analysis, two cluster were observed in the analyzed samples which could be differentiated with age of the waste. Further, the chemical speciation differed for all assessed HMs and had a significant change with age. HMs were dominant in non-bioavailable forms, except for Cd that had significant distribution in all forms. In addition, Cd (23%) and Zn (17%) showed high mobility amongst all analyzed HM, while Cr (0.4%) had the least. According to pollution assessment and chemical speciation results, Cd was identified as the most polluting and mobile HM. The study shows that the mobile form of HMs is low and needs to be considered while deciding the remediation routes and environment hazards. [Display omitted] • The effect of aging on heavy metal chemical speciation and the ecological risk was studied. • Heavy metals showed distinctive speciation characteristics in the dumpsite. • Cadmium had the highest mobility and leaching potential in the dumpsite. • The heavy metal in fine fraction poses low to moderate risk towards the environment. [ABSTRACT FROM AUTHOR]

Old landfills and dumpsites, created due to a linear approach towards municipal solid waste (MSW) management, are one of the major environmental hazards, especially in developing countries. Around 50% of the dumped waste can be characterized as fine fraction (FF), making its recovery a vital parameter for achieving a circular economy. This study investigates the application of FF obtained from the Indian MSW dumpsite to replace topsoil used for fired brick production, which is one of the primary construction materials in India. The raw materials (FF and clay) were mixed in different proportions and fired at a temperature of 800–1000 °C. Physicochemical, mechanical and environmental properties were analyzed for fired bricks using standard methods. Results showed that the fired bricks produced from FF had low density and thermal conductivity than control bricks providing advantages over conventional bricks for transportation and energy savings. The compressive strength (CS) of the bricks increased with an increase in temperature and reduced with an increase in FF, suggesting only a certain amount of clay can be replaced. Hence further optimization using response surface modelling was carried out. The optimization results showed that clay could be substituted up to 23% at 1000 °C (CS = 37.5 N/mm2) by FF to meet Indian regulatory limits for CS. Toxicity characteristic leaching procedure test showed that fired bricks produced from FF are safe for application. The study shows that FF can substitute part of clay in fired brick production, which can help to curb topsoil exploitation while achieving a circular economy by bringing dumped FF back to the anthropogenic material cycle. [Display omitted] • Fine fraction recycling from dumpsite as construction material. • Thermal and mineralogical characterization of raw materials (fine fraction and clay). • Mechanical performance of fired bricks produced from fine fraction and clay. • Response surface modelling (RSM) for optimizing fine fraction utilization. • Environmental assessment for bricks manufactured from fine fraction. [ABSTRACT FROM AUTHOR]

Developing nations are advancing towards improving municipal wastewater treatment infrastructure. However, there have been limited efforts in these countries to understand Water-Energy-GHG nexus for sustainable wastewater treatment. This study evaluates operational energy, total embodied energy and corresponding GHG emissions of a widely implemented municipal wastewater treatment technology in Mumbai Metropolitan Region of India. Data for wastewater inflow, total energy consumption and materials used in the unit processes of the treatment plant were collected and analysed. Direct GHG emissions from the plant were estimated using the method proposed by the intergovernmental panel for climate change (IPCC). The energy embodied within the materials used in the construction and operations of the plant was estimated using country-specific information. The results show that the energy intensity for plant operation and chemical oxygen demand (COD) removal was 0.23 ± 0.05 kWh/m3 of wastewater treated and 1.12 ± 0.77 kWh/kg of COD removed, respectively. The embodied energy in chemicals and building materials during the plant's life cycle contributed 19% of the total embodied energy. Wastewater inflow with specific average energy consumption in wet-well pumping and blowers showed a negative and positive correlation, respectively. The total GHG emissions (direct and indirect) from the plant were ~0.22 kgCO 2 eq/m3 of wastewater treated. The study presents the energy accounting of a wastewater treatment system and extensive analysis of infrastructural data, which is scarcely accessible and available in developing countries. • Gate to gate analysis of Water-Energy-GHG nexus in a wastewater treatment plant. • Electricity consumption in wastewater treatment units is correlated with the inflow. • Operational energy consumes maximum energy consumption and GHG footprints. • Resource recovery essential to offset energy consumption and related footprints. [ABSTRACT FROM AUTHOR]

Sewage sludge, generated post wastewater treatment, constitutes only a small percentage of the total amount of sewage treated, however, its sustainable management is inevitable. In this study, the energy recovery potential of sewage sludge by incineration and anaerobic digestion is investigated for India. The dewatered sludge has total solid content of 25–45% whereas, the primary characteristics of sewage sludge showed significant organic content of about ∼23–40% (dry basis). The calorific value was found to be 8–21 MJ/kg for sludge dry matter. The energy recovery potential of sewage sludge was 555–1068 kWh/tonne on sludge dry matter basis for incineration and 315–608 kWh/tonne for anaerobic digestion. Additionally, the energy recovery potential of current sewage treatment in India was found to be ∼15.3 × 105 or 8.6 × 105 MWh, annually for incineration and anaerobic digestion, respectively. The study had provided in depth view of sludge to be considered as energetic material and its energy recovery potential countrywide, which would not only help for give a proper direction for recovering energy but also helpful to deal with the issue of sludge management in India. Image 1 • Sludge generated from sewage treatment plants was explored for energy alternatives. • The sewage sludge contains high heating value, organic matter and volatile matter etc. • Energy recovery potential of sewage sludge produced in India was estimated. • The energy recovery from sewage sludge could reduce energy demands and reduce land requirement for its disposal as well. [ABSTRACT FROM AUTHOR]