Improve Resource Recovery Research Articles

Direct Membrane Filtration (DMF) of municipal wastewater – A study on the prevention and remediation of fouling

Direct membrane filtration (DMF) has gained a lot of attention in recent years because of its potential to treat low-strength and low temperature wastewater, where biological based treatments are inefficient. However, fouling is a major concern which keeps this technique from being more widely used. The main aim of this study was to investigate membrane fouling, its mitigation approaches and the organic/nutrient retention during DMF of municipal wastewater by adjusting operational parameters and pretreating the sewage. In a laboratory-scale setup employing crossflow to mitigate fouling, both ultrafiltration and microfiltration membranes were utilized. Physicochemical pre-treatment of sewage with polyaluminum chloride and polyamide significantly inhibited membrane fouling and improved organics/nutrient retention. Subsequent experiments with physiochemically pre-treated sewage, using microfiltration and ultrafiltration separately, revealed that (i) an increase in crossflow velocity from 1 to 2 m s −1 improved filtration performance by reducing irreversible fouling, (ii) elevating transmembrane pressure from 0.18 to 0.4 bar increased both reversible and irreversible fouling, and (iii) periodic relaxation increased the extent of irreversible fouling, contributing to higher overall fouling in ultrafiltration. When employing DMF for sewage concentration, ultrafiltration demonstrated superior filtration performance and organics retention compared to microfiltration. Furthermore, through pre-precipitation and microsieving (100 μm) followed by DMF with ultrafiltration membranes, a remarkable removal efficiency of 92 % for chemical oxygen demand (COD), 98 % for total phosphorus (TP), and 100 % for total suspended solids (TSS) was achieved. By cleaning the fouled membranes using an alkaline cleaning solution (Ultrasil-10) at 50 °C, combined with a crossflow of 1 m s−1, the permeability was completely restored. Overall, this study demonstrates that by optimizing operational settings and cleaning conditions, a sustainable DMF process for wastewater treatment with controlled membrane fouling and improved resource recovery can potentially be developed for upscaling. Short abstractThis study investigated the effectiveness of direct membrane filtration for municipal wastewater treatment. It was found that physicochemical pre-treatment with polyaluminum chloride and polyamide significantly reduced membrane fouling and improved nutrient retention. Ultrafiltration membranes demonstrated superior performance and nutrient retention compared to microfiltration membranes. By optimizing operational parameters and cleaning conditions, a sustainable direct membrane filtration process with controlled fouling and improved resource recovery can be developed for wastewater treatment.

Alkaline Pre-Fermentation Promotes Anaerobic Digestion of Enhanced Membrane Coagulation (EMC) Sludge: Performance and Microbial Community Response

Concentrating organic matter in sludge and converting it into methane through anaerobic bioconversion can improve resource recovery from domestic wastewater. Enhanced membrane coagulation (EMC) is highly efficient at concentrating organic matter, but residual coagulants (aluminum salts) can obstruct bioconversion by blocking microbial access. Limited research exists on evaluating EMC sludge bioconversion performance and addressing coagulant inhibition. This study proposes alkaline pre-fermentation to break down HO-Al-P backbones in coagulated sludge flocs, thereby improving hydrolysis and organic acid production for anaerobic digestion. Among the tested alkaline conditions (pH 9, pH 10, pH 11), pre-fermentation at pH 11 released the most organic matter (4710.0 mg/L SCOD), 20.4 times higher than without alkaline treatment. At pH 11, phosphate (61 mg/L PO43−–P) and organic acid production (2728.1 mg COD/L, with nearly 50% acetic acid) peaked, resulting in superior volatile solids removal (65.2%) and methane production (185.8 mL/g VS) during anaerobic digestion. Alkaline pre-fermentation favored alkali-tolerant bacteria such as Firmicutes and Actinobacteria, especially at pH 11, while neutrophilic Proteobacteria were suppressed. Trichococcus and Bifidobacterium, known acid producers, dominated under all conditions, with their abundance increasing at higher pH levels. Anaerobic digestion enriched fermentative bacteria like Chloroflexi and Synergistota (e.g., Thermovirga), especially in high pH reactors. Methanothrix, an acetoclastic methanogen, became the dominant methanogenic archaeon, indicating that methane production from EMC sludge primarily followed the acetoclastic methanogenesis pathway. Our findings demonstrate that alkaline pre-fermentation at pH 11 significantly enhances the hydrolysis efficiency of EMC sludge for methane recovery.

Environmental Impact Assessment of Urban Waste Recycling Challenges: A Review of DPSIR for Life Cycle Assessment of Municipal Solid Waste Recycling Challenges in Greater Monrovia, Liberia

This study evaluates the environmental impact of municipal solid waste management recycling probability in Greater Monrovia, using the Driver-Pressure-State-Impact-Response (DPSIR) framework and Life Cycle Assessment (LCA). Greater Monrovia generates approximately 236155 tons of recyclable waste annually, comprising biodegradable, plastics, paper, inert materials, and assorted waste. Inadequate infrastructure causes less waste collection, and most are openly dumped or burned, triggering severe environmental pollution. The LCA examines key impact categories, including global warming potential (GWP), water pollution, resource depletion, and human health impacts across four waste management scenarios. Scenario one (Landfill) identified significant emissions, contributing to global warming (194.86 kg CO2 eq), marine aquatic ecotoxicity (MAE) (2259578 kg 14-DB eq), and human toxicity (172.59 kg 14-DB eq). Scenario two (Anaerobic Digestion) illustrates lower impacts on human toxicity (237.83 kg 14-DB eq) and freshwater aquatic ecotoxicity (86.99 kg 14-DB eq), with moderate GWP (415.51 kg CO2 eq). In Scenario three, (Open Burning) results are the highest GWP (444.03 kg CO2 eq) and MAE (1426606.7 kg 14-DB eq), indicating substantial environmental and health risks. Scenario Four, a combined approach integrating landfill, anaerobic digestion, and open burning, optimizes the strengths and mitigates the weaknesses of each scenario, offering a balanced approach with reduced impacts across multiple categories. Findings indicate Scenario Two has a relatively moderate environmental impact. Assumed as the most preferred scenario based on the waste management option due to low environmental effects, thereby recommended as the appropriate technology for the MSW recycling process in Greater Monrovia, ultimately reducing environmental impacts and improving resource recovery.

Integrating the circular economy model into the management and treatment of Fischer–Tropsch effluents—a conversion of waste to energy (biogas) opportunity

AbstractThe Fischer–Tropsch (FT) process converts coal, biomass, or natural gas into liquid hydrocarbons via syngas generation and catalytic conversion. However, FT produces byproducts and effluents with substantial environmental consequences. This review explores the circular economy model's potential as a sustainable wastewater management strategy for FT effluent management. Furthermore, the paper investigates ameliorative measures to overcome the limitations of one biological treatment method, anaerobic digestion of FT effluents by examining the combination of nutrient augmentation, microbial augmentation, and enrichment from the integration of wastes derived from other industrial sectors as pivotal to the implementation of circular economics modelling in FT effluents valuation. This approach to the circular economy model can help overcome the environmental concerns posed by FT effluents in its advocacy of resource sharing, reuse, and recycling. This review also promotes circular economy principles to improve resource recovery, recycling, and collaboration with other industrial sectors, such as agriculture and mining, with FT application industries to create a more sustainable economy and reduce their environmental footprints. However, since the chemical compositions of wastes vary with location and other parameters, future case studies should optimize the waste mixtures to determine the optimal balance before valorizing them.

Bioponic systems with biochar: Insights into nutrient recovery, heavy metal reduction, and microbial interactions in digestate-based bioponics

Bioponics is a nutrient-recovery technology that transforms nutrient-rich organic waste into plant biomass/bioproducts. Integrating biochar with digestate from anaerobic wastewater treatment process can improve resource recovery while mitigating heavy metal contamination. The overarching goal of this study was to investigate the application of biochar in digestate-based bioponics, focusing on its efficacy in nutrient recovery and heavy metal removal, while also exploring the microbial community dynamics. In this study, biochar was applied at 50 % w/w with 500 g dry weight of digestate during two 28-day crop cycles (uncontrolled pH and pH 5.5) using white stem pak choi (Brassica rapa var. chinensis) as a model crop. The results showed that the digestate provided sufficient phosphorus and nitrogen, supporting plant growth. Biochar amendment improved plant yield and phosphate solubilization and reduced nitrogen loss, especially at the pH 5.5. Furthermore, biochar reduced the heavy metal accumulation in plants, while concentrating these metals in the residual sludge. However, owing to potential non-carcinogenic and carcinogenic health risks, it is still not recommended to directly consume plants cultivated in digestate-based bioponic systems. Additionally, biochar amendment exhibited pronounced impact on the microbial community, promoting microbes responsible for nutrient solubilization and cycling (e.g., Tetrasphaera, Herpetosiphon, Hyphomicrobium, and Pseudorhodoplanes) and heavy metal stabilization (e.g., Leptolinea, Fonticella, Romboutsia, and Desulfurispora) in both the residual sludge and plants. Overall, the addition of biochar enhanced the microbial community and facilitated the metal stabilization and the cycling of nutrients within both residual sludge and root systems, thereby improving the overall efficiency of the bioponics.

Research on Innovative Models of Waste Recycling in Urban Infrastructure

As urbanization accelerates, waste management has increasingly become a critical factor constraining sustainable urban development. Facing the growing urban population and continuous waste generation, traditional waste treatment methods such as landfill and incineration are unable to meet the modern city's demands for environmental protection and resource recycling. These methods often focus on the end stages of waste management—clearance and disposal—neglecting the importance of waste reduction at the source and resource recovery. To address this challenge, urban infrastructure must shift its approach and explore innovative models of waste recycling. These innovative models emphasize reducing waste generation at the source, improving resource recovery rates, and achieving waste minimization, resource recovery, and harmlessness. By shifting from the traditional linear economic model and viewing waste as a renewable resource, these models leverage scientific and effective means for recycling, thus achieving a win-win for economic and environmental benefits and contributing to the sustainable development of cities.

Decision-making in closed-loop supply chains: The interplay of dual government subsidies, channel Co-opetition, and brand premiums

Many governments in different countries and regions incentivize enterprises to recycle and remanufacture through subsidies to improve resource recovery efficiency. This article establishes a supply chain consisting of retailer R, manufacturer M, and third-party supplier N based on government regulations. Firstly, This paper discussed whether retailer R should establish its brand. Secondly, whether manufacturer M chooses internal recycling and whether to cooperate with competitive or non-competitive suppliers was discussed. Finally, the issue of incentive consistency was discussed from the government's perspective. This paper has established four typical scenarios: basic Scenario, cooperative competition, complete competition scenario, and tripartite Scenario. Our research results indicate that Recycling subsidies and remanufacturing subsidies have a promoting effect on retailer R's establishment of independent brands and manufacturer M's participation in internal recycling, with recycling subsidies having a more significant promoting effect on manufacturer M's participation in internal recycling. The government should control the recycling subsidy not to be too high to ensure that both manufacturer M and retailer R prefer the CO scenario and enhance the stability of the supply chain. At the same time, remanufacturing subsidies should be appropriately increased to increase social welfare.

Evaluation of the economic and environmental benefits of partial nitritation anammox and partial denitrification anammox coupling preliminary treatment in mainstream wastewater treatment

Anaerobic ammonium oxidation (anammox) technology is considered the best alternative for current wastewater treatment to improve resource recovery and energy efficiency. Evaluation of the economic and environmental benefits of partial denitrification anammox (PDA) and partial nitritation anammox (PNA) from a plant-wide perspective, which are the two most common mainstream anammox processes, is crucial for guiding the development direction of anammox, but research is still lacking. In this study, two plant-wide processes with chemically enhanced primary treatment-PDA (CEPT-PDA) and high rate activated sludge-PNA (HRAS-PNA) as the core units respectively, were firstly proposed and analysed, and life cycle assessment (LCA) was conducted to assess environmental impacts (EIs). The results of energy and economic analysis showed that the net energy consumption of CEPT-PDA and HRAS-PNA was 0.11 kwh/m3 and 0.16 kwh/m3 respectively; however, the operating cost of CEPT-PDA was 16.54% higher than that of HRAS-PNA due to the requirement for more chemicals. Compared with CEPT-PDA, the total EIs of HRAS-PNA decreased by 14.80%. The EI categories related to human toxicity and ecotoxicity contributed greatly to total EIs, accounting for 95.81% in CEPT-PDA and 96.75% in HRAS-PNA. Major environmental impacts were attributed to coagulant and energy consumption in two processes. In addition, improving the iron recycling efficiency was more beneficial for CEPT-PDA and further narrowed the gap between CEPT-PDA and HRAS-PNA on EIs. This study identifies that CEPT-PDA is competitive in the engineering application of mainstream anammox but reducing iron addition is a prerequisite.

Hydrothermal carbonization of sewage sludge: Optimization of operating conditions using design of experiment approach and evaluation of resource recovery potential

Scientific disposal of sewage sludge (SS) is a tedious task worldwide. Landfilling of the SS after centrifugation may have serious adverse impacts on the environment. The present study investigated efficacy of hydrothermal carbonization (HTC) as pretreatment for the centrifuged sewage sludge with an aim to improve resource recovery. In this study, both solid and liquid fractions recovered after the HTC were subjected to the detailed analysis for examining the opportunities for recovery of value-added chemicals and biogas. The HTC conditions were optimized using design of experiments (DOE) approach. The runs were performed in a high-pressure reactor at 160–240 °C temperatures and total pressures of 6.1–34.2 kg/cm2 for 1–3 h duration without supply of air. The optimum HTC temperature and duration were found to be 200 °C and 1 h, respectively. Under these conditions, the dried hydrochar (HC) had higher heating value of ~13 MJ/kg. Its properties were found similar to that of the sub-bituminous coal based on the atomic ratio of elements. The HTC pretreatment resulted in substantial reduction in carbon and oxygen due to decarboxylation, dehydration and oxidation (due to oxygen present in reactor headspace) reactions. The process wastewater (PWW) recovered after HTC at the optimum conditions had high concentration of the recoverable value-added compounds such as humic acid (HA) and PO43--P (concentration = 20 g/l and ~0.5 g/l, respectively). Moreover, significant quantity of biogas could be generated from the PWW. Hence, hydrothermal pretreatment can be considered a potential option for SS valorization.

Sensor-Based Technologies in Effective Solid Waste Sorting: Successful Applications, Sensor Combination, and Future Directions.

The increase in global population and improvement of living standards have stirred up a continuous increase in solid waste generation, while simple incineration and landfilling bring about serious environmental and health concerns. In order to improve resource recovery and mitigate pollution, noncontacting and nondestructive sensor-based waste sorting systems are applied to enhance solid waste classification. In recent years, in addition to the rapid development of computer hardware, especially improvements of GPU computing capacity, complicated and efficient classification algorithms have emerged and been widely used in industrial sectors. These advances allow computers to process signals from sensors more quickly and accurately and to classify matters automatically. This article introduces widely applied sensor-based technologies in solid waste sorting and analyzes applicable conditions for each specific method. The latest developed algorithms are critically compared with competitive counterparts. Successful practices are described, and findings are highlighted. Though spectroscopic-based and vision-based waste classifications have achieved high performance in accuracy and detection speed, challenges and future directions can still provide wide development opportunities. Concretely, these opportunities generally comprise classification of indistinct plastics, application of the latest object detection algorithms, appropriate data set formulating, and sensor combination for multiple sorting tasks within a single system.

Effect of Wettability Heterogeneity on Water-Gas Two-Phase Displacement Behavior in a Complex Pore Structure by Phase-Field Model

Understanding the immiscible displacement mechanism in porous media is vital to enhancing the hydrocarbon resources in the oil and gas reservoir. Improving resource recovery requires quantitatively characterizing the effect of wettability heterogeneity on the immiscible displacement behaviors at the pore scale, which can be used to predict the displacement distribution of multiphase fluids and evaluate the optimal wettability strategy in porous media. The heterogeneity of fluid wettability in a natural rock makes it extremely hard to directly observe the fluid displacement behaviors in the reservoir rocks and quantify the sensitivity of preferential displacement path and displacement efficiency to wettability distribution. In this study, the phase-field model coupling wettability heterogeneity was established. The gas-water two-phase displacement process was simulated under various wettability distributions and injecting flux rates in a complex pore structure. The effect of wettability heterogeneity on immiscible displacement behavior was analyzed. The results indicated that wettability heterogeneity significantly affects the fluid displacement path and invasion patterns, while the injecting flux rate negatively influences the capillary–viscous crossover flow regime. The continuous wetting patches enhanced the preferential flow and hindered displacement, whereas the dalmatian wetting patches promoted a higher displacement efficiency. The results of the fractal dimensions and specific surface area also quantitatively show the effects of wettability distribution and heterogeneity on the complexity of the two-phase fluid distribution. The research provides the theoretical foundation and analysis approach for designing an optimal wettability strategy for injecting fluid into unconventional oil and gas reservoirs.

Reusing ethanol-water and recovering residual gum in hemp degumming

Traditional hemp degumming creates large volumes of effluent. Chemical treatment and discharge of the degumming solution is still a challenging task. In this work, ethanol-water solution was reused for hemp degumming and gum recovery was explored to reduce effluent volume and improve resource recovery. The influences of recycling times on fiber color, morphology, mechanical properties, thermal properties and dimensional properties were investigated. Also, the characterizations of the extracted lignin were conducted. The results indicated that pectin could be removed in every degumming cycle. Above 86% of cellulose could be achieved in the five degumming cycles and fiber tenacity increased with each consecutive cycle from 35.6 to 43.6 cN/tex. Most importantly, spherical lignin particles could be extracted from the solution of the last degumming cycle with an average diameter of 249.7 nm. This work contributes to green degumming of bast fibers, reducing degumming cost and value-adding of the lignin-rich residues.

Stability and Cementation of the Surrounding Rock in Roof-Cutting and Pressure-Relief Entry under Mining Influence

The application of roof-cutting and pressure-relief gob-side entry retention plays a critical role in controlling the stability of the surrounding rock at the entry, easing continuity tension and improving resource recovery ratio. The excavation of the 360,803 airway in Xinji No. 1 Mine is affected by intense mining of the 360,805 working face. Hence, to address the stability problem of surrounding rock in the 360,803 airway, rock mass blast weakening theory was used in this study to analyze the blasting stress of columnar charged rock mass and obtain the radiuses of crushed, fractured, and vibration zones under uncoupled charging conditions. The reasonable array pitch, length, and dip angle of boreholes were determined according to the pressure-relief range of the blasting fracture. The migration laws of roof strata were explored based on a mechanical model of overlying roof strata structure on the working face. Subsequently, the horizon, breaking span, and caving sequence of hard roof strata were obtained to determine the roof-cutting height of this entry. On the basis of the theory of key stratum, the number of sequences at the roof caving limit stratum and hanging roof length in the goaf were calculated, the analytical solution to critical coal pillar width was acquired, the evaluation indexes for the stability of entry-protecting coal pillars were determined, and the engineering requirements for the 25 m entry-protecting coal pillars in the 360,803 airway were met. Moreover, various indexes such as roof separation fracture, displacement of surrounding rock, and loose circle of surrounding rock in the gob-side entry were analyzed. The stability and cementation status of surrounding rock in the 360,803 airway were evaluated, and tunneling safety was ensured.

Typology of municipal solid waste recycling value chains: A global perspective

Municipal solid waste (MSW) management that seeks to recover wasted resources and return them to the system as secondary commodities (hence, it promotes circularity in resource recovery systems) is a process instigated by recycling value chains. Recycling value chains are termed as the chain of processes (i.e., value chain activities and performance) and structures (formal/informal networks of stakeholders) created and shaped by the relations of stakeholders operating across the value chain, aimed at connecting production with the management of recyclable waste resources. At present, recycling processes and structures are not well depicted in the global literature due to the heterogeneity of terms used across countries and disciplines, and the lack of holistic insight into the way recycling chains operate. This critical review aims to disentangle the diverse terminology used to describe recycling value chains globally and provides an overview of the current state-of-the-art of MSW recyclable waste materials management in developed and developing economies emphasising their potential in promoting circularity. The study proposes a typology for describing the management of recyclable waste materials across the globe, and highlights that each of the three types of recycling value chains developed is a highly complex, context-specific system, deeply constructed on long-term political, organisational, and institutional aspects. While this typology can be a simplistic way of depicting the type of recycling value chain that is most prevalent in different countries around the globe, it can reveal how different forms of governance affect coordination in recycling networks and, by extent, their recycling performance. Therefore, this study can help researchers and decision-makers understand how recycling value chain systems operate at large and explore different ways to improve resource recovery from waste that match the needs of each area.

Coupling anaerobic fluidized membrane bioreactors with microbial electrolysis cells towards improved wastewater reuse and energy recovery

Anaerobic Membrane Bioreactors (AnMBRs) combine the advantages of anaerobic processes and MBR technology to improve effluent quality and energy recovery. However, these systems are associated with operational challenges such as membrane fouling and loss of dissolved methane that increases operation and energy expenses. In this study, a new configuration was developed combining AnMBRs with Microbial Electrolysis Cells (MECs). The effectiveness of the coupled AnFMBR-MEC system was tested by monitoring several indicators during the treatment of synthetic wastewater. The new configuration exhibited a 25-day shorter startup period, a 56% enhanced average methane yield, and a reduced membrane fouling with a maximum transmembrane pressure value nearly 6.5 folds lower than that exhibited by the AnFMBR alone. AnFMBR-MEC had an average CE of 40% and both reactors achieved around 90% COD removal. Similar bacterial communities existed in both reactors but with different relative abundance and localization. In the AnFMBR-MEC, the Direct Interspecies Electron Transfer was the likely dominant route for acetate consumption due to the abundance of Geobacter and Methanosarcina on the granular activated carbon and in suspension. The new system offers a promising technology with less fouling and improved resource recovery from wastewater due to the presence of different environmental niches (GAC, anode, cathode) for microbial colonization and growth, which resulted in the reduction of biomass in suspension and the proliferation of electroactive bacteria and methanogens as biofilms.

Spatial modelling of municipal waste generation: Deriving property lot estimates with limited data

Given recent circular economy policy and waste minimisation targets, there is a significant opportunity to fundamentally change the way waste is managed in Australia, and re-focus waste management to promote resource recovery and efficiency. Detailed data on household waste generation can assist decision makers in targeting waste minimisation incentives, improving resource recovery and circularity, identifying specific technology and infrastructure gaps and informing future development. Unfortunately, high-resolution spatial estimates of waste generation at the property lot scale is typically unavailable. This study presents a novel spatial model developed to estimate waste generation data at the property lot level. Utilising census data at multiple spatial scales and council waste generation data, we apply our model to estimate quantities of residual waste, dry recyclables and garden waste generated for more than 1,200,000 property lots in the Sydney metropolitan area, Australia. Results show the spatial distribution of estimated household waste generation, achieving a high degree of accuracy when compared to validation data. To illustrate the application of our results in the context of identifying ideal areas for waste processing facilities, we analyse the spatial distribution of available garden waste arising from property lots. An area of intense garden waste generation was identified, indicating a supply area of approximately 13km2 in northern Sydney that can support a facility of approximately 20,000t throughput a year. Our analytical approach presented is novel, and has practical application for locating waste processing facilities; analysing efficient kerbside waste collection services; and in informing data driven urban waste management strategies.

Investigation on hydrochar and macromolecules recovery opportunities from food waste after hydrothermal carbonization

In this paper, the performance of hydrothermal carbonization (HTC) was investigated on real food waste (FW) to improve resource recovery opportunities. The HTC was performed in a high pressure batch reactor (without addition of water) at desired temperatures for different durations to study the properties of solid hydrochar (HC) and process water (PW) produced during the process. The reaction temperature and run time of 200 °C and 1 h, respectively were found suitable to produce the HC (high heating value = ~30 MJ/kg) having properties similar to that of the peat/lignite coal. Moreover, durable pellets could also be prepared from HC without addition of binder. The kinetic constants for HC combustion were also predicted using non-isothermal model-free approach for the data obtained from thermo-gravimetric analysis. In the PW samples recovered after HTC, several value-added compounds like 2,5-hydroxymethyl furfural, humic-like substances (HLS), proteins, carbohydrates and volatile fatty acids could be detected in appreciable quantities. However, longer reaction resulted in further degradation of above macromolecules into VFAs. Based on the observations, a pathway for FW degradation during HTC process is proposed. Moreover, the HLS and proteins mixture recovered from the PW sample exhibited no adverse impact on seed growth. The present study demonstrates that the HTC can be a potential treatment method for FW to recover a variety of useful materials. Further studies should focus on developing cost-effective methods for the recovery of various macromolecules from PW.

Hydrothermal carbonization of centrifuged sewage sludge: Determination of resource recovery from liquid fraction and thermal behaviour of hydrochar

Safe disposal of the sludge generated from sewage treatment plant is a major challenge worldwide. Hydrothermal carbonization (HTC) is considered a potential pretreatment alternative for sewage sludge to facilitate the improved resource recovery. In the present study, the mixed centrifuged sewage sludge (CSS) was subjected to the HTC pretreatment to determine characteristics of the solid hydrochar (HC) and liquid fraction (LF) with a purpose of energy recovery and extraction of value-added compounds, respectively. HTC was performed in a high pressure batch reactor at 200 °C temperature for 1–8 h duration. The HC produced after HTC resembled with the low quality peat coal whereas the LF contained value-added chemicals such as humic acid (HA) and phosphate phosphorous (PO43—P). Using ammonium sulphate as ‘salting out’ agent, ~70% of the total HA (~15–16 g/L) could be recovered from the LF. Using the recovered HA, an improvement in the root and shoot lengths of the seeds could be observed. In the subsequent step, the total PO43−-P recovery of ~80% was obtained as struvite from the residual wastewater.

4D-BIM to enhance construction waste reuse and recycle planning: Case studies on concrete and drywall waste streams

Despite pressing attention on construction waste management (CWM) issues, low rates of construction waste (CW) reuse and recycling (R&R) remain a limitation in construction projects. In recent years, Building Information Modeling (BIM) has gained momentum for CWM purposes; its data-richness, visualization, and simulation capabilities provide an opportunity to enhance CW R&R planning at the project level. In this context, this study proposes temporal-based algorithms integrated with 4D-BIM for the planning of concrete and drywall waste R&R throughout construction projects. Two case studies from Central Texas were used for the demonstration of the algorithms, and estimates were validated with ground truth data and literature values from different projects in North America. The overarching objective of the proposed algorithms is to streamline estimation and visual planning of CW for on-site reuse, and off-site recycling – therefore promoting a more proactive and schedule-based CWM plan. In addition, the approach improves team communication around CWM goals of the project. Moreover, through the use of 4D-BIM, on-site waste reuse opportunities are planned in advance, thus, improving resource recovery and minimizing waste disposal in landfills.

Improvement of resource recovery rate for underground coal gasification through the gasifier size management

Underground coal gasification is one of the most vital technical directions for the future development of the coal industry. Currently, numerous small-scale underground coal gasification industrial tests of different processes have been successively conducted, which has laid a solid foundation for further large-scale experiment and production. However, with the expansion of underground coal gasification experiment scale and promoting application, the surrounding rock stability and surface subsidence must be considered. Moreover, there exists a bottleneck problem, which should be solved urgently, that how to design underground gasification production for different geological conditions to improve resource recovery rate. To solve this issue, this paper analyzed the existing situation of resource recovery rate of industrial experiment for underground coal gasification without shaft. Also, the improvement method for resource recovery rate of underground coal gasification with considering of the gasifier safety and surface subsidence was proposed in combination with the technology characteristics of underground coal gasification. Meanwhile, the influence rule of gasifier parameters on the coal pillars stability and surface subsidence was revealed. From the findings in this research, it can be expected that the resource recovery rate of underground coal gasification without shaft can be increased from about 40% to more than 60% under the both conditions of the safe production of underground gasifiers and surface subsidence control. These research results are of great significance for enhancing the economic benefits of underground coal gasification and promoting its industrialization and large-scale production.