The construction of “zero-waste city” is a crucial step in advancing ecological civilization and building a Beautiful China. It is also a key measure for achieving synergistic effects of pollution and carbon reduction. China’s current work plans and indicator systems for “zero-waste city” construction provide essential guidance and serve as the primary basis for evaluating “zero-waste city” development effectiveness. They encompass the comprehensive management and treatment of both newly generated and existing solid waste. However, central government inspections on eco-environmental protection during the 14th Five-Year period have revealed several issues in the management of existing solid waste, including illegal dumping, incomplete remediation of historical waste, overburdened landfills, and inadequate leachate management. These problems highlight shortcomings in policies, planning, and design related to existing solid waste management, underscoring the urgent need for improvement. The significance of existing solid waste management in achieving the objectives of “zero-waste city” construction based on the present state was discussed, and the inclusion of “existing solid waste management” as a primary indicator in the current indicator system was proposed, which subdivided into three secondary indicators, namely “existing municipal solid waste management”“existing construction waste management” and “existing industrial solid waste management”, further detailed into six tertiary indicators. Meanwhile, the implications of these new indicators were deeply explored and their feasibility through case studies were demonstrated. This improvement will enhance the policy guidelines of “zero-waste city” construction, motivate more cities to strengthen existing solid waste management, and support the high-standard development and realization of “zero-waste city”.

In response to the issues of unclear construction and operational status of food waste treatment facilities and the excessive government subsidies affecting decision-making management, the operational data from 530 centralized treatment facilities and 3 971 decentralized treatment facilities nationwide, with a-total treatment capacity of 1.411×105 t/d was systematically collected and analyzed. The results have indicated that the average load rate of existing treatment facilities is below 70%. Centralized treatment facilities primarily operate at a scale of 100-<300 t/d. The application of technologies ranking as follows: anaerobic digestion>co-incineration>aerobic fermentation>biotransformation. The unit investment intensity is concentrated in the range of 300 000-<800 000 yuan/t, and the median government subsidy for waste treatment is 232 yuan/t. Decentralized treatment facilities generally face technical challenges such as high energy consumption, unstable output quality, incomplete product evaluation systems, and difficulties in odor pollution control, and they are mainly suitable for specific scenarios where centralized treatment is not economically feasible. The study has found that low revenue from resource recovery products is a key factor driving high government subsidies. It is recommended to implement cost-reduction and efficiency-improvement measures, such as increasing subsidies for biogas resource utilization and developing low-cost treatment technologies, to narrow the gap with incineration treatment subsidies. The research results can provide data support and decision-making references for optimizing the layout of food waste treatment facilities and subsidy policies.

The safety of university laboratories is fundamental to fostering high-quality talent and sustaining the production of high-impact research outcomes. To bolster the management capabilities for mitigating safety risks in university laboratory zones, a novel safety risk assessment framework was introduced based on an extensive risk profiling of 135 laboratories in Nanjing. This framework encompassed six primary indicators: fundamental safety conditions, hazardous materials management, equipment, facilities and processes, safety risk mitigation, emergency preparedness, as well as personnel safety competencies. These primary indicators were further refined into 29 secondary indicators and 67 objective evaluation criteria. Additionally, a scoring protocol and computational methodology was formulated to mitigate subjectivity in the assessment process. Through comprehensive evaluations and comparative analyses of results from three laboratories across two universities, the scientific rigor and applicability of the new framework were validated. The evaluation results underscored that the framework could effectively assign scientific ratings to laboratory safety risks and accurately reflect the risk status of laboratories across various dimensions. This new framework is adaptable to different types of laboratories, addressing the issues of previous assessment standards being vague and indicator sets being incomplete, thereby significantly enhancing the level of granular safety management in university laboratories.

Food waste valorization is crucial for achieving zero-waste initiatives and implementing waste management strategies. Carbon chain elongation, particularly for producing medium-chain carboxylic acids like caproate, presents a promising biorefinery pathway for converting food waste into value-added chemicals. Among the various approaches, lactate-mediated chain elongation has garnered significant interest due to its potential advantages, including enhanced process controllability and high electron donor utilization efficiency. Although lab-scale research has confirmed the feasibility of this technology and demonstrated progress, challenges impede its transition to industrial-scale application. This review summarized the current status of lactate-mediated chain elongation for caproate production and critically analyzed the key bottlenecks hindering its scale-up. Major challenges include: adaptability and microbial utilization of complex substrates, precise process control and real-time monitoring, the efficiency and stability of functional microbial communities, and economic constraints imposed by high chemical and energy consumption. Addressing these critical issues is key to advancing this technology towards industrial-scale implementation.

A kitchen waste treatment project in China has adopted three dry anaerobic fermentation technologies, including Kompogas horizontal push flow single axis stirring, TTV tunnel kiln single axis stirring, and Dranco vertical cone bottom forced circulation stirring, to recycle kitchen waste with high organic matter content in urban waste classification. By comparing the equipment integration and operating parameters of three dry anaerobic technologies, their technical application characteristics and advantages were analyzed and explored. By comparing the process and equipment characteristics, TTV and Dranco medium temperature dry anaerobic systems could achieve more stable operating parameters, which were superior to Kompogas high-temperature dry anaerobic systems. The blade of TTV anaerobic tank was set to fit the tank body, which could effectively avoid the deposition of heavy substances and prevent blockage of discharge. Dranco vertical anaerobic tank ensured the homogeneity of materials through forced circulation and achieved rapid inoculation. The sludge dewatering process used vibrating screens, spiral extruders, and centrifugal dewatering machines for more stable results. By comparing the operating parameters and indicators, TTV and Dranco achieved stable operation at full load. The VS degradation ratio of the three anaerobic technologies were basically the same. The key evaluation indicators of TTV have obvious technical advantages, with a volumetric gas production rate of 5.44 m3/m3, an anaerobic tank feed volatile solid load (based on VS) of 10.47 kg/（m3·d）, and a volatile solid decomposition rate of 75.77%. Both TTV and Dranco achieved high solid content in dehydrated residue, with an average of 37.31% and 37.19%, respectively. In combination with the actual processing volume of kitchen waste, the biogas slurry production and solid content of TTV were lower than those of Kompogas and Dranco. Through economic comparison, the management and maintenance cost of TTV was 16.2 yuan per ton, and the operating consumption cost was 33.42 yuan per ton, which was significantly better than Kompogas and Dranco.

Wet waste includes restaurant food waste and household kitchen waste. The existing wet waste anaerobic resource treatment project has an oil extraction process for restaurant food waste, but not for household kitchen waste. Based on a wet waste anaerobic resource utilization project in Shanghai, the impact of engineering operations safety before and after setting up oil extraction processes for household kitchen waste were analyzed, including the operational safety of anaerobic biological systems (which could be reflected by observing the changes in volatile fatty acids, alkalinity and the oil content of the biogas liquid), and operation safety of aerobic biological treatment system for biogas slurry (which could be reflected by the changes in dissolved oxygen). Analysis showed that the oil content in kitchen waste slurry was approximately 1.5%-3.0%,which was necessary to add an oil extraction process, otherwise, it would lead to an increase in volatile fatty acids and a decrease in alkalinity in the anaerobic system, making the system unsafe. The high oil content in the biogas slurry seriously affected the oxygenation effect of the sewage treatment system, and the dissolved oxygen in MBR system nitrification tank was below 0.5 mg/L, resulting in poor treatment efficiency and even the possibility of the biological system collapsing. The economic analysis indicated that the unit price of crude oil (based on waste) ranged from 4 000 to 8 000 yuan per ton. Considering both the income from crude oil and the operating costs, the revenue per ton of waste was 37.20-94.20 yuan. The methane production rate increased by approximately 12%. The frequency of ultrafiltration membrane contamination in the biogas liquid MBR treatment system decreased by approximately 40%. The research could provide references for the engineering design and operation of new or renovated projects of this type.

A large-scale aged landfill site in Southern China was taken as an example. Based on the analysis of groundwater quality survey data, a variety of low-concentration pollutants (such as ammonia nitrogen, COD, volatile phenols, manganese, etc.) were detected in the groundwater. Considering the advantages and disadvantages of mainstream groundwater remediation technologies both domestically and internationally, the pump-and-treat technology was selected as the optimal choice. A process system consisting of “aerobic biofluidized bed + electrocatalytic oxidation + reverse osmosis”was constructed to achieve the simultaneous and highly efficient removal of multiple pollutants in groundwater (removal rate of approximately 100%). The effluent water quality indicators were below the Class III water quality limits specified in table 1 of GB/T 14848—2017 Standard for Groundwater Quality, meeting the design requirements. This work findings could provide valuable technical references for groundwater remediation projects of similar landfill sites.

he mainstream disposal method in China at present is to have the fly ash from the incineration of domestic waste solidified and stabilized and then be sent to the sanitary landfill for compartmentalized landfill. However, in engineering practice, the stacking slope ratio of fly ash often follows the ratio of 1∶3 that is more suitable for municipal solid waste, which the landfill storage capacity has not been maximally utilized. The stability of fly ash slope and final cover under different slope ratio, as well as the influence of length-to-width ratio and area of landfill reservoir on the storage capacity were analyzed. The research results showed that based on the geotechnical properties of fly ash itself, the designed value of the stacking slope ratio of fly ash could be adjusted from 1∶3 to 1∶2, or even to 1∶1, thus significantly increasing the storage capacity of the fly ash landfill. Considering the stability of the final cover layer of the fly ash landfill after its closure, the recommended stacking slope ratio of fly ash was 1∶2. The storage capacity of the fly ash landfill decreased with the increase of the length-to-width of the storage area, and the smaller the area of the landfill area, the greater the decrease in storage capacity.

The sludge drying and incineration technology has significant characteristics of sludge reduction, stabilization, and harmlessness, which has become a key research and important development direction in the field of sludge treatment and disposal in China. Whether from the perspective of process or investment, sludge drying equipment plays a crucial role in the success or failure of sludge disposal projects. Three sludge treatment processes using blade, thin film and disc drying technology were studied and discussed from the perspectives of equipment structure, material and energy balance, process flow, control methods and future thermal drying applications, in order to provide reference for the construction and technology selection of similar projects.

The rapid aerobic stabilization treatment of aged waste is a biochemical process that involves injecting air and water into the landfill waste heap to activate the reactive activity of aerobic microbial communities, accelerate the degradation of organic components and achieve physical and chemical stabilization. Rapid aerobic stabilization plays an important role in aged waste restoration and treatment projects, whether as the main process of in-situ ecological restoration or as a pre-treatment process of ex situ restoration. The traditional aerobic stabilization equipment for the treatment of aged waste usually has disadvantages such as high civil foundation requirements, long installation and positioning cycles, and inconvenient transportation during transfer. In order to overcome these disadvantages and achieve functional requirements such as rapid installation, direct operation, overall transfer, and remote monitoring, based on the design concepts of modular, intelligent, integrated, and efficient, the improvement design and the engineering application of aerobic stabilization equipment was carried out, to achieve the goal of improving engineering efficiency and save engineering costs.

To enhance the resource utilization rate of recyclable materials in municipal solid waste and optimize the recyclable materials collection and transportation facility system, two improved maximum coverage models were adopted to conduct layout optimization research for recyclable materials transfer stations in Chaoyang district, Beijing. Based on the current layout status of recyclable materials facilities, the accessibility of transfer stations was analyzed to determine their service coverage areas. Taking population-weighted recyclable materials collection points as demand points and actual road networks as transportation paths, seven layout optimization schemes for transfer stations were proposed. The results demonstrated that all schemes achieved optimization of transfer station layouts. Specifically, scheme A exhibited the shortest transportation time (3 747.34 minutes), while scheme C achieved the minimum construction cost (16.84 million CNY).

Resource recycling and utilization is a key link in the construction of a “zero-waste city”, while the recycling and utilization of recyclable materials is a shortcoming in the work of waste classification. Taking typical areas as the entry point, through on-site investigation, experimental analysis and other methods, the generation and classification of recyclable materials in residents’ domestic waste were studied, and their components, physical and chemical properties were analyzed. The results indicated that the proportion of recyclable materials (9.9%-24.5%) in the components of domestic waste in Guangzhou’s sanitation collection system has gradually decreased over the past 10 years, with high-value recyclables averaging 6.73% and low-value recyclables exhibiting a decreasing trend. From 2021 to 2023, the proportion of high-value recyclables in domestic waste generated in G street (21.20%-33.34%) has been increasing year by year, while the proportion of low-value recyclables has decreased. According to the analysis of waste classification components in the black bins of G street, the proportion of recyclable materials has decreased from 23.73% to 15.80%, with paper, plastic, and metal all decreasing year by year. Regarding physical composition, the content of rubber and plastic (28.58%-31.28%) was relatively high, while the proportions of paper and glass were slightly higher.The physicochemical analysis of six waste categories showed that waste paper had the highest moisture content (38.94%±3.30%), while the high calorific value of plastic bags and plastics dry basis was higher than the average value of domestic waste. The ash content of plastic bags and paper scraps was relatively high, while the other four categories remained around 1.00%. The concentrations of Pb and Hg (on a dry basis) in plastic bags were the highest, measured at (11.75±6.18) mg/kg and (0.063±0.086) mg/kg, respectively. The total Cr and As contents of fabrics was the highest, and the mixture of plastic bags, fabrics and other materials into terminal incineration would increase the heavy metal toxicity of fly ash and slag. The results of this study can provide reference for selecting appropriate recycling methods for recyclable materials, while improving their recycling rate and economic value, and assisting in the construction of a “zero-waste city”.

In recent years, flue gas recirculation technology has been widely applied in waste to energy plants, which could effectively reduce NOx emissions. However, the corrosion of flue gas recirculation equipment has affected the effect and stability of the technology application, so it is urgently needed to explore the causes of corrosion and countermeasures. The flue gas recirculation system of a waste to energy incineration plant in Guangdong province was taken as the research object. The causes of equipment corrosion were analyzed from the perspectives of equipment selection, process layout, operation specifications and so on. Countermeasures were proposed in the directions of design and operation regulation. In design, equipment leakage should be reduced， and protective wind and drainage pipes should be set to reduce corrosion. In operation regulation, strict compliance with the design operating conditions should be ensured for long-term operation.

During the operation of domestic waste incineration plants, the chimney will appear “white smoke”, causing the public to misunderstand environmental pollution. The engineering analysis was carried out from the aspects of the source of white smoke, the influencing factors of white smoke emission and the control method. The results showed that the quality of white smoke was negligible compared to the atmosphere, and its concentration could not affect the local meteorological conditions. The control of white smoke only met the sensory needs and consumed a lot of energy, which played a negative role in energy conservation and emission reduction. The problem of white smoke is not an environmental problem, but a public awareness problem.

To address the issues of large time delays, complex chemical reactions, and multiple influencing factors on the outlet NOx concentration in the selective non-catalytic reduction (SNCR) denitrification system for waste incinerators, a dynamic modeling method based on maximum information coefficient (MIC) and bi-directional long short-term memory network was proposed. Firstly, by analyzing the SNCR denitrification mechanism and influencing factors, the variables related to outlet NOx were preliminarily selected. Then, based on the MIC algorithm, variables with strong correlation with outlet NOx were selected and redundant variables were removed. Next, the sliding window method and MIC algorithm were used for data delay estimation to complete the data reconstruction. Finally, a dynamic model of the SNCR denitrification system was built based on the bi-directional long short-term memory deep learning algorithm.The results showed that after variable screening and delay estimation, the accuracy of the dynamic model was significantly improved, and the average absolute percentage error of the model was approximately 8.62%, which decreased by 18.6%, 18.1% and 12.5% compared with the BPNN, LSTM and GRU models, respectively. Therefore, this modeling method has higher precision and better fitting effect, which can be more effectively applied to the actual field.