The accumulation of mine tailings on Earth is a serious environmental challenge. The importance for the recovery of heavy metals, together with the economic benefits of precious and base metals, is a strong incentive to develop sustainable methods to recover metals from tailings. Currently, researchers are attempting to improve the efficiency of metal recovery from tailings using bioleaching, a more sustainable method compared to traditional methods. In this work, the research status of using biological leaching technologies to recover heavy metals from tailings was reviewed. Furthermore, CiteSpace 5.7.R2 was used to visually analyze the keywords of relevant studies on biological leaching of tailings to intuitively establish the current research hotspots. We found that current research has made recent progress on influencing factors and microbial genetic data, and innovations have also been made regarding the improvement of the rate of metal leaching by biological leaching combined with other technologies. This is of great significance for the development of bioleaching technologies and industrial production of heavy metals in tailings. Finally, challenges and opportunities for bioleaching provide directions for further research by the scientific community.
Phosphorus, as one of the main pollutants in municipal sewage, has received increasing attention recently. Phosphorus recovery also increases the sustainable development of municipal wastewater. Since algae have the ability to effectively redirect nutrients, including phosphorus, from municipal sewage to algae biomass, municipal sewage treatments involving microalgae have piqued the interest of many researchers. The phosphorus removal depends on the potential of the microalgae to absorb, preserve, or degrade phosphorus in municipal wastewater. It is, therefore, of great interest to study the mechanisms underlying the absorption, storage, and degradation of phosphorus by microalgae to ensure the viability of this phosphorus removal process in wastewater. The objectives of this review were to summarize phosphorus metabolism in microalgae, examine key external and internal factors impacting phosphorous removal by microalgae from wastewater, and examine the status of phosphorous-metabolism-related research to improve our understanding of microalgae-based municipal wastewater treatments. In addition, the methods of recovery of microalgae after phosphorous removal were summarized to ensure the sustainability of municipal wastewater treatment. Finally, a potential approach using nanomaterials was proposed to enhance the overall phosphorous removal performance in municipal wastewater through the addition of nanoparticles such as magnesium and iron.
The safe and efficient disposal and utilization of sludge are major issues to be solved in solid waste treatment and environmental protection due to the complex characteristics of sludge and the low rate of innocuous treatments. Composting is a process of decomposing organic matter and transformed low-molecular organic acids into highmolecular humus substances under the action of microorganisms. Although land-use after composting has become an important direction for sludge treatment, heavy metal pollution is still the bottleneck problem restricting land use of sludge compost. Adding zeolite, hydroxyapatite, and other conditioning agents to the composting process affects the concentration or form of some heavy metals and effectively reduces the environmental risk. Lime and phosphorus modifiers change heavy metal speciation in samples, playing a role in decreasing biological availability and mobility. In this study, the effects of sludge composting treatment and conditioning agents on the concentrations and forms of heavy metals are reviewed. This review will provide a theoretical basis to treat heavy metals in sludge composting and lay the foundation for the land utilization and waste recycling of sludge. KEYWORDSSludge compost; heavy metal; conditioning agents; remediation Sludge treatment includes sanitary landfill, incineration, constructed wetland, composting and other methods. Sanitary landfill method has the advantages of simplicity, easy operation, low cost and strong adaptability. Although the most common method is sanitary landfilling in China, the future of sanitary landfilling is doubtful. The stability problem resulting from the poor physical nature of sludge and limited This work is licensed under a Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Research was conducted at a chicken transfer station to assess ecological treatment and resource utilization. The study examined three aspects: wastewater ecological treatment, resource utilization maximization, and process optimization. Process design and operation monitoring were carried out to treat and reuse wastewater from a chicken feeder station over two periods. The first period was operated in 2014, adopting the mode of pretreatment plus a constructed wetland. Results show that the relevant indicators basically meet the regulatory requirements at that time. The second period carried out in 2017 improved upon the results obtained during the first period. On the basis of strengthening the pretreatment and constructed wetland functions, full recycling of tailwater and zero discharge of wastewater was achieved. The aquatic plant water celery used for wetland wastewater purification function also reached the standard of safe vegetable consumption, producing systematic ecological and economic benefits. The second phase of the project has high promotion and application value in the wastewater treatment of the chicken transfer station. This study demonstrates an improved approach to poultry production wastewater treatment by transforming wastewater into an agricultural product while achieving wastewater reuse and environmental pollution control.
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