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——An interview with Xu Yanhua, a renowned expert in chemical pollution control and dean of the School of Environment at Nanjing Tech University. Xu Yanhua is the dean of the School of Environmental Science and Engineering at Nanjing Tech University, a doctoral supervisor, an expert appointed under the “Thousand Talents Program,” a member of the Coal Chemical Industry Committee, a director of the Sustainable Development Research Association, as well as the director of the Engineering Laboratory for Clean Coal Conversion, Water Conservation, and Emission Reduction in China’s petroleum and chemical industry. He is primarily engaged in research and development, as well as practical application, of new technologies, materials, and equipment for controlling industrial water pollution, treating toxic and malodorous industrial exhaust gases, and recycling industrial solid waste. He has led the completion of numerous major projects under programs such as the “863” Program, key water-related projects, and other major scientific and technological initiatives. He has won 5 provincial and ministerial-level awards for scientific and technological achievements (including 2 first prizes), and is considered a leading expert in the fields of chemical pollution control and industrial water conservation and emission reduction in China. Since the beginning of this year, the environmental impact assessments for many coal chemical projects have been rejected by the Ministry of Environmental Protection. For the development of coal chemical projects, environmental issues are an obstacle that cannot be ignored. What are the current challenges related to environmental issues in the coal chemical industry? What are the effective solutions, exactly? With such questions in mind, the reporter conducted an exclusive interview with Professor Xu Yanhua, a renowned expert in China’s fields of chemical pollution control as well as industrial water conservation and emission reduction, and Dean of the School of Environment at Nanjing Tech University. Disagree with a one-size-fits-all ban on evaporation ponds. Reporter: What’s your view on the current environmental issues associated with coal chemical industries? Xu Yanhua: Some time ago, I participated in a special research mission organized by the China Petroleum and Chemical Industry Federation to coal chemical enterprises in four western provinces and regions, focusing on the environmental issues faced by the coal chemical industry. After 7 or 8 days of research, my overall feeling is mixed. It is gratifying that many coal chemical enterprises have made significant breakthroughs in the localization and scaling up of key technologies and equipment such as gasification and conversion. Some coal chemical industry clusters have carried out active and fruitful explorations in coal-electricity cogeneration, the development and expansion of coal-based products, as well as the complementary coexistence between the coal chemical industry and the petrochemical industry. The concern is that the industry faces severe environmental problems; water scarcity and water pollution have become key constraints to its development. In some regions where coal chemical industries are being developed vigorously, on the one hand, there is a severe shortage of water resources, and on the other hand, the ecosystems there are fragile and lack environmental capacity. Some companies claim in their summary reports that they have achieved zero wastewater discharge, yet the actual treatment processes and the fate of the recycled water are unclear and unverifiable. Due to the lack of effective monitoring and regulatory measures, it is difficult to determine the actual efficiency of wastewater treatment in enterprises, the rate of recycled water reuse, and the water consumption per unit of product, which is a concerning situation. Reporter: The pollution problem in the Tengger Desert has made evaporation ponds the target of criticism. It is said that some coal chemical projects were rejected precisely because evaporation ponds were planned for them. What’s your opinion on this? Xu Yanhua: The initial purpose of constructing evaporation ponds was to handle wastewater with high salinity and low chemical oxygen demand. In the northwestern regions of our country, where evaporation rates are high, utilizing solar energy to enable the natural evaporation and concentration of wastewater can **save businesses the costs associated with installing evaporation equipment as well as the operating expenses related to evaporation crystallization. For coal chemical projects that require large investments but yield relatively low returns, the use of evaporation ponds provides a practical solution for companies to treat high-salinity wastewater at low costs. Regrettably, some enterprises mistakenly use evaporation ponds as temporary storage tanks for wastewater or accident ponds, discharging large amounts of highly concentrated wastewater into them; in some cases, this has even led to environmental pollution incidents, completely going against the original purpose for which those evaporation ponds were approved for construction. As a result, some places have outright banned evaporation ponds and required companies to achieve absolute zero wastewater discharge. In my opinion, there are various reasons for pollution incidents in evaporation ponds; the fault lies not with the ponds themselves. Inadequate monitoring and supervision, as well as insufficient supporting policies, are important contributing factors. Wastewater with truly low chemical oxygen demand, low toxicity, and high salinity in evaporation ponds generally does not pose a serious threat to the ecological environment. Therefore, a one-size-fits-all approach to evaporation ponds has certain issues in terms of scientific validity, rationality, and practical feasibility. The key is to strengthen monitoring and supervision to ensure that the water quality and quantity of wastewater discharged into the evaporation ponds meet the specified requirements. Furthermore, formulating appropriate supporting policies to impose higher pollution fees on enterprises that exceed emission limits or discharge excessive amounts of pollutants, or to impose certain penalties on them, while providing corresponding subsidies and incentives to those that meet the emission standards and reduce their emissions, as well as implementing tiered pricing based on the amount of fresh water consumed by enterprises relative to the established standards, will help to reverse the current situation in coal chemical enterprises, where there is abuse of evaporation ponds and a lack of pressure or motivation to save water and reduce emissions. Achieving near-zero emissions is more scientific and reasonable. Reporter: There is still controversy within the industry regarding zero emissions and near-zero emissions – what is your opinion? Xu Yanhua: Zero wastewater discharge means that no waste water or liquid is released outside the factory; in other words, even concentrated brine cannot be discharged outside, and all such concentrated brine must be evaporated and crystallized. However, relying on evaporation devices for evaporation desalination results in investment and operating costs that are often unaffordable for enterprises, and there is currently no good solution for the crystallized salts. Under current environmental regulations, such salt residues are classified as hazardous waste and must be disposed of by specialized hazardous waste treatment facilities. Due to high disposal costs, not only do companies bear a heavy economic burden, but local disposal is also difficult to achieve because the capacity for disposing of hazardous waste is severely insufficient in many areas. Recently, some organizations have been accelerating research on the technology for selective crystallization of high-salinity wastewater, in order to find ways to recycle the crystallized salts. However, these studies are still in the pilot and pilot-scale stages, and further evaluation of their technical economics and the feasibility of practical engineering applications is needed. Given the above circumstances, and taking into account the needs for ecological and environmental protection, the actual pollution control capabilities of coal chemical enterprises, as well as the current level of environmental protection technologies, I believe that it is more scientific, reasonable, and feasible to achieve near-zero wastewater discharge by sending the small amount of concentrated wastewater with high salt content and low chemical oxygen demand, which meets the regulatory standards, into evaporation ponds, on the basis of strict implementation of classified wastewater collection, treatment based on different wastewater types, and optimization across the entire process. Technology is key to achieving near-zero emissions. Journalist: So what suggestions do you have for achieving near-zero emissions from coal chemical industry wastewater? Xu Yanhua: At present, coal chemical projects still face many challenges in achieving near-zero wastewater discharge. Firstly, the design of wastewater treatment and the design of the main processing processes are usually not carried out by the same entity, resulting in a disconnect between the design tasks and a lack of seamless integration. For a near-zero emission project, the wastewater treatment system is highly integrated and interconnected with the main production equipment. The water intake points, pollution generation points, reclaimed water reuse points, as well as sewage collection, treatment, and reuse should form an organic whole. Only by considering wastewater treatment and the main process design as a whole and designing them simultaneously is it possible to achieve true near-zero emissions. Secondly, existing wastewater treatment processes generally suffer from problems in terms of specificity and effectiveness. Coal-to-gas (Ruhlig furnace or British liquid slag Ruhlig gasifier) projects, coal-to-oil (direct liquefaction) projects, and coal-to-lantern carbon projects generally generate toxic wastewater containing high concentrations of phenols and amines, and traditional treatment processes of \"simple pretreatment + biological treatment\" often fail to operate stably and effectively. Even with complete subsequent membrane treatment and evaporation desalination processes, it is difficult to achieve near-zero emissions. A prominent technical issue is the lack of necessary preprocessing. Selecting effective and cost-efficient enhanced pretreatment techniques to efficiently degrade the large amount of toxic organic substances in wastewater can significantly improve the efficiency and operational stability of subsequent biochemical treatment systems. The aforementioned wastewater often contains not only high concentrations of organic toxins but also large amounts of oily substances and suspended particles (coal dust, coal powder), which frequently cause scaling and blockages in the phenol-amine recovery units, preventing the system from operating stably. Therefore, effective and cost-effective pretreatment technologies must be employed to efficiently remove the large amounts of oily substances and suspended solids from the wastewater prior to the phenol-amine recovery unit, in order to ensure the efficient and stable operation of the phenol-amine recovery equipment as well as the subsequent wastewater treatment systems. Once again, current wastewater treatment processes often suffer from technical fragmentation and low integration levels. Existing coal chemical projects are implemented in segments by multiple units, resulting in poor compatibility among the technologies of these various units, difficulties in effective integration, and a low level of integration overall. Some enterprises fail to properly separate pollutants from clean water, collect wastewater in a categorized manner, or treat it based on its different qualities; they focus on end-stage treatment while neglecting water conservation during the processing process. In my opinion, to achieve water conservation and emission reduction, it is necessary to optimize the entire process of wastewater treatment, apply principles of systems engineering, actively introduce the \"water pinch point\" technology, and vigorously promote the hierarchical use of water as well as its recycled use based on different quality levels. On this basis, a plant-wide water balance is established, a reclaimed water island is built, and flexible scheduling of recycled water across the entire plant is achieved.