How can the development of coal chemical industry overcome the challenges in wastewater treatment?

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Xu Yanhua is the dean of the School of Environmental Science and Engineering at Nanjing Tech University, a doctoral supervisor, a specially-appointed expert under the **\"Thousand Talents Program\"**, a member of the Coal Chemical Engineering Committee, a director of the Sustainable Development Research Association, the director of the Engineering Laboratory for Clean Coal Conversion, Water Conservation, and Emission Reduction in China’s petroleum and chemical industry, and the director of the Jiangsu Province Engineering Research Center for Chemical Pollution Control and Emergency Response. He is primarily engaged in research and development as well as engineering applications related to industrial water pollution control, treatment of toxic and malodorous industrial exhaust gases, and innovative technologies, new materials, and new equipment for the recycling of industrial solid waste. He has led the completion of numerous major projects under the **\"863\" program**, as well as other significant water-related and scientific research projects; he has won 5 provincial and ministerial-level awards for scientific and technological achievements (including 2 first prizes). He is a renowned 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 effective solutions exist? With these questions in mind, the reporter conducted an exclusive interview with Professor Xu Yanhua, a well-known expert in chemical pollution control and industrial water conservation and emission reduction in China, as well as the dean of the School of Environment at Nanjing Tech University. I disagree with a one-size-fits-all ban on evaporation ponds. Reporter: What’s your view on the environmental issues associated with the coal chemical industry at present? Xu Yanhua: Some time ago, I participated in a special investigation into coal chemical enterprises in four western provinces and regions, organized by the China Petroleum and Chemical Industry Federation, with a focus on the environmental problems faced by this 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-power 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 ecosystem is fragile with no environmental capacity. Some companies claim in their summary reports that they have achieved zero wastewater discharge, but the actual treatment processes and the fate of the recycled water are unclear and cannot stand up to scrutiny. 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 of the installation of evaporation ponds. What’s your opinion on this? Xu Yanhua: The initial purpose of installing evaporation ponds is to handle wastewater with high salt content 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 companies 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 wastewater storage areas 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 these evaporation ponds were approved for construction. As a result, some places have outright banned evaporation ponds, requiring companies to achieve absolute zero wastewater emissions. In my opinion, there are various reasons for pollution incidents in evaporation ponds; the fault does not lie 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 benchmarks, will help to change 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 waste 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 salt. 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 enterprises 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, after proper classification, treatment according to its properties, and optimization of the entire treatment process, into evaporation ponds. Technology is key to achieving near-zero emissions. Reporter: 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 terms of near-zero wastewater emissions. 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 supply 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 (Ruhrgas or British liquid slag Ruhrgas gasifiers), coal-to-oil (direct liquefaction), and coal-to-coke projects generally generate toxic wastewater containing high concentrations of phenols and amines, and traditional treatment processes of \"simple pre-treatment + 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 technologies to efficiently degrade the large amounts 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 different 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 according to 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 adopt the \"water pinch point\" technology, and vigorously promote the hierarchical use of water as well as its reuse based on different quality levels. On this basis, a plant-level water balance is established, a reclaimed water island is built, and flexible scheduling of recycled water throughout the plant is achieved.