Analysis on wastewater discharge standards and treatment technologies of petrochemical industry at home and abroad
At the Water Affairs Forum, Zhou Yuexi, deputy chief engineer of the Chinese Academy of Environmental Sciences, pointed out that the petrochemical industry is a key industry for pollution control and water conservation that is clearly required by the “Water Tenâ€. Water pollution control has become a bottleneck factor restricting the sustainable development of the chemical industry. There is an urgent need to construct a complete process control technology system for wastewater pollution in the petrochemical industry.
US Petroleum Refining Industry Water Pollutant Emission Standard
Similarly, the petroleum refining industry is also an important basic industry in the United States. The petroleum refining industry water pollutant discharge standards have been promulgated very early, and have made important contributions to water pollution reduction. The US petroleum refining industry water pollutant discharge standards are compiled in the Federal Code (CFR Part 419). The main control items are as follows:
The law has the legal effect of enforcement and is widely applicable to the petroleum refining industry. In addition, the standard is a dynamic and increasingly stringent standard. The US Environmental Protection Agency regularly reaffirms these standards and, based on improvements in technology, revises the standards as necessary to ensure that the standards are practicable.
China's petrochemical industry water pollutant discharge standards
In order to prevent and control the environmental pollution of petroleum refining industrial wastewater, China's earliest "Water Refining Standard for Petroleum Refining Industry", which was implemented on October 1, 1983, was later adopted by GB 8978-1996. Replaced by the Standard. Later, China issued more than 30 industrial water pollutant discharge standards, but did not include the petroleum refining industry. However, the "Integrated Sewage Discharge Standard" alone has only COD for the pollution index of the petroleum refining industry, while the rest implements comprehensive standards, which do not take into account the characteristics of the petroleum refining industry.
The HJ 2045-2014 "Technical Specification for Petroleum Refining Industrial Wastewater Treatment Engineering" implemented on March 1, 2015 stipulates the technical requirements for the design, construction, acceptance and operation management of petroleum refining industrial wastewater treatment projects.
GB31570–2015 “Pesticide Emission Standards for Petroleum Refining Industry†and GB 31571-2015 “Pesticide Emission Standards for Petrochemical Industryâ€, which were implemented on July 1, 2015, stipulates petroleum refining industrial enterprises and petrochemical industrial enterprises. Water pollutants and atmospheric pollutant emission limits, monitoring and supervision and management requirements for their production facilities. The water pollutant discharge standards of newly-built petroleum refining industrial enterprises are shown in Table 2:
Table 2 Standard unit for water pollutant discharge of newly-established petroleum refining industrial enterprises (excluding pH)
Singapore Petrochemical Wastewater Treatment Technology
As an important refining base in Southeast Asia and one of the world's major refining and petrochemical hubs, Singapore has the world's leading refining companies including ExxonMobil, Shell, Chevron and Total. However, Singapore has a small country and a serious shortage of water resources. Therefore, the achievements in industrial refinery water treatment are worth learning.
Singapore's sewage has undergone a rigorous four-pass treatment process, and finally it becomes a safe water that can be reused or even directly consumed. The four treatment processes are: first, traditional wastewater treatment; second, microfiltration technology, using a filtration membrane to remove water suspension. Granules, colloidal particles, pathogenic bacteria, viruses, etc.; the third is reverse osmosis treatment, using semi-permeable membrane to filter out pollutants in the water; the fourth is UV disinfection, further ensuring water quality and ensuring water purity.
The treated water is called "new water." According to expert appraisal, the water quality indicators of new water produced in Singapore are superior to the tap water currently used, and the cleanliness is higher than the drinking water standards of the US Environmental Protection Agency and the World Health Organization. In addition, the School of Environmental Studies of the National University of Singapore has conducted research on petrochemicals and refining water, such as advanced water and wastewater treatment technologies for water reuse.
China's petrochemical wastewater treatment technology
In general, for refractory petrochemical wastewater, China often uses biological treatment as the main process, physical and chemical methods as pretreatment and advanced treatment.
Physical processing techniques mainly include membrane separation, air flotation, oil separation and adsorption. The air floatation method is a commonly used method for pretreatment of petrochemical wastewater, with low cost, high treatment efficiency and no secondary pollution. The same applies to the oil separation method, but the oil slick collected by the method is hazardous waste and needs to be disposed of by a qualified unit. Membrane separation technology and adsorption method have a good treatment effect on odor and chromaticity in petrochemical wastewater, and the removal rate of organic matter and suspended matter is also high. However, the operating cost is high, and it is necessary to periodically replace the membrane and the activated carbon, and it is easy to cause secondary pollution. Among them, activated carbon adsorption is generally used for subsequent deep treatment.
The chemical treatment technologies mainly include: oxidation method and flocculation method. The oxidation method can effectively remove the chromaticity and odor in the water, and can also oxidize the material which is difficult to be biodegraded in the wastewater, and has strong adaptability to the change of the water quantity and the rapid reaction speed. Among them, the ozone oxidation method is used more and is mostly used for advanced treatment of petrochemical wastewater. Removal of organic matter flocculation method using a coagulant, turbidity and color of water, is used mainly inorganic coagulant agents (such as aluminum sulfate, ferric chloride, etc.) and an organic agent (polyacrylamide).
Compared with other treatment methods, biochemical treatment technology has the characteristics of large processing capacity, good processing effect, simple operation management and low operating cost. Mainly divided into aerobic method, anaerobic method and combined process. Commonly used anaerobic treatment technologies include UASB, AF, anaerobic fluidized bed and other processes. Commonly used aerobic technologies are: A / O method, SBR, oxidation ditch, activated sludge method. Since the anaerobic process can improve the biodegradability of the sewage, an anaerobic-aerobic combination process is often used. For example, the chlorination acidification-aerobic tank-aeration biofilter process is used to treat petrochemical wastewater. The results show that the COD removal rate is above 90%, the ammonia nitrogen removal rate is above 70%, and the sulfide and volatile phenol are also higher. Removal rate.
In recent years, China's water resources utilization has been in a state of tension. After the researchers have treated some petrochemical wastewaters in a moderate and in-depth manner, they directly treated them as water in other petrochemical production links. At present, China's environmental protection enterprises in the coal chemical, petrochemical and other difficult wastewater treatment, regardless of research and exploration of new technologies, trying to introduce zero-emission solutions for petroleum wastewater, to achieve water recycling and reuse.
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