The Collaborative Treatment Of Pollutants In Petrochemical Wastewater

The petrochemical industry plays a pivotal role in China’s economy as it accounts for 11%～15% of the gross domestic product.In China,there are presently more than600 industrial parks for the petrochemical industry,and they host more than half of the large-scale enterprises in the industry.The Emission Standard of Pollutants for Petroleum Chemistry Industry(GB 31571-2015)requires the indirect discharge of wastewater,but some newly built petrochemical parks depart from this standard as they have the capacity to collect and treat wastewater.In the context of carbon sequestration and pollution mitigation,it is imperative to investigate the options for effective wastewater treatment and environmental management in petrochemical parks,to promote the green and high-quality development of the petrochemical industry.Through collaborative treatment,enterprises in the industrial parks collect wastewater with minimal or no treatment and then forward it to the wastewater treatment plant in the park according to the nature of pollutants.The pollutants are then treated centrally at the wastewater treatment plant in the park to avoid penetration,interference,dilution,etc.to ensure compliance to the environmental standards upon the eventual discharge.The present work focuses on the measures to ensure safety and improve effectiveness in collaborative treatment.An evaluation framework is developed for the collaborative treatment of pollutants in petrochemical wastewater,and a petrochemical park is taken as a case study example to determine the pollutants suitable for collaborative treatment and their acceptable emission concentrations.The environmental benefits,economic benefits,and carbon emissions under different treatment modes are analyzed.The evaluation framework of collaborative treatment is established through three steps to set emission limits based on the reference methods.Firstly,the pollutant management analysis is carried out,according to database and literature research as well as the treatment process of the wastewater treatment plant in the park,to divide the petrochemical pollutants into different biochemical categories.A preliminary decision can then be made about the suitability of a pollutant for collaborative treatment.Next,the concentration conversion formula is used for pollutant to calculate if it is suitable for collaborative treatment.Finally,the allowable emission concentration is determined with reference to the Local Limit of the United States Environmental Protection Agency.The load of pollutants suitable for collaborative treatment is redistributed to determine the ultimate acceptable concentration of pollutants.In the studied petrochemical park,there are 44 petrochemical enterprises that produce 36 different pollutants.The results show that,to ensure the safety and effectiveness of wastewater treatment,the enterprises can send 28 pollutants directly to the centralized wastewater plant of the park,but they must on their own process organic halides and 1,2-dichloroethane to 4.55 mg/L and 5.07 mg/L,respectively,and treat 6other pollutants(including acrolein,epichlorohydrin,vinyl chloride,tetrachlorobenzene,nitrobenzene,Trichlorobenzene)directly to discharge standards.The environmental benefits,economic benefits,and carbon emissions of different wastewater treatment modes are compared for the studied industrial park.With the wastewater discharge meeting the requirements of the environmental regulations,the collaborative wastewater treatment creates a win-win situation for both the environment and the economy,each year saving about 40 million Yuan in cost and reducing about220,000 tons of carbon emissions from electricity alone.The evaluation framework of collaborative pollutant treatment established in this work also has good application prospects for other specialized parks that have the capacity for wastewater collection and centralized treatment.