Research On Intelligent And Safe Treatment Technology Of Domestic Sewage From Polar Ships

Since the middle of the twentieth century,the world has been exploring the polar regions more and more frequently.At the same time,the ship effluent discharge standards set by the International Maritime Organization(IMO)have been increasing.In order to make the domestic sewage discharged from polar research vessels meet the IMO standards,a polar ship MBR engineering prototype that can maintain high removal efficiency in polar environment is designed and improved,and an intelligent control system is assembled to investigate its nitrogen and carbon removal performance through continuous flow tests.With an effective volume of 1.862 m~3,the prototype polar ship MBR can treat waste water produced by 35 crew members every day.The prototype control system was improved,the liquid level subsystem,liquid level subsystem,temperature control subsystem,biological safety prevention and control system were regulated by PLC program,and the temperature was accurately controlled by PID method.The prototype was used to carry out continuous flow test on real domestic sewage in science and technology park to explore the operation performance under different HRT gradient and temperature gradient.The results show that the optimal hydraulic retention time is HRT1+HRT2=7+3 h,the optimal operating temperature is T=22℃,and the average effluent concentration of COD and TN reaches 57.8mg/L and 7.75mg/L through continuous flow test.The denitrification effect of the prototype is very sensitive to temperature change,and too low temperature will affect the denitrification and carbon removal effect of the prototype.When the temperature drops to the critical point of 15℃,the effluent TN rapidly rises to 22.36 mg/L.In order to maintain stable nitrogen removal performance,the prototype was equipped with temperature enhancement and insulation and the corresponding control system,and PID control was adopted to accurately regulate the temperature,so that the preset operating temperature could be stabilized.Thirdly,it was found that the nitrogen removal efficiency of the biofilm would be enhanced in the anaerobic film area in low temperature environment,which played a role in guaranteeing the system efficiency in extreme environment.Electron microscopy was used to analyze the surface of membrane components in membrane bioreactors.It was found that the selection of appropriate operating temperature and HRT was very important for the mitigation of membrane contamination and the maintenance of high membrane flux.The microbial distribution in activated sludge under different operating conditions was revealed through the analysis of biological community.The effluent was disinfected by UV-dose-photocatalysis,and the quantity of bacteria in the effluent carried IMO emission standard.The exhaust was disinfected by photocatalysis-exhaust filter element,and the exhaust reached the range required by the national indoor air quality standard(GB/T 18883-2020),effectively preventing the spread of viruses in confined Spaces.Finally,the BP neural network was used to predict the effluent quality of the prototype,and the BP-PID intelligent control system platform was built to conduct the simulation test of the effluent quality control.The effluent quality could be adjusted by adjusting the operating parameters such as temperature and HRT.At the same time,the corresponding control module could be started for different problems in the operation of the prototype.Compared with the traditional PID control,it has rapid response,short buffer time,small perturbation and almost no overshoot,which can be well adapted to the complex process operation system.It is of great significance for the new polar ship MBR prototype to maintain efficient processing performance under the complex polar conditions.