| Phosphorus is a necessary element for the growth of animals and plants,and it is also an important industrial raw material.With population growth,economic prosperity,and continuous development of industry and agriculture,the demand for phosphorus will increase in the future.The sewage treatment system is an important link connecting the social application of phosphorus and the natural cycle.The sludge disposal of the sewage plant has an important impact on the phosphorus cycle.This paper studies the influence of different sewage treatment plant sludge disposal methods on the phosphorus cycle,and proposes technical recommendations for sewage treatment systems for the purpose of promoting the phosphorus cycle.This paper collects and analyzes data on phosphorus production,phosphorus content in sewage and sludge,and sludge disposal methods from 84 countries and regions around the world.On this basis,the material flow method is used to establish the phosphorus in the corresponding sewage treatment system.The flow model identifies the different structures and efficiencies of the phosphorus metabolism system in the sewage treatment system;collects and analyzes the operating parameters of sewage treatment plants in 200 countries and regions,and further studies the economic and geographic influence of different sewage treatment processes.On the basis of the above results,technical recommendations for sewage and sludge treatment and disposal suitable for different countries and regions have been put forward.The research results show that the ratio of phosphorus to total phosphorus flow in the sewage treatment system in Bolivia in America is the highest,reaching 76%;Hungary in Europe has the highest sludge land utilization rate,reaching 86.8%.The sewage treatment process also affects the flow of phosphorus,because its removal efficiency of phosphorus affects the concentration of phosphorus stored in the remaining sludge.The weighted standardized removal efficiency of different sewage treatment processes was calculated,and it was found that both the activated sludge method(0.057)and the biofilm method(0.053)showed good performance in the removal of total phosphorus.In the world,the activated sludge method is the most widely used compared to several other sewage treatment processes.Considering the influence of economy and geographical location,the biofilm method has the best overall removal effect of pollutants among several sewage treatment processes,and is relatively less affected by economy and geographical location;natural biological treatment is greatly affected by economy and geographical location.Based on the above research on sewage and sludge,considering the actual situation of phosphate rock resources and land area,it is recommended that countries with low phosphorus resources such as Norway,Germany,Canada,the United Kingdom,France,Italy,Spain,etc.give priority to sewage and sludge.The technologies are the biofilm method and landfilling.Countries with developed economies but limited land areas such as Denmark,the Netherlands,Austria,and Belgium are capable of incinerating sludge.Although Saudi Arabia,Russia,Brazil,and Kazakhstan are rich in phosphate rock resources and have a vast land area,their economic development is low.The land use and sanitary landfill of sludge are suitable for these countries.For countries with abundant phosphorus resources,sewage sludge treatment and disposal technologies that meet the national conditions of different countries must be considered in consideration of environmental factors. |
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