| Since the promulgation of the "ten water rules",China’s sewage treatment and disposal industry has developed rapidly.The serious problem brought by the rapid expansion of sewage treatment plants is the sharp increase of urban excess sludge.At present,China’s sludge production has ranked first in the world.The large amount of sludge production has brought adverse effects on the urban environment,social development and people’s daily life.How to invest the treatment and disposal of urban excess sludge by source,reduction and rationalization has become a research hotspot at home and abroad.In this paper,the application of two products of urban excess sludge(carbonized sludge and dried sludge)in cinnamon soil,as well as the characteristics of plant growth,soil properties and environmental effects were studied by pot experiment,soil culture and leaching experiment.The results show that:(1)The content of organic matter,total nitrogen,total phosphorus,total potassium and alkali hydrolyzed nitrogen in the soils planted with ryegrass and rape increased in varying degrees after the application of urban excess sludge,and the effect was better when the applied amount was 20~40 t/hm~2.(2)The application of urban excess sludge can promote the growth of ryegrass and rape,increase the yield of rape and ryegrass,and the application of dried sludge can significantly increase the yield of ryegrass and rape,respectively by 106.18%~440.43% and 4.47%~140.12%.(3)The heavy metals(Cu,Cd,Cr,As,Pb,Ni and Zn)in the soil under ryegrass and rape cultivation did not exceed the national agricultural land pollution limit after the application of urban excess sludge;the heavy metals content in ryegrass plants met the national feed health standard;the application amount of dried sludge was 40 t/hm~2,the content of Zn in rape seed was 50.96mg/kg,which exceeded the limit of eight elements in grain and products(NY 861-2004).The content of heavy metals in other treatments met the limit of eight elements in grain and products issued by the Ministry of agriculture of China.(4)Through the soil culture experiment,the content of organic matter,total nitrogen and total phosphorus in the soil increased with the increase of the application amount of urban excess sludge,and the increased range was 8.19%~82.65%,9.76%~86.58%,7.89%~107.89% respectively.Adding dried sludge can reduce the p H value of the soil,increase the content of available phosphorus in the soil,and increase the content of inorganic phosphorus and its proportion in total phosphorus.It can improve the soil fertility and increase the availability of phosphorus in the soil.(5)Through leaching test,the content of total nitrogen,total phosphorus and ammonia nitrogen in leaching decreased with the increase of leaching times.The more the amount of municipal sludge applied,the higher the content of total nitrogen,total phosphorus and ammonia nitrogen in leaching. |
