The Development And Application Of Organic Fertilizer Using Urban Domestic Sludge In Zhongwei City

At present,there are many problems in the process of sludge composting,such as unclear sludge properties,different effects of technical parameters of composting and composting operation process on sludge composting process and product quality,which lead to incomplete technical scheme,parameters and industrial chain of sludge composting,and lack of application specifications of sludge organic fertilizer.To solve these problems,this study investigated the sludge properties,sludge composting test and pot experiment to study the annual nutrient and heavy metal content changes of sludge.The effects of various factors on the internal environment,nutrient and heavy metal contents,the verification of fertilizer efficiency and the application of organic fertilizer in the process of composting provide technical parameters and theoretical basis for the production of sludge composting in cold and arid areas.The main research results are as follows:(1)The average contents of total nitrogen,total phosphorus,total potassium and organic matter in annual sludge are 30g/kg,300mg/kg,5.79g/kg and 63.9%respectively.The contents of nutrients and heavy metals varied with the seasons,showing a pattern of high in autumn and low in spring.The contents of heavy metals were all lower than the national standard limit for agricultural sludge.The potential ecological risks of heavy metal Nemero composite index and comprehensive factors of sludge were light pollution and low hazard risk.(2)The ratio of straw,particle size and tipping process all affect the heating rate,high temperature duration,water content and compost cycle of the pile to varying degrees.The particle size has the greatest influence on the effective accumulated temperature of the pile,and the ratio of 15%straw,particle size of 5cm and standing for 6d are the most favorable for compost heating.In the process of composting,the water content of the upper,middle and lower layers of the pile presents a spatial gradient.The dumping process will break the formation of the spatial gradient of the water content of the pile,and the vertical spatial gradient of the water content of the pile standing for 6 days is small.(3)Compared with the operation process,the ratio and particle size of straw have a greater effect on the contents of organic matter,ammonium nitrogen,nitrate nitrogen and total nitrogen.The content of nitrate nitrogen in the composting process increased with the composting process,and the increase range of each treatment was 696.8mg/kg～1264.1 mg/kg.The increase of straw ratio will accelerate the conversion of ammonium nitrogen to nitrate nitrogen in the reactor.The loss of total nitrogen was faster in the early stage,and the germination index GI curve of all treatments showed a trend of decreasing briefly at first and then increasing continuously.Among them,treatment 7(the optimal condition was 15%ratio+5cm straw+conventional turning)had the least loss of nitrogen(0.04g/kg).Seed germination index was the highest,reaching 1 13%.(4)In the process of composting,the content of heavy metals in each treatment is far lower than the national standard limit.In the later stage of composting,the content of heavy metals increased due to the material concentration,and the content of heavy metals in each treatment decreased somewhat after 10 days of composting than after 1 day of composting.DOM ultraviolet absorption intensity of the pile body showed a trend of increasing first and then decreasing between 200 and 400 cm-1.The peak values of all treatments were at 210 nm,254nm,280nm and 340nm.The ratio of straw,particle size and operation technology all affect the transformation of humus in the reactor to different degrees.(5)All treatments of organic fertilizers had promoting effects on plant height,diameter diameter and biomass of potted spinach.With the increase of the amount of organic fertilizer added,the plant height,diameter diameter and biomass of spinach also increased.By comparing the effects of different supplemental amount of each treatment on the yield increase of spinach,the optimal supplemental amount of organic fertilizer in treatment 7 was 30g/kg.