## 3 Results and Discussions
### Analysis of Petrochemical Excess Sludge Disposal  
From Section 3.1, Ah, Bl, and Cq wet sludge are not hazardous waste. Hence, there are many ways to dispose of petrochemical excess sludge. Since the petrochemical enterprise Cq mainly uses inferior crude oil as raw materials for production, the comprehensive analysis of Cq sample is considered more representative. Therefore, we selected Cq sludge sample as an example to analyze the risks of landfill, land improvement, greening mud, and incineration disposal. Analysis of Mixed Landfill, Land Improvement and Greening Mud for Petrochemical Excess Sludge Landfill  
In this study, Cq sludge was taken as an example to compare the element content of Cq sludge with the mixed landfill, land improvement and greening mud of the sludge dump. The mixed landfill and land improvement of the sludge dump, as well as the possibility of greening mud were analyzed. The content of Cq sludge sample elements is shown in Table 5. It can be seen from Table 5 that the content of As element exceeds the standard according to the standard regulations for mixed landfill, land improvement and greening sludge for sludge dumps. Therefore, it is not possible to use the sludge for mixed landfill, land use and mud for greening. In addition, the content of Al in the excess sludge is relatively high, reaching 6434.88 mg/L. The aluminum in the excess sludge is mainly from the polymerized aluminum flocculant in the sewage treatment plant. The polymerized aluminum flocculant is commonly adopted in sewage treatment plant of the refining and chemical industry. In areas where acid rain is frequent and hence the soil pH is low, aluminum is easily soluble in surface water, threatening severely to animals and plants. Noticing that the safety threshold of aluminum content in tap water is 0.2 mg/L. Aluminum can bind to proteins, and can also bind to lipids, sugars and nucleic acids, etc., interfering with some ion metabolism in plant cells, and affecting various physiological and biochemical processes. Additionally, the existing of aluminum inhibits plant root tip cell elongation and cell division, and affects the biosynthesis of plant cell walls, thereby inhibiting the growth of plants. The perniciousness of aluminum to human health is mainly reflected in the aluminum to human nervous system. Studies have shown that aluminum has toxic effects on the nervous system. Excessive contact and accumulation of aluminum may lead to neurodegenerative diseases such as senile dementia and dialysis encephalopathy; the harm of bones, excessive intake of aluminum, will deposit in the bones, so that blood phosphorus reduces bone decalcification, resulting in bone softening, bone pain, muscle weakness, and other symptoms. Therefore, the analysis of soil aluminum pollution angle, the remaining sludge is not suitable for land use and greening mud. Uranium and thorium are natural radioactive elements of the lanthanum series and are widely distributed in nature. If the contents of uranium and thorium in the excess sludge are higher than that of uranium and thorium in the soil, it will pose great harmless to animals and human beings. By analyzing the uranium and thorium elements in Cq sludge, the contents are 1.589 and 0.498 mg/kg, respectively, which were lower than the mean contents of uranium (3.03 mg/kg) and thorium (13.8 mg/kg) in Chinese soil and the mean contents of uranium (2.7 mg/kg) and thorium (9.4 mg/kg) in American soil [53].