| Sludge as a by-product is produced in the process of sewage treatment,moisture content is about 98% above.High moisture content is based on the zoogloea formed a variety of microorganisms and its adsorption of organic and inorganic mixes together to form a collection.If the sludge is piled up at random,it will cause serious pollution to the environment,and poses a threat to human health.Nitrogen and phosphorus nutrition elements flow into the water excessively,eutrophication will appear.After organic matter going through a long-term fermentation decay,fetor and breeding flies may bring hidden danger to the environment.As a result,the sludge treatment and disposal which is regarded as a environmental problem should be solved urgently in the contemporary era.This paper is to improve the sludge dewatering performance by ultrasonic sludge processing and reduce the moisture content of sludge for subsequent processing which leads the reduction of space and save of the processing costs.While the sludge flocculation structure destroyed,intracellular substances such as organic matter are released into the liquid phase making its content in the liquid phase increases.After ultrasonic treatment on the sludge supernatant reflux returns back to the A/O reactor inlet as a supplement of carbon source for denitrification.In this experiment,the activated sludge from secondary clarifier is used to while inspecting the ultrasonic sludge parameters optimization under a certain conditions within the scope of ultrasonic treatment sludge reaction system.These parameters include ultrasonic time and power influencing on sludge dewatering and the COD,NH4+-N and total nitrogen of supernatant,the optimum reaction conditions.All of these are aim to provide benefits for the following denitrification reaction.It was found that in the 2# reactor,COD concentration in the supernatant fluid is 1518 mg/L,NH4+-N is 28.4 mg/L,total nitrogen is 71.8 mg/L,as the best results of reaction under the conditions of 40 min ultrasonic duration and 240 w power.Under these optimum conditions,the moisture content of sludge also has an obvious downward trend felling from 92.4% to 82.34% at the beginning,and the sludge volume appears to a greatly reduction.The sludge treated with ultrasonic pocessing were characterized by using three-dimensional fluorescence analysis and SEM.Its surface structure and compositon changes make a thorough understanding of the principle of the reaction.In order to analyze the supernatant reflux influence on biological denitrification,the mechanism of the various factors should be clarified at first.The effect of supernatant reflux ratio and the other various factors on nitrogen removal is considered with the conditions unchanged.The results show that the best denitrification effect comes under the conditions of 8h HRT and 7% supernatant reflux ratio which the COD removal rate is 86.11%,NH4+-N is 89.71%,total nitrogen is 82.92% and the COD concentration of effluent is 44.11 mg/L.Ultrasound is a physical method to reduce the moisture content in the process of sludge dewatering so that it can facilitate the subsequent disposal.In the meantime supernatant fluid used for denitrification can reduce the concentration of organic matter in the water and provide carbon source for denitrification as well.It provides a practical guidance for the development of the technology. |
