CN100363276C - A kind of sludge ultrasonic dehydration method - Google Patents

Abstract

The present invention relates to a supersonic wave dewatering method for sludge, which belongs to the technical field of solid waste treatment. In the method, sludge 1 dewatered in a sewage treatment plant is first pressed into cakes by a stirring appliance 2 and a tabletting appliance 3; the sludge is loaded into supersonic wave treating devices 5 arranged at the upper end and the lower end of a conveying belt 4 by the conveying belt 4; the sludge is treated by supersonic waves of certain frequency and power, which are generated by the supersonic wave treating devices 5; the sludge treated by the supersonic waves are further dewatered by a dewatering appliance 6, and water 7 obtained through dewatering is drained into a sewage treatment plant 8; and the dewatered sludge is changed into resources 9 at a later stage. In the dewatering method, the water content is dropped from the original range of 80 to 85% to the range of 60 to 70% after the sludge is treated by the supersonic waves, which lays a good foundation for changing the sludge into resources at a later stage. In addition, a used supersonic wave generator and other supporting facilities are mechanical appliances with low power and little consumed energy; compared with other dewatering technologies, both the cost and the energy consumption of the method are greatly reduced. Consequently, the method has a preferable market prospect.

Description

A kind of sludge ultrasonic dehydration method

technical field

The invention relates to a method for modifying and dehydrating the sludge of a sewage treatment plant by using the ultrasonic principle, and belongs to the technical field of solid waste treatment.

Background technique

With the increasingly severe environmental protection problems, more and more cities have built urban sewage treatment plants to treat domestic sewage, thus producing a by-product - sludge. Sludge is composed of organic debris, bacterial cells, colloids, various microorganisms, and organic and inorganic particles. It contains 90% to 99% of water and 1% to 10% of solid content. At present, the discharge of urban sludge in my country has reached tens of millions of tons, and it is increasing at a rate of 10% every year, which has brought enormous pressure to the environment. The sludge production in foreign countries is also very large. For example, the annual output of sludge produced by sewage treatment in the UK is 1.107 million tons of dry solids, and the per capita dry solids of sludge produced per day is 62g. Since the sludge contains a large amount of perishable substances, and also contains nutrients such as nitrogen and phosphorus and heavy metals such as cadmium, copper and mercury, it must be properly disposed of, otherwise it will bring serious pollution to the environment.

Municipal sludge contains organic matter, nutrients such as nitrogen, phosphorus, and potassium, and heavy metals such as Ni, Pb, Cr, Cu, and Zn. Organic matter is easy to rot without stabilization treatment, and nutrients and heavy metals will also cause secondary pollution to the environment. Facing the difficult problem of sludge treatment and disposal, the Chinese government attaches great importance to it, and successively formulated the "Standards for the Control of Pollutants in Agricultural Sludge" (GB4284-84), the "Standards for Discharge of Pollutants from Urban Sewage Treatment Plants" (GB18918-2002), "Urban Sewage Treatment Plant Sewage Sludge Discharge Standard" (CJ3025-93) and "Urban Sewage Treatment and Pollution Prevention Technical Policy" put forward strict requirements for sludge treatment and disposal.

Currently commonly used treatment methods mainly include gravity settling, conditioning and mechanical dehydration. Gravity settling can increase the weight ratio of solid content in sludge from 2% to 5%. It is usually adjusted by anaerobic, aerobic, lime, heating and cold solution methods. The process is complicated and the cost is high. Some sewage treatment plants Not adopted. Mechanical dehydration is a must for sewage treatment plants. Common methods include ordinary filtration, pressure filtration, vacuum filtration, and centrifugation. Mechanical dehydration is limited by the structure of the sludge itself, and the dehydration effect is very limited. In addition, Shanghai Shidongkou Urban Wastewater Treatment Plant adopts sludge drying and incineration project, and adopts thermal method to dry and dehydrate sludge, which requires a lot of heat, so the cost is very expensive.

Contents of the invention

The problem to be solved by the present invention is to propose a method that utilizes the mechanical and cavitation effects of the ultrasonic wave itself to destroy the structure of bacterial micelles in the sludge and remove the moisture contained in it, aiming at the shortcomings of the above-mentioned existing sludge dewatering technology. Achieve good sludge dewatering effect.

A kind of sludge ultrasonic dehydration method proposed by the present invention is characterized in that: the method is that the sludge (1) after the dehydration treatment in the sewage treatment plant is first pressed into The cake is sent to the ultrasonic treatment device (5) located at the upper and lower ends of the conveyor belt through the conveyor belt (4). The ultrasonic treatment device (5) generates ultrasonic waves of a certain frequency and power to treat the sludge. The sludge after ultrasonic treatment is dehydrated. The equipment (6) is further dehydrated, and the dehydrated water (7) is discharged back into the sewage treatment plant (8), and the dehydrated sludge enters the later stage of resource utilization (9).

In the above sludge ultrasonic dehydration method, the ultrasonic frequency of the ultrasonic treatment device (5) is 20, 33, 40, 50KHz, and the ultrasonic sound energy density is controlled at 0.1-2.0w/g.

In the above method for ultrasonic dewatering of sludge, it is characterized in that: the processing time of the ultrasonic treatment device (5) is within 4-10 minutes.

In the above sludge ultrasonic dehydration method, it is characterized in that: the thickness of the mud cake is controlled within 20cm.

The invention is characterized in that the ultrasonic wave has good dehydration treatment effect on sewage plant sludge, and has low price and low energy consumption. First of all, ultrasonic technology has been widely used in my country's shipbuilding, metallurgy and machinery departments, and has a good industrial foundation. Many domestic manufacturers have production capacity and can reach the international advanced level, which provides good conditions for cost reduction and application. . Secondly, compared with the existing sludge dewatering technology, the present invention has very low energy consumption, which is 1/5 or even 1/8 of the heat treatment energy consumption, which is more in line with the characteristics of energy saving and environmental protection, and is more cost-effective from an economic point of view.

Description of drawings

Fig. 1 is a schematic process flow diagram of the ultrasonic sludge dewatering technology of the present invention.

Detailed ways

Below in conjunction with accompanying drawing, technical scheme of the present invention is described further:

1-sludge, 2-mixing equipment, 3-tabletting equipment, 4-conveyor belt, 5-ultrasonic treatment device, 6-dehydration equipment, 7-remove water, 8-sewage treatment plant, 9-post-recycling , 10 - Ultrasonic.

The specific process of the present invention is: the sludge 1 after the dehydration treatment of the sewage treatment plant first passes through the stirring equipment 2 and the tableting equipment 3, and the sludge is pressed into a cake shape with a certain thickness, and is sent to the conveyor belt 4 through the conveyor belt. The ultrasonic treatment device 5 at the upper and lower ends, the ultrasonic treatment device 5 generates ultrasonic waves of a certain frequency and power to treat the sludge, the sludge after ultrasonic treatment is further dehydrated by the dehydration equipment 6, and the dehydrated water 7 will be discharged back into the sewage treatment plant 8 , the dehydrated sludge enters the later stage of resource utilization9. The moisture content of dehydrated sludge can reach 60-70%, which lays a good foundation for later resource utilization, such as composting, fuel rods and brick making industries.

The technical principle of the present invention is as follows: the dehydrated sludge of the sewage treatment plant is stirred and cake-pressed, and then sent to the ultrasonic treatment device, and the ultrasonic generators located at the upper and lower ends generate ultrasonic waves of a certain frequency and power, which are used in the sludge. After a certain treatment time to achieve the best dehydration efficiency, the dehydrated sludge will be automatically transferred to the filter press equipment outside the ultrasonic treatment device to remove the water generated after ultrasonic treatment. The moisture produced in this process will be discharged into the sewage treatment plant, and the remaining sludge components can be used for later resource utilization due to the good dehydration effect, such as composting, fuel rods and brick making industries.

In the present invention, several key parameters need to be selected, namely: processing time, mud cake thickness, ultrasonic frequency, ultrasonic power. The frequency and power control of ultrasonic waves is the key point of this technology. Too weak ultrasonic waves have no effect on sludge, while too strong ultrasonic waves will destroy the structure of bacteria inside the sludge, which is not conducive to the recycling of sludge in the later stage. In the present invention, the selected ultrasonic frequency is 20, 33, 40, 50KHz, the ultrasonic sound energy density is controlled at 0.1-2.0w/g, the ultrasonic treatment time is within 4-10 minutes, and the mud cake thickness is controlled within 20cm. The invention can dehydrate the sludge with a water content of 80% to 60-70%, thus laying a good foundation for subsequent resource utilization. Due to the different components of sewage in different places and the differences in the processes adopted by sewage plants, these parameters will also change accordingly. Therefore, under the premise of not violating the essence of the present invention and the scope of the appended claims, in the specific implementation process, Some appropriate changes can be made to the selection of key parameters in the present invention.

The test results show that ultrasonic has a good effect on sludge dewatering. The aforementioned and other objects, features and positive effects of the present invention will become more apparent from the detailed description of the preferred embodiments in conjunction with the accompanying drawings.

Example 1

An urban sewage treatment plant in Qinhuangdao adopts the activated sludge method for treatment, and the properties of the dewatered sludge are shown in Table 2:

Table 2 Sludge properties and components before treatment

  Moisture content (%) Volatile content (%)   Ash content (%) Fixed carbon (%)   Lower calorific value (kcal/g) 84.20 40.95 56.66 2.39 457

The moisture content of the treated sludge is shown in Table 3:

Table 3 Water content of sludge after ultrasonic treatment

serial number time (min) Ultrasonic frequency (KHz)   Sound energy density (w/g) Temperature after reaction (°C) Sludge thickness (cm) Moisture content (%) 1 0 0 0 20 10 84.2 2 4 40 0.8 twenty two 10 63.3 3 6 40 0.8 30 10 64.8 4 8 40 0.8 33 10 64.4

Example 2

An urban sewage treatment plant in Nanshan District, Shenzhen, adopts the oxidation ditch process to treat sewage. The properties of dewatered sludge are shown in Table 4:

Table 4 Sludge moisture content and components before ultrasonic treatment

  Moisture content (%) Volatile content (%)   Ash content (%) Fixed carbon (%)   Lower calorific value (kcal/g) 82.70 42.32 55.64 2.04 463

The moisture content of the treated sludge is shown in Table 5:

Table 5 Statistical table of moisture content of sludge after ultrasonic treatment

serial number time (min)  Ultrasonic Frequency(KHz) Sound energy density (w/g) Temperature after reaction (°C) Sludge thickness (cm)   Moisture content (%) 1 0 0 0 20 20 82.7 2 4 50 1.6 25 20 60.1 3 6 50 1.6 34 20 62.2 4 8 50 1.6 40 20 63.0

From the above examples, it can be concluded that after the sludge is treated with ultrasonic waves, the water content drops from 80-85% to 60-70%, which lays a good foundation for the later recycling of sludge. The energy consumption of the present invention mainly comes from the energy consumption of the ultrasonic generator and other supporting facilities, all of which are mechanical equipment with low power and low energy consumption. Compared with other dehydration technologies, the cost and energy consumption will be greatly reduced, so there is a comparative advantage. Good market prospect.

Claims (1)

1. A sludge ultrasonic dehydration method, characterized in that: the method is to press the sludge (1) from a sewage treatment plant into a cake through a stirring device (2) and a tableting device (3) after dehydration treatment , sent through the conveyor belt (4) to the ultrasonic treatment device (5) located at the upper and lower ends of the conveyor belt, the ultrasonic treatment device (5) generates ultrasonic waves of a certain frequency and power to treat the sludge, and the sludge after ultrasonic treatment passes through the dehydration equipment ( 6) Further dehydration, the dehydrated water (7) is discharged back into the sewage treatment plant (8), and the dehydrated sludge enters the later stage of resource utilization (9); the ultrasonic frequency of the ultrasonic treatment device (5) is 20, 33, 40, 50KHz, the ultrasonic sound energy density is controlled at 0.1-2.0w/g; the processing time of the ultrasonic treatment device (5) is within 4-10 minutes; the thickness of the mud cake is controlled within 20cm.

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