As sludge is still liquid and flowing after thickening or digestion, it is still too large to be transported and disposed of. In order to further reduce the water content and make the sludge as low as possible, it is necessary to dewater the sludge to reduce its volume and facilitate transportation [2] .
Background editorial Podcast
Sludge is an inevitable product of sewage treatment plants as well as sewage stations. Sludge that has not been well treated and disposed of will directly bring secondary pollution to water bodies and the atmosphere when it enters the environment, and will pose a serious threat to the ecological environment and human activities. Therefore, sludge is treated with great care. Sludge can be divided into two types of treatment, sludge dewatering process and sludge drying process, and the following mainly describes the respective advantages of different types of sludge dewatering machines [1].
There are three broad types of sludge in wastewater treatment plants: physical sludge, biochemical sludge and mixed physical and biochemical sludge.
Each type of sludge is somewhat different in its adaptation to the dewatering machine. The common models of domestic sludge dewatering machines are: centrifugal, filter belt, spiral ring ultimatum and plate and frame. For the dewatering of precipitated sludge, the choice of flocculant and its proportioning operation are crucial, as a good flocculation effect will result in a relatively smooth dewatering of the sludge. The following is a brief description of the actual use of the three models for selection.
Centrifugal type: all three types of sludge can be adapted, but high energy consumption and high rotational speed lead to high noise levels.
Filter belt type: Adaptable to physical and chemical sludge, with low cake moisture content, poor adaptability to mixed sludge and biochemical sludge, high backflow sludge, high water consumption for backwashing, high energy consumption and complex maintenance.
Spiral ring ultimatum type: the first generation of dewatering machine represented by the Japanese prototype has been promoted and used in China for 3-4 years, the disadvantage is that the output is low.
Technical principle edit Podcast
New separation technology: The organic combination of spiral pressure and dynamic and static ring forms a new separation technology with the integration of concentration and dewatering, adding an advanced dewatering mode option to the field of environmental protection sewage treatment in China.
Energy saving and water saving: As the continuous motion of the static and dynamic rings can achieve the effect of self-cleaning in the cylinder, the filter gap is not easily blocked, replacing the high-pressure flushing of the old generation of filter cloth and belt filter plate, greatly saving industrial water (13,000 tons/year of water saving in a single machine). The main spiral shaft runs at low speed (3-5 rpm) low speed reduces the mechanical wear and tear of the equipment and extends the service life of the equipment. Electricity consumption of the main machine ≦1.1kw/hr, the electricity saving of the single machine reaches 50,000 degrees/year.
Doubling the processing capacity: the processing capacity of the second generation dewatering machine has doubled compared to the first generation dewatering machine. One 303 unit can solve the sludge volume generated by 10,000 tons of sewage (120-150 tons) and can be matched with a process designed for deep dewatering of sludge to 50-40%, a single set of process can solve the sewage treatment volume of 1-30,000 tons.
The first of its kind in China: The regulating plate is automatically adjusted by elasticity, which naturally balances the internal pressure of the sludge in the dewatering section and more effectively ensures the service life of the static and dynamic ring.
Green environmental protection: the whole machine is sealed for operation and can be directly observed, the shell is easy to disassemble and install, no sewage leakage, no secondary pollution, noise ≦ 45 decibels, making the sludge machine room a beautiful environment and civilized production.
No filter cloth filter holes and other clogging original parts in the ring type sludge dewatering machine: safe and simple operation, according to the customer’s operating time period. Combined with the automatic control system, it can be programmed to achieve automatic unattended operation (should have a considerable amount of sludge).
Working principle edit Podcast
1、Plate-and-frame sludge dewatering machine: In an airtight state, the sludge pumped in by a high-pressure pump is squeezed through the plate and frame, so that the water in filter press for sludge dewatering the sludge is discharged through the filter cloth to achieve the purpose of dewatering.
2、Belt type sludge dewatering machine: The upper and lower two tensioned filter belts carry the sludge layer and pass through a series of regularly arranged rollers in an S-shape, relying on the tension of the filter belts themselves to form the pressing and shearing force on the sludge layer, squeezing out the capillary water in the sludge layer, thus realising sludge dewatering.
3、Centrifugal sludge dewatering machine: consists of reprint and screw conveyor with hollow shaft, sludge is fed into the drum by the hollow shaft, and under the centrifugal force generated by high speed rotation, the output is thrown into the drum cavity. Due to the different specific gravity, a solid-liquid separation is formed. The sludge is conveyed to the cone end of the drum by the screw conveyor and discharged continuously from the outlet; the liquid in the liquid ring layer is discharged by gravity outside the drum by continuous “overflow” from the weir.
4、Stacking sludge dewatering machine: The main body of the filter is formed by the fixed ring and the moving ring superimposed on each other in layers, with the spiral shaft running through it. The filtrate is discharged from the slit formed by the fixed ring and the moving ring, and the cake is discharged from the end of the dewatering section.
Workflow Editor Podcast
1, The sludge in the sludge tank is conveyed to the metering tank through the sludge transfer pump, the amount of incoming sludge is adjusted by adjusting the level adjustment tube in the metering tank and the excess sludge is returned to the sludge tank through the return flow tube.
- The sludge and flocculant are mixed in the flocculation mixing tank by a mixer to form an alum bloom, the ideal diameter of which is around 5 mm.
- The alum bloom is concentrated by gravity in the thickening section and a large amount of filtrate is discharged through the slits in the thickening section.
4、The thickened sludge continues to advance in the direction of the spiral shaft rotation and is fully dewatered by the internal pressure formed by the back pressure plate. - The dewatered sludge cake is discharged through the gap formed by the back pressure plate and the spiral body. The sludge throughput and the water content of the cake can be adjusted by adjusting the rotation speed of the spiral shaft and the gap in the back pressure plate.
Selection Editor Podcast
A large amount of sludge will be produced after sewage sedimentation treatment, even after thickening and digestion, the water content is still as high as 96 %, which is very large and difficult to dispose of by consumption, and must be treated by dewatering to increase the solids content of the sludge cake in order to reduce the footprint of the sludge pile.
Mechanical dewatering is generally used in large and medium-sized sewage treatment plants. There are many types of dewatering machines, which can be divided into three categories: vacuum filter dewatering, press filter dewatering and centrifugal dewatering according to the dewatering principle. On the domestic sewage treatment plant often choose the filter press (including belt filter press and plate and frame filter press) and centrifugal dewatering machine working principle, equipment selection need to focus on the issues and maintenance and operating costs, etc. to make an introduction.
1, the belt filter press is less affected by the fluctuation of sludge load, and also has the characteristics of low water content of the mud and stable work, less start-up consumption, relatively simple management and control, and not high requirements for the quality of the operating personnel. At the same time, due to the early entry of the belt filter press dewatering machine into the country, a considerable number of manufacturers can produce this equipment. In the sewage treatment project construction decision, you can choose the belt filter press to reduce the project investment. Most of the new domestic sewage treatment plants use the belt filter press dewatering machine, for example, Beijing Gaobeidian sewage treatment plant a project five dewatering machines are all belt filter press dewatering machine, filter belt, roller press cylinder put into operation since the situation is good, so in the second phase of equipment selection is still the choice of this model.
2,Generally, the plate and frame filter press has the highest solids rate of 35% compared to other types of dewatering machines. The movement of the filter plate. It is required to be fully automatic or semi-automatic by means of a hydraulic and pneumatic device, which is not easy to operate, and a filter cloth oscillation device, so that the filter cake can be easily dislodged. Compared with other types of dewatering machines, the biggest disadvantage of the plate and frame filter press is the large footprint. Take the belt filter press used in Beijing Gaobeidian sewage treatment plant a project and the plate and frame filter press used in Anshan industrial sewage treatment plant as an example for comparison: Gaobeidian sewage treatment plant treats sewage volume of 500,000t/d, sludge output of 1852.5m3/d, dry matter of 92.63t/d, using five German KLEIN-KS30 belt filter presses. The base area of each filter press is only 27503500mm, while the volume of water treated in the Anshan sewage treatment plant is 22t/d and the dry matter is 275t/d, six plate and frame filter presses are used and the base area of each filter press is 240012000mm, meanwhile, due to the intermittent operation of the plate and frame filter presses, the efficiency is low and the environment in the operation room is poor and there is secondary pollution. It is rarely used in domestic large sewage treatment plants.
Use Editor Podcast
Sludge dewatering machine has the advantages of small volume, good effect, low energy consumption, less noise, no vibration, higher automation, easy centralized management and convenient maintenance [3] . It is mainly used for.
- industrial wastewater coagulation and sedimentation sludge
- industrial wastewater excess activated sludge
- urban sewage treatment surplus sludge
- sludge from community sewage treatment
- Water purification field dosing and coagulation sludge
- Surplus sludge from water and fertilizer treatment
- Solid-liquid separation in plant manufacturing processes
Analysis of mesh belt run-off Editorial Podcast
Sludge dewatering machine is a continuous operation of sludge treatment equipment, because of the low water content of the mud out of the work stable operation, with small energy consumption, control and management is relatively simple, easy maintenance and other characteristics in the industry, mining, sewage treatment industry has been widely used. The following is a description of a common problem and solution for sludge dewatering machine in the process of use. Belt dewatering machine in the production operation, affect the mesh belt uniform force factors more, easy to appear mesh belt run off the fold phenomenon and once the mesh belt crease, the crease and sludge scraper frequent friction, easy to appear excessive wear and tear, resulting in mesh belt life greatly shortened for enterprises to bring greater economic losses.
Operation management principles editorial broadcast
1, sludge dewatering machine processing capacity control within the appropriate range, combined with the sludge flow, flocculant flow and differential degree of regulation, to avoid a sudden increase in load caused by equipment overload so that the system fluctuates frequently and affects the processing effect, but at the same time can achieve greater equipment processing efficiency.
2, sludge concentration changes to adjust the flocculant flow and differential speed in a timely manner, both to ensure the treatment effect and to avoid waste; sludge flow increases or sludge concentration increases, the flocculant flow tracking increases, the differential speed increases accordingly; sludge flow decreases or sludge concentration decreases, the flocculant flow tracking decreases, the differential speed decreases accordingly.
3, there is no best flocculant, only the most suitable, flocculant type and consumption depends on both the quality of the agent and the nature of the sludge match, but also depends on the type of equipment structure and operating conditions match, only the three to get the best combination of operation, in order to achieve the lowest flocculant consumption, the best treatment effect and the highest processing efficiency. - Mud biscuit performance should be combined with torque data to determine the optimum range of differential speed values. In principle, a lower differential speed should be used as far as possible to achieve better treatment results and save flocculant consumption without causing clogging of the centrifuge and to meet the treatment capacity.
5, all the site management and operators have to do is: constant observation, timely adjustment and good summary, as far as possible in the various changes that may occur in the search for the best, relatively stable and perfect match of all working parameters. Generally speaking, this observation and adjustment should be carried out once in 1 to 2 hours, to strictly avoid the situation that the operating parameters of the equipment will persist for a long time or a shift without any adjustment after the machine has been turned on, and the laziness or lack of responsibility of the operators on site is one of the main reasons for the long-term inefficiency of the sludge dewatering workshop, the fluctuation of the processing effect and the waste of the chemical consumption.
6, often test the dewatering effect of the dewatering machine, if the separation liquid (or filtrate) is found to be turbid, the solids back to the first rate of decline, should promptly analyze the causes, to take measures to address.
7、Often observe the effect of sludge dewatering, if the solid content of mud cake decreases, the situation should be analysed and targeted measures should be taken to solve the problem.
8、Observe the operation of the sludge dewatering device frequently, and take corrective measures to ensure normal operation in response to abnormal phenomena.
9、Every day, ensure that the dewatering machine has enough flushing time, and when the dewatering machine listens to the machine, the inside and circumference of the machine are flushed cleanly and thoroughly to ensure cleanliness and reduce the bad smell. Otherwise it is very difficult to flush after the accumulated mud has dried.
10、In accordance with the requirements of the dewatering machine, frequently do observation and machine inspection and maintenance.
11、Frequently pay attention to check the easy wear and tear of the dewatering machine and replace it when necessary.
12、Discover the damage to the filter belt by the sand particles in the mud in the dewatering machine in time, and replace it in time when the damage is serious.
13、Make good records of analysis and measurement [1].