New Generation Auger Press Sludge Dewatering Systems
Compiled by: Dr. Ins. Load. Eng. Mete Gerçek email@example.com
March 17, 2017 | TECHNICAL ARTICLE Journal of Water and Environment Issue 104 (March 2017)
Auger Press equipment provides different advantages to the operators as well as the economy provided in operating costs, durability and thus, efficient operation for many years without any problems. In the sense of auger press, the “Auger Press” machines, which were developed for the first time in Japan in 1985 and accepted all over the world as a new sludge dewatering technology, had the opportunity to get acquainted for the first time in Europe 20-25 years ago, during various fairs, especially IFAT. .
Used in the dewatering of domestic and industrial wastewater treatment sludge, previously preferred bag filter presses, later belt filter presses, and in recent years auger presses and decanters are the main sludge dewatering equipment.
Especially in industrial wastewater treatment plants, sludge dewatering gains more importance according to the characteristics of wastewater and treatment process. In such cases, the most suitable sludge dewatering equipment should be carefully selected according to the results of laboratory tests to be performed on the sludge samples taken. In the selection of equipment, of course, the daily amount of sludge to be dewatered, especially the hourly sludge amount (m3/hour) and hourly solid matter amount (kg.KM /hour) gain importance. As in other sludge dewatering systems, the most important issue in Screw Press systems is the conditioning of sludge particles with polyelectrolyte chemicals and thus the formation of solid clots by combining and integrating sludge particles with each other. The water released between the clots comes out of the dewatering equipment as filtrate, and the remaining clots combine with each other to form solid structures that will not break apart, which is the desired goal, to form a sludge cake.
About Auger Press Systems...
There are quite a few different screw sludge dewatering systems. In this study, at least 3, and even a total of 4 different systems were examined.
Each system has a helix system, namely auger (Archimedes screw, auger). The most important necessary condition is “Creation of solid clots by conditioning the sludge entering the equipment with polyelectrolyte (it is very important to choose the most suitable polyelectrolyte material for this) and transportation of the sludge particles that have started to coagulate without fragmentation”, that is, the mud inlet, which is the main element of the equipment, which enables this transportation process to take place. There is a horizontal or inclined Archimedean screw (auger) carrier system that carries the mud cake up to the exit part after the sludge section. The most important features that distinguish these screwed sludge dewatering systems from each other are the main body position, which is manufactured at a certain angle with the horizontal; on the other hand, some other systems come with horizontal auger presses. In addition to this, another feature is the inner surfaces of a fixed-position cylindrical filter and the fixed bar gaps (if we consider them as circles next to each other), the water spraying device, which must operate at certain time intervals as the auger rotates with the brush and the clean drinking water pressure of about 6 ATU. or, in more advanced technologies, different discs can pass through each other and clean the disc spaces by themselves without the need for brushes and pressurized water can be given as an example. The movement of the movable disks between the hard disks is provided by the rotational movement of the auger archimedes screw.
In addition, there are Screw Presses, which are completely horizontal and form the cylindrical structure with a three-dimensional filter membrane instead of circles. The old type inclined auger, which has been used in some facilities since 1993, albeit very limitedly, has been used in a very limited amount of cleaning water such as 200-300 ltr/hour and a maximum of 2-3 ATU pressure in the disc system where the filter surfaces consist of fixed and movable discs. Potable water is used to clean the filter pore spaces in a very high amount (and at very frequent time intervals) such as 5-8 m3/hour in horizontal position auger presses with fixed rods and a membrane filter system; otherwise the system will not work. The potable water to be supplied for cleaning fixed-position filter surfaces should contain particles less than 200-250 microns; otherwise the water spray nozzles will be clogged. In order to ensure that the permeate water (filtrate) is drawn out of the helix, it is essential that the filter surfaces remain clean at all times. In this way, cleaning water with a pressure of at least 5 ATU or even 6 ATU (as long as the machine is dewatering) is used continuously to ensure that the filtrate permeate water drain is open.
Existing dewatering equipment, which is working especially in small and medium-sized wastewater treatment plants in many countries, has been replaced with more economical Screw Presses, especially due to the high operating costs. Especially, new generation disc sludge auger press dewatering equipment is preferred more and more in wastewater treatment plants.
The low operating and maintenance expenses of the Auger Press compared to other alternatives, the absence of fast moving elements in the new generation disc auger presses, the wear problems of the Auger Press are due to the fact that the rotational speed per minute of the helix, which is the only rotating element in the cylindrically-conical fixed filter, is only a few rpm in domestic applications. . Due to the extremely low rotational speed, the wear and tear is reduced, and the need for spare parts is negligible.
Robust structure of auger presses, only 1-3 rpm in some auger presses, 5-12 rpm internal spiral rotation speed, 1.1-3.0-4.0 kW installed powerful direct drive single motor, quiet and vibration-free, relatively less polyelectrolyte need, continuous automatic operation and very advanced electronic control system and technological manufacturing are only possible thanks to a simple structure. All these features and advantages have made the Screw Presses, especially the new generation disc auger presses, superior in small and medium-sized domestic and industrial wastewater treatment plants.
Changes in the solid matter in the sludge inlet and the sludge character changing from time to time cause wear in other dewatering equipment, replacement of worn parts more frequently and the use of spare parts more quickly. As a result, it needs frequent cleaning and more staff attention. For these reasons, unforeseen additional costs arise and as a result, operating costs increase considerably.
The auger press equipment works fully automatically with the PLS system and the system controls itself. The preference of auger press dewatering equipment, especially in small and medium-sized wastewater treatment plants, is not only due to the sludge cake with high solids content, but also that these equipments have been successfully applied all over the world for the last 25 years, and they are as good as the first day with an excellent efficiency without any problems. It also depends on factors such as working, robust, requiring very little human attention, economical operation, and need for very few spare parts. The fact that higher solids content can be reached has also made it possible to obtain sludge cakes that reach 27, 30 or even 45 percent DM contents of sludge obtained from fibrous sludge structures, for example, paper industry, leather industry, fibrous textile industry wastewater. It can work even under a porch outside without requiring a closed space-special building, it is a compact package system that takes up very little space, it is completely made of 304L, 316L or 321 stainless steel, so there is no wear problem, very few spare parts and maintenance are sufficient, automatically With its self-washing cleaning system and the advantage of using very little water, the new generation disc mud auger presses use only one engine (1-4 kW and 1-12 rpm), silent and vibration-free operation, especially thanks to its inclined structure, the pressed mud cake can be directly ( It differs from other processes in that it is automatically poured into a garbage container or storage tank or trailer in a closed environment without emitting odor.
In this process, the sludge is collected from the sludge storage tank, sludge thickener or directly from the digestion tank, etc. It is taken from the source, briefly from the sludge tank, and is pumped to the pipeline where the flocculation tank, which is the first unit of the auger press, is connected with the help of an eccentric screw pump mud pump in order not to spoil the formed sludge clots. A static mixer (mixer, mixing injection unit) located on this pipeline mixes the polyelectrolyte solution and wet sludge very well, which is pressed by a dosing pump from the coagulant preparation (3-chamber powder or liquid polyelectrolyte solution preparation) tank. With this static mixer, optimum contact between the thin sludge and the generally used powdered polyelectrolyte (0.01-0.05%) solution is ensured. In the flocculation tank (tube), the level of the coagulated sludge and permeate water (floc) formed by the polyelectrolyte solution + wet sludge mixture rises and is discharged into the dewatering machine. Thus, the pre-dewatering process is carried out. As a result of the contact of the pre-dewatered (coagulated) sludge with a cylindrical/conical filter network (15-20 microns) inside (fixed and inclined position) continuously, the permeate water filtered from the disc gaps in the rotational movement of the moving discs between the hard disks in the new generation auger presses. It is filtered out/down (and discharged) through this filter by the acceleration of gravity. The clots that will form the mud cake are transported to the upper level of the auger press machine by means of an Archimedean screw auger rotating in the cylindrical filter and stored directly in the container in the mud cake formation. As a result, the sludge cake, which is obtained completely automatically in a completely closed environment, is discharged directly into the storage container.
Before this type of auger press thickener and dewatering equipment was developed, the factors that play an important role in the sludge dewatering process are examined in detail below.
“Addition of appropriate and full dose of coagulant”, “Coagulation of sludge”, “Filtration surface area of sufficient size for filtering water”, “Stainless steel mesh (filter) intervals around the screw conveyor according to the degree of dewatering”, “Disc in new generation disc auger presses” intervals and rotational speed of the moving discs”, “Continuous contact of wet sludge with the filtration surface”, “Rotational speed and engine power of the carrier screw”, “Stainless steel type according to sludge character”, “Sludge dewatering time”.
In the old generation auger presses, it was necessary to ensure that the filter bar gaps were kept thoroughly clean by spraying water with at least 5 ATU pressurized water from the outside at frequent intervals. Otherwise, the cylindrical filter surface rod and pore spaces surrounding the permeate helix will be clogged, the permeate water cannot come out, and because the sludge from the auger will give the mud cake towards the exit point together with the permeate water, sludge has come out instead of mud cake formation. However, this disadvantage has been eliminated in the new generation disc type auger presses.
The new generation disc auger press sludge dewatering systems generally consist of a compression section in which sludge cake formation starts as the following: densification (pre-dewatering) and dewatering (with the gradual decrease of the spacing of the helix steps) formed by fixed and moving discs and a screw conveyor.
Advantages Provided to Operators
The advantages of the fully automatic auger press sludge dewaterers to the operators can be listed as follows.
1- The most suitable machine selection/combination can be made for any amount of sludge. Thanks to its superior manufacturing technology and standardized mass production, it can be delivered in a very short time with a low price. It is completely stainless steel, does not corrode and serves for many years without any problems. The manpower requirement is low. It works fully automatically and continuously (uninterruptedly).
2- A special filter material, any belt, plate, etc. not necessary. The filter is stainless steel. It consumes very little energy, has a very low speed and can also be used for dewatering sludge containing abrasive (sand, pumice stone, etc.) materials.
3- As it works in old type auger presses, it automatically cleans itself with 5-6 ATU pressurized water at certain time intervals and washes the filter. It is not necessary to clean the filter gaps with water in the new generation auger presses consisting of newly developed fixed and movable discs. In this way, significant water savings are achieved. Only when the machine stops, the disc spaces are cleaned with a very small amount of water with 2-3 ATU pressure.
4- It is compact and can be kept anywhere in the outdoor environment. No special equipment is required inside the building. Very little volume is sufficient (6-8 m2). Installation is simple and fast.
5- The amount of polyelectrolyte used is low and thus provides an additional economy. The sludge is constantly in contact with the filter surface, and the permeate water is easily separated from the sludge clots, increasing the dewatering efficiency. It is also important to follow the instructions for use, and to use original polyelectrolyte material that does not add any cheap salt or other additives in order for the auger press equipment to work without any problems and with a long lifespan. Because as it is known, stainless steel rusts.
6- The sludge cake that comes out is emptied directly into the container thanks to the inclined body.
7- It works silently. There is no vibration. There is little to no wear. Minimal maintenance is sufficient. There is no need for spare parts. Operating costs are low.
8- There are no hydraulic elements. Its process and working principle are simple, it works smoothly.
9- It is a completely closed system. It does not produce odor and polluting exhaust, provides a sanitary and clean operation.
The use of auger press sludge dewatering equipment in enterprises avoids the following disadvantages:
1- Prevents intermittent operation (such as intermittent operation in plate presses and other presses)
2- Due to the high amount of wear, there is no necessity to change the belt/plate filter layers and especially the centrifugal rotary filter, which is frequently seen in other equipment. Because the auger press machines are completely made of stainless steel. The necessity of replacing belts and plates requires additional expense as well as a waste of time (as in Belt and plate presses).
3- It does not require continuous manpower (manual) cleaning, it works fully automatically.
4- It does not require a special building, which increases the cost for the presses.
5- Removal (transport) of sludge cake requires additional cost and time. The auger press equipment stores the sludge cake directly into the container.
6- It is silent. Electricity consumption is high in centrifuges (abrasion is high because it is fast and cyclical). Screw press installed power (including pumps etc.) is about 5 kW.
7- There is no rust, the auger presses are made of completely stainless steel material, especially the parts in contact with the mud. It is a closed environment, odor, exhaust gas, etc. it does not emit odor, it is operated cleanly and without any problems.
8- There is no special problem in transportation, the auger press is both compact and robust.
9- It has been used successfully in many facilities for years.
10- Assembly control and commissioning (start-up) is carried out by the expert team.