What is a rotary drum screen filter?
A rotary drum filter, also known as a rotary drum screen or rotary sifter, is equipment commonly used in municipal and industrial water treatment processes. It is typically employed as the second pre-treatment process in wastewater treatment plants, following screening. The rotary drum filter is usually positioned upstream of the system, at the outlet of the pumping station responsible for collecting wastewater.
In addition to its primary function of fine particle separation, the rotary drum filter can also effectively remove mechanically coarse debris such as trash rack debris (RAG), thick sands, and grease. This prevents these wastes from mixing with mud and interfering with downstream processes.
The Rotating Drum Screen is an internally fed rotary drum screen designed for heavy water/wastewater pretreatment applications, including draining, mud thickening, and treating sandy or industrial wastewater. It is especially well-suited for use in membrane bioreactor (MBR) treatment plants.
This rotary drum screen offers an outstanding solution for the removal of small particles. Its exceptional removal efficiency perfectly caters to the requirements of Membrane Biological Reactor (MBR) designs.
How does a rotary drum screen work？
The rotary drum screen operates by sorting various fine and coarse materials. The water initially enters a container and is then poured onto a circular drum screen. The raw water, along with any debris present, passes through the drum screen due to gravity, allowing for sifting.
As the drum rotates slowly, the debris becomes trapped on the surface of the trommel screen. This prevents any accumulation or clogging of the sifter screen. To remove this waste, an outer scraper mounted on a spring system scrapes it off the surface of the screen.
All collected waste falls into a hopper, garbage can, or dumpster and will be discharged outside at a later time. Finally, after being scraped clean, the trommel screen undergoes cleaning using high or medium-pressure water jets.
How to design a rotary drum screen?
Designing a rotary drum screen involves several important steps.
Here is a guide to help you design an effective and efficient rotary drum screen:
1. Determine the specific application: Start by understanding the specific purpose of the rotary drum screen. Consider factors such as flow rate, type of material to be screened, particle size distribution, and required separation efficiency.
3. Select the appropriate sieve or filter type: Based on the application requirements, choose the most suitable sieve or filter for your rotary drum screen. Options include perforated metal plates, wedge wire screens, and trommel screens. Consider factors like durability, ease of maintenance, and compatibility with the material being screened.
3. Calculate dimensions: Calculate the diameter and length of the rotary drum based on factors like desired throughput capacity and residence time needed for effective screening. Ensure that these dimensions are practical for installation in your facility.
4. Determine rotational speed: The rotational speed of the drum affects screening efficiency and performance. It should be optimized to achieve proper agitation without causing excessive wear or clogging issues.
5. Design internal components: Design internal components such as paddles or lifters inside the drum to ensure efficient movement of solids along with adequate exposure to sieves or filters.
6. Design inlet/outlet arrangements: Plan appropriate inlet/outlet arrangements considering factors like flow dynamics, avoidance of dead zones where material can accumulate, ease of maintenance access points, and prevention of bypassing particles during operation.
7. Provide necessary support structure: Adequate support structure must be designed to withstand mechanical stresses due to rotation, making sure it provides stability while allowing easy access for maintenance activities.
8. Include safety features: Integrate safety features into your design, such as emergency stop buttons, guards, and sensors, to prevent accidents during operation. These should comply with relevant safety standards and regulations
9. Consider automation options: Explore possibilities for automating various functions, such as monitoring system status, cleaning mechanisms, differential pressure control, and alarm systems. This can enhance overall efficiency and reduce manual intervention.
10. Perform simulations or prototypes: Before finalizing the design, it’s advisable to perform simulations or build a prototype to validate its performance. This will help identify any potential design flaws and make necessary adjustments before production.
Remember to consult with experts in the field of rotary drum screen design for additional guidance and ensure compliance with local regulations and standards.
Focus: The rotary drum screen for wastewater treatment
The rotary drum screen is ideal for specialized applications that require fine screening, such as wastewater treatment. It serves as the first step in pre-treatment before primary treatment or flotation processes. Screening wastewater treatment plant effluent is of utmost importance for several reasons.
Firstly, it enables the removal of a certain amount of debris, preventing large waste from entering the mud. This helps maintain a cleaner and more efficient system overall. Additionally, it acts as a protective measure for downstream processes within the entire wastewater treatment plant.
Furthermore, by utilizing a drum screen, issues like pump clogging and excessive crusting on primary clarifiers are significantly reduced. This makes it an essential step in ensuring smooth operations throughout the facility, particularly if subsequent processes involve filtration mechanisms.
Benefits of Rotary Drum Screens
Compactness: Rotary drum screens have a small footprint, making them ideal for installations with limited space.
Low maintenance: These screens require minimal maintenance. Regular checks to ensure proper functioning, cleaning of the drum screen, and greasing of bearings are all that is needed.
Easy operation: Rotary drum screens operate automatically through their self-cleaning system. They start working when the pumps in the elevation station are activated.
Screening capability: A rotary drum screen enables effective solid/liquid separation. The finer the mesh used, the better the separation achieved. It also allows for a separate collection of rejects from screenings, preventing them from ending up in mud or other downstream processes.
Securing downstream processes: By removing the coarse waste at the beginning of treatment processes, rotary drum screens prevent various issues such as pump clogging, solenoid valve lockouts, and sand build-up in basins.
Wastewater pretreatment: Rotary drum screens are commonly used for municipal and industrial wastewater treatment before further processing.
Solid/liquid separation: Industries like paper mills, textile (dyeing & bleaching), and chemical/pharmaceuticals rely on these screens to separate solids from liquid effluents effectively.
Food industry applications: From meat processing factories and slaughterhouses to dairies and fast-food establishments, rotary drum screens aid in solid/liquid separation required for efficient wastewater management.
Viticultural & vinicultural effluents/Fish industry/Potato processing/Canning factories/Animal feeding – All these industries benefit from using rotary drum screens for solid-liquid separation purposes during their respective production processes.