Sludge dewatering is the process of removing water from sludge. After wastewater treatment, the remaining material usually has a high water content. This final step in the treatment process reclaims much of the liquid.
The sludge handling and disposal process is a major cost for wastewater facilities. Improvements to older methods as well as innovative alternatives are now available for treatment plants. Some of these options include:
Belt Filter Presses
This type of equipment has been around for many years and is still considered one of the industry standards. These systems are easy to operate and familiar to most facility staff but are not the best alternative for containing odors.
Centrifuges have been greatly improved over the long period of time that they have been used in the sludge dewatering process. They are known to be fast (about 3000 rpm), which means they need regular maintenance. Still, they are built to be extremely reliable and easy to operate. Centrifuges typically produce the driest cake, meaning the most water possible has been removed. Because they are self-contained, the odor control is not a big issue. This flexible piece of equipment handles changing conditions and does well in all kinds of treatment applications.
Rotary Disc Press
This is a relatively new method that involves feeding flocculated material between slowly rotating screens within each disc assembly. The equipment may contain from one to six discs per unit. Users like the slow rotation (usually between one and three rpm) and how the entire system is self-contained.
Inclined Screw Press
Similar to the rotary disc press, this system feeds flocculated material into an inclined screw that rotates inside a stainless still wedge wire screen. It also operates at a very slow speed and is self-contained. It uses minimal horsepower compared to other methods, resulting in lower operation costs.
Horizontal Screw Press
This system is similar to the inclined screw press, but the flocculated material is fed into a horizontal rotating screen. It works well when higher quantities are anticipated. They have been used traditionally in the pulp and paper industry, and more recently with wastewater treatment plants.
The right sludge dewatering equipment for a treatment facility depends on a variety of factors such as:
– Sludge quantity and composition
– How much space is available for equipment
– How quickly the sludge dewatering must take place
– Operator experience and preferences
– Odor control preferences
– How the sludge cake may be used, such as land applications, landfill disposal, alternative fuels, or additional processing for some other purpose
A professional service should be consulted to help evaluate the facility’s needs to ensure the best, most efficient system is being used for its specific applications.