If you’ve wondered what mechanical dewatering is, you’re not alone. There are many methods of dewatering available. You’ve probably heard of centrifuges, screw presses, microwave-assisted dewatering, sludge drying beds, and more. You can also learn more about these methods’ differences and advantages and disadvantages.
Centrifuges
Using centrifuges for mechanical dewatering is essential for waste management. Wastewater treatment is a necessary ecological process in the United States. Waterborne disease control and solid matter disposal are critical issues in wastewater treatment, and reliable equipment is essential. Centrifuges for sludge dewatering are crucial to proper municipal wastewater treatment.
Continuous solid-bowl centrifuges: A centrifuge designed for continuous solid-bowl dewatering has a smaller radius than its liquid overflow port. Moreover, part of the solids settles into the bowl’s conical shape. The resulting pond allows for the drying of settled solids. The picture shows a typical centrifuge thickening and dewatering system.
Screw presses
Two types of screw presses are available in the market: single disc and multi-disc. One of the two types is designed to separate solid particles and remove water from a liquid using centrifugal force. Both are efficient dewatering devices. Each dewatering tool uses a different process to achieve the desired results. In addition, each of them is equipped with a unique set of features.
The first type of screw press uses an in-built hydraulic motor to push the solids through a nozzle to be filtered. Screw presses are best suited for continuous dewatering and filtration. They are used in nutrient management programs to dewater cow and hog manure. You can also use them in food processing factories to remove water and solids from waste streams and convert them into animal feeds.
Microwave-assisted dewatering
A recent study investigated the effect of microwave-assisted mechanical dewatering on sludge. They improved the dewatering ability of sludge by adding a composite bioflocculant, which enhances both dry solids and SRF. Although the microbial flocculants are pollution-free, they are expensive and must be replaced frequently. Heat treatment is considered the most effective method for improving sludge dewatering. Microwave dehydration is superior to thermal heating.
In addition to the mechanical dewatering process, this method also facilitates the production of biofuels and green platform chemicals, including hemicellulose and lignin. The process effectively converts organic materials such as waste paper into biofuels and chemicals. It is also beneficial in producing biodiesel, biolubricants, and carbon nanospheres. The method also promotes the depolymerization of cellulose and lignin by using microwave-induced spray evaporation.
Sludge drying beds
Conventional sludge drying beds are relatively straightforward, with high solids concentration and low capital costs. However, they lack rational design and are not appropriate for all types of wastewater.
Sludge drying beds differ in size depending on how much wastewater they treat. The amount of solids in the dried sludge is also variable, so you must decide the number of beds. For example, the volume of solids produced by a small treatment plant can vary significantly from one large facility to the next. In smaller plants, manual shoveling is sufficient. Trucks typically pick up the dried solids.
Mechanical dewatering of sludge is an essential part of the wastewater treatment process. A single bed can dewater 2.5 to 5.0 kg of solids per square meter or 0.5 to 1 lb/ft2 of sludge. However, the resulting cake remains relatively wet, complicating disposal. To solve this problem, the sludge is preconditioned with polymer and introduced to a depth of 300 to 750 mm. Then, the sludge is drained for an hour, allowing it to dry to a final solids content of 20 to 40%.
