When you hear “cake” in wastewater, it’s not about a birthday celebration. It refers to the solids that remain after removing water from sludge.

Several ways to dewater sludge include setting up a pond or basin and using mechanical methods like belt filter presses and centrifuges. Dewatering machines reduce sludge disposal costs charged on a weight basis.

Reduces Waste

Mechanical dewatering removes water from a slurry, reducing its volume and making it easier to transport or dispose of. It can reduce waste disposal costs for facilities that pay on a weight basis. It also saves on energy used to heat-dry the slurry.

Traditional mechanical dewatering techniques include belt filter presses and centrifuges. These machines separate sludge (residual sludge from wastewater treatment plants and fecal sludge from on-site sanitation) into liquid and solid parts. The liquid can be circulated back into the wastewater plant or treated in a constructed wetland, while the substantial part is either burned in a small or large-scale incineration plant or composted.

A settling pond is another traditional method of separating a slurry into its liquid and solid components. However, a pond is expensive to build and maintain. In addition, a pond requires a lot of space to contain the slurry. Sludge is also slow to process, as particles take days to settle out of the water column.

Reduces Energy

Dewatering uses mechanical forces to separate water from solids, reducing the volume of wastewater sludge for transport or disposal. It significantly reduces waste disposal costs for facilities that pay on a weight basis. It also decreases the need for settling ponds and energy used in fossil fuel heat-drying processes.

Thickening and dewatering technologies provide a concentrated, consolidated product that retains the original sludge solids but a dilute stream that is mostly water. The dewatered sludge cake typically has a TS (total solids) content of 13-46%, with some soluble salts remaining.

Using mechanical dewatering systems like belt filter presses, centrifuges, or screw presses requires less capital and energy than other processing methods. It allows utilities to invest in equipment that will save them energy and money. Pilot testing is essential to determine the maximum solid loading of a dewatering machine and other critical parameters such as polymer feed rate, press pressure, filtrate volumes, and TS concentrations.

Reduces Health Risks

Sludge contaminated with fecal matter and other contaminants can pose health risks to humans, wildlife, and plants. Separating the liquid and solid components is necessary to reduce these risks. It is often done through dewatering. Dewatering allows for easier and more cost-effective handling of the liquid phase and minimizes the potential for contamination.

Mechanical dewatering methods like belt presses and centrifuges use mechanical pressure to remove water from a slurry. It can significantly reduce the volume of waste, making it much easier to transport and store. This can also save on costly waste removal and treatment services that are charged based on the weight of wet waste.

Sludge dewatering is typically a part of the wastewater treatment process but can also be used in industrial applications like mining. This technique is a safe, effective, low-energy alternative to chemical dewatering. Pilot testing using full-scale equipment provides accurate design and performance data. It includes test results for the maximum solids loading, polymer feed rate, press pressure, filtrate volume, and solids concentration.

Reduces Environmental Impact

When it comes to dewatering sludge, most processes involve a large amount of energy. That is because mechanical systems like belt presses and filter press machines use tremendous hydraulic pressure to remove water from sludge.

These machines can have high initial startup costs and require a long period to reach the entire operation. However, they provide significant cost savings over the long term, particularly when compared to thermal dewatering technologies such as aeration basins and ponds.

In addition to being cheaper, mechanical dewatering also reduces the environmental impact of waste management by reducing the volume of sludge for transport and disposal. It is essential for municipalities with landfill fees charged on a weight basis. Pilot tests of selected treatment technologies at full scale can help utility operators evaluate equipment and determine the maximum solid load on the dewatering machine, polymer feed rate, press pressure, filtrate volumes, and substantial concentrations. By doing this, they can make informed decisions about the system that best suits their needs.