What is Sludge Dewatering and Its Usages & Benefits

Sludge is a residual semi-solid material a.k.a. by-product that is extracted from the slurry during industrial, municipal, or wastewater treatment processes.

During the process of treating wastewater, sludge is formed before the water can be released back into the environment.

This has long been a major challenge for the water treatment industry as it increases health hazards and disposal costs. However, the water treatment industry has found a breakthrough in sludge dewatering. In this post, we focus on what sludge dewatering is, including its usages and benefits.

Sludge dewatering can be defined as the practice of reducing waste by volume to prepare for its effective disposal. Dewatering the sludge requires a dewatering filter press significantly which helps to reduce its weight and its volume before disposal.

Sludge dewatering separates sludge into solids and liquids for waste minimization. Centrifuging, frame filter, and belt filter presses, geomembranes, and screw pressing are the most commonly used dewatering options.

Sludge Dewatering Processes

Before the dewatering process can begin, sludge is conditioned through either organic chemicals such as flocculants and coagulants or mineral chemicals such as iron salts and lime.
After conditioning, the sludge is then thickened using a gravity belt, flotation, centrifuge, or a thickening drum/screw drum. Thickening processes concentrate the sludge by removing part of the free water hence, increasing the dry solids (DS) content to 4-6%.

This way, the finished product retains the liquid, free-flowing characteristics of the feed sludge, which allows it to be conveyed by pumping. Thickening and dewatering processes both provide a concentrated, consolidated product as it retains most of the solids from the original sludge.

Also, it provides a diluted stream which is predominantly water and is usually directed back to the inlet of the wastewater treatment works.
Once the conditioning step is done then analyzing which dewatering technique is next. The choice of a sludge treatment method is hugely dependent on several factors including the volume, characteristics, timing, and available disposal options.

Sludge Dewatering Benefits

In this section, we will highlight six benefits of sludge dewatering.

1. Environmentally-friendly

Sludge dewatering is an eco-friendly procedure in several ways. It reduces the volume of the waste to a more compact size for disposal.

While the dry cakes are disposed of, municipal and wastewater industries can still reuse the filtrate thereby reducing the amount of water needed for treatment overall.

2. Reduced transportation costs

Managing sludge can be very costly but managing sludge accumulation through the use of dewatering equipment can reduce both storage expenses and transportation costs.

3. Constant cake dryness implies a lower risk of spilling or leaking

Sludge spillage or leakage is a major concern for truck drivers. However, the dry, high-solid cakes formed during the sludge dewatering filter presses lowers the risk of spilling or leaking onto the roads which in turn, lower costs of transport.

4. Wastewater recycling

The treated water from sludge dewatering is typically free of contaminants which make it beneficial for communities and some industries. Steam-powered plants, communities, and other industries that require non-potable water can reclaim the water for their various needs.

5. Waste volume reduction

The sludge dewatering process focuses on volume and weight reduction before the sludge by-product can be disposed of. A reduction in waste volume implies a reduction in waste disposal costs.

6. Equipment is easily automated

Certain people think that sludge dewatering filters are labour-intensive. On the contrary, this piece of equipment is easily automated.

For instance, sludge dewatering presses can come with sophisticated control systems, automatic cloth washers, and mechanically-assisted cake release for seamless operation and effective communication to the main plant control system – all of which makes sludge dewatering much easier.

The Bottom Line

Sludge dewatering is typically focused on waste minimization i.e. reducing the volume and weight of the sludge. It can also help to achieve overall cost efficiency i.e. reduced disposal costs, including transportation.

Furthermore, stabilized sludge can be reused, handled more safely, and reduce health hazards.

Generally, both the private and public sectors are required to dispose of sludge in a manner that is approved by regulatory agencies in line with their own organizational requirements and environmentally safe.