Which process is used to concentrate sludge?

The thickener is the correct process used to concentrate sludge. In wastewater treatment, a thickener is designed to increase the solids content of the sludge, making it easier to handle and reducing the volume that must be processed or disposed of. This is achieved through gravitational settling, where the solids settle to the bottom, leaving the clearer liquid (supernatant) on the top. This process effectively increases the concentration of solids, which is vital for efficient treatment and subsequent steps, such as anaerobic digestion or dewatering.

While other methods like sand beds, solar lagoons, and centrifuges are also used in wastewater treatment, they serve different purposes. Sand beds are typically utilized for filtration processes rather than thickening. Solar lagoons exploit natural evaporation for treatment and may not specifically focus on sludge concentration. Centrifuges can also concentrate sludge but do so through mechanical means involving high-speed rotation, which requires more energy and maintenance compared to the gravitational process used in thickeners. Each of these methods has its applications, but in terms of specifically concentrating sludge, a thickener is the most efficient and widely used option.