Sludge dewatering:

• The purpose of sludge dewatering is for waste minimization and to achieve overall cost efficiency for disposal. Sludge dewatering separates sludge into liquid & solid component for waste minimization.

• It is important to note that dewatering is not intended to treat the sludge or liquid. it only separate the solids & liquid component so that its easier & more cost effective in handling & final disposal.

• Sludge dewatering is typically focused on reducing the weight and volume of the sludge so that its disposal cost including transportation are kept minimum.

• A sludge drying bed is a common method utilizes to dewater sludge via filtration, evaporation. Perforated pipes situated at the bottom of the bed are used to drain seepage water or filtrate. A reduction of about 35% or less in moisture content expected after drying.

Construction or working :

• A sludge drying bed usually consists of a bottom layer of gravel of uniform size over which is laid a bed of clean sand. Open jointed the under drains are laid in the gravel layer to provide positive drainage as the liquid passes through the sand and gravel.

• Under drain made of vitrified clay pipes or tiles of at least 10cm diameter laid with open joint.

• The drying bed is usually 6 to 8 m wide and 30 to 45 m long.

• The sludge should be deposited evenly to a depth of not greater than 20m.

• The major portion of liquid drains off in a few hours after which drying commence by evaporation, this produce crack in sludge.

• It about 2 to 3 week sludge cake dries up completely with 20 to 40% of volume reduction and can be removed.