Wastewater Sludge

What is Sludge in Environmental Engineering?

Sludge is a semi-solid substance formed during water and wastewater treatment that is removed by settlement. It is a substance that requires further treatment; unless this is done it may pose harm to the environment and public health.

Why further treatment is needed for sludge?
Because sludge includes; large amounts of organic matter, nurients, pathogenic microorganism, huge amount of water.

Sludge production amounts
In order to calculate the amounf of sludge produced in a conventional domestic wastewater treatment plant, dry solid matter content is assumed as roughly 0.09 kg per capita per day in wastewater treatment. For instance, for a residential area with 1.000.000 population, 90-100 tons sludge production can be expected in a day.

Sludge	Conc.of Solids (%)	Characteristics
Raw Primary	4-8	Bad odor, gray-brown color, does not drain well on drying beds, can be dewatered mechanically
Anaerobic Primary Digested	6-10	Black color, produces gas, dewaters well on drying beds
Wasted Activated Sludge	0.5-1.5	Little or no odor, yellow-brown color, flufly, biologically active, difficult to dewater
Mixed Digested (Primary and Waste Activated)	2-4	Black-brown color, produces gas, not as easy to dewater as digested primary
Aerobic Digested	1-3	Yellow-brown color, biologically active, generally difficult to dewater
Waste Alum	0.5-1.5	Grey-yellow in color, odorless, very difficult to dewater