The correct answer is: B. Sludge disposal
Composting and lagooning are methods of sludge disposal. Sludge is a solid waste produced by wastewater treatment plants. It contains a variety of organic and inorganic materials, including bacteria, viruses, and parasites. Sludge disposal is a major challenge for wastewater treatment plants, as it can be a source of pollution if not properly managed.
Composting is a biological process that converts organic matter into a stable, humus-like material. It is a safe and effective way to dispose of sludge, as it kills harmful pathogens and reduces the volume of sludge by up to 50%.
Lagooning is a method of sludge disposal that involves storing the sludge in a lagoon. The lagoon is a large, shallow pond that allows the sludge to decompose naturally. Lagooning is a relatively inexpensive method of sludge disposal, but it can be a source of odor and air pollution.
Sedimentation is a physical process that separates solids from liquids. It is a common method of removing solids from wastewater, but it is not effective for removing sludge.
Filtration is a physical process that removes suspended solids from liquids. It is a common method of removing solids from drinking water, but it is not effective for removing sludge.