Presented by:
A.KUMARAVEL

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What Is Waste Treatment?
Waste treatment techniques are used to change the physical, chemical, or
biological character of the waste, to reduce its volume and/or toxicity, and to
make the waste safer for disposal.
How Is Waste Treated?
Treatment methods are selected based on the
• composition,
• quantity, and
• form of the waste material
METHODS OF WASTE TREATMENT
The treatment methods can be classified into three main categories:
• Physical treatment
• Chemical treatment
• Biological treatment
PHYSICAL TREATMENT
• Sedimentation
• Filtration
o Screening
o Bed filtration
• Flotation
• Evaporation
• Dialysis
• Absorption
PHYSICAL TREATMENT
This includes devices like:
• Coarse or fine screens as well as bar screens to remove bricks, wood pieces, paper, cloth etc.,
• Comminuting devices like grinders, cutters which are employed to break up solid material.
• Grit chambers is employed to arrest sand, dust, stones and other inorganic settleable material.
• Grease traps is used to remove unemulsified oil and grease from the effluents.
• Plain sedimentation tanks are employed to primarily remove suspended organic solids from the waste waters prior to biological treatment.
SEDIMENTATION
Sedimentation is the separation from water, by gravitational settling, of suspended particles that are heavier than water.
Suspended substances with
• higher specific gravity values get deposited to the bottom
• Lesser values float to the medium of suspension
A settling tank should be big enough so that it takes a long time to get through.
Inlets and outlets are designed so the water moves slowly in the tank.
Long and narrow channels are installed to let the water to snake its way through the tank.
The settled particles, sludge, must occasionally be removed from the tanks.
Sedimentation is used in pre-treatment and wastewater treatment.
FILTRATION
Filtration is the process of removing solids from a fluid by passing it through a porous medium.
• Coarse, medium, and fine porous media have been used depending on the requirement.
• The filter media are artificial membranes, nets, sand filter, and high technological filter systems.
• The choice of filters depends on the required filtering speed and the cleanness requirement.
• The flow required for filtration can be achieved using gravity or pressure.
• In pressure filtration, one side of the filter medium is at higher pressure than that of the other so that the filter plane has a pressure drop.
• Some portion of this filter type must be enclosed in a container.
CLASSIFICATION OF FILTRATION SYSTEMS
• The type of operation
• The type of filtering medium used
• The direction of flow during filtration
• The backwashing process
• The method of flow rate control
Screening
Particles when allowed to pass through screen of lesser pore diameter, get retained on the surface.
Purpose:
• To protect pumps and other mechanical equipment
• To prevent clogging of valves
Bed filtration
Combination three actions:
• Particles larger than the filter medium opening cling to the filter
• Particles smaller than the openings in the filter medium, get absorbed into the filter
• Particles of different sizes cling to already filtered caked material
FLOTATION
Flotation is the buoyancy unit process of separating ‘solid’ particles from a liquid
phase.
Eg.
Industrial plants – waste oil products
Milk industry – fats and grease among its liquid wastes etc.,
Floatation system includes
• Gravity flotation
• Vacuum flotation
• Electro flotation
• Air flotation
DIALYSIS
Solutes with unequal diffusion powers, when subjected to pass through membranes, get separated.
ABSORPTION
Under the influence of different surface forces many substances may retain
certain of compounds on their exposed surface.
EVAPORATION
Under the influence of heat, water and low boiling compounds of the
effluent evaporates, leaving behind other dissolved and suspended solids.
SUMMARY
• Waste treatment technologies of the future will most likely promote sustainable economic development, particularly in terms of saving resources and energy.
• Recycling, which is economically efficient and based on appropriate waste treatment, will be important, but gradual progress is also expected in reducing waste discharge volumes both at the individual level through lifestyle changes, and at the corporate level through efforts at so-called "zero emission."
• We will also see increases in material recycling, thermal recycling, appropriate processing of toxic matter, and technologies to preserve life environments.
Treatment
• Treatment is any process that changes the physical, chemical, or biological
character of a waste to make it less of an environmental threat.
• Treatment can neutralize the waste, recover energy or material resources from a waste, render the waste less hazardous, or make the waste safer to transport, store, or dispose of.