There are various alternative waste treatment technologies e.g. physical treatment, chemical treatment, biological treatment, incineration etc. These processes are used to recycle and reuse waste materials reduce the volume and toxicity of a waste stream or produce a final residual material that is suitable for disposal.
This includes processes that separate components of a waste stream or change the physical form of the waste without altering the chemical structure of the material. Commonly used physical processes are as follows:
1. Screening and Sedimentation.
2. Flotation-Removes solids from liquids by floating the particles to the surface by using tiny air bubbles.
3. Filtration-Process for separating liquids and solids by using various types of porous materials.
4. Centrifugation-Process for separating solid and liquid components by rapidly rotating a mixture of solids and liquids inside a vessel.
5. Dialysis-Process for separating components in a liquid steam by using membrane components of a liquid stream will diffuse through the membrane if a stream with greater concentration of the component is on the other side of membrane.
6. Eleetrodialysis- It is an extension of dialysis. This process is used to separate the components of an ionic solution by applying electric current.
7. Reverse Osmosis-It separates components by applying external pressures to one side of membrane.
8. Ultra filtration-It is similar to reverse osmosis but the separation beings at higher molecular weights.
9. Distillation-Process of separating liquids with deferent boiling points. The mixed liquid stream is exposed to increasing amounts of heat and the various components of the mixture are vaporized and recovered.
These alter the chemical structure of the constituents of the waste to produce less hazardous material. Chemical processes are attractive because they produce minimal air emissions, they can be carried out on the site. Commonly used chemical treatments are given below:
1. Neutralization-Process for reducing the acidity or alkalinity by mixing acids and bases.
2. Precipitation-Process for removing soluble compounds.
3. Dechlorination-A process for stripping chlorine atoms from chlorinated compounds.
4. Oxidation-reduction-Process for detoxifying toxic wastes in which the chemical bonds are broken.
It includes processes that use microorganisms to decompose organic wastes either into water, C02 and simple inorganic substances.
The purpose of biological treatment system is to control the environment for microorganisms so their growth and activity are enhanced.
Various biological treatments are:
1. Activated sludge Process
2. Aerated Lagoon
3. Trickling filters
4. Stabilization Pond
5. Anaerobic digestion