Waste water treatment:-
Wastewater treatment is the process of cleaning the sewage and domestic water by removing contaminants in the form of organic matter. It is done so to improve the quality of water so that humans and animals can consume it and make use of it for other purposes.

Methods of cleaning the wastewater:-
There are three different methods for wastewater treatment.

Biological Water Treatment:-
When the water is used for drinking or cleaning, it should be cleaned so that there are no contaminants in it which can affect the human health. For this purpose, biological water treatment is used in which microorganisms especially bacteria play an important role. They decompose the wastewater biochemically or they break don the organic material and improve the quality of water so that it can be used domestically. Biological water treatment is divided into three categories that are aerobic, anaerobic and composting.

- Aerobic process:-
In this process, bacteria degrade or eat the organic matter and convert it into carbon dioxide which can be used by plants for their growth. Oxygen is used during aerobic process.
- Anaerobic Process:-
In thi s process, fermentation process is used to ferment the sludge or waste at a specific temperature. Oxygen is not used in this process.
- Composting:-
It is the type of aerobic process in which in the presence of oxygen, sludge is mixed with sawdust or other carbon sources. In this way, wastewater is treated.
Everyday, wastewater or sewage is produced. It is produced when waste of factories is thrown in the lakes and ponds; it makes the water dirty and unhealthy for human use as well as for the water creatures like fish. Sewage is also the wastewater produced at home. It is necessary to treat this water effectively to use it for drinking. Before it is used for drinking or other environmental purposes, it should be transferred to the sewage treatment plants with great care because if there is leakage in the pipe, it will damage the clean water and soil. It is necessary to clean the wastewater otherwise it will become a source of causing diseases in humans.

Physical Water Treatment:-
In this method physical methods are used in cleaning the wastewater and making its quality better. In this method, no chemicals are biological processes are involved. There is a prominent method for physical water treatment called sedimentation. Sedimentation is a process of suspending out the insoluble heavy particles from the wastewater. This method is best for purifying the water. When the insoluble materials settle down at the bottom of the water, pure water is removed.

Another method which can be used for physical water treatment is called as aeration. In this process air is circulated through the water to provide oxygen to it. It is also an affective method of cleaning the wastewater. Another method filtration is used to filter out the contaminants. Special kinds of filters are used to pass sewage or wastewater due to which the insoluble particles or contaminants are separated. The mot commonly used filter is the sand filter. Some wastewaters contain grease or oil on their surface; they can also be removed from the surface easily.

Chemical Water Treatment:-
As the name shows, to clean the water or sewage, chemicals are used. Most commonly used chemical is chlorine and the method in which chlorine is used called as chlorination. Chlorine is the oxidizing chemical used to kill the bacteria which decomposes water by adding contaminants to it. Another oxidizing disinfectant called as ozone is used to purify the wastewater. These chemicals are very useful as they disallow the bacteria to reproduce in the water thus making the water pure. When the treatment of industrial wastewater is concerned then a special method is used called neutralization. A base or acid is added to the water to level its pH. Lime is the base which is most commonly used in the acidic wastewaters. Metals which have more than one valence are most commonly used chemicals in the chemical wastewater treatment. There are some methods of purifying sewage and wastewater which are used in both physical and chemical water treatments. Carbon usage is the best example which has the ability to adsorb harmful substances from the wastewater.

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