Sewage contains about 90% water. This means that there is a lot that can be obtained from recycling. The source of waste water comprises both commercial and residential premises with residential sources bringing in the larger proportion of solid waste. Before being recycled and reused, the waste water has to be taken through a thorough treatment process. A number of stages are involved in this sewage treatment process.
The stages that are involved in the process are the pre-treatment stage, the primary, the secondary and the tertiary stages. The first of them is pre-treatment, this is the stage at which large solid waste such as rocks, pieces of cloth and wood and removed from the rest of the sewage using a series of meshes. The grate size used here ranges from 1.5 millimeters to 5 cm.
Apart from the foreign bodies, sand and grit also have to be removed during the pre-treatment stage. Most of the grit found in sewage is runoff from the street created after rainfall. The force of gravity plays a vital role here by helping separate the grit and the water; the grit sinks to the bottom and the rest of the waste remains at the top as the effluent flows down a gentle slope.
As the wastewater makes its way to the primary stage, it is at first held in large tanks for a few days so that sedimentation can take place. There is a continuous flow occurring simultaneously. This flow brings in effluent from one end and removes water with minimal solids from another end. The solid that collects at the bottom of the tank over time is also referred to as sludge.
The secondary stage is used for the digestion of biologic materials. For this to happen, the water is filled with anaerobic and aerobic microorganism (both bacteria and protozoa). The breakdown of this material produces energy and carbon dioxide and subsequently reduces that nutritional content available for bacterial survival. Additional sedimentation is also done at this stage to get rid of suspended solids carried over from the primary stage.
A different approach can be adopted at this stage to achieve results that are not very different from those obtained with the conventional method. Instead of using live microorganisms in the biological filtration process, enzymes may be used. The enzymes are combined in a manner that will target as much of the material as possible. The disadvantage is that a significant amount of the material goes undigested.
At the tertiary stage, a number of things are done. Among them is the removal of elements such as phosphorus and nitrogen. If the levels of these elements remain high, they have the potential to lead to an effect termed eutrophication. Other important steps that are undertaken here include chlorination, improvement of odor and the reduction of residual organic matter by use of biologic filters.
Although the process of treating waste water is usually done on a large scale by municipalities, you can have your own treatment plant in an onsite septic tank. Just ensure that you fully understand the public health guidelines that apply with regard to the installation and use of such tanks. Generally, small treatment plants have two main stages rather than the standard four stages seen with the large plants.
The stages that are involved in the process are the pre-treatment stage, the primary, the secondary and the tertiary stages. The first of them is pre-treatment, this is the stage at which large solid waste such as rocks, pieces of cloth and wood and removed from the rest of the sewage using a series of meshes. The grate size used here ranges from 1.5 millimeters to 5 cm.
Apart from the foreign bodies, sand and grit also have to be removed during the pre-treatment stage. Most of the grit found in sewage is runoff from the street created after rainfall. The force of gravity plays a vital role here by helping separate the grit and the water; the grit sinks to the bottom and the rest of the waste remains at the top as the effluent flows down a gentle slope.
As the wastewater makes its way to the primary stage, it is at first held in large tanks for a few days so that sedimentation can take place. There is a continuous flow occurring simultaneously. This flow brings in effluent from one end and removes water with minimal solids from another end. The solid that collects at the bottom of the tank over time is also referred to as sludge.
The secondary stage is used for the digestion of biologic materials. For this to happen, the water is filled with anaerobic and aerobic microorganism (both bacteria and protozoa). The breakdown of this material produces energy and carbon dioxide and subsequently reduces that nutritional content available for bacterial survival. Additional sedimentation is also done at this stage to get rid of suspended solids carried over from the primary stage.
A different approach can be adopted at this stage to achieve results that are not very different from those obtained with the conventional method. Instead of using live microorganisms in the biological filtration process, enzymes may be used. The enzymes are combined in a manner that will target as much of the material as possible. The disadvantage is that a significant amount of the material goes undigested.
At the tertiary stage, a number of things are done. Among them is the removal of elements such as phosphorus and nitrogen. If the levels of these elements remain high, they have the potential to lead to an effect termed eutrophication. Other important steps that are undertaken here include chlorination, improvement of odor and the reduction of residual organic matter by use of biologic filters.
Although the process of treating waste water is usually done on a large scale by municipalities, you can have your own treatment plant in an onsite septic tank. Just ensure that you fully understand the public health guidelines that apply with regard to the installation and use of such tanks. Generally, small treatment plants have two main stages rather than the standard four stages seen with the large plants.
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