Waste water management is an exercise that affects both residential and commercial buildings. The main reason for a sewage water treatment system is to produce an effluent that is safe to be discharged into the environment or reused for other purposes. The stages and the process that are involved vary slightly from place to place. In general, however, there are four main successive stages that are involved. These include pre-treatment, primary, secondary and tertiary treatment.
During pre-treatment (screening), meshes are used to remove extraneous elements carried in the sewage. There are three sizes of meshes arranged in series. The largest grate is about 5 centimeters and helps to get rid of wood, rocks, pieces of cloth and other objects. In larger plants, this may be achieved by use of large mechanical bar rakes that apply a continuous motion. The medium size is between 0.5 and 0.3 cm while the smallest is 1.5 to 3.0 millimeters.
Grit removal is another important process that takes place during the pre-treatment stage. Most of the grit found in sewage comes from street runoff when it rains. The process that is used here is gravity dependent. By allowing the effluent to flow through a V-shaped shaped channel on a gentle slope allows grit to settle at the bottom making easier to remove. As a result of all these process, damage to hardware found downstream is markedly reduced.
For the primary stage, large tanks are required. These tanks hold the effluent for some time and allow for sedimentation to take place. A continuous slow flow in and out of these tanks takes place but the average residence time allows for most suspended solids to settle at the bottom. The solids that settle at the bottom are known as sludge. They may be digested to produce methane or disposed in landfills.
The secondary treatment stage involves the breakdown of biological waste. This is achieved by use of microorganisms such as protozoa, anaerobic bacteria and aerobic bacteria. When the material is broken down, the concentration of harmful microorganisms is markedly reduced. There are two main types of systems that are involved: the fixed film system and the suspended growth system. In the former system, biological contactors and trickling filters are used while in the latter the sewage is directly mixed with biomass.
Another alternative approach is to use enzymes instead microorganisms in the secondary stage. The enzymes are similar to those that are produced by the microorganisms. This method appears to be less preferred due to the inability to produce all the enzymes needed. This makes the process very inefficient. At the same time, it is more expensive.
The tertiary stage is the final stage in the process. It involves a number of process that are mainly used to optimize on the benefits that have been achieved with the other stages. Biological filters are often used here to break the organic materials further. Other important processes include disinfection, reduction in the levels of urea and the associated odor. Many plants tend to skip this stage if the water is not for reuse.
It is possible to carry out the treatment using your own septic tank. All you need to do is to ensure that you are conversant with the public health guidelines that govern the installment and the operation of the tank. Most onsite plants comprise a two stage system rather than the standard four stages.
During pre-treatment (screening), meshes are used to remove extraneous elements carried in the sewage. There are three sizes of meshes arranged in series. The largest grate is about 5 centimeters and helps to get rid of wood, rocks, pieces of cloth and other objects. In larger plants, this may be achieved by use of large mechanical bar rakes that apply a continuous motion. The medium size is between 0.5 and 0.3 cm while the smallest is 1.5 to 3.0 millimeters.
Grit removal is another important process that takes place during the pre-treatment stage. Most of the grit found in sewage comes from street runoff when it rains. The process that is used here is gravity dependent. By allowing the effluent to flow through a V-shaped shaped channel on a gentle slope allows grit to settle at the bottom making easier to remove. As a result of all these process, damage to hardware found downstream is markedly reduced.
For the primary stage, large tanks are required. These tanks hold the effluent for some time and allow for sedimentation to take place. A continuous slow flow in and out of these tanks takes place but the average residence time allows for most suspended solids to settle at the bottom. The solids that settle at the bottom are known as sludge. They may be digested to produce methane or disposed in landfills.
The secondary treatment stage involves the breakdown of biological waste. This is achieved by use of microorganisms such as protozoa, anaerobic bacteria and aerobic bacteria. When the material is broken down, the concentration of harmful microorganisms is markedly reduced. There are two main types of systems that are involved: the fixed film system and the suspended growth system. In the former system, biological contactors and trickling filters are used while in the latter the sewage is directly mixed with biomass.
Another alternative approach is to use enzymes instead microorganisms in the secondary stage. The enzymes are similar to those that are produced by the microorganisms. This method appears to be less preferred due to the inability to produce all the enzymes needed. This makes the process very inefficient. At the same time, it is more expensive.
The tertiary stage is the final stage in the process. It involves a number of process that are mainly used to optimize on the benefits that have been achieved with the other stages. Biological filters are often used here to break the organic materials further. Other important processes include disinfection, reduction in the levels of urea and the associated odor. Many plants tend to skip this stage if the water is not for reuse.
It is possible to carry out the treatment using your own septic tank. All you need to do is to ensure that you are conversant with the public health guidelines that govern the installment and the operation of the tank. Most onsite plants comprise a two stage system rather than the standard four stages.
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