Microbial treatment of wastewater is done to reduce the amount of organic material in sewage. Microorganisms are necessary to decompose the matter. There are many of these microorganisms found naturally in water bodies and flowing together with the waste but it is still necessary to add artificially prepared organisms to complement the preexisting ones. Preparation involves culturing the desired species in special media so as to yield a colony that is later released into the water.
All bacteria can be categorized based on whether or not they utilize oxygen. The broad groups are the anaerobes, aerobes and the facultative bacteria. Aerobes are bacterial species that cannot live without oxygen. Anaerobes, in contrast, do not need oxygen. They use carbon dioxide gas instead. A facultative organism is one that can survive in presence of either carbon dioxide or oxygen. Aerobes play a key role in organic matter breakdown and it is important therefore that some oxygen is added to the sewage to maintain their large numbers.
There are four main stages of sewage treatment. They are the primary, secondary, the tertiary and the disinfection stages. The first stage (primary) is the point at which the very large solids are removed. These solids are trapped as the sewage passes through a system of grates, filtration points and settling tanks. Sewage exiting this stage contains small suspended and dissolved solids that proceed to the next stage.
Microorganisms are added at the secondary stage. This is what starts the decomposition of organic matter. A few organisms multiply millions of times and spread in the whole sewage. By the time the waste leaves this stage, there is almost no organic matter in it. At the tertiary stage, the main activity is the removal of any washed down nutrients in the waste. The main components in these nutrients are nitrogen and phosphorous. Chlorination is done in the disinfection stage to kill bacteria.
When the amount of organic matter is excessively high, there is need to add more organisms at the tertiary stage. If most of the organisms are removed before the secondary stage, the whole process will be more efficient. The amount of organisms added should not be too much as their concentration may be just too much for the disinfection mechanism downstream.
There are many advantages of treating sewage in this manner. The reduction in the amounts of organic matter in the waste greatly reduces the competition for oxygen. This ensures that important aquatic life in the water bodies in which the effluent is discharged is maintained.
If well organized, the process is an option that is efficient, effective and affordable. Since it is entirely natural, there is no environmental pollution. The odor associated with sewage is reduced by treatment of sludge. Odor is caused by the decomposing action of anaerobic bacteria that produce unpleasant gases such as hydrogen sulphide. The treatment also helps reduce the volume of the waste.
The alternative to microbial treatment of wastewater is the use of enzymes. After being attempted for a while initially, this option was found to be impractical. Apart from being ineffective, it is also very expensive. The main reason as to why this is so is the difficulty involved in choosing a single enzyme that can breakdown all the varieties of matter. Using microorganisms is the easier option because these organisms can produce the required variety of enzymes.
All bacteria can be categorized based on whether or not they utilize oxygen. The broad groups are the anaerobes, aerobes and the facultative bacteria. Aerobes are bacterial species that cannot live without oxygen. Anaerobes, in contrast, do not need oxygen. They use carbon dioxide gas instead. A facultative organism is one that can survive in presence of either carbon dioxide or oxygen. Aerobes play a key role in organic matter breakdown and it is important therefore that some oxygen is added to the sewage to maintain their large numbers.
There are four main stages of sewage treatment. They are the primary, secondary, the tertiary and the disinfection stages. The first stage (primary) is the point at which the very large solids are removed. These solids are trapped as the sewage passes through a system of grates, filtration points and settling tanks. Sewage exiting this stage contains small suspended and dissolved solids that proceed to the next stage.
Microorganisms are added at the secondary stage. This is what starts the decomposition of organic matter. A few organisms multiply millions of times and spread in the whole sewage. By the time the waste leaves this stage, there is almost no organic matter in it. At the tertiary stage, the main activity is the removal of any washed down nutrients in the waste. The main components in these nutrients are nitrogen and phosphorous. Chlorination is done in the disinfection stage to kill bacteria.
When the amount of organic matter is excessively high, there is need to add more organisms at the tertiary stage. If most of the organisms are removed before the secondary stage, the whole process will be more efficient. The amount of organisms added should not be too much as their concentration may be just too much for the disinfection mechanism downstream.
There are many advantages of treating sewage in this manner. The reduction in the amounts of organic matter in the waste greatly reduces the competition for oxygen. This ensures that important aquatic life in the water bodies in which the effluent is discharged is maintained.
If well organized, the process is an option that is efficient, effective and affordable. Since it is entirely natural, there is no environmental pollution. The odor associated with sewage is reduced by treatment of sludge. Odor is caused by the decomposing action of anaerobic bacteria that produce unpleasant gases such as hydrogen sulphide. The treatment also helps reduce the volume of the waste.
The alternative to microbial treatment of wastewater is the use of enzymes. After being attempted for a while initially, this option was found to be impractical. Apart from being ineffective, it is also very expensive. The main reason as to why this is so is the difficulty involved in choosing a single enzyme that can breakdown all the varieties of matter. Using microorganisms is the easier option because these organisms can produce the required variety of enzymes.
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