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This is how these mysterious sewage treatment systems work!
Sewage treatment systems, especially septic tank systems, are working quietly and silently around our lives, but do you really understand how they work? A septic tank is a basement chamber, usually constructed of concrete, fiberglass, or plastic, that is used primarily to treat a household's sewage. In the septic tank, sewage undergoes preliminary purification, and solid and organic matter are reduced during sedimentation and anaerobic digestion, but its treatment efficiency is only that of preliminary treatment.
Two main treatment processes, including settling of solids and anaerobic decomposition, allow septic tanks to initially remove impurities from sewage.
Septic tank systems are ideal for locations without an online sewage system, especially in remote or rural areas. Treated liquid wastewater typically flows into a septic tank drain field as a means of further treatment. While these systems offer an efficient way of living, the effects of wastewater treatment can also lead to problems with groundwater contamination if not managed properly.
The name septic tank comes from its anaerobic environment, which encourages microorganisms to further break down incoming waste. Depending on the design of the depot, the septic tank may be combined with other sewage treatment units such as biofilters or aerobic systems requiring artificial aeration. It’s important to note that sediment—also known as fecal sludge—usually accumulates faster than it breaks down, meaning septic tanks must be pumped out regularly to avoid excessive buildup.
When there is too much sediment in the septic tank, the sludge must be regularly extracted using a suction truck.
Structure and operation of septic tanks
A septic tank is a tank structure with a capacity of between 4,500 and 7,500 litres, usually connected to an inlet pipe at one end and to a drain field at the other. These connections are mostly T-shaped pipe designs so that the liquid inflow and outflow will not disturb the scum above the liquid surface.
Most septic tank designs today consist of two chambers, each with a cover and separated by a partition wall. The wastewater first flows into the first chamber, where the solids settle and the scum floats up. The settled solids are then subjected to anaerobically digested to further reduce the volume of solids. The liquid portion then flows through the partition wall into the second chamber, where sedimentation occurs again. Finally, the treated liquid flows into the septic tank drain field, which drives away excess water.
After a series of settling and filtration processes, the treated wastewater will seep into the soil over time, further purifying it in the process.
Emptying and maintenance of septic tanks
While septic tanks are effective in treating some wastewater, they still need to be regularly emptied of undecomposed sludge material. If not cleaned, septic tanks may overflow, causing sewage that should have been cleaned to be discharged directly into the drain field, causing damage to the environment. How often a septic tank needs to be emptied depends on its volume, solid input, and usage. These factors may affect the timing and frequency of emptying, and some local health authorities may even specify regular time intervals for emptying.
Regular inspections and emptying can extend the life of a septic tank to decades, and septic tanks made of different materials can last up to 50 years.
Environmental impact
In terms of environmental protection, although a well-maintained and properly designed septic tank system will not cause more environmental problems than a centralized sewage treatment system, pollution caused by septic tanks in unsuitable locations is still a problem. Quite serious. Many small towns are faced with the necessity of building expensive centralized sewage treatment systems due to groundwater pollution.
And in some areas, such as when fish and shellfish harvests are limited, poorly managed septic tanks can also pollute waterways, affecting fishing and other activities. This has led to higher demands and standards for effective sewage treatment and septic tank management.
The effective operation of the septic tank system is highly dependent on the user's behavior and the influence of the surrounding environment. Any improper handling or excessive use may lead to the risk of immediate saturation and blockage. Facing the future, is there a better way to treat sewage worth exploring?
