Domestic wastewater is the wastewater that results from human activities such as bathing, washing clothes, cleaning dishes, using the garbage disposal, and using the toilet. It contains small amounts of contaminants, yet these small amounts of pollutants can have a negative impact, on the environment.
Therefore, the impact on ground water and surface water will be reduced, by a properly installed and maintained domestic sewage or wastewater treatment system, for treating and disposing of household wastewater.
Why should domestic wastewater be treated?
Domestic waste treatment ensures that all sewage from homes is correctly handled to make it safe, hygienic, and ready to be released back into the air, water, or lakes.
Domestic wastewater may contain pathogenic bacteria, contagious viruses, common home chemicals, and excess nutrients like nitrate. Black water, which comes from toilets and urinals, and grey water, which comes from kitchen sinks, wash basins, laundry, showers, and baths, are the two main fluxes that make up household waste.
Treatment of domestic wastewater
Domestic wastewater is broken down by a household sewage treatment system, in three basic steps.
1. Initial treatment
a. This is the initial step in the treatment of sewage and wastewater, and it gets rid of 40–60% of the suspended particulates.
b. It entails screening to get rid of big things like sticks, stones, etc. that can harm tank inlets.
c. It uses a grit chamber, which slows down wastewater flow, so that grit can fall out naturally and be removed at the tank's bottom.
d. In this stage, pollutants that are floating and sinking are removed using a primary clarifier, or settling/sedimentation tank.
e. The secondary treatment system receives the partially processed wastewater, from the primary tanks.
2. Secondary Stage
a. At this stage, biological (aerobic/anaerobic) treatment of wastewater from the primary stage starts, and up to 90% of organic matter is removed.
b. It employs an activated sludge technique that significantly reduces organic matter, by encouraging the formation of biological floc by using dissolved oxygen.
c. To speed up the decomposition of organic matter, bacteria-rich "activated sludge" is continuously re-circulated, back into the aeration tank.
d. The dissolved and finely divided suspended particles that are not eliminated by primary sedimentation, are attacked by bacteria.
e. The water is then transferred to settling tanks where the sludge once more settles, removing 90 to 95 percent of the contaminants from the water.
3. Tertiary Stage
a. A third stage of treatment known as tertiary or advanced treatment may be used, if the effluent from secondary treatment is deemed undesirable.
b. It serves as the final stage of treatment to bring the effluent quality up to the desired level.
c. Fine particles and suspended materials are still present in the wastewater at the tertiary stage, where they are removed.
d. The water is now almost entirely free of pollutants and hazardous substances, making it suitable for recycling, reusing, or releasing into the environment.
e. This stage is also known as the disinfection stage, and UV is the best disinfectant for sewage because it doesn't affect the quality of the water.
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