Bio Digesters & Waste Water Treatment Plants
Sewage is generated by residential and industrial establishments. This includes household waste liquid from toilets, bathrooms, showers, kitchens, sinks etc that is disposed off via sewers. In many locations, sewage also includes liquid waste from industries and commercial places. The separation and draining of household waste into grey water and black water is becoming more common both in developing and developed world. Grey water is water generated from domestic activities such as laundry, utensils washing, and bathing, and can be reused more readily. Black water comes from toilets and contains human waste.
Wastewater and sewage waste is treated in three phases:
- Primary (solid removal),
- Secondary (bacterial decomposition), and
- Tertiary (extra filtration).
Primary Treatment
In primary treatment, sewage is basically stored in a basin where solids (sludge) can settle to the bottom and oil and lighter substances can rise to the top. The solids are then removed and then the remaining liquid is sent to secondary treatment. Sewage sludge is treated in a separate process called sludge digestion.
Secondary Treatment
Secondary treatment removes dissolved and suspended biological matter, often using microorganisms in a controlled environment. Most secondary treatment systems use aerobic bacteria, which consume the organic components of the sewage (sugar, fat, and so on).
Tertiary Treatment
Tertiary treatment (sometimes called “effluent polishing”) is used to further clean water when it is being discharged into a sensitive ecosystem.
The methods employed in cleaning the waste include:
- Sand filtration
- Biological filtration
- Lagooning
- Treatment by activated carbon
- Reverse osmosis