Wastewater treatment is used to convert wastewater or sewage water into bilge water, which can be discharged back into the environment or natural water bodies such as rivers, lakes, estuaries, and oceans. Wastewater consists of the pollutants of many activities including bathing, washing, and toilet and rainwater runoff. It is full of bacteria, chemicals and other toxins, including contaminants.
Water treatment plants aim to reduce the contaminants to an acceptable level to ensure that the water is safe for environmental discharge. While water quality is affected by natural conditions, the word pollution typically involves a source of contamination for human activity.
The process of wastewater treatment plants
Wastewater treatment plants produce waste containing a large number of potential contaminants. Wastewater collected is usually sufficiently clean to be used for irrigation, but generally comprises greater dissolved solid levels compared to the water source.
- Collection of wastewater: This is the first step in the process of wastewater treatment. The collection systems are developed by local government, homeowners and business owners to ensure the collection and transfer of the entire wastewater to a central point. This water is then transferred by underground drainage systems or exhauster tracks to a treatment plant.
- Preliminary treatment: Removals of ground solids and other significant materials often found in raw wastewaters is a part of preliminary treatment. To improve the operation and retention of subsequent treatment units, the removal of these materials is necessary.
- Primary treatment: Material which either floats or settles readily by gravity is removed from primary treatment and includes physical processes of screening, comminution, grain removal, and sedimentation.
- Secondary treatment: It is also known as activated sludge treatment. Seed sludge is added to the wastewater for secondary treatment to ensure that it further breaks down. For the removal of sludge and scum, settling tanks are utilized.
- Trickling filter: A trickling filter or bioprotective filter is composed of a basin or a tower filling with stone, plastic or wooden slats for supporting media. Wastewater is applied to the media intermittently, or sometimes permanently. Microorganisms attach to media and form a fixed film or biological layer. Organic matter spreads to the film in wastewater, which metabolizes it.
- Activated sludge: Aeration tanks, followed by a secondary clarifier, form the activated sludge treatment system. Into the aeration tank is the settled waste, mixed with fresh sludge that is recycled from the secondary clarifier.
- Tertiary treatment: It is similar to the one used by potable water treatment plants for drinking clean raw water. Up to 99% of impurities can be removed from wastewater during the tertiary treatment process.
Why is wastewater treatment required?
Wastewater treatment is one of the most critical conservation processes to be promoted globally. Metals, nutrients and specialized chemical products are complex blends of wastewater. The recovery of these valuable materials can help compensate for the increasing demands of a community for natural resources.
Water treatment systems and recovery concepts are changing, and many technologies are being investigated and developed by researchers. Particular focus areas are reclaiming and reusing treated water to irrigate, recharge groundwater or recreation.