Different Level Of Water Treatment Process

As mention in the previous post, there are 3 different levels of water treatment process. Primary treatment, secondary treatment, and tertiary treatment.

PRIMARY TREATMENT

For primary treatment, It is the process where we separate suspended solids like rocks, lump of soil, toilet paper etc, through sedimentation, chemical coagulation

, and precipitation so that we can reduce the amount of BOD in the wastewater. It's technology contains of Bar Screen, Grit Chamber, and Primary Settling Tank.

This process is essential as it enhance the operation and maintenance of subsequent treatment units. By removing suspended solids, we can reduce the amount of BOD by 20%-30% and up to 60% for suspended solids.

Firstly, waste water would be directed into the chamber with bar screen which filters out large solids such as toilet paper, plastic bottles, to prevent damages in the secondary and tertiary treatment.

Secondly the wastewater would flow into the grit chamber and the sands or smaller stones that cannot be filtered out by the bar screen would settle down.

Lastly, the grit chamber will remove these dense object and the wastewater is now free from insoluble objects.

SECONDARY TREATMENT

The secondary treatment consists of the aeration tank (bio-reactor) and final clarifiers. The wastewater is mixed with a culture of micro-organism known as activated sludge in the aeration tank. Organic pollutants in the wastewater are digested and broken down by the micro-organism. To sustain biological activities in the aeration tank, oxygen from the air is dissolved into the wastewater to maintain certain level of dissolved oxygen in the wastewater. Oxygen is supplied to the aeration tank by providing air through airholes placed at the bottom of the aeration tanks to create fine air bubbles.

The oxygen supplied will also help to speed up the bioreaction process. At the end of aeration process, where we stop supplying oxygen into the Aeration tank, most of the microorganism would have digested most of the pollutants. After this process, it would be directed ito the Secondary settling tank

At the Secondary Settling Tank, all the sludge would settle down to the bottom of the tank producing clear supernatant water. The supernatant are then tapped out of the tank as final effluent. The settled sludge that is at the bottom of the tank would then be discharged out to be recycled and excess sludge are to be treated.

TERTIARY TREATMENT

Tertiary treatment is to provide a final polishing treatment stage prior to discharge or reuse of the wastewater. Methods include Chlorination, Ozonation, Ultraviolet Radiation and Activated Carbon Absorption.

Firstly, Chlorination is a water treatment method that denatured harmful bacterial, parasites, and other organisms.

which also removes sokuble iron, manganese and hydrogen sulfide from water. Whereas ozonation is a water treatment process that destroys harmful bacteria and other microorganisms through an infusion of ozone.

Due to high electrical voltages, a gas, Ozone (O3) is produce.

Secondly, Ultraviolet radiation is a disinfection process that involves Ultraviolet (UV) light passing through waste water. UV light denatured microorganisms and can reduced dissolved organic material.

Lastly, Activated Carbon Absorption is a physical process that is applied as a tertiary treatment to remove low concentrated contaminants from water that are diffcult to be remove by other means. Activated carbon is then processed to make it extremely porous, which thus ceate a large surface are avaliable for absorption of contaminants. The actvated carbon may have a surface area of as large as 1500 m2/g (7.3 million ft2/lb)

An example will be the NEWater Treatment process whereby water is disinfected with Chlorine, Ozone and UV light to kill remaining pathogenic bacteria. In addition, NEWater is also prouced from treated used water that is purified further using advance membrance technologies, making the water ultra-clean and safe to drink,

https://www.youtube.com/watch?v=oaXth88i7rk

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https://www.youtube.com/watch?v=oaXth88i7rk

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