Wastewater treatment: what is the process?
How is wastewater treated?
To combat the ever-increasing costs of supplying and disposing of water, most commercial businesses are trying to treat and re-use wastewater.
By doing this, they are limiting these costs as well as managing strict regulations when it comes to discharging water. Additionally, if the water is cleaned to an acceptable level in the eyes of the industry, then this waste can actually provide your business with value.
How to treat wastewater
In the process of treating wastewater there are 3 main stages in the process: primary, secondary and tertiary. Here we will go into a bit more detail on the processes of each stage.
Primary wastewater treatment
This largely involves removing sediment from the water. Water is held in tanks that allow solid particles to settle, then they can be collected. Additionally, any oil or fat will float at the top, this is then scraped off. The remaining water is then moved onto the secondary stage.
In the meantime, the leftover sediment, and oils (also known as sludge) is removed to a different location and treated for alternate purposes. We will explain more about this later.
The two main methods used in the primary stage are Dissolved Air Floatation (DAF) and Volute Dewatering Press (VDP). DAP is used in the first part of the process to remove sediments and oils, then VDP is used in the latter half of the primary treatment in sludge removal. Both of these processes are used to remove and dispose of any contaminants that would impact industrial wastewater treatment systems in a negative way.
Secondary wastewater treatment.
Following the wastewater’s initial treatment, it is chemical treated. In this phase the goal is to break down the harmful particles into harmless ones. The chemicals typically used in this process are coagulants and flocculants and they aim to remove further solids by breaking them down.
Coagulants destabilise any remaining suspended particles, then the flocculants bind them to allow filtration out of the water.
This phase is vital, as much as 90% of suspended sediments are removed during this process. Since the strength of the wastewater has been significantly reduced, disposal costs at this stage are also lowered.
Tertiary wastewater treatment
Following the introduction of a chemical treatment to the wastewater, a tertiary phase is required for it to meet industry standards for discharge. This involves using a UV disinfectant and a chemical disinfectant.
The UV treatment aims to destroy any microorganisms in the water that could be harmful to us or other animals. Also, this treatment does not affect the taste, appearance or pH of the water making it safe for reuse. Following it’s UV treatment, the chemical treatment typically involves chlorine. The sole purpose of this treatment layer is disinfection.
After these treatments, the water is safe to be discharged into the environment or to be re-used.
What happens to the sludge?
At this stage your water is clean and safe for re-use, however you will still be left with the sludge from primary treatment. So, what happens to this…
Believe it or not, this material can be put to good use. Sludge can be transformed into energy in many ways. It typically is used for heat and power and can also be further cleaned to generate bio-methane and be returned into the power grid.
We hope this gives you a good overview of how to treat wastewater allowing it to be disposed of safely or re-used by your business.