Industrial wastewater treatment process

All contaminants in the wastewater are removed through a system of biological and chemical processes. These processes produce clean and treated water.

How do Wastewater Treatment Plants work?

During the industrial wastewater treatment process, sewage from household and industrial waste and wastewater from natural sources is collected to be treated at a wastewater treatment plant. All contaminants in the wastewater are removed through a system of biological and chemical processes. These processes produce clean and treated water.

The primary steps of the Wastewater Treatment Process:

• Screening
• Coagulation
• Sedimentation
• Filtration
• Disinfection

Each step in the wastewater treatment process is explained in more detail below. Screening Screening is a preliminary process of wastewater treatment consisting of five steps:

1. Screening – during the screening process, large solid objects are removed from the wastewater through screens. Coarse screens contain small openings to stop larger objects escaping. The wastewater will then pass through a fine screen to remove smaller objects from the water before it moves to the next stage in the wastewater treatment process.
2. Grit removal – this is an optional step in the screening process and is designed to remove much smaller objects such as silt, sand or grit from the water. Velocity control, air lift or pump removal are some of the methods used in this step.
3. Septage management – wastewater flows through a septic tank to remove any remaining solids, oils, and grease. The septic tank is designed to still the water so that the deposits sink to the bottom of the tank and grease and oil rises to the top. The sludge and scum are then effectively removed from the wastewater.
4. Odor control – biological or chemical treatments are used to disinfect the wastewater. Then, hydrogen sulfide and other gases are released by decaying sewage deposits - chemical treatments are used to reduce foul odors by a process of oxidation.
5. Flow equalization – this is the method of controlling the rate that wastewater flows through the treatment system. Flow equalization is used to prevent surges in flow which can cause problems during the screening process.

Coagulation During the coagulation flocculation process, wastewater is treated with chemicals to reduce the amount of turbidity or murkiness from the water.  This stage helps to improve the odor and taste of the water and allows water to be disinfected at a higher rate. A coagulant, often aluminum sulfate, is added to the wastewater to bring smaller particles together to produce larger and denser particles called floc.

Sedimentation In the sedimentation process, gravity allows heavier particles (created in the coagulation flocculation stage) to settle to the bottom of the sedimentation basin so that they are easier to remove. Water passes through slowly, allowing enough time for the floc to settle and settle at the bottom of the basin for easy removal. The clear water above it can pass through to the filtration stage.

Filtration  During the filtration process, any remaining particles or unwanted organic matter from wastewater are removed. This stage is carried out by passing the water through fine, sand-like material or carbon granules. The carbon traps the unwanted matter so that only clean water passes through.

Disinfection The final stage in the industrial wastewater treatment process is disinfection. This process uses a chemical treatment (such as chlorine) to ensure that any harmful bacteria still present in the water is removed. The water comes in to contact with chlorine for a period of time before it moves on. The pH value is balanced so that the water is not acidic or alkaline, and only neutral, clean and disinfected water flows into the mains water system ready to be accessed as usable drinking water.

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