Introduction

Waste water treatment plants are facilities designed to remove pollutants from waste water before it is discharged into natural waters. The treatment process involves multiple steps to ensure that the water is safe for the environment and human consumption. In this article, we will explore what waste water treatment plants remove.

Solids Removal

The first step in waste water treatment is solids removal. This process involves the use of a primary clarifier where heavy solids settle to the bottom and are removed as sludge. The remaining water is then passed through a secondary clarifier where finer solids settle and are removed. Solids removal is important as it reduces the amount of pollutants in the water and prepares it for further treatment.

Biochemical Oxygen Demand (BOD) Reduction

Biochemical Oxygen Demand (BOD) refers to the amount of oxygen consumed by microorganisms breaking down organic matter in the water. High BOD levels can deplete oxygen levels in natural waters, leading to fish kills and other ecological problems. To reduce BOD levels, waste water treatment plants use aeration tanks where microorganisms are provided with oxygen and nutrients to break down organic matter. The water is then passed through a secondary clarifier to remove the microorganisms and any remaining solids.

Nutrient Removal

Nutrients such as nitrogen and phosphorus can cause excessive plant growth and eutrophication if not removed from waste water. Eutrophication is the process of water bodies becoming choked with plants and algae, leading to low oxygen levels and unhealthy aquatic ecosystems. To remove nutrients, waste water treatment plants use a variety of methods including biological nutrient removal, chemical precipitation, and physical separation. These methods reduce the amount of nutrients in the water, improving its quality and reducing its impact on the environment.

Disinfection

The final step in waste water treatment is disinfection. Disinfection is necessary to remove any remaining pathogens in the water before it is discharged into natural waters. The most common disinfection method is chlorination, where chlorine is added to the water to kill any remaining bacteria or viruses. Alternative disinfection methods such as ultraviolet light and ozone are also available and are becoming more popular due to concerns regarding the use of chlorine.

Conclusion

Waste water treatment plants remove a variety of pollutants from waste water to ensure that the water is safe for the environment and human consumption. The treatment process involves multiple steps including solids removal, BOD reduction, nutrient removal, and disinfection. By removing pollutants from waste water, waste water treatment plants reduce the impact of human activities on natural waters and help to ensure a healthy and sustainable environment.