Wastewater treatment process description

Wastewater Treatment Plant

Wastewater treatment plant (WWTP) are facilities created to remove contaminants from effluents. These facilities can be found in industrial plants, treating the industrial wastewater generated in the production process, or they can be found as part of the municipal wastewater treatment process attending to the sewage produced in water, commerce and small businesses.

As water is channeled through pipes and sewer systems and finally pumped into the wastewater treatment plant, they are submitted to physical and chemical treatments in order to reduce the presence of contaminants and debris that could be harmful for the environment. WWTPs can present slight variations to address specific issues found in certain effluents. However, the system is most commonly composed of:

a preliminary treatment, where the use of grades, coarse and fine screens is seen to remove objects that are found in the effluent.

The primary treatment, leading the effluent to tanks that allow for initial sedimentation of grit. By applying slow mixers at the top of the tanks, sediments are separated by gravity and sink to the bottom of the settling basins. The effluent is then filtrated to also remove debris that have floated in the tanks.

The secondary treatment, also known as the biological stage, uses the presence of bacteria to consume the organic compounds, phosphorous and carbon present in the effluent. With time, they form the sludge that is treated separately.

The disinfection step, which applies the use of ozone, chlorine or hypochlorite to the water killing bacteria and pathogens.

Finally, the polishing process starts, where the water is chemically adjusted for proper discharge into the environment, reducing chemicals still present and adjusting pH to ensure environmental safety.

Depending on regulation and technologies, these treatment plants may vary from one location to another due to climate and contamination levels.