What type of system is primarily used for anaerobic treatment of wastewater?

The anaerobic digester is specifically designed for the anaerobic treatment of wastewater, which is a process that occurs in the absence of oxygen. In this system, microorganisms break down organic material in the wastewater, leading to the production of biogas, primarily methane and carbon dioxide, along with reducing the volume of sludge. This process is crucial as it not only helps in treating the wastewater but also generates renewable energy in the form of biogas, which can be used for heating or electricity generation.

Anaerobic digesters are particularly effective for high-strength organic waste, such as sludge from primary treatment and food waste. They provide an optimal environment for anaerobic bacteria to thrive, allowing for efficient digestion over a sustained period.

The other systems listed serve different purposes. Aerobic digesters rely on oxygen to support the growth of bacteria that decompose organic substances, while activated sludge reactors use a mixed population of microorganisms but operate under aerated conditions. Batch reactors are not exclusive to either aerobic or anaerobic processes, making them versatile but not primarily designed for anaerobic treatment. Thus, the anaerobic digester stands out as the dedicated system for anaerobic treatment of wastewater.