Anaerobic reactor, the optimal solution for water with high COD

The anaerobic reactor has emerged as a revolutionary piece of equipment in wastewater treatment, its potential increasing when used in conjunction with an aerobic reactor. By combining both systems, high COD (Chemical Oxygen Demand) loads and large flow rates can be successfully treated . But why is this technology gaining so much traction?

In this type of biological reactor, the bacteria present are able to break down organic matter (COD) without the presence of oxygen. As a result, a biogas stream is produced that can generate energy.

Anaerobic biological reactors have great potential in wastewater treatment; they make it possible to valorize the organic matter present in wastewater and achieve maximum efficiency and sustainability in industrial water management.

These types of reactors are based on anaerobic technology , which consists of two types of equipment: anaerobic reactors and anaerobic digesters . The former, as mentioned earlier, is used for wastewater treatment, while the digester is used for waste treatment, such as sludge. In both cases, this equipment allows for maximizing the potential of organic waste by extracting biogas and, in the case of digesters, digestate. This digestate can then be used as fertilizer, thanks to anaerobic digestion.

Why opt for an anaerobic biological treatment?

 Among the most important advantages of anaerobic biological treatment, we find the following:

• Reduce operating expenses: It does not require aeration to function properly, needs fewer nutrients, and generates less sludge than aerobic digestion. This results in lower operating costs. In short, it achieves Reduce OPEX costs: energy expenses (savings of up to 70%), expenses for reagents and sludge management and treatment.
• Lower nutrient costs: Specifically, it needs 5 times fewer nutrients than an aerobic system.
• Less sludge generated: Regarding sludge, it produces up to 8 times less sludge than the other treatment.
• Low space requirements: It usually occupies less space than aerobic systems, with the resulting cost reductions.
• Potential uses of the biogas produced: During the anaerobic reaction, biogas is generated that can be used to heat the water entering the reactor, as the reaction occurs within a specific temperature range. Heating the influent is not always necessary, but in cases where it is required, the biogas helps reduce operating expenses (OPEX).
• Good resistance to variable input: It maintains proper functioning under changes in load and concentration within certain limits.
• Anaerobic sludge can remain inactive: Anaerobic sludge can be preserved (inactive) for many months without serious deterioration; this is ideal when it is intended for use in seasonal discharges.
• It is capable of treating very high COD loads When dealing with influents with high loads, an aerobic reactor would need to be very large to adequately manage the flow. This increased size would significantly raise operating expenses (OPEX) due to the costs of aeration and sludge management.

As we have indicated before, having aerobic and anaerobic technology combined helps to obtain good results in waters with high COD load and large flow rates, thanks to the fact that anaerobic biological treatment compensates for some of the limitations of aerobic treatment.

Limitsaerobic reactor emissions compensated thanks to the anaerobic reactor

As mentioned earlier, the aerobic reactor requires aeration to function correctly , as its bacteria need oxygen to break down the organic load. These aerators require large amounts of energy to deliver air to the bacteria and enable the reaction to occur, thus increasing operating costs.

In the anaerobic reactor, since the reaction occurs in the absence of oxygen, these costs are not a factor. In addition to the expense of running the aerators, the aerobic reactor produces a large amount of sludge during its reaction, which then requires proper management, increasing operating expenses (OPEX). Combining both technologies significantly reduces sludge generation.

Ideal industries for the anaerobic reactor

In industries with high COD (Chemical Oxygen Demand) levels in their wastewater, anaerobic sludge blanket (ASB) reactors become the solution for achieving acceptable discharge parameters. These industries are typically those in the food and beverage sector , such as wineries, breweries, and fruit and juice factories—in short, those that work with products of plant and/or animal origin.