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Activated sludge for wastewater treatment

On this page, you’ll read more about the activated sludge process in wastewater treatment. and discover which of our two systems based on activated sludge are most cost-effective for your facility.

Activated sludge for wastewater treatment

To meet requirements for surface water discharge, primary treatment for solids removal and anaerobic treatment of wastewater are usually followed by aerobic treatment. The activated sludge process consists of an aeration stage - and an anoxic/oxic compartment if nitrogen has to be removed - and secondary sedimentation with sludge return. Systems for activated sludge are based on high quality surface aeration, fine bubble aeration or jet aeration. After the second part of the activated sludge process, further treatment can consist of filtration, denitrification or effluent softening.

Activated sludge for high quality water output

CIRCOX®, the fully-closed aerobic system of Paques uses granular aerobic sludge for deep removal of COD, ammonia and sulfides. The biofilm on the carrier allows microorganisms to slowly grow in high concentrations. This granular sludge is kept in suspension by means of airlifts. This granular aerobic sludge has a high density and excellent settling properties. The granules are retained by a tilted plate settler on top of the reactor.

The volumetric loading rates of CIRCOX® are five times higher than conventional systems. It also requires little space. That’s why CIRCOX® bioreactors with granular activated sludge are very suitable for aerobic polishing of anaerobic effluent in urban areas.

The activated sludge process in BIOPAQ®UBOX

The BIOPAQ®UBOX offers highly efficient sewage treatment. It combines anaerobic treatment, aerobic treatment and biogas purification. This leads to low operational costs, a small footprint and zero odor emission. The system treats sewage in four steps: anaerobic treatment, supplementary aerobic treatment using the activated sludge process, secondary clarification and biogas purification. The {BIOPAQ®UBOX](https://www.paquesglobal.com/products/biopaq-ubox) is equipped with an exclusive anti-clogging pressurized feeding system. This ensures uniform distribution and avoids thickening of the active sludge.

The BIOPAQ®UBOX modular design is suitable for capacities of 5, 10, 15, 20, 30 and 40 thousand population equivalent (PE). By combining these different modules it is possible to treat larger PE’s. Since implementation in progressive steps is an option, idle capacity is avoided.

Find out if BIOPAQ®UBOX is the most cost-effective solution for your facility


At Paques, we believe in a cleaner, more sustainable world where innovation in biotechnology plays a crucial role in managing our planet's resources wisely.

If you have any questions or wish to explore what Paques technologies can do for your operations, we encourage you to connect with our team of experts. Our knowledgeable professionals are ready to assist you, offering insights and guidance tailored to your specific needs.

Leading the biotech revolution in wastewater and biogas

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The Paques Team