Actiflo® is ideal for drinking water and is particularly efficient in treating algal bloom, removing phosphorus and reducing the taste and odor associated with algae. There are more than 1,100 Actiflo references all over the world featuring more than 1,800 units, including more than 900 package plants, in municipal and industrial water and wastewater applications. The technology is also suitable for utility feed water, water reuse applications and to manage stormwater.

A range of products offering a high-rate and compact water clarification process for the production of drinking water, process water and the treatment and reuse of wastewater.


Water clarification is a fundamental step in water treatment to remove suspended solids from water and in wastewater treatment. 

Offering high-rate clarification, Actiflo is a family of products designed specifically for compact water and wastewater clarification processes. 

For the production of drinking water and process water, Actiflo treats surface water, groundwater, seawater and brackish water. This ability is vital as drinking water treatment plants adapt to the impacts of climate change such as storm events and the growing importance of alternative raw water sources.

To ensure water standards are maintained, Actiflo increases the settling speed compared to conventional settling and allows treating a flow rate up to 10 times higher than the sludge bed process. 

It is particularly effective in eliminating turbidity, natural organic matter, color and algae. For the specific needs of industry, Actiflo is also suitable for the treatment of cooling tower make-up water and boiler feed pretreatment.

For municipal and industrial wastewater, Actiflo can be implemented at all stages of the treatment of municipal effluents, including primary and secondary clarification, tertiary polishing and wastewater reuse. 

How does Actiflo work?

The high-rate clarification system is based on the ballasted flocculation concept developed by Veolia. It  uses microsand and polymer in the flocculation tank to increase the weight of the flocs and hence the water clarification velocity, reaching 40 to 100 times higher velocity than conventional clarification solutions.

It helps our customers across municipal and industrial markets such as pharmaceutical, food and beverage, power, mining, chemical and more, to treat toxins and remove organic matter, and is particularly suited to the removal of heavy metals, ash and coal fines, to ensure safe and compliant water supplies. 


Actiflo has been exclusively developed and patented by Veolia Water Technologies and has been in use for over 30 years. There are more than 1,100 Actiflo references all over the world featuring more than 1,800 units, including more than 900 package plants, in municipal and industrial water and wastewater applications.

Features and benefits

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Fast and flexible: compact high-rate clarification system for multiple applications in water and wastewater treatment plants


High-performance efficiency: turbidity and suspended solids (TSS) removal up to 99%; treats all water and wastewater sources. 

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Treat harmful toxins efficiently to ensure safe water supplies. 

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Extremely quick start-up time: reaches treatment efficiency within a few minutes. 

Process stability: capable of handling sudden variations in flow and load. 

Numerous standard options and alternatives to enhance performances and monitoring. 

Extremely compact footprint and start-up times account for savings in construction materials and water. 


Municipal drinking water systems and management of surface and ground water.
Technologies, services and process expertise to meet environmental requirements, remove contaminants and transform wastewater into a resource.
Optimized management of effluents and wastewater.
Solutions allowing the use of treated wastewater for beneficial purposes.
Solutions for the control, interception and clarification of stormwater


We offer a range of services from factory acceptance testing (FAT) on all manufactured products, to product commissioning support and best-in-class logistics services. We also provide: 

A combination of digital tools and Veolia expertise that make all your water processes smarter, safer and more sustainable.
Rental assets to support and assist your site operations for temporary and longer-term water treatment needs 24/7.
Providing water hygiene and HYDREXⓇ chemical solutions serving the performance of utility and water treatment equipment.

Resources & Product range


The principle of ballasted clarification has been known and used since the 1960s. The latest generation of high-speed clarifier based on this process is the Actiflo which combines the advantages of ballasted floc with those of lamellar decantation. The technology has become an essential tool in clarification with an inert chemical element that still offers continuous sludge discharge, safety and adaptability to incoming load variations.

Philippe Sauvignet picture

Philippe Sauvignet

Industrialization Manager

Contact Philippe through his LinkedIn account


FAQ about Actiflo®

How does clarification in water treatment using microsand work?

The key behind the physical-chemical ballasted flocculation process is the use of continuously recycled ballast or fine sand, which attaches to a flocculated particle through a polymer bridge. The addition of ballast provides two benefits: the high specific gravity sand weights flocculated particles, leading to much faster solids settling; and the increase in collision frequencies between sand and flocculated particles that dramatically increases flocculation kinetics, resulting in very short mixing times. In backwash recovery operations, this combination promotes well over 90% solids removal capability in a total process residence time of just under 15 minutes.

What are the benefits of microsand-enhanced clarification?

Operational stability with varying influent quality: the advantage of micro sand flocculation is that it can consistently produce high-quality clarified water under a variety of different treatment conditions. Actiflo offers stable performance and operating conditions even with large variations in raw water quality and/or difficult to treat water resources. These performance characteristics make this process an excellent choice for facilities subject to significant peaks in turbidity or seasonal changes in water quality.

What is ballasted flocculation?

Ballasted flocculation is a separation process commonly used to remove particulate matter in diverse water treatment applications such as drinking water, stormwater and industrial and municipal wastewater treatments. The process involves the injection of a ballasting agent, typically microsand (MS), during flocculation to increase the floc density and diameter. Organic polymers with high molecular weight and low charge density are normally used as bridging agents between the flocs and MS (Desjardins et al., 2001).

Case Studies

Calgary, Canada
Randy Reaman - Municipal

With an increased water demand due to population growth, coupled with the existing plant facing more stringent requirements and nearing its capacity, the City of Red Deer was planning a costly plant expansion. An additional clarifier and UV disinfection system was proposed to be installed in an expansion to the existing facility. An alternative solution was desperately needed. Actiflo was tested and selected due to its small footprint and performance at removing organic carbon. This was the only process that allowed a complete retrofit inside one of two existing contact clarifiers, while increasing the plant capacity by 80% (120,000 m3/d). And so a costly plant expansion was avoided. Since this date, Actiflo has also successfully managed storm events and flooding where Red River's flow rate went from a normal 150 cubic metre per second (cu.m/s) to 18,000 cu.m. These record turbidites were caused by river banks being literally washed away. However, Red Deer's drinking water quality remained unaffected.

United States
Coal Yard - Power

The client needed to manage stormwater runoff from a 37-acre coal storage yard utilized as a part of daily operations at an industrial site in Southwestern Pennsylvania following new NPDES permit discharge limitations for total suspended solids, iron and manganese. Actiflo provided the solution by utilizing sand-ballasted to treat water with changing flow rates within a small footprint, typically less than 10% of the area required for conventional settling technology. We combined the high-rate settling process with pH adjustment and chemical pretreatment to precipitate the metals of concern and produce an effluent of consistent, compliant quality.