ACTIFLO®: Clarification for Drinking Water Treatment


The ACTIFLO® microsand ballasted clarification process from Kruger combines two proven principles of rapid settling: microsand enhanced floc formation and microsand enhanced settling. With over 260 surface water installations worldwide, the ACTIFLO® process can be found effectively treating low turbidity mountain runoff, reservoirs with algae, waters with high total organic carbon, hard water, soft water, ground water, flashy rivers and streams, brackish water and sea water.


Since its introduction in 1989, the ACTIFLO® process has been on the forefront of drinking water clarification. The ACTIFLO® process utilizes microsand as a seed for floc formation which later acts as a ballast or weight. The resulting sand ballasted floc displays unique settling characteristics, which allow for clarifier designs with high overflow rates and short retention times. These designs result in system footprints that are between 5 and 20 times smaller than conventional clarification systems of similar capacity.

With over 95 surface water clarification installations in the United States alone (as of August 2010) the ACTIFLO® process can be found clarifying all types and sizes of rivers, streams, reservoirs and ground water sources as well as brackish and sea water sources. The versatility of the ACTIFLO® process to treat cold clean water as well as water with high levels of organics, turbidity, color, algae, arsenic, viruses, iron and manganese has been proven over the past 20 years. Filtration steps following existing ACTIFLO® installations include mono/dual media filtration, pressure filters and membranes. The ACTIFLO® process has been shown to work effectively with a majority of the commercially available coagulants on the market today to include alum, ferric chloride, ferric sulfate, PACL, ACH and PASS.


The ACTIFLO® process is an effective and easy-to-operate system that combines standard coagulation chemistry with microsand enhanced flocculation and settling. The diagram to the right shows the typical ACTIFLO process flow path for drinking water treatment.

In a standard water clarification application a coagulant is added upstream prior to the water entering the first process tank. Particle stabilization and pin floc formation begins with the help of the coagulation tank mixer located in the coagulation tank. As the water enters the flocculation tank, microsand and polymer are added to begin the process of ballasted floc formation. With Turbomix™ mixing and flow control baffling the floc, microsand and polymer combine to form sturdy ballasted floc with high settling velocities. As the flow containing ballasted floc exits the flocculation tank the weight of the microsand causes the ballasted flocs to settle immediately upon entering the settling tank. The flow continues through lamella tubes and exits the process for further treatment. The material that settles in the settling tank is continuously withdrawn with the aid of a scraper mechanism and slurry pumps. The settled material is sent to the hydrocyclone where the microsand is separated from the sludge and re-injected into the flocculation tank of the process while the sludge is sent to the sludge handling system (sludge recirculation).