About AquaFLOC Packaged Conventional Water Plants

FilterTECH’s AquaFLOC Package Conventional Water Plants are complete water treatment plants reliably proven to effectively treat incoming water at levels up to and over 500 NTU, designed to deliver a treated water effluent of less than 0.01 NTU. Using a traditional and accepted five-step treatment process, three treatment stages are incorporated into a single marine-grade aluminum vessel, delivered to the job site and easily installed, all at a reasonable cost. The three process stages within the aluminum module are Flocculation, Sedimentation, and Filtration. Single-train AquaFLOC Package Treatment Plants are custom designed to treat flows from 20 GPM to over 1 MGD. Multiple trains can be provided to operate in parallel for greater flow ranges, and in series for system redundancy.

Because good chemical mixing is an important accompanying step to the three-stage treatment process, the FilterTECH AquaMIX in-line Mechanical Flash Mixer is often used as a treatment step prior to flocculation. This stand-alone piece of mixing equipment is not located inside the aluminum vessel, but it ensures good coagulation of particles before the water enters the treatment module. Once inside the vessel, the raw water containing well-mixed coagulant meets our custom vertical paddlewheel mixers designed to impart the correct “G” values in several different basins. Next, our settling basins, integrated into the aluminum module, remove the majority of the flocculated particulates so that any remaining material is easily captured in the filtration area, which is the final step within the vessel. Our AquaFLOC design uses concurrent air-and-water backwash to minimize backwash water use and the energy required for proper filter backwash.

The final step in the traditional five-step process is disinfection, and all of the steps can be automatically controlled using our  AquaTRAC Control System. This system provides operators with a simple yet robust platform for remote and local observation and control of the plant’s operating functions. The entire treatment system is customized for each project’s flow rate, site requirements, and individual project needs.

  • AquaFLOC Package Treatment plants

  • Package Treatment Plants for Surface Water, Tertiary Treatment and Re-Use Applications


The 5 Step AquaFLOC Treatment Process

The AquaFLOC process is a chemical operation, using gravity settling and filtration, typically applied to the removal of turbidity and suspended matter from surface water sources or from underground sources directly influenced by surface water. The AquaFLOC Complete Treatment System consists of five distinct treatment steps – Coagulation, Flocculation, Sedimentation, Filtration, and Disinfection. With proper operation, the AquaFLOC process will consistently produce water with a turbidity of less than 0.01 NTU, even with incoming water turbidity above 500 NTU, or as low as 1 NTU.

Surface water contains two basic sources of turbidity: suspended solids and colloidal solids. Suspended solids settle easily, often within minutes. But colloidal material, as small as 0.1 micron, tends to remain suspended in the water, sometimes taking over 2 years to descend one meter in the water. The AquaFLOC process is designed to accelerate the settling of colloidal material to less than one hour.

Below is more information about each of the 5 treatment steps. 


The first step of the treatment process is coagulation – the addition of cationic chemicals to the raw water. The purpose of coagulation is to neutralize the particle charges in the water. Particles that carry the same charge have a tendency to repel each other. When the particles are negatively charged, a positive or cationic chemical is added.

Coagulation is actually a three-step process. First, there is the rapid mixing of the chemicals with the raw water. This is accomplished with the AquaMIX Mechanical In-Line Flash Mixer. The mixer provides energy for instantaneous dispersion of the chemicals. Second, the cationic coagulant chemicals come in contact with negatively-charged particles in the water and form new molecules with a neutralized charge. The third function of the flash mixer is to provide energy and movement of the neutralized particles to cause collisions between the particles. These collisions are the start of the flocculation process.


The second step is flocculation – the process of floc formation. The flocculation process creates a large or dense particle that will settle rapidly in the third step of the process. The flocculation compartment provides ample time and mixing energy for the completion of the chemical reaction and the formation of a settle-able floc.

Floc consists of particles containing the aluminum-based coagulant and particulate matter in water. Floc particles are formed during particle collisions in the water. The mixing energy to encourage these collisions is provided by vertical-paddle variable speed mechanical flocculators or velocity driven hydraulic mixing ports. The “g” value, or energy imparted to the water ranges from 10 to 100 sec-1.


Once a settle-able floc has formed, the water is transferred to the settling basin for the third step of the process. The settling basin consists of a large open area at the bottom with tube settlers covering the area of the basin.

Tube Settlers are a settling enhancement that work by reducing the amount of distance a particle must fall to settle. Rather than waiting for the particles to settle to the bottom of the depth of the basin, the tube settlers are 2” square tubes inclined at 60o . The particle merely has to travel a distance equal to the sine of 60 o before it reaches the tube settler surface. The tube settlers are self-cleaning. As the settled particles increase in mass, they have a tendency to naturally slough off and fall to the bottom of the basin.

After the clarified water rises out of the tube settlers, it overflows across v-notch weirs into the collection troughs which deliver the water to the filter compartment.

The sludge that accumulates in the bottom of the settling basin must be removed. The AquaFLO sludge draw off system periodically draws the sludge through a header/lateral system located at the floor of the basin. This system is an automatic, continuous operation used on plants larger than 300 gpm capacity.

The AquaJET hydraulically assisted sludge removal system provides spray nozzles to remove the sludge after the basin is drained. This system is incorporated into the smaller plants. The frequency of the sludge removal ranges from monthly to annually.

The sedimentation compartment in the AquaFLOC Complete Treatment System reduces the amount of floc that ends up on the filters. This leads to longer filter runs and shorter backwash cycles saving both money (chemicals) and electricity.


The settled water is directed to the fourth step of the process – filtration. The water flows by gravity through a multi-media filter bed. The filter bed consists of anthracite, silica sand and high-density garnet sand. The anthracite provides full depth filtration to pre-filter large particulate matter before it reaches the layer of sand.

Because untreated colloidal material is small enough to pass through the filter, the previous steps of coagulation, flocculation and sedimentation are key to achieving a high quality filter effluent.

As the particulate matter builds up in the filter bed, the differential pressure across the media begins to rise. When this reaches a pre-determined level, the filter must be backwashed to remove the particulate matter that has been filtered out.

During the backwash process, water is introduced through the effluent pipe and underdrain system and flows upward through the media. The backwash water is removed from the filter through collection troughs and discharged to waste.

The backwash cycle is enhanced with by backwashing with a combination of air and water. This AquaAir concurrent air/water backwash reduces the amount of water required for backwash by over 33% when compared with conventional backwash with surface wash. The bed is significantly cleaner resulting in shorter backwash cycles and longer filter runs. A separate grid is used for air distribution. This allows for more even distribution and a lower volume of air.


The last step of the conventional filtration process is disinfection. After the water has been filtered, a disinfection agent is injected into the effluent pipe. This disinfection step is important for the destruction of water-borne pathogens and the inactivation of any cryptosporidium spores that may have passed through the filter.

An optional pre-chlorination injection point is provided at the flash mixer. However, an analysis of organic levels must be reviewed to determine the extent of the formation of disinfection byproducts.


The AquaCLEAR Package Treatment System uses a subset of the complete AquaFLOC 5-step treatment process. It can be applied in instances where raw water quality is such that regulatory agencies have mandated the use of chemical coagulation and flocculation, but have determined the settling step is not necessary. AquaCLEAR makes use of either hydraulic or mechanical flocculation, followed by filtration, in a single unit to deliver an efficient and economical treatment system when settling is not required. These systems are custom designed for each individual project, and typically include our AquaTRAC Control System. AquaCLEAR can also be applied to Phosphorous Removal in certain wastewater effluents.


The AquaPRIMA Package Treatment System provides a subset of the complete AquaFLOC 5-step treatment process. It incorporates coagulation, flocculation, and sedimentation, but does not include the filtration step. This is an excellent pre-treatment module for use with our UltraFLEX Membrane Filter System, or in plants where a filtration process is already in place, but better pre-filtration steps are needed for optimal plant performance. Good pre-treatment can significantly lower both capital and operating costs of filtration. And, as potable water regulations tighten and good raw water sources become harder to find, many filtration plants without good pretreatment are discovering the value of incorporating an AquaPRIMA System into their treatment steps.