Removing Hardness at the Source

April 3, 2018
Pilot test at Florida groundwater plant reveals parameters for water softening process

A pilot study was conducted to demonstrate the Actiflo Softening process in the removal of total hardness and alkalinity from the groundwater source of a treatment plant in Okeechobee, Fla. The facility, which has a capacity of 1 million gal per day (mgd), pumps water from shallow wells. Average daily production for potable drinking water is just over 2 mgd, with a maximum of over 3 mgd.

The Solution

The Actiflo process is a compact, high-rate, micro-sand ballasted clarification system capable of enhanced total hardness and alkalinity removal from drinking water. The process utilizes coagulant and polymer addition to remove pollutants from the water, and micro-sand to aid in rapid settling and clarification.

The Actiflo Softening process combines the clarification system with a Turbomix softening reaction tank to chemically optimize the removal of total hardness and alkalinity. Based on the project demands, the Actiflo Softening process was shown to be a suitable solution for the Okeechobee Utility Authority (OUA) groundwater plant.

Process Description

The purpose of the pilot study was to demonstrate Actiflo Softening’s ability to provide optimum clarified effluent for Okeechobee’s distribution systems and consistently maintain reduced effluent total hardness and alkalinity from the groundwater sources. In order to simulate different potential conditions, the Actiflo Softening process was operated using a variety of constituent levels and operational criteria. Standard runs using typical plant raw water were carried out to optimize chemical dosages. Chemical additions consisted of ferric chloride and calcium chloride coagulants, as well as Hydrex 3596 (dry, anionic) polymer. Clarified effluent samples were analyzed throughout the study for total hardness, alkalinity, turbidity, pH, temperature, UV-254 and color.


The Actiflo Softening process met the required effluent total hardness and alkalinity quality at the groundwater plant and demonstrated the ability to maintain performance over a period of time. Typical raw water total hardness and alkalinity concentrations were observed at 250 to 280 mg/L and 280 to 310 mg/L, respectively. The Actiflo Softening process was able to consistently achieve total hardness and alkalinity removal to 90 to 110 mg/L and 130 to 160 mg/L, respectively. Chemical doses were 7.0 mg/L ferric, 225 mg/L calcium chloride (for alkalinity reduction only) and 0.6 mg/L of polymer Hydrex 3596. The pilot also determined the optimal effluent pH range to be between 8.3 and 8.7.

Based on the pilot study data obtained on the OUA groundwater well, Kruger recommends using the above operating parameters to achieve desired effluent water qualities. The robust characteristics of the Actiflo Softening system allow for increased removal of total hardness and alkalinity to minimize scaling and corrosion. Furthermore, the ballasted flocculation system allows for high-rate treatment over a short period of time, minimizing the effects of variations in influent water quality.

Visit Kruger at WEFTEC booth 2048.

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