By Nick Nicholas
Hardness in water can be characterized into its primary constituent mineral components, typically calcium and magnesium. Excess water hardness in a water supply creates many issues for industry, utilities, and life in general.
Calcium and magnesium which are the principal sources of this issue are found in many sedimentary rocks, the common being chalk and limestone, which are abundant in many areas of the U.S. and across the world.
The World Health Organization (WHO) recommends that drinking water hardness is to be below 500 mg/L calcium carbonate; however, in most industrial applications this criteria is a lot lower to protect from any damage that can occur to process systems and machinery.
There are several different technologies used for water softening, including ion exchange, chemical precipitation, membrane filtration, evaporation, and electrocoagulation. Each approach has its own set of advantages and disadvantages.
I will be focusing on the electrocoagulation treatment method for the reduction of hardness in a water supply.
Firstly, I will provide a brief description of the electrocoagulation process. This method was developed utilizing electrochemistry to overcome some of the drawbacks of conventional treatment technologies. It uses electricity to effectively reduce and remove multiple contaminants from a water or wastewater source. Electrocoagulation is an advanced yet reliable and cost-efficient process harnessing the conductivity of the water source along with a direct electrical current between metal electrodes to create chemical reactions to remediate the water source.
Advantages of electrocoagulation:
- Does not increase TDS levels
- Does not affect permanent hardness
- Reduced sludge concentration with easier sludge dewaterability
- Is not prone to fouling
Application Case Study (Industrial Process Water – Food/Beverage Industry)
A mid-size dairy company wanted to reduce water hardness among other parameters in their surface water source prior to reverse osmosis (RO) membrane treatment for their ingredient process water requirements.
There additional request was to reduce OPEX by at least 20% over the conventional chemical treatment solutions currently employed in their production makeup water process.
Genesis Water Technologies, in association with its local partner, provided process consulting/design as well as the treatability testing for the planned full-scale implementation. The system included specialized electrochemical treatment, post-clarification, followed by post-polishing filtration using Natzeo and carbon media. This shall be accomplished via a continuous batch process.
The treatability results are indicated below (optimal removal percentage efficiency), in which the full-scale system will be implemented.
Pollutant Removal Reduction %
- Hardness: 92%
- Calcium 92 %
- Magnesium 93 %
- Turbidity 95 %
- Nitrate – 50 %
- TDS – 23 %
Operating Time: 60 min.
Capital cost and operation cost shall be optimized based on adjustment of conductivity of the raw source water.
The sludge production was minimized with a higher solids content that was easy to dewater, thereby reducing associated disposal costs for this food/beverage client’s operations.
The implementation of this system will provide treated water within the water quality parameters set by the client’s regulatory guidelines to allow sustainable utilization of the RO system for the provision of ingredient makeup water for production.
This will assist this food/beverage client to reduce their environmental impact and associated operating cost of the RO membrane treatment system by around 20%.