Water Hardness Scale and Its Industrial Impact
Water is a universal solvent, but with that power comes a downside. As it flows through soil and rock, it dissolves small amounts of minerals, mainly calcium and magnesium. The higher the concentration of these minerals, the “harder” the water becomes. While hard water may not be harmful to human health, it can be a serious challenge for industries, impacting equipment, processes, and output quality.
To evaluate and manage water quality, it’s crucial to understand the water hardness scale, how it’s measured, and what implications it holds for industrial operations.
What Is Water Hardness?
Water hardness refers to the concentration of dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions in water. The presence of these minerals affects how water interacts with soaps, detergents, boilers, cooling towers, and other process equipment.
There are two types of hardness:
- Temporary hardness – Caused by dissolved bicarbonate minerals and can be removed by boiling.
- Permanent hardness – Caused by sulfates and chlorides of calcium and magnesium; cannot be removed by boiling.
Understanding the Water Hardness Scale
To quantify how “hard” water is, we refer to the water hardness scale. This scale is typically expressed in terms of parts per million (ppm), milligrams per liter (mg/L), or grains per gallon (gpg). Since various industries and geographies use different units, understanding water hardness scale conversion becomes important.
Here’s a standard classification of water based on hardness:
| Water Hardness Level | ppm (mg/L) | gpg | Classification |
| 0 – 17.1 | 0 – 17.1 | 0 – 1 | Soft |
| 17.1 – 60 | 17.1 – 60 | 1 – 3.5 | Slightly hard |
| 60 – 120 | 60 – 120 | 3.5 – 7.0 | Moderately hard |
| 120 – 180 | 120 – 180 | 7.0 – 10.5 | Hard |
| 180+ | 180+ | 10.5+ | Very hard |
This water hardness scale in ppm is widely used in laboratory and industrial testing. It allows users to benchmark raw water quality and select appropriate treatment technologies.
Water Hardness Scale Conversion
Depending on where you’re operating, you might need to convert water hardness between different units. Here’s a quick hardness water scale conversion reference:
- 1 gpg = 17.1 ppm (mg/L)
- 1 ppm = 0.0584 gpg
- 1 mmol/L = 100.09 ppm (as CaCO₃)
For industries operating in multiple regions or sourcing water from different supplies, knowing these conversions is vital for consistency in treatment and reporting.
Why Does Water Hardness Matter to Industries?
The impact of water hardness extends far beyond domestic inconvenience. In industrial settings, hard water can wreak havoc on machinery, reduce energy efficiency, and contaminate products.
1. Scaling and Fouling of Equipment
Hard water leads to scale formation in boilers, cooling towers, heat exchangers, and pipelines. This scale acts as an insulating layer, reducing heat transfer efficiency and increasing fuel consumption. Left untreated, scale buildup can cause blockages, overheating, and equipment failure.
2. Reduced Equipment Lifespan
Calcium and magnesium deposits corrode metal surfaces, reduce flow capacity, and lead to frequent maintenance shutdowns. This shortens the operational life of critical assets.
3. Inconsistent Product Quality
In industries like pharmaceuticals, textiles, and food processing, hard water affects product quality. For instance, in textiles, it causes uneven dyeing; in food processing, it alters taste and shelf life.
4. Increased Chemical Use
Hard water reduces the effectiveness of soaps, detergents, and cleaning agents, leading to higher chemical consumption and associated costs.
Industries Most Affected by Hard Water
• Power Generation
Boiler feed water must meet strict quality standards. Even slight hardness can cause scale, reduce thermal efficiency, and pose safety risks.
• Textiles & Dyeing
Hardness affects dye absorption and finish quality. It may also interfere with process chemicals.
• Food & Beverage
Impacts taste, microbial safety, and the cleanliness of processing equipment.
• Pharmaceuticals
Hard water can contaminate formulations and reduce equipment sterility.
• Automotive & Metal Processing
Affects surface treatment processes, paint adherence, and cooling operations.
Ion Exchange: Elevating Water Quality Standards Globally
INDION Lampak, developed by Ion Exchange, is a compact and modular unit tailored to meet the drinking water demands of communities and industrial applications. It combines a pump, static mixer, flocculation, lamella clarifier, gravity sand filter, and chemical dosing systems to produce disinfected water with less than 5 mg/l TSS from feed water containing up to 500 mg/l TSS. Easy to operate and low-maintenance, INDION Lampak can be powered by a diesel generator or renewable energy, making it ideal for regions without electricity. Its lightweight, corrosion-resistant materials and space-efficient design ensure easy transport, operation, and upkeep.
INDION NGIRF is an advanced solution for removing dissolved iron, typically found as ferrous bicarbonate in groundwater. Utilizing a catalytic oxidation process, this filter efficiently reduces iron levels to below 0.3 ppm without the need for chemicals. Designed with convenience in mind, it features a corrosion-resistant Fiber Reinforced Plastic (FRP) pressure vessel and PVC pipes. Pre-assembled and tested, the NGIRF comes equipped with user-friendly valves, offering a reliable and easy-to-operate solution for treating water with high iron content.
- INDION Water Potability Test Kit
INDION Water Potability Test Kit is a versatile tool designed to measure eight essential chemical parameters of drinking water as per the Bureau of Indian Standards. Providing quick and accurate results for pH, total hardness, alkalinity, chloride, fluoride, chlorine, iron, and nitrate, this kit is user-friendly and ideal for semi-skilled individuals, offering an affordable way to ensure safe drinking water.
INDION Packaged Sewage Treatment Plants offer decentralized sewage treatment in a compact, single-tank design that produces low sludge volumes and requires minimal electricity, making them highly cost-effective. Available in capacities ranging from 10 to 100 m³/d, these systems are ideal for smaller needs, while advanced options like Fluidized Media Reactor (FMR), Moving Bed Biofilm Reactor (MBBR), and Membrane Bio-Reactor (MBR) processes are available for efficiently handling higher flow rates in larger applications.
Conclusion
Understanding the water hardness scale is more than just a matter of measurement — it’s a gateway to efficient industrial operations. Whether you’re looking at water hardness scale ppm, gpg, or mmol/L, interpreting it correctly and managing its implications can lead to major savings, increased uptime, and consistent product quality. Industrial water users cannot afford to ignore the hardness water scale — it’s a key parameter in both performance and profitability.
