Lime is an economical solution for a variety of water treatment applications. Taking advantage of the relatively high pH and alkalinity of lime can contribute to safer and cleaner water.
How is Lime Used in Water Treatment?
For decades lime products have become central to the design and operation of a wide variety of water treatment processes, including drinking water, wastewater, and sludge. Common water treatment applications include:
- Neutralize acidic wastewater
- Aid in the coagulation and removal of organics and pathogens
- Precipitate and remove constituents such as metals and various ions
- Prevent corrosion and leaching in water distribution piping
- Soften hard water sources at water treatment plants
- Stabilize biosolids produced from wastewater processes into sellable products
How Are Lime Products Prepared for Use?
For most drinking water and wastewater applications involving lime products, quicklime must first be converted to a slurry of calcium hydroxide in water. This resulting product is known as lime slurry, milk of lime, or by product brand names such as CALSAFE®.
Lime slurry is a suspension of calcium hydroxide solid particles floating in water and due to the low solubility of calcium hydroxide, only a small portion of it is dissolved at any given time in the slurry. However, as this dissolved material reacts with acids, metals and other constituents of the water, those dissolved materials are removed from solution and more solids are dissolved in their place.
Both quicklime and hydrated lime can be converted into slurry through specialized equipment systems. Quicklime is reacted with water in a device called a “Slaker” through a process called “slaking”. Slaking is an exothermic process meaning that heat is produced as the quicklime reacts with water and this heat must be managed by carefully controlling the ratios of water and lime, and any resulting steam and dust must be captured for safety and housekeeping concerns. For these reasons specialized slaking systems are used to control this process in a near fully automated way to produce lime slurry.
Hydrated lime is also mixed with water to produce lime slurry with several very similar characteristics as quicklime slurry, however the hydrated lime slurry process does not produce any significant heat and therefore the systems to control this process are simplified and the process is more straightforward.
STT’s Role in Water Treatment
Deciding between quicklime or hydrated lime for your process is a logical first step in water treatment. Quicklime is a less expensive reagent relative to hydrated lime on a weight/weight comparison. However, the capital costs of systems for hydrated lime are often less expensive than those for quicklime, though this paradigm does have some conditions in which there are exceptions. Whichever bulk material you choose, STT can create the system to meet your needs. And, STT is backed by Carmeuse, one of the world’s leading producers of lime.
STT is equipped to provide systems for the pneumatic conveying and storage of quicklime and hydrated lime. STT is also a global leader in the supply of lime slaking systems, which produce lime slurry from quicklime.
STT is an expert in the design, procurement, and installation of dry chemical systems. We deliver end-to-end lime handling systems: from truck unloading and material handling to the silo, and related silo safety and environmental systems. We are also a globally-recognized expert in the supply of lime slakers and auxiliary equipment, such as slurry holding tanks, de-gritting systems, and slaker control systems.
STT is backed by the experience of its parent company, Carmeuse, a global leader and expert in lime products and solutions. The Carmeuse team of specialists have over a century of combined industry experience in the optimized use of lime across a range of industry applications, including the supply of lime products for water treatment.
Our unique partnership delivers industry-leading lime products and lime handling systems, slaker selection, and system engineering and optimization. It’s a partnership that has proven itself over many years as one of the biggest producers of lime products in North America, where STT and Carmeuse are the largest suppliers of slaking systems and quicklime.