Lime Slurry for Industrial Wastewater Treatment
Calcium hydroxide, supplied as lime slurry, is one of the most widely used alkaline reagents in industrial wastewater pretreatment. Its chemistry is well understood, its cost is competitive with caustic alternatives, and its capacity to precipitate heavy metals, neutralize acidic waste streams, and drive pH into compliance ranges makes it a practical choice for a broad range of treatment applications. OVIVO ALAR supplies lime slurry to industrial facilities operating wastewater treatment systems, including those looking to establish a reliable chemical program or transition away from a current supplier.
What Is Lime Slurry for Water Treatment?
OVIVO ALAR lime slurry is an aqueous suspension of calcium hydroxide (Ca(OH)₂). When introduced into a wastewater stream, the calcium hydroxide dissociates to release hydroxide ions, raising pH and driving precipitation reactions. The divalent nature of Ca(OH)₂ provides two hydroxide ions per mole of compound, compared to one for monovalent caustic soda (NaOH). This higher molar neutralizing capacity translates to lower reagent consumption on a per-mole basis, particularly in high-volume applications.
How Lime Slurry Functions in Wastewater Treatment
The primary treatment functions of lime slurry wastewater treatment include:
- pH adjustment and neutralization of acidic waste streams to meet discharge compliance thresholds
- Heavy metals precipitation, including copper, zinc, chromium, iron, lead, nickel, and cadmium, which form insoluble metal hydroxides at elevated pH and can then be captured by downstream mechanical separation
- TSS reduction in conjunction with coagulant and flocculant programs, where precipitated solids are conditioned for filtration or dewatering
- Sludge stabilization as part of a broader solids management program
Because calcium salts are largely insoluble, the sludge produced by lime-based precipitation is typically denser than that generated by caustic-based treatment. This characteristic improves downstream dewatering performance and reduces the volume of material requiring disposal.
Lime Slurry vs. Caustic Soda: A Practical Comparison
Many facilities operating pH-neutralization and metals precipitation systems use caustic soda (NaOH) as their primary alkali. Lime slurry water treatment offers a cost-effective alternative for facilities processing significant wastewater volumes or targeting metals removal as a primary treatment objective.
Caustic soda is easier to handle and dose in low-volume applications, but its monovalent chemistry means higher per-unit alkalinity cost at scale. Lime slurry requires more attention to feed system design, including continuous agitation to prevent solids settling, recirculation loops to minimize pipe scaling, and appropriate pump and valve selection for abrasive service. For facilities already equipped to handle slurry chemistry, or those willing to configure their feed system accordingly, lime is frequently the more economical and technically effective option where metals precipitation is the goal.
Industries That Rely on Lime Slurry Wastewater Treatment
Lime slurry is a foundational treatment chemical across a range of regulated industries. The following sectors represent common applications where calcium hydroxide plays a central role in achieving discharge compliance.
Metal Finishing
Rinse water and process baths from plating, anodizing, and surface-finishing operations typically carry dissolved heavy metals at concentrations far above permit limits. Lime slurry raises pH into the precipitation range, converting soluble metal ions into insoluble hydroxides that can be captured by filtration or clarification. It's even recognized by the EPA as a suitable treatment method for metals stabilization under land disposal restriction regulations.
Food and Beverage
Processing wastewater from food and beverage facilities is often high in BOD, FOG, and suspended solids, with pH that fluctuates significantly depending on cleaning cycles and process chemistry. Lime slurry neutralizes acidic wastewater, aids in solids coagulation, and supports clarification ahead of biological treatment or direct discharge.
Pulp and Paper
Pulp and paper operations generate large volumes of process wastewater containing fiber solids, color compounds, and acidic or alkaline streams, depending on the production stage. Lime is used for pH neutralization, color precipitation, and alkalinity control across both process water and final effluent treatment stages.
Chemical Manufacturing
Chemical production facilities frequently discharge complex wastewater containing acids, dissolved metals, and reactive compounds requiring neutralization before entering a POTW or receiving water. Lime slurry provides a cost-effective alkali source for high-volume neutralization programs and is compatible with a wide range of pretreatment chemistries used in this sector.
Compatibility With OVIVO ALAR Equipment
Lime slurry is designed to integrate directly with OVIVO ALAR chemical pretreatment systems, including the Flex-O-Star and pH neutralization equipment. Facilities using OVIVO ALAR hardware benefit from chemical and equipment programs developed in coordination, with dosing parameters informed by bench and pilot testing on the actual waste stream rather than generalized assumptions.
For facilities not using OVIVO ALAR equipment, the chemical is available as a standalone supply. OVIVO ALAR can provide guidance on dosing rates, feed system compatibility, and integration with your existing pretreatment infrastructure.
Frequently Asked Questions About Lime Slurry Wastewater Treatment
Lime slurry is capable of raising pH into the 11 to 12 range under controlled dosing conditions. For metals precipitation, target pH typically falls between 9.0 and 11.0, depending on the specific metals present. For standard discharge compliance, systems are usually controlled to maintain effluent pH within the 6.0 to 9.0 range required by most pretreatment programs.
Under DOT and IATA regulations, OVIVO ALAR lime slurry is not regulated as a dangerous good for domestic and air transport. Under IMDG (maritime), it carries UN Number UN3264 and is classified as a Class 8 corrosive liquid. It is not classified as a marine pollutant. Please see SDS for most up to date information.
The SDS designates OVIVO ALAR lime slurry with a Danger signal word. Recommended PPE includes chemical-resistant gloves, chemical-resistant clothing, an impervious apron, and a chemical respirator. Eye wash stations and emergency showers should be accessible when handling chemicals. Handlers should review the full SDS before working with this product.
