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Optimizing Sludge Phosphorus Removal with Calcium Nitrate – Achieving >85% Reduction in Total Phosphorus Concentration

Optimizing Sludge Phosphorus Removal with Calcium Nitrate – Achieving >85% Reduction in Total Phosphorus Concentration

February 07, 2026 | Technical Analysis | HRSU Research

Understanding Wastewater Issues

Wastewater treatment plants are struggling to consistently meet increasingly strict total phosphorus discharge limits (<0 .3="" also="" and="" by="" class="hrsu-citation" composition="" generated="" managing="" methods="" mg="" of="" sludge="" sup="" the="" traditional="" volume="" while="">1

, leading to operational inefficiencies and potential increased treatment costs2. Monitoring phosphorus concentrations and sludge characteristics – specifically tracking levels below 0.3 mg/L and assessing sludge solids content – is crucial for regulatory compliance and optimizing treatment processes1. Failure to maintain these targets can result in fines and necessitate adjustments to operational strategies, potentially impacting plant capacity and overall treatment effectiveness2.

How Calcium Nitrate Solves It

Calcium nitrate provides an effective solution for wastewater phosphorus removal due to its high phosphorus content and ability to form insoluble calcium phosphate precipitates within a pH range of 6.5-7.54. Careful dosage control of calcium nitrate allows for exceeding 85% reduction in Total Phosphorus within the effluent4. The mechanism involves the formation of calcium phosphate, driven by supersaturation and influenced by factors like pH, seed materials, and wastewater composition5. This process, coupled with controlled addition, significantly minimizes sludge volume compared to traditional alum-based methods4.

Specifications and Dosage

The procurement specification requires calcium nitrate with a purity exceeding 99% to ensure consistent phosphorus removal6. Dosage will be determined based on effluent phosphorus levels, typically ranging from 1 to 5 kg/m3, with adjustments made to achieve >85% Total Phosphorus reduction1. Key metrics for evaluation include effluent phosphorus concentration, sludge volume, and the percentage of Total Phosphorus removed6.

Performance Comparison

Calcium nitrate presents a more cost-effective solution compared to alum-based processes, achieving over 85% phosphorus reduction with lower chemical dosages (50-200 mg/l) and consequently reduced sludge volume8. Unlike EBPR systems reliant on carbon availability, calcium nitrate’s precipitation process is independent of this factor, offering predictable performance regardless of wastewater composition8. Furthermore, the ability to precisely control phosphorus removal with calcium nitrate translates to a more targeted and potentially less expensive treatment strategy than broader EBPR approaches7.

Procurement Checklist

Procurement managers must require phosphorus removal chemical suppliers to provide detailed technical data, including ASTM standards for purity and dissolution rates, demonstrating consistent performance achieving Total Phosphorus discharge limits less than 0.

Why Powdered Calcium Nitrate Outperforms Granules

Powdered calcium nitrate dissolves instantly, providing rapid and consistent phosphorus removal. This immediate dissolution ensures immediate reaction kinetics, maximizing phosphorus capture within the target pH range of 6.5-7.5. Unlike granules, it eliminates the need for agitation or pre-dissolution, simplifying the process and reducing operational complexity.

HRSU Calcium Nitrate boasts exceptional purity, exceeding 99% to ensure reliable performance. Our product is formulated to prevent caking, maintaining a free-flowing powder and consistent application. This consistent quality and guaranteed purity delivers predictable results, and Contact HRSU technical support.

Technical References

  1. What is Phosphorus Removal in Wastewater | SSI Aeration
  2. Phosphorus removal from wastewater - Water Industry Journal
  3. Phosphorus recovery from wastewater via calcium phosphate precipitation
  4. Modelling biological and chemically induced precipitation of calcium ...
  5. [PDF] Method for Recovery of Phosphorus from Animal Wastewater - USDA ARS
  6. Phosphorus Treatment and Removal Technologies
  7. Nutrient removal in the wastewater treatment process | Fehr ... Phosphorous removal from wastewater - Lenntech Using the RTW Activated Sludge Troubleshooting Flow Chart #2 Biological Nutrient Removal Processes and Costs Nutrient removal in the wastewater treatment process - Fehr Graham Phosphorus Treatment and Removal Technologies Nutrient removal in the wastewater treatment process - Fehr Graham Phosphorus Treatment and Removal Technologies A study on the repair effectiveness of calcium nitrate slow ...

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