Phosphorus Stripping from Anaerobic Digester Supernatant Using Calcium Silicate Hydrate as Sorbent

Abstract

Excess phosphorus present in anaerobic digester supernatant contributes significantly to eutrophication and deterioration of aquatic ecosystems when discharged without adequate treatment. Efficient phosphorus recovery and removal from wastewater streams have therefore become essential for sustainable nutrient management and environmental protection. The present study investigates phosphorus stripping from anaerobic digester supernatant using calcium silicate hydrate as a sorbent under controlled operational conditions. The research focuses on evaluating sorption capacity, phosphorus removal efficiency, reaction kinetics, and process optimization associated with calcium silicate hydrate-based treatment systems. Experimental analysis was conducted to examine the influence of pH, sorbent dosage, contact time, initial phosphorus concentration, and temperature on phosphorus adsorption and precipitation behavior. Results demonstrate that calcium silicate hydrate effectively removes dissolved phosphorus through combined adsorption and calcium phosphate precipitation mechanisms, leading to substantial reductions in phosphate concentration within the treated supernatant. The study further reveals that alkaline conditions and optimized sorbent loading significantly enhance phosphorus uptake efficiency and improve overall treatment performance. Kinetic and equilibrium analyses indicate stable sorption behavior and favorable interaction between phosphate ions and active calcium-containing sites on the sorbent surface. Comparative assessment with conventional phosphorus removal technologies confirms the advantages of calcium silicate hydrate systems, including lower chemical requirements, improved operational simplicity, and potential resource recovery applications.