Synergistic Addition of Polymer, Ferric Chloride, and Hydrogen Peroxide to Enhance the Post-treatment Efficiency of Thermophilic Digestate

• Published in: Waste and biomass valorization Vol. 15; no. 7; pp. 4087 - 4101
• Main Authors: Hyder, Umme Sharmeen, AlSayed, Ahmed, Elbeshbishy, Elsayed, McPhee, Joseph, Misir, Reshmi
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 2024; Springer Nature B.V
• Subjects: Addition polymerization; Biosolids; Cationic polymerization; Chemical treatment; Coagulants; Conditioning; Dewatering; E coli; Efficiency; Engineering; Environment; Environmental Engineering/Biotechnology; Ferric chloride; Hydrogen peroxide; Industrial Pollution Prevention; Moisture content; Nutrients; Odor control; Odors; Original Paper; Oxidants; Oxidizing agents; Polymers; Polysaccharides; Renewable and Green Energy; Sludge; Suction; Turbidity; Waste Management/Waste Technology; Water content; pH adjustment; Hydrogen peroxide; Phosphorous recovery; Thermophilic digestate; Fecal coliform; Pathogen regrowth; Volume reduction
• ISSN: 1877-2641; 1877-265X
• DOI: 10.1007/s12649-024-02437-z

The high-water content in thermophilic digestate (TD) poses challenges for post-treatment. Separating the water from TD involves costly polymer conditioning, which also raises environmental concerns due to leftover polymers. Regulations on treatment and disposal highlight the necessity of reusing biosolids and recovering nutrients. This study aims to enhance TD post-treatment by reducing volume, improving dewatering, recovering phosphorus, and reducing odours and pathogens. The objective is to minimize polymer use and optimize chemical doses by combining a cationic polymer, a metal coagulant ferric chloride (FeCl
3
), and an oxidant hydrogen peroxide (H
2
O
2
) for TD conditioning. It investigates the effectiveness of chemical treatment using polymer alone versus a combination of other chemicals for improved post-treatment efficiency. The dual application of polymer (3.1 kg/t Dry Solids (DS)) and FeCl
3
(2.5 kg/t DS) at alkaline pH 8.0 resulted in improving TD's post-treatment efficiency by specific resistance to filtration (SRF), capillary suction time (CST), turbidity, cake P concentration, centrate protein to polysaccharide (PN/PS) ratio at a range from 87 to 99% compared to raw TD. The combination of polymer, FeCl
3
and H
2
O
2
reduces the odour-generating potential of raw TD by 88%. It produces class A biosolids with a fecal coliform count of 904 MPN/g DS, eliminating
E
.
coli
content by 100% compared to untreated TD cake. Dual and combined chemical addition at pH 8.0 enhances the post-treatment efficiency of TD with improved cake solid content, significant odour reduction, complete removal of P from centrate and improved biosolids quality.