Enhancing biosludge dewaterability with hemoglobin from waste blood as a bioflocculant

Authors: GHAZISAIDI, HAMED - University Of Toronto; Garcia, Rafael; TRAN, HONGHI - University Of Toronto; YUAN, RUNLIN - University Of Toronto; ALLEN, D. GRANT - University Of Toronto

Submitted to: Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2020
Publication Date: 11/22/2020
Citation: Ghazisaidi, H., Garcia, R.A., Tran, H., Yuan, R., Allen, D. 2020. Enhancing biosludge dewaterability with hemoglobin from waste blood as a bioflocculant. Polymers. 12(11):2755. https://doi.org/10.3390/polym12112755.
DOI: https://doi.org/10.3390/polym12112755

Interpretive Summary: A by-product of the activated sludge wastewater treatment process is excess sludge which must be disposed. The sludge has very high water content, making it bulky and expensive to transport and landfill. Substances in the sludge bind the water and make it difficult to separate the water from the solid components of the sludge. To overcome over this problem, the sludge is normally treated with a synthetic chemical called a conditioner that causes the sludge to release some of its water. In previous research, it was shown that a protein could serve as an effective substitute for the synthetic conditioner, but this protein was too expensive for the purpose. In the current research, a less expensive protein was applied to the problem. Protein recovered from slaughterhouse blood was not effective, but this protein could be modified in a way gave it the properties of an effective sludge conditioner. The results represent an advance towards reducing the use of synthetic chemicals in wastewater treatment and disposal of such chemicals in the environment.

Technical Abstract: Synthetic polymers are widely used in the treatment of biosludge (waste activated sludge) to enhance its dewaterability. This paper discusses the results of a systematic study using hemoglobin (Hb) from animal blood and methylated hemoglobin (MeHb), a derivative in which a methyl group replaces the hydrogen carboxyl groups, to replace synthetic polymers to improve the dewatering efficiency of biosludge. With regular hemoglobin, no improvement in biosludge dewatering was found. With 10% of methylated hemoglobin per total solids content, however, the dry solids content of biosludge increased from 10.2 (± 0.3) wt% to 15.0 (± 1.0) wt%. Zeta potential measurements showed a decrease in negative surface charge of the particles in biosludge from -34.3 (± 3.2) mV to -19.0 (± 2.1) mV after the treatment with methylated hemoglobin. This, along with an unchanged particle size distribution after conditioning, suggests that charge neutralization is likely the main cause of particle flocculation. With charges neutralized, the extracellular polymeric substances (EPS) around the biosludge flocs become loosened, releasing the trapped water and hence increasing dewaterability.