Determination of toxic PAH concentrations for fermentation and evaluation of supernatants and sewage sludge toxicity using TEF indicators

• Published in: Desalination and water treatment Vol. 268; pp. 182 - 193
• Main Authors: Macherzyński, B., Włodarczyk-Makuła, M., Andrzejewska-Górecka, D., Wszelaka-Rylik, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-08-2022
• Subjects: Fermentation process; Polycyclic aromatic hydrocarbons; Sewage sludge; Supernatants; Toxic equivalency factor; Toxicity equivalency factor; Fermentation process; Toxic equivalency factor; Toxicity equivalency factor; Supernatants; Polycyclic aromatic hydrocarbons; Sewage sludge
• ISSN: 1944-3986; 1944-3986
• DOI: 10.5004/dwt.2022.28714

This paper presents the evaluation results of the toxicity of supernatants and sewage sludges using toxicity equivalency factor indicators for polycyclic aromatic hydrocarbons (PAHs) and determines the toxic concentrations of these compounds for the fermentation process. The study was conducted using municipal sewage sludge and sludge from an on-site coking wastewater treatment plant. Municipal sewage sludge (5 samples) constituted the control sample, whereas mixtures of municipal sewage sludge and coke oven sludge were the test samples: S1 municipal sludge with coke oven sludge in the ratio of 20:1 (5 samples) and S2 in the ratio of 6:1 (4 samples). The sludges were incubated at 37°C without light. Quantitative analysis of 16 PAHs was carried out using a gas chromatograph coupled to a mass spectrometer. The determination of PAHs was carried out in the solid and supernatants phase separated from the sludge. The control of fermentation process consisted in the determination of dry matter, mineral and organic compounds, measurement of the amount and composition of biogas. Threshold toxic concentration of PAHs for microorganisms at which the fermentation process breaks down is 2,275 μg/kg dry mass for the solid phase and 4 μg/L – for the sludge liquids. The average toxic equivalency factor value for 16 PAHs for the post-fermentation sludge was 79% lower than the initial value and 570% higher for the sludge liquids. Therefore, recirculation of liquids may adversely affect the efficiency of biological wastewater treatment.