Study on Dissolution Characteristics of Excess Sludge by Low-Temperature Thermal Hydrolysis and Acid Production by Fermentation

Abstract

To investigate the dissolution characteristics of low-temperature thermal pretreatment conditions and the process of sludge fermentation to produce acid, the influence of thermal pretreatment temperature on the dissolution of excess sludge organic composition and the mechanism of cell crushing of sludge thermal pretreatment were analyzed by an experimental method, and the performance of acid production was explored by sludge fermentation after pretreatment at different temperatures. The performance of acid production by sludge fermentation after pretreatment at different temperatures was measured. The results proved that the soluble chemical oxygen demand (SCOD) shows the largest increase in dissolution rate (11.92%) at 70 °C and in dissolution quantity (6518.33 mg/L) at 90 °C. However, at 80 °C, the solubility of total organic carbon (TOC) is the highest (3224.47 mg/L), and at 70 °C, the best dissolution conditions for soluble carbohydrate (SC) and soluble protein (SP) reached 340.07 and 80.92 mg/L, respectively. The degree of sludge breaking starts to increase at 70 °C. Correlation analysis shows that dissolved organic matter is mainly derived from the cell wall and intracellular material and SP is mainly derived from intracellular material. Excitation–emission matrix spectra and parallel factor analysis (EEM-PARAFAC) divides the sludge dissolved organic matter (DOM) into five fluorescent components, including C1 (318/366) tyrosine, C2 (418/470) UVA humic acid, C3 (282/334) tryptophan substances, C4 (322/430) UVC humic acids, and C5 (314, 382, 454/526) UVA humic substances. Fermentation acid production experiment shows that the peak concentration is highest at 80 °C, the arrival time is 2 days, and the acid production type is butyric acid fermentation. Thus, it is proved that low-temperature thermal pretreatment promotes the process of acid-producing fermentation and has no effect on the type of fermentation. The optimal condition for hydrolytic dissolution and acid production under low-temperature thermal pretreatment is 80 °C.

Effect of Thermal Pretreatment of Pineapple Peel Waste in Biogas Production using Response Surface Methodology

“…The increase in biogas production indicates that cellulose is completely degraded and the hydrolysis process is going well. It is stated by (Penghe et al, 2020) that high hydrolysis or dissolving rate can be achieved well by conducting thermal pretreatment using a short temperature and time duration or low temperature with a longer duration pretreatment. Due to the high rate of hydrolysis on thermally pretreated substrates compared to untreated substrates, biogas production is higher at the beginning of the anaerobic process.…”

“…According to (Penghe et al, 2020), high hydrolysis or dissolution rates is achieved well by performing thermal pretreatment using a low temperature with a longer duration pretreatment. According to (Acharjee et al, 2011), the high water content of lignocellulosic biomass corresponding to the moisture level of lignocellulosic biomass also impacts the pretreatment time required, which takes longer to be pretreated using a hot water bath.…”