Affiliation:
1. Department of Environmental and Safety Engineering, Taiyuan Institute of Technology, 31 Xinlan Road, Taiyuan 030008, China
2. College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China
Abstract
Sludge alkaline fermentation liquid (AFL) is a potential carbon source for biological denitrification. However, its effectiveness is limited due to the presence of nutrients and heavy metals. In this study, acid-modified sepiolite (MSEP) was used to extract short-chain fatty acids (SCFAs) from AFL under optimized conditions and then with the prepared MSEP-AFL as a carbon source for denitrification. The optimal condition with an MSEP dosage of 1.96 g/L and pH 7.93 at 30 °C was obtained based on single-factor experiments and response surface methodology (RSM). Carbon balance revealed that 96.2% of the SCFAs, including 43.7% acetate and 23.5% propionic acid, was retained in the MSEP, demonstrating its high selectivity. The adsorption process followed the pseudo-second-order kinetic and Langmuir isothermal model, indicating dominant physical adsorption on the surface or in the fiber pores. This was further supported by the changes in the morphological features and surface properties of the MSEP. In the batch nitrate utilization experiments, the prepared MSEP-AFL was proven to be efficient as a carbon source, with a nitrate removal efficiency of 88.7% and a specific denitrification rate of 8.2 mg NOx-N/g VSS·h, which was 22% higher than that of the AFL. This was due to the establishment of a delicate “release–utilization” balance. These findings contribute to our understanding of the use of AFL for denitrification.
Funder
National Natural Science Foundation of China
the China Postdoctoral Science Foundation
the Fundamental Research Program of Shanxi Province
the Scientific and Technological Innovation Program of Higher Education Institutions in Shanxi