Enhanced bio-drying effect in low-temperature: Characteristics of sludge hyperthermophilic aerobic bio-drying by inoculating with thermophilic bacteria and full-scale operation

Abstract

Low-temperature environment leads to a weakened ability of sludge bio-drying to drive system evaporation and the system’s water removal capacity of aeration (ΣF·ΔP), significantly reducing water removal rate and consequent decrease of the bio-drying index. The bio-drying system maintains more microorganisms active by inoculating with thermophilic bacteria to produce heat when it reaches above 55 °C to enhance the temperature cumulation and ΣF·ΔP to remove moisture and shorten the bio-drying time rapidly. The results showed that the percentage of the thermophilic period (T ≥ 55 °C) and hyperthermophile period (T ≥ 70 °C) of the hyperthermophilic pile was 67.16% and 30.14%, respectively. In comparison, only the thermophilic period of 5.48% existed in the conventional pile. The moisture content of the hyperthermophilic pile decreased from 51.23% to 41.52% in 12 days and decreased from 50.25% to 41.35% in 21 days that in the conventional pile. Meanwhile, the hyperthermophilic pile had a faster VS consumption rate and higher bio-drying index than the conventional pile. The microbial community composition showed that the hyperthermophilic pile mainly comprised thermophilic bacteria, such as Thermopolyspora, and hyperthermophilic bacteria, such as Thermus. The full-scale operation in the plants showed that the sludge inoculated with thermophilic bacteria reached the bio-drying requirement within 12 days with a maximum temperature of 94 °C, which significantly shortened the time of bio-drying and increased the sludge treatment capacity.

Graphical abstract

Keywords:

• Sludge bio-drying
• hyperthermophilic aerobic bio-drying
• bio-drying index
• temperature and humidity distribution
• thermophilic bacteria

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China (No. 2020YFC1806402) and the Shenyang Science and Technology Plan Project (No. 20–202–4–37).