New concept for an aerobic sludge digestion process without aeration using sponge carriers

Area of Science:

• Environmental Science
• Microbiology
• Wastewater Treatment

Background:

• Sludge treatment is crucial for environmental protection and resource recovery.
• Conventional aerobic digestion often requires significant energy input for aeration.
• Developing energy-efficient sludge treatment methods is a priority.

Purpose of the Study:

• To investigate a novel aerobic digestion process for sludge treatment without active aeration.
• To evaluate the efficiency of sludge degradation using sponge carriers.
• To understand the microbial community dynamics and mechanisms involved in sludge reduction.

Main Methods:

• Sludge was immobilized in a sponge carrier and incubated for 21 days at ambient temperature (20°C).
• Oxygen supply was achieved through atmospheric diffusion or water recirculation.
• Sludge degradation was assessed by measuring suspended solids, volatile suspended solids (VSS), and chemical oxygen demand (COD).
• Microbial community structure was analyzed using molecular techniques, and nitrogen stable isotope ratios (δ15N) were measured.

Main Results:

• Volatile suspended solids (VSS) were reduced by approximately 40% over 21 days.
• Rapid sludge degradation occurred within the first 7 days, primarily driven by predation.
• Nitrogen stable isotope ratios (δ15N) indicated an increase in the microbial community's trophic level.
• Molecular analysis confirmed the presence of aerobic organisms and shifts in microbial community structure.

Conclusions:

• The proposed aerobic digestion process effectively degrades sludge without aeration, utilizing predation and endogenous respiration.
• Sponge carriers facilitate efficient sludge treatment, offering a potentially low-energy alternative.
• The findings highlight the role of microbial predation in initial sludge reduction and subsequent endogenous respiration for overall degradation.