Keywords
anaerobic granulation
cultivable microbial diversity
CFU/mL
hospital wastewater
natural additives
How to Cite
Abstract
IntroductionAnaerobic granulation is a critical process governing biomass retention, hydrodynamic stability, and treatment efficiency in Upflow Anaerobic Sludge Blanket (UASB) reactors treating high-strength wastewaters. However, limited empirical evidence exists regarding the microbiological structure and granulation mechanisms of anaerobic granules developed during the treatment of hospital wastewater, particularly under conditions enhanced by natural additives in low-resource settings.
PurposeThis study aimed to quantitatively and qualitatively characterize the cultivable microbial community associated with anaerobic granules formed in an optimized UASB reactor treating raw hospital wastewater from the University Clinics of Kinshasa, with specific attention to granulation mechanisms promoted by natural additives.
MethodsA pilot-scale UASB reactor was operated under steady-state conditions and supplemented with natural additives (natural clay, crushed eggshells, ground maize, and lime) to enhance microbial activity and granule formation. Anaerobic granules were aseptically collected and microbiologically analyzed using selective and non-selective culture media at a 10-1 dilution. Microbial enumeration was performed in triplicate and expressed as colony-forming units per milliliter (CFU/mL). Morphological and structural characteristics of the granules were assessed via optical microscopy.
ResultsThe total cultivable microbial density reached 1.65 x 104 CFU/mL. Fermentative bacteria predominated, representing approximately 76% of the cultivable population. Biofilm-forming bacteria, including staphylococci and Pseudomonas aeruginosa, collectively accounted for about 30%, while hydrolytic fungi represented approximately 16.5%. Microscopic observations revealed compact, spherical granules (1–3 mm diameter) with distinct microbial stratification and a well-developed extracellular polymeric substance (EPS) matrix, indicating stable anaerobic granulation.
ConclusionsThe findings demonstrate that natural additives can effectively promote microbial growth, EPS production, and structural stability of anaerobic granules during hospital wastewater treatment in UASB reactors. This study provides practical insights into granulation mechanisms under real hospital effluent conditions. Future research integrating molecular microbial analyses and long-term reactor performance monitoring is recommended to better elucidate microbial dynamics and system resilience.
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