Optimizing wastewater treatment with PVA gel beads and pumice stones: a multi-stage reactor approach

Effective wastewater treatment is crucial for safeguarding public health and environmental sustainability, particularly in industrial sectors where effluents contain a complex mix of contaminants. This study aims to enhance biological wastewater treatment efficiency by evaluating and comparing two biocarrier materials: polyvinyl alcohol (PVA) gel beads and artificial pumice stones. PVA gel beads, characterized by 95–98% water content and a specific gravity of 1.025 ± 0.01, offer high porosity that facilitates microbial immobilization and improves oxygen and nutrient transfer. In contrast, pumice stones, composed of cement, silica sand, and aluminum powder, provide a lightweight, porous structure conducive to microbial colonization. A lab-scale treatment system was developed employing both suspended and attached growth mechanisms across three experimental phases: (1) a bioreactor utilizing PVA gel beads, (2) a bioreactor with pumice stones, and (3) a hybrid configuration using PVA beads in the aeration unit and pumice stones in the bioreactor. The study developed an innovative hybrid bioreactor system integrating PVA gel beads and pumice stones as complementary biocarriers for wastewater treatment. This novel configuration achieved superior treatment performance with 92% COD (chemical oxygen demand), removal efficiency due to enhanced microbial activity and optimized biofilm formation across different treatment zones. The hybrid system achieved the highest treatment performance, combining the dynamic mixing benefits of PVA beads with the structural advantages of pumice stones. Sludge production was notably reduced, and microbial activity was enhanced, making the system more efficient than those using a single biocarrier type. Limitations of PVA beads, such as low specificity to pollutants and post-use disposal challenges, were observed. The study concludes that a hybrid biocarrier approach holds significant promise for industrial wastewater treatment and recommends further optimization and pilot-scale trials to evaluate long-term applicability across various wastewater profiles.