Performance Evaluation of a Coconut Coir–Immobilized Biphasic Anaerobic Reactor for the Treatment of High-Strength Pharmaceutical Wastewater: Microbial Community Insights

Abstract

Pharmaceutical manufacturing industries generate wastewater containing high concentrations of organic matter and several inhibitory compounds that can adversely affect conventional biological treatment processes. In the present study, the performance of a laboratory-scale biphasic anaerobic reactor was investigated for the treatment of high-strength pharmaceutical wastewater under mesophilic conditions. The system consisted of an acidogenic suspended-growth reactor followed by a methanogenic attached-growth reactor packed with coconut coir as a natural support medium to enhance microbial immobilization and biomass retention.

The reactor was operated at organic loading rates ranging from 0.5 to 3.558 kg COD/m³·d, while the hydraulic retention times were maintained at 24 h and 72 h in the acidogenic and methanogenic reactors, respectively. The acidogenic reactor maintained a pH range between 4.65 and 5.9, whereas the methanogenic reactor operated within a stable pH range of 7.11–8.38, indicating effective phase separation. Maximum COD removal efficiency of 87.54% was observed at lower organic loading rates, while a reduction to 64.68% occurred at higher loading conditions due to temporary accumulation of volatile fatty acids.

Microbial identification revealed the dominance of Microbacterium enclense in the acidogenic phase and Methanococcus aeolicus in the methanogenic phase. The results indicate that coconut coir provides a suitable natural support medium for microbial attachment and improves the stability of biphasic anaerobic treatment systems.