LAUSR

Abstract Anaerobic treatment of industrial effluents is limited by higher sensitivity of anaerobes. High rate digesters resulted in achievement of higher loadings at lower retention times but, efficiencies were limited due to sensitivity. In this study, performance of novel hybrid anaerobic reactor (HAR) was investigated using high strength effluents combined with increasing 4-chlorophenol loadings. HAR is capable of handling much higher OLRs than UASB system, due to completely fluidized state and AFBR because of greater microbial maintenance. The reactor employs self-immobilized granules for biomass retention. Its temporal analysis demonstrated the effects on glucose removal, 4-chlorophenol removal, biogas generation and intermediates accumulation. These variables were related to microbial dynamics as revealed by profiling of reactor population which strongly correlated to increasing 4-chlorophenol levels. Methanogenesis was hindered with substantial decline in COD removal attributed to intermediates built-up (R > 0.7, CI = 0). This was paralleled with diminished archaeal abundance (R = 0.902, CI = 0), especially aceticlastic groups. HAR achieved 73% and 57.5% 4-chlorophenol and COD removal efficiencies, respectively at 200 ppm 4-chlorophenol loadings. Many genera were identified as tolerant possessing biodegradation capability viz: Methanobacterium, Clostridium, Pseudomonas, Rhodococcus, Bellilinea etc. C. cavendishii, P. knackmussii, R. phenolicus, B. caldifistulae were identified on the fingerprint with increasing pollutant levels. Aerobes having versatile metabolisms were acknowledged in strict anaerobic conditions with involvement in toxin removal. The study demonstrated higher resilience of HAR in comparison to other high rate digesters (like UASB, AFBR) due to its unique characteristics. The findings will help in technological advancement of HAR to grope the effects of 4-chlorophenol while treating high strength effluents.