Halophilic Martelella Sp.AD-3 Enhanced Phenanthrene Degradation In A Bioaugmented Activated Sludge System Through Syntrophic Interaction

Polycyclic aromatic hydrocarbons(PAHs)are a group of common recalcitrant pollutant in industrial saline wastewater that raised significant concerns,whereas traditional activated sludge(AS)has limited tolerance to high salinity and PAHs toxicity,restricting its capacity to degrade PAHs.Some non-biological techniques,which are highly cost and might cause second pollution,are employed for the treatment of saline waste water containing PAHs.It is therefore urgent to develop a bioaugmented sludge(BS)system to aid in the effective degradation of these types of compounds under saline condition.In this study,a novel bioaugmentation strategy was developed by using halophilic Martelella sp.AD-3 for effectively augmented phenanthrene(PHE)degradation under 3%salinity.The BS system exhibited a high PHE degradation activity of 2.2 mg·gVSS-1.h-1,nearly 25 times that of AS system.Bioaugmentation and syntrophic effect analysis showed that 0.5～1.5%ratio of strain AD-3 to activated sludge was optimal for BS system to achieve high PHE degradation activity.It was also found that salinity of 3.0%,pH of 7.5-8.5,PHE concentration of 20～200 mg·L-1 were favored for PHE degradation in BS.Although 1-hydroxy-2-naphthoic acid(1H2N)was accumulated obviously,the mineralization of PHE was more complete in the BS system.Reads-based metagenomic coupled metatranscriptomic analysis revealed that the expression values of ndoB,encoding a dioxygenase associated with PHE ring-cleavage,was 5600-fold higher in the BS system than in the AS system.Metagenome assembly showed the members of the Corynebacterium and Alcaligenes genera were abundant in the strain AD-3 bioaugmented BS system with expression of 10.3±1.8%and 1.9±0.26%,respectively.Moreover,phdl and nahG accused for metabolism of 1H2N have been annotated in both above two genera.Degradation assays of intermediates of PHE confirmed that the activated sludge actually possessed considerable degradation capacity for downstream intermediates of PHE including 1H2N.The degradation capacity ratio of 1H2N to PHE was 87%in BS system,while it was 26%in strain AD-3.These results indicated that strain AD-3 contributed mainly in transforming PHE to 1H2N in BS system,while species in activated sludge utilized 1H2N as substrate to grow,thus establishing a syntrophic interaction with strain AD-3 and achieving the complete mineralization of PHE.Long-term continuous experiment confirmed a stable 20 mg·L-1 PHE removal efficiency of 93%and few 1H2N accumulation(less than 0.6 mg·L-1)in BS SBR system,while the COD removal was 84.6～87.6%.This study demonstrated an effective bioaugmented strategy for the treatment of saline wastewater containing PAHs.