Allochthonous bioaugmentation in ex situ treatment of crude oil-polluted sediments in the presence of an effective degrading indigenous microbiome.

Oil-polluted sediment bioremediation depends on both physicochemical and biological parameters, but the effect of the latter cannot be evaluated without the optimization of the former. We aimed in optimizing the physicochemical parameters related to biodegradation by applying an ex-situ landfarming set-up combined with biostimulation to oil-polluted sediment, in order to determine the added effect of bioaugmentation by four allochthonous oil-degrading bacterial consortia in relation to the degradation efficiency of the indigenous community. We monitored hydrocarbon degradation, sediment ecotoxicity and hydrolytic activity, bacterial population sizes and bacterial community dynamics, characterizing the dominant taxa through time and at each treatment. We observed no significant differences in total degradation, but increased ecotoxicity between the different treatments receiving both biostimulation and bioaugmentation and the biostimulated-only control. Moreover, the added allochthonous bacteria quickly perished and were rarely detected, their addition inducing minimal shifts in community structure although it altered the distribution of the residual hydrocarbons in two treatments. Therefore, we concluded that biodegradation was mostly performed by the autochthonous populations while bioaugmentation, in contrast to biostimulation, did not enhance the remediation process. Our results indicate that when environmental conditions are optimized, the indigenous microbiome at a polluted site will likely outperform any allochthonous consortium.

[Hydrogeochemistry of reservoirs of Imfout, Daourat and Sidi Maâchou dams (Morocco)]. / Hydrogéochimie des retenues de barrage Imfout, Daourat et Sidi Maâchou (Maroc).

Monitoring of the physico-chemical parameters of the water, nutriments and chlorophyll was carried out. Also, of the grading and physico-chemical characteristic of the sediment. Tests of fixation and salting out of phosphor were undertaken. Fluctuations were noted in the physico-chemical parameters, the functional reports, the involvement of the mineral fraction in the mobility of the phosphor in the water-sediment interface, the impact of the pH and an internal dynamic of the phosphor in the sediment.