Lyophiles of Pseudomonas sagittaria MOB-181 grown in waste-based culture medium improve groundwater Mn removal

VIDOZ M; PACINI V; CIANCIO L; LABANCA C; GOTTIG N; PIAZZA A; OTTADO J

Congreso; SAIB-SAMIGE Joint Meeting 2020 on line; 2020

The presence of Mn(II) in groundwater, a source of drinking water for many populations, is an important concern affecting water quality and interfering with its disinfection process. Biological sand filtration is widely used for groundwater Mn(II) removal since it is an economic and eco-friendly tool. However, the main limitations of this process are long start-up periods and low efficiencies of Mn(II) removal which frequently occur. A powerful strategy to solve these problems is the bioaugmentation of sand filters with Mn-oxidizing bacteria (MOB). We have previously reported that the inoculation of laboratory-scale sand filters with a Pseudomonas sagittaria MOB-181 strain enhances considerably the groundwater Mn(II) removal process. Based on these results, in this work we proposed a new laboratory-scale inoculation methodology, using MOB-181 lyophiles, to optimize the times, costs and operation of filter systems. MOB-181 planktonic cultures and biofilm were grown in Lept medium and in Lept-Mn medium, a specific medium for Mn(II) oxidation and were lyophilized. Liophilization survival ratios showed the highest values for biofilms covered with biogenic Mn oxides. Moreover, crude glycerol waste, a by-product from biodiesel production process, was used to formulate different culture media to grow MOB-181 inoculum. The MOB-181 biofilms were grown in each of these media and growth ability, lyophilization resistance and Mn(II) oxidation capacity were analyzed observing the best performance in Glycerol 1%-Mn. Further, MOB- 181 lyophiles obtained in this medium retained the capacity to adhere to filters sand.For these reasons, MOB-181 biofilms grown in Glycerol 1%-Mn medium were used to carry out bioaugmentation experiments to improve groundwater Mn removal. Inoculation of sand filters with non-lyophilized and lyophilized MOB-181 biofilms were performed and, daily, the Mn removal efficiencies were measured. As control, a non-bioaugmented filter was operated simultaneously. The results clearly demonstrated that the bioaugmentation with MOB181 lyophiles was not only feasible but also allowed to optimize the Mn removal process since this filter reached the optimum Mn removal efficiency earlier than the filter inoculated with non-lyophilized bacteria. Also, in both cases the bioaugmentation lead to an acceleration of Mn removal respect to control filter, as we have previously noticed.Overall, in this work a novel bioaugmentation strategy was developed to improve the performance of groundwater Mn removal. This new alternative, based on the use of low-cost culture media and lyophilized bacteria, represents a solution to the economic and logistic problems that often arise during large-scale bioaugmentation and is also interesting from an environmental point of view since crude glycerol waste can be reused.