Natural carriers in bioremediation: a review

Bioremediation of contaminated groundwater or soil is currently the cheapest and the least harmful method of removing xenobiotics from the environment. Immobilization of microorganisms capable of degrading specific contaminants significantly promotes bioremediation processes, reduces their costs, and also allows for the multiple use of biocatalysts. Among the developed methods of immobilization, adsorption on the surface is the most common method in bioremediation, due to the simplicity of the procedure and its non-toxicity. The choice of carrier is an essential element for successful bioremediation. It is also important to consider the type of process (in situ or ex situ), type of pollution, and properties of immobilized microorganisms. For these reasons, the article summarizes recent scientific reports about the use of natural carriers in bioremediation, including efficiency, the impact of the carrier on microorganisms and contamination, and the nature of the conducted research

Microalgae community shifts during the biogas upgrading in an alkaline open photobioreactor

Aims: To achieve the functional specialization of a microalgae community through operational tuning of an open photobioreactor used for biogas upgrading under alkaline conditions. Methods and Results: An open photobioreactor was inoculated with an indigenous microalgae sample from the Texcoco Soda Lake. A microalgae community was adapted to fix CO2 from synthetic biogas through different culture conditions reaching a maximum of 220 mg CO2 l?1 per day. Picochlorum sp. and Scenedesmus sp. were identified as the prominent microalgae genera by molecular fingerprinting (partial sequencing of 16S rRNA and 18S rRNA genes) but only the first was detected by microscopy screening. Changes in the microalgae community profile were monitored by a range-weighted richness index, reaching the lowest value when biogas was upgraded. Conclusions: A robust microalgae community in the open photobioreactor was obtained after different culture conditions. The specialization of microalgae community for CO2 fixation under H2S presence was driven by biogas upgrading conditions. Significance and Impact of the Study: The alkaline conditions enhance the CO2 absorption from biogas and could optimize specialized microalgae communities in the open photobioreactor. Denaturing gradient gel electrophoresis fingerprinting and richness index comparison are useful methods for the evaluation of microalgae community shifts and photosynthetic activity performance, particularly in systems intended for CO2 removal from biogas where the CO2 assimilation potential can be related to the microbial richness

Control of dissolved CH4 in a municipal UASB reactor effluent by means of a desorption – Biofiltration arrangement

The direct anaerobic treatment of municipal wastewater represents an adapted technology to the conditions of developing countries. In order to get an increased acceptance of this technology, a proper control of dissolved methane in the anaerobic effluents should be considered, as methane is a potent greenhouse gas. In this study, a pilot-scale system was operated for 168 days to recover dissolved methane from an effluent of an upflow anaerobic sludge blanket reactor and then oxidize it in a compost biofilter. The system operated at a constant air (0.9 m3/h ±0.09) and two air-to anaerobic effluent ratio (1:1 and 1:2). In both conditions (CH4 concentration of 2.7 ± 0.87 and 4.3% ± 1.14, respectively) the desorption column recovered 99% of the dissolved CH4 and approximately 30% ± 8.5 of H2S, whose desorption was limited due to the high pH (>8) of the effluent. The biofilter removed 70% ± 8 of the average CH4 load (60 gCH4/m3h ± 13) and 100% of the H2S load at an empty bed retention time of 23 min. The average temperature inside the biofilter was 42 ± 9 °C due to the CH4 oxidation reaction, indicating that temperature and moisture control is particularly important for CH4 removal in compost biofilters. The system may achieve a 54% reduction of greenhouse gas emissions from dissolved CH4 in this particular case