RESUMEN
In this work, polyhydroxy butyrate (PHB) and biochar from pine wood (PWB) are used in a mini-pilot scale biological reactor (11.3 L of geometric volume) for trichloroethylene (TCE) removal (80 mgTCE/day and 6 L/day of flow rate). The PHB-biochar reactor was realized with two sequential reactive areas to simulate a multi-reactive permeable barrier. The PHB acts as an electron donor source in the first "fermentative" area. First, the thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses were performed. The PHB-powder and pellets have different purity (96% and 93% w/w) and thermal properties. These characteristics may affect the biodegradability of the biopolymer. In the second reactive zone, the PWB works as a Dehalococcoides support and adsorption material since its affinity for chlorinated compounds and the positive effect of the "coupled adsorption and biodegradation" process has been already verified. A specific dechlorinating enriched culture has been inoculated in the PWB zone to realize a coupled adsorption and biodegradation process. Organic acids were revealed since the beginning of the test, and during the monitoring period the reductive dichlorination anaerobic pathway was observed in the first zone; no chlorinated compounds were detected in the effluent thanks to the PWB adsorption capacity.
RESUMEN
Towards chlorinated solvents, the effectiveness of the remediation strategy can be improved by combining a biological approach (e.g., anaerobic reductive dechlorination) with chemical/physical treatments (e.g., adsorption). A coupled adsorption and biodegradation (CAB) process for trichloroethylene (TCE) removal is proposed in a biofilm-biochar reactor (BBR) to assess whether biochar from pine wood (PWB) can support a dechlorinating biofilm by combining the TCE (100 µM) adsorption. The BBR operated for eight months in parallel with a biofilm reactor (BR)-no PWB (biological process alone), and with an abiotic biochar reactor (ABR)-no dechlorinating biofilm (only an adsorption mechanism). Two flow rates were investigated. Compared to the BR, which resulted in a TCE removal of 86.9 ± 11.9% and 78.73 ± 19.79%, the BBR demonstrated that PWB effectively adsorbs TCE and slows down the release of its intermediates. The elimination of TCE was quantitative, with 99.61 ± 0.79% and 99.87 ± 0.51% TCE removal. Interestingly, the biomarker of the reductive dechlorination process, Dehalococcoides mccartyi, was found in the BRR (9.2 × 105 16S rRNA gene copies/g), together with the specific genes tceA, bvcA, and vcrA (8.16 × 106, 1.28 × 105, and 8.01 × 103 gene copies/g, respectively). This study suggests the feasibility of biochar to support the reductive dechlorination of D. mccartyi, opening new frontiers for field-scale applications.
RESUMEN
Groundwater remediation is one of the main objectives to minimize environmental impacts and health risks. Chlorinated aliphatic hydrocarbons contamination is prevalent and presents particularly challenging scenarios to manage with a single strategy. Different technologies can manage contamination sources and plumes, although they are usually energy-intensive processes. Interesting alternatives involve in-situ bioremediation strategies, which allow the chlorinated contaminant to be converted into non-toxic compounds by indigenous microbial activity. Despite several advantages offered by the bioremediation approaches, some limitations, like the relatively low reaction rates and the difficulty in the management and control of the microbial activity, can affect the effectiveness of a bioremediation approach. However, those issues can be addressed through coupling different strategies to increase the efficiency of the bioremediation strategy. This mini review describes different strategies to induce the reduction dechlorination reaction by the utilization of innovative strategies, which include the increase or the reduction of contaminant mobility as well as the use of innovative strategies of the reductive power supply. Subsequently, three future approaches for a greener and more sustainable intervention are proposed. In particular, two bio-based materials from renewable resources are intended as alternative, long-lasting electron-donor sources (e.g., polyhydroxyalkanoates from mixed microbial cultures) and a low-cost adsorbent (e.g., biochar from bio-waste). Finally, attention is drawn to novel bio-electrochemical systems that use electric current to stimulate biological reactions.
RESUMEN
Nowadays porous materials from organic waste, i.e., Biochar (BC), are receiving increased attention for environmental applications. This study adds information on three BCs that have undergone a number of studies in recent years. A Biochar from pine wood, one from rice husk and one from Eupatorium shrubs enriched with Iron, labelled as PWBC, RHBC and EuFeBC respectively, are evaluated for Trichloroethylene (TCE) removal from aqueous solution. Physical-chemical description is performed by SEM-EDS and BET analysis. The decrease of TCE over time follows a pseudo-second order kinetics with increased removal by the PWBC. Freundlich and Langmuir models well fit equilibrium test data. The optimized values of the maximum adsorbed amount, qmax (mg g-1), follows this order 109.41 PWBC > 30.35 EuFeBC > 21.00 RHBC. Fixed-bed columns are also carried out. Best performance is again achieved by PWBC, which operates for a higher number of pore volume, followed by EuFeBC and RHBC. Continuous testing confirms batch studies and makes it possible to evaluate the workability of materials in configurations closer to reality. Results are promising for potential environmental application. In particular, the characterization of several classes of contaminants opens the doors to possible uses in mixed contamination cases.
