Remediation of oil-drilling cuttings by ozonation in semibatch bubble column reactors

The remediation of oil-drilling cuttings (ODC), containing a high percentage of total organic carbon (TOC), total petroleum hydrocarbons (TPH) and moisture, is a challenge. Ozonation is an advanced oxidation method able to destruct a broad variety of organic substances from water and soil. Oil-drilling cuttings are pre-treated inside a sonication bath with three solutions of artificial seawater containing 0.0, 0.2, and 0.5% w/w sodium dodecyl sulphate (SDS) which acts as surfactant and favours the solubilisation of hydrocarbons from the solid to the liquid phase. Afterwards, each pre-treated ODC is diluted at a ratio 1:5 with the corresponding type of seawater, and ozonation of the suspension occurs in a bubble column reactor made of poly methyl methacrylate (PMMA). The transient changes of the TOC content in ODC during the various stages of its treatment are measured with the Walkley-Black titration method. It seems that a percentage ~12-25% of TOC dissolves and is transferred from ODC to seawater, while the treatment of ODC suspended in seawater with ozone leads to the complete removal of the TOC after 2 hrs.

Pilot-scale phycoremediation using Muriellopsis sp. for wastewater reclamation in the Atacama Desert: microalgae biomass production and pigment recovery

Municipal wastewater phycoremediation represents a promising circular economy-based process for wastewater reclamation used to recover water and produce biomass. This study aimed to evaluate a pilot-scale phycoremediation system, using the most efficient strain of microalgae for wastewater reclamation in the Atacama Desert. Nitrogen and phosphorus removal, as well as biomass growth, were compared in different microalgae treatments, namely Muriellopsis sp., Scenedesmus almeriensis, Chlamydomonas segnis, Chlorella pyrenoidosa and Chlorella vulgaris. The most efficient treatments, Muriellopsis sp. and S. almeriensis, were scaled up to 20-L bubble column reactors to evaluate nutrient removal and biomass biochemical profile for potential biotechnological application. Finally, Muriellopsis sp. was selected for a pilot-scale phycoremediation experiment (800-L raceway), which removed 84% of nitrogen, 93% of phosphorus and other chemical compounds after 4 days of treatment to meet most of the Chilean standards for irrigation water (NCh. 1333. DS. MOP No. 867/78). Faecal coliforms count was reduced by 99.9%. Furthermore, biomass productivity reached 104.25 mg·L–1·day–1 value with 51% protein, and pigment content of 0.6% carotenoid, with 0.3% lutein. These results indicate the potential of wastewater phycoremediation at an industrial scale for the production of irrigation water and carotenoid using Muriellopsis sp.

The Effect of Hydraulic Conditions in Barbotage Reactors on Aeration Efficiency

Barbotage reactors such as airlift reactors (ALR) and bubble column reactors (BCR), due to their two-phase flow systems, were investigated in many research papers. In their basic design variants, they are typically used to lift, mix, and aerate liquids, while, when equipped with additional elements in hybrid variants, their individual properties, i.e., lifting, mixing, and aeration of liquids, can significantly change with the same reactor geometry. The object of this study was to develop a hybrid barbotage reactor in various structural design variants. The structure consisted of a barbotage column of 50 mm in diameter, used to transport a water–air mixture outside the reactor (so-called external loop). The installation was additionally equipped with a nozzle in order to improve mixture aeration and circulation efficiency. The nozzle was mounted at various heights of the column pump segment. Additionally, the reactor was equipped with s moving bed in two variants (20% and 40% reactor capacity) in order to determine its effect on the mixture aeration and circulation conditions. Based on the measurement results, aeration curves were prepared for various structural design and column packing variants of the reactor. Properties of the two-phase mixture were determined for both parts—ALR and BCR. Technological and energy parameters of the aeration process were calculated, and the results obtained for the individual structural design variants were compared. It was found that, for the most advantageous design, in terms of aeration efficiency, the aeration nozzle should be placed in the mid-length of the pump segment of the barbotage column, irrespective of the hybrid reactor packing rate with the moving bed. The reactor packing with the moving bed resulted in a decreased mean water velocity in the reactor. For most analyzed structural design variants, the respective packing with the moving bed had no significant effect on aeration efficiency. Only for one structural design variant did the lack of packing significantly improve oxygen levels by as much as approximately 41%.