Interaction between Microalgae P. tricornutum and Bacteria Thalassospira sp. for Removal of Bisphenols from Conditioned Media.

We studied the efficiency of three culture series of the microalgae Phaeodactylum tricornutum (P. tricornutum) and bacteria Thalassospira sp. (axenic microalgae, bacterial culture and co-culture of the two) in removing bisphenols (BPs) from their growth medium. Bacteria were identified by 16S ribosomal RNA polymerase chain reaction (16S rRNA PCR). The microorganism growth rate was determined by flow cytometry. Cultures and isolates of their small cellular particles (SCPs) were imaged by scanning electron microscopy (SEM) and cryogenic transmission electron microscopy (Cryo-TEM). BPs were analyzed by gas chromatography coupled with tandem mass spectrometry (GC-MS/MS). Our results indicate that some organisms may have the ability to remove a specific pollutant with high efficiency. P. tricornutum in axenic culture and in mixed culture removed almost all (more than 99%) of BPC2. Notable differences in the removal of 8 out of 18 BPs between the axenic, mixed and bacterial cultures were found. The overall removals of BPs in axenic P. tricornutum, mixed and bacterial cultures were 11%, 18% and 10%, respectively. Finding the respective organisms and creating microbe societies seems to be key for the improvement of wastewater treatment. As a possible mediating factor, numerous small cellular particles from all three cultures were detected by electron microscopy. Further research on the mechanisms of interspecies communication is needed to advance the understanding of microbial communities at the nano-level.

Removal and fate of 18 bisphenols in lab-scale algal bioreactors.

The removal of 18 bisphenols at wastewater relevant concentrations (µg L-1 range) was investigated and compared between Chlorella vulgaris cultures with pH adjusted to 6.8 and pH non-adjusted cultures where pH raised to above 10. Bisphenols with a high partition coefficient (log P > 6) partitioned to biomass soon after spiking, whereas bisphenols with a low partition coefficient (log P < 4) remained largely in the aqueous phase. Hydrophobic bisphenols and BPF isomers were removed to a large degree in pH adjusted conditions, while BPS and BPAF were the most recalcitrant. The overall average removal after 13 days was similar in both experiments, with 72 ± 2% and 73 ± 5% removed in pH non-adjusted and pH adjusted series, respectively. The removal correlated with chlorophyll a concentration for most bisphenols meaning that algae played a crucial role in their removal, while culture pH also governed the removal of some compounds.

Microalgae-based removal of contaminants of emerging concern: Mechanisms in Chlorella vulgaris and mixed algal-bacterial cultures.

Incomplete removal of contaminants of emerging concern (CECs) has been reported for conventional wastewater treatment technologies. Microalgae-based treatment has recently gained interest thanks to simultaneous removal capacity of organic and inorganic compounds and potentially CECs. In this study, a lab-scale monoculture of Chlorella vulgaris and mixed microalgal-bacterial culture were compared in terms of removal of 28 CECs (bisphenols, 2018 EU Watch List substances, including neonicotinoids, pharmaceuticals, selected transformation products). The removal pathways in light and dark abiotic controls were also studied. Batch photobioreactors were run at hydraulic retention times of 11-12 days and CECs spiked at environmentally relevant concentrations (1-20 µg L-1). The mixed culture was better at removing bisphenols, compared to C. vulgaris. Bisphenols' log Kow was significant in removal pathways, where bisphenols with high log Kow were removed abiotically while bisphenols with low log Kow were mainly biodegraded. The removal degrees and the pathways of pharmaceuticals and EU Watch List substances were comparable between both cultures, showing no impact of log Kow for most compounds; however, the removal with C. vulgaris was faster for some. High log Kow was associated with high removal of estradiol in abiotic controls, showing the importance of adsorption onto biomass and suspended matter.

Determination of 18 bisphenols in aqueous and biomass phase of high rate algal ponds: Development, validation and application.

High rate algal ponds (HRAP) are an alternative to conventional wastewater treatment with the potential for wastewater and biomass reuse. In this study, we report the development and validation of methods for analysing 18 bisphenols (BPs) in the aqueous and biomass phase of HRAP. For aqueous phase samples, obtained LLOQ ranged from 10 to 30 ng/L, and recoveries from 78% to 106%. The relative expanded uncertainty was highest at the lowest spiking level (100 ng/L) and ranged from 27% to 66% (BPA), while for the biomass, the LLOQ ranged from 25 to 75 ng/g dw, recoveries from 84% to 103%. The uncertainty ranged from 16% to 37% (BPA). On average, the influent contained 329, 144, and 21 ng/L of BPA, BPS and 4,4'-BPF, and the effluent 69 ng/L, 94 ng/L and

Use of hydrodynamic cavitation in (waste)water treatment.

The use of acoustic cavitation for water and wastewater treatment (cleaning) is a well known procedure. Yet, the use of hydrodynamic cavitation as a sole technique or in combination with other techniques such as ultrasound has only recently been suggested and employed. In the first part of this paper a general overview of techniques that employ hydrodynamic cavitation for cleaning of water and wastewater is presented. In the second part of the paper the focus is on our own most recent work using hydrodynamic cavitation for removal of pharmaceuticals (clofibric acid, ibuprofen, ketoprofen, naproxen, diclofenac, carbamazepine), toxic cyanobacteria (Microcystis aeruginosa), green microalgae (Chlorella vulgaris), bacteria (Legionella pneumophila) and viruses (Rotavirus) from water and wastewater. As will be shown, hydrodynamic cavitation, like acoustic, can manifest itself in many different forms each having its own distinctive properties and mechanisms. This was until now neglected, which eventually led to poor performance of the technique. We will show that a different type of hydrodynamic cavitation (different removal mechanism) is required for successful removal of different pollutants. The path to use hydrodynamic cavitation as a routine water cleaning method is still long, but recent results have already shown great potential for optimisation, which could lead to a low energy tool for water and wastewater cleaning.