Are native microalgae consortia able to remove microplastics from wastewater effluents?

Wastewater Treatment Plants (WWTPs) are potential sources of microplastics (MPs) in the aquatic environment. This study aimed to investigate the potential of wastewater-native microalgae consortia to remove MPs from the effluent of two different types of WWTPs as a dual-purpose solution for MPs mitigation and biomass production. For that purpose, the occurrence of MPs from two types of WWTP effluents was analysed over one year. MPs were characterized in terms of morphology (microbead, foam, granule, irregular, filament and film), colour and size. The wastewater characterisation was followed by the removal of MP loads, using native microalgae consortia, pre-adapted to the wastewater effluent. Microalgae consortia evolved naturally through four mitigation assays, adapted to seasonal conditions, such as temperature, photoperiod, and wastewater composition. MPs were present in all the effluent samples, ranging from 52 to 233 MP L-1. The characterisation of MPs indicated a predominance of white and transparent particles, with irregular and filament shapes, mainly under 500 μm in size. The μFTIR analysis revealed that 43% of the selected particles were plastic, with a prevalence of polypropylene (PP) (34%) and polyethylene terephthalate (PET) (30 %). In the mitigation experiments, substantial biomass production was achieved (maximum of 2.6 g L-1 (d.w.)), with successful removal of MPs, ranging from 31 ± 25% to 82 ± 13%. These results show that microalgae growth in wastewater effluents efficiently promotes the removal of MPs, reducing this source of contamination in the aquatic environment, while generating valuable biomass. Additionally, the strategy employed, requires minimal control of culture conditions, simplifying the integration of these systems in real-world WWTP facilities for improved wastewater management.

P975Composite electroanatomical maps locate rapid activity within low voltage zones in persistent AF

Funding Acknowledgements

Our research group receives an educational grant from Abbott Inc.

Introduction. Outcomes from catheter ablation of persistent AF (psAF) are not favourable. The two prevailing major directions to improve success are left atrial (LA) substrate ablation, and non pulmonary vein driver ablation. In LA substrate ablation guided by intracardiac voltage, there is debate on the most fitting mapping rhythm and the appropriate cut offs for low voltage zones (LVZ). Non pulmonary vein driver ablation requires extensive experience and relies on complex pattern recognition by the operator, introducing subjectivity, that may lead to reduced reproducibility. AF drivers have been shown to localise to LVZs. We propose an objective, patient-tailored method of identifying rapid activity within LVZs to locate drivers of psAF. 

Methods. Eleven patients (61 ± 10.8 years of age, 9 male) undergoing first time catheter ablation for psAF were included. 3D maps were collected with a double spiral 20 pole catheter, in non-cardiac triggered mode, recording 8s segments at each bipole. Mean AF voltage (AFV) a AF cycle length (AFCL) was calculated for each 8s segment using automated algorithms. Grades of rapid activity and low voltage were defined as the 10th 20th and 30th percentile of all collected points within a patient. Percentile-matched composite LVZ-ARA maps were created on a research platform. 

Results. Mean LVZ percentage of the total mapped area was 4.67 ± 2.4%, 13.95 ± 3.8%, 23.81 ± 5.7% for the 10th, 20th and 30th percentiles respectively (Table 1). Mean, percentile matched LVZ-ARA overlap area percentage of the total mapped area was 0.3 ± 0.25% (10th-10th), 0.86 ± 0.58 (20th-20th), 3.1 ± 1.9% (30th-30th). ARAs represented a small proportion of all LVZs. Location of overlap areas differed significantly between patients and were marked with colours. Multi-colour areas including purple represent LVZ, multi-colour areas excluding purple, show LVZ-ARA overlap (examples in Fig 1). 

Conclusion. Analysis of LVZ-ARA overlap by mean AFV and AFCL provides an objective method of identifying potential drivers that localise to LVZs. The identified overlap areas constituted small, occasionally disparate areas within the LVZ of the LA. By adjusting the AFCL and AFV percentiles, the overlap areas can be tailored at the operator’s discretion, maintaining reproducible, objective decision making, without the need for complex pattern recognition. If ablation is planned, established techniques can be used to target the overlap areas, such as homogenisation or transection and connection to anatomical or ablative non-conductive tissues.

AFCL 10th AFCL 20th AFCL 30th AFV 10th AFV 20th AFV 30th All patients 128 ± 13 ms 144 ± 10 ms 150 ± 9 ms 0.15 ± 0.02 mV 0.19 ± 0.03 mV 0.24 ± 0.04 mV Mean values of percentile cut offs. AFCL: AF cycle length; AFV: AF voltage

Abstract Figure. Fig 1

P991Pattern of rapid activity is preserved in persistent AF in selected locations after pulmonary vein isolation

Funding Acknowledgements

Our research group receives an educational grant from Abbott Inc.

Introduction. There is evidence to suggest that structural remodelling in psAF potentially gives rise to areas of rapid cycle length activity that may act as driving mechanisms. We describe a new method to compare rapid activity (RA) in psAF prior to and after pulmonary vein isolation, in extended AF segments (EAFS). We focus on patterns of RA, based on the hypothesis that AF drivers are transient but recur in the same locations. 

Methods. Five patients (61 ± 8 years of age, 3 male) for catheter ablation of psAF were included. 3D maps were collected with a double spiral 20 pole catheter. In stable locations, pre and post PVI, 37s EAFS were recorded using 8s segments, automatically every 1s, creating a 7s overlap between segments. Dominant cycle length (DCL) was determined for every 8s segment by a fully automated algorithm. RA was defined as the rapidest 20th percentile for each patient. RA episodes consisted of continuous segments with rapid DCL (black lines in Fig 1) and terminated with a non-rapid segment (red lines on Fig 1). Episodes were truncated where overlap occurred (Box 1 and Box 2 in Fig 1). The pattern of RA was assessed by the number, cumulative duration and mean duration of RA episodes within an EAFS pre and post PVI.

Results. Mean DCL of EAFS increased significantly in 4/5 patients after PVI, the number of EAFS with rapid activity showed a reduction in all patients.  The percentage of new sites with RA post PVI was 27%. The number of sites that retained RA post PVI was 14 ± 11.3 (58.3%; Table 1).  Of these, number and cumulative duration of RA did not change in 4/5 patients, and mean duration of RA remained stable in 5/5.

Conclusion. An automated DCL algorithm shows that, in most cases, global AFCL prolongs significantly with PVI overall, but selected foci retain RA and RA patterns. These may represent active drivers, as their activity appears to be independent of their surroundings.

Table 1 Patient ID Number of segments Mean AFCL ± SD of all segments Number of EAFS with rapid activity Pre-PVI Post-PVI P Pre-PVI Post-PVI New sites 1 145 135 ± 8.9 141 ± 9.8 <0.001 94 62 15 2 121 154 ± 12.9 162 ± 15.0 <0.001 94 72 11 3 172 148 ± 13.7 160 ± 16.6 <0.001 108 82 25 4 301 172 ± 22.9 174 ± 21.5 0.418 198 189 58 5 200 177 ± 9.9 215 ± 18.1 <0.001 87 43 14 Pre and Post PVI cycle length and EAFS with rapid activity. (AFCL: AF cycle length; EAFS: Extended AF segments; PVI: Pulmonary vein isolation)

Abstract Figure.