Microplastic particles are now present in every part of our environment and pose serious threats to our ecosystem and to human health. Those tiny particles represent a diverse range of plastic fragments < 5mm.
The Great Bubble Barrier’s mission is to clear rivers and canals from all sorts of plastics and thereby prevent pollution in the ocean to protect the global ecosystem.
During a test conducted in Berlin, the bubble barrier proved that it could catch buoyant fragment as small as 1mm, therefore including microplastics.
In a joint effort, KWR Water Research Institute, Hoogheemraadschap Hollands Noorderkwartier, PWN, PWN-T and Het Water Laboratorium teamed up with The Great Bubble Barrier to investigate how a bubble barrier could mitigate the outflow of microplastics in treated wastewater.
The ultimate goal of the consortium is to prevent microplastic discharge from effluent towards surface water. To reach this goal an effective removal technique is necessary as well as reliable analytical techniques. The consortium has therefore investigated the following:
- The amount of microplastics in the treated waste water (effluent);
- The effect of a bubble curtain (Bubble Barrier) on microplastics with a size of 0.5 mm to 0.02 mm
- The improvement and standardization of the measuring method for microplastics.
With this, the consortium is taking a step towards clarifying the nature of the cause and reducing the occurrence of microplastics in surface water as they can pose a threat to people and the environment.
The Bubble Barrier was installed at a wastewater treatment plant in Wervershoof, North Holland, right after the wastewater treatment installation in the effluent canal. Via that canal, the purified wastewater flows in rivers and eventually the ocean.
This Bubble Barrier gave insights into the effect of the Bubble Barrier on microplastics in water. To measure this effect, three locations were measured by KWR following the TRAMP methodology, every second week. The Bubble Barrier in Wervershoof had a length of 16 meters.
Monitoring point 1 – Baseline
This location will give insights in the amount of microplastics within the effluent; after the wastewater has been treated.
Monitoring point 2 – The effect
This location will give insights in the presence of microplastics just before the Bubble Barrier. We expect a higher concentration of microplastics, because the Bubble Barrier creates a circular current on the surface of the effluent.
Monitoring point 3 – The result
This location will give insights in the presence of microplastics just after the Bubble Barrier. We expect a lower concentration of microplastics compared to monitoring point 2.
OUTCOME & EXTERNAL FACTORS
In the context and conditions studied it didn’t detect a difference between the amount of microplastics on one side or the other of the bubble curtain.
This could be explained through several causes and external influences such as sampling methods, depth, weather and flux as well as analytical detection limitations which are explained below.
These results are strongly dependent on the applied sampling method & analysis. Next to that, microplastics fall into a particularly complex analytical area of which there is still little thorough knowledge.
- Analytical & sampling methods: There isn’t currently any standardized methods in place to measure microplastics. There are no blanks, standard analyses, standards or prescribed requirements and results vary often. Therefore it is difficult to assess the results of a bubble curtain efficacy on microplastics. These results are strongly dependent on the applied sampling method & analysis. Next to that, microplastics fall into a particularly complex analytical area of which there is still little thorough knowledge.
- Depth: Sampling depth was fixed at 15 cm below water surface. However, the distribution of plastics across a water column is unknown and plastic is not homogeneously spread over the water column.
- Weather: Storm events may cause short term peaks of plastic outflow and the potential effects of these events are not yet well understood.
The research identifies the necessity for standardisation methods and a deeper understanding of factors of influence, e.g., sampling depth, weather conditions and day-to-day fluctuations.
Thus additional research is needed and the consortium will stay in touch for potential future collaboration.
The Great Bubble Barrier is open to conduct further research in collaboration with research institutes to investigate and explore how it can extend its success to particles < 1 mm.