Proposed implementation

Our vision

In the beginning of the project, the aim was defined to develop a resistant and long-lasting solution to clear drug residues out of our wastewater. Since wastewater treatment is centralized in Germany and most parts of Europe and the USA, our main end-users were meant to be wastewater treatment plants. During the project, mainly due to our modelling findings, high flow rates proved to be problematic for enzyme-based degradation. Therefore, we added hospitals, nursing homes, swimming pools and all those with potentially high drug loads in their wastewater as potential end-users.

Implementation: The Lac Man filter unit

As the final product, which could be used in the real world, we imagined as filter blocks or filter units. These consist of a water permeable box containing foam particles with immobilized laccases. These filter units could be installed side by side as often as desired to increase the flow rates. By connecting several filter units in series, the degree of degradation of the drug residues could be influenced. This principle allows a high degree of flexibility, for a perfect adaptation to the conditions on site and makes a scale-up easy.

Challenges and Safety in the implementation

Safety aspects

From the very beginning the most important point in our project was environmental protection. For this reason, we already considered environmental protection and the regulations in Germany in the planning and selection of our project idea. By using immobilized enzymes, we are not dependent on living, expressing organisms on site, thus avoiding the regulations for genetically modified organisms (GMO). Since in Germany and large parts of the EU the release of GMOs into the environment must be strictly avoided, and this is almost impossible in sewage treatment plants, this was one of the basic requirements of our project. Our MCF is also characterized by the fact that it is extremely biostable and resistant to environmental influences and has no negative effects on humans or the environment. The degradation products of our laccases were also analyzed for toxicity in advance to ensure that they pose a lower risk than the substrates. These two aspects make our approach applicable almost everywhere where drug residues get into water.

Challenges

The biggest challenge is the real concentration of drug residues. Therefore, it would be best to use laccases at the earliest possible stage of wastewater treatment. However, it has not been possible for us to test to what extent suspensions of the wastewater limit the efficiency of our foam and clog it. Different analysis of the behaviour of our foam under real life conditions (wastewater treatment plant Plieningen) using our model revealed that the effective flux through the MCF has a high effect on the efficiency. Dividing the flux by two has the same effect as doubling the amount of foam. To get an optimal efficiency in a wastewater treatment plant, we suggest a use in the final clarifier. Here the conditions correspond most closely to the ideal conditions. However, one difficulty would be the return of sediments into the activated sludge tank, which would also transport sedimented foam from the secondary clarifier.

Also, it will be difficult to synthesize and activate such a large amount of silica foam.

In addition to the difficulties of production, an economic incentive must also be created to ensure that such an application is actually used. If the use of drug-residue-clearing applications remains voluntary, no country or organization will bear the cost and effort of production and maintenance. In this respect, our project and its implementation in reality is dependent on mandatory maximum residue limits in the EU and other industrialized countries, such as the USA.

How we imagine others to benefit from our project

With our project we hope to draw the attention of future iGEM teams to the topic of water cleanliness and to lay the foundation for further optimization with the approach of immobilized laccases. With the development of the polylysine tag to improve immobilization and subsequent enzyme activity, we hope to enable further applications for stable enzyme immobilization and make it available to other teams.