The idea

The street filter is a system able to filter microplastics, which largely consist of tire abrasion, from the street water. We have built three different very cheap prototypes and have tested them to improve our system. We introduced our anti-microplastics street filter system to the local street maintenance authority and were able to get more information about the usage and cleaning intervals of normal road gullies. The authority confirmed that this prototype would not have a significant difference in cost and effort.

Microplastics

Origin

Microplastics originate from a process where so-called macroplastics erode and form extremely small plastic beads which can be smaller than 5 micrometers. These particles get into the sewer system and from there into the ocean and water circuit. Due to their small size, microplastic particles have a relatively large surface which can be easily enriched with pollutants. Finally these dangerous micro-beads are absorbed by the ecosystem. So in the end we eat microplastics enriched with dangerous chemicals.

Spread

The macroplastics which later form microplastic particles consist largely of plastic bottles and bags which get into the water by careless people throwing them away. However, this factor is very hard to control because it is difficult to change the people’s morals. Tire abrasion, on the other hand, forms microplastics too and is an even larger problem because it cannot be filtered by purification plants. More than 110,000 tons of tire abrasion get into the ecosystem every year in Germany alone. But those particles are just discharged into the sewer system through road gullies.

The circulation of microplastics – The rubber from our wheels ends on our tables

Impact

There are many particles in the German street water. Some of them are leaves, stones, sand, wood and plastic which consists manly of microplastics from tire abrasion. Leaves and stones smaller than one centimeter get into the sewer system because they are not held back by normal catchment buckets. Purification plants can filter sand and wood, but they are not able to stop microplastics, so these particles get into the environment. The most dangerous ingredients of microplastics formed by tire abrasion are Mercaptobenzothiazole (MBT) or Zinc Dibenzyldithiocarbamate (ZBEC). Their impact on the environment is terrible because of the toxic effect on seaweed, water fleas, fungi and bacteria. MBT is dangerous for the larval development of fish and also damages cell membranes.

Existing Solutions

One of the existing solutions consists of large ships pulling nets to fish out macroplastics and hence stop the formation of microplastics. But this is very expensive and also removes plankton from the ocean.

Analysis

"An estimated 110,00 tons of microplastics are formed by tire abrasion every year."

Daniel Venghaus, Technical University Berlin

Analysis

In order to identify in which urban areas most of the tire abrasion is formed, we conducted a exemplary study within Wiesloch – the town we live in. With this study we were able to identify the areas of usage for our filter.

Microplastics through tire abrasion are always formed when driving. How much exactly, depends on many factors like road condition, traffic situation (how often you have to stop and go) or the amount of precipitation.

Filter

Our idea

As part of this year’s competition of FLL - Hydro Dynamics we soon found microplastics to be a very large problem. During our extensive research, we found a study of the Danish environmental protection agency. It identifies tire abrasion as the largest cause of the formation of microplastics (65%). Next we got in touch with Mr Daniel Venghaus from the Technical University Berlin, who has been doing intensive research on the topic. He was able to confirm the relevance and the scope of the problem. His team had started searching for a solution about the same time as we did.

Function

This filter system is put into the catchment buckets and the street water rises inside of the water column until it flows through one of its holes. Now it can flow down inside and be filtered by the activated carbon filter. In case leaves or catchment block the lower holes of the catchment bucket, the water can still rise without blocking the filter system. In the rare occasion of blocked drain holes, the water rises and runs off from the emergency holes without being filtered - to prevent floods.

Construction

An aluminium pipe is inserted into a hole at the bottom of the catchment bucket. We also drilled holes into the pipe in regular distances, and a fine-mesh aluminium net is fitted on the inside. This net is helpful for cleaning the water from particles.

Our filter system for the catchment buckets

Our prototype

After designing our own filter system we built a very cheap test filter for experimental purposes.

Our prototype with material from the DIY store

Cleaning

The cleaning of our filter system is very simple. You can detach the activated carbon filter by a simple twist. Now all filters can be reactivated together. The catchment bucket can be cleaned with a simple water hose as it is usually done with normal catchment buckets.