MULTI interns develop Multi River Cleaner

Niels Selleslags and Mats Weemaes, two Design and Production Engineering students, have spent their internship at MULTI.engineering designing an innovative system for removing waste from rivers and canals without negatively impacting shipping traffic or aquatic life. Watching them grow and coaching them turned out to be quite inspiring. Niko Fierens, our Operations Director, spoke with Niels and Mats about their project and their time at MULTI

WHERE DID THE IDEA FOR YOUR BACHELOR’S PROJECT COME FROM?
Mats & Niels: It was a public tender from the “Vlaamse Waterweg” (Flemish Waterway), on which MULTI wanted to bid. The idea was to develop a prototype waste collection system for use in Flemish inland waterways.

Karen Merlevede (Assistant design engineer manager) discussed the assignment with us and Bart Wilbers (Lead Engineer/Sales Engineer) was our coach. This made the project a combination of our own ideas and those of our colleagues at MULTI.

WHAT WAS YOUR FIRST IMPRESSION OF THE SUBJECT MATTER?
Mats: Very positive, because of its great relevance. It was a lot of fun to work in this area and to make a contribution to society in the process.

Niels: I was fascinated, albeit initially overwhelmed, right away. So you wonder at first where to even start, but then you roll up your sleeves and get to work. And while I had done some research prior to my internship, practice is an entirely different animal. For instance, it soon turned out that I had to scrap several ideas, because they were not going to meet the requirements. In addition, there were frequent conflicts between our numbers and the scientific literature: for example, there is no consensus about exactly where river waste is located – whether it floats, hovers or collects on the riverbed – and about whether a bubble curtain interferes with aquatic life or not. So that was one thing to take into account.

AND SO YOUR LITERATURE STUDY AND RESEARCH LED YOU TO OPT FOR THE BUBBLE CURTAIN METHOD.

HOW DOES THIS WORK?
Mats: It is a system that pumps pressurized ambient air through a perforated line onto the river or sea bed. The air bubbles escaping out of the line push the waste on the riverbed and any hovering waste up to
the surface. There, the bubbles keep the waste from being carried away by the flow by guiding it into a funnel

IS THIS METHOD ALREADY IN USE?
Mats: Yes, bubble curtains are being used to contain any oil spills during the loading of oil tankers, for example. It is also already being used in Australia as a barrier between seabed drilling sites and marine life (underwater noise levels being one consideration

Niels: This system was already used at an estuary lock in the Netherlands as well, to counteract river salination. The advantage of a bubble curtain is that, in addition to having no damaging effect on animal life and vegetation, it also does not interfere with shipping traffic. One concern, though, was the interaction between a ship’s propeller and a bubble curtain.

However, these risks have since been researched extensively, with positive outcomes in terms of both health and safety.

HOW DID YOU CONDUCT AN OBJECTIVE ANALYSIS AND COMPARISON OF AVAILABLE TECHNOLOGIES?
Mats: Rather than conducting a qualitative evaluation and description of our findings, we opted for the “MoSCow method”. It distinguishes between “Must haves”, “Should haves”, “Could haves” and “Would haves”. A few criteria that the system had to meet had been defined in the original recommendation. We expanded this set of criteria further. A quantitative analysis resulted in a total selection of 14 different systems. And our concept came out on top.

AND WHAT WAS THAT CONCEPT? 
Mats: We ended up combining and finetuning two techniques in our design: the bubble curtain and the “Mr. Trash Wheel” from Baltimore. The Mr. Trash Wheel is a kind of comb that removes floating waste from the water. This system is used on water with a natural current.

The downside of this system is that it only collects waste floating on the surface, whereas the tender specified filtration of the top 50% of the water column. By combining the Mr. Trash Wheel with the bubble curtain, we managed to solve this problem. Given the set criteria, our design is undoubtedly the best solution.

WHAT DID YOU DO ONCE YOU HAD SETTLED ON THE CONCEPT?
Mats & Niels: We started with two basic concepts, the first being the “bubble boat”, a kind of “robotic vacuum cleaner”. This was an autonomous pontoon that actively looked for waste. We abandoned that, however, because of insufficient efficiency and robustness. A fixed, current-based system proved to be a much more efficient solution. So we fleshed out this idea, the “bubble barge”, without losing sight of our criteria: speed, ecology, simplicity, robustness, maintenance-friendliness and cost, in terms of both construction and operations.
We drafted our concept in Inventor and Solidworks, prepared strength calculations for all structural components and determined energy requirements by calculating a power balance. In addition, we researched the most suitable materials and paint systems.

DO YOU THINK THAT THIS BUBBLE CURTAIN CONCEPT WILL EVER BE USED?
Mats: It is already being used in the Netherlands, for removing waste from a river in Wervershoof. Granted, it is only a narrow river (about 5 m or 15 ft. wide), with no shipping traffic. Our design, which we have named the “Multi River Cleaner”, is designed for much larger rivers. I am confident that other studies will further confirm the strength of our MRC concept.

This I can say with 100% certainty: our research into the parameters of this problem has been so thorough and our solution was developed in such detail that I can’t imagine there being any better options.
Niels: Whether our design will ever be used is a good question. Regardless, it is the ideal system within the set criteria and no better alternatives are currently available for the collection and removal of waste from our waterways.

WHAT MAKES YOUR SYSTEM SUPERIOR TO OTHER EXISTING SYSTEMS?
Mats: Its simplicity and modular nature. Every component can easily be exchanged or omitted. Beyond that, it is a simple system, whose operation and maintenance require no highly-trained personnel.
Niels: The combination of the bubble curtain and the green energy balance is a unique idea. We have calculated the power requirement for the compressors and the waste stream drive engines, and by installing solar panels and vertical axis wind turbines (Waldemar Piskorz style), we have managed to generate sufficient autonomous power to make the system energy neutral. All subject to sufficient availability of solar and wind energy, of course.

WHAT HAS YOUR WORK ON THIS PROJECT TAUGHT YOU?
Niels: We were able to find many practical applications for our theoretical knowledge: strength of materials, mechanics, materials science, 3D CAD design, production techniques, mechanical and electrical engineering, mechanical maintenance, 3D printing, etc. But we have learned quite a few other things as well.

Mats: I myself, for example, am rather impulsive, and tend to make snap decisions. Niels takes a bird’s eye view of the situation first. Working Niels’s way keeps things from blowing up (laughs). We have met a lot of people from the corporate world as well.

Everybody has been very enthusiastic and eager to help, from academic researchers all the way to US-based entrepreneurs!
Niels: Since we have different personalities, we approach particular situations differently. Giving each other feedback and clearly defining tasks yields better results.

WHAT WAS YOUR FAVORITE MOMENT DURING YOUR INTERNSHIP?
Niels: The day we tested the bubble curtain in MULTI’s pond.
You come up with an idea, you put it together and then you go and do a real-world test.
And then, when everything actually works as it is supposed to, that is the best. We made a video of this live experiment: https://tinyurl.com/bubble-curtain.

Mats: I really enjoyed the atmosphere at the office. You could always ask people questions, and absolutely everybody was interested. We got lots of spontaneous feedback. Everybody was eager to make their own specialized contribution. That really makes you feel appreciated. 

WHERE DO YOU SEE YOURSELVES IN TEN YEARS?
Niels: First, I am going to continue my studies. After that: who knows. I would prefer to find a good job that I enjoy doing. And a great work atmosphere, at a company where I can be happy.

Mats: It’s the same for me. A great job working with a good team and a boss you can talk to, just like at MULTI. And I hope to see our Multi River Cleaner on our rivers one day. I really see the MRC as a meaningful contribution to the world, and I am very proud of that.