The world-wide best approach is found in Baltimore Harbor  as part of the city’s effort  of reviving the harbor. This solution is running on a water wheel powered mechanic. It fulfills Req. 1,2,3 and 8. The sought ‘River Cleaning Device’ was found through research in a National Geographic Documentation . This role-model for the mechanical solution to retrieve the majority of the floating garbage was installed in 2014 in Baltimore's Inner Harbor, clearing debris before it enters the Chesapeake Bay.
1,232.67 TONS of trash and debris has been pulled out of the water by the installed units (dubbed ‘Mr. Trash Wheel family’) by the time of this document (Oct. 2019).
John Kellett constructed the first unit in 2008 by essentially combining basic mechanical components from around 4000 B.C. (Water Wheel ) and the 18th century (conveyor belt ). This simple solution runs without fuel or electricity and is therefore highly sustainable, practically carbon emission free and – most importantly – highly affordable in poor Countries
 THE PEOPLE V. CLIMATE CHANGE / Baltimore’s success with Mr. Trash Wheel and Professor Trash Wheel may spread to other cities. Feb. 2017
As described in a Laboratory Report  from 2018 by students of the Negros Oriental State University the current turns the water wheel which drives the conveyor belt to lift the garbage out of the water.
In Baltimore Inner Harbor the trash situation was severe  and could completely be solved after the installation:
"The most visible, perhaps the only,
successful engineering-based ocean cleanup project, tried and tested"
Andrew Thaler, Deep-sea Biologist
Universally celebrated by scientists, and citizens, they are arguably the most beloved and sensible anti-plastic-pollution mechanisms in the country.
The New Yorker
There is one effective engineering solution
to the prevention problem: Mr. Trash Wheel
Examples like Baltimore Harbor’s Mr. Trash Wheel provide a blueprint
for effective ways to prevent trash from reaching our ocean.
Baltimore’s harbor is cleaner than it has been in decades
thanks to two anthropomorphic trash wheels pulling debris from its waters.
While Mr. Trash Wheel is definitely the best upstream cleaning solution at the moment, there are certain specific topics to be discussed.
Restrictions and Differentiation
This system in Baltimore is a very sophisticated engineering product with technical specialties as for example a solar driving pump system for situations in which the current is not enough to turn the wheel.
The cost of this high-tech construct has been estimated at $850,000 to build and install and a whopping $150,000 operating costs average per year– clearly not the ballpark figure we are aiming for in underdeveloped countries. Obviously, a solution must be found which is targeted at using local materials, simpler constructions and far less high-tech.
One attempt has been roughly calculated by a group of engineering students around Dr. Craig Narzabal Refugio from Negros Oriental State University Philippines, led by Chito S. Briones . They built a very basic prototype with locally available materials:
They came up with estimated cost of approximately US$ 43 (Table 1, BrionesetME425.pdf). Their system though has a much too small container which is also not exchangeable – a must when a continuous operation is planned. It also lacks a sophisticated raking/forks system, which seems to optimize the results drastically.
Lessons learned and the adapted version
One important lesson learned through the Baltimore project is the fact that the rain is bringing a lot of trash with it. Kellett said it’s a common misconception that most trash comes from people chucking things directly into the water. Instead, it comes from litter thrown out of cars, illegal dumping, and cigarettes left on the ground. When it rains, all that junk ends up in the watershed, where some of it eventually makes its way down to the harbor.
“If it rains, there is always trash,”
JOHN KELLETT, CLEARWATER MILLS;
WATERFRONT PARTNERSHIP OF BALTIMORE
This means that rain and the connected swelling of the river will result in a high retrieval rate – which leads to the conclusion that a low current (which will not turn the wheel) is not important – as long as in the South East Asian Monsoon periods the machines can work at full efficiency and retrieve all the material which otherwise would have been washed into the ocean.
Logically a construction with a cost level of multiple hundreds of thousands of dollars is not feasible. Instead the goal must be to construct a similar solution with local materials and a much lesser effort. Think of a “Jungle Wheel” version. It will be built with locally known strong materials and constructed in a way that every Municipality can easily set up multiple Plastic Plugs. We aim at a DIY building guide which can be easily adapted by local entities.