Summary
Every year, about 13 million tonnes of plastic waste ends up in our ocean. A majority of this waste is transported through rivers in Central America and Southeast Asia. Since resources to invest in waste management infrastructure is limited, people often simply throw their waste into the river. Additionally, flash floods occur frequently due to heavy rains. The water level rises rapidly and litter that is dumped along and in the river is transported with the high flow velocities. A general open question is how the transport of litter relates to river discharge. Does the concentration of litter increase in the run-up to a flashflood, increasing transport not only because of higher discharge? Or is the transport highest when river discharge is highest? In this TKI project, a modified design for an 'impact barrier' is applied in a smaller and in a larger river in Guatemala with the aim of removing litter from the river even during the extreme conditions of a flash flood. An 'impact barrier' is a floating vertical upstanding geotextile placed diagonally across the river. This directs waste to a river bank, where it is removed from the water with an excavator. By monitoring what is collected for a six months period, the aim is to have an answer on the open question on the litter transport during a flash flood. Water can flow through and underneath the 'impact barrier', preventing local flooding. With limited resources, plastic waste can be captured, sorted and recycled. Catching and sorting also creates jobs, where people can build a new future under good working conditions and equality, and improve the environment together.
Objectives
The objectives are:
1. Gain knowledge on how much and what type of floating waste is transported in the river in the course of a flash flood (from average discharge to extreme discharge).
2. Determining which part of the captured waste can be marketed in which way.
3. Improve the design of the 'impact barrier' 2.0 for long-term operational application for a smaller river and for the large Motagua river.
4. Evaluate the effectiveness of the 'impact barrier' 2.0 for both rivers. By good effectiveness, we mean that at least two-thirds of the floating debris is captured both during normal and extremely high discharge.
Preliminary results
At the urban river (Rio Escondido, left picture) we have taken out 15 tonnes of trash in the period May-August 2024. It consists for 25% of plastics on average. The PET plastic (11 % of total for this period) was sold to a recycler.
In the Motagua river (the largest river of Guatemala, right picture) the impact barrier was installed for a few days. An island of waste formed within days, consisting of about 50-100 tonnes of waste. Continuous litter collection is planned after improvements on the barrier.
