Our oceans currently hold 165 million tonnes of plastic waste. By 2050, they are expected to contain more plastic than fish. The rivers that discharge this waste into oceans are themselves reduced to large drains, clogged as they are with insoluble trash which causes flooding upstream. For years, most municipal corporations had no means of capturing such solid riverine waste, apart from sending a few small boats out, which helped aggregate and collect small amounts of garbage. A new technology that has come as a rescue to many rivers in the last one year – floating trash barriers – have blocked over 22000 tonnes of waste entering into the rivers
Instead of hunting down floating trash by going after it in a boat, the water should bring the trash to a point where it can be collected. Since the floating trash barrier uses the natural flow of water, this model can be used to clean streams, rivers, storm-water drains, as well as some lakes with inflows and overflows.
It is pertinent to note that every tonne of trash and plastic thus removed is one tonne less reaching the ocean. By blocking the entry of trash into oceans in the first place, this method also acts a form of ocean clean-up. As AlphaMERS founder Captain Sekhar puts it, “this technology is like shutting the taps before mopping the floor”.
It is also cheaper to remove trash from the river which has clearly defined boundaries than collect it from the ocean, where it is dispersed by ocean currents far and wide.
Mechanism
The floating barriers are barriers made of steel and aluminium, which float on the surface of the water body. It is tethered to the sides of the stream and also anchored to the bed. It allows free flow of water below, and through it. The angle of alignment ensures that the natural flow of water causes trash to collect at one end, from where it can be conveniently collected for disposal. Its high tensile strength and robust structure, enable it to withstand the abrasive effects of incoming trash, as well as the corrosive effects of polluted river water.
This system works 24 x 7 and does not require energy for its operation, hence making it a low operating cost solution. One does not have to send a boat with fuel and crew to remove this trash from the river.
The collected waste is removed from the riverbank by excavators or conveyors. This technology ensures that wherever the barrier is installed, the spot is connected to a road. The excavators lift off the trash from the water and transfer it to trucks which in turn take it to municipal disposal facilities. Conveyors can also be used for the same purpose from riverbanks or sides of the streams. Although the amount of collected trash is large, it is still a small fraction of the citywide trash collection, and hence does not merit the setting up of separate disposal infrastructure. The collected trash contains water bottles, thermocol and even sofa sets and logs.
In Tuticorin and Bengaluru, a modified version has been installed in large storm water drains, which will remain standing even when the water level is almost negligible. It will float again when the water level rises.
This solution deals with surface trash and solid waste; dissolved pollutants remain in the water. However, as Captain Sekhar says, “this visually clean surface is often the first day of the turnaround story of the river or stream. This gives rise to some positivity and hope to revive the stream or river.”
Impact
Civic officials are very satisfied since this system has made their job easier and cheaper, and the downstream part of rivers looks, and is cleaner. They have the flexibility to schedule the removal of trash from the most convenient of locations every few days.
The floating trash barriers, introduced by AlphaMERS, have been installed at several locations across four cities: Bengaluru, Puducherry, Tuticorin and Chennai. Its installation on Chennai’s river Cooum alone has yielded over 22,000 tonnes of trash and almost 2,000 tonnes of plastic, in just one year. The technology also reduces litter on nearby beaches, carried by rivers and sea currents. It has stopped trash and weed from reaching the sea in Tuticorin, which has a fishing jetty downstream from the barrier. Fishermen have found that their boat propellers are not fouled up by trash anymore.
AlphaMERS has also developed a smaller version for small open drains running in between houses. This is designed to arrest solid waste and also has a safety feature that will prevent choke up and flooding of the upstream area in case of heavy downpour. This has been tested and certified by a city corporation after a two-month long pilot project.
