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Could a wedge wire barrier provide a solution to ocean contamination?

Every minute across the globe, another truckload of plastic waste ends up in the ocean. Currently, over 8 million tons of plastic is dumped into our oceans every year. What can be done to help?

The propagation of plastic products over recent decades has been extraordinary. We, humans, appear addicted to plastic, producing over 300 million tons every year. And with a staggering 50% of the plastic we produce suitable only for single-use purposes – useful for just a few moments, but a burden to the planet for several hundred years – a feasible solution to the disposal of this material is long overdue. Every minute across the globe, another truckload of plastic waste ends up in the ocean. Currently, over 8 million tons of plastic is dumped into our oceans every year.

wedge wire barrier

A GLOBAL CONCERN

Anyone who has seen images on social media of the Indonesian republic, India and Myanmar using their waterways as part of their usual rubbish disposal system, or the Brazil clear-up of the bay prior to the Olympics of 2016, will understand the need for something to be done. The plastic waste we create is ending up in turtles and other creatures, killing seabirds and breaking down into microplastics that are consumed by fish – with an as yet unknown consequence for humankind. But how can the swirling mass of garbage be dealt with effectively if we are to secure the environmental future of the world’s oceans? Tackling this plastic waste is a tremendous job and will take more than one solution. A more ethical and mindful responsibility towards our waste is required, as well as alternatives to current plastics. In the meantime, technological advances in manufacturing can help aid the drive to decontaminate our oceans. But first, let’s take a look at some of the facts and figures around rubbish dumping in our waterways.

• 95 per cent of river-borne plastic flowing into the oceans comes from just ten rivers (eight in Asia and two in Africa)
• Large rivers with dense populations along their banks deliver a disproportionate amount of waste into the ocean
• The worst polluter is the Yangtze, in China, which releases 1-5 million tons of plastic waste into the Yellow Sea annually

On a positive note, clean-up operations have begun across the globe. A year ago, in Java, the beach at Muncar consisted of an uninviting mile-long stretch of sand several feet deep in food packaging, plastic bags, nappies and other plastic detritus. Bulldozers had already been brought in to clear and bury some of this vast mound of plastic, but with every tide more rubbish was being washed up – to say nothing of the tonnes of plastic washed downstream from towns and villages where citizens still emptied their waste into waterways as a matter of course. Once one of the most picturesque towns in Indonesia and a tourist hotspot, Muncar was at risk of being buried in plastic. An environmental disaster, and a source of economic damage to those who relied on tourism for their income. One year later, local government, working with international advisers, a recycling company and volunteers have worked hard in a race against time to stop the tide of plastic reaching the shorelines. A million-dollar clean-up is in operation, and eventually, the beach at Muncar will be clear again – but it could take years. Unfortunately, Muncar’s example is not being followed by all. Last year saw industries around the globe creating mountains of plastic for future generations to cope with, and coming close to losing the battle to keep global temperatures under control. One of the chief culprits is cheap shale gas from the fracking boom. This industry has grown, especially in the States, with recent investment taking place in new fracking plants that separate ethane from gas to produce ethylene – the building block of most plastics. And over the last decade, the petrochemical industry has invested about $200bn, and with $100bn more planned to be spent, plastic production is expected to grow 40% by 2030.

WHAT IS A WEDGE WIRE BARRIER, AND HOW COULD IT HELP?

Here in the UK, steps are being taken by the Environment Agency to improve rivers, with wedge wire barriers used across waterways. Studies have taken place in Cumbria, near Keswick, to ascertain the effectiveness, suitability and cost-benefit of the screen at a small hydropower scheme. The Coanda phenomena, first identified by Henri-Marie Coanda in 1910, is based on the principle of how fluids follow a surface. The research is explained by the EA report as follows: ‘A screen with 1mm bar spacings, it is capable of excluding all debris greater than 1mm and 90% of particles >0.5mm. Performance evaluation was carried out over 15 months with monitoring of screen capacity, silt exclusion performance, self-cleaning operation, slime and algae growth, operation and maintenance requirements, integrity and resistance to damage and cost-benefit analysis. After the 15-month period there were no noticeable signs of wear and at high flows up to 94% of suspended silt particles between 0.41 and 1.17mm. There had been no records of blockages by debris although it was believed that very thin strands of weed might pass through the wedge wires. After the 15 months, a thin film of algae had developed over the screen, resulting in some loss of capacity, although it was readily cleaned with a stiff brush. Overall the screen was found to be consistently robust, resistant and has a high-performance rating.’ A wedge wire barrier could have a clearing mechanism added to help counteract contamination of the world’s oceans. Certainly, it is worth consideration to help combat the ever-growing concerns of ocean contamination.