Microbeads: capture is not the real issue
Microbeads - a global environmental issue
The media has been full of the dangers of microbeads over the past few months, and the environmental issue has led to a ban on microbeads in the United States (the Microbead-Free Waters Act of 2015). Canada is close on its heels, and the Netherlands has already announced its intent to be free of microbeads in cosmetics by the end of 2016.
The change from organic ‘polishing’ ingredients – such as sugar, pumice, oatmeal and walnut husks – to polyethylene, polypropylene and polystyrene has meant that most of the world’s waterways are now contaminated with as many as 43,000 microbeads per cubic kilometre of water. Greenpeace claims that 8 million tonnes of plastic is dumped into the seas every year, some of which ends up in the fish we eat. A 2015 study published in Environmental Science & Technology found that for every litre of final effluent leaving a works in the US there will be seven microbeads.
That equates to 8 trillion microbeads every day!
But how are these microbeads getting through our treatment systems and into our rivers and seas? The legislation that is being imposed will restrict the use of microbeads smaller than 5 mm, but that is far larger than should be getting through our works anyway.
Microbead capture in wastewater treatment plants
The beads used in our bathroom products range in size from 5 to 1,000 microns. They are designed to be neutrally buoyant and therefore well mixed and suspended within the liquid; something that would be difficult with a natural ingredient without rigorous shaking. The traditional methods of treatment require particles to settle, otherwise particles will carry on straight through the treatment process until they reach a physical barrier such as a membrane.
There are plenty of membrane technologies out there that can capture this hazardous waste. Hydro International have recently introduced the Hydro MicroScreen™ which is capable of removing particles down to 20 microns, and also markets the DynaDisc in the UK with 10 micron membranes.
As we know through our research into fine grit, any particle in a wastewater stream will acquire a coating of fats, oil and grease (FOG) that will further affect its density, causing it to float and therefore enable it to be skimmed off the surface of tanks for diversion to digesters.
Capture is only part of the story
So microbeads may be captured during the wastewater treatment process. The real issue, however, is that once you have captured them, what do you do with them?
It is estimated that 99% of microbeads that are retained at the works settle into sludge that is subsequently spread on the land, and which will eventually end up in the aquatic environment. Therefore the only realistically feasible options are to incinerate, or to send the microbeads to landfill. Neither is an ideal solution.
Many manufacturers and retailers are reacting to environmental concerns and have vowed to remove microbeads from their products over the next 18 months. The UK Government is now under pressure from environmental pressure groups to follow the lead set by the US.
Hopefully the growth of this problem will wane rather quickly, but with huge amounts of microbeads already in the environment the long-term effects may still not yet be evident.
Keith Hutchings is Group Wastewater Product Manager at Hydro International.