/How can we separate oil and water during an oil spill
water-oil separators

How can we separate oil and water during an oil spill

With much of the world moving towards renewable energy, dealing with oil is becoming a less frequent occurrence. But if you do use oil in your manufacturing process (lubricant, coolant, cutting fluid, vegetable oil, hydraulics, engine oil etc.), you’ll have the occasional slip-up. The scale differs though. Most of the time, when the phrase ‘oil spill’ is used, it’s a marine scenario. The oil may have leaked into a river, lake, sea, or ocean, washing up on the beach.

In such cases, the primary task is getting the oil off the beach, and maybe washing marine creatures to get the oil slick off their bodies. Animal-friendly detergents like Dawn are good for this. Then there’s the broader issue of getting the oil off the water itself. Early in 2018, the University of Southern California came up with a solution based on salvinia (floating fern). They combined this marvel from nature with the latest 3D printing technology.

Using their printers, they generated a filtration membrane that imitates the organic make-up of salvinia leaves. One particular species – the salvinia molesta – is native to South America. It ‘lives’ in water but keeps itself dry by forming an air pocket around its leaves which keeps water molecules away. The bubble is created by fine hairs that grow out of the leaves, and the bubble gets activated whenever the leaf is submerged.

Inspired by nature

Researchers at USC combined carbon nanotubes and plastic to reproduce patterns which resemble the salvinia leaf’s microstructure. (It’s described as ‘something that looks like an egg-beater’). This microstructure uses capillary to absorb oil while repelling water, making it the perfect separator. Other uses include DNA sequencing, chemical synthesis, cell cultures, drug discovery robotics, microfluidics, tissue engineering, nanoparticle synthesis, and drug delivery.

So far, the fabric has been screen-printed on a small scale, but eventual applications will include employing robotic arms as medical delivery tools. These robotic arms can also be used to manipulate blood and other fluids during blood analysis and other blood tests. The idea is to precisely transport minuscule amounts of fluid, which is essential when only a small test sample is available. Meaning test subjects will have to offer far less blood for medical evaluation.

If your oil-spill is more garden-variety (e.g. in a factory), you can use filtration membranes to sop it up. You can use a filter material roll like Rapid 200. This spill kit is easy to rip off its roll, but it has the capacity to absorb 3 litres for every square metre. (A roll of 1000mm can hold 150 litres of oil.) The problem is it absorbs both oil and water, so it’s not ideal for separating the two – unless you can somehow float it above the water body, letting it absorb the top layer of oil without getting too much of the water. That requires magician-levels of manoeuvrability.

Perpetual separation

A better option is to use an oil skimmer. It can lift spilt oil off the surface of a water body at about 10 litres per minute. It’s generally used to get oil out of drains, wash pits, or water tanks. It can also be used to separate water from coolants and cutting fluids.  Surface oil skimmers comprise a synthetic belt whose ‘tail’ is submerged into the mixed liquid. The oil is attracted to the belt and sticks to it, and the belt itself is tied around a rotating pulley.

As the belt rises – with the oil stuck to it – the belt passes through wiper blades that scrape the oil off the belt and collect in a sump. This oil can then be filtered and recycled or safely disposed. You can attach varying belt lengths depending on your needs. And because the rotary head on the pulley runs unaided, you can filter your oil continuously, without stopping your machinery or risking any downtime.

If the liquid mixture is in a factory setting rather than a larger water body, you could collect the mixture and feed it into an oil centrifuge that will separate the two liquids. In some water-oil separators, the denser water droplets sink to the bottom and are released through a small tap while the oil flows out of the top. The equipment includes a water sensor that beeps and flashes whenever it detects water, alerting the machine operator, who will open the water tap.

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