Igel Ball

An Igel ball, Igel being German for hedgehog, and the piece is also called a sea urchin ball, is a plastic biofilm carrier used to hold the bacteria that clean water in a treatment tank. It is made by fanning many slim plastic strips out from a common centre, so the ball ends up covered in soft, flexible spikes, much like a sea urchin. Like all biofilm media its purpose is to give bacteria a surface to live on: a film of pollutant-eating bacteria grows over the strips, and as water flows through the ball the biofilm strips the organic matter and ammonia out of it. What the sea urchin form adds is a lot of surface with almost no bulk, since the ball is mostly empty space between the strips, so it holds plenty of biofilm while letting water and air move through freely. It is used in the biological stage of water and wastewater treatment, where it sits in the tank, covered in its living film, quietly doing the cleaning.

It is about getting the most surface into an open, non-clogging shape. Bacteria treat water only where they can grow, so a biofilm carrier is really just a way to pack a large surface into a tank. A solid ball would offer only its outer skin; the sea urchin design instead splits the material into dozens of thin strips and spreads them out, so both faces of every strip become growing surface, multiplying the area many times for the same amount of plastic. Just as important, spreading the strips leaves wide gaps between them, so the ball is almost all open space. That high void means water and the air bubbles from aeration flow straight through the ball rather than around it, feeding the biofilm and keeping it supplied with oxygen, and it means suspended solids cannot bridge across and blind the media the way they can with a tightly packed filler. The flexible strips also flex in the moving water, which helps shed excess biofilm so it does not choke itself. Lots of surface, lots of open space, that is the point of the shape.

They are both plastic biofilm carriers, but they are different sizes and work a little differently. Small moving-bed media like K1 are little cylinders, a centimetre or two across, that grow their biofilm on a sheltered surface inside a protective cross and fins; huge numbers of them tumble freely through the tank, and the shelter is what keeps the biofilm from being scrubbed off as they collide. A sea urchin ball is much larger, often ten centimetres or more, and grows its biofilm on the outside, on its radiating strips; because it is big and its spikes are soft, it does not batter itself the way small hard media would, so an exposed surface works well. In practice, small moving-bed media suit tanks designed for a freely circulating, fully mixed carrier, while sea urchin balls suit larger, gentler installations and are often used where a bigger, easily handled carrier is wanted, sometimes held loosely in a zone or frame rather than filling the whole tank. Tell us your process and we will say which fits.

A sea urchin ball is made of plastic, usually polypropylene or polyethylene, chosen because it is light, durable, and unharmed by the water and the biofilm over a long service life. It is used in the biological treatment stage across municipal sewage works and industrial effluent plants: in aeration tanks, in contact-oxidation and biofilm reactors, and in upgrades where extra biofilm surface is dropped into an existing tank to lift its capacity. Wherever it goes, the job is the same, to hold a large, healthy biofilm in an open shape that will not clog. Because the listing supplied gives only the name, with no material, size or model, the details here are the usual ones for this kind of carrier; please confirm the material, the ball size and the quantity for your tank before ordering. Send us your tank and the treatment duty and we will advise the media and the amount.