Algal blooms happen when waste water from farms, factories and dwellings carries large amounts of normally scarce nutrients like nitrogen, potassium and phosphorous into rivers, lakes and seas. Algae, often unicellular ones, lap these nutrients up and breed like billy-o. These blooms are occasionally dangerous, if the algae involved are toxic, and are generally regarded as undesirable. But what if it were possible to control an algal bloom, and use it to absorb such nutrients before they escape to the wider environment?
That is the idea behind a technology developed by Algal Scientific, of Northville, Michigan. Algal’s researchers are not the first to try to control pollution with algae. But they think they are the first to have succeeded in a commercially viable way, for they have installed a plant at the Budweiser brewery in Idaho Falls.
Cleaning up waste water with algae is an old idea, and the fact it has never really worked before is curious. Geoff Horst, Algal’s boss, reckons that the problem, paradoxically, is that the town sewage to which it has hitherto been applied is not dirty enough. The usual approach has been to rely on photosynthesis to feed the bugs, which then suck the nitrogen, potassium and phosphorous out of the water as they grow. But photosynthesis requires sunlight. Lots of it. That means decontamination plants need to be shallow ponds stretched over huge areas of land. And that is expensive and hard to manage.
Some algae, though, can get away without photosynthesising, by drawing food directly from the surrounding water—assuming this is rich enough in organic matter. And brewery waste is rich in precisely the sorts of organic matter (sugars and so on) that these bugs love. Moreover, without the need for sunlight, the process can be conducted in tanks of the sort breweries are used to. That makes building and running the system a lot easier.
Dr Horst’s other clever idea is to use not an algal monoculture, but rather an entire miniature ecosystem of his own creation. Some bugs hoover up the nutrients. Others are predators, there to eat bacteria which might otherwise run riot and overwhelm the nutrient-absorbing algae. Getting the mix of critters right took years, and its composition remains a secret—beyond the fact that none of the organisms involved is genetically modified. But Dr Horst’s artificial ecosystem now seems more than happy bathing in brewery waste.
Moreover, it may even turn a profit. Obviously, the algae have to be harvested periodically. Dumping them would simply move the problem from one place to another. Dr Horst, however, proposes that they be dried and sold as fertiliser or animal feed. This will put the scavenged nutrients into organisms that will help humanity, rather than hurting it.
View original article at: An artificial ecosystem should help purify the effluent from making beer