Removing the excess
Starting at home
Do you have a compost heap at home for your food and plant scraps? Bacteria love to eat these scraps, breaking them down into compost that can be used on the garden.
Sewage treatment plants also use garbage-loving bacteria. In almost every city, raw sewage is treated in processing plants.
Image courtesy of Photodisc
First, the solids are separated from the liquids and washed, dried and disposed of. Grit and sand are also removed. The liquid goes into a settling tank where most of the remaining solid material sinks to the bottom, this is called sludge.
Then, the bacteria are called in to do their job. Naturally occurring microorganisms break down the organic material and purify the liquid. They can either be encouraged to grow on stones over which the sewage is trickled, feeding on the sewage and purifying the water; or the process can be sped up using aeration tanks. Air is blown into tanks of sewage, where the suspended microorganisms feed on the waste.
The waste water is settled and sometimes given a final treatment using sand filters, reed beds or grass plots. Some sewage treatment plants also disinfect using ultraviolet light to kill bacteria.
Removing nutrients from waste water
In Australia, toxic blue–green algal blooms and red tides are responsible for millions of dollars' worth of stock losses each year. Run-off from farms and from livestock areas causes minerals and organic nutrients such as phosphorus and nitrogen to build up in rivers and lakes. This causes eutrophication; algae proliferate and quickly use up much of the dissolved oxygen in the water, killing other aquatic organisms.
Eutrophication is a well‑recognised environmental problem worldwide. To combat it, tough standards on nutrient discharge are in place. Industries are also researching biological nutrient removal (BNR) systems to treat their wastewater before discharging it into rivers.
Biological treatment is by far the cheapest and most environmentally‑friendly way of removing nutrients from wastewater. Existing methods involve microorganisms that work together to take out nutrients from the water. However, they are not reliable enough to do away with the use of chemicals altogether.
As an example, removing high levels of phosphorus from wastewater requires a large quantity of expensive chemicals. Furthermore, additional (chemical) waste sludge is generated in the process. Scientists are working on ways to use laboratory-‑grown microorganisms to remove nutrients from wastewater.
Reducing nitrogen use in sugarcane farming
Cooperative Research Centre for Sugar Industry Innovation through Biotechnology
Australian cane growers spend more than $80 million on nitrogen (N) fertiliser each year. After heavy rains, fertilisers get washed into river systems; N fertiliser is considered a major threat to surrounding ecosystems.
Much of Australia's sugarcane is grown along coastal regions bordering the environmentally‑sensitive Great Barrier Reef and World Heritage rainforests.
Researchers at the Cooperative Research Centre for Sugar Industry Innovation through Biotechnology (CRC SIIB) are examining ways to reduce N application in sugarcane fields without reducing productivity.
Compared with other sugarcane cropping systems around the world, Australian sugarcane production uses a high level of applied N fertiliser. Some growers exceed industry recommendations for N application, in the hope of improving crop performance. Researchers are identifying traits in Australian and overseas cane varieties, and in ancestral species, that make sugarcane use N more efficiently. This should increase the sustainability of the Australian sugarcane industry.
Sheep vaccine for more wool, less burps
One-fifth of the world's methane emissions come from farm animals belching, farting and exhaling. Methane-producing microbes, or methanogens, are opportunistic organisms that live in a sheep's gut, providing no benefit to the animal. The methane they produced is released into the air when sheep burp.
CSIRO researchers have been developing a vaccine that targets the rumen microbial organisms — protozoa — that reduce the flow of protein to the animal's small intestine. By reducing the protozoa population, more protein would be available to the animal for growth, meaning more wool production.
As an additional environmental benefit, the researchers think the vaccine might reduce methane-producing organisms located in or on the protozoa, thereby reducing methane emissions from belching sheep.
More information: http://www.csiro.au/news/psls.html