Drinking your own waste is probably nobody’s first choice, but it may be necessary to our future food security and critical to our survival.
In fact, recycled wastewater, a pleasant term for human sewage, is the fastest-growing area in the water industry because not every city has an ocean, good lakes and rivers, but everybody’s got sewage. Furthermore, we are left with not many options as we are running out of water from other sources, we are over pumping groundwater, and we have already built more?dams?than we can afford economically and environmentally.
So, how do we recycle wastewater? First, you have to filter out all of the solids in the water. Then, in a process called reverse osmosis, you filter out the tiniest of particles. RO is a method that simulates the biological process that happens within our cells as fluids flow across semipermeable membranes: in this case water, containing dissolved salt molecules, is forced through a semipermiable membrane (essentially a filter), in which the larger salt molecules do not get through the membrane holes but the smaller water molecules do.? After this process, as an extra precaution, the water is often flashed with ultraviolet light to sterilize pathogenic microbes. As a result, the purity you get with water recycling is quantifiably better than the water you get from the tap, better even than some bottled water. Furthermore, while tap water is often treated with chemical coagulants and chlorine, reverse osmosis filtration used in water recycling cuts the need for those chemicals.
Still, for some people no matter how much you tell them the water is safe to drink, the feeling of disgust is too much to overcome. To minimize this feeling, some water recycling plants are using a “psychological” approach that consists of pumping recycled wastewater into aquifers to replenish the ground supply. The aquifers provide free storage, which?would otherwise be?expensive, and?even though the water is already drinkable,?some?people feel?the water gets naturally purified through the ground.
There is also another source of water supply, maybe less controversial than recycled wastewater, but way more expensive – seawater desalination. Desalination?is one of mankind’s earliest forms of water treatment, and it is still a popular treatment solution throughout the world today. In ancient times, many civilizations used this process on their ships to convert sea water into drinking water. Basically, the desalination imitates a process found in nature called water (hydrologic) cycle. We all learned about it in biology class: the sun supplies energy that causes water to evaporate from surface sources such as lakes, oceans, and streams. The water vapor eventually comes in contact with cooler air, where it re-condenses to form rain. However, desalination can have a negative impact on some ocean ecosystems if ocean creatures like baby fish or plankton get sucked into desalination plants, upsetting the food chain. Good news is that the improvements in the pumps, pipe design and membranes have cut the total amount of energy used in desalination by about half in the past two decades.
At some point in the future the water production could become a closed-loop system in which all the used water is recycled.