GREEN would like to welcome guest writer Christopher Olivares. Olivares is a graduate student pursuing a Ph.D. in environmental engineering at the University of Arizona (UA). Originally for Mexico City, he works with biodegradation of nitroaromatic pollutants in soils and thinks that biological-based technologies are one way to a more sustainable and green world. Outside the lab, he is part of the Tricats Triathlon club at UA.
In 2007, the British Medical Journal asked its readers to vote for the largest medical breakthrough since 1840. Vaccines, anesthesia and the discovery of the structure of DNA placed very high, but the number one voted was “the sanitary revolution”; the access to clean water and sewage disposal.
The sanitary revolution brought on by water and wastewater treatment, along with education and other medical advances, has increased life-expectancy from 45 to 70 years from 1840 to 1850 in the longest lived countries of that time. Sanitation has reduced pathogen-caused epidemics, such as cholera outbreaks, as well as the reduction of pollution by metals and other pollutants. Treating water and wastewater is important because someone is always downstream of someone else and because water is a limited resource, we need to put it back to the environment for future use.
To treat sewage, wastewater treatment today uses a combination of physical, chemical and biological treatments that are effective for removing inorganic and organic pollutants, as well as disease-agents. While the details involved in wastewater treatments vary depending on the common type of pollutants found in the water, there are three main treatment stages in an ordinary municipal wastewater treatment plant. In general terms, primary treatment removes physically particles, secondary treatment uses microbes to clean out organic pollutants in water, and the third step disinfects the water.
Even though the basic scheme of treatment has been pretty well established, there are some areas that can improve wastewater treatment technologies to make them more green and sustainable.
1. Cogeneration in wastewater plants
The secondary treatment – which is biological – generates a sludge rich in organic compounds. This concentrated sludge is sent through a process called anaerobic digestion, where anaerobic bacteria will eat the sludge. As the anaerobic bacteria eat the sludge, they generate biogas – a combination of methane and sulfide. This biogas can be used as fuel to power the wastewater treatment plant and reduce its dependency on the electrical grid. This process is called cogeneration.
Another opportunity in wastewater treatment systems with anaerobic digestion is to create valuable goods from what would otherwise be waste. The waste produced by anaerobic digestion can be used – after being treated to kill all pathogens – as fertilizer; however, another product could be bioplastics. Some microorganisms, such as those from the Actinobacteria group, can store polyhydroxyalkanoates (PHAs) when they do not have access to inorganic nutrients. They store PHAs just like you and I store fat in our bodies. PHAs can be used as plastics, and best of all, are biodegradable.
3. Natural biological systems
There are other treatment methods – some of which are less power intensive and more affordable that could represent another possibility to treat wastewater; for example, constructed wetlands. Constructed wetlands are ponds – or sometimes subsurface systems as well – where water flows and interacts with plants, roots, microbes, fungi, etc. These processes are effective for removing biodegradable organic pollutants and high levels of nitrogen from water. However, there are sometimes long retention times, and a large piece of land is required to work.
4. A new vision for wastewater treatment?
Organica is a Hungarian-based company that could reshape the image of wastewater treatment. They propose a solution combining current wastewater treatment, in addition to a natural-based system using thousands of species (microbes, plants, fungi, snails and worms) to treat water. Besides treating water, they can change the typical face of wastewater treatment – a smelly industrial complex – to a recreational natural park, where people could learn about wastewater and the importance of sanitation.
Wastewater treatment and sanitation are revolutionary health advances within the last 170 years. Although some of the processes are well established, there is room to make wastewater treatment approaches more green and sustainable.
More information (sources):
Bosco, Francesca, Chiampo, Fulvia. (2010). Production of polyhydroxyalcanoates (PHAs) using milk whey and dairy wastewater activated sludge Production of bioplastics using dairy residues. Soc. Biotech. Japan
Ferriman, A. (2007). “BMJ readers choose the “sanitary revolution” as greatest medical advance since 1840″. BMJ : Brit. Med. J. 334 (7585): 111.
Kirkwood, T. B. (2008). A systematic look at an old problem. Nature, 451, 7179, 644-647.
Nikodinovic-Runic, J., Guzik, M., Kenny, S. T., Babu, R., Werker, A., O Connor, K.E. (2013). Carbon-Rich Wastes as Feedstocks for Biodegradable Polymer (Polyhydroxyalkanoate) Production Using Bacteria. Advances in Applied Microbiology, 84, 139-200.
US EPA. (1993) “Constructed wetlands for wastewater treatment and wildlife habitat” EPA832-R-93-005