North River Wastewater Treatment Plant in New York City with a boat. Image courtesy of Wikipedia Commons

Every time people use water, it goes back down the drain less purified and clean than it was when it came out of the faucet. People, especially in the United States, take water accessibility and purity for granted so it is easy to forget about the implications of polluting water after use. While water may appear to be clean, it is often times contaminated with micropollutants after human use.  Micropollutants are widely misunderstood because they are not easily found or observed. They are organic, mineral, or synthetic substances that accumulate in the environment and can have a negative affect on organisms because of their toxic nature. This definition exemplifies the “pollutant” part of micropollutant, but micropollutants are also characterized by the small size. These substances are found to be as small as a few atoms that make a molecule to as large as 5 mm in diameter. Three types of pollution that were previously discussed in depth are pharmaceuticals, antibacterial active ingredients, and microplastics.

How is wastewater filtered? In New York City, there is an extensive wastewater treatment system that has the water go through five processes. Wastewater first passes through a very large filter that blocks mostly garbage, including plastic waste, paper, and cans. Then the water is allowed to sit for a couple hours so that it naturally separates into substances that sink and float. The material that sinks is called sludge and it is removed for treatment elsewhere. The floating contaminants, usually oils and small plastics, are also removed. The wastewater then continues to the third step in which air is pumped through the tank so that bacteria can break down some of the organic materials.   After aeration, the water is allowed to sit and separate, as previously done. Finally, the remaining water is disinfected with chlorine and released into local waterways. Although this process is efficient at removing between 85 and 95 percent of pollutants, it does not address micropollutants.

While the general public unknowingly pollutes the water, large companies, factories, and institutions are also responsible for micropollutant contaminations in water that is released into the environment. For example, hospitals are becoming the major source of pharmaceutical micropollutants when medication is improperly discarded. When testing used hospital water, in addition to pharmaceuticals, radionuclides, solvents, and disinfectants are often found. When the wastewater treatment facilities are not specialized to deal with this volume of micropollutants, it is inevitable that some of the chemicals are going to end up in the environment. In general, other sources of water pollution are from factory farms, industrial plants, and fracking.

          While there are rules and regulations for these industries and their treatment of water, the water ultimately released back into the environment is still contaminated due to emerging pollutants.  Emerging pollutants are pollutants that are not yet regulated because the concentrations in the environment are still considered low. Many pharmaceuticals and active ingredients fall under this category. According to Christian Daughton, a researcher at the National Exposure Research Laboratory in Las Vegas, “For any sample collected from the environment, a large (but unknown) portion of its organic constituents are not (or cannot) be identified.” Because little information is known about the toxicity of these unknown micropollutants in water, it is difficult for scientists to propose new pollution regulations for wastewater treatment, even though these pollutants are accumulating in the environment.

In order to improve water filtration and purification in wastewater treatment, there needs to be additional processes added to ensure that micropollutants are effectively removed. New suggested filtration methods focus on the chemical properties of the micropollutant to help remove the contaminants. Two types of wastewater treatment options are activated carbon adsorption and membrane technology.

            Activated carbon adsorption is a technique that works when water passes through carbon powder or granules. This technique works like ocean water travelling through a sand column, which allows for the seaweed and seashells to stay on top while only the water passes through, just on a microscopic scale. Membrane technology is a similar concept, except that the water travels through a thin membrane with very tiny holes in it that allow for only water to pass through. Although there are different sized membranes, nanofiltration membranes are best for removing micropollutants in water. These techniques are not perfect and will not get 100 percent of all micropollutants, but they are definitely a step in the right direction.

           While it will take a while for these new techniques to be implemented in existing water treatment facilities, the general public can help reduce the amount of micropollutants entering the water after household use. For example, there are proper ways to dispose of medication that prevents it from getting into water sources. According to the Associated Press, in order to properly discard old medication, the prescription drug should be mixed with used coffee grinds, cat litter, or another substance equally undesirable. The mixture should then be put in a bag or container and discarded. Sometimes, there are pharmaceutical take-back programs that will take unused medication. Also, some medication has specific directions to be flushed down the toilet; these drugs do not have known micropollutant tendencies. Other ways to avoid adding micropollutants to water accidentally is to avoid purchasing products, such as facial washes with plastic exfoliating beads or antibacterial soaps, that are known for contaminating streams and rivers.

            It is important for these new filtration techniques to be used, not only to protect the environment, but also to protect humans. Once wastewater is treated and put back in the environment, other towns and cities downstream may use this water as drinking water. By protecting the environment, improved wastewater techniques also help ensure that people are also avoiding harmful micropollutants.