Sewage Further Explained-JL

All of the wastewater produced by a city eventually ends up being dumped in a body of water. Before it reaches the water, the wastewater goes through a sewage treatment plant, which removes up to 90% of biodegradable organic wastes. After this, the sewage continues to a sedimentation tank, where any remaining solids and organisms settle as sludge. The sludge is most often dumped in the ocean. This sludge has a very high concentration of toxic substances and microorganisms, which have a large demand for oxygen. It contains large amounts of suspended solids, nitrates and phosphates, and toxic metal compounds. It significantly alters the biological composition of areas of sea floor where it is released.

            When the toxic substances in sewage sludge enter a body of water, they dissolve, become suspended in the water, or get deposited on a shore. Sewage-contaminated water can cause eutrophication, killing many of the organisms living in the water through lack of oxygen. The sludge also contains disease-causing microbes, and some gastrointestinal disorders have been linked to sewage pollution. Shellfish strain water through their gills as they feed. If the water is contaminated by disease-causing bacteria in the sewage sludge, they could be consumed as food by the shellfish. If people eat these shellfish raw or partially cooked, they could become seriously sick. Sewage water is known to carry diseases such as dysentery and cholera.

            There are also many economic disadvantages to sewage dumping. Debris from sewage on beaches results in loss of tourism and requires an additional cost for removal. Also, high income loss can result from the closing of commercial shellfish beds that have been contaminated by sewage.

            A study conducted by the National Undersea Research Program (NURP) examined the effects of sewage dumping on marine organisms’ biodiversity and the transport of contaminants back to humans. They documented the impact of 42 million tons of sewage sludge dumped off of the Mid-Atlantic coast between 1986 and 1992. They found that the sludge significantly affected the metabolism, diet, and composition of the organisms present. They also found that the sludge became mixed with the sediment at the ocean’s bottom and could therefore remain there for a very long time.

            The solution to sewage pollution can be in a treatment plant or in nature. Sewage treatment plants work by relying on bacteria that eats away nitrates, phosphates, and organic matter found in sewage. However these plants can be expensive to build and operate for many governments. A cheaper alternative relies on natural processes to do most of the work. Wetlands contain plants and bacteria that are capable of doing the same thing as the bacteria from the treatment plants. By building and restoring wetlands, it can treat waste water before it reaches other waterways.

 

Annenberg Learner.Retrieved 19 March 2012 from http://www.learner.org/interactives/garbage/sewage.html.

Wall, P. C. Earthalert. Retrieved 19 March 2012 from http://www.earthalert.org/Ocean SewageDumping Runs Afoul.html.  

NOAA Ocean Explorer (20 August 2009). Ocean Dumping. Retrieved 19 March 2012 from http://oceanexplorer.noaa.gov/explorations/deepeast01/background/dumping/dumping.html.

Planetary Notions.Effects of Dumping Sewage Water Directly Into the Sea. Retrieved 19 March 2012from http://gobiidae.com/PN/dumpingsewage.html.