Dr. Erin Argyilan- Lincoln Park rower
Contamination by bacteria and other micro-organisms significantly limits a variety of waterway uses, including recreational activities in which humans contact the water directly. The MWRD operates three water reclamation plants on the Chicago River system: the Northside, Stickney, and Calumet, which process the combined sewer flow and release the treated effluent into the river. The treatment process reduces the volume of solids and other compounds that degrade water quality. But the treated effluent, which makes up approximately 70% of the river’s annual flow, also contains elevated levels of bacteria and pathogens at levels higher than the U.S. Environmental Protection Agency recommends for human contact.
Biological wastewater treatment processes work by promoting the rapid growth of microbial species that consume and digest waste products found in the water. The final process at most large sewer treatment plants involves killing off as many undesirable bacteria and other pathogens as possible. The elevated levels of bacteria and pathogens in the Chicago Waterways can be attributed to an absence of any state regulatory requirement for the disinfection of effluent, and they are one of the few major wastewater facilities in the country that is not required to disinfect.
This relatively unique situation was highlighted in a 2000 study by the Openlands Project, the Civic Federation, and the Friends of the Chicago River. It found that of 23 sewage treatment agencies classified by the USEPA as “major dischargers,” the MWRD was the only one that does not disinfect its effluent or otherwise meet bacterial contamination standards of limits. However, the MWRD complies almost 100% with existing permits. Permit limits, however, are weak—or in the case of bacteria, nonexistent—for much of the river.
There are a number of technologies that are used to disinfect wastewater effluent and protect public health. Chlorination is the most widely used disinfectant at both water and wastewater treatment plants in the Untied States. Chlorine reacts rapidly with water and can inactivate a wide range of pathogens. However the use of chlorine disinfection of wastewater can result in adverse environmental impacts due to the residual chlorine in the water after treatment and the formation of toxic compounds that negatively affect aquatic life and human health. In the mid 1980’s when the MWRD stopped using chlorine to disinfect wastewater, biodiversity of fish in the Chicago area waterways dramatically increased.
Ultraviolet (UV) irradiation has become the second most common method after chlorination. It is a process that changes the biochemical properties of pathogens when they are exposed to UV light. This process is also energy intensive, but maintenance is simple and does not require skills beyond changing lightbulbs, and cleaning the arrays.
Ozone is a very strong oxidizing agent and can be used in disinfection because it reacts to both organic and inorganic compounds in wastewater. An ozone disinfection system first transfers ozone into the wastewater where the ozone can make contact with the pathogens. Contact time is usually 10 to 15 minutes. Ozone disinfection is relatively expensive because the equipment used is complex and difficult to maintain and operate. The process to generate ozone is also an electricity intensive one.
In recognition of the growing recreational use of the Chicago Area Waterways, the Illinois Environmental Protection Agency (IEPA) is completing a Use Attainability Analysis (UAA) of the Chicago Area Waterways to evaluate upgrading the use designations. As the Chart shows: in 2004 sampling data of bacteria counts at all three water treatment facilities are significantly higher downstream from the water reclamation facilities.
IEPA has recommended that the Chicago River’s designated use be upgraded to an E. Coli bacteria standard of 1030 cfu/100 ml during the primary recreational period of March 1 through November 30. This would require disinfection at Northside and Calumet plants. The third plant Stickney was not included in the IEPA recommendations because of the lower levels of recreation in that reach of the river.
Friends of the Chicago River, supports the IEPA’s proposed upgrades of water quality standards to protect public health and we recommend the use of ultraviolet irradiation (UV) as the preferred disinfection technology.
•Disinfecting the effluent on the Chicago waterways is the correct policy because recreational use of the river is growing and this is the solution most protective public health.
•Independent polling confirms that the public supports clean water. In a 2005 national opinion survey, Luntz Research found that an overwhelming majority of the public, 91 percent, agree that ‘‘if, as a country, we are willing to invest over $30 billion dollars a year on highways and more than $8 billion a year on our airways, we certainly should be willing to make the necessary investments in our nation’s rivers, lakes and oceans.’
•The cost is manageable. It has been estimated that the cost of disinfection for two of the three water reclamation facilities using ultraviolet (UV) technology is $84 million annually. (Capital cost + O&M + Debt service) The per person cost $.042 per day
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