Environmental Science and Technology Briefs for Citizens

by Terrie Boguski Landfi lls and Biochemical Oxygen Demand

When organic matter such as food waste, Water samples are often tested for BOD lawn clippings, or animal waste decom- because it is an indicator of water qual- poses, microorganisms such as bacteria ity. If BOD levels are high, dissolved and fungi feed upon it and it eventu- oxygen in the water decreases because ally becomes oxidized combined with bacteria in the water use the dissolved oxygen. Biochemical oxygen demand oxygen as they decompose organic mat- (BOD) is a measure of the amount of ter. When there is less dissolved oxygen oxygen used by these microorganisms in the water, fi sh and other aquatic spe- as they feed upon organic matter. cies may not survive.

Liquid that seeps from landfi lls is called Organisms more tolerant of lower dis- leachate. Leachate is formed when water solved oxygen levels may appear and passes through the waste in a landfi ll. The become numerous. Species tolerant of water can be from rain, melted snow, or lower dissolved oxygen levels include the waste itself. As the liquid moves carp, midge larvae, and sewage worms. through the landfi ll, many organic and Organisms intolerant of low oxygen lev- inorganic compounds may be carried in els, such as caddisfl y larvae, mayfl y, and the leachate. If the leachate contains high stonefl y nymphs, may not survive. As levels of organic matter, then it will also organic pollution increases, ecologically test high for BOD levels. stable and complex relationships present in waters containing a high diversity of Leachate may seep from a landfi ll and organisms is replaced by a low diversity fl ow into a body of water such as a lake, of pollution-tolerant organisms with in- river, or stream. It may also fl ow into creasing populations. BOD is monitored groundwater, the water fl owing beneath to help us know when action is needed the earth’s surface through soil and rock. to protect the diversity of organisms in If leachate has high BOD levels and a lake, river, or stream. contaminates a body of water, it may cause the BOD of the water to be too Modern landfi lls use liners, caps, and high, which may be harmful to fi sh and leachate collection systems to reduce aquatic species. the amount of leachate that may seep Environmental Science and Technology Briefs for Citizens Page 2 from a landfi ll. A liner keeps leachate from seeping through the bottom of the landfi ll. The cap or top cover of clay soil and vegetation is shaped to help rain This publication is published by Kansas State Univer- sity, Midwest Hazardous Substance Research Center and snowmelt to run off the surface of as part of their Technical Outreach Services for Com- the landfi ll instead of percolating down munities (TOSC) program series of Environmental Sci- ence and Technology Briefs for Citizens. If you would through the waste. Keeping water out of like more information about the TOSC program, contact the landfi ll reduces the amount of leach- your regional coordinator. ate. A leachate collection system pro- Center for Hazardous Substances in vides an easy path for leachate to follow Urban Environments and drains it into a collection system for Johns Hopkins University 3400 N. Charles St. proper handling and disposal. Remedia- Baltimore, MD 21218 tion of old landfi lls often includes adding (410) 516-8996 a clay soil cap and shallow-root vegeta- (EPA Regions 1,2, and 3) tion to reduce the amount of leachate Midwest HSRC seeping from the landfi ll. Purdue University School of Civil Engineering 550 Stadium Mall Drive West Lafayette, IN 47907 (800) 213-2812 (EPA Regions 5 and 7) AUTHOR INFORMATION Rocky Mountain HSRC Terrie K. Boguski, P.E., is a Program Department of Civil Engineering Colorado State University Manager for K-State and has been pro- A203C Engineering Building viding technical outreach services to Fort Collins, CO 80523 communities for six years. She has a B.S. (970) 491-3381 (EPA Region 8) in Chemical Engineering and an M.S. in Environmental Engineering. South and Southwest HSRC Louisiana Water Resources Research Institute 3221 CEBA Building Baton Rouge, LA70803 (225) 578-6770 (EPA Regions 4 and 6) Acknowledgement: Although this article has Western HSRC been funded in part by the U.S. Environmental Oregon State University Protection Agency under assistance agreement 204 Apperson Hall R-819653, through the Midwest Hazardous Sub- Corvallis, OR 97331 stance Research Center, it has not been subjected (541) 737-2751 to the agency’s peer and administrative reivew and, (EPA Regions 9 and 10) therefore, may not refl ect the views of the agency. for regional breakout visit: http://www.epa.gov/epa- No offi cial endorsement shoud be inferred. home/whereyoulive.htm#regiontext