1 / 22

Retention Basins and Rain Gardens

Retention Basins and Rain Gardens. A Possible Solution to Nutrient Pollution in Natural Waters?. Population Growth & Urbanization. Impervious surfaces lead to excessive storm water Because of urbanization hydrology is changed. Water Quality Decline. Influx of pollutants

Download Presentation

Retention Basins and Rain Gardens

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Retention Basins and Rain Gardens A Possible Solution to Nutrient Pollution in Natural Waters?

  2. Population Growth & Urbanization • Impervious surfaces lead to excessive storm water • Because of urbanization hydrology is changed

  3. Water Quality Decline • Influx of pollutants • Nitrogen (N2) and phosphorous (P) • Excessive quantities can cause eutrophication • ↑ in algae • ↓ dissolved O2 levels • Leads to widespread fish kills

  4. Water Quality Decline N Concentrations in Bay Streams, 1987-1997 • Key problem is nutrient pollution, particularly nitrogen (N) pollution • About ½ half of N load to Barnegat Bay comes from surface runoff (Kennish et al. 2007) • Removing nutrients from surface water before it enters the Bay is cost effective way to improve Bay health Source: Hunchak-Kariouk and Nicholson, 2001

  5. Nitrogen Cycle – a Key Player • N2 makes up over 75% of air • Contained in Amino Acids, proteins & nucleic acids of living things • Comes in various forms • Only ammonium (NH4+) & nitrate(NO3-) are useable by plants & algae

  6. Nitrogen Cycle – a Key Player • Nitrogen-fixation • anaerobic bacteria convert atmospheric into NH4+ & NO3- • Vital part of Nitrogen Cycle • Made of several parts • Nitrification • Denitrification • Ammonification http://www.google.com/imgres?q=nitrogen+cycle&hl=en&gbv=2&biw=1024&bih=566&tbm=isch&tbnid=Oer5J0d51BtSrM:&imgrefurl=http://www.h2ou.com/h2nitrogencycle.htm&docid=cnNVBqgcmbsX0M&imgurl=http://www.h2ou.com/h2images/NitrogenCycle-lgr-F.jpg&w=697&h=605&ei=qZKzT9DaBNCN6QHmobiQCQ&zoom=1

  7. http://www.google.com/imgres?q=nitrogen+fixation&hl=en&biw=1024&bih=566&gbv=2&tbm=isch&tbnid=cl6dCdYpP-4HkM:&imgrefurl=http://landscapeforlife.org/give_back/3c.php&docid=KXqSzFlwUhex0M&imgurl=http://landscapeforlife.org/images/nitrogencycle.jpg&w=880&h=687&ei=qpGzT8b4C8Gbgwfk89T_Bg&zoom=1http://www.google.com/imgres?q=nitrogen+fixation&hl=en&biw=1024&bih=566&gbv=2&tbm=isch&tbnid=cl6dCdYpP-4HkM:&imgrefurl=http://landscapeforlife.org/give_back/3c.php&docid=KXqSzFlwUhex0M&imgurl=http://landscapeforlife.org/images/nitrogencycle.jpg&w=880&h=687&ei=qpGzT8b4C8Gbgwfk89T_Bg&zoom=1

  8. You tube Video on Nitrogen Cycle • Nitrogen Cycle Description

  9. NO3 CONCENTRATION (AS N), MG/L 1994/95 LAND USE/ LAND COVER, % INCREASING URBAN LAND Rationale • Human development increases impervious cover in watersheds • Traditional rain gardens collect storm water from impervious areas and infiltrate it through soil, slowing delivery to rivers and bays, but don’t reliably remove nutrients, esp. Nitrogen Source: Hunchak-Kariouk and Nicholson, 2001

  10. Nutrient Pollution Standards • US Federal Government changed standards in 2007 • Resulted in a call to lower nutrient pollution from industry, commercial, and residential areas • ↓ non-point pollutants • ↓ N2 and P

  11. Rationale • 2008 National Estuarine Eutrophication Assessment suggests Barnegat Bay is in pretty bad shape • Problems are expected to worsen over time

  12. Solution: Keep nutrients out of waterways • Limit amounts of N-& P- containing nutrients making their way into aquatic ecosystems • In turn, algal blooms would decrease • Also slow flow and possibly divert storm water away from rivers and streams • Reduce downstream flooding

  13. Prior Studies • Many studies have investigated ways to reduce nutrient pollution in waters of East Coast of United States e.g. • Charles River in Boston • North Carolina • Aimed at decreasing excessive nitrogen and phosphorous in bodies of water

  14. Bioretention hydrology & nutrient Removal in North Carolina • Bioretentions built in proximity to Shopping Center with proper filtration can allow in upwards of 40% of nitrogen & phosphorous removal • Water outflow also reduced, especially in warmer seasons

  15. Stormwater ponds & biofilters in Charles River, Boston MA • Reduction of phosphorous from nearby industries into bodies of water can be achieved • Up to 65% removal with the use of detention pond and filter system

  16. Traditional “Infiltration Style” Rain Garden • Designed to slow water flow • Absorbs excess water flow from nearby impervious surfaces • Flood reduction by in increased absorbency • Decreases soil erosion

  17. Traditional “Infiltration Style” Rain Garden • Unreliable at nutrient removal • Maximum phosphorus and nitrogen removal is between 30 – 40% • Inadequate at reducing the amount of nutrients making its way into bodies of water • Water generally flows vertically through traditional style rain garden

  18. Current Studies • Univ. of New Hampshire Stormwater Center is a leader in study of methods for nutrient removal • Their proposed solution uses horizontal filtration of water through a “Gravel Rain Garden” • Dense plantings at surface means lots of plants to take up nutrients through their root system • More important, though, is the anaerobic environment created in crushed stone that lies beneath. • Allows for denitrification

  19. Nitrogen-Removing Rain Gardens • Create extensive saturated zone designed to maintain anoxic conditions to promote denitrification through use of impervious liner • Longer retention of water, increases nitrogen removal efficiency • Base of gravel to provide high surface area for microbial activity • Top with soil and plant with typical rain garden plants

  20. Disadvantages • More expensive • New technology so not yet commonly constructed • Replacement of vegetation every three years to ensure nitrogen removal capabilities are optimized

  21. Advantages • Existing ponds and detention basins can be turned into subsurface gravel rain gardens • Works well in cold climates • Much superior and more reliable nutrient removal than obtained with traditional “infiltration style” rain gardens

  22. Questions?

More Related