Eutrophication Management Strategies: Control of Major Eutrophication Sources |
Research: Impacts of Cultural Eutrophication on Lakes
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In order to control eutrophication and restore water quality, it is necessary to check and restrict phosphorus inputs, reduce soil erosion, and develop new technologies to limit phosphorus content of over-enriched soils (Carpenter and Lathrop 2008).
Under natural conditions, total phosphorus concentrations in lakes range from 14-17 parts per billion (ppb). In 1976, the Environmental Protection Agency recommended phosphorus limits of 25 ppb within lakes to prevent and control eutrophication (Addy and Green 1996). However, many lakes still have nutrient levels above this limit. Lake Washington is a case in point: in the 1960s, phosphorus was found in concentrations of 70 ppb (Edmondson 1991). Although phosphorus levels have declined since the EPA set limits on nutrient loading in 1976, current levels are still too high for healthy lakes. Steps that can be taken immediately include enforcing wastewater treatment and eliminating the importation of chemical phosphorus to watersheds via fertilizers (Schindler 2006).
Restoration strategies include hypo-limnetic aeration (where water from the bottom of a lake is brought to the surface to be oxygenated then returned to the bottom), bio manipulation (the manipulation of food webs to lower levels of algae), and nutrient loading restrictions (restricting phosphorus levels). Of these strategies, I propose that an integrated strategy focusing on nutrient input restrictions and incorporating bio manipulation is essential to future eutrophication management. While hypo-limnetic aeration is the most common approach to improve oxygen conditions of water, the effectiveness of this process is dubious and variable.
For example, studies have shown that this alternative is less effective in shallow lakes. And there is little evidence that hypo-limnetic aeration reduces algal biomass (Cooke and Carlson 1989). Conversely, phosphorus loading restrictions have led to rapid recovery from eutrophication in many lakes (Smith 2009). Lake Washington is perhaps the most widely recognized success story of recovery from eutrophication through nutrient input control (Fig 3). After the city began diverting phosphorus-containing wastewater effluent from the lake, there was a profound improvement of water quality and decrease of phytoplankton growth (Schindler 2006). Thus, to mitigate eutrophication and algal biomass, nutrient control focusing on reducing phosphorus input is vital (Anderson et al. 2002). Nevertheless, while most scientists agree that hypo-limnetic aeration is ineffective, there is still much debate over the use of bio manipulation and nutrient loading restrictions to curtail eutrophication (Cooke 2005).
Measures to curb phosphorus inputs to remedy eutrophic ecosystems have focused on detergent bans, effluent limits, and soil erosion controls (Carpenter 2008). The reduction and eventual elimination of phosphates in detergents is necessary to manage eutrophication. As synthetic detergents became prevalent, phosphate consumption grew to a peak of 240,000 tons in the US. Since 1970, the detergent industry has limited the amount of phosphate in detergents, but a complete ban would remove up to 30% more of the phosphates in sewage, thus reducing future loading to lakes (Litke 1999).
Additionally, the concentrations and loads of phosphorus in wastewater-treatment plant effluents fluctuate together with the consumption of phosphate in detergents. Amendments to the Federal Water Pollution Control Act in 1961 also enforced environmental technology techniques to control discharge from wastewater treatment plants and improve water quality. More plants now treat their wastewater to remove up to 99% of phosphorus, significantly decreasing the amount of the nutrient released into lakes (Litke 1999). At present, there is still a need to find a phosphate substitute in detergents and implement tertiary treatment of wastewater for more complete phosphorus removal. Continuing to educate consumers so that they choose washing products with the least amount of polluting ingredients is also vital (Knud-Hansen 1994).
Under natural conditions, total phosphorus concentrations in lakes range from 14-17 parts per billion (ppb). In 1976, the Environmental Protection Agency recommended phosphorus limits of 25 ppb within lakes to prevent and control eutrophication (Addy and Green 1996). However, many lakes still have nutrient levels above this limit. Lake Washington is a case in point: in the 1960s, phosphorus was found in concentrations of 70 ppb (Edmondson 1991). Although phosphorus levels have declined since the EPA set limits on nutrient loading in 1976, current levels are still too high for healthy lakes. Steps that can be taken immediately include enforcing wastewater treatment and eliminating the importation of chemical phosphorus to watersheds via fertilizers (Schindler 2006).
Restoration strategies include hypo-limnetic aeration (where water from the bottom of a lake is brought to the surface to be oxygenated then returned to the bottom), bio manipulation (the manipulation of food webs to lower levels of algae), and nutrient loading restrictions (restricting phosphorus levels). Of these strategies, I propose that an integrated strategy focusing on nutrient input restrictions and incorporating bio manipulation is essential to future eutrophication management. While hypo-limnetic aeration is the most common approach to improve oxygen conditions of water, the effectiveness of this process is dubious and variable.
For example, studies have shown that this alternative is less effective in shallow lakes. And there is little evidence that hypo-limnetic aeration reduces algal biomass (Cooke and Carlson 1989). Conversely, phosphorus loading restrictions have led to rapid recovery from eutrophication in many lakes (Smith 2009). Lake Washington is perhaps the most widely recognized success story of recovery from eutrophication through nutrient input control (Fig 3). After the city began diverting phosphorus-containing wastewater effluent from the lake, there was a profound improvement of water quality and decrease of phytoplankton growth (Schindler 2006). Thus, to mitigate eutrophication and algal biomass, nutrient control focusing on reducing phosphorus input is vital (Anderson et al. 2002). Nevertheless, while most scientists agree that hypo-limnetic aeration is ineffective, there is still much debate over the use of bio manipulation and nutrient loading restrictions to curtail eutrophication (Cooke 2005).
Measures to curb phosphorus inputs to remedy eutrophic ecosystems have focused on detergent bans, effluent limits, and soil erosion controls (Carpenter 2008). The reduction and eventual elimination of phosphates in detergents is necessary to manage eutrophication. As synthetic detergents became prevalent, phosphate consumption grew to a peak of 240,000 tons in the US. Since 1970, the detergent industry has limited the amount of phosphate in detergents, but a complete ban would remove up to 30% more of the phosphates in sewage, thus reducing future loading to lakes (Litke 1999).
Additionally, the concentrations and loads of phosphorus in wastewater-treatment plant effluents fluctuate together with the consumption of phosphate in detergents. Amendments to the Federal Water Pollution Control Act in 1961 also enforced environmental technology techniques to control discharge from wastewater treatment plants and improve water quality. More plants now treat their wastewater to remove up to 99% of phosphorus, significantly decreasing the amount of the nutrient released into lakes (Litke 1999). At present, there is still a need to find a phosphate substitute in detergents and implement tertiary treatment of wastewater for more complete phosphorus removal. Continuing to educate consumers so that they choose washing products with the least amount of polluting ingredients is also vital (Knud-Hansen 1994).