Nitrogen and Phosphorus Pollution in Limnological Systems
-
Upload
stacey-findlater -
Category
Technology
-
view
2.914 -
download
3
description
Transcript of Nitrogen and Phosphorus Pollution in Limnological Systems
Nitrogen and Phosphorus Point Source Vs. Non Point Source
Pollution
Marek Koloszyc & Stacey Findlater
Point Source Pollution
• Point-source pollution occurs when pollutants enter a waterway directly.
• Can be tracked back to a specific source , location and offender.
• Easier to regulate and manage compared to Non- Point Source pollution.
Major Sources of Point Source Pollution
Sewage Treatment Plant Effluent • Excess nutrients – nitrogen and
phosphorus compounds• Detergents and personal care products• as an additive phosphorus softens
water and loosens dirt particles from fabrics
Industrial Effluent • Manufacturing and mining end of pipe
pollution
Aquaculture Fish Farms • large numbers of fish in a small area
Possible Technological Enhancements:
• Activated carbon filters-to remove phosphorus and nitrogen
• Ion exchange filters –remove charged ions
• Enhanced nutrient removal (ENR) with can reduce total nitrogen down to 3 mg/L or less and total phosphorus to 0.3 mg/L or less
• Effluent filtration in combination with chemical precipitation can be used to remove phosphorous to very low levels (< 0.1 mg/L)
Aquaculture – Fish Farms
• A Special case of agricultural pollution
• Rapidly growing industry in both fresh and marine water
• Feed wastes (up to 20%) and fish wastes - contribute to nutrient loading and eutrophication
• For every ton of fish, aquaculture operations produce up to 66 kilograms of nitrogen waste and between up to 10.5 kilograms of phosphorus waste
• Greatly impacts Benthic communities and native fish
Georgian Bay rainbow trout Farm
Issues Caused by Excess Nutrients in water Bodies
•Increase in production and biomass of algea•Massive fish kills – due to deoxygenation •Drinking water odour and taste problems during algal blooms•Piles of rotting algae along shore line•Recreation ,navigation and irrigation are affected•Harmful algal blooms – production of toxins , acutely toxic or cause skin rashes, poison shellfish •Dead zones•Loss of desirable fish ( salmon and trout) •Economic loss
Methods to Control Excess Nutrient Input
Use advanced ( tertiary) waste treatment to remove nitrates and phosphates from effluentlimits on phosphates in household detergents and other cleaning agentsSoil conservation and land-use control to reduce nutrient runoff But Can more be done?
Trophic Classification of Aquatic Ecosystems
• Oligotrophic – Low levels of organic matter – tend to be deep and clear , oxygen rich bottom supports cold water fish such as trout , Phosphorus is limiting
• Mesotrophic – more organic matter, oxygen level in lake bottom is low
• Eutrophic- High levels of organic matter – abundant plant growth , poor clarity , stratified with oxygen poor bottoms
• A dead zone is an area where oxygen levels fall below 2 ppm
The Nitrogen Cycle
• The most common forms of nitrogen in wastewater are: Ammonia (NH3) Ammonium ion (NH4+) Nitrite (NO2 )Nitrate (NO3 ) and Organic ‐ ‐nitrogen
• Microorganisms make all chemical forms of nitrogen interchangeable• Organic forms of nitrogen are broken down and converted to ammonium
in a process called ammonification• Nitrate and Ammonium are used by primary producers • Ammonia is oxidized to nitrate by nitrifying bacteria in aerobic zones
and the nitrate is converted to free nitrogen in the anoxic zone by denitrifying bacteria – removing it from the environment
The Phosphorus Cycle
• One of the Slowest nutrient cycles• Phosphorus is limiting in Marine systems
– natural phosphorus comes from the weathering of rocks
• Anthropogenic sources are rapidly taken up by primary producers – resulting in rapid overproduction
• Phosphates in marine ecosystems precipitate out as iron phosphate and form a sink in the sediment
Marek this is a good place for you to start maybe ?
Some Types of Algal Blooms
Green Algae • Cladophora sericea -
filamentous ,covers rocky areas and shorelines , can carry pathogens
Blue –Green Algae (cyanobacteria) • Microcystis aeruginosa colonial , float
on water surface – blooms is warm fresh nutrient enriched water – produces the toxin microcystin – kills dogs ,fish and shellfish, toxic or harmful to humans
• Aphanizomenon flos-aquae – can produce endotoxins that are released when the algae dies
• Ananaena sp. – filamentous , fix nitrogen , can produce neurotoxins
Lake Erie 1960 – 2011 Case study
• 1960’s – Scientists recognize that Lake Erie was suffering from eutrophication – and it was caused by human activities• Algal blooms covered large areas of the lake during summer
months , decomposing algae on bathing beaches was removed by bulldozers
• “Newspaper headlines announce Lake Erie is Dead”• 1972 The Great Lakes Water Quality Agreement led to a
coordinated effort to reduce phosphorus – a 60% reduction in loading to lake Erie • Algal blooms of Aphanisomenon reported as decreasing in intensity
and number
• 1980’s – Arrival of Zebra Muscles - several years of improved water clarity – species changes
• 1990’s – large summer blooms of Microcystis reappear• 2003-2006- Algal blooms each summer of Microcystis
The Big Question - Why is eutrophication of Lake Erie continuing to get worse since the 1972 Agreement?
Lake Erie Oct 5 2011Microcystis Areuginosa
Restoration of Eutrophic Lakes
• Chemical treatments – Copper sulfate , calcium hydroxide or calcium carbonate (lime) – reduces chlorophyll a levels in water but may be toxic to non target organisms
• Oxygenation – oxygen helps fish survive warm months and reduces algae
• Dredging – effective but expensiveRestored wetlands in watershedsRiparian Buffer Strips along
streams and estuaries
Restoration of Eutrophic Lakes - Setbacks
• Eutrophic lakes tend to be shallow and suffer from nutrient loadings from point / non point source pollution
• Lake sediments are polluted with nutrient enriched soil particles from shore erosion
• Phosphorus enriched particles sink to the bottom and form a pool of nutrients for rooted plants – internal load
Riparian Buffer Strips
• May be Natural or engineered for restoration
• Represent both wetland and forest habitats for wildlife
• Herbaceous , shrubby plants and trees with strong roots
• Prevent Nutrients and Sediment from entering watershed
• Useful in intensively used agricultural areas with
channeled water
A well defined Riparian Buffer along a lake Erie tributary
Nitrogen and Phosphorus removal in Wetlands• Wetlands act as a sponge , plants take up some nutrients• Phosphorus complexes to soil• Nitrogen is most effectively removed by denitrification• Restored wetlands provide habitat for wildlife and attract
hundreds of birds• Provide a space for naturalists and birdwatchers
St. Clair River Restoration
Mineral Fertilizers – Possible Solutions
• Fertilizer Plans for land owners – soil testing and active planning
• Increased autumn/winter green cover – to reduce leaching of nutrients from bare soil
• Subsidize smart application methods
• Develop new environmentally sound fertilizers
• Tax mineral fertilizers , and lawn fertilizers containing phosphate
• Funding for Wetland restoration and Riparian strips
Success And On To The Next!
• In the 1970’s detergents contained 40% phosphorus by weight
• The Great Lakes Water Quality Agreement in 1972 banned phosphates in laundry detergents
• July 1, 2010 New federal regulations on dishwasher detergents and household cleaners ban phosphates (0.5%) by weight
• This is expected to reduce anthropogenic phosphorus loads by 10%
• This should be considered a success as we move on to the next set of Issues
Phosphate Free Detergents Receive Bad Press
• News- National Post – “Phosphate Bans Means Streaky Dishes” – Jan 6,2011• Complaints about dishwasher
detergents on online blogs – short sighted and selfish• Public needs to be educated
to think greener!• Tip! – white vinegar or lemon
juice can be used in dishwashers as a natural rinse agent