THE USE OF ALUMINUM SULFATE (ALUM) IN LAKES AND PONDS

Joe Bischoff and Brian Beck, Wenck Associates Inc.William F. James, University of Wisconsin-Stout

Presentation Objectives• Sediment P release in lakes (internal loading)• Background on Alum in Lakes

• How does it work?• How is it applied?

• Considerations Prior to Selecting Alum• Watershed loading and long term effectiveness• Cost• Use of alum in shallow lakes• Safety for humans and aquatic organisms

Oligotrophic Mesotrophic Eutrophic Hyper-Eutrophic

Total Phosphorus (µg/L)

Relationship between Total Phosphorusand Transparency

Lake Watershed Phosphorus Loading

Lake AnoxiaDissolved oxygen <2 mg/L

June July August September

Sediment P Release

Sondergaard et al. 2001

Sediment Core Collection

Internal Phosphorus ReductionWhy Alum?

• Sediment P Inactivation Tools• Aluminum Sulfate (Alum)• Ferric Iron• Phoslock (lanthanum clay)

• Water Column Manipulation• Hypolimnetic withdrawal and treatment• Hypolimnetic aeration

What is Alum? • Aluminum Sulfate (liquid)

• Dissolves in water to form aluminum hydroxide and sulfate

• Aluminum hydroxide is a white solid that settles out of the water column

• Permanently binds phosphorus in the sediments

• Aluminum phosphate complexation (Al(OH)3PO4)• Very stable in the environment• Not sensitive to anoxia (low oxygen)

Lake Riley Alum Application, Spring, 2016

Lake Riley Alum Application, Spring, 2016

Advanced Alum Application Technologies

• Advances in application technology have increased project effectiveness and safety

• Computerized GPS guidance and tracking systems ensure complete and accurate coverage and allows for multiple alum dose zones

Pinto Lake, CA Coverage Map

WATERSHED LOADING AND LONGEVITY

Factors Influencing Longevity

Watershed to Lake Area Ratio (32%)

Alum Dose (47%)

Osgood index (3%)(Average depth ÷ Area0.5)

Percentages refer to amount of variation explained by that variable in multiple regression (From Huser et al. 2015)

Recent Advances in Alum Dosage(Rydin and Welch 1999; W. F. James 2011; James and Bischoff 2015)

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Redox-sensitive P (mg g-1)

Potentially-mobile P layer

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Redox-sensitive P (mg g-1)

Potentially-mobile P layer

• Based on binding and inactivating measured P fractions that are active in internal P loading

• The Al:P binding ratio is measured for accuracy• Thickness of the sediment layer active in internal P loading is measured for

dosage calculation

Maximizing Alum Application Effectiveness

1• Collect Sediment Cores• Determine if alum treatment is necessary

2• Apply half alum dose (1st)• Collect sediment cores (6 months)

3• Apply half alum dose (2nd)• Collect Sediment Cores (1-3 year)

4• Monitor water quality to track effectiveness• Collect sediment cores (10 years)

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Redox-sensitive P (mg g-1)

Potentially-mobile P layer

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R d iti P ( 1)

Potentially-mobile P layer

Adapting to Sediment Results

Factors Influencing Longevity

Watershed to Lake Area Ratio (32%)

Alum Dose (47%)

Osgood index (3%)(Average depth ÷ Area0.5)

Percentages refer to amount of variation explained by that variable in multiple regression (From Huser et al. 2015)

Lake P Sedimentation• How long does it take to

replace inactivated sediment TP?• Used Canfield Bachmann P

sedimentation term to estimate P loading to sediment

• Assumes 90% inactivation in top 5 cm

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××+

=T

VWCC

PP bP

CBP

i

1

Canfield and Bachmann (1981)

VTPV

WCCPb

PCBPsed ××

××= ][

Canfield and Bachmann (1981) P Sedimentation Term

Internal or Watershed First?

Watershed Projects Internal load Lake Clarity

improvement

Traditional Thought Model

Watershed Projects

Internal loadLake Clarity improvement

Internal load Internal load

Proposed Thought Model

ALUM USE IN SHALLOW LAKES

Factors Influencing Longevity

Watershed to Lake Area Ratio (32%)

Alum Dose (47%)

Osgood index (3%)(Average depth ÷ Area0.5)

Percentages refer to amount of variation explained by that variable in multiple regression (From Huser et al. 2015)

Alum Use in Shallow Lakes• Physical and biological factors

increase internal load potential and may limit the effectiveness of alum• Wind re-suspension of sediments• Bioturbation from rough fish,

especially carp• Sediment P pumping from deep

sediments by submerged vegetation

Strategy for Restoring Shallow Eutrophic Lakes

• Forward switch detection and removal

• External and internal nutrient control (TMDL)

• Biomanipulation (reverse switch)

• Plant establishment• Stabilizing and managing restored system

From Huser et al. 2015

Shallow Lake Alum Treatments

ALUM COSTS

Costs for Alum Treatments• Cost is typically $1.75 to

$2.00/gallon applied• Alum prices vary significantly year

to year

• Sticker shock for upfront costs• Bald Eagle Lake $860,000• Halsted Bay $1.1M• Spring Lake $986,000• Lake Riley $480,000

Costs for Alum Treatments

Blackhawk and Thomas Lake Management Plan Wenck 2013Neighborhood Lakes Management Plan Wenck 2014 Bald Eagle Lake TMDL Implementation Plan, Wenck 2010

ALUM SAFETY

Aluminum and Human Health• Al is the third most abundant element in

the earths crust• food, water, air, and soil contain aluminum• Occurs naturally in lake sediments

• The average adult eats 7–9 milligrams (mg) aluminum per day in their food

• Only very small amounts of aluminum will enter the bloodstream

• The FDA concluded that aluminum as a food additive is generally safe

One dose of Maalox includes 400 mg Aluminum Hydroxide

Aluminum ToxicityFish and Macroinvertebrate Impacts

• Toxic dissolved aluminum (Al3+) forms if pH drops below 6• pH can be controlled with proper dosing or

buffering

• Aluminum does not bioaccumulate in algae or fish tissue • Huser and Kohler, 2012

• Macroinvertebrates show short term impacts followed by community recovery and improvement• Smeltzer at al. 1999; Harper et al.; Huser

and Kohler 2012

Conclusions

• Sediment P inactivation is more cost effective that watershed BMPs on a cost per pound removal

• Alum can be effective for 15 to 30+ years if dosed correctly• Controlling external P loads is important, but alum

treatments can be effective even when watershed loads are moderately high

• Alum is effective in shallow lakes and can support restoration efforts

• Alum use is safe for both humans and lake organisms

Questions?