COMMON MISCONCEPTIONS REGARDING THE USE OF ALUMINUM SULFATE (ALUM) IN LAKES Joe Bischoff, Wenck Associates Inc. Brian Beck, Wenck Associates Inc.

Sediment P Inactivation • P release from lake sediments

contributes to lake eutrophication • Sediment P becomes soluble under

anaerobic conditions • Mixes into the surface water for uptake by

algae • Sediment P Inactivation

• Aluminum sulfate (alum) Al2(SO4)3 ∙ nH2O

• Applied to surface water, reacts to form a white, milky floc which settles to the sediment

• Permanently binds sediment P active in internal loading

P- Watershed P - Outflow

P - Diffusion

P - Sedimentation

P - Mixing

Hypolimnion

Epilimnion

Metalimnion

Common Misconceptions About Alum • Alum treatments are overly expensive and not effective for

the long term • Alum treatments should not be considered until the

watershed load is addressed • Alum treatments are not effective in shallow lakes • Alum treatments are not safe for humans or biological

organisms

ALUM TREATMENTS DON’T LAST! Alum Treatment Misconception #1

History of Alum Use in Lakes • Alum was first used in lakes in the 1970s with no dosing considerations • Based on pH and alkalinity (Cooke et al. 1995; Kenndy and Cooke 1982)

• Does not consider sediment P concentration • Based on rate of internal P loading and an Al:P ratio assumption of 1:1

(Kennedy et al. 1987) • Al:P ratio can range between 10:1 and > 100:1

• Based on mobile sediment P and an Al:P ratio of ~12:1 • Findings from sediment cores collected many years after alum treatment

• Based on mobile sediment P and an Al:P ratio of 100:1(Rydin and Welch 1999) • Al:P ratio varies for different sediment P concentrations

• Sediment assays to predict Al:P ratio to bind 90% of redox P (James 2011)

• Very few lakes with long term data that were dosed effectively (15 years at best)

Recent Advances in Alum Dosage (W. F. James 2011)

• Based on binding and inactivating measured P fractions that are active in internal P loading • Loosely-bound P • Iron-bound P • Labile organic P

• The Al:P binding ratio is measured for accuracy • Units of Al required to bind one unit of mobile

sediment P • Thickness of the sediment layer active

in internal P loading is measured for dosage calculation

-16

-14

-12

-10

-8

-6

-4

-2

0

0 1 2 3

Sedi

men

t de

pth

(cm

)

Redox-sensitive P (mg g-1)

Potentially-mobile P layer

Alum long term effectiveness

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

Calhoun Cedar Harriet Langdon Long-Henn McCarrons Susan

33% 37% 15% 54% 55% 54% 25%

42 27 32 70 25.6 60 30

TP (m

g/L)

Pre-Alum Treatment TP

7 to 10 years Post Alum Treatment TP

>11 Year Post Alum Treatment TP

7 to 10 year Reduction (%)

Alum Dose (g Al/m2)

Welch and Cooke 1999. Four lakes with >8 year effectiveness

ALUM TREATMENTS ARE TOO EXPENSIVE! Alum Treatment Misconception #2

Costs for Alum Treatments • Cost is typically $1.75 to $2.00/gallon applied

• Buffered alum (sodium aluminate) typically costs more • 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

• Similar P removal amounts using watershed projects • Blackhawk and Thomas Lakes (Eagan)

• $1.7M for 87 pounds removal using watershed projects • $57,000 for 27 pounds removal

*Average cost of all potential watershed projects 1Cost Efficiency = cost per pound/year

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

WATERSHED LOADS MUST BE ADDRESSED FIRST! Alum Treatment Misconception #3

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 10 cm

• Bulk density assumptions ?? Others??

×

××+

=T

VWCC

PP bP

CBP

i

1

Canfield and Bachmann (1981)

VTPV

WCCPb

PCBPsed ××

××= ][

Canfield and Bachmann (1981) P Sedimentation Term

ALUM IS NOT EFFECTIVE IN SHALLOW LAKES! Alum Treatment Misconception #4

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 • Five shallow lakes (WA) treated with

alum had a minimum 7 to 10 years effectiveness with net P release reductions ranging

from 54% to 83%1

1Welch and Cooke 1995

Maximum wind event (average wind speed of 14 MPH over 14 hours estimated a wind resuspension of 2 cm sediment (90% water). USGS 1996.

Wind Resuspension - Klamath Lake, OR

-50

-40

-30

-20

-10

0

0 0.2 0.4 0.6 0.8

Redox P (mg/g)

Sed

imen

t Dep

th (c

m)

0.190 mg/g

P-Inactivation with Alum

• Alum treatments target top 5 to 10 centimeters • Diffusive interaction with

surface waters • Change P speciation from

redox sensitive to refractory (Al bound) which is unavailable to algae

• Resuspension of Al-P won’t drive algal blooms

• Sediment resuspension only impacts top few centimeters

Figure 3. Redox sensitive P and Loss on Ignition (LOI). The regression line is also shown (y = 13.239x-1.2843; r2 = 0.98).

Low Redox P with High Organic Sediment • Lakes with high organic

soils have low redox sensitive P

• Low P release • Suggests P bound in

plant material (peat accretion)

• Suggests plant dominated shallow lakes do not pump P to the surface from deeper sediments

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 10 20 30 40 50 60 70 80

LOI (%)

Red

ox P

(mg/

g)

Oneka Lake

ALUM IS NOT SAFE Alum Treatment Misconception #5

Macroinvertebrate Impacts • Lake Morey, VT (Smeltzer at al. 1999)

• The benthic macroinvertebrate community experienced a 90% decline in density year 1 then recovered with density and taxa richness exceeding pre-treatment values

• 6 Florida Lakes (Harper et al.) • In general, benthic macroinvertebrate monitoring indicated

a reduction in organism density accompanied by a dramatic shift from detritivores dominance to carnivores dominance and the reintroduction of clean water indicator species.

• Sweden Lakes Study (Huser and Kohler 2012) • Exclosure experiments determined short term impacts ,but long term

improvements due to improved water quality

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 • Achieve the benefits of alum now rather than wait 15 to 30+ years • Alum can be safely reapplied and is still cost effective

• Alum is effective in shallow lakes and can support restoration efforts • Plant establishment prevents resuspension

• Alum use is safe for both humans and lake organisms • May have some short term impacts, but long term improvements

outweigh these impacts • Needs continued research

Questions?

Minnesota’s 2012 National Lakes Assessment: National, State, and

Ecoregion-based Approach

Steven Heiskary, Environmental Analysis & Outcomes Division

Minnesota Pollution Control Agency

Minnesota Water Resources Conference 2014

2012 National Lakes Assessment (NLA) 1. Part of nation-wide random survey effort

designed to assess condition of Nation’s lakes, streams, wetland, & estuaries.

2. One resource type each year, surveys repeated every 5 years;

3. Statistically-based stratified random approach to allow inclusion of lakes across all size classes, all major ecoregions and all 48 states.

4. First NLA in 2007 included 1,028 lakes representing ~50,000 lakes in lower 48 states.

5. NLA 2012, 904 lakes including 450 lakes from 2007;

6. Minimum lake size was 1 ha and 1 m depth for inclusion in survey;

Overview 1.Describe overall NLA approach 2.Brief overview of sampling

approach 3.Example results and reporting to-

date including: water chemistry, microcystin, zooplankton, pesticides & emerging contaminants;

4.Acknowledge completed, future reporting and study collaborators.

Note pictures on side panel are examples of the range of lakes included in the study.

National & MN lake draw

1) MN received 42 lakes in national draw, 2) added 8 to allow for statistically-valid state sample 3) 100 more for 50 per aggregated ecoregion 4) represents ~15,000 lakes of 1 ha or more;

Minnesota’s 2012 NLA lakes

Example USEPA Questions 1. What is the current condition of the nation’s lakes nationally and regionally? 2. Which stressors are most associated with degraded lake condition? 3. How has the condition of lakes changed since the 2007 National Lakes Assessment?

Example Minnesota questions

1. How does MN compare to the Nation? 2. How does condition vary among regions? 3. What is the magnitude or detection frequency

of pesticides, emerging contaminants & microcystin across the state & among regions?

4. Provide un-biased state & regional descriptions of water chemistry, zooplankton, microcystin and other measures

Sample approach one-time visit included 1. pelagic: water, algae, zooplankton & sediment cores; 2. near-shore 10 random sites - observations of habitat, macrophytes,

Sampling challenges

• 150 lakes & short index period (June-Sept. 2012) • National lakes often a full-day & two crews; • Many were remote or lacked public access; • Need for multiple teams in field each week

CAWB

Summer 2012 NLA Challenges: severe storms & drought • Dropped ~ 100 lakes from 2012 survey. • Of these ~50% too shallow (<1 m), no open water, or completely dry

(mapped in red).

Map of 2012 Minnesota NLA lakes

Collaboration with partners was essential

• Several lakes on White

Earth Res., Band advised on access & landowner contacts;

• Two lakes on Red Lake Res., Band helped sample;

• Difficult access northern lakes required

MDNR & USFS & NPS

Example analysis & results: 1. Data sets allow for both statewide & regional estimates of condition & patterns. 2. Weighted estimates reflect total number or % of lakes in a class

Examples include: • Nuisance algal bloom frequency • Water chemistry: sulfate • Blue-green algal toxin - microcystin • Pesticides • Emerging contaminants • Zooplankton

Frequency of nuisance algal blooms <10 no bloom, 10-20 mild, >20 ppb nuisance

Patterns in SO4 (<10 low, 10-50 moderate & >50 mg/L high)

What is the risk of encountering measureable concentrations of the blue-green toxin microcystin?

150 lakes w/ 80 um mesh net; 51 crustacean zooplankton sp. identified including 33 cladocerans & 18 copepods; Number of sp from 1 to 15; Species richness statistically higher in NF & ETF as compared to GP ecoregion From J. Hirsch (2013)

Pesticides: Collaboration with MDA Broad suite of pesticides on 50 lakes

1. Detections low in northern MN; 2. Higher near usage of products; 3. Atrazine (67% detect in 2012) & degradate most frequently detected but lower than in 2007; 4. All found at very low levels: Atrazine max. 0.22 ug/L vs. 10 ug/L aquatic life WQS;

Emerging contaminants (EMC) 125 pharmaceuticals & endocrine active chemicals from 50 lakes (ng/L levels);

DEET at 76% most frequent Estimates of total lakes

affected (% in state & SE of estimate)

Androstenedione 27% (9) Cocaine 26% (8) Amitriptyline 24% (9) Carbadox 8% (2) Analysis of watershed land

use revealed few significant associations with EMC – suggest potential importance of atmospheric transport;

However we did find …

Note – only 1 lake received a WWTF discharge

Number of detections increases w/ increase in “disturbed” (cult+urban) land use; Sig. change-point at 42% disturbed land use (95% CI 31-72%)

MN 2012 NLA Reporting • MPCA (Ferrey) 2013 report on emerging

contaminants, journal article submitted; • MDA (Tollefson & VanRyswyk) 2014 report on

pesticide and triazine assay data; • MPCA (Heiskary, Lindon & Anderson. 2014 LRM)

article on Microcystin; comparing findings from random & targeted surveys

• MDNR (Hirsch) report on zooplankton for 150 lakes, with statewide and ecoregion-based (done)

• MDNR analysis of physical-habitat data from 2007 & 2012 NLA surveys (draft).

• MDNR - Macrophyte forms, relative abundance, and depth of colonization assessed as part of P-Hab work on 50 lakes (underway).

• MPCA statewide and ecoregion-based report on lake condition & water chemistry (underway).

http://www.pca.state.mn.us/index.php/water/water-types-and-programs/surface-water/lakes/national-lakes-assessment-project-nlap.html

MPCA 2012 Field Team Leads: Pam Anderson, Jesse Anderson, Lee Engel, Kelly O’Hara, Dereck Richter, & Steve Heiskary Assist: Amy Garcia, Courtney Ahlers-Nelson, Mike Kennedy, Andrew Swanson & Interns: Will Long & Ben Larson MPCA: Emerging contaminants – Mark Ferrey MDNR: Field & data analysis – Mike Duval, DNR lead, Jodie Hirsch - zooplankton MDH – Jeff Brenner, MC & analysis MDA – pesticides Dave Tollefson & Bill Van Ryswyk USFS & NPS: sampling assistance White Earth Band Natural Resources: Will Bement Red Lake Band Natural Resources: Shane Bowe USEPA: John Kiddon, Dave Peck, & Tony Olsen

MN 2012 NLA – Extensive Collaboration!!