The Effects of Dish Detergent on Algae

Luke J. Barrante

PJAS 2014-2015

Central Catholic High School

Eutrophication

• Enrichment of aquatic ecosystems with nutrients

• Can occur as lakes age through geological time

• First recognized as a pollution problem in the mid-20th century

Chlamydomonas reinhardtii

• Have two flagella

• Typically 10-30um wide

• Eyespot helps them gravitate toward light

• Found in calm water, damp soil, and snow

• Contains only one chloroplast

• Model species- research/bio indicators

Sodium Tripolyphosphate

• (STPP) dish/laundry detergent additive in a powdered form

• Accounts for over 50% of the dish phosphate effluent from our wastewater facilities

• Cannot be removed by secondary water treatment

• Accounts for up to 12% of manmade phosphorus in bodies of water

The EPA on STPP

• In 2008, the EPA stated that sodium tripolyphosphate causes eutrophication.

• It was suggested that phosphate be reduced in detergents.

• In 2010, Pennsylvania banned detergent formulas containing more than 0.05% phosphate.

• In hard water areas, glasses turn cloudy, grease builds up, etc.

Purpose

The purpose of this experiment is to study the effects of sodium tripolyphosphate on Chlamydomonas population growth.

Hypothesis

Experimental (single, formal hypothesis): sodium tripolyphosphate and dish detergent will individually and synergistically alter algal growth.

Null (necessary only for statistical analyses): sodium tripolyphosphate and dish detergent will not individually or synergistically alter algal growth.

Materials

1. Chlamydomonas reinhardtii

2. Soil water (Carolina)

3. Spring water (Giant Eagle brand)

4. Phosphate-free dish detergent (Reeva)

5. Sodium tripolyphosphate (SoapGoods)

6. Spectrophotometer (Carolina)

7. 5-50 μl and 100-1000 μl micropipettes

8. Test tubes and rack

9. Lamp

10. Small box

Procedure1. Four test tubes each were filled with the following concentrations.

Test Tube 1 2 3 4 5 6 7 8 9

Chlamy 2mL 2mL 2mL 2mL 2mL 2mL 2mL 2mL 2mL

Soil Water 1mL 1mL 1mL 1mL 1mL 1mL 1mL 1mL 1mL

Spring Water 2mL 1.995mL 1.95mL 1.995mL 1.99mL 1.945mL 1.95mL 1.945mL 1.9mL

Phosphate 0mL 0.005mL 0.05mL 0mL 0.005mL 0.05mL 0mL 0.005mL 0.05mL

Dish Detergent 0mL 0mL 0mL 0.005mL 0.005mL 0.005mL 0.05mL 0.05mL 0.05mL

Phosphate

Dish Detergent 0%, 0% 0.01%, 0% 0.1%, 0%

0%, 0.01% 0.01%, 0.01% 0.1%, 0.1%

0%, 0.1% .01%, 0.1% 0.1%, 0.1%

0.01%

Procedure

2. Absorbance readings of the tubes were taken at 430 nm.

3. The tube rack was placed in an open box.

4. Box was positioned directly under a lamp in a windowless room.

5. Absorbance readings were taken at 430 nm on selected days.

6. Change in absorbance from initial readings were recorded.

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3Dish Detergent and Phosphate Effects on Algae Growth

Del

ta a

bso

rban

ce a

t 4

30

nm

X4

Days after initial reading0 2 3 5 7 9 11 13

0% P, 0% D 0.01% P, 0% D 0.1% P, 0% D 0% P, 0.01% D 0.01% P, 0.01% D 0.1% P, 0.01%

0% P, 0.1% D 0.01% P, 0.1% D 0.1% P, 0.1% D

low phosphate high detergent

high phosphate

low phosphate low detergent

high phosphate low detergent

high detergent

low detergentcontrol

low phosphate

high phosphate high detergent

ANOVA Analysis

• ANalysis Of VAriance • Single factor- the comparison of means• Two factor- a comparison to test interaction (synergy) between two

independent variables• If the P-value is > 0.05, ACCEPT the null hypothesis.• If the P-value is < 0.05, REJECT the null hypothesis.

ANOVA Analysis

P-values

Day 7 Day 13

phosphate (single-factor) 0.000009 0.000021

dish detergent (single-factor) 0.000568 0.022719

interaction (two-factor) 0.023444 0.033373

Dennett's Test Analysis

Variance Day 7 Day 13

Low Phosphate insignificant insignificantHigh Phosphate significant significant

Low Detergent insignificant insignificant

High Detergent significant significant

• a multiple comparison procedure that compares each of a number of treatments with a single control.

• test gives a t-value which is compared to the ANOVA’s t-critical value; variance is significant if t-value is greater than t-crit

Conclusion

The null hypothesis is REJECTED- phosphate and detergent had significant individual and synergistic effects on algal growth.

Further data in the Dennett's test analysis suggests that in large quantities, these variables significantly harmed algal populations and in small amounts, had little to no significant effect.

These results do not support the EPA’s claim that detergent phosphate produces larger populations of algae.

Limitations Extensions

• Only one species of algae was used.

• Culture of Chlamydomonas could have been unhealthy.

• The testing period only spanned 13 days.

• Only four replicates were used.

• Only nine concentrations were tested.

• Test does not explain whether or not algae actually harms aquatic ecosystems.

• Not all ponds are the same.

• Test more than one species of algae, such as Euglena.

• Test multiple cultures of Chlamydomonas.

• Extend the testing period to longer than 13 days.

• Use more than four replicates.

• Test a wider variety of concentrations of pollutants.

• Perform a follow-up study that determines the effects of excess algae on aquatic ecosystems.

• Test with conditions of multiple ponds.

References

• http://www.epa.gov

• http://www.facultystaff.richmond.edu

• http://www.britannica.com

• http://www.environmentalleader.com

• http://www.npr.org

• http://www.colorado.edu

• http://www.ruf.rice.edu

• http://www.chlamy.org

• http://scienceinthebox.com

• http://sciencedaily.com