Using Algae for Phytoremediation (Part 1/3)

Students will design experiment to test a mixture of plant-like protists (commonly known as algae) to clean up wastewater.  This is the first day of a three day lab. (Find day two at this link and day three at this link.) Here is an overview of what students will learn today.  

Begin by showing students the above image and asking them to describe what they see. Then ask students to respond to the following questions:

• Explain the importance of having clean water.  
• List the types of things that might cause water to be polluted. 
• Explain how wastewater is remediated so that it can be used again as drinking water.  

Using the Frayer method, define phytoremediation.  

Students will add 5 grams of a locally collected algal mat that has been grown in Bold's Basal Medium for one week to a 100 mL sample of simulated wastewater. Initial concentrations of the pollutant in the wastewater will be determined using a Spectrovis spectrophotometer 

Students will be provided with five copper (II) sulfate solutions of known concentration (standard solutions) in cuvettes. From these samples, they will develop a graph that shows the relationship between absorbance and concentrations. Concentrations of unknown samples can then be determined using the graph.  

After the graph has been made, 5 mL samples will be removed from the algal/wastewater culture every 10 minutes and concentrations of the pollutant will be determined using the spectrophotometer. Samples will also be taken at every hour after the period is complete until school is dismissed (see student handout and data sheet).  

(Note: This lab is based on the application of Beer's Law. The amount of light that penetrates the solution and strikes the photocell in the spectrophotometer is used to compute the absorbance of each solution. On day 2, students will graph absorbance vs. concentration for the standard solutions; a direct relationship should result. Students will use the collected data from the simulated wastewater to determine the maximum removal rate of the pollutant by the algal mat.)

In their lab notebooks, ask students to list reasons why they think using an algal mat might be better than using a pure culture of algae.  Ask them to list potential problems for not using a pure culture.  

Homework:  Students should view the tour of a wastewater treatment plant and complete a current events summary sheet.  

(Note: Students will continue this lab in the next lesson.)