Vernier Software and Technology
Vernier Software & Technology

Biochemical Oxygen Demand

Figure from experiment 16 from Investigating Environmental Science through Inquiry

Introduction

Oxygen available to aquatic organisms is found in the form of dissolved oxygen. Oxygen gas is dissolved in a stream through aeration, diffusion from the atmosphere, and photosynthesis of aquatic plants and algae. Plants and animals in the stream consume oxygen in order to produce energy through respiration. In a healthy stream, oxygen is replenished faster than it is used by aquatic organisms. In some streams, aerobic bacteria decompose such a large volume of organic material that oxygen is depleted from the stream faster than it can be replaced. The resulting decrease in dissolved oxygen is known as the Biochemical Oxygen Demand (BOD).

When it rains, organic material found in the soil is transported in the rainwater to streams and rivers. Additional organic material accumulates in the stream when aquatic organisms die. Bacteria and other microorganisms decompose this organic material. In a healthy body of water, this process has only a slight impact on dissolved oxygen levels. It serves to release vital nutrients, such as nitrates and phosphates, which stimulate algae and aquatic plant growth. If the amount of decomposing organic material is too high, dissolved oxygen levels can be severely reduced. In a body of water with large amounts of decaying organic material the dissolved oxygen levels may drop by 90%—this would represent a high BOD. In a mountain stream with low levels of decaying organic material, the dissolved oxygen levels may drop by only 10% or 20%—a low BOD.

Objectives

In the Preliminary Activity, you will gain experience using a Dissolved Oxygen Probe as you determine the DO level of a water sample provided by your teacher.

After completing the Preliminary Activity, you will first use reference sources to find out more about BOD before you choose and investigate a researchable question dealing with BOD.

Sensors and Equipment

This investigation features the following Vernier sensors and equipment.

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Standards Correlations

See all standards correlations for Investigating Environmental Science through Inquiry »

Investigating Environmental Science through Inquiry

See other experiments from the lab book.

1Seasons and Angle of Insolation
2A Local Weather Study
3Investigating Dissolved Oxygen
4Water Quality
5Long Term Water Monitoring
6Water Treatment
7Investigating Salinity
8Soil Temperature
9Soil Salinity
10Soil pH
11Soil Moisture
12Soil and Acid Rain
13Managing Garden Soil Moisture
14Cell Respiration (CO2)
15Biodiversity in Ecosystems
16Biochemical Oxygen Demand
17Water Cycle Column Investigations
18Decomposition Column Investigations
19Ecocolumn Investigations
20Global Warming
21UV Investigations
22Comparing Sunscreens
23Primary Productivity
24Modeling Population Growth
25Insulation Study
26Fossil Fuels
27Energy Conversion
28Wind Power
29Photovoltaic Cells
30Investigation of Passive Solar Heating
31The Effect of Acid Deposition on Aquatic Ecosystems
32Measuring Particulates
33Investigating Indoor Carbon Dioxide Concentrations
34A Pollution Study

Investigation 16 from Investigating Environmental Science through Inquiry Lab Book

<em>Investigating Environmental Science through Inquiry</em> book cover

Included in the Lab Book

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