Sewer Treatment Plants (Erica Brauer)

Author(s)

Erica Brauer, Granada Hills Charter HS, CSUN

NGSS Engineering Standards

HS-ETS1-3. Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts.

NGSS Engineering Standards

PROBLEM - Sewage treatment plants are expensive to build, but need to be efficient at cleaning sewer water. Students will try to build a functioning, cost effective sewage treatment model.

DESIGN - Students are going to design model sewage treatment plants, and will actually attempt to use the treatment plants to treat "sewer water". Describe what students are to design. There are two constraints on the engineering design: cost and time the "sewer water" takes to drain. Students will choose what material they want to use, based on the cost of the different supplies. They will then attempt to treat sewer water with their design. The goal is to build a cost effective treatment plant that cleans the water in a reasonable amount of time.

OPTIMIZATION - After students see what does and does not work, and what is more cost effective, students will redesign their models. The goal is that the new model is better at cleaning, is more affordable and works in a more timely manner after optimization.

Background

Each year billions of dollars are spent worldwide to purify water. In this lab you are going to build a water filtering system to see how effectively you can purify a simulated sample of polluted water.

Working with two to four team members, you will construct a water purification system capable of taking 300 ml of simulated polluted wastewater and producing 200 ml of purified, clean water. You will be held accountable for the cost of your wastewater treatment system, the speed at which you are able to produce clean water, and, of course, the quality of the water that you produce.

Important Safety Notice: At no point during this lab are students to taste or drink any water samples including the “purified” water after it is processed through the water filters. Hands should be washed throughout the lab and gloves worn when working with questionable pond water.

The simulated wastewater that you will be asked to purify will contain the following pollutants:

Living Microorganisms - these may include microscopic worms, tiny insects and invertebrates, protists such as paramecium and euglenas, microscopic algae, and bacteria. (the source of these living organisms will be pond water)

Organic and Inorganic Debris – these may include leaves, tiny twigs, sawdust, fine gravel, pieces of toilet paper (unused), and pieces of plastic (a real wastewater treatment plant would use screens to remove large debris from the water)

Oil – the oil in your “polluted” water will be vegetable oil used in cooking and it will represent oil contamination from industrial sources and leakage from the transportation industry and from pipelines.

Soil – soil is a widespread contaminate of water; the soil in your sample will contain sand, silt, and clay. Soil is one cause of turbidity.

Dissolved Solids – your wastewater sample will contain some baking soda (sodium bicarbonate) that represents dissolved solids such as calcium carbonates and magnesium carbonates.

Urine Waste – your wastewater sample will contain a small amount of ammonia which is what urine breaks down into over time. (one way to tell if the ammonia has been removed is by smelling the water (not tasting it) to see if any ammonia odor remains. Use can also test for the ammonia concentration using a test kit or probeware.

Organic Waste – organic waste is often dumped into waterways. Cornstarch has been mixed into your wastewater sample to represent organic waste.

Industrial Detergents – industrial detergents are sometimes dumped into waterways or wastewater treatment systems and must be removed. We will be using dishwashing detergent in our wastewater sample

Materials needed

Materials Available for Building Your Water Purification Filter:

Clear, plastic water bottle with the bottom cut off ($10) – this will be inverted and become the main structure of your water purification system

Small, irregular-shaped rock ($2) – this will be dropped into the inverted plastic water bottle to prevent fine gravel or other materials from falling out through the neck of the bottle and at the same time allow effluent to flow out (instead of a small rock, students may want to wrap a piece of mosquito netting around the end of the bottle and rubber band it into place to prevent materials from falling out)

A 16cm high section of another water bottle with the top cut off ($5) – the bottom section of an additional water bottle will be used to collect the 200ml of effluent (hopefully clean water) from the filtering process

15cm x 15cm section of mosquito netting ($2) – used for screening out large pieces of debris (your teacher may provide a 4oz. plastic soufflé cup with the bottom cut out that can be used at the top of your filter to hold the mosquito netting in place and create a debris screen)

Fine Gravel (2cm @ $2 or 1cm @ $1) – allows water to flow when necessary, helps to block large pieces of materials, and allows for aeration

Coarse Sand (2cm @ $2 or 1cm @ $1) – filters polluted water while allowing good water flow, and allows for aeration

Fine Sand (2cm @ $2 or 1cm @ $1) – filters polluted water and removes small particles

Vermiculite (2cm @ $4 or 1cm @ $2 – has cation exchange capacity which allows it to remove chemical pollutants from the water; also serves as an absorbent

Activated Charcoal (2cm @ $4 or 1cm @ $2) – absorbs organic pollutants and chemicals, removes odors, and reduces unwanted coloration of the water

20cm x 20cm square of cotton fabric ($1 each) – filters out small particles and absorbs organic pollutants

Paper towels (Large piece $2 each or Small piece $1 each) – filters out very small particles and absorbs organic pollutants

Coffee filters of Paper Lab filters ($2 each) – filters out extremely small particles such as fine sand and silt

Vinegar (Ascetic acid) ($1 per milliter) – neutralizes basic water and helps restore the pH to 7.0

Alum or Aluminum Sulfate solution ($1 per 10ml) – removes dissolved solids such as calcium carbonate, magnesium carbonate, and sodium bicarbonate from the water through the process of flocculation

Q-tips ($1 for 5) – used for skimming off floating scum

Chlorine Bleach or Sodium Hypochlorite solution ($1 per 5ml) – kills microscopic animals, protists, bacteria, and viruses; reduces discoloration of the water. Will be administer to the treated water after filtration and flocculation are finished

Rubber Bands – free

pH Paper – used for testing pH after filtration, flocculation, and chlorination have been completed. Use a few drop of vinegar to move the water from basic (pH 8,9, or 10) towards a neutral 7. (free) (You can also use universal indicator)

Remember to add up the cost of all the materials that you used in the construction of your water purification filter. Your team will receive construction cost points based on the following scale:

Low Cost – $20 to $29: Point Value 30 points

Medium Cost - $30 to $49: Point Value 20 points

High Cost - $45 to $60: Point Value 10 points

Procedure

1. Draw out a design of your sewage treatment plant.

2. Cut two 1 liter bottles so that you have a relatively long base, and a long top (see pictures below).

3. Choose supplies that you would like to use, recording how much it will cost as you "buy" things.

4. Build your sewage treatment plant.

5. Run distill water through it to test its drainage and clean the rocks used.

6. When you are ready, dump the sewage into your treatment plant until you reach 200 mls of water into the bottom container.

7. Treat your water with flocculant and bleach (if you choose to do this stage) after you separate the top container from the bottom.

8. Use pH strips to test the water.

9. In addition to the cost of the material you counted above, the following will also be used to grade your design:

Time to produce 200 ml of processed effluent:

Fast Processing: 1 minute to 5 minutes = 30 points

Normal Processing: 5 minutes to 20 minutes = 20 points

Slow Processing: 21 minutes or more = 10 points

Assuring that the purified water meets high quality standards.

Living Microorganisms - No detectable microorganisms (15 points); a few detectable microorganisms (5 points); large numbers of detectable microorganisms (0 points)

Organic and Inorganic Debris – No detectable large debris (15 points); a small amount of detectable debris (5 points); a large amount of detectable debris (0 points)

Oil – No detectable oil residue (15 points); a tiny amount of oil residue (5 points); a large amount of oil residue (0 points)

Soil – No detectable sand or silt in the water or at the bottom of the purified water container (15 points); a tiny amount of sand or silt is visible (5 points); a large amount of sand or silt is visible (0 points)

Acid Waste – A pH level between 6 and 8 (15 points); a pH level between 4 and 6 or a pH level between 8 and 10 (5 points); a pH level less than 4 or greater than 10 (0 points)

Ammonia – No ammonia smell or 0 ppm of ammonia (15 points); slight ammonia smell or 1 ppm to 5 ppm of ammonia detected (5 points); strong smell of ammonia or greater than 5 ppm of ammonia detected (0 points)

Turbidity – Crystal clear water, no or very low turbidity, Nephelometric Turbidity Unit reading of 0 to 20 (20 points); slightly turbid water, transparent, NTU reading of 20 to 80 (15 points); moderately turbid water, translucent, NTU reading of 80 to 140 (5 points), very turbid water, dark, opaque, NTU reading above 140 (0 points)

Industrial Detergents – No bubbles or foaming when effluent sample is shaken (15 points); a few bubbles, slight foaming when effluent sample is shaken (5 points); large number of bubbles and significant foaming when effluent sample is shaken (0 points)

TDS (total dissolved solids such as calcium carbonate and magnesium carbonate) – TDS level of 0 to 5 (15 points); TDS level of 5 to 30 (5 points); and a TDS rating higher than 30 (0 points).

Overall Odor – No odor (15 points); slight odor (5 points); and strong odor (0 points)

Color – Crystal clear, no tint or color (15 points); slight color of green, brown, yellow, or grey (5 points); strong color present (0 points)

Questions

  • Did your design clean sewage water well? Why or why not?

  • Was your design the most cost effective way to clean the water? Why or why not?

  • How long did your water take to clean? What impact could this have on treating real sewer water?

Photos

  • Real-life applications-real water treatment centers!!!

Movies

Include movies that you have taken. Your movies should be placed in your youtube account.

References

Provide links to relevant websites.