Kyle Smith

1B

Sewer Science Lab

Question:

Does waste water treatment bring turbidity to levels acceptable for drinking water standards?

Hypothesis:

If we treat waste water then the turbidity levels will be acceptable for drinking water standards because it has been sufficiently cleaned by the multiple steps in the treatment process.

Variables:

Background:

        Through this process of wastewater treatment, wastewater should theoretically become pretty close to chemically perfect water. So perfect in fact, some communities are using treated wastewater to drink directly. Is this safe? Safe drinking water turbidity levels are under 5 NTU, ideally under 1 NTU. This is a fairly broad range, but does wastewater treatment cut it? This is what will be gathered from this lab.

Wastewater treatment is an essential process that local communities, as well as global communities, need to perform on wastewater in order to return the water back to rivers and lakes. It is so important because it affects the health of all life: from the wildlife habitats within the water, all the way to humans. If untreated wastewater were to be dumped directly into a water source, it would pollute it and create many health concerns. These health concerns affect us in many ways because we often draw our water from places that we could have prevented the pollution in.

        The three main steps in wastewater treatment are primary, secondary, and tertiary treatment. The primary treatment aims to remove as much solid waste as possible. This is done by sedimentation. Secondary treatment aims to remove organic material. Microorganisms are put into the wastewater for a period of time and the tank is aerated so that the bacteria can decompose the organic material. Tertiary treatment is used in order to remove remaining small particles and finalize the cleansing. The wastewater is placed in a large tube filled with varying sizes of rock and sand. The remaining chemical particles attach themselves to the small particles of the rock and sand. The second step of tertiary treatment is disinfection, which removes the remaining bacteria. This is done by adding bleach for a few hours. Now bleach has to be removed, so the water will be filtered through plants which add sulfur dioxide gas that reacts with the bleach to form ions that don’t harm living organisms.

        So, through these processes it would seem that the water would be up to the specifications of drinking water. But, is this the reality of it?

Works Cited

Barringer, Felicity. "As ‘Yuck Factor’ Subsides, Treated Wastewater Flows From Taps." NYTimes. New York Times, 09 Feb. 2012. Web. 03 Mar. 2012. <http://www.nytimes.com/2012/02/10/science/earth/despite-yuck-factor-treated-wastewater-used-for-drinking.html?pagewanted=all>.

"Wastewater Treatment Water Use." Water Use: Wastewater Treatment. Web. 03 Mar. 2012. <http://ga.water.usgs.gov/edu/wuww.html>.

"WHO's Drinking Water Standards 1993." WHO's Drinking Water Standards. Web. 03 Mar. 2012. <http://www.lenntech.com/applications/drinking/standards/who-s-drinking-water-standards.htm>.

Procedure:

Day 1:

1. Add:

2. Once the simulation wastewater has come together, take 4 samples of 50 ml each and test them for initial values of pH, ammonia, and turbidity.

3. Collect the results for each sample.

Day 2:

1. Take 4 samples of water, test for values, and record.

2. Move water from the sedimentation take to the aeration tank and add the bacteria. Safety is of utmost importance when working with live microorganisms. Always handle with care.

Day 3:

1. Take 4 samples of water, test for values, and record.

2. Move water from aeration tank to the filtration tank.

3. After water filters, perform the disinfection and dechlorination process. Once again, safety is key.

Day 4:

1. Take 4 samples of water, test for values, and record final values.

2. Dispose of remaining water in a proper fashion. (If this whole process worked out, it should be able to be dumped into the nearest lake or river! However, that’s probably not recommended.)

Data

Initial tests

Primary treatment

Secondary treatment

Advanced/Tertiary treatment

Limitations/Improvements:

        One major limitation of this lab is that it is a small scale. The process had to be made small enough to be performed in a classroom. This could possibly affect the results of the lab. A way to improve this would be to go to the wastewater treatment facility and test each of these things. That would be a lot more accurate than this scaled down classroom version. In addition to that, the treatment plant may be willing to share the data that they have collected.

        Another limitation that goes along with that is that the wastewater wasn’t completely real. There were some real components, such as the microorganisms, and things representing real objects, but it could still be more realistic. It’s understandable that there are many sanitation and health concerns if real wastewater were to be used, but it would be more accurate when tested within the classroom. These first two improvements would aim to make the lab more realistic.

        A limitation in regard to turbidity is that the mixture wasn’t always mixed together completely. After the primary treatment you can see a large amount of variance amount the results. This is because turbidity was tested from the top, middle, and bottom nozzles of the holding tank. If the wastewater was mixed completely there would be no need to test from each nozzle and the results would be more even.

Conclusion:

        Does waste water treatment bring turbidity to levels acceptable for drinking water standards?

        Acceptable drinking water standards are anywhere under 5 NTU, preferably under 1 NTU. After the final stage of wastewater cleaning, it would appear that the wastewater is, in fact, safe for drinking. The final average of the turbidity is 2.0 NTU, which may not be perfect but is ultimately acceptable. It seems that throughout the process, turbidity was reduced a significant amount at each and every treatment stage. It dropped most significantly after the first treatment.

        Turbidity dropped so significantly after each treatment because each treatment was aimed at removing visible products as thoroughly as possible. This is justified by the somewhat low drop in the chemical ammonia in drinking water until the tertiary treatment when compared to the consistent drop in turbidity. Throughout every process the physical and visible contamination was removed, whereas other components were only removed after one treatment.

        So, looking at the overall result of all of the treated wastewater, all of the tested components ended up being right around the acceptable range of drinking water standards. The wastewater treatment has worked, creating water safe enough to be returned to a river.