ENVR 1401 LAB EXERCISE Lab 11 Wastewater Treatment

Transcription

1 ENVR 1401 LAB EXERCISE Lab 11 Wastewater Treatment Name: SAFETY CONCERNS: Chemical splash goggles must be worn by everyone in the lab for the entire lab period. Goggles and a sterilizing cabinet have been provided in the lab classroom. Safety glasses are not permitted as a substitute. Students should be alert to the potential risk of breathing vapors from all samples of the Sewage Water and from the Bleach that will be used to chlorinate the processed effluent. To detect odor of samples, students should use the wafting technique -- Only check odors by wafting the odor towards your nose with your hand. Report all accidents, injuries and close calls to the teacher immediately. Report all spills and glass breakage or damage to the instructor immediately. Students are NOT to clean up spills or broken glass. WASTE DISPOSAL & LAB CLEAN-UP: Activated carbon should be placed in labeled waste beaker for carbon. Sand filter materials should be placed in labeled waste beaker for sand. DO NOT mix carbon and sand filter wastes to facilitate recycling. All remaining fluids and chemical waste should be placed in waste beakers as directed by lab instructor. Use the Buddy System to watch out for safety of other members of your lab group. Students should NOT drink any fluids in this laboratory exercise. Background: Laboratory activity modified from: Wards 1997 Water Pollution and Wastewater Treatment Lab Activity, Student Investigation. Water pollution and proper treatment of wastewater are critical modern environmental issues. Wastewater from domestic and industrial sources must be treated before being discharged into the environment to reduce environmental degradation, including ecological damage and potential impacts on environmental and human health. Sewage treatment methods simulate the natural processes of aeration, filtration and biological activity combined with chemical treatments. At a treatment plant, raw sewage is separated into solid and liquid components primarily through filtration (screening), sedimentation (settling) and by flocculation (chemical additives). The sludge that is produced is oxidized and digested by biological action and then dewatered. The remaining solid organic sludge matter may be used as fertilizer and soil conditioner depending on regulatory approvals. The liquid component is filtered, aerated and, after final sedimentation, is disinfected with chlorine. Theoretically, the liquid effluent is now potable or appropriate for a variety of other uses. As a TCEQ contractor, you will be investigating the basics of wastewater treatment. This could be used as a training module to be extended to the public through tutorials at public schools and science expositions. One popular venue for material of this type is the Texas Master Naturalist program. This volunteer organization is designed to educate citizens in the basics of the natural world, environmental quality, and beneficial environmental management, so that they can pass this information on through outreach and service to their communities. It is an organization of closet educators and is taught by experts in their respective fields. Even so, preparatory classwork is broad and informal. After completing the Master Naturalist program, citizen volunteers can operate parks, nature areas, youth education programs, or provide leadership in local natural resource conservation efforts.

2 Materials: Wastewater * (see notes on following page) Water samples ** (see notes on following page) Beakers 100 or 250 ml 3 per group Fine sand with scoop Medium sand with scoop Coarse (2 mm) sand with scoop Activated carbon Strainer (to rinse carbon) Cheesecloth (two 5 x 5 inch squares per group) Funnels (medium plastic for sand filter) Funnels (small for filter paper) Filter paper DI water bottles Bleach (2% by volume) 1 ml pipette (1 per hood) Ring stand & Iron ring Large waste beaker for used carbon (can be rinsed and reused) Large waste beaker for used sand (can be rinsed, dried, sieved and reused) Sewage Water Preparation Procedure: The water samples available for student use during this activity have been prepared. Wastewater was prepared in a one-gallon jug, about 3 days in advance of class to generate the ¼ - ½ gallon of wastewater needed per class using the following procedure: Day One fill the jug about ¾ full of water. Add soil; organic materials such as leaves, grass, orange peels; garlic powder; a few drops of food coloring; and 2 spoonfuls of baking soda. Cap the jug and shake. Let it sit overnight. Take a sample of the water and put in a clear glass bottle labeled control Day Two aerate the sample using an aquarium pump overnight. Take a sample of water and put it in clear glass bottle labeled aerated Day Three add 5g of alum per gallon of wastewater. Cap and shake. Leave overnight. Take a sample of water and place in a clear glass bottle labeled alum We did the steps above for you. You are starting on Step 1 below. Record all observations in the Data Table provided at the end of this exercise. Step 1. Three observation bottles are located at the front of the room: Control, Aerated, and Alum. 1. Gently shake each bottle, making sure the lid is tightly capped. 2. Observe each bottle for (A) presence, size, and type of observed solids, (B) clarity of the water, (C) odor (which requires you to carefully open each bottle and do a waft test), and (D) color. 3. Record each answer in the appropriate box in the table at the end of this exercise. a. Note: the water in the big sample jug, which you will use for experiments, has been taken to the alum stage and is equivalent to the alum bottle.

3 Step 2. Construct a simple sand filter system using a large funnel and ring stand as shown in the figure. 4. Construct the sand filter by lining the funnel with several layers of cheesecloth. Do not use all your cheesecloth! 5. Add a ¾ to 1-inch deep layer of coarsest sand (~ 2 mm or very fine gravel), then a ½ to ¾-inch layer of medium sand and topped with a ½ to ¾-inch layer of fine sand. Slightly dampen the sand filter with distilled water to minimize retention wastewater when the Alum water is filtered. Gravel Coarse Sand Fine Sand 6. Place a clean empty beaker beneath funnel, and gently pour a sample of the Alum water from the big jug through the sand filter. Be sure to collect 40 to 50 ml of water that has been filtered through the sand. 7. Note your observations of this Sand-Filtered Water on the Data Table. Step 3. Carefully remove the sand filter material and cheese cloth from the funnel and place in the appropriate waste container. Rinse and dry the funnel. 8. Place approximately ½ cup of activated carbon in a strainer and gently rinse over the sink until the water runs fairly clear. 9. Line the funnel again with layers of cheesecloth and fill the funnel approximately ½ full with carbon. 10. Place a clean empty beaker beneath funnel, and pour a sample of the Sand-Filtered Water through the activated carbon. Be sure to collect 30 to 40 ml of water that has been filtered through the activated carbon. 11. Note your observations of this Carbon-Filtered Water on the Data Table. Step 4. Chlorinate your water sample. This should only be done in the fume hoods. 12. Carefully add 0.5 to 1.0 ml of chlorine (sodium hypochlorite or bleach) to the 30 to 40 ml of Carbon-Filtered Water in the beaker. 13. Note your observations of this Chlorinated Water on your Data Table. Step 5. Carefully remove the activated carbon filter from the funnel and place in the appropriate waste container. Rinse and dry the funnel. 14. Fold a piece of filter paper in half and then in half again, holding three sides together and opening the remaining side to form a cone. Place the cone in the funnel. 15. Place a clean empty beaker beneath the funnel. Carefully and slowly pour the Chlorinated Water Sample through the filter paper cone. Be sure to collect at least 20 to 30 ml of this Final Effluent in your beaker. This step will take a while. Work on the lab questions while you wait! 16. Note your observations of this Final Effluent on your Data Table.

4 Questions: 1. At what stage of the activity did the appearance of the water change the most? Explain the evidence that supports your conclusion: 2. Explain the sand filtering process: 3. Which material in the sand filter removed the most particulates (solids) from the sample? Why? 4. Which step in the procedure removed or reduced the odor of garlic? 5. During which step was the greatest amount of color removed from the water? 6. What important function does the chlorine (sodium hypochlorite) serve? 7. Relate each step of the activity to the functioning of an actual sewage treatment plant (see Reference Websites and/or your Background). a. Explain how they are similar: b. Explain how they are different?

5 8. The quality of water entering the sewage treatment plant affects the entire process. Imagine an industrial spill of a toxic chemical, such as phenol, enters the sanitary sewer line and flows into the sewage plant. Explain how this toxic spill would affect the operation of the plant, both in the short term and in the long term. 9. When you are finished, I want you to write up a one page, attention-grabbing circular (in addition to the lab) that could inform an interested volunteer of the overarching themes of wastewater management, bringing in material you discovered during your research. Write as if you are an educated, stateemployed researcher, trying to inform a concerned citizen about wastewater and wastewater treatment. Remember: these citizens you are educating will be strong voices in their local communities, spurring their fellow men and women on to reform their wasty ways. Be strong but not over-bearing. Have fun with it! Here is an example (albeit about recycling):

6 Sewage Treatment Data Table Sample ID Solids Clarity Odor Color Control Aerated Alum Sand-filtered Carbon-filtered Chlorinated Final Effluent Revised: August 23, 2012