When the Next Generation Science Standards (NGSS) were adopted in our state, it was like a STEAM roller (pun intended!) in that it was inevitable and unstoppable, and teachers needed to adapt. Our school district wouldn’t let us be flattened, however, and offered various staff development trainings.

I signed up for a training session about the nitrogen cycle, and wandered through the first few days wondering if we’d ever have time in the school year to cover all of the content expected of us. I also found that the water, carbon, nitrogen, and phosphorus cycles were making my head spin. The connections with many other subjects, traditionally taught separately, was new to me, and I was intimidated by the expectations.

However, during a discussion about the nitrogen cycle, I had a helpful revelation. For the first time, I realized that it’s through plants that our atmosphere becomes an integral part of our bodies. I always suspected I was full of hot air, but apparently, it’s quite true!

If you’re like me, and need a little refresher on this critical cycle in nature, it starts when nitrogen is plucked from the air and turned into a form that plants can use. Later it’s consumed by we humans or other animals in the form of proteins, and we then return some of the nitrogen back to the air or pass it along to other organisms. I suppose I had long known about this cycle, but it wasn’t until I heard a plant biologist explaining the intricacies of symbiotic bacteria and nitrogen fixation that it really hit home.

One big question remained: How do we help students realize all these connections?

Understanding the connections

In the past, when I wanted to help students make connections between what we were doing in the classroom and real-world applications, I’d invited guest speakers to share their experiences in chemistry. In my case, these speakers included former students who were in master’s programs, medical school or summer internships in chemistry-related fields. These students shared fascinating information about their current research and breakthroughs, as well as practical tips on how to survive college.

My fellow chemistry teachers and I were fortunate to be partners in an AAAS volunteer program that placed retired scientists in schools to work with students in a variety of ways. Our volunteer, who also doubled as our ACS Science Coach, was a former analytical chemist, and now a science writer. He created slideshow presentations on a wide range of topics, working closely with the chemistry teachers at our school to make sure the topics were interesting and pertinent to the topics we taught. Former and current students also served as guest speakers.

Plant biology wasn’t something I knew much about beyond my hobby as a gardener. However, I was aware our school had a robust horticulture program — that might be a good source to connect with to help me bring these concepts closer to home for my students.

Local resources

As it turned out, I diverged in a slightly different direction, and I didn't have to bug our horticulture teacher after all. At the end of the week of teacher training, a presenter described how local resources could help teachers demonstrate connections between the content and the real world. One resource that caught my attention was our local water company, Washington Suburban Sanitary Commission (WSSC). They offered a wide range of classroom resources, such as hands-on experiments for elementary classrooms and visits to their wastewater treatment plants. Here was a chance to help students see the links between chemistry content and real-world concepts; AND it was all free of charge!

Turning opportunity into action

With my nose to the grindstone at school, I had little time to contemplate, let alone plan, any student field trips. I knew they required a lot of work, and who had time for them? Fortunately, my involvement in ChemClub and Science Coaches programs started changing my outlook. These programs provided grant money that could be used to cover bus transportation for students and a substitute teacher for myself. Maybe we could take a few short field trips, after all?

There were many local places to visit, apparently. My Science Coach was very enthusiastic about them as well — he even had contacts and ideas for other places to visit. I just had to open my eyes. These programs encouraged me to overcome my initial reluctance and make these opportunities a reality.

I found the “Sewer Science” program offered by WSSC to be particularly captivating. It is designed for students to visit a wastewater treatment plant, conduct hands-on experiments, and then get a tour of the facility — and it is free! The only hurdles I faced in considering this as a field trip was that I needed to arrange for transportation, and that the facility could only accommodate groups of 30 students at a time. That meant I couldn’t take my classroom students (which numbered well over 100) on a single trip, and going multiple times didn’t make sense financially or logistically.

Luckily, I found it would work well and benefit the smaller ChemClub student population. ChemClub is an extracurricular club open to any students, whether or not they’re taking chemistry. (In the future, I’d like to find a way to bring this program to the rest of my chemistry students. Perhaps we could replicate the experiments and discussions in my classroom to some extent.) So, after learning about what would be involved, I applied for a ChemClub Community Activities Grant to help cover some of the costs. Once the paperwork and permission forms were turned in, off we went!

Valuing the experience

Figure 1. Students using gravity filtration to measure turbidity before and after filtration.

The water treatment plant that we visited was a smaller than average facility, treating a more rural part of our generally suburban county outside of Washington, D.C. The day started with everyone donning PPE and gathering around several tables with various lab equipment set up with funnels, flasks, and filter paper.

The staff were very gracious, and seemed excited to have our rambunctious teens visiting. Otherwise, it was business as usual for the plant, with trucks periodically driving off with trailers filled with waste sludge.

The hands-on activity was billed as a way for students to see how wastewater was treated. I anticipated a simulated lab, with water and sand, something we’ve done before in class. Students had to complete a liability waiver, which I took to mean “wear goggles during the simulated lab.”

It was a surprise, then, when the staff arrived with several gallon milk-jugs of actual wastewater. “Be sure you wear your goggles and gloves!” Indeed. The brown stinky stuff was as real as it gets. Apparently the staff had just pulled it out of the inflow and brought it in. Students added a coagulant for settling, while one of the techs attempted to get the microscope to view the bacteria wiggling around. No luck — but the brown gunk settled and students decanted as much of the clear liquid at the top as possible, following it up with a filtration. Some chemical tests were done on the clearer liquid, and we watched a well-made PowerPoint presentation explaining the process of wastewater treatment from start to finish. Some kids watched, but most were engrossed with their lab activity. It didn’t smell as bad as I thought … but I told them all more than twice to wash their hands before lunch!

Figure 2. An infographic depicting the wastewater treatment cycle. Image used with permission from WSSC.

After we finished the lab activity, we had a detailed walking tour of the facility. Coincidently, our guide was a graduate of our own county’s school system, who had made a career out of managing the plant. We started by observing the detritus caught from the initial screening process, removing indigestible solids like plastic and metals. After initial settling, it moved into tanks with hungry bacteria. Our guide explained that the bacteria helped digest the waste, and a certain bacteria level was maintained naturally, with minimal monitoring, even when temperatures dipped.

It was surprising to learn how “hands-free” the water treatment process was, despite all the tanks and technology that surrounded us. Toward the end, we saw the process in which the remaining sludge is squeezed to remove excess water, and mixed with lime to bring up the pH to “kill” the bacteria (which I took to mean reduce its ability to cause infection). After the water was squeezed out and compacted, the solids were then shipped out for non-agricultural land application. That was one stinky room!

At the very end, we saw a small trickling stream of clear outflow where the cleaned water exited after a month of treatment. Quite an operation for such an anticlimactic ending. But, that’s exactly what the plant is supposed to do!

Reflecting on the opportunity

The students were very excited about the whole experience. Of course, a day off from traditional “school” is fun, but they also learned some chemistry at the same time. Several NGSS standards were on display as well. These included the chemical concepts of bond energy, rates of reactions, and matter cycling through aerobic and anaerobic processes. Students also learned about the very real need to use mathematics to model the cycling of the sewage matter and the flow of energy among organisms in the man-made ecosystem of the sewage treatment plant. I was especially glad to have had the opportunity to invite some of my “on level” chemistry students (typically students with limited English proficiency or learning challenges) to join the ChemClub field trip. Nobody fell in the tanks, everyone kept their goggles on, and washed their hands. As an unexpected bonus, the facility even provided lunch, and covered the cost of our bus transportation! 

Going forward, I think this activity might become an annual pilgrimage. I need to scale it up to include more students — after all, some of my students had never even been on a field trip. This could perhaps involve bringing a guest speaker from WSSC to my classroom, then following this up with hands-on activities as safety and practicality allow. There was no assessment this time around, but it wouldn’t have been too difficult a task for students to write about their experiences and demonstrate where they saw various chemical concepts in action at the treatment plant.

Overall, the experience was convenient, inexpensive, pertinent, and interesting. It helped students make connections between chemistry and other fields like environmental science, municipal management, and modern conveniences we take for granted. It was heartening to learn that these field trip opportunities are literally everywhere — including right under our noses, just like nitrogen! NGSS helps students make connections between what initially seem like disparate scientific concepts and aspects of our way of life — but are actually all intimately connected. Little did I know it would do the same for me as an educator. It helped reveal obvious truths that were always there. I just had to look!

Photo credit:
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