On a hot, summertime San Diego day, my 8-year-old self and a friend were riding bikes around the neighborhood. We were thirsty and several blocks from home when my friend stopped to use his bike tire to dam a stream of runoff water that was aggressively picking up pace on its way down the gutter. Someone up the street must have been watering their lawn or washing a car. He dared me to drink it, but I refused. I could see a rainbow sheen of either soap or motor oil from the road glistening on the top of the water. In his attempt to convince me the water was “safe” to drink, he hopped off his bike and laid flat across the sidewalk, his face inches above the trickling water. He began lapping up the water like a thirsty dog. His efforts to convince me had no effect on my decision to not drink the water, but for several days thereafter I was deeply concerned for my friend’s health. Fortunately, he survived. He didn’t even get sick, although I’m sure that soapy/oily water didn’t taste as good as he let on. My concern was based on him getting poisoned from the oil, or the dirt, or some other contaminant that anybody could have dumped into the gutter. Several years later, in junior high school, I was introduced to the microbial world of bacteria, viruses, and protozoa. I finally began to understand pathogens and how they spread, including through water.
At the beginning of the 2017-18 school year at Strong 21
Century Magnet School in New Haven, CT, a pair of students approached me at the beginning of class. It had been raining all weekend, and both boys were curious if it was safe to drink the water that was streaming along the sidewalks and into the storm drains. One boy was convinced that rain water was pure, so it would only have a little dirt in it but should be safe to drink. The other wasn’t so sure. I advised them not to drink the water and offered them a brief explanation about pathogens and toxins the water could have picked up along the way. As they returned to their class activity, I was reminded of my own experience as an 8-year-old. At this age, children have grown increasingly aware of their environment and know that there are risks out there, but may not understand why. Most children would hesitate to drink water from an untreated source, but probably do not understand why there is a health risk. They just know that drinking dirty water might make them sick. In this unit, I will use this relatively common and appealing wonderment to lead a study of water quality and an engineering project of water filtration.
I have been running the STEM lab at Strong School for three years. Our demographics are typical of New Haven, CT – about 50% Hispanic, 45% Black, and 5% White or other. All 380 students from kindergarten to fourth grade spend one hour a week with me in our STEM lab. During their STEM time, we study elementary science topics and practice engineering solutions to problems based on the science we have learned. Often one question will lead to a variety of other good questions, and before long we have a trail of learning several layers deep. As I began working with the Yale New-Haven Teacher Institute and Dr. Jordan Peccia, a Yale professor of Chemical and Environmental Engineering, I knew the topic of microbial water quality and treatment would be a part of our work. After several months of working closely with Dr. Peccia, I am pleased to present the following unit. It is written with third graders in mind, but can be adapted up or down if needed.
Like most good learning, this unit starts with a question – Is this water safe to drink? (Note that “safe” is a relative term and could be better phrased in terms of reducing risk.) Along the way, students will learn different ways water can be treated to make it less likely to get them sick. They will be introduced to microbes and learn how public drinking water is treated and sent to homes and businesses. Finally, they will match their scientific knowledge with their ingenuity and problem solving skill sets as they engineer a water filter out of various materials under the hypothetical situation, “If I was stranded on an island, how could I make clean drinking water?”