Imagine that you lived in the hot, sandy climate of Egypt, thousands of years ago. Your house would be a small mud hut baked by the summer sun, with little furniture and no running water. After helping your family harvest crops and tend fields and livestock all day, you would be mighty thirsty! But unlike today, grabbing a drink of water wouldn’t be as simple as turning on the tap. You’d have to collect rain and flood water, or gather it from the Nile River. And with a lack of indoor plumbing and the water treatment plants we have today, the water your body needed for life could just as easily make you sick…or worse. How would you feel if you had to drink water that tasted like dirt and looked even worse? Luckily, even in ancient times, early scientists put their heads together to solve this problem.
Early Water Wonderers
Although viruses and bacteria wouldn’t be discovered for thousands of years, these thinkers wanted to figure out a way to make their drinking water look, smell, and, even more importantly, taste better. Ancient Egyptians figured out that adding a metal called alum, which they mined from rocks, helped to separate the water from solid particles, a process called coagulation. The ions from the alum react with the water, causing the solid materials to stick together and sink, leaving clearer water on top. Ancient civilizations also used sand and gravel to trap solid particles, allowing cleaner water to flow through. Heating the water also was an early method of water purification. Evaporation of the water removed harmful elements, and the condensed steam was collected, a process called distillation. Today, we use the same basic principles on a large scale to clean our water.
Aqueducts–Water Works in Ancient Rome
If you ever wander the streets of Rome, you will encounter drinking fountains all over the city, often decorated with old, ornate sculptures. These fountains supply modern Roman citizens and travelers with cold, fresh drinking water from sources established more than 2000 years ago. Rome, even hundreds and hundreds of years ago, was a busy, bustling place. Water supplied from local wells and collected from rainwater and flooding was not adequate for its large population, and was easily polluted without modern plumbing and filtration systems. The ancient Romans built aqueducts that used gravity to carry water from mountain springs and freshwater sources miles away from the city straight to the homes of city dwellers. This system provided Rome’s many citizens with clean water for drinking, bathing, and irrigating their lush gardens. Made from cement, brick, and stone, most aqueducts ran underground, following the twists and turns of the land. Where necessary, bridges were built across waterways, some of which remain today. The steeper the downward slope, the faster the water flowed. Sedimentation tanks along these pathways slowed the water, which allowed solid particles to settle to the bottom. In some areas, the water flowed down cascades and drop-offs that exposed it to the air and helped to clean it. Not only did the aqueducts bring in clean water, they also helped to flush dirty water out of the city.
While advancements in engineering and technology have made the process of water purification safer and more efficient, the basic techniques haven’t changed all that much in hundreds if not thousands of years. Think of some other life-changing discoveries from long ago that have remained mostly the same…and what might we discover now that future civilizations will use the same way hundreds of years in the future?
For more about water purification check out our “Clean Water Act” box for a Lesson in Water Filtration. During your ENGINEERING DESIGN CHALLENGE you will investigate crystals, solubility, evaporation, and much, much, more.