![Black-and-white image showing several cubic measurements of various types](https://waterhistoryphl.org/wp-content/uploads/volume-of-sludge.jpg?w=300)
![Black-and-white image showing several cubic measurements of various types](https://waterhistoryphl.org/wp-content/uploads/volume-of-sludge.jpg?w=300)
![Black-and-white image of two cylinders on a white surface](https://waterhistoryphl.org/wp-content/uploads/emscher-sludge-bubbles.jpg?w=300)
Effects of Expansion of Gas Bubbles in Enscher Sludge Shown in Right-Hand Cylinder
![Black-and-white line graph showing two jagged lines on a grid](https://waterhistoryphl.org/wp-content/uploads/Dissolved-O2-in-Delaware-River.jpg?w=300)
Diagram Showing Decreased Amount of Dissolved Oxygen in Delaware River, 1913
![Black-and-white image of a table with numbers in columns](https://waterhistoryphl.org/wp-content/uploads/bacteria-in-delaware-river-torresdale-filters-1913.jpg?w=300)
Bacteria in Delaware River, Torresdale Filters, 1913
![1914 map showing the plan for the collection and treatment of sewage in Philadelphia.](https://waterhistoryphl.org/wp-content/uploads/1914-Plan-2004.058.0065-RESCAN-rev2-reduced.jpg?w=300)
Historic resources from our archives - images, maps, documents, and more.