Sludge Drying Beds, Essen Nord, Germany
Grit Chamber, Essen, Germany
Effects of Expansion of Gas Bubbles in Enscher Sludge Shown in Right-Hand Cylinder
Diagram Showing Decreased Amount of Dissolved Oxygen in Delaware River, 1913
Water, Water Everywhere – Philadelphia Record, 1937-03-14
Outhouse over the Schuylkill near Pottstown