The Water and Drainage History of Philadelphia, Part 7
Volume of Sludge from 1,000,000 Gallons of Sewage
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