chapter 1. Natural wastewater treatment systems : an overview -- chapter 2. Planning, feasibility assessment, and site selection -- chapter 3. Basic process responses and interactions -- chapter 4. Design of wastewater pond systems -- chapter 5. Pond modifications for polishing effluents -- chapter 6. Free water surface constructed wetlands -- chapter 7. Subsurface and vertical flow constructed wetlands -- chapter 8. Land treatment systems -- chapter 9. Sludge management and treatment -- chapter 10. On-site wastewater systems.