The document discusses the characteristics of sewage or wastewater. It describes the physical, chemical, and biological characteristics in detail. Sewage typically contains 0.5% or less solids, with the remainder being water. It discusses key measures like biochemical oxygen demand (BOD), chemical oxygen demand (COD), pH, dissolved oxygen, temperature, and turbidity. Sewage contains a variety of microorganisms including bacteria, fungi, viruses, and aquatic plants and animals. The types and amounts of microbes and organic materials present impact the treatment design.