This chapter describes the basic responses and interactions among the waste constituents and process components of natural treatment systems. Many of these responses are common to more than one of the treatment concepts and are therefore discussed in this chapter. If a waste constituent is the limiting factor for design, it is also discussed in detail in the appropriate process design chapter. Water is the major constituent of all of the wastes of concern in this book, as even a "dried" sludge can contain more than 50% water. The presence of water is a volumetric concern for all treatment methods, but it has even greater significance for many of the natural treatment concepts because the flow path and the flow rate control the successful performance of the system. Other waste constituents of major concern include the simple carbonaceous organics (dissolved and suspended), toxic and hazardous organics, pathogens, trace metals, nutrients (nitrogen, phosphorus, potassium), and other micronutrients. The natural system components that provide the critical reactions and responses include bacteria, protozoa (e.g., algae), vegetation (aquatic and terrestrial), and the soil. The responses involved include a range of physical, chemical, and biological reactions.
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