treatment of wastewater became recognized and accepted by the engineering profession as a viable treatment concept during the decade following passage of PL 92-500, and it is now considered routinely in project planning and design.
Other "natural" concepts that have never been dropped from use include lagoon systems and land application of sludges. Wastewater lagoons model the physical and biochemical interactions that occur in natural ponds, while land application of sludges model conventional farming practices with animal manures.
Aquatic and wetland concepts are essentially new developments in the United States with respect to utilization of wastewaters and sludges. Some of these concepts provide other cost-effective waste treatment options and are, therefore, included in this text. Several sludge management techniques, including conditioning, dewatering, disposal, and reuse methods, are also covered, as they also depend on natural components and processes. The sludge management (biosolids) procedures discussed in Chapter 9 of this book are compatible with current U.S. Environmental Protection Agency (EPA) regulations and guidelines for the use or disposal of sewage sludge (40 CFR Parts 257, 403, and 503).
1.1.2 Wastewater Treatment Concepts and Performance Expectations
Natural systems for effective wastewater treatment are available in three major categories: aquatic, terrestrial, and wetland. All depend on natural physical and chemical responses as well as the unique biological components in each process.
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