The first treatment plants were based on mechanical or primary treatment only, removing particles and floating substances. The primary treatment was often succeeded by biological treatment, also called secondary treatment. Secondary treatment degrades organic substances in the wastewater, but removes only a small part of the nutrients nitrogen (N) and phosphorus (P) (see also the nutrient cycle). N and P are considered the major elements triggering algal blooms, N in saltwater and P in freshwater. Removal of nutrients requires tertiary treatment. Tertiary treatment involves chemical and biological processes as well as advanced membrane filtering.
This lecture gives an overview of processes used in modern water and wastewater treatment (see also semi-centralised wastewater treatments and advanced systems).
This book not only identifies the threats to human and ecological health that water pollution has and highlights the consequences of inaction, but also presents opportunities, where appropriate policy and management responses over the short and longer term can trigger employment, support livelihoods, boost public and ecosystem health and contribute to more intelligent water management.CORCORAN, E. ; NELLEMANN, C. ; BAKER, E. ; BOS, R. ; OSBORN, D. ; SAVELLI, H. (2010): Sick Water? The central role of wastewater management in sustainable development. A Rapid Response Assessment. United Nations Environment Programme (UNEP), UN-HABITAT, GRID-Arendal URL [Accessed: 05.05.2010] PDF