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CIWEM Good Practice in Water and Environment Management
Natural wastewater treatment
Natural wastewater treatment systems (NWT) are biological treatment systems that require no or very little electrical energy. This is in contradistinction to conventional treatment systems such as activated sludge (Table 1.1).1 Instead they rely on entirely natural processes, principally biochemical and in particular photosynthetic reactions, to provide the energy required for wastewater treatment. NWT systems are anaerobic or aerobic, and some have both aerobic and anaerobic zones. Because they are not energy-intensive processes, they require a greater volume or area to enable wastewater treatment to proceed to the level required. There is thus a trade-off: either more money is spent on land (either by purchase or by leasing) for NWT, or more money is spent on electromechanical equipment and electrical energy for conventional treatment processes such as activated sludge. This study gives an overview of technologies in the area of NWT.