Land based methods of wastewater treatment have been used for many years. There are several types of treatment methods used. In this article I provide a brief overview of the different types of these land based treatment methods and how they work.
The different types of land based methods of wastewater treatment can be identified based either on the rate of infiltration of the wastewater through the soil or how it is applied over land:
Overland Flow Method – A sloping land grown over with grass is used in this method of land treatment of wastewater. The wastewater is sprayed at the top of this slope via sprinklers or pipes. The wastewater then flows down the slope in a thin film over the grass and into collection pipes located at the end of the slope. This downward flowing wastewater undergoes biological, physical and chemical reactions as part of the treatment.
Subsurface Infiltration Method – This method employs soil absorption fields or drain fields lying below the surface layer of the soil. As the wastewater is released into this drain field, it is acted upon by the soil matrix. The treated wastewater then permeates down to the water table. Soakpit is an instance of this method.
Slow Rate Method – The wastewater is applied on a land surface with vegetation at a slow rate. The slow rate of application prevents wastewater runoff. The wastewater that is applied on this land is treated both by plants and microorganisms present in the soil. Some of the water is released into the atmosphere through transpiration by the plants. The remaining wastewater gets treated as it percolates down the soil. It submerges ultimately into the groundwater.
Rapid Infiltration Method – A large volume of wastewater is applied to the soil that permits high infiltration or percolation through the soil. The soil surface is barren or devoid of any form of vegetation. The soil matrix through which the wastewater percolates, acts upon the percolating wastewater, treating it in the process. The treated wastewater finally submerges into the water table.