Treatment of agricultural wastewater usually involves physical, chemical and biological processes. A typical treatment system includes primary, secondary and, in some cases, tertiary purification stages.
The principle of operation of most one or two stage treatment plants is based on using physical (mechanical) effects, and therefore the variety of the facilities does not differ much in terms of construction and operation costs. In turn, secondary treatment plants can be divided into two large groups: traditional and alternative (close to natural conditions), which differ very much in terms of construction and operation costs.
Secondary treatment involves removal of suspended substances, solved organic and biogenic materials from wastewater, and is performed by microbial transformation and assimilation.
Treatment of agricultural wastewater. This biological process, which is performed by bacteria and fungi, the development of which is artificially stimulated in special tanks or depressions in the ground, which may be equipped with devices for mixing, aeration or additional surfaces for immobilizing and development of the biomass.
The traditional biotechnology which can be used for secondary purification of wastewater are:
- aerobic systems with suspended microbes, also known as biosludge systems (aeration basins with sludge recirculation – aerotanks; cyclic reactors – SBR; membrane bioreactors – MBR; oxidation ditches);
- aerobic systems with immobilized microbes (trickling filters – TF; rotating biological contactors – RBC).
Alternative (near-natural) biotechnologies which can be used for secondary treatment of wastewater, are:
- waste stabilization ponds;
- aerated ponds (lagoons);
- constructed wetlands.
