Agricultural wastewater treatment
Where land is available for ponds, settling basins and facultative lagoons may have lower operational costs for seasonal use conditions from breeding or harvest cycles.
[1]: 6–8 Animal slurries are usually treated by containment in anaerobic lagoons before disposal by spray or trickle application to grassland.
Excess sediment causes high levels of turbidity in water bodies, which can inhibit growth of aquatic plants, clog fish gills and smother animal larvae.
Common techniques include: Nitrogen and phosphorus are key pollutants found in runoff, and they are applied to farmland in several ways, such as in the form of commercial fertilizer, animal manure, or municipal or industrial wastewater (effluent) or sludge.
Raising animals accounts for 73% of antibiotics use globally, and wastewater treatment facilities can transfer antibiotic-resistant bacteria to humans.
Animal slurries require special handling and are usually treated by containment in lagoons before disposal by spray or trickle application to grassland.
Application of slurries to land overlying aquifers can result in direct contamination or, more commonly, elevation of nitrogen levels as nitrite or nitrate.
Some animal slurries are treated by mixing with straws and composted at high temperature to produce a bacteriologically sterile and friable manure for soil improvement.
Ascarid worms and their eggs are also common in piggery waste and can infect humans if wastewater treatment is ineffective.
Fresh or wilted grass or other green crops can be made into a semi-fermented product called silage which can be stored and used as winter forage for cattle and sheep.
Although milk is an important food product, its presence in wastewaters is highly polluting because of its organic strength, which can lead to very rapid de-oxygenation of receiving waters.
[citation needed] Wastewater from slaughtering activities is similar to milking parlour waste (see above) although considerably stronger in its organic composition and therefore potentially much more polluting.
Even land spreading has produced severe taste and odour problems for downstream water supply companies in the past.
