Land Treatment of Wastewater
Where there is adequate land available and the soil is able to readily process the wastewater as it passes down through it by means of physical, chemical, and biological processes, the wastewater from the treatment plant can be utilized as a means of irrigating crops. This can be accomplished through slow-rate infiltration where the disinfected wastewater is applied either by spraying, flooding, or irrigating furrows and part of the liquid evaporates and the plants utilize the other part. Rapid infiltration is used to polish and recover the wastewater effluent after pretreatment when large quantities percolate down through permeable soils into the water table. Wells can be used to extract the water and utilize it again. Overland flow is a process where the wastewater effluent passes over gently sloped, compact soil and the soil and its microorganisms form a gelatinous slime similar to a trickling filter, which removes the solids, pathogens, and nutrients. The water at the bottom of the slope if it meets appropriate standards can then be discharged or further treated.