Health and hygiene aspects of spray irrigation

Land disposal of domestic wastewater has been practiced on a large scale in Europe for several decades, mainly for the purpose of irrigating crops or pasture. Recently, however, spray irrigation, one form of land disposal, has taken on new dimensions as it is considered a means of disposal of wastewaters which heretofore have been discharged directly to streams or lakes. The paper is a review of the health and hygiene aspects of wastewater treatment or wastewater reclamation by spray irrigation. Although the discussion is limited to spray irrigation because of its current popularity among communities and sanitary engineers, many of the basic principles are applicable to the other methods of land disposal such as surface flooding and ridge and furrow irrigation. The following conclusions relative to the health and hygiene effects of spray irrigation land disposal of wastewater can be drawn: Many of the detrimental health and hygiene aspects of land disposal should be significantly reduced by proper wastewater pretreatment including secondary treatment, filtration, and complete disinfection. By choosing a land disposal site that has from 5 to 10 ft of continuous fine soil, biological contamination of ground water can be avoided. The probability of inhaling pathogenic aerosols near a spray irrigation site may be significant. If ponding results in spray irrigation areas, mosquito breeding is enhanced. In areas where land disposal is the first step in a water recycle program, total dissolved solids, sodium, and nitrate nitrogen buildup in the ground water supply can be a problem. (44 references.)