The simplest, most appropriate treatment technique consists of directly introducing freshly generated greywater into an active, live topsoil environment. Figure 1 shows one time-tested greywater management approach which employs prefiltration to remove fibers and subsequent pressure infiltration using a piped distribution system that can be laid directly in the soil for plant irrigation. This treatment approach presupposes that the greywater does not contain any significant food waste and grease from kitchens. Figure 2 shows a system which relies either on gravity or batch dosing of raw greywater into a shallow soil environment see Nutricycle . The ultra-low flush toilet used in this investigation was a vacuum toilet using about one pint of water per flush.
Sewage also contains pathogens capable of spreading disease.
The great majority of these pathogenic organisms are derived from toilet waste which endanger the drinking water supply. The risk of bacterial communication from the untreated greywater was estimated by the research team as low. The relatively high numbers of general bacteria are probably related to the high bacterial growth rate in the plumbing system itself. The human pathogens do not, as a rule, find growing conditions hospitable outside the human body. Later data suggest that the amount of phosphates in detergents has, in recent years, been lowered significantly.