shallow subsurface disposal technique is discussed in detail. Process Flood irrigation means discharging water onto a level plot so as to cover or flood the entire plot. Earthen berms or borders are used to contain the effluent within the plot. Generally, multiple plots are used and the discharge alternated between them. Generally, grasses CONVENTIONAL SYSTEM MODIFICATIONS are irrigated in this way. After the growing season or during winter, the flow is diverted to a backup disposal system, which allows year- round disposal and a chance for the plots to rest and the organic matter accumulated to decompose. In some climates, perennial grasses can be irrigated throughout the year. An aerobic treatment unit is recommended if odors could cause a problem, and a sand filter is recommended to further purify the effluent before it is disinfected and applied. Furrow irrigation means discharging water into ditches or channels between rows of plants. This technique is used most often on above- ground vegetable crops, cotton, flowers, or any other aboveground plants that do well as row crops. The same restrictions and require- ments that exist for flood irrigation exist for furrow irrigation, save that the distribution system must be designed to supply the furrows. Sprinkle irrigation means spraying effluent into the air with sprin- klers. This results in an even distribution of water, but evaporation can remove a significant portion of the water. The droplets of water can be carried by the wind and become a health hazard at distances up to one-half mile. In addition, aboveground food crops should never be irrigated by sprinkling with sewage effluent. Here again, aerobic treatment and sand filtration are desirable, and disinfection mandatory. Design for year-round use in freezing climates can be tricky. Additionally, this method should not be used on soils with a percolation rate slower than 30 min per in. Trickle irrigation means the slow dripping of water through a very low pressure distribution system placed in furrows or