TABLE OF CONTENTS Slow rate (SR) land treatment involves the controlled application of wastewater to a vegetated land surface. There are two basic types of SR systems:
Type 1. Optimum hydraulic loading, i.e., apply the maximum amount of water to the least possible land area; a treatment system.
Type 2. Optimum irrigation potential, i.e., apply the least amount of water that will sustain the crop or vegetation; an irrigation or water reuse system with treatment being of secondary importance.
Many of the system components (vegetation, preapplication treatment, transmission, distribution, etc.) may be identical for both types. The land area used, however, and the operational procedures will not be the same, so it is necessary to develop a unique design approach for each case.
In general, industrial operations with easily degraded wastes and municipalities in the humid parts of the country will seek to minimize land and distribution system costs, and will implement type 1 systems, in general. In the arid parts of the world, where the water itself has a significant economic value, it is often cost-effective to design a type 2 system.
Type 1 systems are based on the limiting design parameter (LDP) concept defined in Chaps. 2 and 3. The LDP for typical municipal wastewater and many industrial wastewaters will be either the hydraulic capacity of the soil or the nitrogen loading rate. For other industrial wastewaters the LDP may be metals, solids, organics, or other constituents as discussed in Chap. 3.
The...
