Theory of Storage and Treatment-Plant Overflows

The effectiveness of storage in combination with a treatment plant for storm runoff depends on the capacities of the two facilities and the number, duration, and volumes of runoff events which these facilities must process. Computer simulation models can be used for direct evaluation; this paper presents a complementary theoretical method. The theory uses a probabilistic description of precipitation as determined from local records and develops statistics of untreated discharge through mathematically derived probability functions. A number of important assumptions are made since it is known that such problems can be mathematically unsolvable. The theory is probably not a practical substitute for computer simulation, but should provide a means for directing more detailed computer analysis towards the most cost-effective combinations of storage and treatment.