As the population of a collection system increases, what happens to the ratio of peak flow to average daily flow?

As the population in a collection system increases, the ratio of peak flow to average daily flow tends to increase. This is primarily due to several factors related to demand patterns in wastewater systems.

When more individuals are using the system, the peak flows— often occurring during times of high water use, such as mornings or evenings—can increase significantly compared to the average daily flow. This is because the average daily flow is calculated over a 24-hour period and considers overall usage, while peak flows can reflect momentary surges in water usage that are not as predictable and can vary greatly depending on the time of day or day of the week.

The increased ratio of peak flow to average daily flow demonstrates a more pronounced variability in usage as the population grows. Systems must be designed and operated with this peak flow in mind, as it is critical for ensuring that capacity is adequate to handle those surges without causing problems such as overflow or backups.

In summary, as the population increases, the dynamics of water usage lead to greater peaks relative to the average, resulting in an increased ratio rather than a decrease or a stable ratio. Therefore, the appropriate understanding aligns with the notion that the peak flow to average daily flow ratio will increase with growing population demands.