What are the requirements related to the rated capacity of a water treatment plant?
The rated capacity of a water treatment plant is based upon the ‘firm capacity’ of the facility. Firm capacity refers to the available capacity of a system or process with the largest unit out of service. Thus, the reliability and redundancy of a water treatment plant's equipment and process units are integral to the plant's firm capacity.

Reliability and redundancy requirements are based on installed redundant equipment and process units. Using analytical or statistical methods such as ‘predicted downtime,' ‘mean time between failure’ or other types of failure mode analysis to justify the reliability of systems or processes within a water treatment plant is not an acceptable means of determining the rated capacity of the plant. A water treatment plant's rated capacity is solely based on its firm capacity.

The rated capacity of a water treatment plant is critical in determining when an expansion of a plant is required. The Arizona Department of Environmental Quality's (ADEQ) Engineering Bulletin No. 10, "Guidelines for the Construction of Water Systems", Chapter 4, Section A.6 states: "Expansion of the plant is indicated when the maximum daily demands of the system approach the rated capacity of the existing plant. As a general rule, steps to provide additional treatment capacity should be taken at least 5 years before present capacity is reached to allow sufficient time for engineering investigations, design, financing and construction." For more information, please call 602-372-2861.

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1. Is emergency power required for a water treatment plant?
2. Is emergency power required for groundwater production facilities?
3. Is emergency power required for distribution system facilities?
4. What are the requirements for equipment and process redundancy for a water treatment plant?
5. What are the requirements related to the rated capacity of a water treatment plant?
6. What are some key issues when converting a groundwater production facility to a water treatment plant?
7. What are the design requirements for venting wet wells, clearwells, tanks and reservoirs?
8. What are the design requirements for wet well, clearwell, tank or reservoir overflows?
9. What are the design requirements for entry hatches on wet wells, clearwells, tanks and reservoirs?
10. Can pump seal water be discharged to a pump wet well?