What type of curve shows the relationship between power and capacity in pump operation?

The correct choice is the P-Q curve, which specifically illustrates the relationship between power (P) and flow capacity (Q) of a pump. This graph is a crucial tool in pump engineering and helps operators understand how a pump performs under different flow rates. It allows engineers and operators to assess the efficiency of a pump across various operating conditions.

The P-Q curve displays how the power required by the pump varies with the flow rate, indicating the performance characteristics at different points. Typically, as the flow rate increases, the power required to maintain that flow will also change. This relationship is essential for optimizing pump operation and ensuring that energy consumption is efficient.

By focusing on this curve, users can make informed decisions about pump selection, sizing, and operation, ensuring that they meet the specific needs of their application while minimizing energy costs. This makes the P-Q curve an invaluable tool in water treatment and hydraulic systems design.