Selecting the appropriate UV lamp power for water treatment sterilization depends on several factors, including water flow rate, water quality, the level of disinfection to be achieved, and the design of the system. The following are some of the considerations: 

1. Water flow: Higher water flows usually require a higher wattage UV lamp to ensure that the microorganisms in the water are exposed for a sufficient amount of time. If the water flow is low, a lower wattage lamp can be used.

2. Water conditions: Suspended matter, turbidity and coloration in the water will affect the ability of the UV light to penetrate, so higher power or longer exposure times may be required for poorer water quality. Clean, clear water requires less UV. 

3. Level of disinfection required: Higher levels of disinfection may require higher power UV lamps to ensure that all potential pathogens are effectively inactivated. Lower levels of disinfection may be sufficient at lower power levels.

4. System design: The design of the equipment, such as the length of the water flow path, the speed of the water flow, and the choice of reflective material, all affect the effective utilization of UV light. A well-designed system can improve disinfection efficiency by optimizing the water flow path and contact time without necessarily using very high power lamp beads.