Notes about the PQO file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The PQO file type is primarily associated with 'PhreeqcI'. PhreeqcI Version 2 is a computer program for simulating chemical reactions and transport processes in natural or contaminated water.