Quarantine all dogs in your kennel that are displaying giardia cysts. Do not take any new dogs into your kennel until two weeks after your disinfection process.
Disinfect all the kneels with a cleaner made with quaternary ammonium compounds. Apply the cleaner, and leave it for 30 minutes. Wash off the cleaner thoroughly with water.
Quarantine the kennels with grass runs. Do not open them for at least one month since the last infected dog used the kennel space. It is nearly impossible to get giardia out of grass. You must remove the source -- i.e., the infected dog -- and give the grass time to rehabilitate and return to normal.