REPLACEMENT OF THE FILTER BED IN THE RAPID FILTRATION PROCESS AT THE SAN LORENZO WATER TREATMENT PLANT, CONSISTS OF REPLACEMENT OF THE FILTER BED IN THE 6 FILTERS OF MODULE No.1 BASED ON ZEOLITE MINERAL COMPOSED OF CALCIUM CLINOPTILOTITE, 45 CM. OF ADSORSIL HYBRID HZ1, (FIRST STAGE WITH 5 FILTERS), EL QUEMADITO, SIND. COSTA RICA. (EXPIRED)