Evaluation of waste stabilization ponds for the reduction of Giardia cysts

Abstract

Giardia cyst concentration was studied at the different lagoons of a system located at the Center for Water Research at La Universidad del Zulia. The calcium carbonate flocculation protocol was applied together with an immunofluorescent analysis procedure for recovery and detection of cysts, respectively. Samples were taken at the following sites: raw sewage (Site 1), facultative pond effluent (Site 2). maturation pond effluent (Site 3) and polishing pond effluent (Site 4). The following mean values of cysts and percentage of positive samples were obtained: Site 1: 561 (100%), Site 2: 72 (100%), Site 3: 16 (80%) and Site 4: 5 (60%). The results obtained during this investigation indicate that even though Giardia cysts were removed, there are still values four times higher than those reported in the United States for well established waste stabilization pond systems whose effluents are used for irrigation.

Keywords

• Giardia cysts
• stabilization ponds
• domestic wastewater
• reuse