Detection and alkaline inactivation of Cryptosporidium spp. oocysts and Giardia spp. cysts in drinking-water treatment sludge. (April 2021)

• Record Type: Journal Article
• Authors: Ogura, Allan Pretti; Sabogal-Paz, Lyda Patricia
• Is Part Of: Journal of water process engineering. Volume 40(2021)
• Publication Date: 2021-04
• Subjects: Immunomagnetic separation -- Polyaluminium chloride -- Protozoan -- Propidium iodide -- Calcium oxide -- Drinking-water treatment sludge; Water-supply engineering -- Periodicals; Saline water conversion -- Periodicals; Seawater -- Distillation -- Periodicals; Sanitary engineering -- Periodicals; Sewage -- Purification -- Periodicals; 627
• DOI: 10.1016/j.jwpe.2021.101939
• Languages: English
• ISSNs: 2214-7144

Abstract

Abstract: Removing and inactivating Cryptosporidium spp. oocysts and Giardia spp. cysts are a challenge for drinking-water treatments, mainly because of their small sizes and resistance to chlorination. Moreover, protozoan detection methods are expensive and subject to high variability and low reproducibility, especially in high turbidity water. This research aimed at detecting and inactivating cysts and oocysts in drinking-water treatment sludge. In jar test treatability assays, 110 NTU study water was treated with polyaluminium chloride to obtain the sludge. The chosen method for detecting cysts and oocysts was direct centrifugation with ICN 7X solution followed by the immunomagnetic separation (IMS) with two acid dissociations. The inactivation of cysts and oocysts was identified by the inclusion of propidium iodide as a vital dye when the cell walls were damaged. This method's analytical quality control, which was performed with the EasySeed® suspension, obtained recovery of 3.3 ± 2.0 % and 24.8 ± 8.0 % for oocysts and cysts, respectively. Besides, the Giardia spp. recovery met the standards recommended for water by the USEPA Method 1623.1. Magnetic microspheres were found attached to the protozoan in the microscope slides after IMS, indicating some limitations of this purification method. The alkaline treatment tested a dose of 27 mg CaO/100 mL for 3 and 5 days, obtaining inactivation of 1.85 and 3.0 log for oocysts and 2.05 and 2.14 log for cysts, respectively. In this context, the alkaline treatment may be feasible to reduce the microbiological risk in water treatment sludge, considering an economic assessment.