Removal of Giardia spp. and Cryptosporidium spp. from water supply with high turbidity: analytical challenges and perspectives

Abstract

Giardia and Cryptosporidium species are a serious problem if present in water supplies. The removal of these protozoans and the adaptation of existing protocols are essential for supplying drinking water to developing countries. Considering this, the aim of this study is to evaluate, on a bench level, the removal of Giardia spp. cysts and of Cryptosporidium spp. oocysts from water with high turbidity, using polyaluminium chloride as a coagulant. Filtration using mixed cellulose ester membranes, followed, or not, by purification through immunomagnetic separation (IMS) was used for detecting protozoans. By evaluating the adopted protocol, without using IMS, retrievals of 80% of cysts and 5% of oocysts were obtained, whereas by using IMS, recoveries of 31.5% of cysts and 5.75% of oocysts were reached. When analyzing the coagulant performance, a dosage of 65 mg L(-1) showed contamination from protozoans in all the samples of filtered water. A dosage of 25 mg L(-1) presented protozoans in 50% of the filtered water samples. The results showed an improved performance for the 25 mg L(-1) dosage; therefore, the control of coagulation and adaptation of detection protocols must be evaluated according to the features of raw water and availability of local resources.

Ferric sulphate flocculation as a concentration method for Giardia and Cryptosporidium in filter backwash water

“…Although there were no outliers within the confidence interval established for this research (α ¼ 0.05), more repetitions would be an option for reducing data variability. Nonetheless, costs associated with the detection step by immunofluorescence assay (IFA) often limit repetition, particularly in developing countries (Maciel & Sabogal-Paz 2016). This effect on the coefficient of variation has also been reported in similar research on FBW , in which recovery assays by direct centrifugation with ICN 7X cleaning solution (MPBio ® ) and subsequent purification led Giardia spp.…”

“…Here we tested concentration by ferric sulphate flocculation, which is an acid-based flocculation technique and found coefficients of variation (CV) that did not comply with the established recommendations from Method 1623.1 (USEPA 2012). Although flocculation is low-priced when compared to MF (Maciel & Sabogal-Paz 2016;Andreoli & Sabogal-Paz 2017), its efficiency must also be assessed in different conditions, as the matrix quality parameters vary, causing protozoan cysts and oocysts to possibly fail to settle during concentration or, on an opposite prospect, cause the concentrate to be incompatible with purification or detection steps.…”

“…Filtering medium consisted of sand with size ranging from 0.30 to 0.59 mm. This bench-scale filtering was performed under a 100 m 3 m À2 d À1 maximum rate (Maciel & Sabogal-Paz 2016), which means that, within the period of 60 s, approximately 20 mL of filtered water should be produced. This was confirmed regularly by timed volume verifications.…”

Risk to human health from protozoan (oo)cysts in water treatment plants

“…The ease of implementation, the possibility of preserving (oo)cysts for future infectivity tests (MACIEL & SABOGAL-PAZ, 2016), and the use in research involving water supply sources in different regions in the world (ALMEIDA et al, 2015;BAUTISTA et al, 2018;SILVA & SCALIZE, 2020) were other criteria for choosing the aforementioned technique.…”

Dairy wastewater treatment employing microencapsulated Pseudomonas aeruginosa on low acyl gellan gum

“…in water, although it may present limited effectiveness in high-turbidity water samples. Other factors, such as greater laboratory complexity, execution time, and specialized human resources, impact the use of the method in developing countries (USEPA, 2012;Maciel and Sabogal-Paz, 2016).…”