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Efficiency of chlorine and UV in the inactivation of Cryptosporidium and Giardia in wastewater.

ABSTRACT: Wastewater from different sources is contaminated by protozoan parasites including Cryptosporidium and Giardia. Many protozoan parasites are becoming resistant to chemical treatment. The challenge of finding alternatives is presented to researchers by exploring other methods of eliminating protozoan parasites from wastewater. The aim of this study was to assess the speciation and the viability of Cryptosporidium and Giardia in environmental samples with the specific objective of evaluating if effluent chlorination and UV affect the viability. Different doses of chlorine with different exposure times were experimented with both distilled water and waste water spiked with (oo)cysts derived from environmental samples. UV irradiation at different doses was also experimented using the same spiked samples. Two methods of quantification and detection, namely, microscopy and flow cytometry, were used in the experiment. Two vital dyes, Syto-9+PI and DAPI+PI, were the used for staining the collected wastewater samples. It was found that the (oo)cysts responded to chlorination and UV treatments with Giardia responding better than Cryptosporidium. Giardia responded very well to UV irradiations with almost 0 percent remaining viable after a low dose of UV. Cryptosporidium was found to be resistant to chlorination even at high doses but responded well to high UV doses. DAPI+PI dye gave a lower mean percentage viability values than Syto-9+PI. Flow cytometry gave higher mean percentage than microscopy from the results. It is concluded that UV is a promising alternative to Chlorine in removing Cryptosporidium and Giardia from waste water. Appropriate treatment method for wastewater is necessary to minimize water resources pollution when wastewater is released into water systems.

SUBMITTER: Adeyemo FE

PROVIDER: S-EPMC6513095 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundDespite their wide occurrence, cryptosporidiosis and giardiasis are considered neglected diseases by the World Health Organization. The epidemiology of these diseases and microsporidiosis in humans in developing countries is poorly understood. The high concentration of pathogens in raw sewage makes the characterization of the transmission of these pathogens simple through the genotype and subtype analysis of a small number of samples.Methodology/principal findingsThe distribution of genotypes and subtypes of Cryptosporidium spp., Giardia duodenalis, and Enterocytozoon bieneusi in 386 samples of combined sewer systems from Shanghai, Nanjing and Wuhan and the sewer system in Qingdao in China was determined using PCR-sequencing tools. Eimeria spp. were also genotyped to assess the contribution of domestic animals to Cryptosporidium spp., G. duodenalis, and E. bieneusi in wastewater. The high occurrence of Cryptosporidium spp. (56.2%), G. duodenalis (82.6%), E. bieneusi (87.6%), and Eimeria/Cyclospora (80.3%) made the source attribution possible. As expected, several human-pathogenic species/genotypes, including Cryptosporidium hominis, Cryptosporidium meleagridis, G. duodenalis sub-assemblage A-II, and E. bieneusi genotype D, were the dominant parasites in wastewater. In addition to humans, the common presence of Cryptosporidium spp. and Eimeria spp. from rodents indicated that rodents might have contributed to the occurrence of E. bieneusi genotype D in samples. Likewise, the finding of Eimeria spp. and Cryptosporidium baileyi from birds indicated that C. meleagridis might be of both human and bird origins.Conclusions/significanceThe distribution of Cryptosporidium species, G. duodenalis genotypes and subtypes, and E. bieneusi genotypes in urban wastewater indicates that anthroponotic transmission appeared to be important in epidemiology of cryptosporidiosis, giardiasis, and microsporidiosis in the study areas. The finding of different distributions of subtypes between Shanghai and Wuhan was indicative of possible differences in the source of C. hominis among different areas in China.

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Efficiency of chlorine and UV in the inactivation of Cryptosporidium and Giardia in wastewater.

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