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Background <p>Oil refinery (OR) facilities consume vast volumes of water during their processes, generating a large amount of wastewater (WW). The oil refinery wastewater (ORWW) contains toxic materials, and few microorganisms are believed to remain active in this environment.</p> Methods <p>Water samples were collected from an ORWW facility for nine months. After recording physical-chemical features, filtration and sedimentation were employed. DNA extraction was performed for all samples and the presence of targeted parasites was evaluated using real-time PCR. Genotype/subtype of positive samples was characterized using sequencing.</p> Results <p>Real-time PCR showed that from 76 ORWW samples, targeted protozoa were identified in 26 (34.2%) samples. Accordingly, <i>Blastocystis</i> sp., <i>Enterocytozoon bieneusi</i>, and <i>Giardia duodenalis</i> were detected among 9.21% (7/76), 25.0% (19/76), and 2.63% (2/76) of samples, respectively. <i>Enterocytozoon bieneusi</i> was the most common detected species in samples followed by <i>Blastocystis</i> sp. and <i>G. duodenalis</i>. There was a statistically association between the presence of <i>Blastocystis</i> sp. and the type of wastewater treatment plants (WWTPs). <i>Enterocytozoon bieneusi</i> genotypes BEB6 (3/5; 60%), C (1/5; 20%), and an unknown genotype were detected among samples. Also, <i>Blastocystis</i> sp., ST1 (2/4; 50%), ST3 (1/4; 25%), uncultured uncharacterized stramenopile (1/4; 25%) and ST2 (1; 100%), were characterized in samples. <i>Giardia duodenalis</i> was the assemblage AII (1/2; 50%). Phylogenetic analysis showed that <i>E. bieneusi</i> genotypes were grouped within the groups 1 and 2, human-infecting genotypes. In addition, <i>Blastocystis</i> sp., subtypes were clustered within subtypes isolated from humans.</p> Conclusion <p>This is the first study investigating intestinal protozoa in a super harsh condition. Our findings signify the concern due to the distribution of potentially pathogenic parasites to downstream farmlands through industrial treated wastewaters which are used for irrigation.</p>

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Molecular characterization of intestinal protozoa in an oil wastewater treatment facility; risk for contamination of downstream farmlands

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月18日

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  • Hanieh Mohammad-Rahimi,
  • Saeid Andalib,
  • Maryam Niyyati,
  • Hamed Mirjalali

摘要

Background

Oil refinery (OR) facilities consume vast volumes of water during their processes, generating a large amount of wastewater (WW). The oil refinery wastewater (ORWW) contains toxic materials, and few microorganisms are believed to remain active in this environment.

Methods

Water samples were collected from an ORWW facility for nine months. After recording physical-chemical features, filtration and sedimentation were employed. DNA extraction was performed for all samples and the presence of targeted parasites was evaluated using real-time PCR. Genotype/subtype of positive samples was characterized using sequencing.

Results

Real-time PCR showed that from 76 ORWW samples, targeted protozoa were identified in 26 (34.2%) samples. Accordingly, Blastocystis sp., Enterocytozoon bieneusi, and Giardia duodenalis were detected among 9.21% (7/76), 25.0% (19/76), and 2.63% (2/76) of samples, respectively. Enterocytozoon bieneusi was the most common detected species in samples followed by Blastocystis sp. and G. duodenalis. There was a statistically association between the presence of Blastocystis sp. and the type of wastewater treatment plants (WWTPs). Enterocytozoon bieneusi genotypes BEB6 (3/5; 60%), C (1/5; 20%), and an unknown genotype were detected among samples. Also, Blastocystis sp., ST1 (2/4; 50%), ST3 (1/4; 25%), uncultured uncharacterized stramenopile (1/4; 25%) and ST2 (1; 100%), were characterized in samples. Giardia duodenalis was the assemblage AII (1/2; 50%). Phylogenetic analysis showed that E. bieneusi genotypes were grouped within the groups 1 and 2, human-infecting genotypes. In addition, Blastocystis sp., subtypes were clustered within subtypes isolated from humans.

Conclusion

This is the first study investigating intestinal protozoa in a super harsh condition. Our findings signify the concern due to the distribution of potentially pathogenic parasites to downstream farmlands through industrial treated wastewaters which are used for irrigation.