Occurrence and removal of Giardia spp. cysts and Cryptosporidium spp. oocysts from a municipal wastewater treatment plant in Brazil

Integrating life cycle assessment with quantitative microbial risk assessment for a holistic evaluation of sewage treatment plant

An integrated approach was employed in the present study to combine life cycle assessment (LCA) with quantitative microbial risk assessment (QMRA) to assess an existing sewage treatment plant (STP) at Roorkee, India. The midpoint LCA modeling revealed that high electricity consumption (≈ 576 kWh.day^-1) contributed to the maximum environmental burdens. The LCA endpoint result of 0.01 disability-adjusted life years per person per year (DALYs pppy) was obtained in terms of the impacts on human health. Further, a QMRA model was developed based on representative sewage pathogens, including E. coli O157:H7, Giardia sp., adenovirus, norovirus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The public health risk associated with intake of pathogen-laden aerosols during treated water reuse in sprinkler irrigation was determined. A cumulative health risk of 0.07 DALYs pppy was obtained, where QMRA risks contributed 86 % of the total health impacts. The annual probability of illness per person was highest for adenovirus and norovirus, followed by SARS-CoV-2, E. coli O157:H7 and Giardia sp. Overall, the study provides a methodological framework for an integrated LCA-QMRA assessment which can be applied across any treatment process to identify the hotspots contributing maximum environmental burdens and microbial health risks. Furthermore, the integrated LCA-QMRA approach could support stakeholders in the water industry to select the most suitable wastewater treatment system and establish regulations regarding the safe reuse of treated water.

Synergism in sequential inactivation of Cryptosporidium parvum with trypsin and UV irradiation

Cryptosporidium, a protozoan parasite, in wastewater presents a major public health concern for water safety. However, bactericidal efficiencies of conventional disinfection methods towards Cryptosporidium oocysts are still hampered owing to the presence of their thick outer wall. In this study, we present a novel UV inactivation process where the efficiency has been significantly enhanced by addition of a trypsin pretreatment stage. Notably, inactivation (log-reduction) of oocysts was noted to be 73.75-294.72% higher than that obtained by UV irradiation alone, under identical conditions. Experimental observations and supporting mechanistic analyses suggest that trypsin led to cleavage of the protein layers on the oocyst wall, facilitating penetration of UV radiation into the oocysts leading to degradation of their genomic DNA (gDNA). The dissociative effect of trypsin on the oocyst wall was indicated by the fact that 64.50% of oocysts displayed early apoptosis after trypsinization. Imaging by scanning electron microscopy indicated that this combined treatment led to substantial disruption of the oocyst coat, deforming their shape. This resulted in the release of cellular proteins and gDNA, their concentrations in bulk solution increasing by 1.22-8.60 times. As UV irradiation time was prolonged, gDNA was degraded into smaller fragments with lower molecular masses. Both laddering and diffuse smear patterns in gel analysis indicated significantly detrimental effects on gDNA and viability of oocysts. Overall, this study demonstrated enhancement of UV inactivation of Cryptosporidium oocysts by trypsin and explored the underlying mechanisms for the process.

Performance of sewage treatment technologies for the removal of Cryptosporidium sp. and Giardia sp.: Toward water circularity

Cryptosporidium sp. and Giardia sp. are parasites that cause diseases in the population. Most of parasite diseases regarding the consumption of drinking water polluted with sewage are caused by Cryptosporidium sp. or Giardia sp. it is because of the incomplete disinfection of the wastewater treatment. Therefore, in this work the removal or inactivation efficiency of different treatment technologies presented by around 40 scientific studies was evaluated, with a view to water circularity. For Cryptosporidium sp., we conclude that the most efficient secondary technologies are aerobic technologies, which remove between 0.00 and 2.17 log units (Ulog), with activated sludge presenting the greatest efficiency, and that the tertiary technologies with the greatest removal are those that use ultrasound, which reach removal values of 3.17 Ulog. In the case of Giardia sp., the secondary technologies with the greatest removal are anaerobic technologies, with values between 0.00 and 3.80 Ulog, and the tertiary technologies with the greatest removal are those that combine filtration with UV or a chemical disinfection agent. Despite the removal values obtained, the greatest concern remains detecting and quantifying the infectious forms of both parasites in effluents; therefore, although the technologies perform adequately, discharge effluents must be monitored with more sensitive techniques, above all aiming for circularity of the treated water in a context of the water scarcity that affects some parts of the world.

A probabilistic assessment of microbial infection risks due to occupational exposure to wastewater in a conventional activated sludge wastewater treatment plant

Exposure to pathogens during wastewater treatment could result in significant health risks. In this paper, a probabilistic approach for assessing the risks of microbial infection for workers in an activated sludge wastewater treatment plant is presented. A number of exposure routes were modelled, including hand-to-mouth and droplet ingestion of untreated wastewater, droplet ingestion and inhalation of aerosols after secondary treatment, and ingestion of sludge during drying. Almost all workers exposed to untreated wastewater could be infected with the three selected potential pathogens of pathogenic E. coli, Norovirus and Cryptosporidium spp. Hand-to-mouth ingestion is the single most significant route of exposure at the head of works. There is also a risk of infections resulting from ingestion of droplets or inhalation of aerosols at the aeration tanks or contaminated hands at the clarifiers during secondary wastewater treatment. For sludge, the risks of infection with Norovirus was found to be the highest due to accidental ingestion (median risks of 2.2 × 10^-2(±3.3 × 10^-3)). Regardless of the point and route of exposure, Norovirus and Cryptosporidium spp. presented the highest risks. The study finds that occupational exposure to wastewater at wastewater treatment plants can result in significant viral and protozoan infections. This risk assessment framework can be used to establish and measure the success of risk reduction measures in wastewater treatment plants. These measures could include the use of personal protective equipment and adherence to strict personal hygiene.

The performance evaluation of wastewater service: a protocol based on performance indicators applied to sewer systems and wastewater treatment plants

This research aimed to identify a tool to objectively analyse the performance and the environmental contextualisation of sewer systems (SwSs) and wastewater treatment plants (WWTPs). This procedure performs assessment by calculating performance indices which could be subsequently applied to SwSs and WWTPs with different characteristics. The proposed tool can be applied conveniently over the years by managers of integrated urban water management systems for the analysis of different realities also allowing the evaluation of the effects of upgrades carried out during the management phases. The proposed analysis allows the optimisation of SwSs and can profitably guide the choice and the priority among possible interventions for the sewerage infrastructure and WWTPs providing a verification and evaluation protocol as well as a financial planning tool.

Detection and removal of Giardia spp. cysts and Cryptosporidium spp. oocysts by anaerobic reactors in Brazil

The discharge of raw wastewater into the environment can be a contamination source of Giardia spp. cysts and Cryptosporidium spp. oocysts. The UASB (Upflow Anaerobic Sludge Blanket) reactor is the most popular technology applied for wastewater treatment in Brazil, nevertheless there is little information concerning its capacity for (oo)cyst removal. In this context, this study investigated the occurrence and removal of Giardia spp. cysts and Cryptosporidium spp. oocysts by three different UASB reactors (i.e. Reactor A, B, and C) treating different wastewater types. In the wastewater influent, the concentration varied from 493.3 to 14,000 cysts·L^-1 for Giardia spp. and from 'not detected' to 53.3 oocysts·L^-1 for Cryptosporidium spp.. The (oo)cyst concentration increased after the anaerobic treatment in Reactors A and B, while Giardia spp. log-removal of 0.5 ± 0.2 was found in Reactor C. The increment in (oo)cyst concentration may happened due to the inefficacy for (oo)cyst removal by the specific UASB reactor and/or due to the reduction of matrix interference for reactor effluent samples in the detection method. The results suggest that hydraulic retention time (HRT) may be the key parameter for Giardia spp. removal by the UASB reactor. Furthermore, no parameter analysed (physical-chemical and indicator microorganisms) showed a common correlation with the (oo)cyst concentration in the three UASB reactors. Considering that official data of cryptosporidiosis and giardiasis cases are rarely reported in Brazil, monitoring Giardia spp. cysts and Cryptosporidium spp. oocysts in wastewater could be an alternative to estimate the occurrence of diseases in the served population.

Investigation of Toxoplasma gondii in wastewater and surface water in the Qinghai-Tibet Plateau, China using real-time PCR and multilocus genotyping

Toxoplasma gondii is a protozoan parasite, causing one of the most prevalent parasitic infections in the world. In the present study water sources of the Qinghai-Tibet Plateau (QTP), China, where the hygienic infrastructure is still developing, were investigated. A total of 214 water samples of 10 L volume, were collected from wastewater treatment plants (WWTPs), a slaughterhouse and rivers. The samples were filtered and then analysed using real-time PCR and multilocus genotyping. T. gondii DNA was found in four (1.9%) samples representing T. gondii type I; in one of them T. gondii-like oocysts were also confirmed microscopically. The approximate level of contamination of positive samples ranged between 30 and 2300 T. gondii sporozoites. The results of this study confirmed that T. gondii is present in wastewater in the greater metropolitan area of Xining and a neighbouring county. Contamination of wastewater at this level constitutes rather a moderate source of Toxoplasma infections in humans and animals. It suggests, however, a link between environmental exposure of animals, meat processing facilities and WWTPs. To our knowledge, this is the first investigation describing T. gondii detection in wastewater and environmental water samples collected from the territory of P.R. China using sensitive molecular tools.

Removal of protozoan (oo)cysts and bacteria during microalgae harvesting: Outcomes from a lab-scale experiment

The efficiency of microalgae harvesting on the removal of Giardia spp. cysts, Cryptosporidium spp. oocysts, total coliforms, Escherichia coli, Enterococcus spp. and Clostridium spp. was assessed in lab-scale experiments (Jartest and Flotatest) using effluent from a flat panel photobioreactor used for Chlorella sorokiniana cultivation. Three harvesting methods were evaluated: (1) flocculation induced by pH modulation followed by sedimentation (pH-SED), (2) flocculation induced by pH modulation followed by dissolved air flotation (pH-DAF), and (3) coagulation using an organic coagulant (Tanfloc SG) followed by dissolved air flotation (Coag-DAF). The results indicated that the three harvesting methods were efficient in removing protozoan (oo)cysts and bacteria, achieving percentages of removal higher than 97% for all the analyzed pathogens. Among the three methods, pH-SED showed the best removal performance: 99.60% (2.5 log) for Giardia spp. cysts, 100% (>6.3 log) for total coliforms, 100% (>4.6 log) for Escherichia coli, 100% (>5.8 log) for Enterococcus spp. and 99.96% (3.6 log) for Clostridium spp. Clostridium spp. seemed to be more tolerant to the harvesting methods than the other groups of bacteria analyzed in the study, and its presence was positively correlated to the presence of Giardia spp. cysts.

Cryptosporidium and Giardia in urban wastewater: A challenge to overcome

This study aimed to quantify Giardia and Cryptosporidium in disinfected water reuse samples from two Wastewater Treatment Plants (A and B), which were quantified by USEPA 1693/2014 Method. Giardia was found in 35.8% of the total samples (<0.03 to 16 cysts/L) while Cryptosporidium in 30.2% (<0.03 to 25.8 oocysts/L). This study highlights the presence of both parasites in water for reuse despite treatment processes for their removal, which means there is a challenge to overcome. Their presence is preoccupant even though in low concentrations because the infectivity dose is low coupled with high prevalence in the global population. The practice of water recycling is valuable for sustainable water management and it is in line with Sustainable Developments Goals but should not threaten human health. Tackling this issue is more critical in developing countries because treatment processes are often more limited, the monitoring data from water reuse are not always available, the lack of regulation for water reuse quality and the lack of planning for its sustainable usage.

Performance of a small-scale wastewater treatment plant for removal of pathogenic protozoa (oo)cysts and indicator microorganisms

The protozoa Giardia and Cryptosporidium are associated with numerous outbreaks of waterborne diseases worldwide. This study aimed to evaluate the concentration of Giardia spp. cysts, Cryptosporidium spp. oocysts, total coliforms, Escherichia coli and Clostridium perfringens in raw wastewater and their removals at UASB reactor, activated sludge system (operated conventionally and extended aeration) and slow sand filtration. Giardia spp. cysts were present in 100% and Cryptosporidium spp. oocysts in 31.4% of the analysed wastewater samples. The UASB reactor followed by activated sludge system obtained approximately 2.0 log of removal for total coliforms and E. coli, whereas for C. perfringens and Giardia spp. cysts, it obtained 1 log. There was a high percentage of (oo)cysts still viable after secondary treatment, therefore, the risk of contamination of water courses and, consequently, for public health is considerable. However, after tertiary filtration, no (oo)cysts were found in any of the filtered effluent samples, being a good option for future reuse. Seasonal variations did not affect the concentrations and removals of microorganisms observed. Lack of correlations of concentrations of indicator microorganisms and (oo)cysts raise caveats and doubts regarding the true microbiological quality when using only indicator microorganisms.

Black water treatment by an upflow anaerobic sludge blanket (UASB) reactor: a pilot study

Decentralized sanitary wastewater treatment has become a viable and sustainable alternative, especially for developing countries and small communities. Besides, effluents may present variations in chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total nitrogen values. This study describes the feasibility of using a pilot upflow anaerobic sludge blanket (UASB) reactor to treat wastewater with different organic loads (COD), using black water (BW) and sanitary wastewater, in addition to its potential for preserving nutrients for later recovery and/or reuse. The UASB reactor was operated continuously for 95 weeks, with a hydraulic retention time of 3 days. In Phase 1, the reactor treated simulated BW and achieved 77% COD_total removal. In Phase 2, treating only sanitary wastewater, the COD_total removal efficiency was 60%. Phase 3 treated simulated BW again, and COD_total removal efficiency was somewhat higher than in Phase 1, reaching 81%. In Phase 3, the removal of pathogens was also evaluated: the efficiency was 1.96 log for Escherichia coli and 2.13 log for total coliforms. The UASB reactor was able to withstand large variations in the organic loading rate (0.09-1.49 kg COD m^-3 d^-1), in continuous operation mode, maintaining a stable organic matter removal.

Giardia spp. and Cryptosporidium spp. removal efficiency of a combined fixed-film system treating domestic wastewater receiving hospital effluent

Giardia and Cryptosporidium have caused numerous outbreaks of diarrhea as a result of the ingestion of water contaminated with sewage. In Brazil, the efficiency of Giardia and Cryptosporidium removal by combined fixed-film systems has rarely been studied. The aims of the present study were therefore to verify the removal efficiency of Giardia and Cryptosporidium by a combined system (anaerobic/anoxic filter and aerated submerged biofilter) and to perform the genetic characterization of these parasites. The (oo)cysts were detected by centrifuge concentration and membrane filtration from raw sewage, effluents, adhered biomass, and sludge samples. Immunofluorescence assay and differential interference contrast microscopy were used for the visualization of the (oo)cysts. Nested PCR was applied to confirm Giardia and Cryptosporidium. Giardia and Cryptosporidium were detected in 27% and 5.5% of the 144 analyzed samples of raw sewage and effluents, respectively. A total of 33,000 cysts/L were recovered in the adhered biomass samples (n = 25) from different points of the aerated submerged biofilter, while 6000 oocysts/L were registered in a single point. An average of 11,800 cysts/L were found in the sludge samples (n = 5). The combined system exhibited a removal efficiency of Giardia cysts of 1.8 ± 1.0 log removal. The C and BIV assemblages of Giardia were identified in the raw sewage while AII was found in the treated effluent sample. It was not possible to calculate the removal efficiency of Cryptosporidium oocysts by the combined system. The combined system exhibited some potential as a suitable treatment for the removal of parasites from sewage.

Comparative Pathobiology of the Intestinal Protozoan Parasites Giardia lamblia, Entamoeba histolytica, and Cryptosporidium parvum

Protozoan parasites can infect the human intestinal tract causing serious diseases. In the following article, we focused on the three most prominent intestinal protozoan pathogens, namely, Giardia lamblia, Entamoeba histolytica, and Cryptosporidium parvum. Both C. parvum and G. lamblia colonize the duodenum, jejunum, and ileum and are the most common causative agents of persistent diarrhea (i.e., cryptosporidiosis and giardiasis). Entamoeba histolytica colonizes the colon and, unlike the two former pathogens, may invade the colon wall and disseminate to other organs, mainly the liver, thereby causing life-threatening amebiasis. Here, we present condensed information concerning the pathobiology of these three diseases.

Profiling the diversity of Cryptosporidium species and genotypes in wastewater treatment plants in Australia using next generation sequencing

Wastewater recycling is an increasingly popular option in worldwide to reduce pressure on water supplies due to population growth and climate change. Cryptosporidium spp. are among the most common parasites found in wastewater and understanding the prevalence of human-infectious species is essential for accurate quantitative microbial risk assessment (QMRA) and cost-effective management of wastewater. The present study conducted next generation sequencing (NGS) to determine the prevalence and diversity of Cryptosporidium species in 730 raw influent samples from 25 Australian wastewater treatment plants (WWTPs) across three states: New South Wales (NSW), Queensland (QLD) and Western Australia (WA), between 2014 and 2015. All samples were screened for the presence of Cryptosporidium at the 18S rRNA (18S) locus using quantitative PCR (qPCR), oocyst numbers were determined directly from the qPCR data using DNA standards calibrated by droplet digital PCR, and positives were characterized using NGS of 18S amplicons. Positives were also screened using C. parvum and C. hominis specific qPCRs. The overall Cryptosporidium prevalence was 11.4% (83/730): 14.3% (3/21) in NSW; 10.8% (51/470) in QLD; and 12.1% (29/239) in WA. A total of 17 Cryptosporidium species and six genotypes were detected by NGS. In NSW, C. hominis and Cryptosporidium rat genotype III were the most prevalent species (9.5% each). In QLD, C. galli, C. muris and C. parvum were the three most prevalent species (7.7%, 5.7%, and 4.5%, respectively), while in WA, C. meleagridis was the most prevalent species (6.3%). The oocyst load/Litre ranged from 70 to 18,055 oocysts/L (overall mean of 3426 oocysts/L: 4746 oocysts/L in NSW; 3578 oocysts/L in QLD; and 3292 oocysts/L in WA). NGS-based profiling demonstrated that Cryptosporidium is prevalent in the raw influent across Australia and revealed a large diversity of Cryptosporidium species and genotypes, which indicates the potential contribution of livestock, wildlife and birds to wastewater contamination.

Opportunistic and non-opportunistic intestinal parasites in HIV/ AIDS patients in relation to their clinical and epidemiological status in a specialized medical service in Goiás, Brazil

Patients infected with the Human Immunodeficiency Virus (HIV) often have opportunistic infections, among which strongyloidiasis and coccidiosis are the most common parasitic infections that aggravate their health status. This study examined the prevalence of intestinal parasites, particularly of Strongyloides stercoralis and intestinal coccidia in patients with the Human Immunodeficiency Virus (HIV)/ Acquired Immunodeficiency Syndrome (AIDS) who were treated at the Specialized Assistance Service (SAE) of Jataí, State of Goiás, Brazil, and analyzed its correlation with clinical, laboratory, and socio-epidemiological parameters. A total of 270 stool samples were analyzed by the Lutz technique, Rugai's method, Agar Plate Culture, Ritchie's method and specific staining, Ziehl-Neelsen modified technique, Kinyoun's method and the rapid safranin method. The prevalence of intestinal parasites was 28.88% including 3.8% of S. stercoralis, Cryptosporidium sp. and Cystoisospora belli. There was a significant positive correlation between intestinal parasites and the clinical status and the use of antiretroviral therapy (ART), smoking, CD4+ lymphocyte counts and sexual orientation. In conclusion, the widespread use of antiretroviral therapy and health assistance contributed to the low prevalence of S. stercoralis and coccidiosis in patients with HIV/ AIDS who were followed up at the SAE.