Luciana Urbano dos Santos

Cryptosporidium spp. and Giardia spp. in surface water supply of Campinas, Southeast Brazil

Surface water contaminated by domestic sewage discharges is a potential source of pathogens, including protozoa. During 2005-2006, the source water (Atibaia River) of the Surface Water Treatment Plant (WTP) of Campinas city, São Paulo, Brazil was sampled to obtain an assessment of Cryptosporidium oocyst and Giardia cyst concentrations. Calcium carbonate flocculation (CCF) and membrane filtration (MF) concentration techniques, with and without purification by immunomagnetic separation (IMS) were evaluated. The cysts and oocysts were detected by immunofluorescence assay (IFA) and confirmed by differential interference contrast (DIC). Membrane filtration method generally produced higher recovery efficiency. Giardia spp. was detected in 87.5% of the water samples analyzed with densities ranging from 2.5 to 120 cysts per L. Cryptosporidium spp were detected in 62.5% and the concentrations ranged from 15 to 60 oocysts per L. Cryptosporidium oocyst and Giardia cyst concentrations detected in this study were elevated and are associated with discharge of untreated sewage in Atibaia River. Measures should be taken to protect surface water from sources of contamination.

Occurrence of Giardia cysts and Cryptosporidium oocysts in activated sludge samples in Campinas, SP, Brazil

Giardia and Cryptosporidium have caused several outbreaks of gastroenteritis in humans associated with drinking water. Contaminated sewage effluents are recognized as a potential source of waterborne protozoa. Due to the lack of studies about the occurrence of these parasites in sewage samples in Brazil, we compared the efficiency of two procedures for concentrating cysts and oocysts in activated sludge samples of one sewage treatment plant. For this, the samples were submitted to i) concentration by the ether clarification procedure (ECP) and to ii) purification by sucrose flotation method (SFM) and aliquots of the pellets were examined by immunofluorescence. Giardia cysts were present in all samples (100.0%; n = 8) when using ECP and kit 1 reagents, while kit 2 resulted in six positive samples (85.7%; n = 7). As for SFM, cysts were detected in 75.0% and 100.0% of these samples (for kit 1 and 2, respectively). Regarding Cryptosporidium, two samples (25.0%; kit 1 and 28.5% for kit 2) were detected positive by using ECP, while for SFM, only one sample (examined by kit 1) was positive (12.5%). The results of the control trial revealed Giardia and Cryptosporidium recovery efficiency rates for ECP of 54.5% and 9.6%, while SFM was 10.5% and 3.2%, respectively. Considering the high concentration detected, a previous evaluation of the activated sludge before its application in agriculture is recommended and with some improvement, ECP would be an appropriate simple technique for protozoa detection in sewage samples.

Inactivation of bacteria and helminth in wastewater treatment plant effluent using oxidation processes.

The contamination of bodies of water by raw and even treated sewage is worrying because pathogens that affect public health and the environment are not fully eliminated in wastewater treatment systems. The disinfection step is an important barrier to adopt to reduce this contamination. However, widely used disinfectants such as chlorine do not guarantee the inactivation of resistant organisms such as spore-forming bacteria and helminth eggs. This study evaluated the effectiveness of processes of peroxidation (H2O2), ultraviolet radiation (UV) and peroxidation assisted by ultraviolet radiation (H2O2/UV) in terms of reduction and inactivation of total coliform bacteria, Escherichia coli, helminth eggs and larvae present in a treated sewage. Doses of UV radiation of 70 mJ cm(-2) and hydrogen peroxide concentration of 30 mg L(-1) were used. The number of bacteria reduced after UV and H2O2/UV processes was 3 and 4 log, respectively. An average reduction of 59% in the number of eggs was verified when using H2O2, UV, and H2O2/UV processes. Helminth larvae were reduced by 24% after H2O2 and UV; the process H2O2/UV did not reduce the number of larvae. Statistically significant differences between the processes for both organisms were not observed.

Detecção de oocistos de Cryptosporidium spp. e cistos de Giardia spp. em amostras de esgoto bruto ou tratado: avaliação crítica dos métodos

In this study, the efficiency of centrifuge-concentration and membrane filtrated methods was evaluated in the detection of Cryptosporidium spp. oocysts and Giardia spp. cysts in raw or treated wastewater samples, from activated sludge systems (ETE - Samambaia, Campinas, in Sao Paulo). The samples were collected once a fortnight for two years: 53 samples of influent (AFL), 53 samples of treated effluent without ultraviolet disinfection (EFL), and 38 samples of treated effluent with ultraviolet disinfection (EFL+UV). Giardia spp. cysts were found in 90.5% of the AFL samples; in 96.2% of the samples, EFL; and in 94.7%, EFL+UV. Cryptosporidium spp. oocysts were detected in 6.4% of AFL samples and 2.6% of EFL+UV. Both methods showed efficiency when detecting protozoa in all types of samples, besides having low costs by analysis.

Urban water reuse: microbial pathogens control by direct filtration and ultraviolet disinfection

Physicochemical treatment efficiency for unrestricted urban water reuse was evaluated at a conventional activated-sludge wastewater treatment plant (WWTP). Pilot plant set-up consisted of an alum coagulation step, granular media upflow flocculation and direct downflow dual-media filtration followed by ultraviolet disinfection (dose of 95 mJ cm⁻²). Optimum aluminum sulfate dosage of 10 mg L⁻¹ and coagulation pH 7.0 were preset based on bench scale tests. Under WWTP stable operation, water quality met United States Environmental Protection Agency (USEPA) suggested guidelines for unrestricted urban reuse regarding turbidity (mean value 1.3 NTU) and suspended solids (mean value 2.1 mg L⁻¹). When WWTP overall plant performance dropped from 90 to 80% (although BOD value stayed below 6 mg O₂ L⁻¹, suggesting unrestricted reuse), solids breakthrough in filtrate was observed. Microorganism removal rates were: total coliforms 60.0%, Escherichia coli 63.0%, Giardia spp. 81.0%, and helminth eggs 62.5%; thus organisms still remained in filtrate. Ultraviolet (UV) disinfection efficiency was 4.1- and 3.8-log for total coliforms and E. coli, respectively. Considering low UV efficiency obtained for helminths and the survival of protozoa and helminths in the environment, effluent quality presents risk to public health if destined for unrestricted urban reuse.

Giardia duodenalis: Number and Fluorescence Reduction Caused by the Advanced Oxidation Process (H2O2/UV)

This study evaluated the effect of peroxidation assisted by ultraviolet radiation (H2O2/UV), which is an advanced oxidation process (AOP), on Giardia duodenalis cysts. The cysts were inoculated in synthetic and surface water using a concentration of 12 g H2O2 L−1 and a UV dose (λ = 254 nm) of 5,480 mJcm−2. The aqueous solutions were concentrated using membrane filtration, and the organisms were observed using a direct immunofluorescence assay (IFA). The AOP was effective in reducing the number of G. duodenalis cysts in synthetic and surface water and was most effective in reducing the fluorescence of the cyst walls that were present in the surface water. The AOP showed a higher deleterious potential for G. duodenalis cysts than either peroxidation (H2O2) or photolysis (UV) processes alone.

Infectivity of Giardia duodenalis Cysts from UV Light-Disinfected Wastewater Effluent Using a Nude BALB/c Mouse Model

Giardia duodenalis is a protozoan of public health interest that causes gastroenteritis in humans and other animals. In the city of Campinas in southeast Brazil, giardiasis is endemic, and this pathogen is detected at high concentrations in wastewater effluents, which are potential reservoirs for transmission. The Samambaia wastewater treatment plant (WWTP) in the city of Campinas employs an activated sludge system for sewage treatment and ultraviolet (UV) light for disinfection of effluents. To evaluate this disinfection process with respect to inactivating G. duodenalis cysts, two sample types were investigated: (i) effluent without UV disinfection (EFL) and (ii) effluent with UV disinfection (EFL+UV). Nude immunodeficient BALB/c mice were intragastrically inoculated with a mean dose of 14 cysts of G. duodenalis recovered from effluent from this WWTP, EFL, or EFL+UV. All animals inoculated with G. duodenalis cysts developed the infection, but animals inoculated with UV-exposed cysts released a lower average concentration of cysts in their faeces than animals inoculated with cysts that were not UV disinfected. Trophozoites were also observed in both groups of animals. These findings suggest that G. duodenalis cysts exposed to UV light were damaged but were still able to cause infection.

Inactivation of Clostridium perfringens, Total Coliforms, and Escherichia coli by UV/H2O2 in Wastewater Treatment Plant Effluent

Abstract This study evaluated the effectiveness of H2O2, UV radiation, and H2O2/UV processes to inactivate total coliforms, Escherichia coli, and Clostridium perfringens bacteria present in a treated sewage. The samples were collected at Samambaia Waste Water Treatment Plant in Campinas, Brazil. The photochemical assays were carried out using 125-3,640 mJ cm−2 doses of UV radiation. The initial H2O2 concentration was 30 mg L−1. The bacteria were quantified in samples of 100% raw effluent, which had an average of 1.1 × 106 most probable number (MPN)/100 mL of total coliforms, 2.3 × 105 MPN/100 mL of E. coli, and 1.4 × 104 MPN/100 mL of C. perfringens after treatment with activated sludge. Peroxidation did not efficiently inactivate the measured bacteria. The UV process incurred 5-log inactivation for total coliforms and E. coli bacteria, whereas advanced oxidation processes (AOPs) inactivated both bacteria. UV radiation and AOP incurred a 2-log inactivation of C. perfringens.

Inativação de cistos de Giardia duodenalis por peroxidação e peroxidação assistida por radiação ultravioleta

ABSTRACT Performance of an advanced oxidative process (AOP) with the application of hydrogen peroxide and UV radiation (H 2 O 2 /UV) has proven effective to inactivate Giardia duodenalis cysts. Hydrogen peroxide concentrations of 15 mg.L -1 and 6x10 3 mg.L -1 and 44 UV doses of 2,736 and 5,472 mW s.cm were used in this study. The process effectiveness was assessed observing the occurrence of damage to the cyst’s wall using direct immunofluorescence reaction (IFA) and scanning electron microscopy (SEM). When using the lower UV radiation dose and the lower oxidant concentration the AOP has shown higher effectiveness both in causing damage to the Giardia duodenalis wall and in reducing the number of cysts inoculated at the beginning. The average reduction AOP and peroxidation processes reduced 45.2 and 22.6% in the number of G. duodenalis cysts and 42 and 29.4% of the remaining cysts presented damage, respectively.Keywords: advanced oxidation process; Giardia duodenalis; scanning eletronic microscopy.