Avaliação de ultrafiltração como alternativa à flotação por ar dissolvido no pós-tratamento do efluente de lodos ativados — estudo em escala piloto na estação de tratamento de esgoto Brasília norte / Evaluation of ultrafiltration as an alternative to dissolved air flotation for the post-treatment of activated sludge effluent — pilot study in the Brasília norte wastewater treatment plant

RESUMO A melhoria da qualidade dos efluentes das estações de tratamento de esgotos Brasília Norte e Sul tornou-se premente após o corpo receptor dos seus efluentes, o lago Paranoá, passar a ser utilizado como manancial de abastecimento. Este trabalho apresenta estudo comparativo entre o tratamento terciário por ultrafiltração precedido por coagulação em escala piloto e a flotação por ar dissolvido existente na estação de tratamento de esgotos Brasília Norte. A instalação piloto de ultrafiltração e a flotação por ar dissolvido foram alimentadas pela mesma matriz, o efluente da etapa de lodos ativados das estações de tratamento de esgotos Brasília Norte, após coagulação. Foram avaliadas sete condições operacionais da instalação piloto de ultrafiltração variando-se a vazão, o tempo de operação entre limpezas e a duração da limpeza física. O comportamento operacional e a qualidade do efluente produzido foram monitorados. O aumento do fluxo do permeado (de 40,2 para 50,6 e 61,0 L.m−2.h−1) e do tempo de operação entre as limpezas (de 25 para 38 e 50 min), bem como a redução da duração da retrolavagem (de 80 para 60 e 30 s) resultaram em evolução mais intensa da pressão transmembrana. A ultrafiltração foi mais eficiente do que a flotação por ar dissolvido na remoção de turbidez, sólidos suspensos totais, demanda química de oxigênio e fósforo total, com ganho médio de remoção de 9,4, 13,0, 8,5 e 12,8%, respectivamente. Destaca-se a remoção de coliformes na ultrafiltração, 3,4 log superior à da flotação por ar dissolvido. A utilização da ultrafiltração como alternativa à flotação por ar dissolvido apresenta a vantagem de produzir efluente de melhor qualidade, particularmente no aspecto microbiológico, com menor flutuação da qualidade, porém o tratamento e a destinação do lodo produzido pela ultrafiltração devem ser equacionados.

ABSTRACT Improvement in the effluent quality of the Brasília Norte and Brasília Sul wastewater treatment plants became necessary after their effluent receiving body, Paranoá Lake, started being used as source of drinking water for the population of Brasília (Federal District, Brazil). This is a comparative study between the tertiary treatment with ultrafiltration membrane (pilot scale) and the existing dissolved air flotation of Brasília Norte wastewater treatment plant. Both ultrafiltration pilot plant and dissolved air flotation were fed with the same matrix, the effluent of the activated sludge stage of Brasília Norte wastewater treatment plants, after coagulation. Seven operational conditions were evaluated at ultrafiltration pilot plant, with variations in flow rate, time of operation between cleaning processes, and the duration of backwashing. The operational behavior and the quality of the produced effluent were monitored. The increase in permeate flux (from 40.2 to 50.6 and 61.0 L.m−2.h−1) and in the time of operation between cleaning processes (from 25 to 38 and 50 min), as well as the reduction of backwashing duration (from 80 to 60 and 30s), resulted in a more intense evolution of transmembrane pressure. Ultrafiltration was more efficient than dissolved air flotation in the removal of turbidity, total suspended solids, chemical oxygen demand, and total phosphorous, with average gain in removal of 9.4, 13.0, 8.5, and 12.8%, respectively. It is worth mentioning the removal of coliforms by ultrafiltration, which was, on average, 3.4 log higher than that by dissolved air flotation. The use of ultrafiltration as an alternative to dissolved air flotation has the advantage of producing better quality effluent, particularly regarding microbiological aspects, providing lower quality fluctuation; however, treatment and destination of the ultrafiltration waste must be considered.

Eficiência de duas técnicas de recuperação de espermatozoides epididimários de cães e avaliação seminal pós-criopreservação / [Efficiency of two techniques for recovering epididymal spermatozoids from dogs and seminal evaluation post cryopreservation]

O objetivo deste trabalho foi avaliar a recuperação de espermatozoides epididimários de cães castrados, utilizando as técnicas de fluxo retrógrado (FR) e flutuação (FL) em diluidor Tris-gema, antes e após a criopreservação. Foram coletados 30 complexos testículo-epididímos (CTE), sendo 15 para FR e 15 para FL, e, logo após a recuperação dos espermatozoides, foram analisadas as alterações morfológicas nessas células espermáticas. Após a adição do diluidor, foram avaliados os parâmetros de motilidade total (MOT) e vigor (V) espermáticos. O sêmen pós-criopreservado foi submetido ao teste de termorresistência nos tempos T0, T30, T60 e T90 minutos, além da avaliação das membranas plasmática e acrossomal por sondas fluorescentes. Não houve diferença estatística entre as técnicas quanto à MOT e ao vigor no sêmen diluído (FR-MOT: 82,3% e V: 3,4; FL-MOT: 79,6% e V: 3,2) e pós-criopreservado (FR-MOT: 34% e V: 2,8; FL-MOT: 30% e V: 2,7). A partir do T30, houve diferença significativa quanto à MOT e ao vigor nas técnicas utilizadas, e o tempo também prejudicou o acrossoma espermático a partir do T30. Conclui-se que as técnicas de recuperação de espermatozoides epididimários de cães castrados, testadas neste trabalho, podem ser utilizadas para refrigeração e criopreservação de sêmen.(AU)

The objective of this work was to evaluate the recovery of epididymal spermatozoa from castrated dogs using retrograde flow (FL) and flotation (FL) techniques in Tris-egg yolk diluent, before and after cryopreservation. Thirty testicle-epididymal complexes (CTE) were collected, 15 for FR and 15 for FL and soon after spermatozoid recovery, morphological changes in these spermatic cells were analyzed. After addition of the diluent, the parameters of total motility (MOT) and vigor (V) were evaluated. The post-cryopreserved semen was submitted to thermoresistance (TTR) test at T0, T30, T60 and T90 minutes, as well as the plasma and acrosomal membrane evaluation by fluorescent probes. There was no statistically significant difference between techniques tested for MOT and vigor in the diluted semen (FR-MOT: 82.3% and V: 3.4, FL-MOT: 79.6% and V: 3.2) and post-cryopreserved (FR-MOT: 34% and V: 2.8, FL-MOT: 30% and V: 2.7). From the T30 there was a significant difference regarding MOT and vigor in the used techniques, and the time also damaged the spermatic acrosome from the T30. It is concluded that the epididymal spermatozoa recovering techniques from castrated dogs, tested in this study, can be used for semen refrigeration and cryopreservation.(AU)

Estudo da coagulação/floculação de água com turbidez moderada na sedimentação e flotação por ar dissolvido / Study of coagulation/flocculation of water with moderate turbidity in sedimentation and floating by dissolved air

RESUMO Os processos de formação, crescimento, ruptura e rearranjo dos flocos que ocorrem durante a coagulação/floculação influenciam, significativamente, a eficiência da remoção dos agregados no tratamento de água. Por isso, é importante estudar as propriedades dos flocos, que são alteradas continuamente durante a floculação e podem interferir na subsequente remoção das partículas. Neste trabalho foi avaliada a eficiência de remoção de turbidez por meio da sedimentação e da flotação por ar dissolvido (FAD), com o uso de aluminato de sódio como agente coagulante. Adicionalmente, a etapa de floculação foi monitorada usando imagens obtidas por método não intrusivo. A FAD proporcionou melhor resultado de remoção de turbidez, de 93%, mostrando robustez como etapa no processo de tratamento de água. Na etapa de floculação, o tamanho dos flocos variou de 0,03 a 0,53 mm, com maior concentração de partículas nas menores classes de tamanho monitoradas. O estudo da dimensão fractal mostrou que o aumento da intensidade da mistura acentuou a ruptura (Dmédio de 0,2 mm para 20 s-1 para Dmédio de 0,1 mm para 40 s-1) nos flocos, promovendo o surgimento de flocos menos compactos. A FAD se mostrou menos sensível às variações de tamanho dos agregados quando comparada à sedimentação.

ABSTRACT The processes of formation, growth, rupture, and rearrangement of flocs, which occur during coagulation/flocculation, significantly influence the removal efficiency of the aggregates in water treatment. Therefore, it is important to study the flocs properties because they change continuously during the process and may interfere in the choice of later step for removal of the particles. This article evaluated the efficiency of turbidity removal in sedimentation and dissolved air flotation (DAF) with the use of sodium aluminate as a coagulant. In addition, the flocculation step was monitored through digital images, by non-intrusive method, to study the morphological properties of flocs. The DAF step provided better removal results (greater than 93%) in less process time, showing to be an advantageous step in turbid water treatment. In the flocculation step, the size of the flocs varied from 0.03 to 0.53 mm, with a higher particle concentration in the smaller size classes. The study of the fractal dimension showed that the increase in the intensity of the mixture accentuated the rupture (Dmean of 0.2 mm for 20s for Dmean of 0.1 mm for 40s-1) in the flocs, promoting the appearance of less compact flocs. DAF was less sensitive to variations in aggregate size when compared to sedimentation.

Composted slaughterhouse sludge as a substitute for chemical fertilizers in the cultures of lettuce (Lactuca sativa L.) and radish (Raphanus sativus L.)

Abstract Flotation sludge (FS) is produced in huge amounts at slaughterhouses in western Santa Catarina, Brazil. This waste is rich in plant nutrients and a valuable resource for soil amendments. Five FS composts were tested as a replacement for chemical fertilizers (QF), namely T1 (75% poultry manure (PM) and 25% sawdust (SD)); T2 (50% PM and 50% SD); T3 (25% PM and 75% SD); T4 (100% PM and 0% SD); and T5 (0% PM x 100% SD). For lettuce plants, treatments containing composted FS resulted in an increased number of leaves, leaf area and leaf fresh weight (LFW). T1 presented the best results with increases of 1.4 fold in LFW compared to plants supplemented with QF. T2 was the most effective treatment for radish with the best results of root fresh weight and root diameter. Although T4 had the highest nitrogen content, it did not present the best results in growth performance for lettuce or radish. The presence of higher proportions of SD in composts (25% for lettuce and 50% for radish) improved the physical characteristics of the soil and proved to be a more balanced compost.

Reliability of different methods of diagnosing intestinal parasites in horses

Parasitism by intestinal nematodes may cause serious injuries to equines affecting their performance, given that the parasites compete for food and cause irritation, internal bleeding and anaemia. The diagnostic methods currently available are not efficient in detecting all the species of parasites simultaneously, hampering reliable diagnosis. Therefore, the purpose of this study was to evaluate four diagnostic methods for detecting equine intestinal parasites in the southern hinterland of Pernambuco, Brazil. Fecal samples (n = 87) were collected and examined through flotation based methods (Willis-Mollay, modified centrifugal flotation and EPG/OPG) and sedimentation (Hoffman). Of the total number of samples examined, 77.0% (67/87) were positive by modified centrifugal flotation; 44.8% (39/87) were positive by the Willis-Mollay method; 34.5% (30/87) by the Hoffman method and 28.7% (25/87) by the EPG/ OPG method. The Kappa index indicated moderate concordance between the Willis-Mollay and modified centrifugal flotation techniques (K= 0.477); Willis-Mollay and EPG/OPG (K= 0.466); EPG/OPG and Hoffman (K= 0.425). In conclusion, modified centrifugal flotation presented high sensitivity for detection of parasites of the Strongylida order and Parascaris spp. It may, therefore, be used in association with the Willis-Mollay technique as a safe and accurate method of diagnosis.

One case report of Ancylostoma duodenale parasitized in hepatic flexure of colon / 中国血吸虫病防治杂志

This paper reports a case of Ancylostoma duodenale parasitized in the hepatic flexure of colon and the case was misdiagnosed at the beginning. The causes of misdiagnosis are analyzed and the laboratory examination methods of hookworm are summarized.

Concordance between the zinc sulphate flotation and centrifugal sedimentation methods for the diagnosis of intestinal parasites / Concordancia entre los métodos de flotación con sulfato de zinc y sedimentación centrífuga para el diagnóstico de parásitos intestinales

Resumen Introduction: The diagnosis of intestinal parasitic infections depends on the parasite load, the specific gravity density of the parasite eggs, oocysts or cysts, and the density and viscosity of flotation or sedimentation medium where faeces are processed. Objective: To evaluate the concordance between zinc sulphate flotation and centrifugal sedimentation in the recovery of parasites in faecal samples of children. Materials and methods: Faecal samples of 330 children from day care centers were evaluated by zinc sulphate flotation and centrifugal sedimentation techniques. The frequencies of detection of parasites by each method were determined and the agreement between the diagnostic techniques was evaluated using the kappa index, with 95% confidence intervals. Results: The faecal flotation in zinc sulphate diagnosed significantly more cases of Trichuris trichiura infection when compared to centrifugal sedimentation (39/330; 11.8% vs. 13/330; 3.9%, p<0.001), with low diagnostic concordance between methods (kappa=0.264; 95% CI: 0.102-0.427). Moreover, all positive samples for Enterobius vermicularis eggs (n=5) and Strongyloides stercoralis larvae (n=3) were diagnosed only by zinc sulphate. No statistical differences were observed between methods for protozoa identification. Conclusions: The results showed that centrifugal flotation in zinc sulphate solution was significantly more likely to detect light helminths eggs such as those of T. trichiura and E. vermicularis in faeces than the centrifugal sedimentation process.

Abstract Introducción. El diagnóstico de infecciones parasitarias intestinales depende de la carga de parásitos, la densidad de la gravedad específica de los huevos, ooquistes o quistes de parásitos, y de la densidad y viscosidad de los reactivos de flotación o sedimentación usados para procesar las heces. Objetivo. Evaluar la concordancia entre el método de flotación de sulfato de zinc y la sedimentación por centrifugación en la recuperación de parásitos en muestras fecales de niños. Materiales y métodos. Se evaluaron las muestras fecales de 330 niños de guarderías mediante las técnicas de flotación con sulfato de zinc y de sedimentación por centrifugación. Se determinó la frecuencia de detección de parásitos con cada método y se evaluó la concordancia entre las técnicas de diagnóstico mediante el índice kappa, con intervalos de confianza del 95 %. Resultados. Mediante la flotación fecal con sulfato de zinc, se diagnosticó un número significativamente mayor de casos de infección por Trichuris trichiura que con la sedimentación por centrifugación (39/330; 11,8 % Vs. 13/330; 3,9 %) (p<0,001), con poco acuerdo entre los métodos (kappa=0,264; IC95% 0,102-0,427). Además, todas las muestras positivas para huevos de Enterobius vermicularis (n=5) y larvas de Strongyloides stercoralis (n=3) se diagnosticaron solamente por sulfato de zinc. No se observaron diferencias estadísticamente significativas entre los métodos para la identificación de protozoos. Conclusiones. La flotación centrífuga en una solución de sulfato de zinc presentó una probabilidad significativamente mayor de detectar los huevos livianos de helmintos como T. trichiura y E. vermicularis en heces, que el proceso de sedimentación por centrifugación.

Influência do tamanho de flocos e da concentração de ar dissolvido na eficiência da flotação / Influence of flocs size and dissolved air concentration on the efficiency of flotation

RESUMOO presente artigo apresenta resultados de pesquisa que teve por objetivo a investigação da influência do tamanho de partículas floculadas na eficiência da clarificação de águas para abastecimento por flotação por ar dissolvido (FAD) com o emprego de método e equipamento para a aquisição e análise de imagens especialmente desenvolvidos para a caracterização da distribuição de tamanho de flocos e microbolhas de ar presentes no processo de flotação. Os ensaios foram realizados com água sintética (temperatura de 26,0±0,5oC; turbidez de 7,5±0,2 NTU; cor aparente de 38±1 uC; alcalinidade de 29,8±0,6 mgCaCO3.L-1; condutividade de 59,3±0,8 µS.cm-1; UV254nm de 0,128±0,004cm-1), a qual foi coagulada com a aplicação de 1,9 mg.L-1 de Al3+ (pH de 6,6±0,05; 22,5 mg.L-1alum). Os resultados alcançados demonstraram que: i) a distribuição de tamanho de partículas floculadas influenciou diretamente a clarificação por flotação da água em estudo, sendo que as melhores condições de floculação foram aquelas que conduziram à formação, em sua maioria, de partículas floculadas com diâmetro médio de Feret acima de 300 µm; ii) os menores valores residuais dos parâmetros analisados na água em estudo foram alcançados com o emprego da Condição 2 de floculação (T=17 min/G=60 s-1) associada a uma concentração em massa de ar (Cb) de 4,8 mg.L-1, entretanto, a FAD foi capaz de operar também com boa eficiência com a utilização de tempo de floculação (T) de 10 minutos; iii) o método e o equipamento desenvolvidos nesta pesquisa para aquisição e análise de imagens demonstraram constituir importantes ferramentas para a obtenção das distribuições de tamanho de flocos e microbolhas de ar.

ABSTRACTThis paper shows the results of a research that aimed to investigate the influence of flocculated particles size on the dissolved air flotation (DAF) efficiency. Special image acquisition method and equipment were developed to characterize the flocculated particles and air microbubbles size distribution in the contact zone outlet of the DAF unit. The trials were carried out with synthetic water (temperature of 26.0±0.5oC; turbidity of 7.5±0.2 NTU; apparent color of 38±1 uC; alkalinity of 29.8±0.6 mgCaCO3.L-1; conductivity of 59.3±0.8 µS.cm-1; UV254nm of 0.128±0.004 cm-1), that it was coagulated by applying 1.9 mg.L-1 of Al3+ (pH 6.6±0.05; 22.5 mg.L-1alum). The results showed that: i) the flocculation conditions interfered directly on the efficiency of DAF process, and the best flocculation conditions were those that conducted to formation of flocculated particles size with Feret mean diameter above 300 µm; ii) the best results were obtained applying Condition 2 of flocculation (T=17 min/G=60 s-1) combined to air mass concentration of 4.8 mg.­L-1, however, DAF was also capable of operating with a satisfactory efficiency when applying flocculation time of 10 minutes; iii) the special image acquisition method and equipment developed proved to be an important tool to characterize the flocculated particles and air microbubbles size distribution.

Separation and enrichment of geniposidic acid from leaves of Eucommia ulmoides by aqueous two-phase flotation / 中草药

Objective: Ethanol/NaH2PO4 aqueous two-phase gas solvent sublation coupled with response surface methodology was developed for the separation/enrichment and analysis of geniposidic acid from the leaves of Eucommia ulmoides. Methods: For the aqueous two-phase flotation project, the flotation effects of different solvent, salts, flotation rate, flotation time, amount of crude extract and so on were deeply investigated; Furthermore, a Box-Behnken central composite test design was studied to determine the best flotation process conditions of GPA, and three factors including the mass fraction of NaH2PO4, the mass fraction of ethanol, and the flotation rate were selected based on the single factor test in the design. A 100 times scale-up experiment also was tested. Results: The optimal conditions of the flotation were as follows: the mass fraction of NaH2PO4 was 25%, the mass fraction of ethanol was 20%, the amount of crude extract was 5 g, the flotation rate was 30 mL/min, and the flotation time was 20 min. Under the optimal condition, the flotation efficiency was 97.88%, and the enrichment factor was 27.34; The 100 times scale-up results showed that the flotation efficiency of GPA was 95.60%, and the RSD value was 0.77%. Conclusion: The method with ethanol/NaH2PO4 aqueous two-phase gas solvent sublation is suitable for the separation and enrichment of the active ingredients from E. ulmoides because of its high distribution coefficient and large enrichment factor.

Emprego de bomba multifásica como unidade geradora de microbolhas de ar em sistema de flotação aplicado ao pré-tratamento de efluente têxtil / Multiphase pump as microbubble generator for flotation system applied to pre-treatment of textile wastewater

O artigo apresenta os resultados de uma pesquisa desenvolvida com o objetivo de avaliar o desempenho de bomba multifásica (mistura de ar e água) aplicada em substituição à câmara de saturação, em sistema de flotação localizado em uma indústria têxtil. Na unidade piloto (taxa de aplicação superficial de clarificação igual a 128,6 ± 10 m.d-1), foi verificado que os melhores resultados em termos de eficiência de remoção de turbidez e cor aparente (eficiência de remoção superior a 95 por cento) foram obtidos nos ensaios realizados com razão de recirculação em torno de 30 por cento associada à composição volumétrica de ar de 13 por cento.

This paper presents the results of a research carried out that aims to evaluate the performance of a multiphase pump (mixture of air and water) applied to replace the saturator chamber in a flotation system located in a textile industry. In the pilot unit (hydraulic surface loading equal to 128.6 ± 10 m.d-1), it was verified that the best results in terms of removal efficiency of turbidity and apparent color (efficiency removal over 95 percent) were obtained for the essays performed with recirculation ratio equal to 30 percent and air supply of 13 percent.

Estudio comparativo de recuperación de formas parasitarias por tres diferentes métodos de enriquecimiento coproparasitológico / Comparative study of parasitic forms recuperation using three different coproparasitoscopic methods

Se analizaron 165 muestras fecales seriadas, utilizando dos métodos de sedimentación: Ritchie (R) y Carles Barthelemy (CB) y uno de flotación: Willis (W), con el fin de optimizar el diagnóstico de los parásitos intestinales y determinar la eficacia de las técnicas. Se hallaron parásitos en 119 (72,1 por ciento) de los analizados. Hubo diferencias significativas en la recuperación de protozoos (p < 0,001), observándose 81,4 por ciento (R), 77,4 por ciento (CB), y 57,8 por ciento (W). Blastocystis hominis, G.lamblia, Ascaris lumbricoides y Trichuris trichiura se recuperaron con mayor frecuencia mediante sedimentación, resultando más efectivo el método de Ritchie (p < 0,05).

A total of 165 fecal samples were analyzed, using two sedimentation methods: Ritchie (R), Carles Barthelemy (CB), and one of flotation: Willis (W), in order to optimize intestinal parasites diagnosis and to determine the techniques effectiveness. Parasites were found in 119 (72,12%) of those analyzed. Significant differences were in protozoa recovery (p < 0,001), being observed 81.4% (R), 77.4% (CB), and 57.8% (W). Blastocystis hominis, Giardia lamblia, Ascaris lumbricoides and Trichuris trichiura were recovered more frequency by means of sedimentation, being Ritchie´s method the most effective one (p < 0.05).

Attention Promotion Effect of Flotation Therapy / 中国心理卫生杂志

Objective: To evaluate the effect of flotation therapy on the attention of undergraduates. Method: Subjects were 53 undergraduates (26 male, 27 female). They were randomly divided into 5 groups. Group 1,2,3 and group 4 were flotation groups and group 5 was control group. Each subject finished four therapies. Visual attention attribution and diversion (T5) and bilateral two- choice reaction time (T8) were used as the indexes. Result: As a whole, the T5 and T8 times of the subjects in the flotation groups were shortened in the course of the therapy. The promotion of attention in the male subjects was better than that in the female subjects. There was no significant difference between the changes of bilateral two-choice reaction time. The promotion in the flotation subjects was significantly better than that in the control subjects and it could not be explained totally by practice effect. Conclusion: The attention of the subjects can be promoted by flotation therapy. This study could not support the assumption that flotation therapy could promote the function of right brain as some prior studies declared.

Separation of Indigo Naturalis by foam flotation technique in a continuous mode / 中草药

Objective To study the process of foam flotation in separation of Indigo Naturalis in a continuous mode and to optimize the operational conditions.Methods Taking content and rate of recovery rate of indigo as index to investigate the single factors,such as the height of collecting region,the height of froth layer,flushing water rate,delivery rate,air flow rate,and aerating velocity,to study the effect of continuous foam floatation on Indigo Naturalis,and to optimize the process conditions finally.Results The flotation performance is good when the height of collecting region is 1.5 m,the height of froth layer is 30 cm,the delivery rate is 0.1 cm/s,the flushing water rate is 0.01 cm/s,the aerating velocity is 1.5 cm/s.The recovery rate of indigo is more than 75% and indgo content is over 5.0%.Conclusion Foam flotation technique is stable and can be used to the separation of Indigo Naturalis in a continuous mode.And this study is the foundation of semi-works production of Indigo Naturalis.

Study on Methods for Isolation and Purification of Cryptosporidium parvum Oocysts from Mouse Feces / 中国寄生虫学与寄生虫病杂志

Objective To explore an applicable method for isolation and purification of Cryptosporidium parvum oocysts with high purity, recovery and vigor from mouse feces. Methods Four techniques were used for isolating and purifying C.parvum oocysts from mouse feces: modified saturated saline flotation, percoll gradient centrifugation, CsCl gradient centrifugation and the classical discontinuous sucrose gradient centrifugation. Oocysts received from the methods were used respectively to infect in vitro bovine fallopian tube epithelial cells (BFTE) and the development of the oocysts was examined under microscope after 48 h and 72 h cultivation. Results The number of oocysts received by the classical discontinuous sucrose gradient centrifugation [(2.86?0.08)?107] was significantly higher than that of percoll gradient centrifugation [(1.52?0.08)?107] (P0.05). Oocysts received from CsCl gradient centrifugation showed higher purity than those by discontinuous sucrose gradient centrifugation. Conclusion In comparison to the classical discontinuous sucrose gradient centrifugation, operation of the modified saturated saline flotation is easier and faster, and the purity of oocysts isolated by CsCl gradient centrifugation is higher.