Phytoremediation of Landfill Leachate with Colocasia esculenta, Gynerum sagittatum and Heliconia psittacorum in Constructed Wetlands.

This study assessed the accumulation of Cd (II), Hg (II), Cr (VI) and Pb (II) in Gynerium sagittatum (Gs), Colocasia esculenta (Ce) and Heliconia psittacorum (He) planted in constructed wetlands treating synthetic landfill leachate. Sixteen bioreactors were operated in two experimental blocks. Metal concentrations in the influent and effluent; root, stem, branch and leaves of plants were analysed, as well as COD, N-NH4+, TKN, T, pH, ORP, DO, and EC. Average removal efficiencies of COD, TKN and NH4+-N were 66, 67 and 72%, respectively and heavy metal removal ranged from 92 to 98% in all units. Cr (VI) was not detected in any effluent sample. The bioconcentration factors (BCF) were 10(0) -10(2). The BCF of Cr (VI) was the lowest: 0.59 and 2.5 (L kg(-1)) for Gs and He respectively; whilst Cd (II) had the highest (130-135 L kg(-1)) for Gs. Roots showed a higher metal content than shoots. Translocation factors (TF) were lower, He was the plant exhibiting TFs>1 for Pb (II), Cr (T) and Hg (II) and 0.4-0.9 for Cd (II) and Cr (VI). The evaluated plants demonstrate their suitability for phytoremediation of landfill leachate and all of them can be categorized as metals accumulators.

First record of Anastrepha flavipennis Greene (Diptera: Tephritidae) and of its host in the Brazilian Amazon.

Anastrepha flavipennis Greene was obtained from Pouteria glomerata (Sapotaceae) fruits, known as "abiurana-da-várzea" in the Brazilian Amazon. This is the first record of A. flavipennis for the state of Amazonas and of P. glomerata as a host for this fruit fly in the Amazon Basin.

Inibição do desenvolvimento de aleurocanthus woglumi ashby (hemiptera: aleyrodidae) por aschersonia cf. aleyrodis webber (deuteromycotina: hyphomycetes)

ABSTRACT The host insects of the fungus Aschersonia sp. are restricted to the Aleyrodidae and Coccidae families of the Hemiptera order. The present study was aimed at evaluating, through bioessays with different concentrations of the fungi, the effect of this fungus, in-vitro, on different developmental stages of Aleurocanthus woglumi, thus testing it as a potential biological control agent. Aschersonia cf. aleyrodis proved more efficient in the control of A. woglumi at higher concentrations, from 2.3 x 107 conidia/mL, turning out to be a good biological control agent of this pest. Although it presented slow growth in the culture medium tested, Aschersonia cf. aleyrodis proved to be efficient in the control of citrus blackfly. The highest mortalities occurred in the youngest stages of A. woglumi as an egg, and at the second and first nymph stages, there being no statistical difference between them. The lowest mortality occurred at the fourth nymph stage. The mortalities at the egg stage, and at the first, second and third nymph stages (but not the fourth), began on the fourth day after A. cf. aleyrodis inoculation, with peaks of mortality on the tenth day.

RESUMO Os insetos hospedeiros do fungo Aschersonia sp. estão restritos às famílias Aleyrodidae e Coccidae, da ordem Hemiptera. Objetivou-se avaliar o efeito, in vitro, desse fungo, nos diferentes estádios de desenvolvimento da mosca-negra-dos-citros, A. woglumi, como potencial agente de controle biológico, através de bioensaios com diferentes concentrações de inóculo do fungo. A melhor eficiência de controle foi constatada em concentrações mais elevadas, a partir de 2,3 x 107 conídios/mL, revelando-se como um bom agente de controle biológico dessa praga. Embora tenha apresentado crescimento lento no meio de cultura testado, Aschersonia cf. aleyrodis mostrou-se eficiente no controle da mosca-negra-dos-citros. As maiores mortalidades ocorreram nas fases mais jovens de A. woglumi como ovo, ninfa 2 e ninfa 1, não havendo diferença estatística entre elas. No estádio de ninfa 4, ocorreu a menor mortalidade. As mortalidades nas fases de ovo, ninfas 1, 2 e 3, com exceção da ninfa 4, se iniciaram no quarto dia após a inoculação de A. cf. aleyrodis, com acmes de mortalidade no 10º dia.

Dispersion and treatment performance analysis of an UASB reactor under different hydraulic loading rates.

Mixing and transport phenomena affect the efficiency of all bioreactor configurations. An even mixing pattern at the macro-level is desirable to provide good conditions for substrate transport to, and from, the microbial aggregates. The state of segregation of particulate material in the reactor is also important. The production of biogas in anaerobic reactors is another factor that affects mixing intensity and hence the interactions between the liquid, solid and gaseous phases. The CSTR model with some degree of short-circuiting, dead zones and bypassing flows seems to describe the overall hydrodynamics of UASBs. However, few data are available in the literature for full-scale reactors that relate process performance to mixing characteristics. Dispersion studies using LiCl were done for four hydraulic loading rates on a full-scale UASB treating domestic wastewater in Ginebra, Valle del Cauca, southwest Colombia. COD, TSS, and Settleable Solids were used to evaluate the performance of organic matter removal. The UASB showed a complete mixing pattern for hydraulic loading rates close to the design value (i.e. Q = 10-13l s(-1) and HRT=8-6 h). Gross mixing distortions and localised stagnant zones, short-circuiting and bypass flows were found in the sludge bed and blanket zones for both extreme conditions (underloading and overloading). The liquid volume contained below the gas-liquid-solid separator was found to contribute to the overall stagnant volume, particularly when the reactor was underloaded. The removal of organic matter showed a log-linear correlation with the dispersion number.

Application of CFD modelling to study the hydrodynamics of various anaerobic pond configurations.

The simulation of hydrodynamics and transport phenomena in waste stabilization ponds is a developing tool worth studying in order to understand their internal processes and interactions. Pond design involves several physical, hydrological, geometric and dynamic variables so as to provide high hydrodynamic efficiency and maximum substrate utilization rates. CFD modelling allows the combination of these factors to predict the behaviour of ponds having different configurations. The two-dimensional depth-integrated model MIKE 21 was used in this study to simulate hydrodynamic and advection-dispersion processes in a full-scale anaerobic pond (AP) located in southwest Colombia. A set of 12 configurations including sludge contents, inlet-outlet positioning, baffling and pond geometry were modelled. Results showed that a crosswise (diagonally opposite) inlet-outlet layout, a length-to-breadth ratio of 2:1, plus provision of two cross baffles at 1/3 L and 2/3 L were the most effective measures to improve overall AP hydrodynamics and dispersion patterns.

Improvement of mixing patterns in pilot-scale anaerobic ponds treating domestic sewage.

Anaerobic ponds are customarily designed as completely mixed reactors. However, evidence from experiments on full-scale facilities shows large deviations from ideal flow models, which in turn cause a reduced process performance. Thus, modified pilot scale anaerobic ponds receiving domestic sewage were developed and studied in parallel. A factorially designed experiment evaluated horizontal and vertical baffling, ponds fitted with cross-sectional plastic nets and a pond with a mixing pit. The hydrodynamic behaviour and process performance of these modified configurations were monitored for four flow rates (1.0, 1.2, 1.5 and 2.0 l/s). The results showed that baffling (vertical and horizontal) and the mixing pit configuration had the best hydrodynamic behaviours and removal efficiencies. Consequently, the development of high-rate anaerobic ponds, through improvements of hydrodynamic behaviour, seems feasible.

Feasibility of waste stabilization pond technology for small municipalities in Colombia.

The selection of any wastewater treatment technology should take into consideration both "software" and "hardware" aspects. There are contrasting opinions regarding the feasibility of waste stabilisation ponds (WSP): some emphasise their advantages while others are concerned with their high land area requirements. As with any technology, WSP are feasible under specific circumstances related to the context where they are to be implemented. In this study data were collected from three regions in Colombia (Nariño, Tolima and Valle del Cauca) in order to assess the feasibility of WSP under real conditions in a tropical country. A feasibility matrix was developed in order to organise and synthesise the information gathered. The results obtained showed that WSP are highly feasible in Tolima and Valle del Cauca due to the fact that these regions have geographical, socio-economic and technical characteristics that enhance the advantages of WSP technology. Nariño has a very mountainous topography along with other local limitations that hinder the application of WSP technology. The cost of land was not found to be a real limitation for the technology, whereas the availability of land is. Finally, the feasibility matrix may be a good planning tool at regional or national levels in order to help decision-making regarding cost-effective wastewater treatment alternatives on the basis of local conditions.

Microbiological quality of a waste stabilization pond effluent used for restricted irrigation in Valle Del Cauca, Colombia.

This paper discusses the applicability of effluent reuse in agriculture after treatment in a series of anaerobic, facultative and maturation ponds. The WSP system is located in Ginebra municipality, a small town in southwest Colombia. The total HRT is 12 days. Several samples of the final effluent were taken over a 55 day period and were analysed for E. coli, Streptococcus spp. and helminth eggs. Some additional grab samples were taken to determine the presence of pathogenic bacteria such as Salmonella spp. and Shigella spp. The results showed that the system was able to remove 4 log units of E. coli, 1 log unit of Streptococcus spp. and 100% of helminth eggs. Meanwhile, Salmonella spp. were detected in the effluent of the facultative pond whilst Shigella spp. were not detected in any sample. The main species of helminth eggs encountered were Taenia spp., Ascaris spp., Trichuris spp., Hymenolepis nana, H. diminuta and Enterobius vermicularis. Removal efficiencies were satisfactory despite the relatively short HRT. Nevertheless, WHO guidelines were slightly surpassed in the case of E. coli for unrestricted irrigation. The helminth egg value was always below the maximum WHO limit. Hence, this effluent can be safely used for restricted irrigation provided that field workers are protected from direct contact with wastewater given the presence of Salmonella spp. in the facultative pond effluent.

Application of an innovative methodology to improve the starting-up of UASB reactors treating domestic sewage.

This study shows the results obtained during the starting-up evaluation of an UASB reactor treating domestic sewage. It is located in the municipality of Ginebra, Valle del Cauca region in Colombia. Its design flow is 7.5 l/s with a maximum capacity of 10 l/s. The reactor was seeded with a deficient quality inoculum which accounted for 20% of the total reactor volume. The starting-up methodology comprised the sequential washing of the sludge (inoculum) by applying three different upflow velocities. This procedure resembles what other authors term the "selective pressure method". Once the sludge was washed, the reactor was started-up with an initial hydraulic retention time (HRT) of 24.9 hours, which was steadily reduced down to 6.7 hours in the final stage. Along the starting-up phase, there was a positive evolution in terms of quantity, quality and spatial distribution of the sludge. Consequently, there was a positive evolution in organic matter removal mechanisms. For HRT above 14 hours, the removal mechanisms were mainly physical whilst for HRT below 9 hours the removal mechanisms were mostly biological. Based on the above considerations and on the water quality parameters measured, it may be concluded that the start-up of an UASB reactor for domestic sewage treatment seeded with a low quality inoculum can be done with HRT as low as 15 or 12 hours. In this way, it is possible to reduce the starting-up period of these reactors down to 4 to 6 weeks, provided that the starting-up methodology is properly applied.