No abstract

The hyporheic environment is composed of a rich meiofauna that depends on water flow, organic matter, and oxygen. The concentration of meiofauna varies spatially (horizontal and vertical) and temporally. Several processes occur at this interface (groundwater and surface water), including biogeochemical processes involving meiofauna. A study of the hyporheic meiofauna community in the sediments of the Beberibe River, in Brazil, was conducted. Meiofauna attained peak densities of 942.8 organisms/10 cm2, with organisms distributed over six taxa, with 98% of them represented by rotifers, nematodes, and annelids. Density was higher in the dry season with an average of 653.1 organisms/10 cm2, and in more superficial sediments with an average of 739.6 organisms/10 cm2. Greater densities were found in coarser sediment with a higher percentage of organic matter. A river bank filtration (RBF) pilot project has been installed, with good results in the attenuation of contaminants and pathogens.

Resumo -As interações que ocorrem entre a água superficial (rios e lagos) e água subterrânea envolvem uma série de processos que devem ser explorados no intuito de entender suas interligações, já que a taxa de recarga e a qualidade da água subterrânea dependem fortemente das características dessa interface. A zona de intercâmbio, conhecida por zona hiporreica é formada por uma camada subsuperficial de sedimentos entre o leito do rio e o aquífero, e suas características favorecem o estabelecimento de algumas espécies, destacando-se a meiofauna. Alguns processos biológicos responsáveis pela modificação da qualidade da água de recarga envolvem esses organismos. Um estudo sobre a comunidade da meiofauna hiporreica foi realizado em três pontos do rio Beberibe, Olinda -PE. A meiofauna esteve composta por um total de 4965 indivíduos, distribuídos em oito taxa, onde 97% dos organismos foram representados pelos rotíferas, nemátodas e anelídeos. A densidade média total variou entre 1446,3 indivíduos/ 10 cm 2 no verão e 12,1 indivíduos/ 10 cm 2 no inverno. A estrutura da comunidade foi correlacionada às variáveis: inverno, verão e granulometria dos sedimentos e o conjunto desses fatores refletiu-se nas características da meiofauna hiporreica do trecho estudado do rio Beberibe-PE. Tanto no verão como no inverno, os pontos onde as densidades de grupos foram mais significativas, foram as dominadas pelas frações arenosas. Palavras-chave:Interação água subterrânea -água superficial. Meiofauna hiporreica. Qualidade da água de recarga.Abstract -The interactions that occur between surface water (rivers and lakes) and groundwater involve a number of processes that should be explored in order to understand their interconnections, since the rate of recharge and groundwater quality strongly depend on the characteristics of this interface. The area of interconnection, known as hyporheic zone is formed by a subsurface layer of sediment from the river bed and the aquifer, and its characteristics favor the establishment of some species, highlighting the meiofauna. Some biological processes responsible for modifying the recharge water quality involve those bodies. A study on hyporheic meiofauna community was performed at three points of Beberibe river, Olinda -PE. The meiofauna was composed of a total of 4965 individuals, distributed in eight taxa where 97% of organizations were represented by rotíferas, nematodes and annelids. The average total density varied between individuals 1446.3 / 10 cm 2 in the summer and 12.1 individuals / 10 cm 2 in winter. The community structure was correlated to the variables: winter, summer and grain size of the sediment and the combination of these factors were reflected in characteristics of hyporheic zone of Beberibe river -PE. Both in summer and in winter, the points where the densities groups were more significant were dominated by sandy fractions.

Entre os processos de autopurificação natural que ocorrem na zona hiporreica, estão os de aspecto biológico, onde os organismos da meiofauna desempenham importantes funções, favorecendo a melhoria da qualidade da água de recarga do aquífero subjacente ao rio. São diversos os fatores que influenciam a distribuição vertical da comunidade meiofaunística como o hidrodinamismo na massa hídrica superficial e a disponibilidade de matéria orgânica e oxigênio nas camadas mais profundas. Por isso, este artigo objetivou avaliar a influência destes dois fatores na distribuição vertical da meiofauna hiporreica em três pontos do rio Beberibe-PE. O hidrodinamismo foi considerado como resultado direto do regime pluviométrico e o fluxo vertical entre o rio e o aquífero foi analisado a partir de medições realizadas em três períodos pluviométricos distintos com auxílio do piezômetro diferencial. A análise da distribuição vertical da meiofauna foi realizada a partir do levantamento da abundância média em camadas de 2 cm até a profundidade de 10 cm. Foram contabilizados 4906 indivíduos pertencentes a 8 grupos taxonômicos. Os resultados mostraram que as camadas superficiais foram as mais abundantes. Entretanto, a diminuição desta abundância não se deu gradativamente com a profundidade, provavelmente por uma vazão maior do rio no período chuvoso e/ou por condições de rio influente. Apesar de que estes fatores não demonstraram um caráter completamente determinante sobre a distribuição vertical.

The interaction between groundwater and surface water occurs naturally and is dependent on the dynamics in the hyporheic zone. The hyporheic zone is the interface between the surface water source and the phreatic aquifer and it's a system that also influences the water quality. An important feature is the ability to flux in this zone. This work aimed to evaluate the vertical hydraulic gradient in the hyporheic zone at two points in Beberibe river, Olinda-PE, to understand the hyporheic environment characteristics and water flow dynamics in experimental area, in addition to identify the existence of hydraulic connection between surface water and groundwater. The experimental phase consisted of infiltration tests in riverbed with cylinder infiltrometer and vertical hydraulic gradients readings with differential piezometer, complemented with grain size information, for an assessment of the water budget between the river and the aquifer. Analyzing the behavior of the interaction over the period of 10 months, it was observed that the Beberibe river (middle course) contributes to the groundwater recharge in most of the time. The average infiltration rate was 1.02 mm/min in point 1 and 0.85 mm/min in point 2. It was concluded that there is a variability in flow direction, which often is top-down, but may undergo change in the stream showing upstream after long periods of rainfall. Another conclusion is that grain size distribution of bed sediment, that is predominantly sandy, influences hydraulic conductivity of hyporheic zone and influences consequently the vertical flow rates.Keywords: River-aquifer interaction; Infiltration; Cylinder infiltrometer; Differential piezometer; Hyporheic zone. RESUMOA interação entre águas subterrânea e superficial ocorre naturalmente e depende da dinâmica na zona hiporreica. A zona hiporreica é a interface entre o corpo hídrico superficial e o meio subterrâneo, sendo um sistema que também influencia a qualidade da água. Uma importante característica é a capacidade de fluxo nesta zona. O trabalho objetivou avaliar o fluxo vertical de água na zona hiporreica em dois pontos do rio Beberibe, Olinda -PE, para compreender as características do ambiente hiporreico e a dinâmica do fluxo de água nesta zona, além de identificar a existência de conexão hidráulica entre a água superficial e subterrânea. A fase experimental consistiu em ensaios de infiltração no leito com infiltrômetro de cilindro e leituras da diferença da carga hidráulica com piezômetro diferencial, complementadas com informações granulométricas, para uma avaliação da capacidade de transporte de volumes hídricos entre o rio e o aquífero. Analisando-se o comportamento da interação ao longo do período de 10 meses, verificou-se que o rio Beberibe no seu curso médio contribui para a recarga do lençol freático em boa parte do tempo, sendo a média da taxa de infiltração de 1,02 mm/min no ponto 1 e de 0,85 mm/min no ponto 2. Concluiu-se que há uma variabilidade no sentido do fluxo, que geralmente é de cima para baixo, mas pode so...

In bank filtration (BF) technology, a production well is pumped near surface water and induces water flow from the river through a porous medium to the well by percolation into the soil.Several physical, chemical, and biological processes occur, providing a natural water treatment along the river banks. An experimental area was installed on the Beberibe River with 2 production wells and 7 monitoring wells. The BF potential in removing pathogenic intestinal parasites and analysis of physical-chemical and bacteriological parameters was evaluated, according to Standard Methods. River-aquifer interaction was characterized by piezometric levels of production wells. Monitoring of the wells was correlated with the water depth of the river and precipitation. Parasite analysis was performed using Hoffman, Pons, and Janer's methods of spontaneous sedimentation, followed by centrifugation and preparation of slides stained with acetic Lugol. Protozoa oocysts were isolated by a modified Ziehl-Neelsen method, preceded by sedimentation and centrifugation. The pathogenic protozoa found in samples from Beberibe River were Cryptosporidium spp., Giardia spp., Entamoeba histolytica/dispar complex, and Isospora belli. Pathogenic helminths were also detected: Ascaris lumbricoides, Strongyloides stercoralis, and hookworm eggs and larvae, Hymenolepis nana. In water samples from the production wells, no waterborne pathogens were found. The BF pilot project was effective in reducing levels of turbidity and color. Total coliforms and Escherichia coli were absent in the production wells.Piezometric levels of production wells and monitoring wells correlated with water depth of Beberibe River show hydraulic connection between the production wells and river, thus featuring a river-aquifer interaction. The BF pilot system showed potential for reduction or elimination of pathogenic intestinal parasites.

Knowledge about the hyporheic zone is important to understand the pollutant attenuation processes that occur during the aquifer recharge, whether by natural or artificial means, for example, Bank Filtration. In this paper, the structure of the hyporheic meiofauna and the influence of pollution, microphytobenthos and sedimentological parameters (grain size, organic matter and CaCO 3 content) were studied at a periurban area of Beberibe River (Northeastern Brazil), the location of a riverbank filtration (RBF) pilot project. PERMANOVA analysis indicated interactions between meiofauna community and the sampling sites, rainfall seasons, and depth. The release of untreated wastewater was the most influential factor for physical and biochemical features of the hyporheic zone, since the sampling sites with higher levels of elements related to eutrophication supported the highest levels of meiofauna abundance, fine sediments, organic matter, and CaCO 3 content. It was verified that organic matter from domestic wastewater in tropical streams can promote protective effects that favor the retention and biodegradation of pollutants in the hyporheic zone. The results reveal that, even in eutrophic rivers, there are factors that contribute to the processes of pollutant attenuation in tropical hyporheic environments. The results demonstrate the potential for using RBF in communities without adequate sanitation, especially in developing countries.