24 research outputs found

    The use of sewage treatment works as foraging sites by insectivorous bats

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    Sewage treatment works with percolating filter beds are known to provide profitable foraging areas for insectivorous birds due to their association with high macroinvertebrate densities. Fly larvae developing on filter beds at sewage treatment works may similarly provide a valuable resource for foraging bats. Over the last two decades, however, there has been a decline in filter beds towards a system of “activated sludge”. Insects and bat activity were surveyed at 30 sites in Scotland employing these two different types of sewage treatment in order to assess the possible implications of these changes for foraging bats. Bat activity (number of passes) recorded from broad-band bat detectors was quantified at three points within each site. The biomass of aerial insects, sampled over the same period as the detector surveys, was measured using a suction trap. The biomass of insects and activity of Pipistrellus spp. was significantly higher at filter beds than at activated sludge sites. In addition, whilst foraging activity of Pipistrellus spp. at filter beds was comparable to that of adjacent “good” foraging habitat, foraging at activated sludge sites was considerably lower. This study indicates the high potential value of an anthropogenic process to foraging bats, particularly in a landscape where their insect prey has undergone a marked decline, and suggests that the current preference for activated sludge systems is likely to reduce the value of treatment works as foraging sites for bats

    The population structure of a peat filter bed system for treating domestic wastewater, and comparisons with conventional activated sludge

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    The protozoan population growing in a peat filter bed located at an urban wastewater treatment plant ("La Cabrera”;, Madrid, Spain) was studied. A high density of microorganisms (2.7106 No./l) was found indicating a considerable biological activity. Comparing the mean characteristics of the protozoan population of a peat filter bed with that of a conventional activated-sludge pilot plant, it was found that 80% of the total population corresponded to free swimming ciliates in the first case, whilst sessile or fixed ciliates dominated in the activated-sludge system. These differences in population structure between purification systems could indicate, that the ciliate population in the peat bed did not reach an equilibrium phase, due to the relatively short operation time used in a pond (25-30 days), and was more similar to the transitional phase in an activated-sludge system. Paramecium sp. was found to be the predominant ciliate in the peat bed although a reasonably diverse population structure was found, which was indicative of aerobic conditions
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