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Number of results: 6
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Abstract

Sewage sludge is a two-phase mixture, generated during the treatment of domestic sewage in waste water treatment plants. It consists of 90-99% water and an accumulation of settleable solids. mainly organic that are removed during primary, secondary or advanced wastewater treatment processes. The hydration of the sludge is one of its main properties which determines sludge management and waste disposal cost. The flow properties of the sewage sludge, such as settling properties and concentration of solids. may affect its hydraulics. Application of rheology in wastewater treatment is determined by the flow character of the sludge. The basic purpose of the investigation was to define the rheological properties of sludge taken from secondary settling tanks in a typical municipal wastewater treatment plant. A laboratory investigation was conducted using a coaxial cylinder with a rotating torque and gravimetric concentration of the investigated sludge ranged from 2.21 to 6.56%. Approximation was made after transforming the pseudo-curve obtained from the measurements into the true flow curve, which was made according to the equation provided by Krieger, Elrod, Maron and Svec. In order to describe rheological characteristics the 3-parameter Herschel-Bulkley model was applied. The correlation between rheological parameters -r , k, n and concentration C was calculated as well as between periods of time when the samples of sludge were 'taken. The research has allowed calculating the dimension of the main transport installation pumping sludge and optimizing the pump discharge pressure, when transporting viscous sludge in pipelines. Determination of rheological parameters, especially yield stress tr), is important in sludge management, for instance in designing parameters transporting, storing, spreading.
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Authors and Affiliations

Beata Malczewska
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Abstract

The aim of the present study was to examine changes in species composition and density of ciliates in an adjacent river, ccotone and reservoir zone (Zemborzycki Reservoir, Eastern Poland). Quality and quantity structure of planktonie ciliates showed visible differences between studied zones; the highest species diversity and abundance were observed in the ecotone (water/water). The lowest species diversity and abundance were noted in the Bystrzyca River. Independent on the zone, ciliates community was dominated by bacterivorous species with the lowest proportions of algivorous tax a. The present study showed that density of protozooplankton rose with the increase of nutrients delivery and TOC concentration in water.
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Authors and Affiliations

Tomasz Mieczan
ORCID: ORCID
Monika Tarkowska-Kukuryk
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Abstract

Hg concentration was studied in waters of 16 lakes in the Suwałki Landscape Park. The samples of lake water were collected from the surface zone and I m above the bottom, in the deepest site of the lakes. Apart from Hg concentration, the measurements included: the pH, soluble oxygen, water saturation with oxygen, electrolytic conductivity and total hardness of water. Hg concentration varied from lake to lake, but remained at the same levels in consecutive years. It has been found that Hg concentration in the bottom zone is higher than that in the surface zone. Significant differences were found between mean Hg concentrations in the bottom zone both during the summer and winter stagnation. No significant differences were found in mean Hg concentration in surface waters in different seasons of the year.
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Authors and Affiliations

Wojciech Dobicki
Ryszard Polechoński
Przemysław Pokorny

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