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Number of results: 12
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Abstract

The primary objective of the present study was to determine the seasonal dynamics of ciliates in activated sludge. Studies were carried out in order to verify the hypothesis that fertility of a habitat may significantly influence the seasonal dynamics of the abundance of ciliates, as well as the number and intensity of correlations between physic-chemical parameters and ciliates. It seems that the values of numbers of ciliates were seasonally changeable. The highest numbers of ciliates were found in spring and summer, however the lowest numbers of ciliate communities were noted in winter. The studies showed that protozoa community is determined by ammonia mainly in summer. In spring and winter additional factors may be important. Probably suspended solid, total organic carbon and concentration of appropriate food (bacteria and flagellates) are the major regulator of abundance of ciliates.
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Abstract

Primary or secondary sewage sludge in medium and large WWTP are most often processed by anaerobic digestion, as a method of conditioning, sludge quantity minimization and biogas production. With the aim to achieve the best results of sludge processing several modifications of technologies were suggested, investigated and introduced in the full technical scale. Various sludge pretreatment technologies before anaerobic treatment have been widely investigated and partially introduced. Obviously, there are always some limitations and some negative side effects. Selected aspects have been presented and discussed. The problem of nitrogen has been highlighted on the basis of the carried out investigations. The single and two step - mesophilic and thermophilic - anaerobic waste activated sludge digestion processes, preceded by preliminary hydrolysis were investigated. The aim of lab-scale experiments was pre-treatment of the sludge by means of low intensive alkaline and hydrodynamic disintegration. Depending on the pretreatment technologies and the digestion temperature large ammonia concentrations, up to 1800 mg NH4/dm3 have been measured. Return of the sludge liquor to the main sewage treatment line means additional nitrogen removal costs. Possible solutions are discussed.
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Abstract

Improving the effects of hydrolysis on waste activated sludge (WAS) prior to anaerobic digestion is of primary importance. Several technologies have been developed and partially implemented in practice. In this paper, perhaps the simplest of these methods, alkaline solubilization, has been investigated and the results of hydrolysis are presented. An increase to only pH 8 can distinctively increase the soluble chemical oxygen demand (SCOD), and produce an anaerobic condition effect favorable to volatile fatty acids (VFA) production. Further increases of pH, up to pH 10, leads to further improvements in hydrolysis effects. It is suggested that an increase to pH 9 is sufficient and feasible for technical operations, given the use of moderate anti-corrosive construction material. This recommendation is also made having taken in consideration the option of using hydrodynamic disintegration after the initial WAS hydrolysis process. This paper presents the effects of following alkaline solubilization with hydrodynamic disintegration on SCOD
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Abstract

The prevalence of heavy metals in wastewater is the cause of death of numerous organisms which take part in biological treatment of wastewater, that is why the aim of the study has been to asses the influence of cadmium and copper ions upon the microfauna of activated sludge. 5, 10, 50, and 100 mg/l of Cd2+ and Cu2+ were added into the samples of activated sludge and then, after 24 hours, the microscopic observations of activated sludge microfauna were carried out, and all changes concerning the amount of microfauna, functional groups, and species composition were determined. The results obtained allowed to find a high level of toxicity of Cd2+ and Cu2+ ions to activated sludge microfauna, which resulted in the changes in the value of the Sludge Biotic Index and classes of sludge, survivability of microfauna, and reduction in the number of taxonomic units. It was observed that Cu2+ ions are more toxic to activated sludge microfauna than Cd2+ ions in identical doses. Organisms sensitive to Cd2+ and Cu2+ ions have been found to be testate amoebae, Aspidisca sp. and Epistylis sp., as well as organisms relatively sensitive to tested metals, which turned out to be ciliates of Opercularia and Vorticella convalaria genera.
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Abstract

The aim of the study was to develop an effective treatment of post-digestion liquors highly-loaded with biogenic and organic substances. The scope of the research project encompassed: mesophilic anaerobic digestion of waste activated sludge (WAS) as well as the treatment of post-digestion liquors, coming from the most appropriate HRT value of 25 days, in the process of ammonium magnesium phosphate (struvite) precipitation targeted at ammonia nitrogen binding and a subsequent reverse osmosis (RO) process. It was established that the method combining chemical precipitation and high-pressure filtration ensures a high degree of contaminants removal allowing for a direct release of treated liquors into the natural reservoir. However, in order to decrease the residual NH4+ concentration (6.1 mg NH4+/dm3) in the purified post-digestion liquors below the level allowing for a direct release to the natural reservoir, it turned out to be necessary to apply increased molar ratio of magnesium and phosphates (Mg:NH4+: PO43-= 1.5:1:1.5).
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Abstract

Monitoring of activated sludge flocs may provide important information for effective operation and control of wastewater treatment. The research objective is to demonstrate methodology for activated sludge image processing aimed to describe morphological characteristics of activated sludge flocs. The proposed software- -based method was presented and verified by analysis of several activated sludge samples. The results show high efficiency of image segmentation and floc recognition of more than 94% floc components. The analysis of a series of 50 pictures gives rapid and reliable results and can be performed in an automatic or semiautomatic mode. Given inherent heterogeneity of activated sludge flocs, multiple and repeated sample images capture (processing of 50 pictures at a time, repeated at least 4 times ) is recommended.
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Abstract

The aim of this work was to determine the influence of various variants of bioleaching on effectivity of releasing chosen critical metals: rhodium, cadmium, indium, niobium and chromium from ashes which are a byproduct of municipal waste and sewage sludge thermal processing. The research was conducted in 3 variants that considered different process factors such as temperature (24ºC and 37ºC), mixing intensity and aeration. After 5 days of the process the analyses were made of metals content, sulfate concentration, pH, general number of bacteria number, index of sulfur oxidizing bacteria. The best results of bioleaching were achieved by running the process at the temperature of 24ºC with aeration. The efficiency of rhodium and cadmium release from the byproduct of municipal waste thermal processing was above 90%. The efficiency of indium and chromium release reached 50–60%. Only niobium leached better in mixing conditions. The byproduct of sewage sludge thermal processing was far less susceptible to bioleaching. The highest effectivity (on a level of 50%) was reached for indium in temperature of 24°C with aeration. The efficiency of bioleaching depended on waste’s physiochemical properties and type of metal which will be released. Aeration with compressed air had a positive influence on the increase of sulfur oxidizing bacteria what corresponded with almost double increase of sulfate concentration in leaching culture. Such conditions had a positive influence on the increase of the efficiency of bioleaching process. Heightening the temperature to 37°C and slowly mixing did not impact bioleaching in a positive way.
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Abstract

This study investigates the influence of four imidazolium ionic liquids (ILs) present in wastewater on the activated sludge process. In addition, experiments with inactivated sludge to assess the capacity of this sorbent to remove ILs from the wastewater were conducted. It occurred that the presence of ionic liquids in wastewater reduces biomass growth and size of the sludge flocs. The strongest effect has been found for IL 6 (1-hexyl-2H-3-methyl-4,5-dimethylimidazolium iodide) with the longest alkyl chain length. Also, the degree of ILs removal increases with the alkyl chain length and decreases with the increase of initial concentration of ILs in wastewater. IL 6 reaches the highest degree of ILs removal from wastewater but inhibits the biomass growth and growth of sludge flocs in a greater extent than other tested compounds. Moreover, it was confirmed that newly synthesized ionic liquids can be adsorbed onto inactivated sludge. IL 6 could be adsorbed in a higher degree than other ionic liquids. This adsorption was described by Langmuir isotherm, whereas adsorption of other ionic liquids was described by Freundlich isotherm.
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Abstract

The paper deals with the problem of the determination of the effects of temperature on the efficiency of the nitrification process of industrial wastewater, as well as its toxicity to the test organisms. The study on nitrification efficiency was performed using wastewater from one of Polish chemical factories. The chemical factory produces nitrogen fertilizers and various chemicals. The investigated wastewater was taken from the influent to the industrial mechanical-biological wastewater treatment plant (WWTP). The WWTP guaranteed high removal efficiency of organic compounds defined as chemical oxygen demand (COD) but periodical failure of nitrification performance was noted in last years of the WWTP operation. The research aim was to establish the cause of recurring failures of nitrification process in the above mentioned WWTP. The tested wastewater was not acutely toxic to activated sludge microorganisms. However, the wastewater was genotoxic to activated sludge microorganisms and the genotoxicity was greater in winter than in spring time. Analysis of almost 3 years’ period of the WWTP operation data and laboratory batch tests showed that activated sludge from the WWTP under study is very sensitive to temperature changes and the nitrification efficiency collapses rapidly under 16°C. Additionally, it was calculated that in order to provide the stable nitrification, in winter period the sludge age (SRT) in the WWTP should be higher than 35 days.
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Abstract

The analysis of particle size in suspensions carried out with use of the laser diffraction method enables us to obtain not only information about the size of particles, but also about their properties, shape and spatial structure, determined basing on fractal dimension. The fractal dimension permits the evaluation of the interior of aggregates, at the same time showing the degree of complexity of the matter. In literature, much attention is paid to the evaluation of the fractal dimension of flocs in activated sludge, in the aspect of control of single processes, i.e. sedimentation, dehydration, coagulation or flocculation. However, results of research concerning the size of particles and the structure of suspensions existing in raw and treated sewage are still lacking. The study presents optical fractal dimensions D3 and particle size distributions measured with use of laser granulometer in raw and treated sewage and activated sludge collected from six mechanical-biological wastewater treatment plants located in the Lower Silesian region. The obtained test results demonstrate that wastewater treatment plants that use both sequencing batch reactors and continuous flow reactors are more efficient at capturing suspension particles of a size up to 30 μm and are characterized by an increased removal of particles of a size ranging from 30 μm to 550 μm to the outflow. Additionally, in the case of samples of treated sewage and activated sludge collected at the same location, at short intervals, similar particle distributions were observed. As far as the analysis of fractal dimensions is concerned, particles contained in the raw sewage suspension were characterized by the lowest values of the fractal dimension (median equals 1.89), while the highest values occurred in particles of activated sludge (median equals 2.18). This proves that the spatial structure of suspension particles contained in raw sewage was similar to a linear structure, with a large amount of open spaces, while the structure of particles contained in the activated sludge suspension was significantly more complex in the spatial aspect.
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