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ABSTRACT: A survey has been carried out involving 55 Hungarian wastewater treatment plants in order to evaluate the wastewater quality, the applied technologies and the resultant problems. Characteristically the treatment temperature is very wide-ranging from less than 10 °C to higher than 26 °C. Influent quality proved to be very variable regarding both the organic matter (typical COD concentration range 600-1,200 mg l(-1)) and the nitrogen content (typical NH(4)-N concentration range 40-80 mg l(-1)). As a consequence, significant differences have been found in the carbon availability for denitrification from site to site. Forty two percent of the influents proved to lack an appropriate carbon source. As a consequence of carbon deficiency as well as technologies designed and/or operated with non-efficient denitrification, rising sludge in the secondary clarifiers typically occurs especially in summer. In case studies, application of intermittent aeration, low DO reactors, biofilters and anammox processes have been evaluated, as different biological nitrogen removal technologies. With low carbon source availability, favoring denitrification over enhanced biological phosphorus removal has led to an improved nitrogen removal.
Water Science & Technology 01/2012; 65(9):1676-83. · 1.12 Impact Factor
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ABSTRACT: In order to reduce the pollution load of the Danube, the North-Budapest Wastewater Treatment Plant has been upgraded to enhanced nitrogen removal by establishing a new activated sludge treatment line and modifying the existing unit for nitrification and denitrification. As both the influent flow rate and the influent chemical oxygen demand (COD), biological oxygen demand (BOD(5)) and total suspended solids (TSS) concentration levels remained far below the design values, setting one fourth of the reactor volume out of operation in the Old Line, and operating the nitrification reactor of the New Line with part-time aeration proved to be possible. Analytical data as well as simulation studies supported the advantage of the intermittent-aeration process in efficient N-removal. However, the lengths of the aerated periods have to be increased with decreasing temperature, and thereby effluent total nitrogen (TN) concentration can increase due to decreasing denitrification efficiency. Potential occurrence of low-dissolved oxygen (DO) bulking should be hindered through applying an efficient anoxic selector system.
Water Science & Technology 01/2012; 65(10):1801-8. · 1.12 Impact Factor
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ABSTRACT: The purpose of the experiments was to increase the rate of activated sludge denitrification in the combined biological treatment system of the Southpest Wastewater Treatment Plant in order to gain savings in cost and energy and improve process efficiency. Initial profile measurements revealed excess denitrification capacity of the preclarified wastewater. As a consequence, flow of nitrification filter effluent recirculated to the anoxic activated sludge basins was increased from 23,000 m3 d(-1) to 42,288 m3 d(-1) at an average preclarified influent flow of 64,843 m3 d(-1), Both simulation studies and microbiological investigations suggested that activated sludge nitrification, achieved despite the low SRT (2-3 days), was initiated by the backseeding from the nitrification filters and facilitated by the decreased oxygen demand of the influent organics used for denitrification. With the improved activated sludge denitrification, methanol demand could be decreased to about half of the initial value. With the increased efficiency of the activated sludge pre-denitrification, plant effluent COD levels decreased from 40-70 mg l(-1) to < 30-45 mg l(-1) due to the decreased likelihood of methanol overdosing in the denitrification filter.
Water Science & Technology 01/2008; 57(8):1287-93. · 1.12 Impact Factor
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ABSTRACT: To meet the effluent requirements given for the sensitive receiving body, the Southpest Wastewater Treatment Plant of Budapest, Hungary uses a combined activated sludge-biofilter system with chemical precipitation for P removal. Causes of the proliferation of glycogen accumulating organisms (GAOs) observed in the unaerated/oxic activated sludge unit of this system were investigated both in full-scale and in lab-scale experiments combined with a detailed analysis of the microbial communities. Concentration profile measurements throughout the 8-stage activated sludge unit indicated anaerobic conditions in the first two unaerated reactors and low orthophosphate level (< 1 mg l(-1)) in all of the stages that could not be attributed to the influent quality, but to Fe (III)-dosing to the returned activated sludge. Microbiological analysis revealed the presence of GAOs from the GB group in the Gammaproteobacteria and occasionally tetrad-forming organisms from Actinobacteria, and the absence of Rhodocyclus-related polyphosphate accumulating organisms (PAOs) in the activated sludge samples. Comparative lab-scale studies carried out in two identically arranged UCT-systems with staged anoxic reactors also confirmed that Fe (III)-dosing may result in phosphorus deficiency of the microbial niche, leading to the suppression of growth and EBPR activity of PAOs and to the proliferation of GAOs.
Water Science & Technology 01/2006; 54(1):101-9. · 1.12 Impact Factor
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ABSTRACT: In 1999 the existing activated sludge unit of the Southpest Wastewater Treatment Plant was supplemented by a two-stage biofilter system aiming for nitrification and post-denitrification. In this arrangement excess biomass of the filters is wasted through the activated sludge unit, facilitating backseeding, and recirculation of the nitrate-rich effluent of the N-filter serves for decreasing the methanol demand of the DN-filter and for saving aeration energy at the same time. The paper reports on the development of an ASM1-based mathematical model that proved to be adequate for describing the interactions in the combined system and was used to compare the efficiency of different treatment options. Full-scale results verified that backseeding may considerably improve performance. However, nitrification ability of the activated sludge unit depends on the treatment temperature and, if unexpected, can be limited by insufficient oxygen supply. The upgrading possibilities outlined may serve as a new perspective for implementation of combined activated sludge-biofilter systems.
Water Science & Technology 02/2004; 50(7):1-8. · 1.12 Impact Factor
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ABSTRACT: Activated sludge treatment of nutrient-deficient wastes may lead to severe slime formation and consequent biomass separation difficulties. The purpose of this paper has been to show that bioreactor arrangement essentially influences the manner of biological excess carbon removal. In a comparative lab-scale experiment two differently arranged activated sludge systems were operated simultaneously: an aerated CSTR with an aerobic selector and an aerated CSTR with an anaerobic selector. The seed derived from an anaerobic/aerobic activated sludge plant of a winery. The model wastewater contained wine, sugar and acetic acid as organic carbon sources and lacked nutrients regarding both N and P, similarly to the influent of the full-scale plant. During the 52 days of the experiment the SVI values of the fully aerated system increased up to 600-800 cm3 g(-1) whereas those of the anaerobic/aerobic system remained below 250 cm3 g(-1) The SVI values showed a strict correlation with the amount of extracellular polysaccharides. In the anaerobic/aerobic experimental system, the high (40% of MLSS) intracellular polysaccharide content of the seed could be maintained. Besides the analytical data, also the microscopic observations of the biomass structure referred to the presence of glycogen accumulating organisms in both the lab- and full-scale anaerobic/aerobic systems.
Water Science & Technology 02/2002; 46(1-2):185-90. · 1.12 Impact Factor
