Artykuły w czasopismach na temat „Activated sludge”
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1
Noyola, Adalberto, i Gloria Moreno. "Granule production from raw waste activated sludge". Water Science and Technology 30, nr 12 (1.12.1994): 339–46. http://dx.doi.org/10.2166/wst.1994.0633.
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Granulation is an important characteristic of sludges used in upflow anaerobic sludge blanket (UASB) reactors. As the UASB technology is rapidly spreading, there is a need of granular sludge for inoculation of new reactors, particularly in those countries where anaerobic technologies have been just recently accepted. Alternative sources of inocula are digested sludge, digested manure, septic tank sludges and pond sediments. Raw waste activated sludges have also been identified as a convenient material for reactor seeding, with previous treatment. In this work, anaerobic flocculant sludge obtained from raw waste activated sludge has been granulated with hydraulic stress, in a lab-scale column under different upflow velocities (1 to 50 m h−1). A methodology is proposed for enhancing the quality of non granular anaerobic sludges in batch treatments of less than 8 hours. The granular sludge produced was used as inoculum for a UASB lab scale reactor. The seed sludge improved all its characteristics and maintained the granulation, in spite of the low velocity (0.08 m h−1) applied.
2
de Beer, Dirk, Andreas Schramm, Cecilia M. Santegoeds i Helle K. Nielsen. "Anaerobic processes in activated sludge". Water Science and Technology 37, nr 4-5 (1.02.1998): 605–8. http://dx.doi.org/10.2166/wst.1998.0726.
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We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H2S, O2, NO2− and NO3−. Denitrification and sulfate reduction rates were mmeasured with 15N- and 35S-tracer techniques. We showed that under normal reactor conditions (ca. 20% air saturation) anoxic zones develop within flocs allowing denitrification. The denitrification rates amounted to 40% of the rates under anoxic conditions. At 100% air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20% air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport. Sulfate reduction was not detected in any of the sludges tested by microsensors or by tracer techniques even under anoxic conditions. this indicates that the sulfur cycle (sulfate reduction and sulfide oxidation) does not play a role in mineralization processes and bulking in activated sludge. Preliminary molecular work (in situ hybridization with the 16S-rRNA probe SRB385) indicated the presence of small amounts of sulfate reducing bacteria in all sludges. Either the probe is not specific or the sulfate reducers present are not active under reactor conditions.
3
Tonkovic, Zlatko. "Aerobic stabilisation criteria for BNR biosolids". Water Science and Technology 38, nr 2 (1.07.1998): 133–41. http://dx.doi.org/10.2166/wst.1998.0123.
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A research program was undertaken to establish the stability of waste activated sludge generated from seven activated sludge treatment plants, both nutrient removal and conventional, and determine what further treatment is required to produce a substantially stabilised (ie. non-odorous) sludge. It has been previously thought that waste activated sludge from extended aeration plants (sludge age of approximately 25 days) was sufficiently stabilised to permit dewatering and stockpiling without odour generation. However, experience at a number of treatment plants with large unaerated mass fractions for biological removal of nitrogen and phosphorus has demonstrated that these sludges are generally odorous. With the increasing requirement for on-site storage of sludge to remove pathogens prior to sludge re-use, odour generation from secondary sludges has the potential to pose significant environmental problems for many treatment plants. The objective of the research program was to quantify the degree of stabilisation achieved in various activated sludge treatment plants, what additional aerobic treatment is required to achieve a stabilised sludge and what are the readily identified characteristics of a stabilised sludge, including volatile solids content, specific oxygen uptake rate and pathogen destruction. The phosphorus leaching characteristics were also compared between various sludges and between continuous and intermittent aerobic digestion process.
4
Tonkovic, Zlatko. "Aerobic stabilisation criteria for BNR biosolids". Water Science and Technology 39, nr 6 (1.03.1999): 167–74. http://dx.doi.org/10.2166/wst.1999.0290.
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A research program was undertaken to establish the stability of waste activated sludge generated from several activated sludge treatment plants, both nutrient removal and conventional, and determine what further treatment is required to produce a substantially stabilised (ie. non-odorous) sludge. It has been previously thought that waste activated sludge from extended aeration plants (sludge age of approximately 25 days) was sufficiently stabilised to permit dewatering and stockpiling without odour generation. However, experience at a number of treatment plants with large unaerated mass fractions for biological removal of nitrogen and phosphorus has demonstrated that these sludges are generally odorous. With the increasing requirement for on-site storage of sludge to remove pathogens prior to sludge re-use, odour generation from secondary sludges has the potential to pose significant environmental problems for many treatment plants. The objective of the research program was to quantify the degree of stabilisation achieved in various activated sludge treatment plants, what additional aerobic treatment is required to achieve a stabilised sludge and what are the readily identified characteristics of a stabilised sludge, including volatile solids content, specific oxygen uptake rate and pathogen destruction. The phosphorus leaching characteristics were also compared between various sludges and between continuous and intermittent aerobic digestion processes.
5
Dregulo, A. M. "A STUDY OF HEAVY METAL COMPOSITIONS AND PHOSPHATES IN POLYMER SUBSTANCES OF THE ACTIVATED SLUDGE BIOMASS". Water and Ecology 25, nr 3 (2020): 8–13. http://dx.doi.org/10.23968/2305-3488.2020.25.3.8-13.
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Introduction. Heavy metals discharged with wastewater can lead to a toxic effect on the microbiocenosis of activated sludge and significantly decrease the degree of wastewater treatment, which dictates the need for a more detailed study and search for ways to detoxify activated sludge at the recycling stage and, at the same time, solve the problems of the neutralization of sewage sludge for safe soil disposal. To ensure the adequacy of the approach to the choice of the methodology for the neutralization of sludge, including sewage sludge, it is necessary to perform compositional analysis of their organic fractions and heavy metal compositions. Methods. To determine the quantitative content of organic components in activated sludge, a sample of sludge was dried to an air-dry state and then subjected to separation into fractions using a method based on the different solubility of compounds with the use of different solvents. Then, extractants were added step by step to the weighted samples of sewage sludge weighing about 2 g each (in a volume 20 times greater than the weight of the weighted sample (40 ml)). Results. The results of the study show that polysaccharides are the dominant form of the organic fraction (polymers) in sewage sludge. Most heavy metals were identified in acidic polysaccharides, humic-like acids and lipids. Significant concentrations of phosphates were observed for the same components of polymer substances in the biomass of activated sludges. Conclusion. The products of extraction of polymer substances of the activated sludge biomass and the content of heavy metals in them may indicate the biosorption of heavy metals by zoogleal accumulations (having a polysaccharide structure) of activated sludges in aeration tanks during biological treatment. Therefore, extracellular biopolymers can be a “target” in the development of targeted technologies for the neutralization of activated sludges.
6
Demel, I., i C. H. Möbius. "Improving the Settling of Activated Sludge by Chemical Additives". Water Science and Technology 20, nr 1 (1.01.1988): 283–86. http://dx.doi.org/10.2166/wst.1988.0036.
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One of the main problems encountered in biological waste water treatment plant of papermills is poor settling of activated sludge in secondary sedimentation tanks. In many cases, activated sludge volume indices stay above 150 ml/g. Moreover, bulking of sludges in activated sludge plants of papermills is more frequent than usual. Bulking sludge is characterized by excessive growth of filamentous microorganisms. In a lab-scale activated sludge plant, tests were made to improve the settling of activated sludge by adding the following chemicals: Lime, alkaline activated bentonite, powdered lignite coke, polyelectrolytes used as flocculants. The findings reveal that dosage of the above additives actually gives improved sedimentation. Moreover, biochemical degradation becomes more effective if bentonite and powdered lignite coke are added. Test results are evaluated to determine the extent to which settling of the activated sludge and plant efficiency are improved, taking into account operational and waste water parameters. Using lime, bentonite, lignite coke or polyelectrolytes is an economic method of fighting or preventing acute or permanent problems caused by bulking sludge and high sludge volume indices.
7
Ilyasov, O. R., M. V. Kirillov, I. I. Gavrilin, O. A. Bykova i A. M. Asonov. "Resource-saving technology for dewatering and decontamination of activated sludge". E3S Web of Conferences 282 (2021): 05003. http://dx.doi.org/10.1051/e3sconf/202128205003.
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The authors of the article consider the problem of the formation of huge volumes of liquid toxic activated sludge in the biochemical method of the residential area wastewater decontamination. At present, there are no effective technical solutions and technologies in terms of eliminating the negative impact of activated sludge on environmental components. The article examines the technologies that allow to involve activated sludges in reuse and use them as fertilizers in agriculture. A resource-saving biotechnology for activated sludge dewatering and decontamination from ecotoxicants has been developed. The results of the study confirm the effectiveness of the process of heavy metal extraction from activated sludge.
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Aitken, Michael D., Phillip E. Heck, Richard O. Mines i Joseph H. Sherrard. "Activated sludge". Water Environment Research 64, nr 4 (czerwiec 1992): 347–59. http://dx.doi.org/10.1002/j.1554-7531.1992.tb00009.x.
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Aitken, Michael D., Phillip E. Heck, Lisa Alvarez-Cohen, Stefan J. Grimberg i William T. Stringfellow. "Activated sludge". Water Environment Research 65, nr 4 (czerwiec 1993): 324–36. http://dx.doi.org/10.1002/j.1554-7531.1993.tb00055.x.
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Ichihashi, O., H. Satoh i T. Mino. "Sludge–sludge Interaction in the Enhanced Biological Phosphorus Removal Process". Water Science and Technology 53, nr 6 (1.03.2006): 1–6. http://dx.doi.org/10.2166/wst.2006.161.
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Metabolisms related to enhanced biological phosphorus removal (EBPR) were found to be affected when two activated sludges with different EBPR activities were mixed together. In the present study, two laboratory scale EBPR processes were operated in parallel, one of them with higher and another with lower EBPR activities. The activated sludges from the two reactors were mixed together at different mixing ratios. The supernatant was made the same for all mixing ratios, anaerobic–aerobic batch experiments were performed, and acetate uptake rate and phosphate release rate under anaerobic conditions and phosphate uptake rate under aerobic condition were determined. The metabolic rates measured were expected to be linear to the mixing ratios, as the supernatant was the same for all mixing ratios, whereas the metabolic rates were either promoted or inhibited by mixing of sludges. As an indicator for the sludge mixing effect on the metabolic rates, mixing effect intensity (MEI) was introduced. Chemical substances that are produced by microorganisms in activated sludge are proposed to be one of the possible causes of the sludge mixing effect.
11
Navrátilová, P. "Pathogenic micro-organisms in waste waters from daiies". Czech Journal of Food Sciences 18, No. 5 (1.01.2000): 170–74. http://dx.doi.org/10.17221/8338-cjfs.
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Waste waters from dairies were tested for the presence of bacterial pathogens – Listeria monocytogenes, Staphylococcus aureus and Salmonella spp. The prevalence of bacteria was investigated in each stage of the cleaning process (activated sludges systems) too. Two hunder samples of raw waste water, activated sludge, returned activated sludge, excess sludge and treated water from 14 dairies were tested. The samples were all negative for Salmonella spp. From a total of 102 (51%) strains Listeria spp., Listeria inoccua 95 (47.5%) and Listeria monocytogenes 7 (3.5%) were identified. 47 samples were positive for S. aureus. L. monocytogenes were detected in raw waste water 1 (1.6%), in activated sludge 3 (5.5%), in excess sludge 1 and in treated water 2 (3.1%). S. aureus were detected in raw waste water 14 (22.6%), in activated sludge 23 (41.8%), in excess sludge 1 and in treated water 8 (12.3%). These results demonstrate a prevalence of L. monocytogenes and S. aureus in waste waters from dairies. During the cleaning process pathogenic bacteria were not devitalized. The excess sludge and treated water including pathogenic micro-organisms represent a potential health hazard.
12
Choi, Y. G., H. S. Kim, Y. H. Park, S. H. Jeong, D. H. Son, Y. K. Oh i I. T. Yeom. "Improvement of the thickening and dewatering characteristics of activated sludge by electroflotation (EF)". Water Science and Technology 52, nr 10-11 (1.11.2005): 219–26. http://dx.doi.org/10.2166/wst.2005.0697.
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The performances of electroflotation (EF) on the thickening of activated sludge were investigated using laboratory scale batch flotation reactors. Four activated sludges including bulking sludges were tested. After 30minutes of EF operation, 57–84% of sludge volume reduction could be achieved by EF, while only about 1.5–14% could be obtained by gravity thickening for the same period. After thickening the effluent water quality in terms of TCOD, SS, and turbidity was improved by EF operation for all sludge samples. In addition, the EF thickened sludge showed much better dewaterability both in SRF and cake solid content. It is induced that the air bubbles entrapped in the thickened sludge play a key role in the observed dewaterbility improvement.
13
Yigit, Nevzat O., Gokhan Civelekoglu, Ozer Cinar i Mehmet Kitis. "Filterability of membrane bioreactor (MBR) sludge: impacts of polyelectrolytes and mixing with conventional activated sludge". Water Science and Technology 61, nr 3 (1.02.2010): 659–69. http://dx.doi.org/10.2166/wst.2010.869.
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The main objective of this work was to investigate the filterability of MBR sludge and its mixture with conventional activated sludge (CAS). In addition, the impacts of type and dose of various polyelectrolytes, filter type and sludge properties on the filterability of both MBR and Mixed sludges were determined. Specific cake resistance (SCR) measured by the Buchner funnel filtration test apparatus and the solids content of the resulting sludge cake were used to assess the dewaterability of tested sludges. The type of filter paper used in Buchner tests affected the results of filterability for MBR, CAS and Mixed sludges. SCR values and optimum polyelectrolyte doses increased with increasing MLSS concentrations in the MBR, which suggested that increase in MLSS concentrations accompanied by increases in EPS and SMP concentrations and a shift toward smaller particles caused poorer dewaterability of the MBR sludge. The significant differences observed among the filterability of CAS and MBR sludges suggested that MLSS alone is not a good predictor of sludge dewaterability. Combining CAS and MBR sludges at different proportions generally improved their dewaterability. Combining MBR sludges having typically high MLSS and EPS concentrations with CAS having much lower MLSS concentrations may be an option for full-scale treatment plants experiencing sludge dewaterability problems. Better filterability and higher cake dry solids were achieved with cationic polyelectrolytes compared to anionic and non-ionic ones for all sludge types tested.
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Mustranta, A., i L. Viikari. "Dewatering of Activated Sludge by an Oxidative Treatment". Water Science and Technology 28, nr 1 (1.07.1993): 213–21. http://dx.doi.org/10.2166/wst.1993.0051.
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Different activated sludges from pulp and paper mills were treated with hydrogen peroxide in the presence of ferrous sulphate under different reaction conditions in order to improve the dewatering characteristics of the sludges. The efficiency of the treatment was evaluated on the basis of the specific filtration resistance. Although sludges from different mills varied considerably with respect to their chemical composition and dewatering properties, the specific resistance values of all the sludges could be decreased using rather mild conditions. The filterabilities of the sludges were dependent on reaction temperature, hydrogen peroxide concentration and the reaction time used in the oxidative treatment. Depending on the type of sludge, hydrogen peroxide concentrations of 15 to 30 % mmoles/l sludge were sufficient to decrease the filtration values to a low level at 70°C using a reaction time of 1-2 hours at pH 3.
15
Anderson, B. C., D. S. Mavinic i J. A. Oleszkiewicz. "Stabilization of combined wastewater sludge: anaerobic processes". Canadian Journal of Civil Engineering 22, nr 2 (1.04.1995): 223–34. http://dx.doi.org/10.1139/l95-032.
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Pilot-scale research was conducted to quantify the effects of stabilizing combined wastewater sludges (primary and biological nutrient removal waste activated sludges), in a common high-rate, single-stage anaerobic digestion operation. Various ratios of primary to waste activated sludge were used, and digester operational efficiency was assessed on the basis of the amount and rate of volatile mass removal, biogas production, and digester supernatant quality. It was found that, depending on the sludge ratio, addition of the biological nutrient removal waste activated sludge decreased digester operational efficiency; for example, almost 20% less volatile mass reduction, up to 25% reduction in metabolic reaction rates, and reduced gas production rates of up to 40% were observed. This was attributed to the presence of the cell membrane encapsulating the fermentable substrates of waste activated sludge, making them less available in the digestion process. It was concluded that, unless some type of pretreatment operation is utilized to liberate these substrates, this type of commonly used codigestion system will be of less benefit to a wastewater treatment plant, especially the smaller facilities which will lose a ready source of power in the form of biogas production, and the full value of the waste activated sludge as a resource will not be realized. Key words: anaerobic sludge digestion, biogas production, biological nutrient removal, biosolids, combined sludge, fermentation, volatile mass reduction.
16
Bux, F., B. Atkinson i H. C. Kasan. "Zinc biosorption by waste activated and digested sludges". Water Science and Technology 39, nr 10-11 (1.05.1999): 127–30. http://dx.doi.org/10.2166/wst.1999.0640.
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Biological matter is known for its ability to biosorb solubilised heavy metal ions to its surface. Experiments were therefore conducted to assess the biosorptive capacity of two waste products of the wastewater treatment industry ie., waste activated and waste digested sludge. Surface charge of each was determined in order to relate electronegativity with biosorptive potential. Activated sludge was found to be more effective than digested sludge for removal of zinc from a metal plating effluent, viz., 5.9 mg Zn/(g sludge)−1 as opposed to 4.0 mg/g, respectively, as well as producing a higher net negative charge. It was also noted that as initial zinc concentrations in solution increased there was a concomitant increase in sludge biosorption capacity. Activated and digested sludges were capable of biosorbing zinc from a metal plating effluent although activated sludge showed better potential for industrial application.
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Lai, J. Y., i J. C. Liu. "Co-conditioning and dewatering of alum sludge and waste activated sludge". Water Science and Technology 50, nr 9 (1.11.2004): 41–48. http://dx.doi.org/10.2166/wst.2004.0530.
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Co-conditioning and dewatering behaviors of alum sludge and waste activated sludge were investigated. Two different sludges were mixed at various ratios (2:1; 1:1; 1:2; 1:4) for study. Capillary suction time (CST) and specific resistance to filtration (SRF) were utilized to assess sludge dewaterability. Relatively speaking, waste activated sludge, though of higher solid content, was more difficult to be dewatered than alum sludge. It was found that sludge dewaterability and settlability became better with increasing fraction of alum sludge in the mixed sludge. Dosage required of the cationic polyelectrolyte (KP-201C) for dewatering was reduced as well. It is proposed that alum sludge acts as skeleton builder in the mixed sludge, and renders the mixed sludge more incompressible which is beneficial for sludge dewatering. Implications of the results of the study to the sludge management plan for Taipei City that generates both alum sludge and waste activated sludge at significant amount are also discussed. The current sludge treatment and disposal plan in Metropolitan Taipei could be made more cost-effective.
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Kageyama, Masao, i Kosuke Tomita. "Activated Sludge Treatment of Wastewater from a Nylon 6 Manufacturing Plant". Water Science and Technology 20, nr 10 (1.10.1988): 49–55. http://dx.doi.org/10.2166/wst.1988.0123.
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The activated sludge treatment of wastewater containing ɛ-caprolactam from a Nylon 6 manufacturing plant was investigated by basic studies and operation of a full-scale treatment plant. Activated sludges were obtained from several municipal and industrial wastewater sources, or were prepared by mixing ɛ-caprolactam-utilizing bacteria (Bacillus sp. and Achromobacter sp.) with a municipal activated sludge. However, bulking phenomena were soon observed in the acclimatization of ordinary activated sludges, even when started from a very low concentration of ɛ-caprolactam. On the other hand, the activated sludge synthesized from ɛ-caprolactam-utilizing bacteria showed better results as regards sludge volume index (SVI), BOD removal, and transparency of treated water. Wastewater from the Nylon 6 manufacturing plant, which contained ɛ-caprolactam, was treated by this synthesized activated sludge in a bench-scale apparatus consisting of a 4 m3 aeration basin and a 1.4 m3 sedimentation basin. The optimum BOD loading was estimated to be 0.35-0.40 kg BOD/kg MLSS/day for this wastewater. Production of excess activated sludge was 10% of the BOD loaded. In 1974, based on this preliminary experiment, a wastewater treatment facility consisting of a 2,500 m3 aeration basin and a 1,250 m3 sedimentation basin was constructed near the Uji Nylon 6 manufacturing plant (Unitika Ltd), to treat 5,000 m3 of wastewater (BOD 300-400 mg/l) per day. The treatment plant operates successfully, producing treated water with a BOD below 10 mg/l.
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Dohányos, Michal, Jana Zábranská i Pavel Jenícek. "Enhancement of sludge anaerobic digestion by using of a special thickening centrifuge". Water Science and Technology 36, nr 11 (1.12.1997): 145–53. http://dx.doi.org/10.2166/wst.1997.0405.
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The intensification method of anaerobic methane fermentation of sludges, based on the stimulation activity of cell lysate, was studied. The effect of lysate is caused by the still remaining activity of released enzymes and by the stimulating properties of other compounds that are present inside the cells. The use of cell lysate as a stimulating agent was examined in the laboratory experiments of anaerobic degradation of municipal raw sludge, excess activated sludge and a mixture of them. The cell lysate was prepared by a partial mechanical destruction of cells of the excess activated sludge by a special adapted thickening centrifuge. The presence of aerobic cell lysate in thickened excess activated sludge causes a substantial increment in the methane yield and the biodegradability of thickened activated sludge in comparison with untreated excess sludge. The improvement of methane yield and biodegradability is influenced by the quality of input excess activated sludge and the parameters and efficiency of the thickening centrifuge. The improvement of methane yield from thickened activated sludge ranged from 8.1 to 86.4% dependent on the sludge quality. The improvement of methane yield from the mixture of thickened activated sludge and primary sludge ranged from 0 to 24%, and it was predominantly dependent on the fluctuating quality of primary sludge. The advantages of the stimulation method with the cell lysate are the following: the improvement of the anaerobic biodegradability of organic materials treated, the acceleration of the degradation process, the increment of methane production, the lowering of digested sludge amount and the improvement of the energetic balance of the process.
20
Kahru, A., M. Kurvet i I. Külm. "Toxicity of phenolic wastewater to luminescent bacteria photobacterium phosphoreum and activated sludges". Water Science and Technology 33, nr 6 (1.03.1996): 139–46. http://dx.doi.org/10.2166/wst.1996.0090.
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Ash-heap water (AHW - phenolic wastewater of local oil-shale industry) was analyzed for its phenolic composition using HPLC and for its relative toxicity using MicrotoxTM and BiotoxTM tests where inhibition of natural luminescence of photobacteria is used as toxicity endpoint. Most abundant components in AHW were phenol (84 mg/L) and p-cresol (70 mg/L). The 5-min EC50 values for AHW (the concentration of AHW, %, which reduces the light output of bacteria by 50% after being in contact with bacteria for 5 minutes) for BiotoxTM and MicrotoxTM tests were 1.5% and 0.6%, respectively. Also, the toxicity of AHW towards two different activated sludges (acclimatized and not acclimatized to phenolic wastewater) was evaluated using decrease of adenosine triphosphate (ATP) content of the sludge as toxicity endpoint. AHW was relatively non-toxic to activated sludges, especially to the acclimatized sludge. The respective 60-min EC50 value for AHW (the concentration of AHW, %, which decreases the ATP level of activated sludge compared to the non-exposed control by 50% after being in contact with sludge for 60 minutes) was 20-30% for non acclimatized sludge and 50-60% for acclimatized sludge. Therefore, the biopurification of AHW using an adapted activated sludge process could be considered feasible.
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Hanada, S., H. Satoh i T. Mino. "Measurement of microorganisms with PHA production capability in activated sludge and its implication in Activated Sludge Model No. 3". Water Science and Technology 45, nr 6 (1.03.2002): 107–13. http://dx.doi.org/10.2166/wst.2002.0098.
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In Activated Sludge Model No.3 (ASM3), it is hypothesized that all heterotrophic microorganisms (XH) can store substrate. However, in reality, both microorganisms with and without substrate storage capability (XH/STO and XH/S, respectively) could exist. If the ratio of XH/STO in activated sludge is influenced by operational and environmental conditions, kSTO (storage rate constant of heterotrophic microorganisms which is defined in ASM3) may not be a universal parameter and can change from case to case. In this study, polyhydroxyalkanoate (PHA) is assumed as the principal storage product, and the ratio of microorganisms with PHA production capability (XH/PHA) in various activated sludges was estimated by the dual staining of Nile Blue A (NB) and DAPI. It was shown that the ratio of XH/PHA in sludge varied among different municipal and laboratory activated sludges.
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Rio, S., C. Faur-Brasquet, L. Le Coq, D. Lecomte i P. Le Cloirec. "Preparation and characterization of activated carbon from sewage sludge: carbonization step". Water Science and Technology 49, nr 1 (1.01.2004): 139–46. http://dx.doi.org/10.2166/wst.2004.0041.
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Sewage sludges produced from wastewater treatment plants continue to create environmental problems in terms of volume and method of valorization. Thermal treatment of sewage sludge is considered as an attractive method in reducing sludge volume which at the same time produces reusable by-products. This paper deals with the first step of activated carbon production from sewage sludge, the carbonization step. Experiments are carried out on viscous liquid sludge and limed sludge by varying carbonization temperature and heating rate. The results show that carbonized residue properties are interesting for activated carbon production.
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Sparling, Arthur B., i David L. Woytowich. "A new concept of upflow clarification in activated sludge separation". Canadian Journal of Civil Engineering 13, nr 5 (1.10.1986): 517–22. http://dx.doi.org/10.1139/l86-078.
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An experimental investigation was conducted to evaluate a new concept of upflow clarification. A novel sludge removal mechanism that used the entire floor area for the removal of solids was incorporated in an upflow clarifier. The operating characteristics and design features of the continuous flux upflow clarifier (CFLUC) are described in detail. The laboratory study was conducted to determine the effectiveness of the CFLUC clarifier in separating sludges with different settling characteristics. The different sludge types were produced by an activated sludge system treating a synthetic dairy waste at four different food to microorganism (F: M) ratios. At low organic loadings (0.10–0.24 (g COD)(g MLVSS)−1 (d)−1), the CFLUC clarifier removed 70% of the pinpoint floe that remained during quiescent batch settling conditions. At high organic loadings (0.41–0.83 (g COD)(g MLVSS) −1 (d) −1), the CFLUC clarifier was capable of separating filamentous bulking sludges with poor settling characteristics. Based on the results of the experimental study the upflow clarifier effectively separated all sludge types over the range of organic loadings investigated. Key words: CFLUC clarifier, secondary clarification, upflow clarification, sludge blanket, bioflocculation, bulking sludge, gravity sedimentation.
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Dokulilová, Tereza, Tomáš Vítěz, Jan Chovanec, Robert Rouš, Monika Vítězová i Ivan Kushkevych. "Primary and Activated Sludge Biogas Production: Effect of Temperature". Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 66, nr 1 (2018): 23–28. http://dx.doi.org/10.11118/actaun201866010023.
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Sewage sludge management is a problem of growing importance. Anaerobic sewage sludge stabilization is commonly used technology, where organic matter contained in primary and activated sewage sludge is converted into biogas, so both, pollution control and energy recovery can be achieved. The paper deals with the effect of process temperature (36 °C, 42 °C and 50 °C) on biogas production and quality during anaerobic stabilization of primary and activated sewage sludge generated during purifying process in low‑loaded activated sludge process. Primary and activated sewage sludge samples were taken at the wastewater treatment plant Brno, Czech Republic. The characteristics of sludges (dry matter and organic dry matter content, pH, conductivity, redox potential) were dermined. Biogas production and quality was measured using 3 anaerobic systems, each of 8 batch anaerobic fermenters, at the 3 different temperature conditions 36 °C, 42 °C and 50 °C. Hydraulic retention time was 20 days. Hypothesis, which predicts that the fermentation of primary and activated sludge provides dissimilar methane quantity and quality under different temperature conditions (36 °C, 42 °C and 50 °C), was partially confirmed. Temperature 42 °C significantly increased biogas production from primary sewage sludge (by 60 % in comparison with production at 36 °C). For activated sewage sludge samples no significant influence of temperature on the biogas production was observed.
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Matsui, Y., F. Yamaguchi, Y. Suwa i Y. Urushigawa. "Growth Characteristics of Activated Sludges Acclimated to para-Nitrophenol in Batch and Continuous Modes". Water Science and Technology 29, nr 7 (1.04.1994): 327–33. http://dx.doi.org/10.2166/wst.1994.0359.
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Activated sludges were acclimated to p-nitrophenol (PNP) in two operational modes, a batch and a continuous. The operational mode of the PNP acclimation of activated sludges strongly affected the physiological characteristics of predominant microorganisms responsible for PNP degradation. Predominant PNP degraders in the sludge in batch mode (Sludge B) had lower PNP affinity and were relatively insensitive to PNP concentration. Those of the sludge in continuous mode (Sludge C), on the other hand, had very high PNP affinity and were sensitive to PNP. MPN enumeration of PNP degraders in sludge B and C using media with different PNP concentrations (0.05, 0.2,0.5 and 2.0 mM) supported the above results. Medium with 0.2 mM of PNP did not recover PNP degraders in sludge C well, while it recovered PNP degraders in sludge B as well as the medium with 0.05 mM did. When switching from one operational mode to the other, the predominant population in sludge B shifted to the sensitive group, but that of sludge C did not shift at the given loading of PNP, showing relative resistance to inhibitive concentration.
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Jönsson, K., E. Aspichueta, A. de la Sota i J. la C Jansen. "Evaluation of nitrification-inhibition measurements". Water Science and Technology 43, nr 1 (1.01.2001): 201–8. http://dx.doi.org/10.2166/wst.2001.0049.
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A screening method for nitrification-inhibition determination has been evaluated at two laboratories, one in Sweden and one in Spain. Allylthiourea (ATU), methanol, chromium and zinc were used as reference toxicants in combination with different kinds of full-scale sludge and sludge produced in the laboratory. Different results were obtained with different combinations of activated sludge and toxicants. It was found that activated sludge often exposed to small amounts of a variety of toxic substances may build up a general resistance to toxic substances. Specific adaptation to certain substances was also observed. Domestic activated sludge responded in the same way to ATU regardless of whether it originated from Sweden or Spain. Synthetic sludge and domestic sludge exhibited the same inhibition of nitrification when tested with ATU as a toxicant. Synthetic activated sludge from two laboratory-scale plants run in parallel did not exhibit exactly the same sensitivity to certain toxicants. The variation in repeated tests with the synthetic sludges was about the same as for repeated tests with full-scale sludge and for other biological toxicity tests. Limits of detection were calculated to be about 5% for a single sample with three blanks as references at both the laboratories.
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Daigger, Glen T., Eric Redmond i Leon Downing. "Enhanced settling in activated sludge: design and operation considerations". Water Science and Technology 78, nr 2 (26.06.2018): 247–58. http://dx.doi.org/10.2166/wst.2018.287.
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Abstract Settling of activated sludge particles has long been the key to successfully achieving secondary treatment. While soluble products can be converted to particulate components via microbial reactions in the activated sludge process, it is the subsequent removal of these particulate components that is the key to achieving ultimate water quality criteria. An understanding of the operating parameters for selecting good settling activated sludge particles was first documented in the 1970s and 1980s. An understanding of the growth pressures that can be imposed on filamentous organisms, and the impacts of selector zones in general, allowed the design and operation of activated sludge processes to routinely achieve good sludge settleability. More recently, research has identified what could be the next evolution in flocculant growth, with the growing interest in aerobic granular sludge. Aerobic granular sludge is purported to provide superior settling properties, and many of the growth pressures identified for aerobic granular sludge are also present in activated sludge systems. These enhanced settling sludge systems are gaining significant interest, but the factors leading to enhanced sludge settleability could be present in historical and existing systems. Three facilities were evaluated that exhibited enhanced settleability (i.e. sludge volume indices of less than 70 mL/g the majority of the time) to determine how these enhanced settling sludges compare to typical settling curves from the literature. The enhanced settling sludge facilities exhibit key differences related to surface overflow rate, return activated sludge (RAS) pumping requirements, and sensitivity to solids concentration that are critical for developing effective settling designs for enhanced settling sludge facilities. As more facilities aim to achieve enhanced settling sludge for intensification of infrastructure, it will be important to carefully consider historic settling curves and to develop site-specific settling criteria when possible.
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Hagland, Eva, Åsa Dillner Westlund i Maria Rothman. "Sludge retention time in the secondary clarifier effects on the growth of Microthrix parvicella". Water Science and Technology 37, nr 4-5 (1.02.1998): 47–50. http://dx.doi.org/10.2166/wst.1998.0578.
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Microbiological examinations have been performed over the last 3 years at 3 large sewage treatment plants in the greater Stockholm area. All 3 plants have periodically suffered from excessive growth of the filamentous bacterium Microthrix parvicella. The growth of Microthrix parvicella was favored by low sludge loading. Results from various plants and from the various parallel systems within the individual plants were compared. The bacterial composition of the activated sludges differed in ways that could not be explained by the sludge loading or the sewage composition. Biological processes in the secondary clarifiers seem to influence the competition between the different organisms in the activated sludge. A clear relationship was shown between high sludge retention time in the secondary clarifiers, VFA production in the return activated sludge (RAS) and a high abundance of Microthrix parvicella.
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Hardy, P., J. E. Burgess, S. Morton i R. M. Stuetz. "Simultaneous activated sludge wastewater treatment and odour control". Water Science and Technology 44, nr 9 (1.11.2001): 189–96. http://dx.doi.org/10.2166/wst.2001.0537.
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Lab-scale tests were used to determine the amount of H2S that can be treated using a range of different activated sludges. Static vessels were used to study the effects of different H2S concentrations (5, 25, 50 and 75 ppm). The data indicated that odour control may be carried out using certain types of sludge, but sludge type, e.g. carbonaceous, nitrifying, with or without coagulant, affects removal efficiency. The presence of the biomass resulted in greater H2S removal than the use of wet scrubbing and the adverse effects on mixed liquor were negligible. A pilot plant was used to study the removal efficiencies of activated sludge diffusion using a typical wastewater treatment plant H2S concentration and investigated the effects that the diffusion of H2S had on the process performance. Results indicated that the levels of H2S produced by other unit processes on a wastewater treatment site (approximately 5 ppm) can be treated using activated sludge diffusion without compromising the performance of the wastewater treatment process. The only effects on the activated sludge plant observed were: (1) nitrification was interrupted briefly as H2S diffusion commenced and (2) the species' diversity in the sludge decreased.
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Oosthuizen, D. J., i T. E. Cloete. "SEM-EDS for determining the phosphorus content in activated sludge EPS". Water Science and Technology 43, nr 6 (1.03.2001): 105–12. http://dx.doi.org/10.2166/wst.2001.0351.
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Not all phosphorus removed in activated sludge systems can be accounted for by polyphosphate accumulating organisms (PAO). A method for the qualitative and quantitative in situ characterization of PAO cell clusters and closely associated extracellular polysaccharides (EPS) is described. X-ray microanalysis was performed on samples from four activated sludge plants situated in Pretoria, South Africa. Analyses were done by means of Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectrometry (EDS). Cell clusters with associated EPS on average contained between 57 and 59% phosphorus, while EPS alone contained on average between 23 and 30% phosphorus. Results suggest that phosphorus removal in activated sludge might be due not only to PAO, but also by EPS acting as a phosphorus reservoir. Extraction of EPS from two different activated sludge plants yielded different amounts of EPS, which, in combination with SEM-EDS, may shed light on different phosphate uptake abilities of different activated sludges.
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Urbain, V., J. C. Block i J. Manem. "Bioflocculation in Activated Sludge, an Analytic Approach". Water Science and Technology 25, nr 4-5 (1.02.1992): 441–43. http://dx.doi.org/10.2166/wst.1992.0531.
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A study on the physico-chemical structure of activated sludge flocs was carried out to get a better insight in its relation with sludge settleability. For this purpose, sixteen sludges from different origins were analysed in order to provide information with regard to their settleability, biomass and exocellular composition, surface characteristics and internal hydrophobicity. The presence of filamentous micro-organisms was observed in all samples but was not always associated with poor settleability, supporting to some extent the idea of their role as a backbone in the flocs. The relations between variables were studied through their linear correlations. Exocellular polymers (ECP) were associated with poor settling conditions. The chemical composition of the ECP (the DNA fraction and the C/N ratio) had an influence on the surface characteristics of the flocs. Finally, sludge settleability was described with a mathematical model, opposing the ECP and the internal hydrophobicity of the flocs. The positive role of hydrophobic interactions, in term of settleability, should provide a new approach in the understanding of flocculation mechanisms in activated sludge.
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Barbusinski, K., i H. Koscielniak. "Activated sludge floc structure during aerobic digestion". Water Science and Technology 36, nr 11 (1.12.1997): 107–14. http://dx.doi.org/10.2166/wst.1997.0400.
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Additional observations of the physical characteristics have been introduced to current monitoring of aerobic digestion of sludges coming from two wastewater treatment plants. New parameters have included determination of floc size and sludge specific surface. The internal floc structure was also examined with the use of microtome technique for slicing flocs into very thin sections. During aeration, considerable changes in floc dispersion occurred. Analysis of floc size distribution enables observation of regroupment of different sludge fractions and successive increase in frequency occurrence of the finest fractions, which usually hinder dewatering process. The decrease of average floc size has been accompanied by the increase in sludge specific surface. The time needed for “biological stabilization” has not occurred simultaneously with the time when physical parameters have been shaped in the best possible manner for further sludge treatment. The joint analysis of biochemical and physical properties including above mentioned parameters has enabled the assignment of aerobic digestion time more precisely. It has special meaning in pre-designing research as well as during the start-up of the aerobic digestion systems.
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Yangin Gomec, C., i R. E. Speece. "The role of pH in the organic material solubilization of domestic sludge in anaerobic digestion". Water Science and Technology 48, nr 3 (1.08.2003): 143–50. http://dx.doi.org/10.2166/wst.2003.0185.
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The effect of pH on anaerobic solubilization of domestic primary sludge and activated sludge was investigated and compared. Anaerobic solubilization was carried out in continuously stirred anaerobic reactors at mesophilic temperature (35°C) and pH was fixed at 6.5 (pH-controlled). Many researches reported the serious effects of pH on the solubilization of organic materials. Thus, the aim of pH control in the reactors consisting of domestic primary and activated sludges, was the evaluation of retardation in hydrolysis/acidogenesis at low pH values. Since primary and activated sludges have different biodegradation characteristics, results were compared. Results indicated that the destruction of Total Suspended Solids (TSS) and Volatile Suspended Solids (VSS) were better in the pH-controlled reactors. In both sludges, acetic acid was the main Volatile Fatty Acid (VFA) produced. In the pH-controlled reactors, VSS reduction was found to be 72% in about 20 days in the anaerobic digestion of activated sludge, whereas for the same interval VSS reduction could only be achieved by 32% in primary sludge at 35°C. When primary sludge was used as substrate, the pH-uncontrolled and the pH-controlled reactors removed VSS with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). However, production of VFAs and SCOD was ceased after 5 days in the pH-controlled reactor whereas VFAs and SCOD production continued after 5 days in the pH-uncontrolled reactor, which indicated that hydrolysis and fermentation did not complete and continued longer. On the other hand; in either the pH-uncontrolled or the pH-controlled reactor of activated sludge, VSS was not removed with a corresponding production of VFAs and Soluble Chemical Oxygen Demand (SCOD). It was apparent that solubilization was occurring, however this solubilization was not observed as VFA production. When total methane production and total COD (CODtot) removal were estimated using VSS removal in both types of sludges, results indicated that pH control enhanced biogas productions as well as CODtot removals.
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Kosaric, N., i Z. Duvnjak. "Deemulsification of Water-in-Oil Emulsion with Sludges". Water Quality Research Journal 22, nr 3 (1.08.1987): 437–43. http://dx.doi.org/10.2166/wqrj.1987.034.
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Abstract Aerobic sludge from a municipal activated sludge treatment plant, sludge from a conventional municipal anaerobic digester, aerobic sludge from an activated sludge process of a petroleum refinery, and granular sludge from an upflow sludge blanket reactor (USBR) were tested in the deemulsification of a water-in-oil emulsion. All sludges except the last one, showed a good deemulsification capability and could he used for a partial deemulsification of such emulsions. The rate and degree of the deemulsifications increased with an increase in sludge concentrations. The deemulsifications were faster at 85°C and required smaller amounts of sludge than in the case of the deemulsifications at room temperature. An extended stirring (up to a certain limit) in the course of the dispersion of sludge emulsion helped the deemulsification. Too vigorous agitation had an adverse effect. The deemulsification effect of sludge became less visible with an increase in the dilution of emulsion which caused an increase in its spontaneous deemulsification.
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Dohányos, Michal, Jana Zábranská i Pavel Jenícek. "Innovative technology for the improvement of the anaerobic methane fermentation". Water Science and Technology 36, nr 6-7 (1.09.1997): 333–40. http://dx.doi.org/10.2166/wst.1997.0608.
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The intensification method of anaerobic methane fermentation of sludges, based on the stimulation activity of cell lysate, was studied. The effect of lysate is caused by the still remaining activity of released enzymes and by the stimulating properties of other compounds that are present inside the cells. The anaerobic cell lysate was prepared by a thermal treatment of anaerobic sludge and the aerobic cell lysate by a partial mechanical destruction of cells of the excess activated sludge by a special adapted thickening centrifuge. The use of cell lysate as a stimulating agent was examined in the laboratory experiments of anaerobic degradation of simple organic compounds (glucose, acetate, formate and propionate) and of complex substrates as municipal raw sludge, excess activated sludge and some pharmaceutical organic wastes. The results show a significant improvement of the removal rates of substrates and the enhancement of methane production in all cases of lysate addition. In the fermentation of raw sludges and pharmaceutical wastes with anaerobic lysate, the increment of the methane yield ranges from 38.2–61.8% and 20.2–36.7% respectively. The aerobic lysate increased the methane yield of excess activated sludge and of its mixture with primary sludge at the range of 17.1–86.4% and 24% respectively.
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Hua-Wu, Liu, Steven N. Liss i D. Grant Allen. "The influence of anoxic conditioning of sludge on enhanced AOX (adsorbable organic halogen) removal in aerobic biological treatment systems". Water Science and Technology 35, nr 2-3 (1.02.1997): 77–84. http://dx.doi.org/10.2166/wst.1997.0487.
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The increasingly stringent limits on the discharge of adsorbable organic halogen (AOX) from bleached kraft pulp mills have resulted in a need to optimize the performance of biological wastewater treatment systems with respect to the removal of these compounds. To investigate whether anoxic conditioning of sludge can enhance AOX removal in activated sludge systems, a series of batch experiments was conducted where reactors were seeded with various proportions of activated and anoxic-conditioned sludges. AOX removal was found to be significantly enhanced through the addition of anoxic-conditioned sludge to activated sludge, resulting in overall AOX removal of up to 75%. The extent of enhancement ranged from 3 to approximately 10% as the conditioning time was increased from 5 to 20 days. The benefit then declined as the conditioning times increased further beyond 20 days and up to 30 days. The effect of conditioning time on COD removal followed a similar trend as for AOX removal. An optimal AOX removal was achieved when the proportion of conditioned sludge within the biomass was 30%. A good correlation between the enhanced AOX removal and increasing levels of facultative bacteria developed in the conditioned sludge was observed. The addition of sulphate into the sludge during conditioning further increased the enhancement of AOX removal when compared to sludges conditioned under nitrogen.
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Hilligardt, Dieter, i Erhard Hoffmann. "Particle size analysis and sedimentation properties of activated sludge flocs". Water Science and Technology 36, nr 4 (1.08.1997): 167–75. http://dx.doi.org/10.2166/wst.1997.0112.
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Activated sludge is one of the best investigated and understood suspensions. But up to now we still lack the factors influencing the sedimentation velocities concerning the main sludge characteristics/properties to describe the settleability of different sludges. Different in terms of SVI, organic loading, sludge retention time, composition, content of polymers, iron or aluminium, density, porosity and particle size distribution. But for the design of clarifiers most of these parameters are disregarded, of none importance or neglectable. With the help of PSD and particle shape analysis we can improve our knowledge of the settleability of activated sludge flocs. The measurements, done with the CIS show the influence of the differential sedimentation in comparison to the effluent of the secondary clarifiers under different conditions. Calculating the sedimentation velocities, the behaviour of activated and precipitated sludge could be explained and conclusions can be drawn to optimize the solid flux in secondary clarifiers.
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He, Li, i Hui Pan. "Toxic Effects of Phenol on OUR in Activated Sludge". Advanced Materials Research 955-959 (czerwiec 2014): 2065–69. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.2065.
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Toxic effects of phenol on the activated sludge process were evaluated by determining the changes in DO in a laboratory-scale unit. A series of phenol concentration significantly affected the activated sludge. The effect of phenol was variable depending on its concentration. With the increase of phenol concentration, oxygen uptake rate (OUR) decreased. The inhibitory concentration that reduced the sludges specific oxygen uptake 50% from its maximum rate was determined (IC50).
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Hiraishi, Akira, Yoko Ueda i Junko Ishihara. "Quinone Profiling of Bacterial Communities in Natural and Synthetic Sewage Activated Sludge for Enhanced Phosphate Removal". Applied and Environmental Microbiology 64, nr 3 (1.03.1998): 992–98. http://dx.doi.org/10.1128/aem.64.3.992-998.1998.
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ABSTRACT Respiratory quinones were used as biomarkers to study bacterial community structures in activated sludge reactors used for enhanced biological phosphate removal (EBPR). We compared the quinone profiles of EBPR sludges and standard sludges, of natural sewage and synthetic sewage, and of plant scale and laboratory scale systems. Ubiquinone (Q) and menaquinone (MK) components were detected in all sludges tested at molar MK/Q ratios of 0.455 to 0.981. The differences in MK/Q ratios were much larger when we compared different wastewater sludges (i.e., raw sewage and synthetic sewage) than when we compared sludges from the EBPR and standard processes or plant scale and laboratory scale systems. In all sludges tested a Q with eight isoprene units (Q-8) was the most abundant quinone. In the MK fraction, either tetrahydrogenated MK-8 or MK-7 was the predominant type, and there was also a significant proportion of MK-6 to MK-8 in most cases. A numerical cluster analysis of the profiles showed that the sludges tested fell into two major clusters; one included all raw sewage sludges, and the other consisted of all synthetic sewage sludges, independent of the operational mode and scale of the reactors and the phosphate accumulation. These data suggested that Q-8-containing species belonging to the classProteobacteria (i.e., species belonging to the beta subclass) were the major constituents of the bacterial populations in the EBPR sludge, as well as in standard activated sludge. Members of the class Actinobacteria (gram-positive bacteria with high DNA G+C contents) were the second most abundant group in both types of sludge. The bacterial community structures in activated sludge processes may be affected more by the nature of the influent wastewater than by the introduction of an anaerobic stage into the process or by the scale of the reactors.
40
Wanner, Jiri. "Activated sludge population dynamics". Water Science and Technology 30, nr 11 (1.12.1994): 159–69. http://dx.doi.org/10.2166/wst.1994.0556.
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The paper briefly surveys topics covered by the IAWQ Specialist Group on Activated Sludge Population Dynamics. The activated sludge population dynamics has been formulated as a branch of water science and technology concerned with phenomena governing the relationships between activated sludge microorganisms and their functions. The characterization of organic pollution fractions in wastewaters according to their rate of biodegradation has been discussed and the role of wastewater as an inoculum stressed. The characterization of activated sludge biomass has been evaluated from two viewpoints: grouping according to metabolic abilities and identification and classification of activated sludge microorganisms. The basic selection mechanisms influencing the microbial composition of activated sludge have been described. The problems with activated sludge settling and thickening properties have been mentioned as a typical example of applied population dynamics research.
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Zarnovsky, L., J. Derco, R. Kuffa i M. Drtil. "The influence of cadmium on activated sludge activity". Water Science and Technology 30, nr 11 (1.12.1994): 235–42. http://dx.doi.org/10.2166/wst.1994.0564.
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The influence of solid retention time, cadmium loading and the effect of the process of acclimation on the activity of activated sludge in the presence of the metal were studied. Activated sludge was cultivated in plug-flow and continuous completely mixed lab-scale bioreactors. Respirometric measurements were applied to evaluate the inhibition effects of cadmium on activated sludge. Monod's equation and the equation of non-competitive inhibition were applied to describe the toxicity and inhibition of cadmium. Maximum inhibition effect of cadmium was observed at different time periods of cadmium acting on both acclimated and non-acclimated sludges. The dependence of the attainment of maximum inhibition effect on the metal loading as well as solid retention time was observed. Therefore, maximum inhibition should be included in the assessment of metal toxicity.
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Namazi, A. B., C. Q. Jia i D. G. Allen. "Production and characterization of lignocellulosic biomass-derived activated carbon". Water Science and Technology 62, nr 11 (1.12.2010): 2637–46. http://dx.doi.org/10.2166/wst.2010.981.
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The goal of this work is to establish the technical feasibility of producing activated carbon from pulp mill sludges. KOH chemical activation of four lignocellulosic biomass materials, two sludges from pulp mills, one sludge for a linerboard mill, and cow manure, were investigated experimentally, with a focus on the effects of KOH/biomass ratio (1/1, 1.5/1 and 2/1), activation temperature (400–600°C) and activation time (1 to 2 h) on the development of porosity. The activation products were characterized for their physical and chemical properties using a surface area analyzer, scanning electron microscopy and Fourier transform infrared spectroscopy. Experiments were carried out to establish the effectiveness of the lignocellulosic biomass-derived activated carbon in removing methylene blue (MB), a surrogate of large organic molecules. The results show that the activated carbon are highly porous with specific surface area greater than 500 m2/g. The yield of activated carbon was greater than the percent of fixed carbon in the dry sludge, suggesting that the activation process was able to capture a substantial amount of carbon from the organic matter in the sludge. While 400°C was too low, 600°C was high enough to sustain a substantial rate of activation for linerboard sludge. The KOH/biomass ratio, activation temperature and time all play important roles in pore development and yield control, allowing optimization of the activation process. MB adsorption followed a Langmuir isotherm for all four activated carbon, although the adsorption capacity of NK-primary sludge-derived activated carbon was considerably lower than the rest, consistent with its lower specific surface area.
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Park, C., i R. F. Helm. "Application of metaproteomic analysis for studying extracellular polymeric substances (EPS) in activated sludge flocs and their fate in sludge digestion". Water Science and Technology 57, nr 12 (1.06.2008): 2009–15. http://dx.doi.org/10.2166/wst.2008.620.
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Metaproteomic analysis, comprising protein separation and identification, was applied to study extracellular proteins in activated sludges and to track their fate in sludge digestion under both anaerobic and aerobic conditions. The complex sludge proteins were first separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and further analysed by liquid chromatography tandem mass spectrometry (LC-MS/MS) to search their identification. Base extraction and cation exchange resin (CER) method were used to extract EPS from sludges at 0, 12 and 30 days of batch digestion. Several important observations were made during this study. Firstly, protein bands were well separated by extraction/SDS-PAGE protocol used in this study. Secondly, numerous protein bands remained after digestion, indicating that these proteins are not easily degradable in sludge digestion. Thirdly, protein bands detected following anaerobic and aerobic digestion differed, suggesting that proteins degraded in two different digestion environments are not the same. Finally, protein bands that emerged distinctively following anaerobic digestion was found to be subunits of methyl-coenzyme M reductase, the enzyme involved in methane generation, in Methanosarcina barkeri. These results demonstrated that metaproteomic investigation on activated sludge EPS is useful for studying floc formation in activated sludges and their degradation in various digestion environments.
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McMahon, Katherine D., Michael A. Dojka, Norman R. Pace, David Jenkins i Jay D. Keasling. "Polyphosphate Kinase from Activated Sludge Performing Enhanced Biological Phosphorus Removal". Applied and Environmental Microbiology 68, nr 10 (październik 2002): 4971–78. http://dx.doi.org/10.1128/aem.68.10.4971-4978.2002.
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ABSTRACT A novel polyphosphate kinase (PPK) was retrieved from an uncultivated organism in activated sludge carrying out enhanced biological phosphorus removal (EBPR). Acetate-fed laboratory-scale sequencing batch reactors were used to maintain sludge with a high phosphorus content (approximately 11% of the biomass). PCR-based clone libraries of small subunit rRNA genes and fluorescent in situ hybridization (FISH) were used to verify that the sludge was enriched in Rhodocyclus-like β-Proteobacteria known to be associated with sludges carrying out EBPR. These organisms comprised approximately 80% of total bacteria in the sludge, as assessed by FISH. Degenerate PCR primers were designed to retrieve fragments of putative ppk genes from a pure culture of Rhodocyclus tenuis and from organisms in the sludge. Four novel ppk homologs were found in the sludge, and two of these (types I and II) shared a high degree of amino acid similarity with R. tenuis PPK (86 and 87% similarity, respectively). Dot blot analysis of total RNA extracted from sludge demonstrated that the Type I ppk mRNA was present, indicating that this gene is expressed during EBPR. Inverse PCR was used to obtain the full Type I sequence from sludge DNA, and a full-length PPK was cloned, overexpressed, and purified to near homogeneity. The purified PPK has a specific activity comparable to that of other PPKs, has a requirement for Mg2+, and does not appear to operate in reverse. PPK activity was found mainly in the particulate fraction of lysed sludge microorganisms.
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Kyllönen, H., J. Lehto, P. Pirkonen, A. Grönroos, H. Pakkanen i R. Alén. "Correlation of wood-based components and dewatering properties of waste activated sludge from pulp and paper industry". Water Science and Technology 62, nr 2 (1.07.2010): 387–93. http://dx.doi.org/10.2166/wst.2010.273.
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Large amounts of wet sludge are produced annually in municipal and industrial wastewater treatment. Already in pulp and paper industry, more than ten million tons of primary sludge, waste activated sludge, and de-inking sludge is generated. Waste activated sludge contains large quantities of bound water, which is difficult to dewater. Low water content would be a matter of high calorific value in incineration but it also has effects on the volume and the quality of the matter to be handled in sludge disposal. In this research waste activated sludges from different pulp and paper mills were chemically characterised and dewatered. Correlations of chemical composition and dewatering properties were determined using multivariate analysis. Chemical characterisation included basic sludge analysis, elementary analysis and analysis of wood-based components, such as hemicelluloses and lignin-derived material. Dewatering properties were determined using measurements of dry solids content, flux and flocculant dosage. The effects of different variables varied according to the response concerned. The variables which were significant regarding cake DS increase in filtration or centrifugation and flocculant dosage needed in filtration were different from those which were significant regarding flux.
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Eriksson, L., i B. Alm. "Study of Flocculation Mechanisms by Observing Effects of a Complexing Agent on Activated Sludge Properties". Water Science and Technology 24, nr 7 (1.10.1991): 21–28. http://dx.doi.org/10.2166/wst.1991.0180.
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Electrostatic interactions between bacterial surfaces, extracellular polymers (ECP) and polyvalent metal ions are important in activated sludge flocculation. An indirect study of these mechanisms was done by adding different concentrations of EDTA to activated sludge samples from 6 Swedish wastewater treatment plants. The effects on sludge properties were studied with sedimentation and filtration tests as well as analysis of released extracellular polymers. EDTA had a significant effect on sedimentation velocity in all investigated sludges. This shows that charged polymers are important for the properties of the floc surfaces and in building up the sludge macroflocs. The effect on filtration resistance where the bulk properties of the primary flocs are more important varied considerably for the different sludges. Thus, both electrostatic and other interactions are involved to a varying extent in building up the primary flocs in the sludges investigated. Variations in sedimentation velocity, residual turbidity, filtration resistance and release of ECP with variations in EDTA concentrations could be explained by effects of polyvalent metal ions on ECP binding and conformation.
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Boehler, M., i H. Siegrist. "Potential of activated sludge ozonation". Water Science and Technology 55, nr 12 (1.06.2007): 181–87. http://dx.doi.org/10.2166/wst.2007.407.
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The disposal of sewage sludge and the agricultural use of stabilised sludge are decreasing due to more stringent regulations in Europe. An increasing fraction of sewage sludge must therefore be dewatered, dried, incinerated and the ashes disposed of in landfills. These processes are cost-intensive and also lead to the loss of the valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Partial ozonation of the return sludge of an activated sludge system significantly reduces excess sludge production, improves the settling properties of the sludge and reduces bulking and scumming. The solubilised COD will also improve denitrification if the treated sludge is recycled to the anoxic zone. However, ozonation partly kills nitrifiers and could therefore lead to a decrease of the effective solid retention time of the nitrifier, thus reducing the safety of the nitrification. This paper discusses the effect of ozonation on sludge reduction, the operating stability of nitrification, the improvement of denitrification and also presents an energy and cost evaluation.
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Samson, K. A., i G. A. Ekama. "An assessment of sewage sludge stability with a specific oxygen utilization rate (SOUR) test method". Water Science and Technology 42, nr 9 (1.11.2000): 37–40. http://dx.doi.org/10.2166/wst.2000.0165.
Pełny tekst źródłaStreszczenie:
Sewage sludge treatment systems are intended to stabilize the sludge so that its disposal or reuse can be environmentally acceptable. However, stabilized sludges may still contain residual biodegradable organic matter that can be environmentally a nuisance. This paper presents a specific oxygen utilization rate [SOUR, mgO2/(gVSS·h)] batch reactor test method to quantify the residual biodegradable organic matter content of the treated (stabilized) sewage sludges. The results of the study, in which 37 SOUR batch tests were done on 10 different sewage sludges, show that the SOUR, when determined over a prolonged period (4 to 5 days), gives an indirect measure of sludge stability defined as the % soluble and particulate residual biodegradable organics in the sludge; to determine % sludge stability, it is necessary to simulate the experimental SOUR data by means of a general activated sludge model. The % sludge stability obtained for the 10 different sludges, taking due account of their soluble and particulate constituents, was consistent with that expected from the stabilization treatment systems to which the sludges were subjected.
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Comeau, Yves, Kenneth J. Hall i William K. Oldham. "Indirect Polyphosphate Quantification in Activated Sludge". Water Quality Research Journal 25, nr 2 (1.05.1990): 161–74. http://dx.doi.org/10.2166/wqrj.1990.009.
Pełny tekst źródłaStreszczenie:
Abstract An indirect biological method is presented to quantify the amount of polyphosphates in activated sludge obtained from wastewater treatment plants removing phosphate biologically. The method is based upon the property of such sludges to degrade polyphosphate reserves under anaerobic conditions as a result of acetate addition thereby releasing inorganic phosphate into solution. The addition of an excess of acetate ensures the consumption of any oxygen and nitrate, and the depletion of intracellular polyphosphates available for acetate storage. Thus, this new method offers a much easier approach than those previously available to quantify polyphosphate, one of the two storage polymers involved in the mechanism of biological phosphate removal.
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Boehler, M., i H. Siegrist. "Potential of activated sludge disintegration". Water Science and Technology 53, nr 12 (1.06.2006): 207–16. http://dx.doi.org/10.2166/wst.2006.423.
Pełny tekst źródłaStreszczenie:
The disposal of sewage sludge and the agricultural use of stabilised sludge are decreasing due to more stringent regulations in Europe. An increasing fraction of sewage sludge must therefore be dewatered, dried, incinerated and the ashes disposed of in landfills. These processes are cost-intensive and also lead to the loss of valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Disintegration of biological sludge by mechanical, thermal and physical methods could significantly reduce excess sludge production, improve the settling properties of the sludge and reduce bulking and scumming. The solubilised COD could also improve denitrification if the treated sludge is recycled to the anoxic zone. However, disintegration partly inhibits and kills nitrifiers and could therefore shorten their effective solid retention time, thus reducing the safety of the nitrification. This paper discusses the potential of disintegration on sludge reduction, the operating stability of nitrification, the improvement of denitrification and also presents an energy and cost evaluation.