Results 1 - 10 of 5750
Results 1 - 10 of 5750. Search took: 0.03 seconds
|Sort by: date | relevance|
[en] An oligochaete reactor linked to an integrated oxidation ditch with vertical cycle (IODVC) was used to investigate the sludge reduction potential induced by worms. The presence of Tubificidae was observed in the worm reactor throughout the operational period after its inoculation, and Tubificidae was occasionally found in the IODVC. Free-swimming worms, Aeolosoma hemprichi, Nais elinguis, and Aulophorus furcatus, were found in both the IODVC and the worm reactor, but A. hemprichi was dominant. A. hemprichi reached its maximum, 322 and 339 Aeolosoma/mL mixed liquor on day 49 in the worm reactor and the IODVC, respectively. The presence of oligochaetes or the integration of worm reactor with the IODVC had little effect on sludge yield, but the worm growth was helpful for improving sludge settling characteristics. The average sludge yield and sludge volume index (SVI) in the IODVC were 0.33 kgSS/kgCODremoved and 78 mL/g, respectively. The worm presence had little impact on effluent quality of the IODVC, but it caused phosphorus release into the effluent. The average COD, NH4+-N, and SS concentrations in the effluent of the IODVC were 49.06, 12.82, and 58.25 mg/L, respectively. No total nitrogen (TN) release into the effluent of the IODVC occurred
[en] A good place for the first sludge irradiator in Mexico would be the Toluca Norte sewage water treatment plant. This plant has a definitive biological treatment, and handles only domestic wastewater and assures therefore good and stead sewage sludge quality, and has capacity do deliver sufficient sludge (approximately 22,000 ton.y-1 or 70 ton.d-1) to the irradiator. Capital and operating cost calculations for a sewage sludge plant by irradiation in Mexico were done using a mathematical model considering a 50 k W electron linear accelerator of 10 MeV beam energy, an irradiation dose of 5 kGy, a treatment capacity of 346 ton.d-1, an absorption efficiency of 40%, an electricity consumption of 400 k W, an operating mode of 325 days per year and one shift per day. Total annual operating costs is estimated to be $1,007,900 for treating 346 ton.d-1 with irradiation dose of 5 kGy, including both fixed ($664,000) and variable costs ($343,920). The unit cost at maximum utilization was obtained as $9.00 per ton. (author). 16 refs., 3 tabs
[en] The expected quantity of sludge from waste water purification plants in the Netherlands is estimated for the period 1998-2005 and extrapolated to the year 2015. Also attention is paid to the available sludge processing capacity and amount of biogas that can be produced by digestion of sewage sludge in the period 1998-2005. 7 refs
[en] Activated sludges from the wastewater treatment of an oil refinery were characterized in order to improve the biotreatment of soils contaminated with hydrocarbons. The objective was to evaluate whether such industrial wastes that are being sent to landfills could be used for any useful purposes. A sand pit soil that contained 416 mg PAHs/kg and a gas station soil containing 1 mg PAHs/kg were evaluated. The study showed that activated sludges contain high concentration of oil and grease. Activated sludges were also found to be a valuable source of nitrogen and adapted bacteria
[en] This study aimed to determine the types of bacteria exist in wastewater that contribute to generate electricity and simultaneously remove carbon and nitrogen. The method used was Fluorescence In Situ Hybridization (FISH) to detect the bacteria group while Polymerase Chain Reaction (PCR) was used to confirm the observation made using FISH. A biochemical identification using BIOLOG GEN III MICROPLATETM also was used . The samples were cultured on nutrient agar plate to identify the morphology of the bacteria. The result showed that 21 isolates from three different locations at the activated sludge treatment plant with six, eleven and four strains for raw sewage, aeration tank and returned activated sludge samples, respectively. Preliminary identification does not give a good match but only showed the existence of ammonia-oxidizing bacteria (FISH) and Kurtia Gibsoni (BIOLOG) from aeration tank : Bacillus sp (PCR) and Bacillus Pseudomycoides (BIOLOG) from returned activated sludge. The maximum power density generated using returned activated sludge was 9.053 mW/ cm2, with 26.8 % COD removal and 40 % TKN removal (author)
[en] This research project focuses on pollutants from the combustion of mixtures of dried municipal sewage sludge (MSS) and coal. The objective is to determine the relationship between (1) fraction sludge in the sludge/coal mixture, and (2) combustion conditions on (a) NO(sub x) concentrations in the exhaust, (b) the size segregated fine and ultra-fine particle composition in the exhaust, and (c) the partitioning of toxic metals between vapor and condenses phases, within the process. To this end work is progress using an existing 17kW downflow laboratory combustor, available with coal and sludge feed capabilities. The proposed study will be conducted in concert with an existing ongoing research on toxic metal partitioning mechanisms for very well characterized pulverized coals alone. Both high NO(sub x) and low NO(sub x) combustion conditions will be investigated (unstaged and staged combustion). The proposed work uses existing analytical and experimental facilities and draws on 20 years of research on NO(sub x) and fine particles that has been funded by DOE in this laboratory. Four barrels of dried sewage sludge are currently in the laboratory. Insofar as possible pertinent mechanisms will be elucidated. Tradeoffs between CO(sub 2) control, NO(sub x) control, and inorganic fine particle and toxic metal emissions will be determined. For the Fifth Quarter of this project we focus on determining whether certain trace metals are associated with certain major species, such as calcium and iron. To this end we present data showing correlations between As, Se,and Sb and major species, such as Ca and Fe. Conversely, lack of correlation between trace metals and elements, such as aluminum can also be used to infer lack of chemical association
[en] In this study, the properties of unstable and stable flocs were investigated under the steady operation of a membrane bioreactor (MBR). The extracellular polymeric substances (EPS) composition, surface charge, and hydrophobicity of unstable and stable flocs were examined and compared. Interfacial interactions of the membrane with unstable flocs, unstable flocs themselves, and unstable and stable flocs were assessed using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) models. Cake layer resistance was found to contribute more than 80% of total resistance under steady operating conditions. Compared with stable flocs, unstable flocs possessed a higher level of EPS, more diverse protein, more negative charge, weaker hydrophobicity, and higher fouling potential. Thermodynamic analyses showed that unstable flocs had a higher adhesive strength (− 63.4 mJ/m2) with the membrane, lower self-cohesive strength (− 18.3 mJ/m2), and higher cohesive strength (− 54.3 mJ/m2) with stable flocs. Therefore, some unstable flocs remained on the membrane surface to form the cake layer due to their poor cohesion strength.
[en] Constructed wetlands (CWs) are engineered systems that have been designed and constructed to utilize natural processes involving wetland soils, vegetation, and microbes to treat wastewater (Vymazal, 2018). In CWs substrates or filling material act as carriers for biofilm development, medium for plant growth and adsorbent for pollutant removal.
[en] In this study, we explored the effect of chemical oxygen demand (COD) load on the nitrification and microbial communities in activated sludge isolated from an aerobic nitrifying tank. The activated sludge was cultured in three different COD groups: L-COD, 200 mg/L; M-COD, 1200 mg/L; H-COD, 4200 mg/L. The results indicated that the COD exerts a negligible effect on the nitrogen removal ability within the first 24 h. However, the nitrification rate decreased with culture time; the ammonium degradation rates were found to be 80.26%, 57.56%, and 43.43% at 72 h in the three COD groups, respectively. These values correspond to decreases of 19.40%, 41.83%, and 51.48%, respectively, in relation to those observed at 24 h. The activated sludge in the different COD groups exhibited similar community compositions after 24 h, as assessed by Illumina high-throughput sequencing, while a significant difference in the relative abundances of some organisms occurred after 48 and 72 h. Proteobacteria was the main phylum, with a relative abundance of >51.45%. The genera Aridibacter, Paracoccus, Nitrospira, and Nitrosomonas were suppressed by COD load over time. This study may contribute to our knowledge about the nitrification ability and microbial communities in activated sludge at different COD load levels. (author)
[en] The effects of Ni(II) in a synthetic wastewater on the activity of activated sludge microorganisms and sequencing batch reactor (SBR) treatment process were investigated. Two parallel lab-scale SBR systems were operated. One was used as a control unit, while the other received Ni(II) concentrations equal to 5 and 10 mg/l. The SBR systems were operated with FILL, REACT, SETTLE, DRAW and IDLE modes in the time ratio of 0.5:3.5:1.0:0.75:0.25 for a cycle time of 6 h. The addition of Ni(II) into SBR system caused drastically dropped in TOC removal rate (k) and specific oxygen uptake rate (SOUR) by activated sludge microorganisms due to the inhibitory effects of Ni(II) on the bioactivity of microorganisms. The addition of 5 mg/l Ni(II) caused a slight reduction in TOC removal efficiency, whereas 10 mg/l Ni(II) addition significantly affected the SBR performance in terms of suspended solids and TOC removal efficiency. Termination of Ni(II) addition led to almost full recovery of the bioactivity in microorganisms as shown in the increase of specific oxygen uptake rate (SOUR) and SBR treatment performance