Studies on Microbial Leaching of Heavy Metals from Municipal Sludge

1990 ◽  
Vol 22 (12) ◽  
pp. 229-238 ◽  
Author(s):  
R. D. Tyagi ◽  
D. Couillard ◽  
F. T. Tran
Keyword(s):  
Ammonia Nitrogen ◽  
Filter Press ◽  
Vacuum Filter ◽  
Continuous Stirred Tank Reactor ◽  
Microbial Leaching ◽  
Anaerobically Digested Sludge ◽  
Air Lift Reactor ◽  
Solid Liquid ◽  
Air Lift ◽  
Metal Solubilization

A comparative study between continuous stirred tank reactor (CSTR) with cell recycle and air-lift reactor was carried out in 30 1 capacity reactors for metal solubilization from anaerobically digested sludge. In CSTR at a residence time of 0.75 day, supplementing the feed sludge with 4 g/l of FeSO4.7H2O, using 20% sludge recycle and adjusting pH of the feed sludge to 4.5 resulted in following metal solubilization : 91% Cu, 94% Zn,, 93% Mn, 67% Cd, 67% Ni, 8% Cr, and 7% Pb. At 0.75 day retention time metals were solubilized to the recommended level in CSTR as well as in air-lift reactor. The treated sludge is easy to filter in plates filter press, centrifugation, or vacuum filter. The sludge nutrients do not seem to be diminished as a result of treatment and separation of solid-liquid. The ammonia-nitrogen fraction seems to be transformed in organic nitrogen. The decontaminated sludge produced has less odour.

Effect of Dye Concentration on Adsorption Efficiency in the Air-Lift Reactor

2007 ◽  
Vol 22 (3) ◽  
pp. 447-458
Author(s):  
Urszula Filipkowska ◽  
Aneta Hołownia-Kosak
Keyword(s):  
Adsorption Efficiency ◽  
Air Lift Reactor ◽  
Air Lift

Enhanced sludge conditioning by enzyme pre-treatment: comparison of laboratory and pilot scale dewatering results

2006 ◽  
Vol 54 (5) ◽  
pp. 33-41 ◽  
Author(s):  
D. Dursun ◽  
M. Turkmen ◽  
M. Abu-Orf ◽  
S.K. Dentel
Keyword(s):  
Extracellular Polymeric Substances ◽  
Treatment Plant ◽  
Pilot Scale ◽  
Solid Content ◽  
Filter Press ◽  
Treatment Comparison ◽  
Anaerobically Digested Sludge ◽  
Network Strength ◽  
Pre Treatment ◽  
Solids Content

The effect of enzyme pre-treatment on dewaterability of anaerobically digested sludge was investigated at both laboratory and pilot scale. Our results revealed a significant increase in cake solid content (27% cake solids compared to 18% without enzyme pre-treatment), using an enzyme dose of only 20 mg/L. In order to assess practical application, enzyme pre-treatment was applied at the Wilmington, Delaware (US) wastewater treatment plant, using a pilot-scale centrifuge. However, the efficiency reached in laboratory scale could not be obtained in pilot scale, where the final cake solids content did not exceed 20%. Centrifuge and belt filter press (simulated by Crown Press™) dewatering were compared in terms of the process efficiencies in the absence and presence of enzyme pre-treatment. Possible factors that might cause the differences were tested by experimental and statistical comparisons. Results indicated that the higher shear applied in centrifugation is responsible for the lack of improved cake solids. The network strength of sludge determined by rheological measurements revealed that enzymatic treatment weakens the gel structure of the sludge floc through the hydrolysis of extracellular polymeric substances; this allows improved dewatering by filtration processes, but leads to floc deterioration when subjected to high shear during centrifugation.

Ozonation combined with ultrasound for the degradation of tetracycline in a rectangular air-lift reactor

2012 ◽  
Vol 84 ◽  
pp. 138-146 ◽  
Author(s):  
Yan Wang ◽  
Hui Zhang ◽  
Lu Chen ◽  
Sheng Wang ◽  
Daobin Zhang
Keyword(s):  
Air Lift Reactor ◽  
Air Lift

Degradation of C.I. Acid Orange 7 by ultrasound enhanced ozonation in a rectangular air-lift reactor

2008 ◽  
Vol 138 (1-3) ◽  
pp. 231-238 ◽  
Author(s):  
Hui Zhang ◽  
Yujuan Lv ◽  
Fang Liu ◽  
Daobin Zhang
Keyword(s):  
Acid Orange 7 ◽  
Acid Orange ◽  
Air Lift Reactor ◽  
Air Lift

through tubing and fittings made of PTFE. Analysis was undertaken by the Warren Spring Laboratory of the Department of Trade and Industry, according to the method described by Bailey and Bedbo rough The results are shown in Table IV. and plotted in Fig. 3. and 4. Table IV. Variation of odour strength of extracted samples with volune of eluted air Volume of air Strength of odour samples passing through (dilutions) sludge before sampling (1/1) Raw sludge Digested sludge 0 154 000 9 900 11.1 53 000 350 22.2 30 600 270 55.6 15 500 190 111 8 200 160 It is clear from these results that there is considerable die-off of odour strength with time, and that, as would be expected, the anaerobic digestion of sludge can reduce the odour potential by at least one order of magnitude. To illustrate the importance of this die-off effect, the results have been re-plotted in Fig. 5. in a cunulative form; that is to say as cumulative percentage of the eventual colour release against volume of air. In the case of the raw sewage sludge, 38% of the ultimate odour was carried in the first odour sample, and 90% of the odour had been extracted by the passage of about 200 1. In the case of the anaerobically digested sludge, the same effect is much more marked; 72% of the ultimate odour was carried by the first sample, and thereafter the strength of the odour fell off very rapidly. There are two possible explanations for this. First, it can be postulated that as it is known that many of the important odorous chemical species are highly volatile, they may be only physically trapped in the sludge, and need little encouragement to transfer to the atmosphere. An alternative explanation concerns the existence of two equilibria. As the vapour/liquid equilibrium is disturbed by the passage of air, the concentration of dissolved compounds in the liquid phase falls, disturbing the ’solid’/liquid equilibrium The kinetics of transfer across this latter phase boundary are much slower than for the liquid/vapour transfer, so that the extraction of odour becomes limited by the rate of diffusion into the liquid phase. Two observations may be cited as evidence for this latter view. First, when sludge is applied to land, there is a rapid tail-off of odour nuisance after spreading. Hie incidence of rain after a dry period is known to result in an increased evolution of odour. Second, in earlier experiments samples of sludge were centrifuged, and the supernatant liquor discarded and replaced by tap water, before being used in the standard odour potential test. Some re-extraction of odour from the samples was rapidly found. In practice, both postulated mechanisms are probably at work, especially if the concept of ’solid/liquid equilibrium’ be extended to

1986 ◽  
pp. 152-152
Keyword(s):  
Liquid Phase ◽  
Tap Water ◽  
Chemical Species ◽  
Liquid Equilibrium ◽  
Digested Sludge ◽  
Order Of Magnitude ◽  
Anaerobically Digested Sludge ◽  
Solid Liquid ◽  
Kinetics Of ◽  
Potential Test

scholarly journals Nucleation Triggering of Highly Undercooled Xylitol Using an Air Lift Reactor for Seasonal Thermal Energy Storage

2018 ◽  
Author(s):  
Marie DUQUESNE ◽  
Elena PALOMO DEL BARRIO ◽  
Alexandre GODIN
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
High Energy ◽  
Operating Conditions ◽  
High Energy Density ◽  
Bubble Generation ◽  
Spontaneous Nucleation ◽  
Air Lift Reactor ◽  
Air Lift

Xylitol is an organic, non-toxic, biosourced phase change material with high potential for seasonal thermal energy storage material. It has a high energy density, a high and stable undercooling allowing storing solar energy at ambient temperature thus, reducing thermal losses and the risk of spontaneous nucleation (i.e., the risk of losing the stored energy). When the energy is needed, the discharge triggering of the storage system (i.e., Nucleation triggering of highly viscous undercooled Xylitol) is very difficult as well as reaching a sufficient power delivery (i.e., the control of the subsequent crystal growth rates). Both are the mains locks for the use of Xylitol in seasonal energy storage. Different techniques to crystallize highly undercooled Xylitol have hence been considered. It has been proven that nucleation triggering of highly undercooled Xylitol using an air lift reactor would allow reaching performances matching with building applications (i.e., at medium temperatures, below 100 °C). The advantages of this technique compared to other existing techniques to activate the crystallization are discussed. The mechanisms triggering the nucleation are investigated. The air bubble generation, transportation of nucleation sites and subsequent crystallization are discussed to improve the air injection operating conditions.

Development and Scale-Up of an Aerobic Biofilm Air-Lift Suspension Reactor

1993 ◽  
Vol 27 (5-6) ◽  
pp. 253-261 ◽  
Author(s):  
J. J. Heijnen ◽  
M. C. M. van Loosdrecht ◽  
R. Mulder ◽  
R. Weltevrede ◽  
A. Mulder
Keyword(s):  
Aerobic Oxidation ◽  
Scale Up ◽  
Suspended Particles ◽  
Aerobic Treatment ◽  
Treatment Concept ◽  
Air Lift Reactor ◽  
Volumetric Loading ◽  
Air Lift ◽  
Sludge Production

A new aerobic treatment concept for the aerobic oxidation of COD, ammonia and sulphide has been developed. The concept is based on the formation of biofilms on small suspended particles in an air-lift reactor. This reactor concept enables to combine a low sludge loading with a high volumetric loading. This makes the reactor especially useful for e.g. nitrification processes. It is also feasible to operate under conditions of marginal sludge production. In this article the scale up aspects of such a process are discussed.

scholarly journals Performance of Anaerobic Digestion of Chicken Manure Under Gradually Elevated Organic Loading Rates

2019 ◽  
Vol 16 (12) ◽  
pp. 2239 ◽  
Author(s):  
Fei Wang ◽  
Mengfu Pei ◽  
Ling Qiu ◽  
Yiqing Yao ◽  
Congguang Zhang ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Biogas Production ◽  
Poultry Manure ◽  
Ammonia Nitrogen ◽  
Methane Content ◽  
Chicken Manure ◽  
Continuous Stirred Tank Reactor ◽  
Organic Loading ◽  
Biogas Yield ◽  
Loading Rates

Poultry manure is the main source of agricultural and rural non-point source pollution, and its effective disposal through anaerobic digestion (AD) is of great significance; meanwhile, the high nitrogen content of chicken manure makes it a typical feedstock for anaerobic digestion. The performance of chicken-manure-based AD at gradient organic loading rates (OLRs) in a continuous stirred tank reactor (CSTR) was investigated herein. The whole AD process was divided into five stages according to different OLRs, and it lasted for 150 days. The results showed that the biogas yield increased with increasing OLR, which was based on the volatile solids (VS), before reaching up to 11.5 g VS/(L·d), while the methane content was kept relatively stable and maintained at approximately 60%. However, when the VS was further increased to 11.5 g VS/(L·d), the total ammonia nitrogen (TAN), pH, and alkalinity (CaCO3) rose to 2560 mg·L−1, 8.2, and 15,000 mg·L−1, respectively, while the volumetric biogas production rate (VBPR), methane content, and VS removal efficiency decreased to 0.30 L·(L·d)−1, 45%, and 40%, respectively. Therefore, the AD performance immediately deteriorated and ammonia inhibition occurred. Further analysis demonstrated that the microbial biomass yield and concentrations dropped dramatically in this period. These results indicated that the AD stayed steady when the OLR was lower than 11.5 g VS/(L·d); this also provides valuable information for improving the efficiency and stability of AD of a nitrogen-rich substrate.

Effect of pH on metal solubilization from sewage sludge: a neural-net-based approach

1994 ◽  
Vol 21 (5) ◽  
pp. 728-735 ◽  
Author(s):  
Y. G. Du ◽  
T. R. Sreekrishnan ◽  
R. D. Tyagi ◽  
Peter G. C. Campbell
Keyword(s):  
Heavy Metals ◽  
Sewage Sludge ◽  
Municipal Sewage ◽  
Municipal Sewage Sludge ◽  
Neural Net ◽  
Metals Removal ◽  
Complex Biological Process ◽  
System Temperature ◽  
Microbial Leaching ◽  
Metal Solubilization

Microbial leaching for heavy metals removal from municipal sewage sludge is a complex biological process. The ultimate metal solubilization achieved depends on the type of sludge involved (nondigested, aerobically digested or anaerobically digested sludge), the decrease in sludge pH as a result of the leaching operation, and the concentration of metals initially present in the sludge. In addition, the system temperature exerts an indirect but strong influence by its effect on the bacterial growth and acid production process. A neural-net-based model was developed to predict the solubilization of six heavy metals, Cd, Cr, Cu, Ni, Pb, and Zn, from sewage sludge using the bioleaching process. The only input parameters required are the type of sludge, initial metal concentrations in the sludge, and the sludge pH. The model yielded satisfactory predictions of metal solubilization when tested with a number of actual experimental data. Key words: heavy metals, microbial leaching, modelling, neural-net, sewage sludge.

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