[Optimized cultivation of a bioflocculant M-C11 produced by Klebsiella pneumoniae and its application in sludge dewatering].

A bioflocculant-producing Klebsiella pneumoniae strain C11 was screened out from activated sludge and the optimal medium conditions for the production of microbial flocculant M-C11 were determined. The bioflocculant was used in activated sludge dewatering and compared with conventional chemical conditioners. Effects of pH, CaCl2 dosages and M-C11 dosages on sludge dewaterability were investigated. The optimized conditions for M-C11 production indicated that the optimal medium carbon, nitrogen, metal ion were 30 g x L(-1) glucose, 2 g x L(-1) NaNO3 and 0.5 g x L(-1) MgSO4, respectively. The flocculating rate with kaolin suspension was as high as 91.70%, when incubated in a rotary shaker at 150 r x min(-1) and 37 degrees C for 48 h. The microbial focculant showed excellent pH and thermal stability over a pH range of 4-8 and a temperature range of 20-60 degrees C. Then the bioflocculant M-C11 produced by Klebsiella pneumoniae was employed to enhance the sludge dewaterability. The sludge resistance to filtration (SRF) and cake moisture decreased from 11.64 x 10(12) m x kg(-1) and 98.86% to 4.66 x 10(12) m x kg(-1) and 83.74%, respectively. Sludge dewatering performance was more significantly improved with the optimal conditioning dosages (pH = 6, 3 mL M-C11, 4 mL CaCl2), than inorganic flocculating reagents such as aluminum sulfate and polymeric aluminum chloride (PAC). The microbial flocculant has advantages over traditional sludge conditioners for its lower cost, benign biodegradability and ignorable secondary pollution. In addition, it was favorably adapted to the sludge pH and salinity. The novel bioflocculant could be used as a potential conditioner for sludge dewatering.

[Sludge dewaterability with combined conditioning using Fenton's reagent and CPAM].

The moisture of sludge significantly influenced its dewaterability and the disposal cost. Cationic polyacrylamide (CPAM) and Fenton's reagent were investigated for sludge dewatering with separate and combined conditioning. Several parameters were used to evaluate the dewatering performance and to analyze the conditioning mechanism, such as cake moisture, soluble COD, protein and polysaccharide contents in supernatant and sludge particle size. The results indicated that favorable dewaterability was achieved when the sludge was conditioned at higher CPAM degrees, and sludge dewatering ability was further improved at acidic conditions. In Fenton reaction, higher H2O2 dosages enhanced the dewatering performance of sludge. Combined conditioning using Fenton's reagent and CPAM led to considerable improved sludge dewaterability. At the optimized dosages of FeSO4 (2 g x L(-1)) and H2O2 (6 g x L(-1)), the sludge moisture declined to 76.7% from 85.5% (raw sludge), while a moisture as low as 74.8% was obtained by combined conditioning using CPAM (3 kg x t(-1)). Sludge particle size went down and the specific surface area grew bigger after Fenton reaction. As a result of disintegration of extracellular polymeric substances (EPS), the adsorbed and intrinsic water were released from microorganisms and sludge flocs. CPAM addition remarkably promoted the coagulating and flocculating of dispersed flocs. Sludge particle size changed from 35.16 microm to 50.50 microm, and the specific surface area declined from 0.39 m2 x g(-1) to 0.20 m2 x g(-1). The combined conditioning using Fenton's reagent and CPAM was proved to be more effective in improving sludge dewaterability, compared with the separate conditioning.

[Research of moisture content variation in MSW landfill].

Using time domain reflectometry (TDR) technology, waste moisture content variation in aerobic and anaerobic landfill of MSW was monitored, in order to study its disciplinarian. The results showed that volume moisture content of waste increased with landfill time and water holding capacity of waste improved continuously. The correlation of water quantity and moisture content was positive in early aerobic landfill, but it became negative later. In anaerobic landfill, moisture content variation was caused by settlement and compression of MSW. TDR readings and waste material-based volume moisture content had a good correlation. The maximum error between them is about +/- 5% in aerobic landfill and +/- 2% in anaerobic landfill. TDR technology is applicable to measure moisture content in practical landfill engineering.

[Fluorescence characterization of leachate organic matter in 717 resin adsorption process].

Synchronous fluorescence spectroscopy and 3-dimensional excitation emission matrices spectra (3DEEM) were used to study the composition variation of dissolved organic matter (DOM) in landfill leachate in the adsorption process with 717 resin. The synchronous fluorescence spectra showed fluorescence intensities of longer wavelength went down greatly while those of shorter wavelength went up in the first 10 min, then there were little changes. 3DEEM results indicated that there were two fulvic-like fluorescence peaks, whose intensities decreased dramatically, the peak intensities ratio (I(UV)/I(Vis)) also decreased, and the blue shifts of emission wavelengths took place obviously with the time rising. It was indicated that the adsorption rate of DOM by 717 resin was fast, and the main adsorbed DOM had higher molecular weight and higher degree of complexity, which was potential to facilitate subsequent bio-treatment.

[Dynamic leaching behavior of heavy metals in eco-cement mortar block].

A dynamic leaching test with the renewal of acidic leaching medium was designed to study the leaching behavior of the seven heavy metals (As, Cd, Cr, Cu, Ni, Pb, Zn) in three solidified eco-cement mortar samples with different particle size (fine granule, coarse granule, block) under a long-term leaching condition. It was demonstrated that all the heavy metals were detected in the leachate except Cd. The leaching ratio of Cr was the highest when compared with other metals in the same sample, and the leaching ratio of every metal showed an identical tendency: fine granule> coarse granule > block. The on-going leaching part of the relationship curve of accumulative leaching point (Pt) and t1/2 of each metal presented a fairly good linearity, which indicated that the leaching process was under the control of diffusion mechanism by the Fick Law. To each metal, the effective diffusion coefficient (Deff) showed a tendency of fine granule < coarse granule < block, which was opposite to the tendency of leaching ratio. It could be concluded that the solidified eco-cement mortar with a bigger size would have a lower leaching ratio and a shorter period to finish the leaching test. To all the metals, the Deff was very low, with the magnitude around 10(-10) cm2/s, which meant the leaching process would take a relatively long time.

[Vaporization of organic acids from young landfill leachate during evaporation].

To obtain the vaporization rule of organic pollutants in a young landfill leachate, we conducted normal evaporation and gas-carrying evaporation experiments, analyzing TOC and volatile fatty acids (VFAs) of batch condensate. The results showed that TOC in condensates declined when pH was 4, whereas it presented a contrary trend when pH was 7. Variation of VFAs except acetic acid in condensates was similar to that of TOC. The more complicated the chemical construction of VFAs was, the greater the relative rate of vaporization was. The results indicated that the organic matter in condensate from young landfill leachate mainly consisted of VFAs. The quantity change of carried gas didn't distinctly affect the vaporization rule of organic matter in young landfill leachate.

Fractionation of dissolved organic matter in mature landfill leachate and its recycling by ultrafiltration and evaporation combined processes.

XAD resin procedure was used to isolate dissolved organic matter (DOM) of a mature leachate collected from a municipal solid waste landfill in Beijing, China. The fulvic acids fraction dominated in collected leachate, accounting for 64% of DOM as dissolved organic carbon (DOC), and a high concentration of humic substances (HS) with a value of 441 mg l(-1) was found in the leachate. Molecular size distribution of DOM was also done by using batch ultrafiltration (UF) technique. Two major parts of the molecules of DOM were distributed in the regions of smaller than 1 kDa and 1-3.5 kDa, containing 45% and 43% of DOM as DOC, respectively. The laboratory-scale experiments were conducted to investigate and to develop an overall concept for mature leachate recycling based on UF and evaporation combined processes. Separation factor (SF) was applied to evaluate separation efficiency of UF. The data indicate that SF is strongly correlated with concentration factor. Second retentate from two-stage UF contained relatively high amount of DOM comprising 91% of HS and an insignificant concentration of heavy metals. The SF value for two-stage UF was more than 10. These results demonstrate that two-stage UF could effectively separate and refine HS in mature leachate from inorganic components. For achieving the main requirements as a fertilizer product, second retentate was further concentrated by evaporation, and contents of organic matter and dry-solids were obtained 13 wt.% and 25 wt.%, respectively. This study confirmed the feasibility of recycling HS from mature leachate.