Author(s): Li F, Wichmann K, Heine W
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Abstract A leachate purification system, equipped with the thin open channel spiral wound modules, is studied in this paper. In Phase I, effluent from an activated sludge process followed by the flocculation/sedimentation process was fed into the landfill leachate treatment unit. After 2 wk of operation, the permeate flux dropped dramatically, from an average value of 6.5l/m(2)/h to 4.23 l/m(2)/h. The significant decline of membrane flux was likely caused by membrane fouling. In Phase II, raw leachate was fed directly into the reverse osmosis leachate treatment system. An average flux of 7.8l/m(2)/h was maintained at an initial trans-membrane pressure difference of 20 bar, which increased to 40 bar before membrane chemical cleaning. An average recovery rate of 70\% was achieved. Throughout the observation in Phase II, an average reduction rate of 98.2\% for the dissolved solids was obtained. The reduction rate of COD was greater than 99.5\% with a constant level of the permeate COD. Chloride was eliminated by more than 99\%, while over 98\% of NH(4)-N was reduced. A negligible permeate flux drop was observed after cleaning the membrane effectively. The study shows that direct reverse osmosis membrane filtration with thin open channel spiral wound modules is able to achieve satisfactory results in terms of water quality, process stability and membrane flux. The obtained quality of the permeate quality in this study met the German standards for leachate discharge. At the end of each filtration cycle, the membrane was maintained through alkaline chemical cleaning in order to remove any irreversible membrane fouling. After the maintenance procedure, the membrane flux was found to recover to the initial value.
This article was published in Waste Manag
and referenced in International Journal of Waste Resources
- Eugene Stephane Mananga
On Fer and Floquet-Magnus expansions: Application in solid-state nuclear magnetic resonance and physics
- Yosef Yarden
Classically, the 3âuntranslated region (3âUTR) is that region in eukaryotic protein-coding genes from the translation termination codon to the polyA signal. It is transcribed as an integral part of the mRNA encoded by the gene. However, there exists another kind of RNA, which consists of the 3âUTR alone, without all other elements in mRNA such as 5âUTR and coding region. The importance of independent 3âUTR RNA (referred as I3âUTR) was prompted by results of artificially introducing such RNA species into malignant mammalian cells. Since 1991, we found that the middle part of the 3âUTR of the human nuclear factor for interleukin-6 (NF-IL6) or C/EBP gene exerted tumor suppression effect in vivo. Our subsequent studies showed that transfection of C/EBP 3âUTR led to down-regulation of several genes favorable for malignancy and to up-regulation of some genes favorable for phenotypic reversion. Also, it was shown that the sequences near the termini of the C/EBP 3âUTR were important for its tumor suppression activity. Then, the C/EBP 3âUTR was found to directly inhibit the phosphorylation activity of protein kinase CPKC in SMMC-7721, a hepatocarcinoma cell line. Recently, an AU-rich region in the C/EBP 3âUTR was found also to be responsible for its tumor suppression. Recently we have also found evidence that the independent C/EBP 3âUTR RNA is actually exists in human tissues, such as fetal liver and heart, pregnant uterus, senescent fibroblasts etc. Through 1990âs to 2000âs, world scientists found several 3âUTR RNAs that functioned as artificial independent RNAs in cancer cells and resulted in tumor suppression. Interestingly, majority of genes for these RNAs have promoter-like structures in their 3âUTR regions, although the existence of their transcribed products as independent 3âUTR RNAs is still to be confirmed. Our studies indicate that the independent 3âUTR RNA is a novel non-coding RNA species whose function should be the regulation not of the expression of their original mRNA, but of some essential life activities of the cell as a whole.
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