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Water pipe sediment removal should be implemented as an integral part of water mains maintenance in order to steadily supply consumers with drinking water of high quality. Considering the number of different water pipe sediment removal methods, the article aims to evaluate the currently used methods to remove water pipe sediment from the pipes of the drinking water distribution system. The evaluation compares the implementation requirements of each method as well as the quality and the quantity of the removed products. The tested methods were unidirectional flushing, Comprex®, and Ice Pigging®. The results of the comparison are expressed in terms of total suspended solids (TSS) recovery, metals mass concentration and water consumption. Since contamination can settle along the entire surface of the pipeline, it is most appropriate to recalculate the results per unit area of the pipeline. The results point at the following efficiency the Comprex® method was the most efficient in removing TSS, Ice Pigging® was the next and unidirectional flushing removed a negligible amount of TSS compared to the other two methods. The absolute recovery of TSS was 0.12-3.01 g·m-2 in unidirectional flushing of plastic pipes, 1.58-8.54 g·m-2 in unidirectional flushing of metal pipes, 4.36-47.53 g·m-2 in Ice Pigging®, and 5.19-69.23 g·m-2 in Comprex®. The composition of the sediment was strongly influenced by particle origin: Pipe material affected the crystalline phase of the sediment and the water source and the age of the pipe affected the amorphous phase of the sediment. Therefore, it was found that evaluation of efficiency based on the amount of TSS removed is only suitable for sites that meet the same conditions as pipe material, water source and ideally the pipe age. It has further been found that the Comprex® method can be advantageously used in real conditions to clean pipes with insufficient hydraulic conditions (such as with a high level of incrustation), as the cleaning has low water flow velocity requirements.
- MeSH
- kovy MeSH
- mikrobiologie vody MeSH
- pitná voda * MeSH
- zásobování vodou MeSH
- Publikační typ
- časopisecké články MeSH
7, 408 s.
The analytical model suggested some time ago for the calculation of bond indices in infinite periodical structures was reconsidered and extended so as to provide not only realistic estimate of the extent of electron sharing localized among individual pairs of the atoms in the lattice but also to detect the eventual presence of multicenter bonding in metallic solids.
- MeSH
- algoritmy MeSH
- chemické modely MeSH
- elektrony MeSH
- kvantová teorie MeSH
- lithium chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
323 s. : il.
427 s.
This Review summarizes all of the currently described strategies applicable for the solid-phase synthesis of purine derivatives. The individual approaches are classified according to the immobilization procedure used resulting in a linkage of the final scaffold at various positions.
We report two synthetic strategies for traceless solid-phase synthesis of molecular scaffolds comprising 6- to 8-membered rings fused with 5- to 7-membered rings. Traceless synthesis facilitated preparation of target molecules without any trace of polymer-supported linkers. The cyclization proceeded via acid-mediated tandem N-acylium ion formation followed by the nucleophilic addition of O- and C-nucleophiles. The presented synthetic strategy enabled, through the use of simple building blocks without any conformational preferences, the evaluation of the predisposition of different combinations of ring sizes to form fused ring molecular scaffolds. Compounds with any combination of [6,7 + 5,6,7] ring sizes were accessible with excellent crude purity. The 8-membered cyclic iminium was successfully fused only with the 5-membered cycle and larger fused ring systems were not formed, probably due to their instability.
High-solid anaerobic digestion of the very small particle fraction of mechanically-sorted organic fraction of municipal solid waste (OFMSW) was examined in mesophilic digestion tests in a conventional laboratory (0.013 m3) and a pilot (0.300 m3) reactor. The non-biodegradable and recalcitrant molecules together with the low protein and starch contents of the small-particles of OFMSW limited the methane generation potential of substrate. In the conventional AD system, methane yields remained low at 0.139 m3kgVS-1 due to formation of a non-reacting layer on digestate surface, which restricted utilization of the available in OFMSW digestible organics. The absence of surface solid crust in the pilot unit favoured consumption of a greater proportion of volatile solids of the OFMSW. Dry AD was remarkably stable over the entire period and negligibly effected by the toxic H2S yields. Methane generation (0.167 m3kgVS-1) was increased 1.2-fold compared to the conventional system due to a better mixing of substrate and microorganisms achieved inside the pilot reactor, which led to an increase of the digested volatile organics. Digestate presented low stability and high heavy metal content, both of which restrain its implementation as soil conditioner or fertilizer in agriculture. A secondary co-digestion treatment may be required for the neutralization of digestate.
- MeSH
- anaerobióza MeSH
- bioreaktory MeSH
- laboratoře MeSH
- methan MeSH
- odpadky - odstraňování * MeSH
- tuhý odpad * analýza MeSH
- Publikační typ
- časopisecké články MeSH
We have developed a robust solid-phase protocol which allowed the synthesis of chimeric oligonucleotides modified with phosphodiester and O-methylphosphonate linkages as well as their P-S and P-N variants. The novel O-methylphosphonate-derived modifications were obtained by oxidation, sulfurization, and amidation of the O-methyl-(H)-phosphinate internucleotide linkage introduced into the oligonucleotide chain by H-phosphonate chemistry using nucleoside-O-methyl-(H)-phosphinates as monomers. The H-phosphonate coupling followed by oxidation after each cycle enabled us to successfully combine H-phosphonate and phosphoramidite chemistries to synthesize diversely modified oligonucleotide strands.
