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Accumulation Ratio

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Yongzhen Peng – One of the best experts on this subject based on the ideXlab platform.

Shuying Wang – One of the best experts on this subject based on the ideXlab platform.

  • achieving nitrite Accumulation in a continuous system treating low strength domestic wastewater switchover from batch start up to continuous opeRation with process control
    Applied Microbiology and Biotechnology, 2012
    Co-Authors: Yongzhen Peng, Jianhua Guo, H Horn, Xiong Yang, Shuying Wang
    Abstract:

    Although biological nitrogen removal via nitrite is recognized as one of the cost-effective and sustainable biological nitrogen removal processes, nitrite Accumulation has proven difficult to achieve in continuous processes treating low-strength nitrogenous wastewater. Partial nitrification to nitrite was achieved and maintained in a lab-scale completely stirred tank reactor (CSTR) treating real domestic wastewater. During the start-up period, sludge with ammonia-oxidizing bacteria (AOB) but no nitrite-oxidizing bacteria (NOB) was obtained by batch opeRation with aeRation time control. The nitrifying sludge with the dominance of AOB was then directly switched into continuous opeRation. It was demonstrated that partial nitrification to nitrite in the continuous system could be repeatedly and reliably achieved using this start-up strategy. The Ratio of dissolved oxygen to ammonium loading rate (DO/ALR) was critical to maintain high ammonium removal efficiency and nitrite Accumulation Ratio. Over 85% of nitrite Accumulation Ratio and more than 95% of ammonium removal efficiency were achieved at DO/ALR Ratios in an optimal range of 4.0–6.0 mg O2/g N d, even under the disturbances of ammonium loading rate. Microbial population shift was investigated, and fluorescence in situ hybridization analysis indicated that AOB were the dominant nitrifying bacteria over NOB when stable partial nitrification was established.

  • effective and robust partial nitrification to nitrite by real time aeRation duRation control in an sbr treating domestic wastewater
    Process Biochemistry, 2009
    Co-Authors: Yongzhen Peng, Shuying Wang, Yanan Zheng, Huijun Huang, Shijian Ge
    Abstract:

    Achieving sustainable partial nitrification to nitrite has been proven difficult in treating low strength nitrogenous wastewater. Real-time aeRation duRation control was used to achieve efficient partial nitrification to nitrite in a sequencing batch reactor (SBR) to treat low strength domestic wastewater. Above 90% nitrite Accumulation Ratio was maintained for long-term opeRation at normal condition, or even lower water temperature in winter. Partial nitrification established by controlling aeRation duRation showed good performance and robustness even though encountering long-term extended aeRation and starvation period. Process control enhanced the successful Accumulation of ammonia oxidizing bacteria (AOB) and washout of nitrite oxidizing bacteria (NOB). Scanning electron microscope observations indicated that the microbial morphology showed a shift towards small rod-shaped clusters. Fluorescence in situ hybridization (FISH) results demonstrated AOB were the dominant nitrifying bacteria, up to 8.3 ± 1.1% of the total bacteria; on the contrary, the density of NOB decreased to be negligible after 135 days opeRation since adopting process control.

Shuai Tian – One of the best experts on this subject based on the ideXlab platform.

Shijian Ge – One of the best experts on this subject based on the ideXlab platform.

  • effective and robust partial nitrification to nitrite by real time aeRation duRation control in an sbr treating domestic wastewater
    Process Biochemistry, 2009
    Co-Authors: Yongzhen Peng, Shuying Wang, Yanan Zheng, Huijun Huang, Shijian Ge
    Abstract:

    Achieving sustainable partial nitrification to nitrite has been proven difficult in treating low strength nitrogenous wastewater. Real-time aeRation duRation control was used to achieve efficient partial nitrification to nitrite in a sequencing batch reactor (SBR) to treat low strength domestic wastewater. Above 90% nitrite Accumulation Ratio was maintained for long-term opeRation at normal condition, or even lower water temperature in winter. Partial nitrification established by controlling aeRation duRation showed good performance and robustness even though encountering long-term extended aeRation and starvation period. Process control enhanced the successful Accumulation of ammonia oxidizing bacteria (AOB) and washout of nitrite oxidizing bacteria (NOB). Scanning electron microscope observations indicated that the microbial morphology showed a shift towards small rod-shaped clusters. Fluorescence in situ hybridization (FISH) results demonstrated AOB were the dominant nitrifying bacteria, up to 8.3 ± 1.1% of the total bacteria; on the contrary, the density of NOB decreased to be negligible after 135 days opeRation since adopting process control.

Quinton L Fivelman – One of the best experts on this subject based on the ideXlab platform.

  • activity of piperaquine and other 4 aminoquinoline antiplasmodial drugs against chloroquine sensitive and resistant blood stages of plasmodium falciparum role of β haematin inhibition and drug concentRation in vacuolar water and lipid phases
    Biochemical Pharmacology, 2007
    Co-Authors: David C. Warhurst, John Craig, Ipemida S. Adagu, Peter B Madrid, Quinton L Fivelman
    Abstract:

    Abstract Chloroquine (CQ), a 4-aminoquinoline, accumulates in acidic digestive vacuoles of the malaria parasite, preventing conversion of toxic haematin to β-haematin. We examine how bis 4-aminoquinoline piperaquine (PQ) and its hydroxy-modification (OH-PQ) retain potency on chloroquine-resistant (CQ-R) Plasmodium falciparum . For CQ, PQ, OH-PQ and 4 and 5 , representing halves of PQ, β-haematin inhibitory activity (BHIA) was assayed, while potency was determined in CQ-sensitive (CQ-S) and CQ-R P. falciparum . From measured p K a s and the pH-modulated distribution of base between water and lipid (log D), the vacuolar Accumulation Ratio (VAR) of charged drug from plasma water (pH 7.4) into vacuolar water (pH 4.8) and lipid Accumulation Ratio (LAR) were calculated. All agents were active in BHIA. In CQ-S, PQ, OH-PQ and CQ were equally potent while 4 and 5 were 100 times less potent. CQ with two basic centres has a VAR of 143,482, while 4 and 5 , with two basic centres of lower p K a s have VARs of 1287 and 1966. In contrast PQ and OH-PQ have four basic centres and achieve VARs of 104,378 and 19,874. This confirms the importance of VAR for potency against CQ-S parasites. Contrasting results were seen in CQ-R. 5 , PQ and OH-PQ with LARs of 693; 973,492 and 398,118 (compared with 8.25 for CQ) showed similar potency in CQ-S and CQ-R. Importance of LAR for potency against CQ-R parasites probably reflects ability to block efflux by hydrophobic interaction with PfCRT but may relate to β-haematin inhibition in vacuolar lipid.

  • activity of piperaquine and other 4 aminoquinoline antiplasmodial drugs against chloroquine sensitive and resistant blood stages of plasmodium falciparum role of β haematin inhibition and drug concentRation in vacuolar water and lipid phases
    Biochemical Pharmacology, 2007
    Co-Authors: David C. Warhurst, John Craig, Ipemida S. Adagu, Peter B Madrid, Kiplin R Guy, Quinton L Fivelman
    Abstract:

    Chloroquine (CQ), a 4-aminoquinoline, accumulates in acidic digestive vacuoles of the malaria parasite, preventing conversion of toxic haematin to beta-haematin. We examine how bis 4-aminoquinoline piperaquine (PQ) and its hydroxy-modification (OH-PQ) retain potency on chloroquine-resistant (CQ-R) Plasmodium falciparum. For CQ, PQ, OH-PQ and 4 and 5, representing halves of PQ, beta-haematin inhibitory activity (BHIA) was assayed, while potency was determined in CQ-sensitive (CQ-S) and CQ-R P. falciparum. From measured pK(a)s and the pH-modulated distribution of base between water and lipid (logD), the vacuolar Accumulation Ratio (VAR) of charged drug from plasma water (pH 7.4) into vacuolar water (pH 4.8) and lipid Accumulation Ratio (LAR) were calculated. All agents were active in BHIA. In CQ-S, PQ, OH-PQ and CQ were equally potent while 4 and 5 were 100 times less potent. CQ with two basic centres has a VAR of 143,482, while 4 and 5, with two basic centres of lower pK(a)s have VARs of 1287 and 1966. In contrast PQ and OH-PQ have four basic centres and achieve VARs of 104,378 and 19,874. This confirms the importance of VAR for potency against CQ-S parasites. Contrasting results were seen in CQ-R. 5, PQ and OH-PQ with LARs of 693; 973,492 and 398,118 (compared with 8.25 for CQ) showed similar potency in CQ-S and CQ-R. Importance of LAR for potency against CQ-R parasites probably reflects ability to block efflux by hydrophobic interaction with PfCRT but may relate to beta-haematin inhibition in vacuolar lipid.