Elevated Nitrite Occurrence in Biological Wastewater Treatment Systems

1985 ◽  
Vol 17 (2-3) ◽  
pp. 409-419 ◽  
Author(s):  
J. E. Alleman
Keyword(s):  
Wastewater Treatment ◽  
Oxygen Demand ◽  
Biological Wastewater Treatment ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Nitrite Toxicity ◽  
Chlorine Demand ◽  
Rate Limiting ◽  
Wastewater Treatment Systems ◽  
Initial Conversion

The initial conversion of ammonium to nitrite by Nitrosomonas has traditionally been regarded as the rate-limiting step for nitrification metabolism. This perspective implicitly assumes that subsequent oxidation of nitrite by Nitrobacter occurs more rapidly, and that NO2 concentrations are consequently maintained at low, sub-mg/L values. However, numerous bench- and full-scale nitrification systems have reportedly encountered elevated nitrite concentrations. Several concerns are generated by this circumstance, including: a) an increased chlorine demand, b) an increased effluent nitrogenous oxygen demand, c) potential nitrite toxicity, and d) possible nitrosamine formation. This paper consequently provides an overview of seven conditions which could lead to elevated nitrite occurrence in biological nitrification systems.

scholarly journals Bioaugmentation with Mixed Hydrogen-Producing Acetogen Cultures Enhances Methane Production in Molasses Wastewater Treatment

Archaea ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Shuo Wang ◽  
Jianzheng Li ◽  
Guochen Zheng ◽  
Guocheng Du ◽  
Ji Li
Keyword(s):  
Wastewater Treatment ◽  
Removal Rate ◽  
Oxygen Demand ◽  
Cod Removal ◽  
Anaerobic Wastewater Treatment ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Molasses Wastewater ◽  
Cod Removal Rate ◽  
Rate Limiting

Hydrogen-producing acetogens (HPA) have a transitional role in anaerobic wastewater treatment. Thus, bioaugmentation with HPA cultures can enhance the chemical oxygen demand (COD) removal efficiency and CH4yield of anaerobic wastewater treatment. Cultures with high degradation capacities for propionic acid and butyric acid were obtained through continuous subculture in enrichment medium and were designated as Z08 and Z12. Bioaugmentation with Z08 and Z12 increased CH4production by glucose removal to 1.58. Bioaugmentation with Z08 and Z12 increased the COD removal rate in molasses wastewater from 71.60% to 85.84%. The specific H2and CH4yields from COD removal increased by factors of 1.54 and 1.63, respectively. Results show that bioaugmentation with HPA-dominated cultures can improve CH4production from COD removal. Furthermore, hydrogen-producing acetogenesis was identified as the rate-limiting step in anaerobic wastewater treatment.

Modeling hydrolysis of slowly biodegradable organic compounds in biological nutrient removal activated sludge systems

2013 ◽  
Vol 67 (9) ◽  
pp. 2067-2074 ◽  
Author(s):  
J. Drewnowski ◽  
J. Makinia
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Nutrient Removal ◽  
Biological Nutrient Removal ◽  
Biological Wastewater Treatment ◽  
Important Process ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Activated Sludge Systems

Hydrolysis is an important process in biological wastewater treatment and is known to be the rate-limiting step in organic carbon removal from municipal or industrial wastewater. The influence of the readily biodegradable chemical oxygen demand fraction in biological wastewater treatment systems has been extensively investigated, but little is known about the effects of slowly biodegradable substrate (XS) on denitrification and enhanced biological phosphorus removal. The biodegradation of XS is initiated by hydrolysis, which is an integral part of activated sludge models, such as the Activated Sludge Model no. 2d (ASM2d). This process is slower than heterotrophic growth and thus becomes the rate-limiting step for the biodegradation of organic compounds. The aim of this study was to evaluate different concepts of modeling the hydrolysis process using the original and modified version of ASM2d. Batch test results obtained at a large biological nutrient removal (BNR) plant in Gdansk (Poland) provided an experimental database for comparison of the two model predictions. Both models were compared in terms of their predictions for the most important process rates in BNR activated sludge systems. In comparison with the orginal ASM2d, the modified model had no or only minor effect on the predicted nitrate utilization rate, phosphate release rate and anoxic/aerobic phosphate uptake rate, but better predicted the oxygen uptake rate. The average ARDs (average relative deviations) were 19.0 and 29.3% (original ASM2d) vs. 13.4 and 20.4% (modified ASM2d), respectively, for the settled wastewater without pretreatment and after coagulation–flocculation.

scholarly journals Is the 135S Poliovirus Particle an Intermediate during Cell Entry?

2000 ◽  
Vol 74 (18) ◽  
pp. 8757-8761 ◽  
Author(s):  
Yan Huang ◽  
James M. Hogle ◽  
Marie Chow
Keyword(s):  
Conformational Transition ◽  
Cell Entry ◽  
Wild Type ◽  
Cold Adapted ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
A Cell ◽  
Low Efficiency ◽  
Rate Limiting ◽  
Initial Conversion

ABSTRACT Poliovirus binding to its receptor (PVR) on the cell surface induces a conformational transition which generates an altered particle with a sedimentation value of 135S versus the 160S of the native virion. A number of lines of evidence suggest that the 135S particle is a cell entry intermediate. However, the low infection efficiencies of the 135S particle and the absence of detectable 135S particles during infection at 26°C by the cold-adapted mutants argue against a role for the 135S particle during the cell entry process. We show here that binding of 135S-antibody complexes to the Fc receptor (CDw32) increases the infectivity of these particles by 2 to 3 orders of magnitude. Thus, the low efficiency of infection by 135S particles is due in part to the low binding affinity of these particles. In addition, we show that there is an additional stage in the entry process that is associated with RNA release. This stage occurs after formation of the 135S particle, is rate limiting during infection at 37°C, but not at 26°C, and is PVR independent. The data also demonstrate that during infection at 26°C, the rate-limiting step is the PVR-mediated conversion of wild-type 160S particles to 135S particles. This suggests that during infection at 26°C by the cold-adapted viruses, 135S particles are formed, but they fail to accumulate to detectable levels because the subsequent post-135S particle events occur at a significantly faster rate than the initial conversion of 160S to 135S particles. These data support a model in which the 135S particle is an intermediate during poliovirus entry.

scholarly journals Reduction of Organic and Inorganic Pollutant from Waste Water by Algae

2014 ◽  
Vol 13 ◽  
pp. 1-8 ◽  
Author(s):  
Omprakash Sahu
Keyword(s):  
Wastewater Treatment ◽  
Conventional Treatment ◽  
Low Cost ◽  
Oxygen Demand ◽  
Biological Oxygen Demand ◽  
Biological Wastewater Treatment ◽  
Toxic Substances ◽  
Volatile Solid ◽  
Inorganic Pollutant ◽  
Wastewater Treatment Systems

Recently, algae have become significant organisms for biological purification of wastewater since they are able to accumulate plant nutrients, heavy metals, pesticides, organic and inorganic toxic substances and radioactive matters in their cells/bodies. Biological wastewater treatment systems with micro algae have particularly gained importance in last 50 years and it is now widely accepted that algal wastewater treatment systems are as effective as conventional treatment systems. These specific features have made algal wastewaters treatment systems an significant low-cost alternatives to complex expensive treatment systems particularly for purification of municipal wastewaters. By this method 70 % of biological oxygen demand, 66 % of chemical oxygen demand, 71 % total nitrogen, 67 % of phosphorus, 54 % volatile solid and 51 % of dissolved solid was reduced

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting
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