scholarly journals The role of food/microorganism ratio in denitrification reactors: how it affects the sizing and operation of the denitrification process

2021 ◽  
Vol 16 (1) ◽  
pp. 1
Author(s):  
Renato Gavasci ◽  
Francesco Lombardi ◽  
Massimo Raboni
Keyword(s):  
Dissolved Oxygen ◽  
Linear Dependence ◽  
Narrow Range ◽  
Sewage Treatment ◽  
Denitrification Rate ◽  
Sewage Treatment Plants ◽  
First Approximation ◽  
Denitrification Reactor ◽  
Denitrification Process

Two calculation models of the Specific Denitrification Rate (SDNR) are analyzed to highlight the sensitivity of this parameter to the Food:Microorganisms ratio in the denitrification reactor (F:MDEN). One of these models is empirical while the second was elaborated on a deterministic basis. Both models reveal a linear dependence of SDNR20°C on F:MDEN and in a first approximation they are comparable only in a narrow range of concentration of dissolved oxygen (DO) in denitrification, specifically DO=0.25-0.35 mg L-1. These values frequently occur in well designed and well operated sewage treatment plants. Outside this range, the role of F:MDEN must necessarily be examined in combination with DO because of the relevant influence of the latter on the efficiency of the denitrification process.

scholarly journals The Sensitivity of a Specific Denitrification Rate under the Dissolved Oxygen Pressure

2020 ◽  
Vol 17 (24) ◽  
pp. 9366
Author(s):  
Massimo Raboni ◽  
Paolo Viotti ◽  
Elena Cristina Rada ◽  
Fabio Conti ◽  
Maria Rosaria Boni
Keyword(s):  
Sensitivity Analysis ◽  
Dissolved Oxygen ◽  
Scientific Literature ◽  
Full Scale ◽  
Denitrification Rate ◽  
The Third ◽  
Small Influence ◽  
Denitrification Reactor ◽  
Activated Sludge Processes ◽  
Denitrification Process

The biological denitrification process is extensively discussed in scientific literature. The process requires anoxic conditions, but the influence of residual dissolved oxygen (DO) on the efficiency is not yet adequately documented. The present research aims to fill this gap by highlighting the effects of DO on the specific denitrification rate (SDNR) and consequently on the efficiency of the process. SDNR at a temperature of 20 °C (SDNR20°C) is the parameter normally used for the sizing of the denitrification reactor in biological-activated sludge processes. A sensitivity analysis of SNDR20°C to DO variations is developed. For this purpose, two of the main empirical models illustrated in the scientific literature are taken into consideration, with the addition of a deterministic third model proposed by the authors and validated by recent experimentations on several full-scale plants. In the first two models, SDNR20°C is expressed as a function of the only variable food:microrganism ratio in denitrification (F:MDEN), while in the third one, the dependence on DO is made explicit. The sensitivity analysis highlights all the significant dependence of SDNR20°C on DO characterized by a logarithmic decrease with a very pronounced gradient in correspondence with low DO concentrations. Moreover, the analysis demonstrates the relatively small influence of F:MDEN on the SDNR20°C and on the correlation between SDNR20°C and DO. The results confirm the great importance of minimizing DO and limiting, as much as possible, the transport of oxygen in the denitrification reactor through the incoming flows and mainly the mixed liquor recycle. Solutions to achieve this result in full-scale plants are reported.

Post-Denitrification with Controlled Feeding of Activated Sludge as H Donator

1990 ◽  
Vol 22 (7-8) ◽  
pp. 161-170
Author(s):  
I. Sekoulov ◽  
R. Addicks ◽  
J. Oles
Keyword(s):  
Activated Sludge ◽  
Sewage Treatment ◽  
Domestic Sewage ◽  
Trickling Filter ◽  
Sewage Treatment Plants ◽  
Effluent Quality ◽  
Second Stage ◽  
Denitrification Reactor ◽  
The Given ◽  
Complicated Configuration

Enlargement and/or upgrading of already existing sewage treatment plants will bring problems to design and operation. However, this can be solved even in some complicated configuration of the treatment system, as will be demonstrated. Having an activated sludge system for BOD removal (first stage) followed by a trickling filter for nitrification (second stage), denitrification of the effluent without an external H donator is hard to achieve. In domestic sewage treatment, denitrification is usually carried out with BOD as carbon source. Additionally to the principal question of pre- or post denitrification and the related effects on the effluent quality (BOD, COD, NH4) pre-denitrification in the given case would be highly ineffective and uneconomical (large hydraulic loads). The paper presents a system using thickened sludge from the activated sludge sedimentation as H donator. The sludge has been successfully used to denitrify the trickling filter effluent. For the design of the post-denitrification stage, the necessary volume of sludge could be determined together with the volume of the denitrification reactor. Results of the pilot-plant studies are presented.

scholarly journals Microplastic Abundance In Volga River: Results Of A Pilot Study In Summer 2020

2021 ◽  
Vol 14 (3) ◽  
pp. 82-93
Author(s):  
Anastasia A. Lisina ◽  
Maxim M. Platonov ◽  
Oleg I. Lomakov ◽  
Alexey A. Sazonov ◽  
Tatiana V. Shishova ◽  
...  
Keyword(s):  
Pilot Study ◽  
Sewage Treatment ◽  
Water Layer ◽  
Average Concentration ◽  
Volga River ◽  
Sewage Treatment Plants ◽  
Large Cities ◽  
Cheboksary Reservoir ◽  
Downstream Area

In order to analyze the problem of microplastics pollution a comprehensive environmental survey was conducted along the entire Volga river in summer of 2020. The analysis of 34 water samples allowed us to determine the average concentration of microplastic (MP) in the surface water layer of the Volga river which accounted for 0.90 items/m3 (0.21 mg/m3). MP particles were found in all samples taken. The concentrations ranged from 0.16 to 4.10 items/m3 (from 0.04 mg/m3 to 1.29 mg/m3). The maximum MP concentrations were recorded in large cities downstream of the sewage treatment plants. For Tver, Nizhny Novgorod, Kazan and Volgograd they reached 3.77, 1.91,4.10 and 1.34 items/m3 respectively. The key role of large settlements as sources of MP in the Volga water was revealed. The minimum MP concentrations were recorded upstream of the large cities showing relatively stable levels of 0.25 items/m3 (0.05 mg/m3). The lowest MP content (0.16 items/m3) was revealed in the downstream area of the Cheboksary reservoir near Cheboksary. The results of weighing MP particles showed that their average concentration in the Volga water is 0.21 mg/m3. In each of the investigated samples particles of three determined fractions - fragments, fibers and films - were found, however, their ratio was not constant. On average, the proportion of fragments and films in the Volga water was 41% and 37% respectively and share of fibers accounted for 22%.

Nitrogen removal capacity of simultaneously autotrophic and heterotrophic denitrification in a sewer receiving nitrified source-separated urine

2013 ◽  
Vol 8 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Feng Jiang ◽  
Zhen-Sheng Liang ◽  
Guo-Liang Peng ◽  
Jin Qian ◽  
Guang-Hao Chen
Keyword(s):  
Field Study ◽  
Nitrogen Removal ◽  
Removal Rate ◽  
Sewage Treatment ◽  
Calcium Nitrate ◽  
Denitrification Rate ◽  
Batch Tests ◽  
Denitrification Process ◽  
Heterotrophic Denitrification

Discharging source-separated and nitrified urine into sewer helps to save cost and space in biological nitrogen treatment as in-sewer denitrification is induced. This unique denitrification process may become complicated in sewers with sulfide contamination as simultaneously autotrophic and heterotrophic denitrification possibly occur but may compete each other for nitrate in oxidation of sulfide and organics. The objective of this study is to estimate the mixed denitrification rate in a sulfide-contaminated sewer when nitrified urine (mainly nitrite and nitrate) is discharged. In this study two investigations were conducted: (1) determination of the autotrophic, heterotrophic and mixed denitrification rates via lab batch tests and (2) determination of the total nitrogen removal rate in a 6.5-km long force main sewer via field study with calcium nitrate dosed at an average influent rate of 15.6 mg N/L. The lab tests determined the rates of autotrophic, heterotrophic and mixed denitrification at 0.36 ± 0.06, 6.54 ± 0.04 and 1.99 ± 0.1 mg N/L/h, respectively, while the field study estimated the total in-sewer denitrification rate at 2.32 mg N/L/h in the sewer when sulfide was present. Simultaneously autotrophic and heterotrophic denitrification was found when sewage was contaminated with sulfide. However, nitrogen removal rate of heterotrophic denitrification was 3.3 times higher that of the mixed denitrification process. The results indicate that discharging source-separated and nitrified urine into sewer is meaningful to decentralized sewage treatment, especially when sulfide is absent in the sewer.

Rapid evaluation of FDG imaging alternatives using head-to-head comparisons of full ring and gamma camera based PET scanners –

2002 ◽  
Vol 41 (05) ◽  
pp. 208-213 ◽  
Author(s):  
L. M. Haslinghuis-Bajan ◽  
L. Hooft ◽  
A. van Lingen ◽  
M. van Tulder ◽  
W. Devillé ◽  
...  
Keyword(s):  
Methodological Quality ◽  
Gamma Camera ◽  
First Generation ◽  
Prospective Evaluation ◽  
First Approximation ◽  
Variable Head ◽  
Malignant Lesions ◽  
The Impact ◽  
Pet Scanners

SummaryAim: While FDG full ring PET (FRPET) has been gradually accepted in oncology, the role of the cheaper gamma camera based alternatives (GCPET) is less clear. Since technology is evolving rapidly, “tracker trials” would be most helpful to provide a first approximation of the relative merits of these alternatives. As difference in scanner sensitivity is the key variable, head-to-head comparison with FRPET is an attractive study design. This systematic review summarises such studies. Methods: Nine studies were identified until July 1, 2000. Two observers assessed the methodological quality (Cochrane criteria), and extracted data. Results: The studies comprised a variety of tumours and indications. The reported GC- and FRPET agreement for detection of malignant lesions ranged from 55 to 100%, but with methodological limitations (blinding, standardisation, limited patient spectrum). Mean lesion diameter was 2.9 cm (SD 1.8), with only about 20% <1.5 cm. The 3 studies with the highest quality reported concordances of 74-79%, for the studied lesion spectrum. Contrast at GCPET was lower than that of FRPET, contrast and detection agreement were positively related. Logistic regression analysis suggested that pre-test indicators might be used to predict FRPET-GCPET concordance. Conclusion: In spite of methodological limitations, “first generation” GCPET devices detected sufficient FRPET positive lesions to allow prospective evaluation in clinical situations where the impact of FRPET is not confined to detection of small lesions (<1.5 cm). The efficiency of head-to-head comparative studies would benefit from application in a clinically relevant patient spectrum, with proper blinding and standardisation of acquisition procedures.

Changes of microbial indices of water quality in the Vistula and Brda rivers as a result of sewage treatment plant operation

2008 ◽  
Vol 37 (2) ◽  
Author(s):  
Maciej Walczak
Keyword(s):  
Water Quality ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Sewage Treatment Plants ◽  
Plant Operation ◽  
Treated Sewage ◽  
Microbiological Parameters ◽  
Microbial Indices

Changes of microbial indices of water quality in the Vistula and Brda rivers as a result of sewage treatment plant operationThis paper reports the results of studies of microbiological changes in the water quality of the Vistula and Brda rivers after the opening of sewage treatment plants in Bydgoszcz. The study involved determining the microbiological parameters of water quality. Based on the results obtained, it was found that the quality of the water in both rivers had improved decidedly after the opening of the plants, although an increased number of individual groups of microorganisms was found at the treated sewage outlet from one of the plants.

Spatial and Temporal Water Quality Trends in Severn Sound, Georgian Bay, since the Introduction of Phosphorus Control Guidelines: Nutrients and Phytoplankton, 1973 to 1991

1995 ◽  
Vol 30 (4) ◽  
pp. 565-592 ◽  
Author(s):  
A.F. Gemza
Keyword(s):  
Total Phosphorus ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Soluble Reactive Phosphorus ◽  
Euphotic Zone ◽  
Water Clarity ◽  
Sewage Treatment Plants ◽  
Order Of Magnitude ◽  
Phosphorus Levels

Abstract Severn Sound continues to exhibit signs of eutrophication despite initial identification of the problem in 1969 and the construction of several sewage treatment plants since then. In general, improvements in trophic state indicators have been marginal, suggesting that the sewage treatment plants have had limited success in controlling phosphorus concentrations. These discharges likely contributed to the increased total phosphorus levels and consequently the higher phytoplankton densities of the nearshore waters. Phytoplankton biovolumes were on average one order of magnitude higher than in the open waters of Lake Huron with mean summer biovolumes as high as 8.0 mm/L. Algal biovolumes were most dense in Penetang Bay, which experienced limited exchange with the main waters of the sound. No significant long-term trends were observed. Water clarity was declining significantly, however, at a rate of -0.60 to -0.78 m/year throughout the sound except in Sturgeon Bay. Total phosphorus levels were highly variable from year to year; however, concentrations from a 20-year perspective were declining in the open waters at a rate of 0.70 µg/L/year, but response was limited in nearshore areas. In Sturgeon Bay, mean annual euphotic zone total phosphorus as well as soluble reactive phosphorus levels declined by as much as 50% following the construction of a sewage treatment plant with tertiary treatment. Phytoplankton genera typical of eutrophic waters continued to dominate the algal assemblage but members indicative of mesotrophic conditions have become apparent in some areas of the sound.

Control of Bulking in an Extended Aeration Sewage Treatment Plant

1972 ◽  
Vol 7 (1) ◽  
pp. 13-20
Author(s):  
D.D.P. Cane ◽  
G.J. Farguhar
Keyword(s):  
Dissolved Oxygen ◽  
Control Measure ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Effective Control ◽  
Organic Loading Rate ◽  
Organic Loading ◽  
Mixed Liquor ◽  
Air Supply

Abstract A case of filamentous activated sludge bulking was investigated at an extended aeration plant treating wastes from a highway service centre. The purpose of the study was to find an effective control measure for the bulking and, if possible, to determine the cause of the bulking condition. Experiments were conducted to determine the effects upon bulking of: (a) a controlled copper dosage to the mixed liquor, (b) variations in the organic loading rate, and (c) maintenance of high and low dissolved oxygen concentrations in the mixed liquor. The microorganism responsible for the bulking condition was tentatively identified as Sphaerotilus natans. Extensive growths of these bacteria occurred in the sludge when the mixed liquor dissolved oxygen concentration dropped below 0.5 mg/1. Such dissolved oxygen levels had frequently occurred at this plant due to the use of timed aeration cycles and the use of insufficient air supply during peak loading periods. Variations in organic loading rates were found to have no adverse effect on sludge settleability. When bulking was slight, the condition could be improved by increasing the dissolved oxygen level to 1.5 mg/1, or more. The rate at which the filamentous growths could be eliminated from a highly filamentous sludge by increased aeration was very slow, but could be greatly increased by the simultaneous feeding of copper to the mixed liquor at a dosage rate of 1.0 mg/1, based on the raw sewage flows.

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