Use of contact tank to enhance denitrification in oxidation ditches

1996 ◽  
Vol 34 (1-2) ◽  
pp. 195-202 ◽  
Author(s):  
X Hao ◽  
H. J. Doddema ◽  
J. W. van Groenestijn
Keyword(s):  
Carbon Sources ◽  
Organic Substrate ◽  
Adsorptive Capacity ◽  
Oxidation Ditch ◽  
Anoxic Zone ◽  
Time Zone ◽  
Floc Structure ◽  
N Removal ◽  
Denitrifying Microorganisms ◽  
Set Up

Poor denitrification in a Pasveeer oxidation ditch is attributed to a lack of carbon sources available in the anoxic zone as it is essential to maintain a high C/N ratio for denitrification. Influent of sewage directly into the anoxic zone is not useful to maintain a high C/N ratio. The adsorptive capacity of activated sludge can rapidly increase the C/N ratio. Similar to a contact-stabilization process, a contact tank can be combined with the Pasveer ditch; it provides contact time (zone) between raw sewage and return sludge before entering the ditch. In principle, insoluble organic substrate can be easily adsorbed onto the floc surfaces and enmeshed in the floc structure at a short retention time. After the contact, mixed influent is introduced into the anoxic zone. As a result, a high C/N ratio is obtained which enhances denitrification. Using this set up, the Pasveer ditch was operated. The experimental results show that the efficiency of denitrification has been enhanced from 45 to 83% for NO−3-N removal. The corresponding denitrification capacity of the sludge is increased by 240%. The contact tank has also the same principle as a ‘selector’ to control bulking sludge caused by filamentous bacteria. The SVI data and microscopic examination indicated improved settleability of the sludge. Further enhancement of denitrification needs an exact control of the dissolved oxygen level in the ditch and/or a concentration increase of denitrifying microorganisms.

Automatic monitoring of denitrification rates and capacities in activated sludge processes using fluorescence or redox potential

1998 ◽  
Vol 37 (12) ◽  
pp. 121-129 ◽  
Author(s):  
S. Isaacs ◽  
Terry Mah ◽  
S. K. Maneshin
Keyword(s):  
Biological Activity ◽  
Activated Sludge ◽  
Redox Potential ◽  
Treatment Plant ◽  
Automatic Monitoring ◽  
Organic Substrate ◽  
Anoxic Zone ◽  
Optimal Dosing ◽  
Denitrifying Microorganisms ◽  
Activated Sludge Processes

A novel method is described to automatically estimate several key parameters affecting denitrification in activated sludge processes: the nitrate concentration, the denitrification capacity, and the maximum (substrate unlimited) and actual denitrification rates. From these, the concentration of active denitrifying microorganisms and the quality of available organic substrate pool can be estimated. Additionally, a modification of the method allows the determination of the efficacy of various carbon substrates to enhance denitrification, and this can be used to determine optimal dosing rates of an external carbon source. The method is based on measurements of either fluorescence or redox potential (ORP) in an isolated mini-reactor, the Biological Activity Meter (BAM), situated in the anoxic zone of the wastewater treatment plant. Advantages of the method are that it is in situ, operating at the same temperature as in the measured anoxic zone, requires no pumps or pipes for mixed liquor sampling, consumes little or no reagents, and uses measurement signals which are instantaneous and low maintenance, one of which provides a direct measure of biological activity.

Denitrification in a Carbon and Nitrogen Removal System for Leachate Treatment: Performance of a Upflow Sludge Blanket (USB) Reactor

1999 ◽  
Vol 40 (8) ◽  
pp. 145-151 ◽  
Author(s):  
Liliana Borzacconi ◽  
Gisela Ottonello ◽  
Elena Castelló ◽  
Heber Pelaez ◽  
Augusto Gazzola ◽  
...  
Keyword(s):  
Complete System ◽  
Carbon Sources ◽  
Uasb Reactor ◽  
Leachate Treatment ◽  
N Removal ◽  
Start Up ◽  
Aerobic Reactor ◽  
C And N ◽  
Reactor Operating ◽  
Removal System

The performance of a bench scale upflow sludge bed (USB) denitrifying reactor was evaluated in order to integrate it into a C and N removal system for Sanitary Landfill Leachate. The raw leachate used presented COD and NH4-N average values of 30000 mg/l and 1000 mg/l, respectively. The complete system comprises in addition an UASB reactor and a nitrifying RBC. A portion of the aerobic reactor effluent was recycled into the denitrification stage and some raw leachate was also added as an additional C source. In order to obtain operating parameters the denitrifying reactor was operated alone. Sludge from an aerobic reactor (RBC) treating raw leachate was used as inoculum. Shortly after the start up, good granulation of the sludge bed was observed. Using raw leachate and UASB outlet as carbon sources with COD/NO3-N ratios of 4 and 12, respectively, denitrification efficiencies of about 90% were reached. A sludge yield of 0.16 gVSS/gCODremoved was obtained operating with raw leachate. For the anoxic reactor operating in the complete system, denitrification efficiencies of 90% were also achieved. A nitrogen gas recycle was a successful way to avoid frequently observed sludge bed rising problems.

scholarly journals Automatic controller to water plants

2010 ◽  
Vol 67 (6) ◽  
pp. 727-730 ◽  
Author(s):  
Leonardo Oliveira Medici ◽  
Hermes Soares da Rocha ◽  
Daniel Fonseca de Carvalho ◽  
Carlos Pimentel ◽  
Ricardo Antunes Azevedo
Keyword(s):  
Water Column ◽  
Large Scale ◽  
Low Cost ◽  
Organic Substrate ◽  
Domestic Water ◽  
Plastic Tube ◽  
Soil P ◽  
Set Up ◽  
Water Plants ◽  
Water Tension

Despite the massive demand of water for plant irrigation, there are few devices being used in the automation of this process in agriculture. This work evaluates a simple controller to water plants automatically that can be set up with low cost commercial materials, which are large-scale produced. This controller is composed by a ceramic capsule used in common domestic water filters; a plastic tube around 1.5 m long, and a pressostate used in domestic washing machines. The capsule and the pressostate are connected through the tube so that all parts are filled with water. The ceramic capsule is the sensor of the controller and has to be placed into the plant substrate. The pressostate has to be placed below the sensor and the lower it is, the higher is the water tension to start the irrigation, since the lower is the pressostate the higher is the water column above it and, therefore, the higher is the tension inside the ceramic cup to pull up the water column. The controller was evaluated in the control of drip irrigation for small containers filled with commercial organic substrate or soil. Linear regressions explained the relationship between the position of pressostate and the maximum water tension in the commercial substrate (p < 0.0054) and soil (p < 0.0001). Among the positions of the pressostate from 0.30 to 0.90 m below the sensor, the water tension changed from 1 to 8 kPa for commercial substrate and 4 to 13 kPa for the soil. This simple controller can be useful to grow plants, applying water automatically in function of the water tension of the plant substrate.

Dynamics of the anaerobic utilization of organic substrates in an anaerobic/aerobic sequencing batch reactor

1995 ◽  
Vol 31 (2) ◽  
pp. 35-43 ◽  
Author(s):  
A. Carucci ◽  
K. Lindrea ◽  
M. Majone ◽  
R. Ramadori
Keyword(s):  
Sequencing Batch Reactor ◽  
Batch Reactor ◽  
Large Population ◽  
Organic Substrate ◽  
Organic Substrates ◽  
Total Carbohydrate ◽  
Fermentation Products ◽  
Virtual Absence ◽  
Floc Structure ◽  
Filamentous Microorganisms

The operation of an anaerobic/aerobic Sequencing Batch Reactor (SBR) with synthetic feed (glucose as the sole organic substrate) demonstrated periods of non-EBPR and EBPR operation in the absence of polyhydroxy alkanoate (PHA) storage. The glucose added as feed disappeared rapidly (within 10 minutes) and none of the normal fermentation products were detected in the supernatant in either mode of operation. Anaerobic/aerobic batch trials using the biomass from the SBR were conducted to examine the processes taking place and a rapid uptake of glucose was confirmed and was accompanied by a fall in pH. The biomass also demonstrated that anaerobic PHB storage occurred when acetate feed was used. The biomass was characterized by a large population of “G” bacteria, the absence of filamentous microorganisms, compact floc structure and high total carbohydrate (ca 40% w/w). The supernatant was characterized by low COD, TOC and the virtual absence of the glucose substrate. The observations indicate that EBPR was possible under circumstances which are not consistent with accepted mechanisms.

Balancing yield, kinetics and cost for three external carbon sources used for suspended growth post-denitrification

2009 ◽  
Vol 60 (10) ◽  
pp. 2485-2491 ◽  
Author(s):  
Y. Mokhayeri ◽  
R. Riffat ◽  
S. Murthy ◽  
W. Bailey ◽  
I. Takacs ◽  
...  
Keyword(s):  
Wastewater Treatment Plants ◽  
Carbon Sources ◽  
The United States ◽  
Batch Reactors ◽  
Sequencing Batch Reactors ◽  
Process Step ◽  
Stringent Limit ◽  
Receiving Waters ◽  
Set Up

Facilities across North America are designing plants to meet stringent limit of technology (LOT) treatment for nitrogen removal. In the Mid-Atlantic region of the United States, this is in response to the Chesapeake Bay Agreement, which limit effluent total nitrogen discharges from wastewater treatment plants to between 3–5 mg/L. Since denitrification is crucial for the removal of nitrogen, maximizing this process step will result in a decrease in nutrient load to the receiving waters. Of particular interest is the use of an alternate external carbon source to replace the most commonly used carbon, methanol. Three external carbon sources were evaluated in this study including: methanol, ethanol and acetate at 13°C. The aim of this study was to evaluate the relative benefits and constraints for using these three carbon types. Laboratory scale Sequencing Batch Reactors (SBRs) were set up to grow and acclimate carbon free biomass to the specified substrate while in-situ Specific Denitrification Rates (SDNRs) were conducted concurrently. The results suggest that the SDNRs for acetate (31.0 ± 4.6 mgNO3-N/gVSS/hr) and ethanol (29.6 ± 5.6 mgNO3-N/gVSS/hr) are higher than that for methanol (10.1 ± 2.5 mgNO3-N/gVSS/hr). The yield coefficients in g COD/g COD were observed to follow a similar trend with values of 0.45 ± 0.05 for methanol, 0.53 ± 0.06 for ethanol and 0.66 ± 0.06 for acetate.

Sebatian Metoksiaromatik Sebagai Substrat Pertumbuhan dan Pengaruh Enzim Demetilase dalam Acetobacterium Woodii DSM 1030

2012 ◽  
Author(s):  
Mohd. Sahaid Hj. Kalil ◽  
Muhammad Zaki ◽  
Wan Mohtar Wan Yusoff ◽  
Mohammad Ramlan Mohd. Salleh
Keyword(s):  
Growth Rate ◽  
Steady State ◽  
Sole Carbon Source ◽  
Specific Growth ◽  
Chemostat Culture ◽  
Carbon Sources ◽  
Syringic Acid ◽  
Organic Substrate ◽  
Acetobacterium Woodii ◽  
Vanilic Acid

Penyelidikan ini bertujuan untuk menyaring substrat organik bagi untuk penghasilan sel–sel A. woodii teraruh demetilase. Pertumbuhan A. woodii dilakukan dalam medium “Balch” yang mengandungi sumber karbon berbeza dalam keadaan anaerobik. Sebanyak sebelas substrat telah diuji iaitu anisol, 2– dan 3–metoksifenol, asid vanilik, asid siringik, asid 2,3,4–, 2,4,5– dan 3,4,5–trimetoksi benzoik, 2,3,4–, 2,4,5– dan 3,4,5–trimetoksi benzil alkohol. 2–metoksifenol merupakan substrat terbaik untuk pertumbuhan A. woodii pada kadar pertumbuhan spesifik 0.14 j–1. Penghasilan sel–sel teraruh demetilase dilakukan dalam kultur kemostat pada kadar pencairan (D) 0.0j–1. Sel-sel pada keadaan mantap dituai dalam keadaan anaerobik dan dipekatkan sebelum digunakan. Pertumbuhan A. woodii didapati maksimum dengan menggunakan kepekatan 0.62 g/L 2–metoksifenol sebagai sumber karbon tunggal. Tindak balas penyahmetilan oleh sel–sel A. woodii meningkat sebanyak 78% apabila 2–metoksifenol sebanyak 0.31 g/L ditambah dalam medium yang mengandungi fruktosa (1% w/v) semasa kultur kemostat. Kata kunci: tindak balas penyahmetilan; demetilase; sel-sel tertuai; metosiaromatik, Acetobacteriumwoodii The objective of this project was to screen organic substrate suitable for the growth of A. woodii, and as for the production of demethylase. A. woodii was grown in “Balch” medium containing different carbon sources. Eleven substrates were tested including anisole, 2– and 3–methoxyphenol, vanilic acid, syringic acid, 2,3,4–, 2,4,5– and 3,4,5–trimethoxy benzoic acid and 2,3,4–, 2,4,5– and 3,4,5–trimethoxy benzyl alcohol. It was found that 2–methoxyphenol was the best substrate with a specific growth rate of 0.14 h–1. The production of demethylase induced cells was carried out in a chemostat culture at a dilution rate (D) of 0.08 h–1. Cells were harvested at steady state of growth and concentrated before use. Optimal concentration of 2–methoxvphenol as the sole carbon source was 0.62 g/L. Demethylation reaction of 0.31 g/L 2–methoxyphenol by induced culture increases 78% relative to the chemostat culture containing only fructose. Key words: Demethylation reaction; demethylase; harvested cells; methoxyaromatic; Acetobacteriumwoodii

scholarly journals Substrate-dependent CO2 fixation in heterotrophic bacteria revealed by stable isotope labelling

2020 ◽  
Vol 96 (6) ◽  
Author(s):  
Marina Spona-Friedl ◽  
Alexander Braun ◽  
Claudia Huber ◽  
Wolfgang Eisenreich ◽  
Christian Griebler ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Heterotrophic Bacteria ◽  
Tricarboxylic Acid Cycle ◽  
Carbon Sources ◽  
Organic Substrate ◽  
Gas Chromatography Mass Spectrometry ◽  
Logarithmic Phase ◽  
Natural Environments ◽  
Organic Substrates ◽  
Stable Isotope Labelling

ABSTRACT Virtually all heterotrophs incorporate carbon dioxide by anaplerotic fixation. Little explored, however, is the interdependency of pathways and rates of CO2fixation on the concurrent usage of organic substrate(s). Potentially, this could reveal which substrates out of a pool of dissolved organic carbon are utilised by environmental microorganisms. To explore this possibility, Bacillus subtilis W23 was grown in a minimal medium with normalised amounts of either glucose, lactate or malate as only organic substrates, each together with 1 g/L NaH13CO3. Incorporation of H13CO3− was traced by elemental analysis-isotope ratio mass spectrometry of biomass and gas chromatography-mass spectrometry of protein-derived amino acids. Until the late logarithmic phase, 13C incorporation into the tricarboxylic acid cycle increased with time and occurred via [4–13C]oxaloacetate formed by carboxylation of pyruvate. The levels of 13C incorporation were highest for growth on glucose and lowest on malate. Incorporation of 13C into gluconeogenesis products was mainly detected in the lactate and malate experiment, whereas glucose down-regulated this path. A proof-of-principle study with a natural groundwater community confirmed the ability to determine incorporation from H13CO3− by natural communities leading to specific labelling patterns. This underlines the potential of the labelling approach to characterise carbon sources of heterotrophic microorganisms in their natural environments.

Comparison of particulate pyrite autotrophic denitrification (PPAD) and sulfur oxidizing denitrification (SOD) for treatment of nitrified wastewater

2016 ◽  
Vol 75 (1) ◽  
pp. 239-246 ◽  
Author(s):  
Shuang Tong ◽  
Laura C. Rodriguez-Gonzalez ◽  
Chuanping Feng ◽  
Sarina J. Ergas
Keyword(s):  
Packed Bed ◽  
Product Formation ◽  
Electron Donors ◽  
Autotrophic Denitrification ◽  
Reduced Sulfur Compounds ◽  
N Removal ◽  
Sulfur Oxidizing ◽  
Reduced Sulfur ◽  
Carry Over ◽  
Set Up

The use of reduced sulfur compounds as electron donors for biological denitrification has the potential to reduce chemical and sludge disposal costs as well as carry-over of organic carbon to the effluent that often occurs with heterotrophic denitrification. Although a number of prior studies have evaluated sulfur oxidizing denitrification (SOD), no prior studies have evaluated particulate pyrite autotrophic denitrification (PPAD) in continuous flow systems. Bench-scale upflow packed bed reactors (PBRs) were set up to compare denitrification rates, by-product production and alkalinity consumption of PPAD and SOD. At an empty bed contact time of 2.9 h, average NO3−-N removal efficiencies were 39.7% and 99.9% for PPAD and SOD, respectively. Although lower denitrification rates were observed with PPAD than SOD, lower alkalinity consumption and reduced sulfur by-product formation (SO42−, S2− and SO32− plus S2O32−) were observed with PPAD. Furthermore, higher denitrification rates and lower by-product production was observed for SOD than in prior studies, possibly due to the media composition, which included sand and oyster shells. The results show that both pyrite and elemental sulfur can be used as electron donors for wastewater denitrification in PBRs.

Evaluation of a novel oxidation ditch system for biological nitrogen and phosphorus removal from domestic sewage

2010 ◽  
Vol 62 (8) ◽  
pp. 1745-1754 ◽  
Author(s):  
X. Chen ◽  
T. Fujiwara ◽  
K. Ohtoshi ◽  
S. Inamori ◽  
K. Nakamachi ◽  
...  
Keyword(s):  
Nitrogen Removal ◽  
Phosphorus Removal ◽  
Domestic Sewage ◽  
Control Technology ◽  
Oxidation Ditch ◽  
Anoxic Zone ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Do Control ◽  
Biological Nitrogen

A novel oxidation ditch system using anaerobic tanks and innovative dual dissolved oxygen (DO) control technology is proposed for biological nitrogen and phosphorus removal from domestic sewage. A continuous bench-scale experiment running for more than 300 days was performed to evaluate the system. Monitoring and controlling the airflow and recirculation flow rate independently using DO values at two points along the ditch permitted maintenance of aerobic and anoxic zone ratios of around 0.30 and 0.50, respectively. The ability to optimize aerobic and anoxic zone ratios using the dual DO control technology meant that a total nitrogen removal efficiency of 83.2–92.9% could be maintained. This remarkable nitrogen removal performance minimized the nitrate recycle to anaerobic tanks inhibiting the phosphorus release. Hence, the total phosphorus removal efficiency was also improved and ranged within 72.6–88.0%. These results demonstrated that stabilization of the aerobic and anoxic zone ratio by dual DO control technology not only resulted in a marked improvement of nitrogen removal, but it also enhanced phosphorus removal.

Era of Efficiency: New teaching models in a self-directed learning environment (Preprint)

2020 ◽  
Author(s):  
Kirsten Raphael ◽  
Shonnelly Novintan ◽  
Daniel Foran ◽  
Daniel Campioni-Norman
Keyword(s):  
Medical Schools ◽  
Time Zone ◽  
Self Directed Learning ◽  
Clinical Placements ◽  
The United Kingdom ◽  
School Teaching ◽  
Directed Learning ◽  
Logistical Difficulty ◽  
Set Up ◽  
Senior Students

UNSTRUCTURED During the COVID-19 lockdown, medical schools in the United Kingdom withdrew their students from clinical placements and delivered education and examinations via online platforms. The logistical difficulty of timetabling a multitude of clinicians, with many working busier rotas on the front lines, to give one-hour lectures delayed the delivery of medical education. During this delay, the United Hospitals (UH) Medgroup set up an online platform called TeachtoLondon that recruited doctors and senior students to deliver 10-minute tutorials. Even with medical school teaching having resumed, TeachtoLondon remains popular due to its efficient and bespoke model. The short tutorials made the content more accessible and, more importantly, more useful as a revision tool. Compared to a one-hour online lecture that lacks ‘virtual bookmarks’, a playlist of tutorials allows easy navigation for students to revisit difficult topics, a pivotal part of learning. Teachtolondon is also popular with tutors, as it facilitates participation in teaching despite reduced availability due to COVID redeployment. It also allowed recruitment of doctors internationally, who would have been prevented by time zone differences from giving live lectures. Lastly, the UH network allowed students from any of the London medical schools to request a tutorial topic. Topics were allocated to the large database of tutors, providing an efficient turnaround, which is flexibility that a medical school’s rigid curriculum does not allow. The TeachtoLondon project could be adapted as an effective teaching model that promotes digestible, bite-sized learning and provides uniform teaching to students, whilst simultaneously acting as a revision tool.

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