Hydrodynamics and oxygen balance in a high-rate algal pond

2000 ◽  
Vol 42 (10-11) ◽  
pp. 349-356 ◽  
Author(s):  
H. El Ouarghi ◽  
B. E. Boumansour ◽  
O. Dufayt ◽  
B. El Hamouri ◽  
J. L. Vasel
Keyword(s):  
Wastewater Treatment ◽  
Flow Rate ◽  
Oxygen Transfer ◽  
Plug Flow ◽  
High Rate ◽  
Oxygen Balance ◽  
Transfer Coefficients ◽  
Recirculation Flow ◽  
Hydrodynamic Parameters ◽  
Photosynthesis And Respiration

As for any other system used in wastewater treatment, it is important to know the mixing characteristics and net oxygen balance in high-rate algal ponds (HRAPs). The design of HRAPs obviously is conducive to plug flow, but with a large recirculation flow rate. The pond's treatment capacity will also depend on the net oxygen balance resulting from photosynthesis and respiration. In order to define an appropriate model describing the oxygen balance in the system, two techniques are respectively used for determining the hydrodynamic parameters and oxygen transfer coefficients of HRAPs.

Oxygen Supply Method Using Gas-Permeable Film for Wastewater Treatment

1993 ◽  
Vol 28 (7) ◽  
pp. 243-250 ◽  
Author(s):  
Y. Suzuki ◽  
S. Miyahara ◽  
K. Takeishi
Keyword(s):  
Wastewater Treatment ◽  
Energy Consumption ◽  
Oxygen Transfer ◽  
Transfer Rate ◽  
Oxygen Supply ◽  
Oxygen Transfer Rate ◽  
High Energy ◽  
High Rate ◽  
N Removal ◽  
High Energy Consumption

Gas-permeable film can separate air and water, and at the same time, let oxygen diffuse from the air to the water through the film. An oxygen supply method using this film was investigated for the purpose of reducing energy consumption for wastewater treatment. The oxygen transfer rate was measured for the cases with or without biofilm, which proved the high rate of oxygen transfer in the case with nitrifying biofilm which performed nitrification. When the Gas-permeable film with nitrifying biofilm was applied to the treatment of wastewater, denitrifying biofilm formed on the nitrifying biofilm, and simultaneous nitrification and denitrification occurred, resulting in the high rate of organic matter and T-N removal (7 gTOC/m2/d and 4 gT-N/m2/d, respectively). However, periodic sloughing of the denitrifying biofilm was needed to keep the oxygen transfer rate high. Energy consumption of the process using the film in the form of tubes was estimated to be less than 40% of that of the activated sludge process.

Comparison of oxygen and carbon dioxide balances in HRAP (high-rate algal ponds)

2003 ◽  
Vol 48 (2) ◽  
pp. 277-281 ◽  
Author(s):  
H. El Ouarghi ◽  
E. Praet ◽  
H. Jupsin ◽  
J.-L. Vasel
Keyword(s):  
Carbon Dioxide ◽  
Diurnal Variations ◽  
High Rate ◽  
Oxygen Balance ◽  
Oxygen Production ◽  
Tracer Gas ◽  
High Rate Algal Ponds ◽  
Hydrodynamic Study ◽  
Oxygen Production Rate ◽  
Photosynthesis And Respiration

We previously suggested a method to characterize the oxygen balance in High-Rate Algal Ponds (HRAPs). The method was based on a hydrodynamic study of the reactor combined with a tracer gas method to measure the oxygen transfer coefficient. From such a method diurnal variations of photosynthesis and respiration can be quantified and the net oxygen production rate determined. In this paper we propose a similar approach to obtain carbon dioxide balances in HRAPs. Then oxygen and carbon dioxide balances can be compared.

scholarly journals Global Internal Recirculation Alternative Operation to Reduce Nitrogen and Ammonia Limit Violations and Pumping Energy Costs in Wastewater Treatment Plants

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1606
Author(s):  
Ignacio Santín ◽  
Ramon Vilanova ◽  
Carles Pedret ◽  
Marian Barbu
Keyword(s):  
Wastewater Treatment ◽  
Flow Rate ◽  
Biological Treatment ◽  
Fuzzy Controller ◽  
Wastewater Treatment Plants ◽  
Nitrate Concentration ◽  
Great Influence ◽  
Energy Costs ◽  
Recirculation Flow ◽  
Operational Costs

The internal recirculation plays an important role in different areas of the biological treatment of wastewater treatment plants because it has a great influence on the concentration of pollutants, especially nutrients. A usual manipulation of the internal recirculation flow rate is based on the target of controlling the nitrate concentration in the last anoxic tank. This work proposes an alternative for the manipulation of the internal recirculation flow rate instead of nitrate control, with the objective of avoiding limit violations of nitrogen and ammonia concentrations and reducing operational costs. A fuzzy controller is proposed to achieve it based on the effects of the internal recirculation flow rate in different areas of the biological treatment. The proposed manipulation of the internal recirculation flow rate is compared to the application of the usual nitrate control in an already established and published operation strategy by using the internationally known benchmark simulation model no. 2 as a working scenario. The results show improvements with reductions of 59.40% in ammonia limit violations, 2.35% in total nitrogen limit violations, and 38% in pumping energy costs.

scholarly journals Vibratory membrane separation for wastewater treatment

2018 ◽  
Vol 14 (s1) ◽  
pp. 25-35
Author(s):  
Péter Bor ◽  
József Csanádi ◽  
Gábor Veréb ◽  
Sándor Beszédes ◽  
Zita Šereš ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Shear Rate ◽  
Flow Rate ◽  
Specific Energy ◽  
Membrane Fouling ◽  
Energy Demand ◽  
Membrane Separation ◽  
Permeate Flux ◽  
Recirculation Flow ◽  
Shear Rates

To meet the requirements defined by environmental protection regulations effective wastewater treatment is required to process effluents before discharging them into sewers or living waters. While membrane separation offers a quite advantageous method to reduce the organic load of wastewaters, membrane fouling is still limiting its application in wastewater treatment. In this study, the possibility of membrane fouling reduction by increased shear rates on the surface of the membrane was investigated. 7 and 10 kDa MWCO ultrafiltration and 240 Da nanofiltration membranes were studied, with the use of a laboratory mode Vibratory Shear Enhanced Processing. This work mostly focused on studying the effects of module vibration and recirculation feed flow rate on permeate flux, specific energy demand and membrane rejections. Using the same operation parameters, vibration and non-vibration mode experiments were carried out with high and low recirculation flow rate to have a deeper understanding of the shear rate effects. It can be concluded that higher shear rate had a positive effect on the process: increased shear rate resulted in higher flux, higher overall rejection values, as well as a significantly decreased specific energy demand. By calculating and comparing the shear rates in experiments with different operating parameters, both vibration and nonvibration mode, both low and high recirculation flow rate, we have reached the conclusion that vibration causes a significantly higher shear rate increase than setting the recirculation flow rate high.

Oxygen transfer and aeration efficiency - influence of diffuser submergence, diffuser density, and blower type

1998 ◽  
Vol 38 (3) ◽  
pp. 1-6 ◽  
Author(s):  
Martin R. Wagner ◽  
H. Johannes Pöpel
Keyword(s):  
Wastewater Treatment ◽  
Energy Consumption ◽  
Flow Rate ◽  
Oxygen Transfer ◽  
Wastewater Treatment Plants ◽  
Air Flow ◽  
Oxygen Absorption ◽  
Air Flow Rate ◽  
Fine Bubble ◽  
Aeration Efficiency

The main factors of fine bubble aeration systems in uniform arrangement in clean water are the air flow rate, the depth of submergence of the diffusers, and the diffuser density. While the influence of the air flow rate on the oxygen transfer parameters is known, knowledge of the influence of the depth of submergence and the diffuser density on the specific oxygen transfer efficiency SOTE [%/m] and on the specific oxygen absorption SOA [g/m3·m at STP] is very limited. Both parameters are of great importance in dimensioning fine bubble aeration systems. Therefore, a literature review was conducted to show the influence of the diffuser submergence and density and the type of blower on oxygen transfer and aeration efficiency. The main review results are, that higher values of specific oxygen absorption can be obtained at higher diffuser density; secondly, the volumetric oxygen transfer rate VOTR [g/m3·h] is higher with increasing depth of submergence at the same air flow rate. Also it can be stated that with greater depth of submergence the specific oxygen absorption [g/m3·m at STP] is reduced. Dependent on the air flow rate and the pressure head, the energy consumption [Wh/m3·m at STP] of the blowers used in wastewater treatment plants is different. For example, the energy consumption varies from 4.3 [Wh/m3·m at STP] (positive displacement blower) to 3.0 [Wh/m3·m at STP] (turbo-compressors) at a pressure of 10 m and an air flow rate of 5,000 m3/h at STP. From the results of the literature review the following conclusions can be drawn: (1) High specific oxygen absorption values (SOA) [g/m3·m at STP] can be achieved applying shallow tanks, high diffuser densities and low specific air flow rates; (2) High aeration efficiencies (AE) [kg/kWh] can be obtained by applying high volumetric oxygen transfer rates and adequate selection of the blowers used at the wastewater treatment plants.

scholarly journals Oxygen Transfer in Two-Stage Activated Sludge Wastewater Treatment Plants

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1964
Author(s):  
Maximilian Schwarz ◽  
Justus Behnisch ◽  
Jana Trippel ◽  
Markus Engelhart ◽  
Martin Wagner
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Oxygen Transfer ◽  
Pressure Loss ◽  
Wastewater Treatment Plants ◽  
High Rate ◽  
Ex Situ ◽  
Stormwater Treatment ◽  
Two Stage ◽  
Efficient Operation

Aeration is an energy-intensive process of aerobic biological treatment in wastewater treatment plants (WWTP). Two-stage processes enable energy-efficient operation, but oxygen transfer has not been studied in depth before. In this study, α-factors were determined with long-term ex situ steady-state off-gas measurements in pilot-scale test reactors (5.8 m height, 8.3 m3) coupled to full-scale activated sludge basins. A two-stage WWTP with more than 1 Mio population equivalent was studied over 13 months including rain and dry weather conditions. Operating data, surfactant concentrations throughout the two-stage process, and the effect of reverse flexing on pressure loss of diffusers were examined. The values of αmean, αmin, and αmax for design load cases of aeration systems were determined as 0.45, 0.33, and 0.54 in the first high-rate carbon removal stage and as 0.80, 0.69, and 0.91 in the second nitrification stage, respectively. The first stage is characterized by a distinct diurnal variation and decrease in α-factor during stormwater treatment. Surfactants and the majority of the total organic carbon (TOC) load are effectively removed in the first stage; hence, α-factors in the second stage are higher and have a more consistent diurnal pattern. Proposed α-factors enable more accurate aeration system design of two-stage WWTPs. Fouling-induced diffuser pressure loss can be restored effectively with reverse flexing in both treatment stages.

Deep Shaft High Rate Aerobic Digestion: Laboratory and Pilot Plant Performance

1981 ◽  
Vol 16 (1) ◽  
pp. 71-90 ◽  
Author(s):  
F. Tran ◽  
D. Gannon
Keyword(s):  
Retention Time ◽  
Oxygen Transfer ◽  
Pilot Plant ◽  
High Rate ◽  
Plant Performance ◽  
High Solids ◽  
Aerobic Digestion ◽  
Volatile Solids ◽  
Solids Content ◽  
High Solids Content

Abstract The Deep Shaft process, originating from ICI Ltd. in the U.K., has been further developed by C-I-L Inc., Eco-Technology Division into an extremely energy efficient, high rate biological treatment process for industrial and municipal wastewaters. The Deep Shaft is essentially an air-lift reactor, sunk deep in the ground (100 - 160 m): the resulting high hydrostatic pressure together with very efficient mixing in the shaft provide extremely high oxygen transfer efficiencies (O.T.E.) of up to 90% vs 4 to 20% in other aerators. This high O.T.E. suggests real potential for Deep Shaft technology in the aerobic digestion of sludges and animal wastes: with conventional aerobic digesters an O.T.E. over 8% is extremely difficult to achieve. This paper describes laboratory and pilot plant Deep Shaft aerobic digester (DSAD) studies carried out at Eco-Research's Pointe Claire, Quebec laboratories, and at the Paris, Ontario pilot Deep Shaft digester. An economic pre-evaluation indicated that DSAD had the greatest potential for treating high solids content primary or secondary sludge (3-7% total solids) in the high mesophilic and thermophilic temperature range (25-60°C) i.e. in cases where conventional digesters would experience severe limitations of oxygen transfer. Laboratory and pilot plant studies have accordingly concentrated on high solids content sludge digestion as a function of temperature. Laboratory scale daily draw and fill DSAD runs with a 5% solids sludge at 33°C with a 3 day retention time have achieved 34% volatile solids reduction and a stabilized sludge exhibiting a specific oxygen uptake rate (S.O.U.R.) of less than 1 mgO2/gVSS/hour, measured at 20°C. This digestion rate is about four times faster than the best conventional digesters. Using Eco-Research's Paris, Ontario pilot scale DSAD (a 160 m deep 8 cm diameter u-tube), a 40% reduction in total volatile solids, (or 73% reduction of biodegradable VS) and a final SOUR of 1.2 mg02/gVSS/hour have been achieved for a 4.6% solids sludge in 4 days at 33°C, with loading rates of up to 7.9 kg VSS/m3-day. Laboratory runs at thermophilic temperatures (up to 60°C) have demonstrated that a stabilized sludge (24-41% VSS reduction) can be produced in retention time of 2 days or less, with a resulting loading rate exceeding 10 kg VSS/m3-day.

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