scholarly journals RESPONSE OF SOD AND PHOSPHATE RELEASE RATE DUE TO STEP CHANGES IN DO CONCENTRATION AND FLOW VELOCITY

1999 ◽  
Vol 43 ◽  
pp. 1013-1018
Author(s):  
Tetsunori INOUE ◽  
Yoshiyuki NAKAMURA ◽  
Yoshihiko ADACHI
Keyword(s):  
Flow Velocity ◽  
Release Rate ◽  
Phosphate Release ◽  
Do Concentration

Effect of flow velocity on phosphate release from sediment

1994 ◽  
Vol 30 (10) ◽  
pp. 263-272 ◽  
Author(s):  
Yoshiyuki Nakamura
Keyword(s):  
Flow Velocity ◽  
Release Rate ◽  
Bulk Water ◽  
Low Flow ◽  
Limiting Factor ◽  
Phosphate Release ◽  
Release Flux ◽  
Diffusive Boundary ◽  
Do Concentration ◽  
Flow Velocities

A mathematical model of phosphate release rate from sediment, fp, is presented which determines the fp as a function of flow velocity over the sediment and dissolved oxygen concentration. Oxygen consumption in the sediment is expressed as the sum of chemical consumption due to ferrous iron oxygenation and the bacterial consumption which is assumed to be a first order reaction of oxygen. At very low flow velocities, transport through the diffusive boundary layer is the limiting factor of SOD, and phosphate release rate is expressed as a linear decreasing function of the velocity. When flow velocities are increased, both SOD and phosphate release rate become independent of velocity, since the reactions in the sediment are the rate limiting factor. The model suggests that phosphate release flux is a linear decreasing function of DO in the bulk water, while SOD is an increasing function of DO concentration. The critical DO concentration at which the phosphate release ceases is expressed in terms of the flow velocity. The prediction of SOD and ϕp by the present model is favourably compared with experiments by former researchers.

Non-steady variations of SOD and phosphate release rate due to changes in the quality of the overlying water

2000 ◽  
Vol 42 (3-4) ◽  
pp. 265-272 ◽  
Author(s):  
T. Inoue ◽  
Y. Nakamura ◽  
Y. Adachi
Keyword(s):  
Release Rate ◽  
Oxygen Demand ◽  
Phosphate Concentration ◽  
Sediment Oxygen Demand ◽  
Biochemical Reactions ◽  
Overlying Water ◽  
Phosphate Release ◽  
Do Concentration ◽  
The Difference

A dynamic model, which predicts non-steady variations in the sediment oxygen demand (SOD) and phosphate release rate, has been designed. This theoretical model consists of three diffusion equations with biochemical reactions for dissolved oxygen (DO), phosphate and ferrous iron. According to this model, step changes in the DO concentration and flow velocity produce drastic changes in the SOD and phosphate release rate within 10 minutes. The vigorous response of the SOD and phosphate release rate is caused by the difference in the time scale of diffusion in the water boundary layer and that of the biochemical reactions in the sediment. Secondly, a negative phosphate transfer from water to sediment can even occur under aerobic conditions. This is caused by the decrease in phosphate concentration in the aerobic layer due to adsorption.

scholarly journals Effect of the fuel-air flow velocity on heat release rate of swirling non-premixed methane flames

2019 ◽  
Vol 95 ◽  
pp. 105465 ◽  
Author(s):  
Kuanliang Wang ◽  
Fei Li ◽  
Pengfei Zou ◽  
Xin Lin ◽  
Ronghai Mao ◽  
...  
Keyword(s):  
Heat Release ◽  
Flow Velocity ◽  
Heat Release Rate ◽  
Release Rate ◽  
Air Flow ◽  
Methane Flames ◽  
Air Flow Velocity

Phosphate release from waste stabilisation pond sludge: significance and fate of polyphosphate

2011 ◽  
Vol 63 (8) ◽  
pp. 1689-1694 ◽  
Author(s):  
N. Powell ◽  
A. Shilton ◽  
S. Pratt ◽  
Y. Chisti
Keyword(s):  
Release Rate ◽  
Phosphorus Removal ◽  
Algal Bloom ◽  
Chemical Precipitation ◽  
Phosphorus Release ◽  
Common View ◽  
Phosphate Release ◽  
Initial Release ◽  
Polyphosphate Accumulation ◽  
The Common

Net phosphorus removal from waste stabilisation pond (WSP) systems is governed by the rate of phosphorus incorporation into the sludge layer and the rate of phosphorus release from this sludge back to the overlying wastewater. Luxury uptake of phosphorus by microalgae has been shown to occur under WSP conditions in the laboratory; however, the significance of this mechanism and the fate of polyphosphate contained in the settled solids have not previously been investigated. In this work the analysis of sludge samples from three WSP showed that up to 71% of the total phosphorus in the sludge was in the form of polyphosphate. This indicates that polyphosphate accumulation could potentially be an important mechanism for phosphorus sequestration in WSP and challenges the common view that chemical precipitation is the predominant phosphorus removal mechanism in these systems. The release of phosphate from WSP sludge samples was monitored in the laboratory. The samples from two different pond systems had release rates in the order of 4.3 μgP/gTSS.d. However, the third sample which was collected during an algal bloom had a release rate of 12.4 μgP/gTSS.d. Phosphate release from fresh microalgal sludge grown under laboratory conditions was also studied and was shown to have a release rate of 160 μgP/gTSS.d. Analysis of polyphosphate during the experiments on laboratory grown microalgal sludge showed that polyphosphate was indeed degraded resulting in phosphate release. Interestingly, after the initial release phase phosphorus was assimilated by the biomass and some polyphosphate was reformed. It is likely that this is due to bacterial growth in the sludge.

scholarly journals Sediment Phosphate Release Flux Under Hydraulic Disturbances in the Shallow Lake of Chaohu, China

2021 ◽  
Author(s):  
Wenguang LUO ◽  
Yao Yue ◽  
Jing Lu ◽  
Lina Pang ◽  
Senlin Zhu
Keyword(s):  
Shallow Lakes ◽  
Release Rate ◽  
Surface Sediment ◽  
Shallow Lake ◽  
Chaohu Lake ◽  
Small Motion ◽  
Phosphate Release ◽  
Wide Range ◽  
Sediment Phosphate ◽  
Motion Mode

Abstract Quantifying the effect of hydraulic disturbances on sediment phosphate release is a key issue in the water quality assessment of lakes, especially for the shallow lakes which are susceptible to winds and waves. Here, we sampled the original sediment columns from 12 positions in the eastern, central, and western areas of the Chaohu Lake, a representative shallow lake in China, and observed phosphate release under three levels of hydraulic disturbances in the laboratory. When the disturbance was weak and the surface sediment of bottom mud moved individually (the Individual Motion Mode), sediment phosphate release rate was insignificant (0.24 mg/m2/d). When the disturbance was medium and only a small percentage (<16%) of surface sediment started to move (the Small Motion Mode), phosphate release rate sharply increased to 4.81 mg/m2/d. When the disturbance was further strengthened and most (≥16%) of the surface sediment moved (the General Motion Mode), phosphate release rate was more than doubled (10.23 mg/m2/d). With the increase of hydraulic disturbance intensity, the variation range of phosphate release also became wider. Spatial distribution showed that the release rate varies the most in the western area, followed by the eastern and the central areas. By extrapolating the experimental results to the real scale, we found the phosphate release fluxes would probably fall within a wide range between 203.43 kg/d to 7311.01kg/d under different levels of hydrodynamic disturbances with considerably affects phosphate release from shallow lakes. This study also has implications for the pollutant management in other shallow lakes.

Identification of the adverse effect of nitrate on the phosphate release rate and improvement of EBPR process models

2006 ◽  
Vol 53 (4-5) ◽  
pp. 115-123 ◽  
Author(s):  
S.H. Lee ◽  
J.H. Ko ◽  
J.R. Kim ◽  
Y.J. Kim ◽  
J.J. Lee ◽  
...  
Keyword(s):  
Adverse Effect ◽  
Release Rate ◽  
Flow Reactor ◽  
Process Models ◽  
Sequential Reaction ◽  
Phosphate Release ◽  
Continuous Flow Reactor ◽  
Storage Rate ◽  
Nitrate Inhibition ◽  
Residual Nitrate

The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, KI,NO,PAO was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no phosphate release occurred with the existence of a little nitrate even though there was sufficient SCOD. It also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO3-4-P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process.

Sign in / Sign up

Export Citation Format

Share Document