Oxygen Depletion Modelling, Port Shelter, Hong Kong

1986 ◽  
Vol 18 (7-8) ◽  
pp. 277-287
Author(s):  
J. Krogsgaard Jensen ◽  
A. Malmgren-Hansen ◽  
P. Mortensen
Keyword(s):  
Organic Matter ◽  
Hong Kong ◽  
Decay Rate ◽  
Oxygen Concentration ◽  
Dispersion Model ◽  
Vertical Mixing ◽  
Oxygen Demand ◽  
Bottom Layer ◽  
Oxygen Depletion ◽  
Sensitivity Analyses

In order to describe and evaluate the effect on the oxygen concentrations of a planned sewage outlet in the Port Shelter Bay in Hong Kong, a relatively simple BOD-DO-box model has been established. The model describes the oxygen concentration in 6 horizontal boxes in the central part of Port Shelter. Each box is vertically divided into 4 layers (sub-boxes). The oxygen concentration in each layer is described as a function of the vertical and the horizontal mixing, the oxygen demand of the sediment and the concentration of organic matter in the water. A finite difference transport dispersion model provided input data for the BOD-DO model. Two main calculations have been made: one simulating the cold season (15°C) and one simulating the warm season (30°C). Furthermore sensitivity analyses have been carried out. The calculations show an oxygen depletion of approximately 1 and 2 mg O2/l at 15° and 30°C respectively in the bottom layer over an area of approximately two sq. km. The highest oxygen depletion is calculated in the bottom layer. From the calculation it can further be concluded that the decay rate of organic matter in the water and the vertical mixing will influence the oxygen depletion considerably. In periods where either the decay rate is higher than 3 d−1, or the vertical mixing is considerably low an oxygen depletion higher than the calculated can be expected. The lowest measured oxygen concentration in Port Shelter during the period July-August 1982 was 1.7 mg O2/l. Therefore it can be expected that the planned outlet will cause oxygen-free or nearly oxygen-free conditions in the bottom layer in warm periods with low vertical mixing.

scholarly journals Oxygen Depletion in the Kattegat

1985 ◽  
Vol 16 (4) ◽  
pp. 237-256 ◽  
Author(s):  
T.S. Jacobsen ◽  
N.-E. Ottesen Hansen
Keyword(s):  
Lower Layer ◽  
Saline Water ◽  
Vertical Mixing ◽  
Oxygen Demand ◽  
Simple Calculation ◽  
Oxygen Depletion ◽  
Time Step ◽  
Meteorological Forcing ◽  
First Order ◽  
Model Driven

A mathematical model driven by meteorological forcing and sea level differences has been established in order to describe the water exchange and vertical mixing in the Kattegat and Samsø Belt. The model has been run with a time-step of 1 day for the period April - October from 1961 to 1981. The mixing has been represented by equations from the theory of turbulence with the normally used coefficients, i.e. no calibration has been necessary. Results from earlier investigations have been used to describe the flows in the Belts and the Sound. The vertical exchange between the upper, brackish and the lower, saline water is strongly dependent on the meteorology. A small meteorological activity results in small exchange flows which implies that the oxygen supply to the lower layer becomes smaller and unfavourable biological conditions may occur. A simple calculation has been carried out on the assumption that the chemical and biological oxygen demand is a first order process with a time scale for the oxygen decay, which is halfed for each 10° increase of temperature. Thus the model describes the effect of the meteorological activity on the oxygen concentration, all other parameters kept constant.

scholarly journals Seasonal Stratification and Biogeochemical Turnover in the Freshwater Reach of a Partially Mixed Dredged Estuary

2021 ◽  
Vol 8 ◽  
Author(s):  
Johannes Pein ◽  
Annika Eisele ◽  
Tina Sanders ◽  
Ute Daewel ◽  
Emil V. Stanev ◽  
...  
Keyword(s):  
Organic Matter ◽  
Vertical Mixing ◽  
Three Dimensional ◽  
Oxygen Depletion ◽  
Biogeochemical Model ◽  
Elbe Estuary ◽  
Ecological Processes ◽  
Ammonium Accumulation ◽  
Bottom Oxygen ◽  
Organic Particles

The Elbe estuary is a substantially engineered tidal water body that receives high loads of organic matter from the eutrophied Elbe river. The organic matter entering the estuary at the tidal weir is dominated by diatom populations that collapse in the deepened freshwater reach. Although the estuary’s freshwater reach is considered to manifest vertically homogenous density distribution (i.e., to be well-mixed), several indicators like trapping of particulate organic matter, near-bottom oxygen depletion and ammonium accumulation suggest that the vertical exchange of organic particles and dissolved oxygen is weakened at least temporarily. To better understand the causal links between the hydrodynamics and the oxygen and nutrient cycling in the deepened freshwater reach of the Elbe estuary, we establish a three-dimensional coupled hydrodynamical-biogeochemical model. The model demonstrates good skill in simulating the variability of the physical and biogeochemical parameters in the focal area. Coupled simulations reveal that this region is a hotspot of the degradation of diatoms and organic matter transported from the shallow productive upper estuary and the tidal weir. In summer, the water column weakly stratifies when at the bathymetric jump warmer water from the shallow upper estuary spreads over the colder water of the deepened mid reaches. Enhanced thermal stratification also occurs also in the narrow port basins and channels. Model results show intensification of the particle trapping due to the thermal gradients. The stratification also reduces the oxygenation of the near-bottom region and sedimentary layer inducing oxygen depletion and accumulation of ammonium. The study highlights that the vertical resolution is important for the understanding and simulation of estuarine ecological processes, because even weak stratification impacts the cycling of nutrients via modulation of the vertical mixing of oxygen, particularly in deepened navigation channels and port areas.

Investigation of the Contribution of Natural Organic Runoff to Dissolved Oxygen Depletion in the Red Deer River

1979 ◽  
Vol 14 (1) ◽  
pp. 71-88
Author(s):  
S.E. Penttinen ◽  
P.H. Bouthillier ◽  
S.E. Hrudey
Keyword(s):  
Dissolved Oxygen ◽  
Red Deer ◽  
Stream Water ◽  
Oxygen Demand ◽  
Oxygen Depletion ◽  
Experimental Program ◽  
Nitrogen Budgets ◽  
Carbon And Nitrogen ◽  
Tributary Stream ◽  
Small Tributary

Abstract Studies on the chronic low dissolved oxygen problems encountered under winter ice in the Red Deer River have generally been unable to account for dissolved oxygen depletion in terms of known manmade inputs. An experimental program was developed to assess the possible nature and approximate bounds of oxygen demand due to natural organic runoff carried to the Red Deer River by a small tributary stream, the Blindman River. The study employed an electrolytic respirometer on stream water samples subjected to prior concentration by vacuum evaporation. Evaluation of carbon and nitrogen budgets in conjunction with the measured oxygen demand indicate that biochemical oxygen demand is originating with natural organic runoff in tributaries of the Red Deer River. The results provide a basis for estimation of the possible contribution to the observed oxygen demand in the Red Deer River originating from natural organic runoff.

scholarly journals Treatment of fish processing industry wastewater using hydrodynamic cavitational reactor with biodegradability improvement

2019 ◽  
Vol 80 (12) ◽  
pp. 2310-2319 ◽  
Author(s):  
Prashant Dhanke ◽  
Sameer Wagh ◽  
Abhijeet Patil
Keyword(s):  
Organic Matter ◽  
New Technology ◽  
Oxygen Demand ◽  
Operating Conditions ◽  
Hydrodynamic Cavitation ◽  
Inlet Pressure ◽  
Fish Processing ◽  
Processing Industry ◽  
Cavitation Effect ◽  
Processing Plants

Abstract Water generated from the fish processing industry is contaminated with organic matter. This organic matter present in wastewater increases the biochemical oxygen demand (BOD) and chemical oxygen demand (COD). A new technology, hydrodynamic cavitation (HC) is used to deal with this wastewater produced in fish processing plants. The orifice plate is used in the HC reactor to generate a cavitation effect. The intensification of this technique was carried out with the help of hydrogen peroxide (H2O2) and TiO2. The treatment of this wastewater is reported in terms of percent degradation in BOD and COD and in biodegradability index (BI). Operating parameters like inlet pressure, pH, operating temperature and H2O2 doses were used to find the optimum condition. 15 g/L of H2O2 gave 69.5% reduction of COD in the 120 min of treatment that also increases BI value to 0.93 at inlet pressure 8 bar, Plate-5, temperature (30 °C), and pH 4. In the ultrasonic cavitation (UC) reactor, COD reduction is 68.7% without TiO2 and with TiO2 it is 71.2%. Also, this HC and UC reactor reduced CFU count to a great extent at the same operating conditions.

scholarly journals Simultaneous nitrate and organic matter removal from a dairy effluent by biodenitrification

2018 ◽  
Vol 31 (2) ◽  
pp. 97-107
Author(s):  
Ahmed Hamdani ◽  
Mohammed Mountadar ◽  
Omar Assobhei
Keyword(s):  
Organic Matter ◽  
Chemical Oxygen Demand ◽  
Electron Donor ◽  
High Efficiency ◽  
Oxygen Demand ◽  
Nitrite Accumulation ◽  
Simultaneous Removal ◽  
Optimal Conditions ◽  
Dairy Effluent ◽  
Organic Removal

In order to study the simultaneous removal of nitrate and organic matter from a dairy effluent containing 670 mg∙L-1 of nitrate (NO3--N) and 5 760 mg∙L-1 of dissolved chemical oxygen demand (CODd), denitrification in a laboratory scale bioreactor consisting of an immersed bacterial bed colonized by an heterotrophic denitrifying flora (HDF) selected for NO3- reduction, COD consumption and adapted to grow on an effluent produced by a dairy industry was investigated. The obtained results indicated that at the optimal conditions of temperature (30°C), pH (7), COD/NO3--N ratio (5), the operation lasted 108h with total reduction of nitrate in 72h, no nitrite accumulation, and 92% of soluble COD removal in 96h. This indicates that the biodenitrification was accompanied with a high efficiency of matter organic removal as an electron donor, and thereby satisfies the applicable standards.

Electricity generation through a photo sediment microbial fuel cell using algae at the cathode

2017 ◽  
Vol 76 (12) ◽  
pp. 3269-3277 ◽  
Author(s):  
B. Neethu ◽  
M. M. Ghangrekar
Keyword(s):  
Power Generation ◽  
Organic Matter ◽  
Microbial Fuel Cells ◽  
Carbon Capture ◽  
Algal Growth ◽  
Oxygen Demand ◽  
Sediment Organic Matter ◽  
Overlying Water ◽  
Organic Matter Removal ◽  
Removal Efficiencies

Abstract Sediment microbial fuel cells (SMFCs) are bio-electrochemical devices generating electricity from redox gradients occurring across the sediment–water interface. Sediment microbial carbon-capture cell (SMCC), a modified SMFC, uses algae grown in the overlying water of sediment and is considered as a promising system for power generation along with algal cultivation. In this study, the performance of SMCC and SMFC was evaluated in terms of power generation, dissolved oxygen variations, sediment organic matter removal and algal growth. SMCC gave a maximum power density of 22.19 mW/m2, which was 3.65 times higher than the SMFC operated under similar conditions. Sediment organic matter removal efficiencies of 77.6 ± 2.1% and 61.0 ± 1.3% were obtained in SMCC and SMFC, respectively. With presence of algae at the cathode, a maximum chemical oxygen demand and total nitrogen removal efficiencies of 63.3 ± 2.3% (8th day) and 81.6 ± 1.2% (10th day), respectively, were observed. The system appears to be favorable from a resources utilization perspective as it does not depend on external aeration or membranes and utilizes algae and organic matter present in sediment for power generation. Thus, SMCC has proven its applicability for installation in an existing oxidation pond for sediment remediation, algae growth, carbon conversion and power generation, simultaneously.

scholarly journals Long residence times of rapidly decomposable soil organic matter: application of a multi-phase, multi-component, and vertically-resolved model (TOUGHREACTv1) to soil carbon dynamics

2014 ◽  
Vol 7 (1) ◽  
pp. 815-870 ◽  
Author(s):  
W. J. Riley ◽  
F. M. Maggi ◽  
M. Kleber ◽  
M. S. Torn ◽  
J. Y. Tang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Reactive Transport ◽  
Lignin Content ◽  
Sensitivity Analyses ◽  
Rooting Depth ◽  
Carbon Substrate ◽  
Advective Transport ◽  
Turnover Rates ◽  
Multi Phase

Abstract. Accurate representation of soil organic matter (SOM) dynamics in Earth System Models is critical for future climate prediction, yet large uncertainties exist regarding how, and to what extent, the suite of proposed relevant mechanisms should be included. To investigate how various mechanisms interact to influence SOM storage and dynamics, we developed a SOM reaction network integrated in a one-dimensional, multi-phase, and multi-component reactive transport solver. The model includes representations of bacterial and fungal activity, multiple archetypal polymeric and monomeric carbon substrate groups, aqueous chemistry, aqueous advection and diffusion, gaseous diffusion, and adsorption (and protection) and desorption from the soil mineral phase. The model predictions reasonably matched observed depth-resolved SOM and dissolved organic carbon (DOC) stocks in grassland ecosystems as well as lignin content and fungi to aerobic bacteria ratios. We performed a suite of sensitivity analyses under equilibrium and dynamic conditions to examine the role of dynamic sorption, microbial assimilation rates, and carbon inputs. To our knowledge, observations do not exist to fully test such a complicated model structure or to test the hypotheses used to explain observations of substantial storage of very old SOM below the rooting depth. Nevertheless, we demonstrated that a reasonable combination of sorption parameters, microbial biomass and necromass dynamics, and advective transport can match observations without resorting to an arbitrary depth-dependent decline in SOM turnover rates, as is often done. We conclude that, contrary to assertions derived from existing turnover time based model formulations, observed carbon content and δ14C vertical profiles are consistent with a representation of SOM dynamics consisting of (1) carbon compounds without designated intrinsic turnover times, (2) vertical aqueous transport, and (3) dynamic protection on mineral surfaces.

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