Modelling Dissolved Oxygen Depression in an Urban River in China (original) (raw)
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Annals of the New York Academy of Sciences, 2008
Water-quality modeling has been used as a support tool for water-resources management. The Streeter-Phelps (SP) equation is one often-used algorithm in river waterquality simulation because of its simplicity and ease in use. To characterize the river dissolved oxygen (DO) sag profile, it only considers that the first-order biological oxygen demand (BOD) degradation and atmospheric reaeration are the sink and source in a river, respectively. In the river water-quality calculation, the assumption may not always provide satisfactory simulation due to an inappropriate description of BOD degradation. In the study, various patterns of BOD degradation were combined with the oxygen reaeration to simulate the DO sag profile in a river. Different BOD degradation patterns used include the first-order decay, mixed second-order decay, and oxygen-inhibition decay. The results shows that the oxygen-inhibition SP equation calculates higher BOD and DO concentration, while the mixed second SP equation calculates the least among the three tested models. In river-water calculation of Keelung River, the SP and oxygeninhibition SP equations calculate similar BOD and DO concentrations, and the mixed second SP equation calculates the least BOD and DO concentration. The pollution loading of BOD and atmospheric reaeration constant are the two important factors that have significant impacts on aqueous DO concentration. In the field application, it is suggested that the mixed second SP equation be employed in water-quality simulation when the monitoring data exhibits a faster trend in BOD decay. The oxygen-inhibition SP equation may calculate the water quality more accurately when BOD decay is slower.
Dissolved oxygen dynamics of streams draining an urbanized and an agricultural catchment
Ecological Modelling, 2003
The extreme value method (EVM), based on the maximum and minimum dissolved oxygen (DO) deficits, was derived to estimate metabolism rates (photosynthesis and respiration) in streams. The proposed method was applied to DO concentrations that were measured in two creeks located in urbanized and agricultural watersheds, respectively. The results obtained by the EVM agree with the delta method used for the estimation of metabolism rates in streams. Diurnal DO variations were explained using a DO mass balance equation with the estimated daily metabolism rates. A comparison between the metabolism rates obtained in two creeks indicates that the creek located in a non-urban watershed has higher metabolism rates than the creek located in an urban watershed. The non-urban creek was periodically autotrophic, and the urban creek was heterotrophic during the measurement period. Simulations conducted by using 1-day metabolism rates and augmenting the basic DO mass balance equation with the dimensionless relationships between the metabolism rate and discharge in creeks followed actual diurnal DO concentrations measured in the streams. #
Modeling biochemical oxygen demand in a river with scattered storage zones
Applied Mathematical Sciences
Mathematical models have often been accepted as a useful tool to assess and manage water quality in water bodies. Dissolved Oxygen (DO), a surrogate variable for the general health of an aquatic ecosystem and Biochemical Oxygen Demand (BOD) are two important parameters to assess the level of pollution in river/stream. Various models developed to date accounts for only that portion of BOD which is in dissolved form and not the least in settleable form. These models also do not account for the storage zone in a scattered way in rivers and hence do not represents the actual situation caused by the discharge of partially treated/ untreated waste water, which contains a significant portion of BOD in settleable form, into the water body with a large width where the water becomes stagnant anywhere, due to rag/garbage in rivers. The present work represents a model to predict the concentration of total BOD when partially treated/untreated waste water is discharged into the river having staggered storage zones and thus address the above stated situation.
2002
Due to limited data and scarce financial resources in developing regions, policy decisions for managing water resources must often be made without a full understanding of what potential impacts on water quality may result. This study demonstrates a methodology for utilizing georeferenced statistical data to assess the primary pollution contributions and to model the physical impacts resulting from these contributions. Using socio-economic data on population, agricultural production and industrial output provides a basis for evaluating the potential effects on the current water quality situation and allows a method to assess the influences resulting from changes of these socio-economic patterns. This study focused on evaluating the current conditions in the Yellow River in China. A conceptual model is developed to estimate Biochemical Oxygen Demand (BOD) generation and link these sources with the hydrologic characteristics of the landscape to generate BOD loadings into the main river...
An oxygen equivalent model for water quality dynamics in a macrophyte dominated river
Ecological Modelling, 2003
A water quality modeling study was performed in a macrophyte dominated river. A computer model, MACRIV (macrophyte growing river) was formulated to incorporate diurnal dissolved oxygen variations and nutrient uptake/recycle caused by all aquatic plants, including macrophytes. In this model, the aquatic plant is represented as an equivalent amount of dissolved oxygen by reach, which varies diurnally as well as seasonally depending upon solar radiation, temperature, and nutrients. The solar radiation is computed in the model based on the latitude, Julian day, and real-time of day. The model simulates seven coupled state variables (BOD (CBOD or 5-day BOD), DO (daily average value or diurnal variation), organic nitrogen, ammonia nitrogen, nitrite/nitrate nitrogen, total organic phosphorus, dissolved inorganic phosphorus (DIP)) and two non-coupled variables (a first-order decay substance, and a conservative substance). Through a stoichiometric relationship between plant protoplasm and physiological processes including photosynthesis, respiration, and death, the water quality variables interacting with aquatic plants are computed in the model. The model was calibrated and verified against data collected from an impounded river in which macrophytes play an important role in defining water quality dynamics. There were reasonable agreements between model predictions and the field measurements both for steady-state water quality and diurnal dissolved oxygen. The overall study demonstrated that the developed MACRIV model can simulate the most important parameters involved in waste load allocation studies in macrophyte growing rivers, such as diurnal DO variation, BOD (autochtonous and allochtonous), ammonia toxicity, and nutrient dynamics.
Multi-scale modeling of nutrient pollution in the rivers of China
Environmental Science & Technology
Chinese surface waters are severely polluted by nutrients. This study addresses three challenges in nutrient modeling for rivers in China: (1) difficulties in transferring modeling results across biophysical and administrative scales, (2) poor representation of the locations of point sources, and (3) limited incorporation of the direct discharge of manure to rivers. The objective of this study is, therefore, to quantify inputs of nitrogen (N) and phosphorus (P) to Chinese rivers from different sources at multiple scales. We developed a novel multi-scale modeling approach including a detailed, state-of-the-art representation of point sources of nutrients in rivers. The model results show that the river pollution and source attributions differ among spatial scales. Point sources accounted for 75% of the total dissolved phosphorus (TDP) inputs to rivers in China in 2012, and diffuse sources accounted for 72% of the total dissolved nitrogen (TDN) inputs. One-third of the sub-basins accounted for more than half of the pollution. Downscaling to the smallest scale (polygons) reveals that 14% and 9% of the area contribute to more than half of the calculated TDN and TDP pollution, respectively. Sources of pollution vary considerably among and within counties. Clearly, multi-scale modeling may help to develop effective policies for water pollution.
The level of contamination in surface water has been a major concern to society in the reduction of oxygen in the water bodies. This study was carried out to test and validate a developed model of dissolved oxygen with time (days) in urban waterfronts. Water samples were collected at Bonny and Okirika waterfronts in Port Harcourt, Rivers State, Nigeria. This was taken at different times, depths, and distances along the river, in both dry and rainy seasons. The biological oxygen demand (BOD) and dissolved oxygen (DO) of the water samples were analyzed according to APHA-51210B. The model was validated by simulating the experimental results into the equation, and with coefficient determination (r 2). The results of the analysis showed that dissolved oxygen (DO) in the creeks in the presence of oxygen-consuming pollutants in the creeks depleted the DO concentration, which attained saturation after 30 days. The saturation with DO value approximately 7.2mg/l. however, from 80 to 100 days, deficit was almost insignificant with values recorded between 4.9x10-6 mg/l and 3.5x10-6 mg/l for the two creeks across the seasons. The experimental results were simulated into the prediction model. The developed model showed good agreement between measured and predicted results with high coefficient of determination. Thus, suggesting that the model be used for predicting dissolved oxygen with time in the waterfronts.