Dissolved oxygen sag analysis for a settling fields overlapping type multi-wastewater-outfall

The classical Streeter–Phelps models for Dissolved oxygen (DO) sag do not account for a significantly settleable portion (about 10% in treated to about 60% in the untreated wastewater discharged) of the total biochemical oxygen demand (BOD) inputs into rivers through wastewater outfalls, and therefore, they can not be used to predict the DO sag to any accuracy and rationality. The author’s rationally composited model for an accurate prediction of stream BOD, accounting for near linear removal of settleable BOD as well as simultaneous exponential decay of the non-settleable BOD, is used to predict the DO sag resulting from a multi-wastewater-outfall system, wherein the settling fields of some of the outfalls interfere and overlap. An illustrative case example has been presented to demonstrate use of the models evolved under varying locations of the multi-wastewater-outfalls. A universal and integrated PC based computer program can also be evolved for the computation of the overall resultant DO sag to confirm the manually computed DO sag.     

Comparative Evaluation of Three River Water Quality Models1

Abstract: Selection of a biochemical oxygen demand (BOD) reaction model to incorporate into dissolved oxygen (DO) water quality models is an overlooked choice available to river water quality modelers. Data from rivers can serve in screening methods to discriminate between competing water quality models. In this study, 15 published BOD and DO datasets based on a 7 year long study of the Bormida River in Italy are used to calibrate three‐multiorder BOD models: first‐order, three‐halves order, and second‐order, which are then included in three corresponding DO models which incorporate these BOD models. The adequacy of the first‐order, three‐halves order and second‐order BOD models was evaluated by calculating the root mean square error between a model and data. A similar procedure was followed to evaluate three DO models, each of which incorporated one of the three BOD models. The first‐order BOD model most frequently fit the river data best, followed by the three‐halves order and the second‐order BOD models. The DO model incorporating a first‐order BOD model most frequently fit the data best, followed by the DO order incorporating second‐order BOD and the DO model incorporating three‐halves order BOD.     

REGIONAL WATER QUALITY MANAGEMENT BY THE GENERALIZED REDUCED GRADIENT METHOD1

ABSTRACT: A river basin-wide water quality management system is considered. The river receives thermal as well as organic wastes. At-source treatment of these pollutants is imposed to control the basin-wide water quality. The related water quality standards are: the minimum DO concentration, the maximum allowable BOD concentration, the maximum allowable stream temperature, and the allowable rise in stream temperature. The general dynamic mathematical model representing water quality in streams and the thermal effects on BOD and DO concentrations is presented. The model is highly nonlinear in nature. The optimal management problem involving the model is solved by a recently developed nonlinear propgramming technique - the generalized reduced gradient (GRG) method. Comparison of results obtained by the GRG method vs. dynamic programming, and of results using a more realistic mathematical model vs. a simple model are presented. The analysis procedure can be applied to designing new and examining existing water quality programs, and to study the influence of alternate policies and constraints.     

PROBABILISTIC METHODS IN STREAM QUALITY MANAGEMENT1

ABSTRACT. Recent advances in water quality modelling have pointed out the need for stochastic models to simulate the probabilistic nature of water quality. However, often all that is needed is an estimate of the uncertainty in predicting water quality variables. First order analysis is a simple method of providing an estimate in the uncertainty in a deterministic model due to uncertain parameters. The method is applied to the simplified Streeter-Phelps equations for DO and BOD; a more complete Monte Carlo simulation is used to check the accuracy of the results. The first order analysis is found to give accurate estimates of means and variances of DO and BOD up to travel times exceeding the critical time. Uncertainty in travel time and the BOD decay constant are found to be most important for small travel times; uncertainty in the reaeration coefficient dominates near the critical time. Uncertainty in temperature was found to be a negligible source of uncertainty in DO for all travel times.     

DIGITAL SIMULATION OF THE EFFECT OF THERMAL DISCHARGE ON STREAM WATER QUALITY1

A modified transient version of the Streeter-Phelps model along with the energy balance equation is employed to analyze the effects of waste heat discharge from power plants on stream water quality. Analysis is also made to examine the effects of the upstream water quality and stream velocity on the downstream DO concentration level. The resulting coupled nonlinear hyperbolic partial differential equations representing the energy, BOD and DO concentrations are solved by the method of characteristics and simulated on a digital computer. Final numerical results indicate that the allowable quantity of thermal discharge does heavily depend on the upstream quality.     

DISPERSION MODEL FOR A STREAM WITH SEVERAL WASTE INPUTS AND WATER INTAKES1

An analytical solution is developed to predict the BOD and DO profiles in a stream having several outfalls of waste and intakes of water. The model also incorporates continuous addition and removal of BOD and DO along the stream. A steady state one dimensional dispersion model is used to describe the transport of BOD and DO in a stream. Changes in stream properties along the length are considered by dividing the stream into several segments and changing the parameters of the BOD and DO equations as needed in each segment. By applying continuity equations at the boundaries of these segments and equilibrium conditions at either ends of the infinitely long stream, the arbitrary constants in the solutions to the differential equations for BOD and DO can be determined. Some applications of the results in studying water pollution problems are illustrated.     

WATER QUALITY CONTROL BY ARTIFICIAL AERATION OF STREAM RECEIVING THERMAL AND ORGANIC WASTE DISCHARGES1

ABSTRACT: The purpose of this work is to study the installation of artificial aerators for water quality control of a stream which receives thermal and organic waste discharges. The location and numer of diffuser type aerators to be installed along the stream are determined so as to maintain the stream DO content above a certain minimum requirement (4 mg/l or 5 mg/l) for normal aquatic life. Effects of the stream velocity, upstream BOD concentration and rates of thermal and organic waste discharges to the stream are examined.     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN THE PIRACICABA RIVER BASIN,BRAZIL1

ABSTRACT: The spatial and temporal variability of dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrate concentration and total coliform (TC) were investigated at nine sampling stations distributed along the main rivers of the Piracicaba River Basin, a 12,400 km² catchment located in São Paulo State, one of the most developed regions of Brazil. Spatially, a downstream impoverishment of water quality conditions was observed, as seen by the decrease of DO, and increase of BOD, nitrate, and TC. These changes were probably caused by accumulating downstream discharge of domestic and industrial sewage. Temporal evaluation of 18 years of data showed that DO decreased with time for the majority of the sampling stations, while BOD, nitrate, and TC increased. A law, approved at the end of 1991, proposed a new water tax for river water extraction for industrial and agricultural use. The amount of this tax is determined according to the water quality of the extracted water. Therefore, the evaluation of the water quality status in this basin is a first step to help resources managers to determine the values for this tax.     

STATISTICAL ANALYSIS OF DAILY WATER QUALITY DATA1

ABSTRACT. The stochastic nature of some water quality time series were examined. These time series include nine years of daily observations in: (1) the stream flow (Q), (2) the water temperature (T), (3) the dissolved oxygen (DO), and (4) the biochemical oxygen demand (BOD) of the Passaic River at Little Falls, New Jersey. It was found that the random component contributes more than 60 per cent of the variance in the BOD series, but only 30 per cent or less in the DO series. Autocorrelation analysis suggest that DO and BOD residual series have a persistence of about 30 days. Significant crosscorrelation between DO and temperature T was found when DO lags T for up to 30 days, which indicates that the critical DO probably lags the critical temperature. Also, spectral anlaysis shows multiple peaks in the BOD series, reflecting effects of storm runoff and other non-point source pollution on river water quality.     

Trends of surface water quality of the Krishna River,India during the urbanization process

In the present study, Amaravati, the proposed city of India is considered to assess the impacts of urbanization on water quality of the Krishna River in the vicinity. Long-term surface water quality data of various parameters of Krishna River are obtained from Central Water Commission (CWC). Trends of various parameters are analyzed using a modified version of Mann-Kendall (M-K) test; bootstrapped M-K trend test with optional bias corrected pre-whitening and R programming are used affecting water quality prior to and at the commencement of urbanization. During the onset of urbanization, minimum BOD is decreased from 0.49 to 0.2 mg/L, while the maximum BOD is increased by 67.7%. Dissolved oxygen's (DO) minimum value is decreased by 29.33% while maximum DO value is decreased by 4.47% at the beginning of urbanization. During the process of urbanization, total coliform's minimum count is increased to 330 from 2 MPN/100 ml while the maximum count of total coliforms is increased to 16,000 from 2400 MPN/100 ml. Faecal coilform's minimum count is increased from 2 to 80 MPN/100 ml while maximum count is increased to 16,000 from 800 MPN/100 ml during urbanization. It is found that due to urbanization, pH, DO values exceed the allowable limit.     

Coupled cycles of dissolved oxygen and nitrous oxide in rivers along a trophic gradient in southern Ontario, Canada

Diel (24-h) cycling of dissolved O2 (DO) in rivers is well documented, but evidence for coupled diel changes in DO and nitrogen cycling has only been demonstrated in hypereutrophic systems where DO approaches zero at night. Here, we show diel changes in N2O and DO concentration at several sites across a trophic gradient. Nitrous oxide concentration increased at night at all but one site in spring and summer, even when gas exchange was rapid and minimum water column DO was well above hypoxic conditions. Diel N2O curves were not mirror images of DO curves and were not symmetrical about the mean. Although inter- and intrasite variation was high, N2O peaked around the time of lowest DO at most of the sites. These results suggest that N2O must be measured several times per diel period to characterize curve shape and timing. Nitrous oxide concentration was not significantly correlated with NO3- concentration, contrary to studies in agricultural streams and to the current United Nations Intergovernmental Panel for Climate Change protocols for N2O emission estimation. The strong negative correlation between N2O concentration and daily minimum DO concentration suggested that N2O production was limited by DO. This is consistent with N2O produced by nitrite reduction. The ubiquity of diel N2O cycling suggests that most DO and N2O sampling strategies used in rivers are insufficient to capture natural variability. Ecosystem-level effects of microbial processes, such as denitrification, are sensitive to small changes in redox conditions in the water column even in low-nutrient oxic rivers, suggesting diel cycling of redox-sensitive compounds may exist in many aquatic systems.     

DESK TOP METHODOLOGY FOR MODELING BIOCHEMICAL OXYGEN DEMAND IN STREAMS1

: The modeling of dissolved oxygen in streams is a widely used technique, upon which a great deal of money has been spent. This paper concludes that the standard methods of DO modeling by computer are unnecessarily complex, and that for some purposes, they can be replaced without loss of accuracy by desk top BOD models. Taking as an example, a set of data used in DO modeling, it is shown (a) that the data are grossly inconsistent, (b) that simultaneous gathering of data introduces errors in streams of long travel time, (c) that much more data as to pollutant concentrations should have been obtained, and (d) that 24-hour DO data could have been dispensed with.     

A MODELLING METHOD FOR EVALUATING WATER QUALITY POLICIES IN NONSERIAL RIVER SYSTEMS1

ABSTRACT: This paper describes a modelling method which simplifies the evaluation of water quality policies for nonserial (branching) river systems. The method introduces dummy facilities at the junctions of the major tributary branches with the mainstream as replacements for the facilities and activities on the tributaries. The cost functions for the dummy facilities and the DO and BOD concentrations at the junctions as determined for each tributary are introduced into the mainstream serial system model which is then solved for the optimal values of the mainstream treatment plant efficiencies, the dummy facility effeciencies, and the tributary system DO and BOD concentrations using nonlinear programming. Given the optimum values for the dummy facility efficiencies and the values for the tributary system DO and BOD concentrations, the optimum values for the tributary treatment plant efficiencies are found using nonlinear programming. The method is applied to a river system with a mainstream and one major tributary which contain industrial and municipal organic and thermal polluters and their associated wastewater treatment plants.     

POLLUTANT LOADING CAPACITY FOR THE BLACK RWER,CHEHALIS RWER SYSTEM,WASHINGTON1

ABSTRACT: The Black River, a tributary of the Chehalis River in western Washington State, has a history of widespread low dissolved oxygen (DO), anoxia in some locations, and fish kills. As part of a Total Maximum Daily Load (TMDL) study, environmental data were collected during two summer dry seasons and simulations were conducted with the WASP5 model to assess the effect of biochemical oxygen demand ( BOD ), ammonia, and nutrient loads on DO in the Black River. DO levels were below the State water quality regulatory criterion of 8.0 mg/L in almost all locations during the study. The slow middle reach of the river showed stratified conditions, with anoxia in some of the deepest pools. Based on model simulations, DO was found to still fall below the 8.0 mg/L criterion in the entire mainstem under “natural” conditions, and eutrophication was identified as a potential problem in the middle reach. A TMDL was proposed for BOD and ammonia that would prevent significant degradation of DO in the Black River. To prevent eutrophic conditions in the Black River, a TMDL for total phosphorus was proposed that establishes a protective criterion of 0.05 mg/L for the middle river during the dry low-flow season.     

Determination of dissolved oxygen limitation in aerobic biofilm reactors

The concentration of dissolved oxygen (DO) strongly influences the performance of aerobic biofilm reactors because organic oxidation is limited by the availability of oxygen. However, it is not necessary to maintain a high DO level in the reactors in order to overcome this limitation. Excessive aeration wastes energy. Therefore, the determination of the onset of DO limitation against organic substrate removal in aerobic biofilm reactors is important for their effective operation. This study is aimed at developing an expression to determine the onset of DO limitation and hence to control the aeration system. The expression developed is as follows: , where S_b and C_b are the bulk concentrations of organic substrate and DO, respectively; D_ws and D_wc are the diffusion coefficients of organic substrate and oxygen in the reactors respectively; and R_b is an overall ratio of oxygen consumption to organic substrate removal in the reactors. The latter is the key parameter in the equation, and is determined by the characteristics of the substrate, biofilm, and reactor. In order to measure the value of R_b, the authors have developed a micro-biofilm reactor. The value of R_b was determined to be 0.13 (mg O₂ mg⁻¹ COD_cr) for glucose removal with this reactor. The equation has, subsequently, been verified with data from batch and continuous experiments.     

Analysis of pollution status of River Illo,Ota, Nigeria

An assessment of the pollution status of River Illo, located within River Owo catchments area in Ota, Ogun State, Nigeria, was carried out. The River’s response to deoxygenation due to BOD loading from an abattoir and its dissolved oxygen (DO) level was predicted using the modified Streeter-Phelps model. The average concentrations of measured parameters at the sampling stations include: 2.24 mg/l of DO, 312.85 mg/l of BOD, 782.86 mg/l of chemical oxygen demand, and 620.76 g/l of total solids. The DO model for River Illo showed a positive correlation between measured and calculated DO, while the dissolved oxygen curve gave a double spoon shape of two major segments with distinct zones of degradation, decomposition, and recovery. The self-purification factor (f) for both segments ranged between 0.8 and 1.1 depicting River Illo as a slow moving or sluggish river. The above results revealed slow reaeration of the water body while full recovery from pollution was difficult. The treatment of River Illo before usage is very essential to ensure public health safety of users from waterborne diseases.     

Establishment the relationship between water quality parameter and micro plastic concentration for Adyar and Cooum estuary

Increasing micro plastic concentration in the marine environment is a severe threat to the marine ecosystem and indirectly to human society depending on the marine environment. Also, the surface and subsurface water quality parameters are the indicators of the usability of the water sources for human activities. The primary source of micro plastic is the water river systems from land to sea. This study establishes a correlation between water quality parameters and micro plastic concentration to find the most suitable quality parameter for finding the micro plastic concentration in urban coastal estuaries of Chennai coast, Tamil Nadu, India. Twenty samples from Adyar and Cooum estuaries were collected, with ten each on August 2019 and August 2020. They are tested for temperature pH, EC, Turbidity, TDS, DO, BOD, COD, Salinity and micro plastic concentrations. Correlation tests such as Pearson's and Spearman's are performed based on the initial Normality and Homogeneity test. The results show that all the parameters are significantly not correlated with the Micro plastic Concentration, and Micro plastic Concentration is considered an independent factor.     

京杭运河(苏州段)水质时空分布特征分析

本文基于数据分析工具Excel 2007和SPSS17.0,采用多元统计方法中的聚类分析与判别分析对2008年京杭运河(苏州段)水质时空分布特征进行分析,以识别水质指标的时间与空间差异性。时间分析结果将京杭运河(苏州段)划分为与丰、平、枯水期略有差异的3个时期,其中7项显著性时间差异的水质指标为pH、NH4-N、CODMn、DO、BOD5、V-phen、cn-total。空间分析结果将研究区域分为3个污染区域;空间分析判别函数的构建表明仅pH、NH4-N、CODMn、DO、BOD55项水质指标即可反映研究区域水质的差异性。本研究结果对改善省界河流水质、缓解省际纠纷、维护社会和谐稳定具有重要意义。     

掺杂型二氧化钛纳米管光催化降解甲基橙研究

利用本实验室制备的N-F原子掺杂二氧化钛纳米管作催化剂,在可见光区对甲基橙(MO)进行光催化降解实验。在催化剂用量固定为3cm2时考察了不同初始浓度、pH值、溶解氧(DO)等对降解率的影响。结果表明,在可见光区该催化剂具有较高的光催化活性;当溶液DO为19.2mg/L、pH值为3、初始浓度为10mg/L、反应时间300min时,降解率可达82.3%。     

GOALS IN WASTEWATER TREATMENT1

Within a few years all domestic wastewater effluents in the United States will be subjected to a minimum of a properly operated primary and secondary treatment process. This implies a very high degree of removal of the more readily biologically degradable material as measured by the BOD test. This practice will to a large degree negate the value of the BOD test as a pollution parameter. Organic carbon appears to be a more suitable means for determining the strength of a wastewater or for controlling the operation of physical and chemical treatment processes. Studies were conducted to determine the effect of time of passage on the ratio of organic carbon to BOD, COD and carbohydrate. The ratio was found to vary with both time and the state of the sample. The carbon content was reduced to a lesser degree than the other parameters. Organic carbon content appears to correlate better with COD than with BOD. The efficiency of a chemical precipitation process can be determined on the basis of organic carbon removal.