A Stochastic Model for BOD and DO with Random Initial Conditions and Distance Dependent Velocity

A random differential equation arises in stream pollution models when the initial conditions are stochastic and the stream velocity is distance dependent. The mean squared solution gives the biochemical oxygen demand (BOD) and the dissolved oxygen (DO) at any distance downstream from the pollution source. The probability density function and some of the moments of the BOD and DO are obtained, thus completely characterizing the BOD and DO process. An example illustrates the results and compares them with previous ones.     

A flow injection analysis system with encapsulated high-density <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> cells for rapid determination of biochemical oxygen demand

The biochemical oxygen demand (BOD) determination was studied using a novel flow injection analysis (FIA) system with encapsulated Saccharomyces cerevisiae cells and an oxygen electrode and was compared with conventional 5-day BOD tests. S. cerevisiae cells were packed in a calcium alginate capsule at a dry cell weight of 250 g/l of capsule core. The level of dissolved oxygen (DO) was reduced due to the enhanced respiratory activity of the microbial cells when the injected nutrient passed through the bioreactor. The decrease in DO (ΔDO) was intensified with the amount of microbial cells packed in the bioreactor. However, the specific ΔDO decreased as the amount of cells loaded in the bioreactor increased. The ΔDO value was dependent on the pH and temperature of the mobile phase and reached its maximum value at 35°C and pH 7–8. Also, ΔDO became larger at longer response times as the flow rate of the mobile phase decreased. The measurement of ΔDO was repeated more than six times consecutively using a 20-ppm standard glucose and glutamic acid solution, which confirmed the reproducibility with a standard deviation of 0.95%. A strong linear correlation between ΔDO and BOD was also observed. The 5-day BOD values of actual water and wastewater samples were in accordance with the BOD values obtained by this FIA method using encapsulated S. cerevisiae cells. Unlike the cell-immobilized bead system, there was no contamination of the bioreactor resulting from any leak of yeast cells from the sensor capsules during BOD measurements.     

Modeling of activated sludge wastewater treatment processes

The performance of an activated sludge wastewater treatment process consisting of an aeration tank and a secondary settler has been studied. A tanks-in-series model with backflow was used for mathematical modeling of the activated sludge wastewater treatment process. Non-linear algebraic equations obtained from the material balances of MLSS (mixed liquor suspended solids or activated sludge), BOD (biological oxygen demand) and DO (dissolved oxygen) for the aeration tank and the settler and from the behavior of the settler were solved simultaneously using the modified Newton-Raphson technique. The concentration profiles of MLSS, BOD and DO in the aeration tank were obtained. The simulation results were examined from the viewpoints of mixing in the aeration tank and flow in the secondary settling tank. The relationships between the overall performance of the activated sludge process and the operating and design parameters such as hydraulic residence time, influent BOD, recycle ratio and waste sludge ratio were obtained.     

A rational approach for predicting the dissolved oxygen profile in receiving waters

A practical method for predicting the dissolved oxygen (DO) profile in a stream receiving biodegradable waste is presented. In this method the BOD (accumulated O₂ uptake) curve is obtained using an open jug technique. The accumulated O₂ uptake curve thus developed is employed in numerical integration with the physical reaeration data for the receiving stream to predict the DO profile in the stream. In the present study, the method was examined using 10-liter open jar reactors to obtain the O₂ uptake curves, and the receiving stream was a 670-liter simulated stream apparatus which has been employed in previous studies on stream reaeration. The method was found to provide a fairly good prediction of the actual dissolved oxygen profile observed in the receiving stream. The effect of the reaeration constant, K₂ )agitation effect(, on the kinetics of O₂ uptake was also investigated and it was found that increased agitation (higher K₂ value) caused some increase in the accumulated oxygen uptake (BOD) curve with most of the increase coming after the so-called “plateau” area in the O₂ uptake curve, i.e., in the general case, after the low point along the DO sag curve.     

UASB/Flash aeration enable complete treatment of municipal wastewater for reuse

A simple, efficient and cost-effective method for municipal wastewater treatment is examined in this paper. The municipal wastewater is treated using an upflow anaerobic sludge bed (UASB) reactor followed by flash aeration (FA) as the post-treatment, without implementing aerobic biological processes. The UASB reactor was operated without recycle, at hydraulic retention time (HRT) of 8 h and achieved consistent removal of BOD, COD and TSS of 60-70% for more than 12 months. The effect of FA on UASB effluent post-treatment was studied at different HRT (15, 30 and 60 min) and dissolved oxygen (DO) concentrations (low DO = 1-2 mg/L and high DO = 5-6 mg/L). The optimum conditions for BOD, COD and sulfide removal were 30-60 min HRT and high DO concentration inside the FA tank. The final effluent after clarification was characterized by BOD and COD values of 28-35 and 50-58 mg/L, respectively. Sulfides were removed by more than 80%, but the fecal coliform only by ~2 log. The UASB followed by FA is a simple and efficient process for municipal wastewater treatment, except for fecal coliform, enabling water and nutrients recycling to agriculture.     

Novel BOD optical fiber biosensor based on co-immobilized microorganisms in ormosils matrix

A biochemical oxygen demand (BOD) sensor has been developed, which is based on an immobilized mixed culture of microorganisms combined with a dissolved oxygen (DO) optical fiber. The sensing film for BOD measurement consists of an organically-modified silicate (ORMOSIL) film embedded with tri(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) perchlorate and three kinds of seawater microorganisms immobilized on a polyvinyl alcohol sol-gel matrix. The BOD measurements were carried out in the kinetic mode inside a light-proof cell and with constant temperature. Measurements were taken for 3 min followed by 10 min recovery time in 10 mg/L glucose/glutamate (GGA) BOD standard solution, and the range of determination was from 0.2 to 40 mg/L GGA. The effects of temperature, pH and sodium chloride concentration on the BOD sensing films were studied. BOD values estimated by this optical BOD sensing film correlate well with those determined by the conventional BOD5 method for seawater samples.     

A simple algorithm for on-line prediction of BOD(5) by a microprocessor-based system

A novel algorithm for predicting BOD(5) from the dissolved oxygen (DO) concentration after a relatively short incubation period is presented and evaluated experimentally. Test runs on synthetic and experimentally derived raw data suggest that BOD(5) can be predicted to within 15% ca. 36 h. The method can be improved by filtering out, via a digital filter, noise from the raw data. The suggested algorithm does not require elaborate computations or large data storage and can therefore be implemented on a low-cost microcomputer for fast on-line determination of BOD(5).     

Monitoring the biodegradability of bisphenol A and its metabolic intermediates by manometric respirometry tests

As a result of its wide usage in the production of polycarbonate plastics and epoxy resins, bisphenol A (BPA) is commonly detected in wastewaters. Recently, BPA became a major concern because its adverse effects as an endocrine disruptor. In this work, the biodegradation kinetics of BPA and its metabolic intermediates 4-hydroxyacetophenone (4HAP), 4-hydroxybenzaldehyde (4HB) and 4-hydroxybenzoic acid (4HBA) by BPA-acclimated activated sludge was studied using manometric respirometry (BOD) tests. For all the tested compounds, BOD curves exhibited two phases. In the first one, a fast increase of the oxygen consumption (OC) due to the active oxidation of the substrate was obtained. Then, when the substrate was exhausted, the endogenous respiration produced a slower increase of OC. A standard Monod-model with biomass growth was used to represent the OC profiles as a function of time. For all the tested compounds, a good agreement between the proposed model and the experimental data was obtained. According to their biodegradation rates, the tested compounds can be ordered as follows: BPA < 4HAP ? 4HB < 4HBA. Because the oxidation rate of BPA by BPA-acclimated activated sludge limits the rate of the whole biodegradation pathway, the accumulation of metabolic intermediates 4HAP, 4HB, and 4HBA would be negligible. To calculate the dissolved oxygen (DO) concentration (C) during the BOD tests, the oxygen transfer coefficient (k_La) of the BOD bottles was obtained using the sulfite method. Finally, a simple procedure to calculate the minimum DO concentration (C_min) based on BOD data was developed. Calculation results demonstrated that under the tested conditions, C values were high enough as not to be the limiting substrate for the microbial growth.     

生物传感器快速测定BOD系统的稳定性研究

在前期研究工作的基础上,确定了生物传感器快速测定BOD的实验流程。研究了温度对检测结果的影响,初始BOD浓度与检测时间的关系,并探讨了检测结果的重现性及其线性范围。结果表明：恒温环境可以保持微生物活性的相对稳定,并保证了检测过程的相对稳定,检测结果的最大相对偏差7.7%,满足BOD快速测定的要求;溶液BOD浓度不同,所需的检测时间也不同,BOD浓度越高,所需时间越长。在曝气状态下,可以保证BOD浓度在200mg/l以下的样品在15min以内检测完毕。通过对线性范围的分析,该方法适宜的线性范围可达5－200mg/l。     

pH, Redox, and oxygen microprofiles in rhizosphere of bulrush (Scirpus validus) in a constructed wetland treating municipal wastewater

Microenvironmental studies regarding plant oxygen release in a wastewater environment are important to understand the principles of constructed wetlands for wastewater treatment. pH, oxidation reduction potential (ORP), and dissolved oxygen (DO) microprofiles for the lateral and main roots of the bulrush (Scirpus validus) in a vertical flow constructed wetland fed with municipal wastewater were measured using microelectrode techniques. pH was found to be low (6.91-6.98) near the lateral root surface, indicating possible nitrification or H(+) extrusion. The ORP at the lateral root surface was between +250 and +317 mV and gradually reached the bulk solution ORP (+14 to -54 mV) at a radial distance of approximately 4,750 microm. DO values at the lateral root surface varied from 0.64-2.04 mg L(-1) as bulk biochemical oxygen demand (BOD) changed from 24 to 1,267 mg L(-1). DO at the lateral root surface and the thickness of the oxygen layer around the root marginally increased with an increase in bulk BOD, while ORP at the lateral and main root surface decreased. pH and DO values did not change near the main root and had the bulk solution values. The results of this study provide insights into root-induced microenvironments and would be helpful for the quantification of the total amount of oxygen contributed by plants in constructed wetlands.     

Dissolved oxygen decline in ice-covered rivers of northern Alberta and its effects on aquatic biota

To determine whether existing dissolved oxygen (DO) regulationswere adequate to protect riverine biota, the Northern River Basins Studyrequired a research and assessment program to establish the effect ofpulp mill and municipal sewage discharges on under-ice DO concentrationsand aquatic biota in the Athabasca, Wapiti and Smoky rivers of northernAlberta, Canada. Analysis of monitoring data collected over >30 yearsshowed that pulp mill and municipal effluents have caused sags in DObelow their discharges and contributed to an increased rate of declinein DO over 10s of kilometers in the Wapiti-Smoky rivers or 100s ofkilometers in the Athabasca River. To permit forecasting of DO declinesin response to changes in river discharge or effluent biochemical oxygendemand (BOD), a one-dimensional steady-state river water quality modelwas implemented that successfully (r² =0.74–0.92) predicted DO concentrations over an 820 km reach of theAthabasca River for the 1990–1994 winters. Experiments on nativefish and benthic macroinvertebrate species showed that exposure to lowDO and low temperatures (2–3°C) caused delays in hatch ofmountain whitefish eggs (at 6.5 mg/L DO), reduced mass of bull troutalevins post-hatch (at 5.0 mg/L DO), extended the spawning period ofburbot (at 6.0 mg/L DO), and depressed feeding rates and loweredsurvival of the mayfly Baetis tricaudatus (at 5 mg/L DO).As a result of recommendations from this integrated program of rivermonitoring, modelling and experimentation, effluent BOD loading has beenreduced to the Athabasca and Wapiti rivers and the provincial DOguideline for protection of aquatic life has been increased from 5.0 to6.5 mg/L.     

Effects of dilution on dissolved oxygen depletion and microbial populations in the biochemical oxygen demand determination

The biochemical oxygen demand (BOD) value is still a key parameter that can determine the level of organics, particularly the content of biodegradable organics in water. In this work, the effects of sample dilution, which should be done inevitably to get appropriate dissolved oxygen (DO) depletion, on the measurement of 5-day BOD (BOD₅), was investigated with and without seeding using natural and synthetic water. The dilution effects were also evaluated for water samples taken in different seasons such as summer and winter because water temperature can cause a change in the types of microbial species, thus leading to different oxygen depletion profiles during BOD testing. The predation phenomenon between microbial cells was found to be dependent on the inorganic nutrients and carbon sources, showing a change in cell populations according to cell size after 5-day incubation. The dilution of water samples for BOD determination was linked to changes in the environment for microbial growth such as nutrition. The predation phenomenon between microbial cells was more important with less dilution. BOD₅ increased with the specific amount of inorganic nutrient per microbial mass when the natural water was diluted. When seeding was done for synthetic water samples, the seed volume also affected BOD due to the rate of organic uptake by microbes. BOD₅ increased with the specific bacterial population per organic source supplied at the beginning of BOD measurement. For more accurate BOD measurements, specific guidelines on dilution should be established.     

Operational parameters affecting the performannce of a mediator-less microbial fuel cell

A mediator-less microbial fuel cell was optimized in terms of various operating conditions. Current generation was dependent on several factors such as pH, resistance, electrolyte used, and dissolved oxygen concentration in the cathode compartment. The highest current was generated at pH 7. Under the operating conditions, the resistance was the rate-determining factor at over 500 omega. With resistance lower than 500 omega, proton transfer and dissolved oxygen (DO) supply limited the cathode reaction. A high strength buffer reduced the proton limitation to some extent. The DO concentration was around 6 mg l(-1) at the DO limited condition. The fact that oxygen limitation was observed at high DO concentration is believed to be due to the poor oxygen reducing activity of the electrode used, graphite. The current showed linear relationship with the fuel added at low concentration, and the electronic charge was well correlated with substrate concentration from up to 400 mg l(-1) of COD(cr). The microbial fuel cell might be used as a biochemical oxygen demand (BOD) sensor.     

水利工程对河流生态系统服务功能的影响评价方法初探

通过分析水利工程对河流生态系统服务功能的影响,建立了评价指标体系和定量化的评价方法．评价指标体系包括建立评价指标的原则、对河流生态系统服务功能的分类和指标确定等．本文将河流生态系统的服务功能分为四类即供水及与供水量相关的航运和水电功能、生态支持功能、调节控制功能和文化美学功能．依据不同的功能类型,应用以前的研究成果,针对水利工程产生的生态效应如生物多样性的变化和河流净化功能的变化,确定了不同的调度指标,并建立了相应的数量化评价方法,主要包括指效法和BOD-DO模型方法,这些方法特有助于对水利工程的生态环境效应进行深入的分析与评价。     

Continuous fill intermittent decant type sequencing batch reactor application to upgrade the UASB treated sewage

The performance of continuous flow intermittent decant type sequencing batch (CFID) reactor treating the effluent of an UASB reactor treating domestic wastewater and operated at 8 h hydraulic retention time (HRT) was investigated. The CFID was operated at three different HRTs (22, 8 and 6 h) and three different dissolved oxygen (DO) patterns (<0.5, 2.5–3.5 and 3.5–4.5 mg/L). The highest effluent quality was observed at the 8 h HRT and 2.5–3.5 mg/L DO concentration. At this operational condition, the average BOD, TSS, ammonia nitrogen and fecal coliform removal efficiencies were 83, 90, 74 and 99 %, respectively. The CFID is a promising post-treatment option for existing UASB systems, with a final effluent quality that comply with receiving water and effluent reuse criteria.     

An approach for prediction of optimum reaction conditions for laccase-catalyzed bio-transformation of 1-naphthol by response surface methodology (RSM)

Response surface methodology (RSM) was successfully applied to enzymatic bio-transformation of 1-naphthol. The experiments were conducted in a closed system containing acetone and sodium acetate buffer, with laccase enzyme. Laccase enzyme used as catalyst was derived from Trametes versicolor (ATCC 200801). The enzymatic bio-transformation rate of 1-naphthol, based on measurements of initial dissolved oxygen (DO) consumption rate in the closed system, was optimized by the application of RSM. The independent variables, which had been found as the most effective variables on the initial DO consumption rate by screening experiments, were determined as medium temperature, pH and acetone content. A quadratic model was developed through RSM in terms of related independent variables to describe the DO consumption rate as the response. Based on contour plots and variance analysis, optimum operational conditions for maximizing initial DO consumption rate, while keeping acetone content at its minimum value, were 301 K of temperature, pH 6 and acetone content of 7% to obtain 9.17 x 10(-3) mM DO/min for initial oxidation rate.     

Enzymatic Evaluation of Oxidation Pond Performance

A one year study on a waste oxidation pond was undertaken to observe the behaviour of four enzymes, viz catalase, phosphatase, protease and amylase with respect to other ecological factors. The increase in solar radiation from March to May enhanced phytoplankton growth resulting in increased pH and DO and considerable reduction in nutrients and BOD. Variations in the activity of enzymes seemed to be directly related to bacterial number. The activity of catalase and phosphatase seemed to be related to the microbial density and nutrient status of the pond. The activity of protease and amylase could be used as a measure of degradation of organic matter.     

Some aspects of the metabolism of a partially colloidal substrate

The biochemical oxygen demand (BOD) of a complex, partially colloidal substrate is divided into oxidation (f_o) and synthesis (f_s) fractions. The substrate being investigated is a suspension containing 10 mg./l. of dry skim milk. The oxidized and synthesized fractions of the BOD are shown to be 38.4% and 61.6%, respectively. The division of BOD is related to the time at which maximum cell growth appears. The time required to obtain maximum cell production is shown to be at least 10 hr. The relationship between the time to maximum cell production and the apparent initial activity of the seed organisms is discussed.     

Characteristics of solids, BOD5 and VFAs in liquid swine manure treated by short-term low-intensity aeration for long-term storage

A laboratory-scale experiment presents data that reveal the temporal characteristics of solids, biochemical oxygen demand (BOD5) and volatile fatty acids (VFAs) in the aerated liquid swine manure for minimizing odor generation potential during 190-day storage. The performance of 15-day aeration of liquid manure with initial total solids (TS) content from 0.5% to 4.0% was examined at low-intensity aeration rates, i.e., +35 mV oxidation-reduction potential (ORP), 1.0 mg O2/l and 3.0 mg O2/l dissolved oxygen (DO). Odor generation potential was evaluated using VFAs. The aeration process contributed remarkably to the decomposition of TS, total volatile solids (TVS), BOD5 and VFAs. Moreover, the stabilization of manure due to aeration could last up to 190 days. The TS reduction on day 190 ranging from 6.3% to 32.7%, 20.2% to 39.1%, 19.0% to 41.0% were realized under the intensities of +35 mV ORP, 1.0 and 3.0 mg O2/l, respectively. At the same time, the reduction of BOD5 and VFAs reached around 7.8% to 69.5%, 17.2% to 79.9% and 21.9% to 91.1%; 0.4% to 91.0%, 60.4% to 95.0% and 70.4% to 94.1%. The liquid manure with low solids (e.g., TS of 0.5% and 1.0%) offered an advantageous condition for aeration treatment, particularly for biodegradation of BOD5 and VFAs. The odor generation potential could also be evaluated by the levels of solids and BOD5 in the manure. Increasing aeration intensity would significantly diminish the odor generation potential for given levels of solids and/or BOD5. Fifteen-day aeration with intensity of 1.0 mg O2/l may be recommended at farm level for both odor control and energy savings.