Simulating a cyclic activated sludge system by employing a modified ASM3 model for wastewater treatment

To interpret the biological nutrient removal in a cyclic activated sludge system (CAS), a modified model was developed by combining the process of simultaneous storage and growth, and the kinetics of soluble microbial product (S _SMP) and extracellular polymeric substance (X _EPS) with activated sludge model no. 3 (ASM3). These most sensitive parameters were initially selected whilst parameters with low sensitivity were given values from literature. The selected parameters were then calibrated on an oxygen uptake rate test and a batch CAS reactor on an operational cycle. The calibrated model was validated using a combination of the measurements from a batch CAS reactor operated for 1 month and the average deviation method. The simulations demonstrated that the modified model was capable of predicting higher effluent concentrations compared to outputs of the ASM3 model. Additionally, it was also shown that the average deviation of effluent S _COD, S _NH, S _SMP and X _EPS simulated with the modified model was all less than 1 mg L⁻¹. In summary, the model could effectively describe biological processes in a CAS reactor and provide a wonderful tool for operation.

     

THE USE OF TROFIC AS AN AID FOR THE MANAGEMENT OF EUTROPHIC LAKES

SUMMARY

As a result of eutrophication studies that have been performed by the National Institute for Water Research for many years it was decided in 1980 that a detailed investigation into this area take place. Hypertrophic Hartbeespoort Dam was selected as the study site. A simulation model, named TROFIC, of the ecosystem was developed and updated over a three-year research program. Different management strategies were performed to attempt to reduce the size of phytoplankton standing stock and to modify the phytoplankton species composition so that blue-green algae are no longer dominant. In this paper the applicability of each strategy to the model is examined by means of results obtained and conclusions drawn from these results.     

Health and chemical burdens of fish species from polluted and hyper-eutrophic freshwater ecosystems in South Africa

Three aquatic ecosystems in South Africa, the Hartbeespoort, Klipvoor and Bospoort Dams, are classified as hyper-eutrophic, because of high nutrient loads and chemical pollution. Water and two fish species, Clarias gariepinus and Cyprinus carpio, were collected from these dams to assess the impact of eutrophication and chemical pollutants on their health status. Water and muscle samples were analysed for organic and inorganic chemicals. Condition factor was determined and a necropsy performed to note any macroscopic abnormalities. A histology-based fish health assessment was done on the liver, kidney, gills and gonads. A number of fish from the three dams exhibited livers with fatty change and focal discoloration, skin lesions and parasites within the visceral cavity. The prevalence and severity of histopathology in the liver resulted in higher liver index values than the index values for kidneys and gills. Aluminium, silicon and chromium were detected in the water and muscle tissue. The DDT metabolite p,p’-DDE was present in both species, as well as in fish from the reference site, Marico-Bosveld Dam. Only C. gariepinus from Hartbeespoort Dam had p,p’-DDD levels higher than 5 µg g^?1 per edible portion. Water from hyper-eutrophic dams adversely affects the health of freshwater fish.     

A one dimensional moving bed biofilm reactor model for nitrification of municipal wastewaters

This work presents a one-dimensional model of a moving bed bioreactor (MBBR) process designed for the removal of nitrogen from raw wastewaters. A comprehensive experimental strategy was deployed at a semi-industrial pilot-scale plant fed with a municipal wastewater operated at 10–12 °C, and surface loading rates of 1–2 g filtered COD/m² d and 0.4–0.55 g NH₄-N/m² d. Data were collected on influent/effluent composition, and on measurement of key variables or parameters (biofilm mass and maximal thickness, thickness of the limit liquid layer, maximal nitrification rate, oxygen mass transfer coefficient). Based on time-course variations in these variables, the MBBR model was calibrated at two time-scales and magnitudes of dynamic conditions, i.e., short-term (4 days) calibration under dynamic conditions and long-term (33 days) calibration, and for three types of carriers. A set of parameters suitable for the conditions was proposed, and the calibrated parameter set is able to simulate the time-course change of nitrogen forms in the effluent of the MBBR tanks, under the tested operated conditions. Parameters linked to diffusion had a strong influence on how robustly the model is able to accurately reproduce time-course changes in effluent quality. Then the model was used to optimize the operations of MBBR layout. It was shown that the main optimization track consists of the limitation of the aeration supply without changing the overall performance of the process. Further work would investigate the influence of the hydrodynamic conditions onto the thickness of the limit liquid layer and the “apparent” diffusion coefficient in the biofilm parameters.

     

TOWARDS THE SUSTAINABLE WATER QUALITY MANAGEMENT OF AN URBANISED AFRICAN RIVER CATCHMENT: THE KLIP RIVER,GAUTENG, SOUTH AFRICA

Summary

A water quality impact assessment of Greater Johannesburg's three southern wastewater treatment works was undertaken to quantify present and predict future contributions of pollution to the Klip River, as well as the impact on downstream users. This information is required to assist the Department of Water Affairs and Forestry in setting appropriate standards for the treated effluent discharged from these works. and for the integrated water quality management of the entire Klip River system.

The study showed that the wetlands in the Klip River system have a distinct and important role to play in the abatement of diffuse pollution. A contradictory view is held. however, by many local communities. Their feeling is that the wetlands are unsafe areas and aesthetically unacceptable due to their propensity to act as waste traps.     

Towards the assessment of the trophic status of South African impoundments for management purposes: Bon Accord Dam

The 1 mg/l phosphate effluent standard legislated in South Africa in 1980 in seven sensitive catchments, and ad hoc eutrophication-related requests, necessitated the monitoring of 53 impoundments throughout the country. Variables that were monitored, and are still being monitored in some cases, included nutrients, chlorophyll a, algal identification, suspended solids and other major inorganic constituents. The measurement of temperature and oxygen profiles was conducted on an ad hoc basis when the sites were visited. The results, as determined from data collected between 1989 and 1998, indicated a range of trophic states from oligotrophic to hyper-eutrophic in the sensitive catchments. The catchments that were covered in the survey are: the Vaal River, Crocodile River (North West Province), Pienaars River, Olifants River (Mpumalanga Province), Letaba River, Buffalo River, Berg River, White Mfolozi River, Mgeni River, Mlazi River and the Molopo River catchments.

The objective of this paper is to discuss the methods, variables and presentation for determining the trophic status of an impoundment for management purposes by using findings in the Bon Accord Dam, a small reservoir near Pretoria. The trophic status of selected impoundments was determined by using the mean total phosphorus (TP) concentrations, the nitrogen to phosphorus ratio, the mean chlorophyll a concentration, the presence of cyanobacteria and the turbidity (measured by means of Secchi disc readings) of the system.

The mean annual phosphorus concentrations dropped from more than 800μg/l to less than 100μg/l in three years, and have remained at that level since 1987. The authors suggest that further reductions in phosphorus input are necessary to prevent eutrophication in the reservoir.     

Improving predictive mapping in Swiss mire ecosystems through re‐calibration of indicator values

Question: How may Landolt indicator values be re‐calibrated to improve the performance of predictive models? Location: Mires Gross Moos Schwändital (1250 m a.s.l.) in the Prealps, Burgmoos (465 m. a.s.l.) on the Central Plateau and La Burtignière (1000 m a.s.l.) in the Jura, Switzerland. Methods: Habitat distribution models based on high resolution remotely sensed data and vegetation field data are applied to monitor 130 mires. Instead of plant species or communities we used mean indicator values of vegetation records as response variables. To improve the differential power of indicator values for wetland habitat conditions, we calibrated these values using field data. Different methods were tested with our predictive models in three mires to see which calibration method is best in enhancing model performance. To assess the effect of the uneven distribution of vegetation records along environmental gradients, calibrations based on random and evenly distributed samples were compared. As a test of the predictive power of the models we used r² between ground truth and model prediction. This approach is illustrated through an application with nutrient indicator values in the mire La Burtignière. Results: Model performances were not the same for the three mires. The predictive power was better for the nutrient values, soil reaction and humus values than for light and moisture values. 2000 records were sufficient as basis for re‐calibration. Models based on original Landolt indicator values were overall the weakest compared with re‐calibrated values. By comparing the predictive power of Models based on randomly or evenly selected records were about equally predictive. Conclusions: 1. Ahabitat‐specific re‐calibration of the Landolt indicator values enhances the predictive mapping of the Swiss mire ecosystems. 2. The re‐calibration based on weighted averaging gives a better performance than the one based on Gaussian logistic regression. 3. The uneven distribution of indicator values due to the over‐representation of mire habitats does not hamper model performance. 4. 2000 vegetation records are a sufficient basis for an optimal re‐calibration of the vegetation types. An illustration of the method is given by using the soil fertility pattern of the mire La Burtignière.     

Ecological sensitivity of marl lakes to nutrient enrichment: evidence from Hawes Water,UK

相似文献   

A Catastrophe Model for Water Bloom Prediction: A Case Study of China's Lake Chaohu

Using a case study of Lake Chaohu, the fifth largest lake in China, we constructed a cusp model for water bloom prediction that used TP (total phosphorus), T (temperature), Chla (chlorophyll-a), and DO (dissolved oxygen). These four parameters were assumed to be the most important factors in eutrophication and water bloom of the lake. The model was found to be accurate, because its relative error was around 10%. What is more convincing, according to the catastrophe discriminant of the cusp model, it could be judged that a discontinuous jump of the aquatic ecosystem occurred in July 2004, in Lake Chaohu. This conclusion is consistent with the fact that water blooms arose in August 2004. The cusp model also showed satisfactory precision when applied to forecast the eutrophication trend and prediction of water bloom in Lake Chaohu in 2005. The case study found that water bloom brought on by eutrophication can be fit and predicted by a catastrophe model. We suggest that catastrophe models would be a constructive approach to forecast and judge the outbreak of water bloom in lakes. In addition, by constructing and studying such catastrophe models, lake managers would be able to simulate the effects of different protection and mitigation projects and enrich the scientific basis for the optimization of these projects as well.     

A system for the on-line determination of glucose concentration

An off-line glucose analyzer, Yellow Springs Instrument (YSI) model 27 was modified and coupled to various peripheral components to produce a fast, fully automated system for the online determination of glucose concentration. The amount of time required to accomplish each measurement was in the order of two minutes. To demonstrate the utility of this system, various tests were performed. First, a stream containing known amounts of glucose was monitored on-line and the system was calibrated. The calibration curve was shown to be described by Michaelis-Menten kinetics. Once the system was properly calibrated, it was used to monitor the glucose concentration in the effluent stream of two different enzyme reactor systems. The glucose concentrations were within experimental error of those obtained via standard off-line techniques.     

A mixture theory model of fluid and solute transport in the microvasculature of normal and malignant tissues. II: Factor sensitivity analysis, calibration, and validation

The treatment of cancerous tumors is dependent upon the delivery of therapeutics through the blood by means of the microcirculation. Differences in the vasculature of normal and malignant tissues have been recognized, but it is not fully understood how these differences affect transport and the applicability of existing mathematical models has been questioned at the microscale due to the complex rheology of blood and fluid exchange with the tissue. In addition to determining an appropriate set of governing equations it is necessary to specify appropriate model parameters based on physiological data. To this end, a two stage sensitivity analysis is described which makes it possible to determine the set of parameters most important to the model’s calibration. In the first stage, the fluid flow equations are examined and a sensitivity analysis is used to evaluate the importance of 11 different model parameters. Of these, only four substantially influence the intravascular axial flow providing a tractable set that could be calibrated using red blood cell velocity data from the literature. The second stage also utilizes a sensitivity analysis to evaluate the importance of 14 model parameters on extravascular flux. Of these, six exhibit high sensitivity and are integrated into the model calibration using a response surface methodology and experimental intra- and extravascular accumulation data from the literature (Dreher et al. in J Natl Cancer Inst 98(5):335–344, 2006). The model exhibits good agreement with the experimental results for both the mean extravascular concentration and the penetration depth as a function of time for inert dextran over a wide range of molecular weights.     

MY EXPERIENCE OF DIGITAL RECORDING

ABSTRACT

Object classifiers that attempt to mimic dolphin echolocation require an auditory weighting function representative of dolphin peripheral auditory processing. An evolutionary program (EvPg) was used to fit the frequency-dependent output of a bank of bandpass filters to the auditory sensitivity of the bottlenose dolphin, Tursiops truncatus. Pseudo-Gaussian (PG) and rounded exponential (ROEX) functions were used to describe individual filter shapes. Variables determining the number of filters per model, overall filter shape and amplitude scaling were submitted to the EvPg for optimization. Maximum deviation (P _e ) between model output and the sensitivity of the dolphin was used as a measure of similarity between the two, i.e., lower P _e indicated a greater similarity. The number of filters converged upon 37 for all ROEX models and ≤ 45 for all PG models. The P _e of the best-performing PG model was 0.08, and for all ROEX models was 0.13. Greatest deviations typically occurred below 5 kHz and above 130 kHz. Relative audiometric sensitivity of a dolphin ear model has been improved relative to previous models, thereby providing an auditory weighting function more representative of dolphin peripheral auditory processing. This model will be applied to further investigate how dolphins use echolocation to discriminate among objects.     

Sensitivity analysis of an energetic muscle model applied at whole body level in recumbent pedalling

Musculoskeletal models are used in order to describe and analyse the mechanics of human movement. In order to get a complete evaluation of the human movement, energetic muscle models were developed and were shown to be promising.

The aim of this work is to determine the sensitivity of muscle mechanical and energetic model estimates to changes in parameters during recumbent pedalling.

Inputs of the model were electromyography and joint angles, collected experimentally on one participant. The sensitivity analysis was performed on muscle-specific tension, physiological cross-sectional area, muscle maximal force, tendon rest length and percentage of fast-twitch fibres using an integrated sensitivity ratio. Soleus, gastrocnemius, vasti, gluteus and medial hamstrings were selected for the analyses.

The energetic model was found to be always less sensitive to parameter changes than the mechanical model. Tendon slack length was found to be the most critical parameter for both energetic and mechanical models even if the effect on the energetic output was smaller than on muscle force and joint moments.     

富营养化对白洋淀底栖-浮游耦合食物网结构和功能的影响

国际湖沼学的长期研究发现,一个完整的湖泊生态系统应包括底栖食物网和浮游食物网,而营养条件变化会显著改变浅水湖泊中底栖-浮游食物网的结构和功能。为了明晰富营养化对浅水湖泊底栖-浮游耦合食物网结构和功能的影响,以浅水草型湖泊——白洋淀为研究区,运用野外监测和ECOSIM与ECOPATH(Ew E)模型相结合方法,构建白洋淀底栖-浮游耦合食物网的概念模型,模拟1982—2011年间富营养化对白洋淀底栖路径和浮游路径的结构和功能影响:(1)野外监测的结果表明,从1999年至今白洋淀一直处于富营养化状态;(2)Ew E模型模拟结果表明1982—2006年,总生物量呈下降趋势,下降比例达66.38%;能流路径从以底栖路径为主转变为以浮游路径为主;(3)运用Pearson相关分析,结果表明:浮游植物与TN(r=0.67,P0.01)和TP(r=0.37,P0.05)呈显著正相关,而底栖藻类和大型沉水植物与TN(r=0.77,P0.01;r=0.67,P0.01)和TP(r=0.54,P0.01;r=0.36,P0.05)呈显著负相关。富营养化是白洋淀底栖初级和次级生产力向浮游初级和次级生产力转变的主要驱动力。采用科学的方法准确评估富营养化对湖泊底栖-浮游耦合食物网结构和功能的影响,可为湖泊生态系统管理提供技术和方法支持。     

Change in diel catchability of young-of-year yellow perch associated with establishment of dreissenid mussels

1. Non‐native mussels have increased water clarity in many lakes and streams in North America and Europe. Diel variation in catchability of some fish species has been linked to visibility during survey trawls (used to measure escapement). 2. Water clarity increased in nearshore areas of western Lake Erie by the early 1990s, following passage of legislation in 1972 to improve water quality (e.g. reduce phosphorus loading) and the invasion of dreissenid mussels (Dreissena spp.) beginning in 1987. 3. We hypothesised that increased water clarity in Lake Erie resulted in decreased catchability of young‐of‐year (age‐0) yellow perch (Perca flavescens Mitchill) during daylight compared to during night. We used a two‐tiered modelling approach to test this hypothesis on the ratio (R) of catch per hour (CPH) during night to CPH during daylight in bottom trawl surveys conducted during 1961–2005. 4. First, we examined seven a priori models. The first model, the ‘null’ model, represented no change in R over time. Three more models tested whether the timing of the change in R was associated with passage of water quality legislation only, dreissenids only (two‐period models) and both legislation and dreissenids (three‐period models). Three additional models included a 3‐year lag before the effects of legislation, dreissenids or both occurred. Secondly, all possible two‐ and three‐period models with a minimum of 2 years per time period were explored a posteriori. The a posteriori procedure determined the temporal transitions to higher R that were best supported by the data, without regard to a priori hypotheses. 5. Night CPH was greater than daylight CPH in 3 of 11 years during 1961–72, in 10 of 15 years during 1973–87, and in 14 of 18 years during 1988–2005. During 1991–2005 night CPH exceeded daylight CPH in all years except one, and night CPH was more than twice daylight CPH in 10 years during this period. 6. The best a priori model had two periods, with a break between 1990 and 1991, corresponding to 3 years after the dreissenid invasion. Similarly, the best two‐ and three‐period a posteriori models both had breaks between 1990 and 1991. The results supported our hypothesis that age‐0 yellow perch exhibited a transition to lower catchability during daylight compared to night, and the timing of the transition coincided with the establishment of dreissenid mussels. 7. The most plausible mechanism for our results was increased visibility of the trawl during daylight, resulting in increased avoidance of the trawl. These results have potential applications wherever non‐native mussels have increased water clarity.     

Uncertainties in predicting rice yield by current crop models under a wide range of climatic conditions

Predicting rice (Oryza sativa) productivity under future climates is important for global food security. Ecophysiological crop models in combination with climate model outputs are commonly used in yield prediction, but uncertainties associated with crop models remain largely unquantified. We evaluated 13 rice models against multi‐year experimental yield data at four sites with diverse climatic conditions in Asia and examined whether different modeling approaches on major physiological processes attribute to the uncertainties of prediction to field measured yields and to the uncertainties of sensitivity to changes in temperature and CO₂ concentration [CO₂]. We also examined whether a use of an ensemble of crop models can reduce the uncertainties. Individual models did not consistently reproduce both experimental and regional yields well, and uncertainty was larger at the warmest and coolest sites. The variation in yield projections was larger among crop models than variation resulting from 16 global climate model‐based scenarios. However, the mean of predictions of all crop models reproduced experimental data, with an uncertainty of less than 10% of measured yields. Using an ensemble of eight models calibrated only for phenology or five models calibrated in detail resulted in the uncertainty equivalent to that of the measured yield in well‐controlled agronomic field experiments. Sensitivity analysis indicates the necessity to improve the accuracy in predicting both biomass and harvest index in response to increasing [CO₂] and temperature.     

In situ near infrared spectroscopy for analyte‐specific monitoring of glucose and ammonium in streptomyces coelicolor fermentations

There are many challenges associated with in situ collection of near infrared (NIR) spectra in a fermentation broth, particularly for highly aerated and agitated fermentations with filamentous organisms. In this study, antibiotic fermentation by the filamentous bacterium Streptomyces coelicolor was used as a model process. Partial least squares (PLS) regression models were calibrated for glucose and ammonium based on NIR spectra collected in situ. To ensure that the models were calibrated based on analyte‐specific information, semisynthetic samples were used for model calibration in addition to data from standard batches. Thereby, part of the inherent correlation between the analytes could be eliminated. The set of semisynthetic samples were generated from fermentation broth from five separate fermentations to which different amounts of glucose, ammonium, and biomass were added. This method has previously been used off line but never before in situ. The use of semisynthetic samples along with validation on an independent batch provided a critical and realistic evaluation of analyte‐specific models based on in situ NIR spectroscopy. The prediction of glucose was highly satisfactory resulting in a RMSEP of 1.1 g/L. The prediction of ammonium based on NIR spectra collected in situ was not satisfactory. A comparison with models calibrated based on NIR spectra collected off line suggested that this is caused by signal attenuation in the optical fibers in the region above 2,000 nm; a region which contains important absorption bands for ammonium. For improved predictions of ammonium in situ, it is suggested to focus efforts on enhancing the signal in that particular region. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Response in the water quality of the Salton Sea,California, to changes in phosphorus loading: an empirical modeling approach

Salton Sea, California, like many other lakes, has become eutrophic because of excessive nutrient loading, primarily phosphorus (P). A Total Maximum Daily Load (TMDL) is being prepared for P to reduce the input of P to the Sea. In order to better understand how P-load reductions should affect the average annual water quality of this terminal saline lake, three different eutrophication programs (BATHTUB, WiLMS, and the Seepage Lake Model) were applied. After verifying that specific empirical models within these programs were applicable to this saline lake, each model was calibrated using water-quality and nutrient-loading data for 1999 and then used to simulate the effects of specific P-load reductions. Model simulations indicate that a 50% decrease in external P loading would decrease near-surface total phosphorus concentrations (TP) by 25–50%. Application of other empirical models demonstrated that this decrease in loading should decrease near-surface chlorophyll a concentrations (Chl a) by 17–63% and increase Secchi depths (SD) by 38–97%. The wide range in estimated responses in Chl a and SD were primarily caused by uncertainty in how non-algal turbidity would respond to P-load reductions. If only the models most applicable to the Salton Sea are considered, a 70–90% P-load reduction is required for the Sea to be classified as moderately eutrophic (trophic state index of 55). These models simulate steady-state conditions in the Sea; therefore, it is difficult to ascertain how long it would take for the simulated changes to occur after load reductions. Guest editor: S. H. Hurlbert The Salton Sea Centennial Symposium. Proceedings of a Symposium Celebrating a Century of Symbiosis Among Agriculture, Wildlife and People, 1905–2005, held in San Diego, California, USA, March 2005.