ADM1-based methodology for the characterisation of the influent sludge in anaerobic reactors.

This paper presents a systematic methodology to characterise the influent sludge in terms of the ADM1 components from the experimental measurements traditionally used in wastewater engineering. For this purpose, a complete characterisation of the model components in their elemental mass fractions and charge has been used, making a rigorous mass balance for all the process transformations and enabling the future connection with other unit-process models. It also makes possible the application of mathematical algorithms for the optimal characterisation of several components poorly defined in the ADM1 report. Additionally, decay and disintegration have been necessarily uncoupled so that the decay proceeds directly to hydrolysis instead of producing intermediate composites. The proposed methodology has been applied to the particular experimental work of a pilot-scale CSTR treating real sewage sludge, a mixture of primary and secondary sludge. The results obtained have shown a good characterisation of the influent reflected in good model predictions. However, its limitations for an appropriate prediction of alkalinity and carbon percentages in biogas suggest the convenience of including the elemental characterisation of the process in terms of carbon in the analytical program.     

A Methodology for the Breakdown of NRW into Real and Administrative Losses

The estimation of Non Revenue Water (NRW) is simple and easy for water suppliers who keep records of the system input volume and the billed authorized consumption. However, the breakdown of NRW into its two main components real and administrative which refers to the unbilled authorized consumption plus apparent losses is not an easy or straight forward task. Methods reported in the literature for the breakdown of NRW into its components are top down approach and bottom up approach. Both approaches suffer from certain limitations and shortcomings that limits their use and reduce our confidence in the results obtained by them. This paper presents a methodology that can be used to draw a line between the real and the administrative losses with an acceptable level of accuracy. This methodology is based on the fact that the administrative losses are delivered to the demand site and consequently reach the wastewater collection system whereas the real losses are lost from the system and consequently do not reach the wastewater collection system. The methodology applies water balance from the water treatment plant outlet till the inlet of the wastewater treatment plant (WWTP). The mass balance approach of the Water Evaluation And Planning (WEAP) system was implemented for this purpose. In this methodology, the breakdown of NRW into its two main components is adjusted iteratively so that the difference between WEAP calculated and measured inflow to the WWTP is minimal. The presented methodology was applied to Amman and Zarqa cities in Jordan which return their wastewater to As Samra WWTP. The results showed that this methodology is capable of dividing NRW water into its two main components with an acceptable level of accuracy.     

Automatic characterisation of primary, secondary and mixed sludge inflow in terms of the mathematical generalised sludge digester model

This paper presents the characterisation procedure of different types of sludge generated in a wastewater treatment plant to be reproduced in a mathematical model of the sludge digestion process. The automatic calibration method used is based on an optimisation problem and uses a set of mathematical equations related to the a priori knowledge of the sludge composition, the experimental measurements applied to the real sludge, and the definition of the model components. In this work, the potential of the characterisation methodology is shown by means of a real example, taking into account that sludge is a very complex matter to characterise and that the models for digestion also have a considerable number of model components. The results obtained suit both the previously reported characteristics of the primary, secondary and mixed sludge, and the experimental measurements specially done for this work. These three types of sludge have been successfully characterised to be used in complex mathematical models.     

Impact of influent data frequency and model structure on the quality of WWTP model calibration and uncertainty

Application of activated sludge models (ASMs) to full-scale wastewater treatment plants (WWTPs) is still hampered by the problem of model calibration of these over-parameterised models. This either requires expert knowledge or global methods that explore a large parameter space. However, a better balance in structure between the submodels (ASM, hydraulic, aeration, etc.) and improved quality of influent data result in much smaller calibration efforts. In this contribution, a methodology is proposed that links data frequency and model structure to calibration quality and output uncertainty. It is composed of defining the model structure, the input data, an automated calibration, confidence interval computation and uncertainty propagation to the model output. Apart from the last step, the methodology is applied to an existing WWTP using three models differing only in the aeration submodel. A sensitivity analysis was performed on all models, allowing the ranking of the most important parameters to select in the subsequent calibration step. The aeration submodel proved very important to get good NH(4) predictions. Finally, the impact of data frequency was explored. Lowering the frequency resulted in larger deviations of parameter estimates from their default values and larger confidence intervals. Autocorrelation due to high frequency calibration data has an opposite effect on the confidence intervals. The proposed methodology opens doors to facilitate and improve calibration efforts and to design measurement campaigns.     

Mathematical modelling of small wastewater treatment plants: power and limitations.

Although mathematical modelling of biological wastewater treatment processes has proved to be valuable for large-scale WWTPs (wastewater treatment plants) little experience has been acquired in the mathematical modelling of small wastewater treatment plants. This paper seeks to evaluate the applicability of mathematical modelling on small systems, which are characterized by high fluctuations in organic and hydraulic loads and little possibility for control. In order to achieve this, the paper examines the different steps in a general modelling protocol. One important bottleneck for the general use of mathematical modelling of small systems that emerges is the frequent sampling and many analyses needed for characterization of the flows while its applicability is limited. On the other hand, the determination of the model structure of a small WWTP can be quite valuable. Experiments show that tracer tests should include tests with a highly varying influent flow rate to spot independent small internal flows as these can have a significant impact on the behaviour of peak concentrations throughout the system. In addition, the model structure determination can provide useful information on dead zones, short-circuiting and mixing behaviour in the plant.     

Towards a benchmarking model for winery wastewater treatment and disposal.

We propose a benchmarking model for winery wastewater treatment systems and use it to quantitatively compare the performance of Chilean wine-making operations. The benchmarking model integrates three components: the influent characteristics, the wastewater treatment alternatives, and the location constraints. Four performance levels may be defined when plotting the available data of the wine production versus the ratio of wastewater to wine, for the French, US, and Chilean industries. Knowing where a certain system lies in this diagram helps to quantify the gap between the current and a target performance, and to set performance goals for planned expansions. The analysis of construction and operating costs of treatment systems currently in operation in Chile shows that similar compliance levels can be achieved at remarkably different costs. A steep decrease in the unitary cost is observed as wastewater flow increases; yet, the treatment alternative for achieving that cost may change. Further selection is obtained when location constraints are considered, including stringent discharge standards and proximity to urban settlements. The application of this simple benchmark model to three Chilean winery facilities shows how it produces meaningful quantitative and qualitative results. However, there is still ample room to improve this benchmarking model by considering additional complexity, including technical detail in the treatment options and costs related to technology conversion.     

Optimal biodegradation of phenol and municipal wastewater using a controlled sequencing batch reactor.

This work presents the results of the application of an optimally controlled influent flow rate strategy to biodegrade, in a discontinuous reactor, a mixture of municipal wastewater and different concentrations of phenol when used as a toxic compound model. The influent is fed into the reactor in such a way to obtain the maximal degradation rate avoiding the inhibition of the microorganisms. Such an optimal strategy was able to manage increments of phenol concentrations in the influent up to 7000 mg/L without any problem. It was shown that the optimally controlled influent flow rate strategy is a good and reliable tool when a discontinuous reactor is applied to degrade an industrial wastewater.     

Calibrating a side-stream membrane bioreactor using Activated Sludge Model No. 1.

Membrane bioreactors (MBRs) are attracting global interest but the mathematical modeling of the biological performance of MBRs remains very limited. This study focuses on the modeling of a side-stream MBR system using the Activated Sludge Model No. 1 (ASM1), and compares the results with the modeling of traditional activated sludge processes. ASM1 parameters relevant for the long-term biological behaviour in MBR systems were calibrated (i.e. Y(H) = 0.72 gCOD/gCOD, Y(A) = 0.25 gCOD/gN, b(H) = 0.25 d(-1), b(A) = 0.080 d(-1) and f(p) = 0.06), and generally agreed with the parameters in traditional activated sludge processes, with the exception that a higher autotrophic biomass decay rate was observed in the MBR. Influent wastewater characterization was proven to be a critical step in model calibration, and special care should be taken in characterizing the inert particulate COD (X(I)) concentration in the MBR influent. It appeared that the chemical-biological method was superior to the physical-chemical method. A sensitivity analysis for steady-state operation and DO dynamics suggested that the biological performance of the MBR system (the sludge concentration, effluent quality and the DO dynamics) are very sensitive to the parameters (i.e. Y(H), Y(A), b(H), b(A) micro(maxH) and micro(maxA), and influent wastewater components (X(I), S(s), X(s) and S(NH)).     

SBR法处理煤化工废水中石油烃类的试验研究

采用序批式(SBR)活性污泥法处理煤化工废水.通过分析不同周期、进水浓度、pH、温度、DO与处理效果之间的关系,确定了SBR法处理煤化工废水的的最佳运行参数.试验结果表明,在SBR处理周期为24 h的条件下,进水CODCr为1200～1400 mg/L,石油烃类为50～70 mg/L,pH为6.8～7.1,DO为3.5 mg/L左右,温度约为25℃时,该工艺对CODCr和石油烃类去除效果较好,去除率分别为85％和76％.该工艺具有投资少、操作简单、运行费用低等特点.     

印染废水起始惰性溶解有机物的测定

介绍4种测定起始惰性溶解有机物的方法,比较了各种方法的优缺点及适用情况。利用方法四对印染废水起始惰性溶解有机物的含量进行了测定,结果表明该种废水单纯应用生物法处理难以满足排放标准的要求,必须辅以物化处理系统。起始惰性溶解有机物的测定是应用活性污泥数学模型模拟废水生物处理过程的基础。     

Evaluation of performance and microbial ecology of sequencing batch reactor and membrane bioreactor treating thin-film transistor liquid crystal display wastewater

In Taiwan, a substantial amount of thin-film transistor liquid crystal display (TFT-LCD) wastewater is produced daily due to an increasing production of the opto-electronic industry in recent years. The main components of TFT-LCD wastewater include dimethyl sulphoxide (DMSO), monoethanolamine (MEA), and tetra-methyl ammonium hydroxide (TMAH), which are recognized as non-or slow-biodegradable organic compounds and limited information is available regarding their biological treatablility. This study was conducted to evaluate the long-term performance of two bioreactors, anaerobic-aerobic (A/O) sequencing batch reactor (SBR) and aerobic membrane bioreactor (MBR), treating synthetic TFT-LCD wastewater containing DMSO, MEA, and TMAH with different loadings. For the A/O SBR, the influent wastewater was composed of 800 mg MEA/L, 430 mg DMSO/L, and 90 mg TMAH/L, respectively. After reaching steady-state, SBR was able to achieve more than 99% degradation efficiencies for the three compounds examined. For the case of aerobic MBR, the influent wastewater was composed of 550 mg MEA/L, 270 mg DMSO/L, and 330 mg TMAH/L, respectively, and degradation efficiencies for the three compounds achieved more than 99%. Although both different reactors shared similar and satisfactory degradation efficiencies for DMSO, MEA, and TMAH, the microbial ecology of these two reactors, as elucidated with molecular methods, was apparently different. The 16S rDNA-based cloning/sequencing results indicated that the dominant sequences retrieved from the aerobic MBR, including Hyphomicrobium denitrificans, Hyphomicrobium zavarzinii, Rhodobacter sp., and Methyloversatilis universalis, showed a clear linkage to their physiological properties of DMSO and TMAH degradation. On the other hand, Zoogloea sp., Chlorobium chlorochromatii, Agricultural soil bacterium, and Flavosolibacter ginsengiterrae were proliferated in the A/O SBR Run1, while Thiobacillus sp., Nitrosomonas sp., Thauera aromatica and Azoarcus sp. became dominant in Run2. Furthermore, the sequences retrieved from different reactors were used to establish the terminal restriction fragment length polymorphism (TRFLP) fingerprint methodology for monitoring the dynamics of dominant degrading bacteria in the aerobic MBR treating TFT-LCD wastewater.     

Evaluation of sewer infiltration/inflow using COD mass flux method: case study in Prague

The combined sewer system of the City of Prague, similar to other relevant locations, is strongly affected by infiltrating waters. The knowledge of their volume is one of the important parameters with respect to sewer system operation, maintenance and reconstruction. The methodology is based on the variation of diurnal chemical oxygen demand (COD) load and continuous water quality monitoring using in-line absorption spectrometry. This approach allows the identification of individual components of the diurnal wastewater hydrograph, in particular the contribution of parasitic water flow to wastewater discharge. The statistical relevance was tested using Monte Carlo simulations on a 7-year data series of flow rate. The results show that application of this methodology provides specific relevant information about individual sub-catchments within an entire sewer system, particularly in terms of absolute and relative values of I/I and structural state indicators. Processing of long-term data series gives clear information about the significance of the monitoring period length for the relevance of obtained results.     

城市污水处理厂设计进水水质确定和出水水质评价

以广州市各污水处理厂的进出水水质的实测数据为例,通过概率分析,进行了城市污水处理厂设计进水水质确定和出水水质评价的尝试。这些实测数据,经过适当变换,可以与标准正态分布曲线良好符合,说明它们基本遵从正态分布规律,并更加遵从对数正态分布规律。按照保证概率确定了该地区或类似地区的城市污水处理厂的设计进水水质,并利用达标概率评价了广州市各污水处理厂的出水水质。     

Waste characterization for implementation in ADM1.

Wastewater characterization as required for implementation in ADM1 is based on the identification of the numerous concentrations of the specific compounds defined in ADM1. However, identification of the individual substrate concentrations requires specific analytical techniques and in most cases only general measurements like COD, TOC, and organic nitrogen are available. This paper describes a simple method for calculation of the lumped elemental composition of the organic substrates in the wastewater from a limited number of widely available analyses. Using the elemental composition of the lumped substrate and the elemental composition of the substrates defined in the model, the influent composition as required for input in ADM1 can be calculated. Furthermore, proper waste characterization allows for an initial analysis of the biogas flow rate and composition as well as the reactor pH that can be achieved upon organic substrate degradation, as will be demonstrated. It is hoped that the methods described in this paper will stimulate and simplify future application of ADM1.     

Generation of diurnal variation for influent data for dynamic simulation.

When using dynamic simulation for fine tuning of the design of activated sludge (AS) plants diurnal variations of influent data are required. For this application usually only data from the design process and no measured data are available. In this paper a simple method to generate diurnal variations of wastewater flow and concentrations is described. The aim is to generate realistic influent data in terms of flow, concentrations and TKN/COD ratios and not to predict the influent of the AS plant in detail. The work has been prepared within the framework of HSG-Sim (Hochschulgruppe Simulation, http://www.hsgsim.org), a group of researchers from Germany, Austria, Luxembourg, Poland, the Netherlands and Switzerland.     

Linking sanitation and wastewater treatment: from evaluation on the basis of effluent pollutant concentrations to evaluation on the basis of pollutant removal efficiencies

The evaluation of centralised wastewater treatment plants (WWTPs) in planning and management is sometimes based solely on effluent pollutant concentrations or pollutant loads. For sanitation purposes, the effluent pollutant concentrations/loads of WWTPs are important; of course, but from the point of view of wastewater treatment, the pollutant removal performance should also be evaluated. Focussing on low- and middle-income countries, especially those in tropical regions, published kinetics studies on biological WWTPs (such as oxidation ditches and aerated lagoons) are summarised in this paper. In most studies, effluent pollutant concentrations/loads are described as first-order linear functions of influent pollutant concentrations/loads. Therefore, pollutant removal efficiencies can be expressed as first-order linear functions of the reciprocal of influent pollutant concentrations/loads with negative coefficients. This implies that pollutant removal efficiencies increase with influent pollutant concentration/load increases. Based on pollutant removal efficiency functions, biological or ecological WWTPs when operating with small influent pollutant concentrations/loads should change their management to increase influent pollutant concentrations/loads in order to increase pollutant removal efficiencies. It may, however, be possible for technological development in wastewater treatment to overcome this problem.     

Indepth diagnosis of a secondary clarifier by the application of radiotracer technique and numerical modeling.

To make an indepth diagnosis of a full-scale rectangular secondary clarifier, an experimental and numerical study has been performed in a wastewater treatment facility. Calculation results by the numerical model with the adoption of the SIMPLE algorithm of Patankar are validated with radiotracer experiments. Emphasis is given to the prediction of residence time distribution (RTD) curves. The predicted RTD profiles are in good agreement with the experimental RTD curves at the upstream and center sections except for the withdrawal zone of the complex effluent weir structure. The simulation results predict successfully the well-known flow characteristics of each stage such as the waterfall phenomenon at the front of the clarifier, the bottom density current and the surface return flow in the settling zone, and the upward flow in the exit zone. The detailed effects of density current are thoroughly investigated in terms of high SS loading and temperature difference between influent and ambient fluid. The program developed in this study shows the high potential to assist in the design and determination of optimal operating conditions to improve effluent quality in a full-scale secondary clarifier.     

The possibility of using encapsulated nitrifiers for treatment of reject water coming from anaerobic digestion

Large wastewater treatment plants have to deal not only with the influent wastewater, but also with the highly concentrated reject water coming from anaerobic digestion. The aim of this work was to verify the suitability of using encapsulated nitrifiers in polyvinyl alcohol carrier (so called Lentikats Biocatalyst) at temperatures between 5 and 30 °C. For laboratory nitrification batch tests synthetic wastewater with ammonia nitrogen (Namon) concentration 10-800 mg L(-1) was used. The system has been proved to operate at the temperature of 10 °C, but not at 5 °C. It was found that the highest specific nitrification rates were observed at 30 °C and with ammonia nitrogen concentrations above 250 mg L(-1), which means that separate treatment of reject water by using encapsulated biomass seems to be an effective tool for wastewater treatment plant optimization.