bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling of wastewater treatment plants – how far shall we go with sophisticated modelling tools?
Authors: Glover G.C. , Printemps C. , Essemiani K. , Meinhold J.
Published: July 2007

Several levels of complexity are available for modelling of wastewater treatment plants. Modelling local effects rely on computational fluid dynamics (CFD) approaches whereas activated sludge models (ASM) represent the global methodology. By applying both modelling approaches to pilot plant and full scale systems, this paper evaluates the value of each method and especially their potential combination.

Model structure identification for ASM is discussed based on a full-scale closed loop oxidation ditch modelling. It is illustrated how and for what circumstances information obtained via CFD (computational fluid dynamics) analysis, residence time distribution (RTD) and other experimental means can be used. Furthermore, CFD analysis of the multiphase flow mechanisms is employed to obtain a correct description of the oxygenation capacity of the system studied, including an easy implementation of this information in the classical ASM modelling (e.g. oxygen transfer).

The combination of CFD and activated sludge modelling of wastewater treatment processes is applied to three reactor configurations, a perfectly mixed reactor, a pilot scale activated sludge basin (ASB) and a real scale ASB. The application of the biological models to the CFD model is validated against experimentation for the pilot scale ASB and against a classical global ASM model response. A first step in the evaluation of the potential of the combined CFD-ASM model is performed using a full scale oxidation ditch system as testing scenario.
Development and exploitation of a multipurpose CFD tool for optimisation of microbial reaction and sludge flow
Authors: Oda T. , Yano T. , Niboshi Y.
Published: July 2007

A numerical analysis technique for optimisation of microbial reaction and sludge flow has been developed in this study. The technique is based on the 3D multiphase Navier–Stokes solver with turbulence models. In order to make numerical analyses of the total processes in wastewater treatment plants possible, four numerical models, the microbial reaction model, a sludge settling model, oxygen mass transfer model from coarse bubbles, and a model from fine bubbles, are added to the solver. All parameters included in those models are calibrated in accordance with experimental results, and good agreements between calculated results and experimental results are found. Finally, this study shows that the numerical technique can be used to optimise wastewater treatment plants with an example of the operational optimisation of an intermittent agitation in anoxic reactors by coarse bubbles. With a proper appreciation of its limit and advantages, the exploitation of the CFD efficiently leads us to the right direction even though it is not quantitatively perfect.
High-Rate Nitrification Using Aerobic Granular Sludge
Authors: Tsuneda S. , Ogiwara M. , Ejiri Y. , Hirata A.
Published: July 2007

The performance of nitrifying granules, which had been produced in an aerobic upflow fluidised bed (AUFB) reactor, was investigated in various types of ammonia-containing wastewaters. When pure oxygen was supplied to the AUFB reactor with a synthetic wastewater containing a high concentration of ammonia (500 g-N/m3), the ammonia removal rate reached 16.7 kg-N/m3/day with a sustained ammonia removal efficiency of more than 80%. The nitrifying granules possessing a high settling ability could be retained with a high density (approximately 10,000 g-MLSS/m3) in a continuous stirring tank reactor (CSTR) even under a short hydraulic retention time (44 min), which enabled a high-rate and stable nitrification for an inorganic wastewater containing low concentrations of ammonia (50 g-N/m3). Moreover, the nitrifying granules exhibited sufficient performance in the nitrification of real industrial wastewater containing high concentrations of ammonia (1,000–1,400 g-N/m3) and salinity (1.2–2.2%), which was discharged from metal-refinery processes. When the nitrifying granules were used in cooperation with activated sludge to treat domestic wastewater containing organic pollutants as well as ammonia, they fully contributed to nitrification even though a part of activated sludge adhered onto the granule surfaces to form biofilms. These results show the wide applicability of nitrifying granules to various cases in the nitrification step of wastewater treatment plants.
Where is biological nutrient removal going now?
Authors: Barnard J.L. , Steichen M.T.
Published: July 2007

With more than 30 years of experience multiple options exist for removal of nitrogen and phosphorus from wastewater. Communities that were exempt from nutrient removal for many years must now comply with imposed nutrient limits, and in areas where technology-based nutrient limits have been in place communities are now faced with more stringent mass-based limits that are becoming more difficult to meet as their populations increase. Recent efforts in the industry have been focused on getting more out of existing plants, or in many cases where land is not available, in intensifying existing processes to increase capacity and/or level of treatment. This paper will discuss some of these methods and the general direction in which biological nutrient removal is developing to address these new challenges.
Low effluent nutrient technologies for wastewater treatment
Authors: Pagilla K.R. , Urgun-Demirtas M. , Ramani R.
Published: July 2007

The USEPA (2001) water quality nutrient criteria will have a significant impact on water pollution control industry due to stringent N and P requirements. This paper presents an update of findings on successful total N (TN) and total P (TP) technologies being implemented at existing wastewater treatment plants (WWTP) to achieve low TN and TP effluents and some key challenges in achieving lower levels. Plants consistently achieving <5 mg TN/L and <0.5 mg TP/L were identified from a worldwide literature search and plant data collection. Technology gaps and research needs to improve successful technologies to achieve very low TN and TP effluents are summarised in this paper. The dissolved and colloidal organic N have been identified as major challenges in achieving very low levels of TN. Technical and economic challenges to achieve very low TP effluents include alkalinity deficiency, high chemical usage, high sludge production and lack of sufficient influent BOD for biological P uptake.
Membrane chemical reactor (MCR) combining photocatalysis and microfiltration for grey water treatment
Authors: Rivero M.J. , Parsons S.A. , Jeffrey P. , Pidou M. , Jefferson B.
Published: July 2007

Urban water recycling is now becoming an important issue where water resources are becoming scarce. This paper looks at reusing grey water; the preference is treatment processes based on biological systems to remove the dissolved organic content. Here, an alternative process, photocatalysis is discussed as it is an attractive technology that could be well-suited for treating the recalcitrant organic compounds found in grey water. The photocatalytic process oxidises organic reactants at a catalyst surface in the presence of ultraviolet light. Given enough exposure time, organic compounds will be oxidized into CO2 and water. The best contact is achieved in a slurry reactor but a second step to separate and recover the catalyst is need. This paper discusses a new membrane chemical reactor (MCR) combining photocatalysis and microfiltration for grey water treatment.
Integration of sulphate reduction, autotrophic denitrification and nitrification to achieve low-cost excess sludge minimisation for Hong Kong sewage
Authors: Lau G.N. , Sharma K.R. , Chen G.H. , van Loosdrecht M.C.M.
Published: July 2007

An integrated anaerobic–aerobic treatment system of sulphate-laden wastewater was proposed here to achieve low sludge production, low energy consumption and effective sulphide control. Before integrating the whole system, the feasibility of autotrophic denitrification utilising dissolved sulphide produced during anaerobic treatment of sulphate rich wastewater was studied here. An upflow anaerobic sludge blanket reactor was operated to treat sulphate-rich synthetic wastewater (TOC = 100 mg/L and sulphate = 500 mg/L) and its effluent with dissolved sulphide and external nitrate solution were fed into an anoxic biofilter. The anaerobic reactor was able to remove 77–85% of TOC at HRT of 3 h and produce 70–90 mg S/L sulphide in dissolved form for the subsequent denitrification. The performance of anoxic reactor was stable, and the anoxic reactor could remove 30 mg N/L nitrate at HRT of 2 h through autotrophic denitrification. Furthermore, sulphur balance for the anoxic filter showed that more than 90% of the removed sulphide was actually oxidised into sulphate, thereby there was no accumulation of sulphur particles in the filter bed. The net sludge productions were approximately 0.15 to 0.18 g VSS/g COD in the anaerobic reactor and 0.22 to 0.31 g VSS/g NO3−-N in the anoxic reactor. The findings in this study will be helpful in developing the integrated treatment system to achieve low-cost excess sludge minimisation.
Production of porous carbonaceous adsorbent from physical activation of sewage sludge: application to wastewater treatment
Authors: Rio S. , Le Coq L. , Faur C. , Le Cloirec P.
Published: July 2007

With an objective of production of carbonaceous sorbent for industrial effluent treatment, physical activation by steam of biological sludge collected from the municipal wastewater treatment plant of Nantes (France) was studied and optimised using experimental design. Thus, this activation process consists of a carbonisation under N2 atmosphere at 600 °C for 1 h, followed by a thermal oxidation using steam (760 °C, 0.5 h, 2.5 L/min). The global mass yield of the process is equal to 38%. The thermal treatment allows a specific surface area of up to 225 m2/g to be reached, the porous structure being composed of both micropores and mesopores. The content of acidic surface groups is 0.71 mEq/g whereas that of basic surface groups is 0.55 mEq/g. The adsorption properties of the sorbent made from sludge are estimated with regard to various pollutants representative of industrial pollution of wastewaters and compared with those of commercial activated carbon. Whereas the adsorption capacities of organic micropollutants are quite low because of proportionality to the microporosity, the important mesoporosity of the sorbent leads to interesting properties for macromolecules removal from aqueous solutions, such as dyes(qm=175–200 mg/g). Furthermore, the surface functional groups and Ca2 +  ions within the materials allow high copper ion adsorption capacities of 140 mg/g to be obtained. Finally, a techno-economic approach shows that the sludge activation process seems to be economically competitive with regard to incineration.
Anaerobic digestion with partial ozonation minimises greenhouse gas emission from sludge treatment and disposal
Authors: Yasui H. , Matsuhashi R. , Noike T. , Harada H.
Published: July 2007

A novel anaerobic digestion process combined with partial ozonation on digested sludge was demonstrated for improving sludge digestion and biogas recovery by full-scale testing for 2 years and its performance was compared with a simultaneously operated conventional anaerobic digestion process. The novel process requires two essential modifications, which are ozonation for enhancing the biological degradability of sludge organics and concentrating of solids in the digester through a solid/liquid separation for extension of SRT. These modifications resulted in high VSS degradation efficiency of ca. 88%, as much as 1.3 times of methane production and more than 70% reduction in dewatered sludge cake production. Based on the performance, its energy demands and contribution for minimisation of greenhouse gas emission was evaluated throughout an entire study of sludge treatment and disposal schemes in a municipality for 130,000 p.e. The analysis indicated that the novel process with power generation from biogas would lead to minimal greenhouse gas emission because the extra energy production from the scheme was expected to cover all of the energy demand for the plant operation, and the remarkable reduction in dewatered sludge cake volumes makes it possible to reduce N2O discharge and consumption of fossil fuel in the subsequent sludge incineration processes.
Lessons learnt from 15 years of ICA in anaerobic digesters
Authors: Steyer J.P. , Bernard O. , Batstone D.J. , Angelidaki I.
Published: July 2007

Anaerobic digestion plants are highly efficient wastewater treatment processes with inherent energy production. Despite these advantages, many industries are still reluctant to use them because of their instability confronted with changes in operating conditions. There is therefore great potential for application of instrumentation, control and automation (ICA) in the field of anaerobic digestion. This paper will discuss the requirements (in terms of on-line sensors needed, modelling efforts and mathematical complexity) but also the advantages and drawbacks of different control strategies that have been applied to AD high rate processes over the last 15 years.
Extremum-seeking with variable gain control for intensifying biogas production in anaerobic fermentation
Authors: Liu J. , Olsson G. , Mattiasson B.
Published: July 2007

A state-dependent variable-gain control system is implemented to follow the characteristics of a laboratory-scale up-flow anaerobic fixed-bed reactor dynamically. The transition from one state to another is determined on an hourly basis, depending on difference between the setpoint of the reactor pH and its true value. Considerable improvement of the process stability – reduction of oscillation in both the reactor pH and biogas production rate during high-rate operation, has been achieved, although the control structure is simple and intuitive.
Implementation of in-line infrared monitor in full-scale anaerobic digestion process
Authors: Spanjers H. , Bouvier J.C. , Steenweg P. , Bisschops I. , van Gils W. , Versprille B.
Published: July 2007

During start up but also during normal operation, anaerobic reactor systems should be run and monitored carefully to secure trouble-free operation, because the process is vulnerable to disturbances such as temporary overloading, biomass wash out and influent toxicity. The present method of monitoring is usually by manual sampling and subsequent laboratory analysis. Data collection, processing and feedback to system operation is manual and ad hoc, and involves high-level operator skills and attention. As a result, systems tend to be designed at relatively conservative design loading rates resulting in significant over-sizing of reactors and thus increased systems cost. It is therefore desirable to have on-line and continuous access to performance data on influent and effluent quality. Relevant variables to indicate process performance include VFA, COD, alkalinity, sulphate, and, if aerobic post-treatment is considered, total nitrogen, ammonia and nitrate. Recently, mid-IR spectrometry was demonstrated on a pilot scale to be suitable for in-line simultaneous measurement of these variables. This paper describes a full-scale application of the technique to test its ability to monitor continuously and without human intervention the above variables simultaneously in two process streams. For VFA, COD, sulphate, ammonium and TKN good agreement was obtained between in-line and manual measurements. During a period of six months the in-line measurements had to be interrupted several times because of clogging. It appeared that the sample pre-treatment unit was not able to cope with high solids concentrations all the time.
Instrumentation in anaerobic treatment – research and practice
Authors: Spanjers H. , van Lier J.B.
Published: July 2007

High rate anaerobic treatment reactors are able to uncouple solids and liquid retention time, resulting in high biomass concentrations. Principal advantages of anaerobic treatment include: energy efficiency, low biomass yield, low nutrient requirement and high volumetric organic loadings. In order to facilitate small reactors operation with stable and good performance automatic process control systems in combination with on-line instrumentation are proposed. The paper reviews the development and availability of the principal instrumentation for anaerobic treatment processes. First, the most important measuring principles are discussed, followed by a review of the most important process variables with emphasis on the development of their instrumental measurement techniques and application in research. Finally, a summary of actual application of instrumentation in full-scale anaerobic treatment plants is presented.
Application of a model-based optimisation methodology for nutrient removing SBRs leads to falsification of the model
Authors: Sin G. , Villez K. , Vanrolleghem P.A.
Published: July 2007

Recently, a model-based optimisation methodology for SBR operation has been developed and an optimal operation scenario proposed to improve N and P removal in a pilot-scale SBR. In this study, this optimal operation scenario was implemented and evaluated. The results of the implementation showed that the SBR performance was improved by approximately 50 and 40% for total nitrogen and phosphorous removal, respectively, which was better than predicted by the model. However, the long-term SBR performance was found to be unstable, particularly owing to settling problems developed after the implementation. When confronted with reality, the model used for the optimisation of the operation was found to be invalid. The model was unable to predict the nitrite build-up provoked by the optimal operation scenario. These results imply that changing the operation of an SBR system using a model may significantly change the behaviour of the system beyond the (unknown) application domain of the model. This is simply because the mechanistic models currently do not cover all the aspects of activated sludge systems, e.g. settling and adaptation of the microbial community. To further improve model-application practices, expert knowledge (not contained in the models) can be valuable and should be incorporated into model-based process optimisations.
Identification of the adverse effect of nitrate on the phosphate release rate and improvement of EBPR process models
Authors: Lee S.H. , Ko J.H. , Kim J.R. , Kim Y.J. , Lee J.J. , Kim C.W. , Lee T.H.
Published: July 2007

The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, KI,NO,PAO was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no phosphate release occurred with the existence of a little nitrate even though there was sufficient SCOD. It also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO3-4-P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process.
A process-dependent real-time controller for sequencing batch reactor plants: results of full-scale operation
Authors: Wiese J. , Simon J. , Steinmetz H.
Published: July 2007

This paper presents results of a research project, in which a process-dependent real-time control (RTC) strategy for a sequencing batch reactor plant was realised in full-scale. The cycle controller is based on NH4 analysers, NO3 probes, TSS probes and sludge level probes. With this new RTC strategy it was possible to increase the treatment capacity by 50%. By implementation of the new controller the TN, TP and NH4-N treatment efficiency could be improved significantly, too. The treatment efficiency concerning COD is comparable.
Model-based evaluation of an on-line control strategy for SBRs based on OUR and ORP measurements
Authors: Corominas Ll. , Sin G. , Puig S. , Traore A. , Balaguer M. , Colprim J. , Vanrolleghem P.A.
Published: July 2007

Application of control strategies for existing wastewater treatment technologies becomes necessary to meet ever-stricter effluent legislations and reduce the associated treatment costs. In the case of SBR technology, controlling the phase scheduling is one of the key aspects of SBR operation. In this study a calibrated mechanistic model based on the ASM1 was used to evaluate an on-line control strategy for the SBR phase-scheduling and compare it with the SBR's performance using no control strategy. To evaluate the performance, reference indices relating to the effluent quality, the required energy for aeration and the treated wastewater volume were used. The results showed that it is possible to maintain optimal SBR performance in the studied system at minimal costs by on-line control of the length of the aerobic and anoxic phases.
An on-line optimisation of a SBR cycle for carbon and nitrogen removal based on on-line pH and OUR: the role of dissolved oxygen control
Authors: Puig S. , Corominas Ll. , Traore A. , Colomer J. , Balaguer M.D. , Colprim J.
Published: July 2007

A pilot plant sequencing batch reactor (SBR) was applied in a wastewater treatment plant treating urban wastewater focused on carbon and nitrogen removal. From an initial predefined step-feed cycle definition, the evolution of the on-line monitored pH and calculated oxygen uptake rate (OUR) were analysed in terms of knowledge extraction. First, the aerobic phases of the SBR cycle were operated using an On/Off dissolved oxygen (DO) control strategy that concluded with a sinusoidal pH profile that made detecting the “ammonia valley” difficult. After changing to fuzzy logic control of the dissolved oxygen and by adding an air flow meter to the pilot plant, the pH evolution and on-line calculated OUR showed a clearer trend during the aerobic phases. Finally, a proposed algorithm for adjusting the aerobic phases of the SBR for carbon and ammonia removal is presented and discussed.
Forecasting influent flow rate and composition with occasional data for supervisory management system by time series model
Authors: Kim J.R. , Ko J.H. , Im J.H. , Lee S.H. , Kim S.H. , Kim C.W. , Park T.J.
Published: July 2007

The information on the incoming load to wastewater treatment plants is not often available to apply modelling for evaluating the effect of control actions on a full-scale plant. In this paper, a time series model was developed to forecast flow rate, COD, NH+4-N and PO3-4-P in influent by using 250 days data of field plant operation data. The data for 150 days and 100 days were used for model development and model validation, respectively. The missing data were interpolated by the spline method and the time series model. Three different methods were proposed for model development: one model and one-step to seven-step ahead forecasting (Method 1); seven models and one-step-ahead forecasting (Method 2); and one model and one-step-ahead forecasting (Method 3). Method 3 featured only one-step-ahead forecasting that could avoid the accumulated error and give simple estimation of coefficients. Therefore, Method 3 was the reliable approach to developing the time series model for the purpose of this research.
Total cost minimization control scheme for biological wastewater treatment process and its evaluation based on the COST benchmark process
Authors: Yamanaka O. , Obara T. , Yamamoto K.
Published: July 2007

This paper proposes a new cost minimisation control scheme for a predenitrification type of biological wastewater treatment process and evaluates the validity of the control scheme based on the benchmark process presented by Copp. The control scheme adopting a hierarchical control structure incorporates lower-level controllers that consist of a set of local dynamic controllers and a higher-level static optimiser that provides the set points of the lower-level controllers based on the total cost index of Vanrolleghem and Gillot. Prior to benchmarking, this paper derives a simplified process model used for the optimiser, which is able to approximate the benchmark process model effectively as well as is simplified sufficiently for faster set point optimisation for on-line purposes. Numerical experiments evaluate the effectiveness of the proposed control scheme from various viewpoints including process operational and optimisation viewpoints.
Feasibility of controlling nitrification in predenitrification plants using DO, pH and ORP sensors
Authors: Ma Y. , Peng Y. , Yuan Z. , Wang S. , Wu X.
Published: July 2007

Experimental studies were carried out on a bench-scale nitrogen removal system with a predenitrification configuration to gain insights into the spatial and temporal variations of DO, pH and ORP in such systems. It is demonstrated that these signals correlate strongly with the operational states of the system, and could therefore be used as system performance indicators. The DO concentration in the first aerobic zone, when receiving constant aeration, and the net pH change between the last and first aerobic zones display strong correlations with the influent ammonia concentration for the domestic wastewater used in this study. The pH profile along the aerobic zones gives good indication on the extent of nitrification. The experimental results also showed a good correlation between ORP values in the last aerobic zone and effluent ammonia and nitrate concentrations, provided that DO in this zone is controlled at a constant level. These results suggest that the DO, pH and ORP sensors could potentially be used as alternatives to the on-line nutrient sensors for the control of continuous systems. An idea of using a fuzzy inference system to make an integrated use of these signals for on-line aeration control is presented and demonstrated on the bench-scale system with promising results. The use of these sensors has to date only been demonstrated in intermittent systems, such as sequencing batch reactor systems.
Improving the start-up of an EBPR system using OUR to control the aerobic phase length: a simulation study
Authors: Guisasola A. , Pijuan M. , Baeza J.A. , Carrera J. , Lafuente J.
Published: July 2007

The enhanced biological phosphorus removal (EBPR) process is based on enriching the sludge with polyphosphate accumulating organisms (PAO) which are scarce in conventional non-EBPR wastewater treatment plant sludge. Hence, the start-up of EBPR systems (i.e. enriching the sludge with PAO) can be very slow and complex. A simulation study of a possible improvement of the start-up of an EBPR system in a sequencing batch reactor is presented in this work. The improvement is based on reducing the length of the aerobic phase so that it coincides with the depletion of orthophosphate from the medium. This improvement, though verified by simulation to be very successful, requires a good on-line orthophosphate sensor. To avoid this technical limitation, a link between oxygen uptake rate (OUR) measurements and orthophosphate presence is proposed. This link allows the control of the aerobic phase length with OUR as a measured variable and, consequently, a considerable improvement with respect to the conventional fixed aerobic phase length operation. An improvement of 95% in the ratio of PAO to heterotrophs and an increase of 30% in the final amount of PAO in sludge is achieved with this control strategy. The kinetic mod for simulations was a modification of the Activated Sludge Model 2d.
Development and commissioning of decision support tools for sewerage management
Authors: Manic G. , Printemps C. , Zug M. , Lemoine C.
Published: July 2007

Managing sewerage systems is a highly complex task due to the dynamic nature of the facilities. Their performance strongly depends on the know-how applied by the operators. In order to define optimal operational settings, two decision support tools based on mathematical models have been developed. Moreover, easy-to-use interfaces have been created as well, aiding operators who presumably do not have the necessary skills to use modelling software. The two developed programs simulate the behaviour of both wastewater treatment plants (WWTP) and sewer network systems, respectively. They have essentially the same structure, including raw data management and statistical analysis, a simulation layer using the application programming interface of the applied software and a layer responsible for the representation of the obtained results. Four user modes are provided in the two software including the simulation of historical data using the applied and novel operational settings, as well as modes concerning prediction of possible operation periods and updates. Concerning the WWTP software, it was successfully installed in Nantes (France) in June 2004. Moreover, the one managing sewer networks has been deployed in Saint-Malo (France) in January 2005. This paper presents the structure of the developed software and the first results obtained during the commissioning phase.
Demonstration of a tool for automatic learning and re-use of knowledge in the activated sludge process
Authors: Comas J. , Rodríguez-Roda I. , Poch M. , Gernaey K.V. , Rosen C. , Jeppsson U.
Published: July 2007

Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance.
Application of a multi-channel system for continuous monitoring and an early warning system
Authors: Lee J.H. , Song C.H. , Kim B.C. , Gu M.B.
Published: July 2007

A multi-channel continuous toxicity monitoring system developed in our laboratory, based on two-stage mini-bioreactors, was successfully implemented in the form of computer-based data acquisition. The multi-channel system consists of a series of a two-stage minibioreactor systems connected by a fiber optic probe to a luminometer, and uses genetically engineered bioluminescent bacteria for the detection of the potential toxicity from the soluble chemicals. This system can be stably and continuously operated due to the separation of the culture reactor from the test reactor and accomplish easy and long-term monitoring without system shut down by abrupt inflows of severe polluting chemicals. Four different recombinant bioluminescent bacteria were used in different channels so that the modes of the samples toxicities can be reasonably identified and evaluated based upon the response signature of each channel. The bioluminescent signatures were delivered from four channels by switching one at once, while the data is automatically logged to an IBM compatible computer. We also achieved the enhancement of the system through the manipulation of the dilution rate and the use of thermo-lux fusion strains. Finally, this system is now being implemented to a drinking water reservoir and river for remote sensing as an early warning system.
Temperature-based rapid toxicity test using Ceriodaphnia dubia
Authors: Jun B.H. , Lee S.I. , Ryu H.D. , Kim Y.J.
Published: July 2007

Toxicants, which may cause the inhibition to the biological process in sewage/wastewater treatment plant, need to be monitored within short time to prevent from serious damage. A new method, Temperature-based rapid toxicity test (TempTox test) using Ceriodaphnia dubia, was developed and compared with the standard 48 hr acute bioassay (Std. 48-hr test). Inorganic toxicants of cadmium, zinc, copper, cyanide, chromium (III), chromium (VI) and organic toxicants of phenol, PCP and pesticides of BPMC, Diazinon, Fenitrothion were tested for TempTox test and Std. 48-hr test. Because the TempTox test is based on just temperature control, C. dubia neonates were exposed to toxicants under high temperature (35.5 °C) condition without any complicated pretreatment. After given exposure time of 1, 1.25, 1.5 hours, the number of the live (no toxic effect) or the dead (toxic effect) was counted with eye without the aid of any microscope and median effective concentrations (EC50 values) were determined. From the results for all toxicants, the TempTox test was proved to be as sensitive as the Std. 48-hr test with shorter-time of just 1.25–1.5 hours. Moreover, the TempTox test was further much more sensitive than alternative bioassays such as the 1-hour I.Q. test and 30-minute Microtox. The TempTox test showed a high applicability of toxicity bioassay for real sewage/wastewater treatment plant by its easiness, rapidity and sensitivity. Finally, the prototype for short-term TempTox test was introduced.
Monitoring of pH inhibition on microbial activity in a continuous flow reactor by pseudo toxic concentration (CPT) concept and time delay model
Authors: Ko J.H. , Lee S.H. , Kim J.R. , Kim Y.J. , Hwang I.S. , Lee T.H. , Kim C.W.
Published: July 2007

The pseudo toxic concentration (CPT) concept was introduced as a quantification method to describe pH as an inhibitor concentration. In this research, the applicability of the CPT concept model for the detection of pH inhibitions was expanded for a continuous flow activated sludge reactor. A pilot equipped with an inhibition detection system was installed. Inhibitory wastewater was injected for 1 h and the relative activity was calculated by the maximum respiration rate. At the same time, the coefficients for the CPT concept model were estimated. At the dynamic conditions, the estimated relative activity by the CPT concept model showed time lag compared to the measured one. However, the time lag problem was successfully resolved by introducing a transfer function into the CPT concept model. The CPT concept model combined with a transfer function (CPT + TF model) successfully tracked the variation of the relative activity under dynamic conditions. The CPT + TF model could detect 50% inhibition faster than the respirometry based method by approximately 10 min. Moreover, it had additional advantages such as being inexpensive, easy to install and simple to operate. In conclusion, the CPT + TF model was an effective and convenient detection method of pH inhibition.
Fault detection for control of wastewater treatment plants
Authors: Schraa O. , Tole B. , Copp J.B.
Published: July 2007

Interest in real-time model-based control is increasing as more and more facilities are being asked to meet stricter effluent requirements while at the same time minimizing costs. It has been identified that biological process models and automated process control technologies are being used at wastewater treatments plants throughout the world and that great potential for optimising biotreatment may exist with the integration of these two technology areas. According to our experience, wastewater treatment plants are indeed looking for ways to successfully integrate their modelling knowledge into their process control structure; however, there are practical aspects of this integration that must be addressed if the benefits of this integration are to be realised. This paper discusses the practical aspects of monitoring, filtering and analysing real sensor data with an aim to produce a reliable real-time data stream that might be used within a model-based control structure. Several real case study examples are briefly discussed in this paper.
Equipment fault diagnosis system of sequencing batch reactors using rule-based fuzzy inference and on-line sensing data
Authors: Kim Y.J. , Bae H. , Poo K.M. , Ko J.H. , Kim B.G. , Park T.J. , Kim C.W.
Published: July 2007

The importance of a detection technique to prevent process deterioration is increasing. For the fast detection of this disturbance, a diagnostic algorithm was developed to determine types of equipment faults by using on-line ORP and DO profile in sequencing batch reactors (SBRs). To develop the rule base for fault diagnosis, the sensor profiles were obtained from a pilot-scale SBR when blower, influent pump and mixer were broken. The rules were generated based on the calculated error between an abnormal profile and a normal profile, eORP(t) and eDO(t). To provide intermediate diagnostic results between “normal” and “fault”, a fuzzy inference algorithm was incorporated to the rules. Fuzzified rules could present the diagnosis result “need to be checked”. The diagnosis showed good performance in detecting and diagnosing various faults. The developed algorithm showed its applicability to detect faults and make possible fast action to correct them.
A micromachined electrochemical sensor for free chlorine monitoring in drinking water
Authors: Mehta A. , Shekhar H. , Hyun S.H. , Hong S. , Cho H.J.
Published: July 2007

In this work, we designed, fabricated and tested a disposable, flow-through amperometric sensor for free chlorine determination in water. The sensor is based on the principle of an electrochemical cell. The substrate, as well as the top microfluidic layer, is made up of a polymer material. The advantages include; (a) disposability from low cost; (b) stable operation range from three-electrode design; (c) fluidic interconnections that provide on line testing capabilities; and (d) transparent substrate which provides for future integration of on-chip optics. The sensor showed a good response and linearity in the chlorine concentration ranging from 0.3 to 1.6 ppm, which applies to common chlorination process for drinking water purification.
Monitoring of coagulation performance and determination of coagulant dosage using a pilot in-line filter
Authors: Kim S.G. , Choi K.J. , Son H.J. , Jun Y.C. , Rhee J.B. , Shon I.S. , Lee Y.D. , Kim S.H.
Published: July 2007

A rapid method using the pilot in-line filter to detect any change in coagulation performance was proposed in this study. This method attempted to detect a change in coagulant dosage and mixing intensity by evaluating the filtrate quality of the in-line filter, which took the rapidly mixed water. Since the response time of this method was less than 10 min, it could be valuable to monitor the coagulation performance. The in-line filter was found more useful without underdrain. The in-line filter was more sensitive to a change in filtrate quality without underdrain than with underdrain. A new method, which combines a jar test with the in-line filter, was proposed to determine the coagulant dosage. This method reflected the actual plant situation more accurately than a jar test.
Integrated soft sensor model for flow control
Authors: Äijälä G. , Lumley D.
Published: July 2007

Tighter discharge permits often require wastewater treatment plants to maximize utilization of available facilities in order to cost-effectively reach these goals. Important aspects are minimizing internal disturbances and using available information in a smart way to improve plant performance. In this study, flow control throughout a large highly automated wastewater treatment plant (WWTP) was implemented in order to reduce internal disturbances and to provide a firm foundation for more advanced process control. A modular flow control system was constructed based on existing instrumentation and soft sensor flow models. Modules were constructed for every unit process in water treatment and integrated into a plant-wide model. The flow control system is used to automatically control recirculation flows and bypass flows at the plant. The system was also successful in making accurate flow estimations at points in the plant where it is not possible to have conventional flow meter instrumentation. The system provides fault detection for physical flow measuring devices. The module construction allows easy adaptation for new unit processes added to the treatment plant.
Study on the introduction of hazard analysis and critical control point (HACCP) concept of the water quality management in water supply systems
Authors: Yokoi H. , Embutsu I. , Yoda M. , Waseda K.
Published: July 2007

In the latest revision in 2004, the 3rd edition, the Water Safety Plans (WSP) was newly introduced into the World Health Organization (WHO) Guidelines for Drinking Water Quality. The Hazard analysis and critical control point (HACCP) is a basic concept that underlies the WSPs, and is also known as the product quality management method in the field of food and the medical manufacturing industries. In the amendments of the Drinking Water Quality Standards in Japan, water suppliers are required to reasonably achieve both safe water and efficient water quality management. Therefore, the HACCP concept is focused as an adequate management method covering a whole process of water supply systems, in a systematic way.

The purpose of this study is to investigate a practical procedure in introducing the HACCP into water quality management in Japan. In comparison to conventional applications of the HACCP, unmanageable variations of raw water quality, continuous treatment and supply, and numerous standards of water quality items need to be considered. The HACCP system is expected to achieve a quick response to improvements in water quality, accountability towards consumers and a decrease in accidents.
Development of a coliforms monitoring system using an enzymatic fluorescence method
Authors: Morikawa A. , Hirashiki I. , Furukawa S.
Published: July 2007

A coliforms monitoring system in treated effluent of a wastewater treatment plant has been developed. In order to achieve rapid monitoring within 1 hour, an enzymatic fluorescence method without a culturing process was introduced to this system. It converts the increase rate of fluorescence intensity as enzymatic activity into the number of coliforms instead of converting fluorescence intensity itself. A flow injection analysis is used in this system for automatic measurement. Moreover, it is equipped with the pre-filtering unit to remove the interfering substances in the suspended solids causing deterioration in measurement precision. The good relationship (correlation coefficient of 0.90) between the obtained values using this system and the analysed values using the conventional direct counting method was observed in a test at an existing wastewater treatment plant.
SBR on-line monitoring by set-point titration
Authors: Fiocchi N. , Ficara E. , Canziani R. , Luccarini L. , Ciappelloni F. , Ratini P. , Pirani M. , Mariani S.
Published: July 2007

The applicability of set-point titration for monitoring biological processes has been widely demonstrated in the literature. Based on published and on-going experiences, some operating procedures have been specifically developed to be applied to SBRs, so that real-time information about the process and/or the influent can be obtained. This, in turn, would allow plant operators to select the most appropriate actions properly and timely. Five operating modes are described for the monitoring of (1) influent toxicity, (2) influent N-content, (3) nitrification capacity, (4) end of the nitrification reaction, and (5) nitrate effluent concentration, and are currently tested on the on-line titrator TITAAN (TITrimetric Automated ANalyser) which is in operation on a pilot scale SBR.
Optimal flow distribution over multiple parallel pellet reactors: a model-based approach
Authors: van Schagen K.M. , Babuška R. , Rietveld L.C. , Baars E.T.
Published: July 2007

A drinking water treatment plant has a typical configuration of parallel lanes to provide safe drinking water 24 h a day. A new approach for optimising the production of drinking water treatment plants is proposed. This approach is applied to the softening process step and shows promising results in terms of cost reduction by optimising the water distribution over several parallel reactors. The proposed scheme relies on optimal model-based control of a single softening reactor and the use of a bypass.
Effects of solid retention time on the performance of submerged anoxic/oxic membrane bioreactor
Authors: Ng H.Y. , Tan T.W. , Ong S.L. , Toh C.A. , Loo Z.P.
Published: July 2007

In this study, four similar bench-scale submerged Anoxic/Oxic Membrane Bioreactors (MBR) were used simultaneously to investigate the effects of solids retention time (SRT) on organic and nitrogen removal in MBR for treating domestic wastewater. COD removal efficiencies in all reactors were consistently above 94% under steady state conditions. Complete conversion of NH4+-N to NO3--N was readily achieved over a feed NH4+-N concentration range of 30 to 50 mg/L. It was also observed that SRT did not significantly affect the nitrification in the MBR systems investigated. The average denitrification efficiencies for the 3, 5, 10 and 20 days SRT operations were 43.9, 32.6, 47.5 and 66.5%, respectively. In general, the average effluent nitrogen concentrations, which were mainly nitrate, were about 22.2, 27.6, 21.7 and 13.9 mg/L for the 3, 5, 10 and 20 days SRT systems, respectively. The rate of membrane fouling at 3 days SRT operation was more rapid than that observed at 5 days SRT. No fouling was noted in the 10 days and 20 days SRT systems during the entire period of study.
Comparison of membrane biofouling in nitrification and denitrification for the membrane bioreactor (MBR)
Authors: Jang N. , Ren X. , Choi K. , Kim I.S.
Published: July 2007

Batch filtration tests were conducted to compare the characteristics of membrane biofouling with regard to nitrification and denitrification. A Modified Fouling Index (MFI) was obtained using a stirred cell tester. The denitrification assays showed higher membrane fouling rates than the nitrification assays.The fouling became worse, not only due to pore blocking resistance, but also from cake layer resistance after denitrification. The Extracellular Polymeric Substances (EPS) concentration and relative hydrophobicity were decreased after denitrification, resulting in floc deterioration. The floc deterioration was assumed to have increased the cake layer resistance in the filtration test. The protein Soluble Microbial Products (SMP) concentration, portion of high molecular weight in carbohydrate SMP and relative hydrophobicity were increased after denitrification, which was assumed to cause membrane pore blocking. The changes in the EPS and SMP characteristics were the main fouling parameters in denitrification.