Browsing by Author "Ikumi, David S"

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    Open Access
    A System-Wide Model for Solid Waste Separation and Food Waste Discharge to Sewer Systems
    (2022) Angula, Shalongo; Ikumi, David S; Gaszynski, Chris
    The emergence of the circular economy, together with the changing paradigms in resource and environmental management, has resulted in a call to (1) convert wastewater treatment plants (WWTPs) to water resource recovery facilities (WRRF) and (2) diversion of organic waste (i.e., food waste) from landfills. Due to excess anaerobic digester (AD) capacities at most WWTPs, it has been proposed to co-digest sewage sludge and food waste in the AD at WWTPs to enhance resources (mainly energy and nutrient) recovery. However, suitable options for sustainable food waste handling (i.e., separation and transport) and the characteristics of food waste have not been established, particularly in South Africa. Without characterising food waste, it is impossible to include it in WWTP simulation models. In this study, food waste and sewage sludges were limited to the household food waste and primary sludge categories, respectively. A detailed review on alternative sustainable solid waste separation and food waste transport systems was carried out and a review paper was submitted to Environmental Challenges journal for publication. The experimental investigation of the study focused on identifying the biodegradable organic composition of selected substrates, i.e., primary sludge (PS), food waste, and PS and food waste blend. PS was obtained from Belville Wastewater Treatment Works (BWWTW) in Cape Town, while food waste was manually simulated. The augmented biomethane potential (ABMP) experiment was used to obtain the required research data. The ABMP data was used to determine the substrates' biodegradable composition. The biodegradable composition was carried out using two approaches. The first approach is the mass balanced bioprocess stoichiometric calculations, which used the measured start and end concentrations of the ABMP experiment. The second approach is the parameter estimation procedure, which used the mass balanced steady-state AD model of Ikumi et al. (2015) together with its built-in parameter estimation function. With the exception of methane COD produced, there were slight to moderate differences between the measured and modelled experiment results. However, the modelled experiments produced significantly higher methane COD than the measured experiment, suggesting a high-level error associated with the gas measurement. As a result, the modelled experiment and the substrates' composition obtained using parameter estimation were chosen to be more accurate and reliable. The results revealed that anaerobic digestion of food waste and co-digestion of primary sludge and food waste produces 41% and 21% more methane than the anaerobic digestion of primary sludge, respectively. The methane produced is equivalent to the potential energy recoverable. These findings suggest that diverting food waste from landfills to WWTP's AD systems can potentially enhance energy recovery. This highlights the potential need to revise urban wastewater systems to include solid waste separation and food waste diversion to AD systems to enhance resource recovery.
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    Open Access
    Anaerobic Digestion Steady State model parameter estimation for determination of waste activated sludge characteristics
    (2021) Du Toit, Johan; Ikumi, David S
    Phosphorus (P) is an essential nutrient which supports growth and life. A need has developed to recycle P due it being a finite mined resource. At present, most P is lost due to runoff or wastewater (WW) effluent and ending up in rivers and oceans. In order to recycle P and other nutrients, Wastewater Treatment Plants (WWTPs) will need to be converted to Water and Resource Recovery Facilities (WRRFs). However, for WRRFs to be feasible, a better understanding of the current models predicting the fate of P and other material components in place are required. The objective of this study is to utilise augmented batch tests to determine the characteristics of the Waste Activated Sludge (WAS) containing Polyphosphate Accumulating Organisms (PAOs) from a full-scale WWTP as input variables in the Steady State (SS) Anaerobic Digestion (AD) model to ensure accurate prediction of AD performance. The experimental setup used in this research consisted of two completely mixed laboratory scale (20 litres volume, mesophilic 36 ̊C) Anaerobic Digesters (ADrs). The ADrs were operated at SS for 15 day and 32-day Solid Retention Times (SRT) and were fed WAS from a full-scale treatment plant which consisted of a Membrane Bioreactor (MBR) Nitrification-Denitrification (ND) Biological Excess Phosphorus Removal (BEPR) Activated Sludge (AS) system. Two different methods ((i) a novel approach by Maake & Ikumi, (2021) and (ii) the method used by Harding, (2009)) were compared in determining the saturation kinetic rates and the WAS characteristics as input variables for the SS AD models. It was determined that the novel approach by Maake & Ikumi, (2021) was very reliable in determining Chemical Oxygen Demand (COD) removal, Free and Saline Ammonia (FSA), system effluent pH and total alkalinity. With respect to the Ortho-Phosphates (OP), the parent system from where the WAS is sourced, had a long SRT. This resulted in a low predicted PAO count and Poly-Phosphate (PP) content, which resulted in low amounts of Organically bound Phosphate (OrgP) being released into the Anaerobic Digester Liquor (ADL), which equated to an underprediction of OP. Due to the low PP content found in the WAS fed to the ADrs, the ADL was not fully saturated, resulting in no struvite precipitation taking place. This was accurately modelled for both Maake & Ikumi, (2021) and Ikumi, Harding & Ekama, (2013) modelling scenarios.
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    Open Access
    The development of a three phase plant-wide mathematical model for sewage treatment
    (2011) Ikumi, David S; Ekama, George A
    To aid in finding the most cost effective methods for the design and operation of wastewater treatment plants, for minimization of energy consumption and cost while maximizing nutrient recovery and improving effluent quality, the purpose of this project is to develop three phase (aqueous-gas-solid) steady state and dynamic mathematical models for the anaerobic and aerobic digestion of sludge; including waste activated sludge (WAS) produced by biological excess phosphorus removal (BEPR) plants, within a plant-wide setting.
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    Developments in anaerobic digestion modelling
    (2019) Ghoor, Tasneem; Ekama, George A; Ikumi, David S
    Anaerobic digestion (AD) is notorious for being susceptible to failure and is regarded as unstable and sensitive. Thus, to avoid failure, anaerobic digesters are frequently operated far below their optimal level. In order to run a digester closer to capacity, a better understanding of AD failure is required. Under conditions approaching failure, or during startup, intermediate products such as acetate, propionate and hydrogen accumulate. Successful AD modelling during failure requires the AD model to be suitably calibrated. Some AD models have been calibrated to the initial slow rate-limiting hydrolysis step only with the result that these models cannot be used to predict AD failure. Without adequate modelling of AD dynamics, the AD model cannot be used to model digester start-up, digester failure or even upflow anaerobic sludge bed (UASB) reactors (which have temporary failure conditions at the bottom of the bed). This study aims to develop an AD model capable of predicting failure and digester start-up conditions. Development of an improved model was accomplished by means of calibrating the AD model to a UASB reactor dataset wherein temporary failure conditions are present in the bottom of the reactor, evident by the presence of the abovementioned intermediate products. After comparing and contrasting available AD models to identify one for further development, the AD model subset (PWM_SA_AD) of plantwide model South Africa (PWM_SA) was selected because (1) it characterizes the organics’ composition using routine wastewater treatment measurements rather than carbohydrates, lipids and proteins, which is typical of other models, (2) external speciation reduces model stiffness, (3) includes aqueous, gas and solid phases for pH calculation, gas evolution and mineral precipitation and (4) contains the same components as PWM_SA enabling plant-wide modelling without needing component transformers between process units. Before calibration, PMW_SA_AD was rigorously tested for mass balance, stoichiometric and kinetic correctness. Because the UASB reactor undergoes temporary failure observed by the accumulation of AD intermediate substrates in the bottom of the bed, the glucose fed UASB reactor system of Sam-Soon et al. (1989) was modelled to calibrate the Monod kinetic constants of the acidogens, acetoclastic methanogens, acetogens and hydrogenotrophic methanogens. This required coding into WEST® (MikebyDHI, 2016), the platform on which PWM_SA runs, a six-in-series completely-mixed AD system with a solids retention factor for each digester that retained a fraction of the reactor’s solids. Determination of the parameters that required calibration was identified with sensitivity analysis. Due to the complexity of the physical, biological and aqueous interactions, many model simulations were needed to identify the important parameters with the lasso (least absolute shrinkage and selection operator) feature selection method. Not unexpectedly the most important parameters that required calibration were the retention factor for each digester in the series; and the maximum specific growth rates and the half-saturation coefficients for the four AD biomass groups, which were global parameters, i.e. for each biomass group the same values in each digester of the series applies. Stability of the complex six-in-series UASB reactor needed the initial masses in each digester to be reasonably close to the final steady-state masses. Steady-state Microsoft Excel AD spreadsheet models were set-up to calculate these initial masses. Following the calibration procedure wherein the modelled AD intermediate products matched the measurements from the UASB reactor dataset, it was expected that the pH also would be predicted well. However, this was not the case. So, the assumption of equilibrium between the headspace CO2 partial pressure and aqueous phase CO2 concentration was replaced by a rate-controlled CO2 evolution. With this correction, the predicted pH matched well with that observed along the height of the UASB reactor. The calibrated model was then tested to observe how the UASB reactor system fails irrecoverably by gradually decreasing the influent alkalinity from the dataset value of 6000 mg/L as CaCO3. Irrecoverable failure occurred at an influent alkalinity of 4200mg/L as CaCO3 because the specific growth rate of the acetoclastic methanogens, which progressively decreases the further the pH falls below 7, fell below the minimum required to utilise the high acetate concentration. The role of the sensitivity of the acetogens to hydrogen in digester failure was also tested. Counter-intuitively, it was found that this in and of itself did not cause failure but that to a degree, postponed failure because the acetogen inactivity at high hydrogen concentration delayed the acetate load on the acetoclastic methanogens. To verify the acetogen effect on failure, acetogen sensitivity to hydrogen was increased, and the alkalinity was gradually decreased. Irrecoverable failure now occurred at an influent alkalinity of 4000mg/L as CaCO3. The above modes of UASB reactor failure predicted by PWM_SA_AD were compared with ADM1 (Anaerobic Digestion Model No. 1). ADM1 was coded into PWM_SA_AD as an independent subset using the same external speciation routine. Although ADM1 has previously been documented to be incapable of predicting AD failure, this comparison showed that ADM1 predicted the same failure modes as PWM_SA_AD but at a higher influent alkalinity of 5000mg/L as CaCO3. One of the main reasons why ADM1 fails at sooner is that the specific growth rate of the acetoclastic methanogens in ADM1 is slower than in the PWM_SA_AD model calibrated to the UASB reactor data. The UASB reactor system calibrated PWM_SA_AD model was applied to model digester start-up with primary sewage sludge. This was done by adding to the single completelymixed anaerobic digester a percentage of seed and filling the rest of the volume with wastewater treatment plant effluent with 250 mg/L as CaCO3 alkalinity. The percentage of seed was the percentage of the anaerobic digester volume, which was filled with seed sludge containing the same biomass concentrations as those at steady state after start-up is complete and the set digester sludge age is reached. The hydrolysis rate of biodegradable particulate organics (BPO) was modelled with saturation kinetics (also known as Contois (1959) kinetics) with constants obtained from Sötemann et al. (2005b). Three different startup cases were investigated (1) setting the influent pump at the final steady-state flow rate but switching it off and on with either a pH controller or a Ripley ratio controller, (2) increasing the influent flow by a fixed proportion of the final steady-state flow daily (t1/t -1), where t is the start-up duration, (3) same as (2) but adding either a pH controller or a Ripley ratio controller. Two modes failure, resulting in an inability to start up, were found: (1) BPO overload which causes acetoclastic methanogen overload and surprisingly (2) acetoclastic methanogen starvation. BPO overload results in a high acetate concentration and low pH, which slow the acetoclastic methanogens below the tipping point to start up. It is exacerbated by low percentage of seed and during the slow hydrolysis and acidification of BPO, or a setpoint which is not sufficiently conservative. Acetoclastic methanogen starvation is as a result of a too conservative setpoint which prevents flow from entering the digester, thereby depriving the organisms of the substrate. Plotting the specific growth rate to the maximum specific growth rate ratio of the acetoclastic methanogens indicated that under starvation conditions, the ratio is extremely low. The reason for the low ratio is due to the low bulk liquid concentrations on which Monod kinetics depends. The limitations of Monod kinetics are made apparent here because the initial seed amount is significantly below the final steadystate mass. So, for these cases, further investigations are required to identify if saturation kinetics will allow better predictions. Through the development of the model, although the model was capable of predicting failure and start-up in line with the expected principles, it is not possible to find a unique set of kinetic constants, resulting in a degree of freedom with the choice of a maximum specific growth rate of acidogens. This degree of freedom may have been eliminated if sufficient measurements were available. Overall, the investigation provided useful insight into the mode of AD failure and difficulties regarding modelling digester start-up. There is, therefore, the scope for further additions to the study, with a specific focus on the residual COD, sludge bed measurements, gas flow and hydrogen concentration in the bed and modelling the acidogen, acetogen, acetoclastic methanogen and hydrogenotrophic methanogen specific growth rates with saturation kinetics. This will enable greater insight into the failure modes and the effect of hydrogen and growth rate kinetics on the AD system failure.
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    Open Access
    Growing an Enhanced Culture of Polyphosphate Accumulating Organisms using a University of Cape Town Membrane Bioreactor (UCTMBR) System
    (2022) Thela, Njabulo; Ikumi, David S
    Phosphorus (P) is a resource required by all living organisms and a key ingredient in fertilizers and P-based pesticides. The global increase in fertilizer demand due to the continuing increase in population and rising demand for high quality food present a risk to the current P reserves given that P is sourced from a non-renewable phosphate rock. To cope with the increased demand and promote the sustainable use of P, researchers have been investigating methods to recover P from numerous waste streams, including municipal wastewater. Between the two main P removal technology processes, namely chemical precipitation and enhanced biological phosphorus removal (EBPR), the EBPR process presents a greater potential for P recovery in a wastewater treatment plant (WWTP). This EBPR process utilizes polyphosphate accumulating organisms (PAOs), which can accumulate P as polyphosphate (a metal phosphate complex that requires much larger P quantities than the P used for nutritional purposes in the biomass anabolic process). The resulting P-rich sludge generated in EBPR activated sludge (AS) systems can be broken down during anaerobic digestion (AD; often used to treat sludge generated in WWTPs), which results in a release of the polyphosphate as orthophosphate and free metal counterions (mainly magnesium, potassium and calcium that formed part of the polyphosphate). The P released is hence found in the AD dewatering liquor that is generated during the AD sludge thickening process and can be used towards formation of struvite (via side stream struvite crystallization unit that processes AD dewatering liquor), which is a mineral product applied to supplement P in agriculture. The use of mathematical models in the design and optimization of WWTPs has significantly grown in popularity over the past few years, with the development of models that can predict the performance of different WWTP unit operations. However, the development of such models requires an in-depth understanding of the physiology of microorganisms responsible for mediation of the bioprocesses resulting in biological wastewater treatment. In the case of the EBPR process, the PAOs play a critical role. Hence a better understanding of the functions of these microorganisms can allow for greater accuracy in model predictions. The current research undertook to grow an enhanced culture of PAOs at a relatively high solids concentration. For this purpose, a laboratory-scale University of Cape Town Membrane Bioreactor Activated Sludge (UCTMBR AS) system was setup, operated, and tested. To place PAOs at an advantage, the system was fed influent rich in readily biodegradable chemical oxygen demand (RBCOD) in the form of propionate. An activated sludge biomass containing PAOs shows certain characteristics that are different from those displayed by biomass containing predominantly ordinary heterotrophic organisms (OHOs). Therefore, it was possible to ascertain the presence of PAOs in the UCTMBR AS system using wet chemistry analysis protocols. To check the accuracy and reliability of the results, chemical oxygen demand (COD), nitrogen (N), and phosphorus (P) mass balances were conducted around the system and found to be within the acceptable range. Through the careful analysis of the data collected, the fraction of PAOs (favPAO = XBG/Xv) in the bioreactor was found to be 0.62 mgAVSS/mgVSS, while that of OHOs (favOHO = XBH/Xv) was a mere 0.12 mgAVSS/mgVSS at 76 % steady state (where the percentage indicates the COD fraction of the synthetic feed comprising propionate). Evidence presented in the current manuscript shows that PAOs prefer propionate over acetate. It was also found that a high influent calcium concentration inhibits the growth of PAOs due to the formation of calcium phosphate precipitates. The presence of nitrate in the anaerobic zone significantly inhibited the PAO metabolism in the anaerobic reactor causing a deterioration in PAO activity. In summary, the current study shows that a laboratory-scale UCTMBR AS system can be used to grow an enhanced culture of PAOs at the relatively high concentrations of 3 849 mgVSS/l. Operating such a system can play an important role in the overall study of PAOs, ultimately leading to more accurate model predictions.
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    Improved tracking of phosphorus in wastewater treatment works through anaerobic digestion of p-rich sludge
    (2021) Quevauvilliers, Matthieu; Ikumi, David S; Ekama, George
    This research aims at improving the tracking of phosphorus (P) in wastewater treatment works (WWTWs) by developing a model which accurately explains the intracellular processes of phosphorus accumulating organisms (PAOs). Two major models: the “Comeau-Wentzel” model (Comeau et al., 1987) and the “Mino” model (Mino et al., 1988) were developed to explain PAO intracellular processes but the failure of these models to achieve data reconciliation when modelling the anaerobic digestion of PAOs show that they are still incomplete. Ikumi and Ekama (2019) generated stoichiometry to help model PAO intracellular processes and hypothesised that an energy transfer between the activated sludge (AS) system and the anaerobic digester (AD) might take place. This research generated a steady state (SS) anaerobic digestion model (an extension of Sӧtemann et al.'s (2005) model) to model the treatment of sludge from nitrifying-denitrifying enhanced biological phosphorus removal (NDEBPR) system and assess, through data reconciliation, which of Ikumi and Ekama's (2019) stoichiometry best models PAO behaviour. The AD model generated achieved a high degree of correlation with experimental data but was unable to conclusively identify a single biochemical pathway for PAO processes.
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    Primary sedimentation tank model with characterized settling velocity groups
    (University of Cape Town, 2020) Polorigni, Christian Leprince; Ikumi, David S; Ekama, George A
    Primary sedimentation involves the separation of solids and liquid in primary settling tanks (PSTs) of wastewater treatment systems. These physical processes are described by various settling conditions such as discrete and flocculent settling, along with other phenomena such as flocculation, coagulation, ammonification or hydrolysis. The modelling of primary sedimentation has often been overlooked because (i) it involves various intricacies that are difficult to replicate and (ii) primary sedimentation has been assumed to be an input to most of the main unit process models, including the activated sludge (AS) system and the anaerobic digestion (AD) models. Though there has been a wide range of proposed mathematical models to describe how PSTs function, the need to correctly disaggregate the total suspended solids (TSS) into realistic fractions of unbiodegradable particulate organics (UPO), biodegradable particulate organics (BPO) and inorganic settleable solids (ISS), remains. This is because PST models that are unable to correctly split the TSS into its characteristic components make incorrect assumptions. These assumptions lead to inconsistencies in predicting the compositions of the primary sludge (PS) that is fed to the AD unit and the settled wastewater (settled WW) that is treated in the AS system. Hence, it becomes difficult to correctly simulate the entire system (plant-wide) towards a holistic evaluation of system strategies. In this study, a realistic PST model was developed, with characterized settling velocity groups, within a plant-wide setting, for municipal wastewater. This involved the improvement of a current TSS-based model into a more accurate and realistic model that could account for the settling of raw wastewater particles. The model was therefore expected to predict the composition of the PS that is treated in the AD system and the composition of the settled WW that is going to the AS unit processes. This could be achieved by splitting the TSS into UPO, BPO and ISS fractions. In developing preparation of such a realistic PST model, the following objectives were established: 1. Disaggregate the TSS into realistic UPO, BPO and ISS fractions, by means of discrete particle settling modelling (Kowlesser, 2014) and the particle settling velocity distribution (PSVD) approach of Bachis et al. (2015). 2. Verify that the model is internally consistent with wastewater treatment plant (WWTP) data, by means of mathematical material mass balances and other specific scenarios. 3. Demonstrate the application and impact of such a model by performing steady state plant-wide simulations. Using the discrete particle settling approach of Kowlesser (2014), a discrete particle settling model was developed in Microsoft Excel and implemented into a dynamic PST framework in WEST® (Vanhooren et al., 2003). The discrete particle settling model was described using steady state and dynamic calculations and the insights obtained from these calculations were implemented in the current TSS-based PST model of Bachis et al. (2015). This was performed towards developing the University of Cape Town Primary Sedimentation Unit (UCTPSU). The influent raw wastewater TSS was fractionated into UPO, BPO and ISS fractions and settling proportions of these fractions were assigned to five settling velocity groups. In addition, a distinct settling velocity was assigned to each settling velocity group. Previous studies data from WRC (1984) and Ekama (2017), were used in the discrete particle settling model, which was able to reproduce PS and settled WW outputs, through steady state and dynamic calculations and under strict material mass balances. As a result, UPO, BPO and ISS settling proportions as well as settling velocities, were extracted from these calculations and used as input parameters into the UCTPSU model. This dynamic model was rigorously verified to be internally consistent with regards to strict material mass balances. The verification scenarios also included variations of high and low settling velocities as well as a combination of both high and low velocities and checking that the model was behaving as expected. The application and impact of the UCTPSU model were demonstrated using plant-wide scenarios in proposing a preliminary integration, under steady state conditions. It showed how incorrect disaggregation of the TSS into UPO, BPO and ISS fractions can lead to incorrect predictions in terms of the settled WW composition, the AS system capacity, the effluent quality, as well as the energy consumption and generation in the AS system and AD unit respectively. The investigation also revealed the need to measure key wastewater parameters such as particle settling velocities and the unbiodegradable particulate COD fraction, when it comes to realistically modelling of primary sedimentation of municipal wastewater, with the view of optimizing plant operations and tactical decision making. The study thereafter recommended the need to conduct an extensive experimental campaign to measure in-situ diurnal data, mainly in terms of settling velocities and settling proportions of UPO, BPO and ISS. It was also suggested to use the settleometer as a tool to extract these settling velocities and settling proportions, after performing biodegradability tests. As such, the data collected from the experimental campaign and the biodegradability tests could be used in calibrating the UCTPSU model and validation could be undertaken by means of full plant scale data.
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    Tracking Inorganic Solids in Biological Enhanced Phosphorus Removal Wastewater Treatment Systems
    (2022) Oodally, Adam; Ikumi, David S
    The modelling and tracking of solids in wastewater treatment plants (WWTPs) has historically been focussed on the different types of organic solids. Conversely, there is currently limited information on the composition of inorganic solids, and how they behave across different WWTP unit operations. For the biological removal of organics or nitrogen, this limited information on inorganic solids has no implications as the inorganic solids (sediments) do not interact with the biochemical processes of the WWTP units. For enhanced biological phosphorus removal (EBPR) systems, biochemical processes result in the generation of additional forms of inorganic solids. This includes the formation of polyphosphate by phosphorus accumulating microorganisms (PAOs) and precipitation of inorganic minerals (e.g., struvite). Up until now, the only test that provides information on inorganic settleable or suspended solids (ISS) is the total solids test which yields the total lumped ISS mass of sewage or sludge samples. Furthermore, although there are several models that can provide useful information on the forms and concentrations of ISS in WWTP units (Musvoto et al., 2000; Ekama et al., 2006; Kazadi et al., 2015), no experimental tests exist that can verify the assumptions or predictions of these models. The ISS in EBPR systems can potentially be made up of the following: sediments (clay, silt and sand), polyphosphate (polyP) and mineral precipitates. Based on the ionic concentrations, as well as the conditions in WWTP units, the main forms of mineral precipitates present in EBPR systems are struvite and amorphous calcium phosphate (ACP). For sludge treatment processes downstream of EBPR activated sludge (AS) systems, several assumptions are made on the forms of inorganic solids present in the sludge. For instance, prior to the anaerobic and aerobic sludge digesters, mineral precipitation is currently not simulated, and the polyP molecules are assumed to remain unchanged from the AS system to the anaerobic digesters (AD). Post anaerobic digestion, it is assumed that all polyP has been hydrolysed and the released ions participate in mineral precipitation. The objective of this research is to develop and evaluate an ISS characterisation procedure. The output of the ISS characterisation procedure is a fully characterised ISS i.e., the individual ISS components and their respective concentrations. This ISS characterisation procedure was made up of two major components: an experimental test (named as an ISS characterisation test (ICT)) and a data modelling procedure (DMP). The former is a laboratory test that can be applied to a sample to provide input data for the DMP. The approach taken towards the development of the ICT was to identify base methods from previous literature, and thereafter modifying them to provide analytical measurements to the DMP. Several potential base methods for the ICT were identified in the literature and assessed using a multicriteria decision analysis. The base method was then modified to an ICT. The DMP was developed based on the expected effect of the ICT on the sludge samples, as well as stoichiometric ratios of the different inorganic compounds. To evaluate the performance of the ICT and DMP, the sample set was made up using solution with (i) known amount of mineral precipitate, (ii) EBPR sludge, (iii) a mixture of EBPR sludge and mineral precipitate. The EBPR sludge was obtained from a parallel study that aimed at growing an enhanced culture of PAOs in a University of Cape Town (UCT) configured AS system. Through the multicriteria analysis it was deduced that the cold perchloric acid (PCA) fractionation procedure by De Haas et al. (2000) was the most suitable base method for the ICT. Short extraction times of EBPR sludge with cold PCA acid was proven to be efficient in dissolving mineral precipitates without hydrolysis of polyP molecules (De Haas et al., 2000). The cold PCA fractionation procedure was modified (to the ICT) to include more analytical measurements such as magnesium (Mg), potassium (K), calcium (Ca), free and saline ammonia (FSA) and orthophosphate (OP), such that these measurements can be used in the DMP to characterise ISS. The DMP I (denoted as DMP I for being the first attempt) was developed based on the expected effect of the cold PCA fractionation procedure on the EBPR sludge sample with mineral precipitates. The analysis of the results from the application of the ICT on the EBPR sludge samples showed significant findings. It was demonstrated that the ICT was successful in dissolving the maximum expected concentration of mineral precipitates in its PCA extracts. The application of the ICT on the EBPR sludge sample showed that the hydrolysis of polyP did occur in the PCA extract. PolyP phosphate and counter-ions (Mg, K and Ca) were released into the PCA extract. Results from the application of the ICT on a mixture of EBPR sludge and mineral precipitates showed that the PCA extract contained both mineral precipitates ions and polyP ions. The FSA measurements on the PCA extract showed that the FSA was from the dissolution of struvite only, and there was negligible N from the hydrolysis of biomass. The release of polyP phosphate was consistent for all tests carried on sludge samples. On the other hand, the release of polyP counter-ions Mg and Ca were varied amongst the test cases with sludge samples. The results of the ICT were used as input to the DMP. The output of the DMP I was significantly inaccurate. The concentration of struvite and ACP were overpredicted by 66% and 129%, respectively. The concentration of polyP (as mgP/L) was underpredicted by 28%. It was deduced that the release of polyP counter-ions into the PCA extract led to the overprediction of the mineral precipitate and the release of polyP phosphates into the PCA extract led to the underprediction of polyP phosphate concentration. Following this analysis, a second DMP was developed (DMP II) and evaluated. Using the DMP II, the error in struvite and ACP prediction improved to 15% and 25%, respectively. The error in prediction in polyP concentration increased slightly to 31%. The ICT was not successful in separating the polyP and mineral precipitates due to the hydrolysis of polyP molecules. Hence the percentage error in the prediction of the ISS constituents concentrations were high using both DMPs. The DMP II showed an improvement in the prediction of mineral precipitate concentration. However, there are several caveats to the application of DMP II. First, it depends largely on a few parameters (such as the soluble ammonium) and thus inaccurate measurements of these parameters can result in significant mispredictions form the model. Second, it depends on parameters (namely the Mg:P ratio in polyP and extent of polyP hydrolysis) that need to be calibrated for each experimental investigation. Further research is required to determine what affects these ratios and how it can be parametrised into the DMP II. Although, this research has successfully identified, developed and evaluated a potential ISS characterization procedure for EBPR systems, there is still further research that still needs to be performed on this topic to achieve a fully calibrated and validated procedure.