This thesis deals with real time control (RTC) in urban wastewater systems, where urban wastewater systems are defined as a combination of combined sewer systems and wastewater treatment plants (WWTPs). Urban wastewater systems discharge, through combined sewer over flows (CSOs) and WWTP effluent, onto the receiving waters. Receiving waters are thus closely linked to urban wastewater systems but are not a part of it. ... Read more

Weirs are essential structures in sewer systems. Detailed knowledge on their hydraulic performance is necessary but difficult to obtain. In this research the applicability of computational fluid dynamics (CFD) simulations for deriving reliable discharge relationships for weirs where the weir chamber geometry limits the discharged flow is investigated. A unique combination of field measurements for a combined sewer overflow, lab experiments on a scale model, and CFD simulations for the scale model and prototype is available. In the CFD simulations no prior knowledge on the hydraulic behaviour of the weir was assumed to verify the application of CFD for both scientific and engineering purposes. The results show that i) unverified CFD simulations can describe the complex hydraulic behaviour occurring in the lab experiments including a flow regime change, ii) different discharge relationships are needed for different flow conditions, iii) unverified CFD is applicable to derive discharge relationships in the disturbed flow regime where backwater effects occur, but has no added value over the standard weir equation in the undisturbed regime, and iv) unverified CFD can be applied to determine the optimal sensor location. This study supplies a quantitative support to earlier publications based on unvalidated results. ... Read more

Dit is de Nederlandstalige samenvatting van het proefschrift ‘Performance evaluation of real time control in urban wastewater systems’ van Petra van Daal-Rombouts. Met haar promotie op 22 september 2017 is zij de vierde om een promotieonderzoek met succes af te ronden binnen het Kennisprogramma Urban Drainage. Dit door de afvalwatersector gefinancierde meerjarig onderzoeksprogramma levert wetenschappelijke kennis voor belangrijke vraagstukken én wetenschappelijk geschoolde vakkrachten voor stedelijk waterbeheer. Petra ontwikkelde een methodiek voor evaluatie van het nut van realtimecontrol (RTC) in stedelijke afvalwatersystemen en paste deze methodiek toe in de regio Eindhoven. Doel van de sturing is een betere kwaliteit van het ontvangend oppervlaktewater door naar het gehele afvalwatersysteem te kijken. Uit de evaluatie blijkt dat RTC het overstortingsvolume op rwzi Eindhoven beperkt met 33% zonder dat de overige overstorten meer lozen en blijken de ammoniumpieken in het effluent door de sturing tijdens buien 20% minder. Het onderzoek laat zien dat met behulp van RTC aanzienlijke winst is te behalen in het functioneren van afvalwatersystemen. De belangrijkste voorwaarde voor een succesvolle optimalisatie is inzicht in het werkelijke functioneren van het riolerings-, zuiverings- en oppervlaktewatersysteem. Hiervoor zijn gerichte metingen en een gevalideerd model van het afvalwatersysteem onontbeerlijk. De voorliggende samenvatting presenteert de voor de praktijk meest relevante resultaten van het uitgevoerde promotieonderzoek. Het proefschrift met de detailinformatie en de wetenschappelijke onderbouwing van de resultaten kunt u via http://repository.tudelft.nl/ vrij downloaden. ... Read more

Wastewater treatment plants (WWTP) typically have a service life of several decades. During this service life, external factors, such as changes in the effluent standards or the loading of the WWTP may change, requiring WWTP performance to be optimized. WWTP modelling is widely accepted as a means to assess and optimize WWTP performance. One of the challenges for WWTP modelling remains the prediction of water quality at the inlet of a WWTP. Recent applications of water quality sensors have resulted in long time series of WWTP influent quality, containing valuable information on the response of influent quality to e.g., storm events. This allows the development of empirical models to predict influent quality. This paper proposes a new approach for water quality modelling, which uses the measured hydraulic dynamics of the WWTP influent to derive the influent water quality. The model can also be based on simulated influent hydraulics as input. Possible applications of the model are filling gaps in time series used as input for WWTP models or to assess the impact of measures such as real time control (RTC) on the performance of wastewater systems ... Read more

Real time control (RTC) is increasingly seen as a viable method to optimise the functioning of wastewater systems. Model exercises and case studies reported in literature claim a positive impact of RTC based on results without uncertainty analysis and flawed evaluation periods. This paper describes two integrated RTC strategies at the wastewater treatment plant (WWTP) Eindhoven, the Netherlands, that aim to improve the use of the available tanks at the WWTP and storage in the contributing catchments to reduce the impact on the receiving water. For the first time it is demonstrated that a significant improvement can be achieved through the application of RTC in practice. The Storm Tank Control is evaluated based on measurements and reduces the number of storm water settling tank discharges by 44% and the discharged volume by an estimated 33%, decreasing dissolved oxygen depletion in the river. The Primary Clarifier Control is evaluated based on model simulations. The maximum event NH4 concentration in the effluent reduced on average 19% for large events, while the load reduced 20%. For all 31 events the reductions are 11 and 4% respectively. Reductions are significant taking uncertainties into account, while using representative evaluation periods. ... Read more

Real time control (RTC) is generally viewed as a viable method for optimising the performance of urban wastewater systems. A literature review on the performance evaluation of RTC demonstrated a lack of consensus on how to do this. Two main deficiencies were identified: omitting uncertainty analysis and applying limited evaluation periods. A general methodology to evaluate the performance of RTC in practice, that takes into account these deficiencies, is proposed. The methodology is either data or model driven and the (dis)advantages of each are discussed. In a case study for a combined sewer system with limited discharge to a WWTP, it is demonstrated that the successful application of RTC and the possibility to determine a significant effect is very much dependent on the goal. It also clearly illustrates the need for taking uncertainties into account and that careful consideration in the chosen evaluation period is required. ... Read more

Optimisation or real time control (RTC) studies in wastewater systems increasingly require rapid simulations of sewer systems in extensive catchments. To reduce the simulation time calibrated simplified models are applied, with the performance generally based on the goodness of fit of the calibration. In this research the performance of three simplified and a full hydrodynamic (FH) model for two catchments are compared based on the correct determination of CSO event occurrences and of the total discharged volumes to the surface water. Simplified model M1 consists of a rainfall runoff outflow (RRO) model only. M2 combines the RRO model with a static reservoir model for the sewer behaviour. M3 comprises the RRO model and a dynamic reservoir model. The dynamic reservoir characteristics were derived from FH model simulations. It was found that M2 and M3 are able to describe the sewer behaviour of the catchments, contrary to M1. The preferred model structure depends on the quality of the information (geometrical database and monitoring data) available for the design and calibration of the model. Finally, calibrated simplified models are shown to be preferable to uncalibrated FH models when performing optimisation or RTC studies. ... Read more

This research deals with the design and implementation of an integrated control for the WWTP of Eindhoven. The control influences the operation of the primary settling tanks and influent pumping station to reduce reduce ammonia peaks in the WWTP effluent. The control takes into account the treatment capacity of the biological tanks, the influent flows and the available storage capacity in the individual catchments. It was implemented in winter 2016 and has been operational since April 2016. Model results and preliminary measurements show that the WWTP can be operated with a reduced number of PCs for over 90% of the time ... Read more