Hans Korving

Deltares · Department of Hydrology

The description of intertwined ecological processes in surface waters requires a holistic approach that accounts for spatially distributed hydrological/water quality processes. This study describes a new approach to model dissolved oxygen (DO) based on linked hydrodynamic and closed nutrient cycle ecological models. Long term datasets from the Rive...

Due to a variety of contaminants in floodwater, exposure to urban pluvial flooding may pose a health risk to humans. In-sewer defects may cause increased pluvial flooding, possibly increasing health risks. This paper addresses the impact of in-sewer defects on urban pluvial flooding and, subsequently, on infection probabilities for humans. As such,...

Underground water infrastructure is essential for life in cities. The aging of these infrastructures requires maintenance strategies to maintain a minimum service level. Not all elements are equally important for the functioning of the infrastructure as a whole. Identifying the most critical elements in a network is crucial for formulating asset ma...

A question arising when considering the changing climate is whether real time control (RTC) can be considered as a ‘No Regret’ measure, i.e. can RTC maintain its proven current added-value to reduce emissions from sewage systems in the future under altered rainfall patterns and often higher extreme rainfall intensities. This study explored four cli...

Sewer performance is typically assessed using hydrodynamic models assuming the absence of in-sewer defects. As a consequence, hydraulic performance calculated by models is likely to be overestimated, while the real hydraulic performance of the sewer system remains unknown. This article introduces the concept of ‘hydraulic fingerprinting’ based on m...

In-sewer defects are directly responsible for affecting the performance of sewer systems. Notwithstanding the impact of the condition of the assets on serviceability, sewer performance is usually assessed assuming the absence of in-sewer defects. This leads to an overestimation of serviceability. This paper presents the results of a study in two re...

In common with most infrastructure systems, sewers are often inspected visually. Currently, the results from these inspections inform decisions for significant investments regarding sewer rehabilitation or replacement. In practice, the quality of the data and its analysis are not questioned although psychological research indicates that, as a conse...

The Volkerak-Zoom Lake is an enclosed part of the estuarine delta in the southwest of the Netherlands and exists as such since 1987. The current freshwater lake experienced a deterioration in water and ecological quality. Especially cyanobacteria are a serious problem. To solve this problem it is proposed to reintroduce salt water and tidal dynamic...

In biological wastewater treatment, nitrogen and phosphorous are removed by activated sludge. The process requires oxygen input via aeration of the activated sludge tank. Aeration is responsible for about 60% of the energy consumption of a treatment plant. Hence optimization of aeration can contribute considerably to the increase of energy-efficien...

The aeration of the activated sludge tank of wastewater treatment plant (WWTP) Westpoort in Amsterdam (the Netherlands) has been optimised using model based control. Discharge limits for the effluent of the treatment plant require total nitrogen (Ntot) concentrations below 10 mg/l. Ntot levels are reduced using biological nitrification-denitrificat...

Risk and uncertainty are often not taken into account in decision-making on sewer rehabilitation. However, the assessments on which the decisions are based are considerably affected by uncertainties in external inputs, system behaviour and impacts. This is a problem of growing significance. Many sewer systems need expensive rehabilitation due to th...

Sewer degradation is mainly a stochastic process. The future condition of sewers can be predicted with models based on condition states. In The Netherlands, the 'SPIRIT' model is being developed which combines expert opinion and visual inspections to predict sewer degradation. The statistical method implemented in this model is based on Bayesian st...

It is generally accepted that sewage pumping stations are directly responsible for affecting sewer system performance in terms of combined sewer overflows and flooding. However, the specific causes of pump failure are unknown. This paper presents the analysis of pump failure data provided by four sewer management authorities in The Netherlands. Pum...

Often the quality of information in sewer databases is questionable due to e.g. poor documentation and subsidence of sewers. As a result, decisions on sewer rehabilitation have to be made with unreliable or incorrect information. This paper presents an automatic validation tool for sewer database quality. This tool evaluates recency, reliability, a...

Sewage pumping stations represent an element of the sewer system, which is directly responsible for affecting serviceability; i.e., failing pumps may result in combined sewer overflows or flooding. However, failures of sewage pumps are not yet incorporated in sewer assessments due to lack of data. This paper presents the analysis of pump failure da...

Sewage pumping stations are directly responsible for affecting performance, i.e. failing pumps may result in combined sewer overflows or flooding. However, failures of sewage pumps are not yet incorporated in sewer assessments due to lack of knowledge and data. This paper presents the analysis of pump failure data provided by two sewer management a...

Assessments of sewer performance are usually based on a single computation of CSO (combined sewer overflow) volumes using a time series of rainfall as system loads. A shortcoming of this method is that uncertainties in knowledge of sewer system dimensions are not taken into account. Moreover, sewer models are rarely calibrated. This paper presents...

In decision-making on sewer rehabilitation risk and uncertainty are not taken into account. However, the assessments on which the decisions are based are considerably affected by uncertainties on external inputs, system behaviour and effects. In this paper, a risk-based approach is presented considering uncertainty in sewer system dimensions, natur...

Decisions on the rehabilitation of a sewer system are usually based on a single computation of CSO volumes using a time series of rainfall as system loads. A shortcoming of this method is that uncertainties in knowledge of sewer system dimensions are not taken into account. Besides, statistical uncertainties are left aside. This paper presents the...

In recent years, decision analysis has become an important technique in many disciplines. It provides a methodology for rational decision-making allowing for uncertainties in the outcome of several possible actions to be undertaken. An example in urban drainage is the situation in which an engineer has to decide upon a major reconstruction of a sys...

Decisions on the rehabilitation of a sewer system are usually based on a single computation of CSO volumes using a time series of rainfall as system loads. Therefore, uncertainty in knowledge of model parameters is not taken into account. Moreover, statistical uncertainties are left aside. This paper presents the effect of uncertainties in model pa...

Although the majority of management authorities for wastewater systems has automatic systems for failure reporting, the reports are not uniform. Often they consist of a combination of real failures and interpreted operational data. Moreover, operational data are generally registered at a too low frequency. In order to enhance systematic process ana...

In decision-making on sewer rehabilitation risk and uncertainty are not taken into account. However, the assessments on which the decisions are based are considerably affected by uncertainties on exter- nal inputs, system behaviour and effects. In this paper, a risk-based approach is presented considering uncer- tainty in sewer system dimensions, n...