Thạc Sĩ A New Empirical Sewer Water Quality Model for the Prediction of WWTP Influent Quality

1

A New Empirical Sewer Water Quality Model for the Prediction
of WWTP Influent Quality

Jeroen LANGEVELD
1,2*
, Remy SCHILPEROORT
1
, Petra VAN DAAL
2,3
, Lorenzo
BENEDETTI
4
, Youri AMERLINCK
5
, Jarno DE JONGE
6
, Tony FLAMELING
6
, Ingmar
NOPENS
5
, Stefan WEIJERS
5,6


1
Royal Haskoning DHV, P.O. Box 151, 6500 AD, Nijmegen, The Netherlands

2
Delft University of Technology, PO Box 5048, Delft, The Netherlands

3
Witteveen+Bos, P.O. Box 233, 7400 AE Deventer, The Netherlands

4
WATERWAYS srl, Via del Ferrone 88, 50023 Impruneta, Italy

5
BIOMATH, Department of Mathematical Modelling, Statistics and Bioinformatics, Ghent
University, Coupure Links 653, 9000 Gent, Belgium

6
Waterschap De Dommel, P.O. Box 10.001, 5280 DA, Boxtel, The Netherlands
*
Corresponding author
Email: [email protected]

ABSTRACT
Modelling of the integrated urban water system is a powerful tool to optimise wastewater
system performance or to find cost-effective solutions for receiving water problems. One of
the challenges of integrated modelling is the prediction of water quality at the inlet of a
WWTP. Recent applications of water quality sensors have resulted in the availability of long
time series of sewer water quality and WWTP influent quality. This time series contains a lot
of information on the response of sewer water quality to, for example, storm events. This
allows the development of empirical models to predict sewer water quality. This paper
proposes a new approach for water quality modelling, which uses the measured hydraulic
dynamics at the influent of the WWTP to derive the (measured) influent water quality. This
model can then be used as a WWTP influent generator using either measured or simulated
influent hydraulics as input.

KEYWORDS
Sewer system, empirical model, influent generator, water quality modelling

INTRODUCTION
Modelling of the integrated urban water system is a powerful tool to optimise wastewater
system performance or to find cost effective solutions for receiving water problems
(Benedetti et al., 2013a). One of the weaknesses of integrated modelling is the water quality
modelling in sewer systems, due to the limited knowledge on the physical-chemical,
biological and transport processes occurring in sewer systems (Bertrand-Krajewski, 2007).
Especially sediment transport is not very well understood and not very successfully
reproduced in deterministic models. This is partly due to the fact that it is currently not
possible to get enough data on the initial sewer sediment conditions throughout an entire
sewer network. As a consequence, a lot of effort has been put in the development of
regression models, which are validated against monitoring data. A recent successful example
of this approach is given by Dembélé et al. (2011), who developed an empirical model for
stormwater total suspended solids (TSS) event mean concentrations with rainfall depth and
antecedent dry weather period as input variables. These empirical relations, that are valid at a
combined sewer overflow (CSO) or storm sewer outfall (SSO), however, are not suitable for 13
th
International Conference on Urban Drainage, Sarawak, Malaysia, 7-12 September 2014
2

the prediction of wastewater treatment plant (WWTP) influent quality, as these models do not
predict the influent quality during dry weather flow (DWF).
Recent applications of water quality sensors have resulted in the availability of long time
series of sewer water quality and WWTP influent quality. These time series contain a lot of
information on the response of sewer water quality to e.g. storm events. This allows the
development of empirical models to predict sewer water quality at the inlet of a WWTP, such
as for example the one by Talebizadeh et al. (2014). They use a mix of statistical and
conceptual modeling techniques for synthetic generation of influent time series based on a
periodic multivariate time series model for the influent in DWF conditions and a two-state
Markov chain-gamma model for rainfall conditions. The main drawback of this approach is
that the errors in the hydrologic runoff and hydraulic sewer model cumulate. In order to
overcome this drawback, a new approach is developed and presented in this paper, which
uses the measured hydraulic behaviour at the influent of the WWTP to derive the (measured)
influent water quality. This model can then be used to predict WWTP influent water quality
using simulated influent hydraulics as input.
This paper describes the development of this new model for the WWTP Eindhoven in the
Netherlands, with flow and water level as the input variables. The paper also discusses the
transferability of the developed concept to other locations.

METHODS AND MATERIALS

System description: the Dommel River IUWS
The Dommel is a relatively small and sensitive river flowing through the city of Eindhoven
(The Netherlands) from the Belgian border (South) into the river Meuse (North), receiving
discharges from the 750,000 PE wastewater treatment plant (WWTP) of Eindhoven and from
over 200 combined sewer overflows (CSOs) in 10 municipalities. In summer, the WWTP
effluent equals the base flow of 1.5 m
3
/s of the Dommel River just upstream the WWTP. The
Dommel River does not yet meet the requirements of the European Union Water Framework
Directive (WFD). The water quality issues to be addressed are dissolved oxygen (DO)
depletion, ammonia peaks and seasonal average nutrient concentration levels (Weijers et al.
2012). Benedetti et al. (2013b) describe the set of measures required for compliance with the
WFD and the methodology applied to derive them as developed in the KALLISTO project.