Transportsystem

In the northern part of the region of the Delfland Water Board eighteen pumping stations pump the waste water of almost 1.5 million people and 40,000 businesses through large diameter pressure mains to two waste water treatment plants, where is arrives as ‘influent’.

WWTP Houtrust in The Hague and WWTP Harnaschpolder in Midden-Delfland treat the waste water to become ‘effluent’, relatively clean water. The treated waste water from WWTP Harnaschpolder is pumped through two large effluent mains to the WWTP Houtrsut, about ten kilometers away. Together with the treated waste water from WWTP Houtrust, the total effluent is pumped, – with a maximum capacity of 50,000 m³ per hour – through an effluent main with a length of 2.5 kilometer, in order to discharge it into the sea, far away from the coast.

Pumping stations

Nineteen pumping influent stations take care of the transport of the municipal waste water to the WWTP’s Houtrust and Harnaschpolder.

The pumping stations form an in series connected chain of pumping stations (influent pumping stations – effluent pumping station Harnaschpolder – effluent pumping station Houtrust), which are all equipped with a ‘stand-alone’ automation systems. In order to avoid that the total influent to the treatment plants Harnaschpolder and Houtrust becomes bigger than the discharge capacity of effluent, the flows of the influent pumping stations are strictly controlled.

The pumping stations Morsestraat, Laakwijk, Leyweg and Schiestraat are equipped with large rain water tanks, which can be filled during showers of rain in order to limit the flow of water to the WWTP’s under rainy weather conditions.

The effluent pumping station of the WWTP Harnaschpolder pumps the effluent to the WWTP Houtrust, from where it is discharged, together with the effluent of the WWTP through a 2.5 kilometre long effluent main into the Northsea.

Continuity

The pumping stations are equipped with electric driven, frequency controlled pumps. In order to safeguard the continuity in case of a breakdown of a pump, an additional pump is installed at each pumping station.

A ‘stand-alone’ automation system sees to it that each pumping station can operate completely independently. The operator can log in remotely and, if required, intervene.

Basic data pumping stations

 

Nr.	Pumping station	Capacity m3/uur	Pumps	Remarks
1	Delft	8.800	3	Renovated in 2009
2	Groenhovenstraat	3.000	2	New from 2009
3	Hogeveld	240	2	Renovated in 2005
4	Laakwijk	3.400	2	Renovated in 2011
5	Lageveld	345	2	Renovated in 2003
6	Leidschendam	1.200	2	Renovated in 2009
7	Leidschenveen	840	2	Renovated in 2003
8	Leijweg	5.300	5	New from 2006
9	Lookwatering	345	2	New from 2009
10	Loosduinen	3.450	3	New from 2006
11	Monster	1.525	3	New from 2005
12	Morsestraat	11.300	3	Being renovated
13	Nootdorp	550	2	Renovated in 2004
14	Schiestraat	4.350	5	Renovated in 2004
15	Vogelwijk	150	2	Renovated in 2004
16	Duindorp	230	2	Renovated in 2004
17	Westduinweg	1.710	2	Replacement not yet started
18	Ypenburg	850	2	Renovated in 2008
19	Harnaschpolder	39.000	5	New from 2006
20	Houtrust	50.000	3	Renovated in 2006
21	Berkel	1.600	3	New from 2006

Separated systems

The influent transport system is stretched out over a vast area and comprises of various types of mains. Based on the various permissible pressures, the influent transport system is divided into several separated mains systems with different pressure heads. In this way the high pressure influent transport sys¬tem Harnaschpolder, the low pressure influent transport system Houtrust and the medium pressure influent transport system Monster were created. Pumping station Groenhovenstraat is the physical separation between the high pressure and the low pressure systems, whereas pumping station Loosduinen separates the medium pressure system from the high pressure system.

Ring structure

The high pressure transport system is provided with a ring. Under “dry weather” conditions and by making use of the storage capacity of the sewage systems, the ring makes it possible for almost all the pumping stations to discharge water through the transport system, in case of parts of the transport system will have to be taken out of operation in case of calamities or maintenance works. For this purpose system valves are installed near all intersections of mains.

Transport mains

The diameters of the mains of the influent transport system vary between 500 mm and 2.000 mm, while the effluent transport system consists of mains with diameters of 1.400 mm and 2.000 mm. The 500 mm mains are made of synthetic materials, the next larger mains, 600 mm – 900 mm, are made of concrete and the largest are made of polyethylene, concrete, glass fibre reinforces plastic and steel, or a combination thereof. Sixty percent of the entire transport system is less than 40 years old. The majority of the older mains were renovated in the past years, resulting in a transport system that is fit for its task in the years to come.