Alferink - Urban water management - paper vs 2

WPC 2016, September 15 – 16, Cape Town International conference Centre, South Africa

Urban water management: Principles, design and application

By

Frans Alferink, Wavin Overseas, The Netherlands

SYNOPSIS In creating sustainable solutions for urban areas, water and energy are key issues. This paper describes the different challenges we are facing in managing water. This includes the aquifers, potable water, Waste water and Storm water, as well as the management of solid waste in the streets. It also discusses how the solutions need to fit into the urban environment. The availability of space, the mobility of people and the effects on the economical- and social processes are amongst others important parameters in the process to move to a higher degree of sustainability. It is very difficult to upsize existing water and waste water systems in cities which may have grown several times beyond their original scale. Next to that, many of the existing water&waste water systems have even lost their initial capacity down to levels as low as 50% of the original. Methods exist however, to re-instate the original design capacity without digging. An example is given of a comparison in effort and environmental loading (CO2, energy) between an open cut replacement and a NO-Dig solution using Compact Pipe. On the potable water side, the example of The Netherlands is shown and also it is shown how the designer can influence the future energy demand by choosing specific solutions when designing new installations. For the issue of storm water management, an example is shown how it has been possible to create a sustainable solution, meaning avoiding mixing of the three main water qualities, avoiding flooding and destruction of infrastructure which frequently is a consequence of flooding. Two solutions are shown for managing the storm water from a site, one which uses a lot of energy and another, smart design, avoiding the use of energy, the latter being the solution that is more sustainable. INTRODUCTION Almost every day there are examples of cities flooded by storm water after periods of heavy rain.

Climate change is one of the causes of this problem, but also a lack of maintenance of rivers and

open waters, poor functioning storm water channels and pipes, in-sufficient capacity of

(combined) sewers and a lack of urban planning in general, contribute to the development of that

problem.

So it is not just one cause, meaning that focusing on integral solutions are therefore the way

forward in obtaining step by step a sustainable solution. Such integral solutions are only possible

with a good overall (urban and sub-urban) planning and by having regulations in place.


Solutions that are usually provided, focus mostly on one specific issue and neglect the

continuity of the total system. Solving the problem locally by discharging the stormwater quickly

to the street solves the problem of an individual but not of the society. There are examples

where river flooding is tried to be solved by civils works around the river. Whereas at the same

time, the origin of the storm water coming to the river is neglected.

Improving the sustainability is a matter of an integral approach in which Water, Energy, Spatial

planning and Mobility are key issues.

In this paper the focus will be on the water related issues in combination with energy.

POTABLE WATER There is no doubt about the importance of the availability of potable / drinkable water to society. The “Fluid of live” for people is without any doubt clean potable water. A precious asset. However, looking around the world, potable water is not treated as such. Many aquifers are not well protected and managed, the treatment process not well executed and the design and choice of the network not well done. When focusing on the network, then it is noticed that a lot of precious potable water never arrives to the client and gets lost / wasted on the way. Figure 1, shows an overview of levels of non-revenue water, found around the world. Figure 1: Overview of non-revenue water in the world.

Figure 1 shows that The Netherlands is the country with the lowest leakage rate. The main material used for water distribution in The Netherlands is PVC. From 1955 to 2000 PVC-U was used, and after 2000 mainly PVC-O is used. It is the PVC-O type produced in an in-line process using a rigid mandrel, that fulfills the same narrow tolerances as PVC-U, in order to guarantee a

0 10 20 30 40 50 60 70 80

Netherlands

Singapore

Japan

Germany

Denmark

Finland

Sweden

UK

Spain

France

Italy

Albania

Non-revenue water [%]


high tightness security and prolonging the very low leakage rates in the future. Amongst that also the lowest permeability and lowest bacterial growth potential are important reasons to choose PVC pipes for water distribution. Figure 2 shows an overview of the materials used in the Dutch potable water network. The use of PVC-u for water distribution started by the foundation of Wavin, partly owned by a water company. Figure 2: Materials used in Dutch potable water network

Another very important reason for using PVC however are the aspects of costs of the installed system and the lowest possible operational costs. In figure 3 the operational costs are shown for various Plastics pipes systems. The outside diameter of the pipes is the same, but due to the higher strength of the material, the internal diameter varies depending on the material strength. Figure 3: Operational costs comparison when comparing for equal outside diameter.

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140000

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in

sta

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d

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Rest

PE

PVC

Iron

AC


The energy consumption is a continuous cost factor during the lifetime of the system. It is clear that this should be considered, when making the choice for the type of pipeline system. For the water system, the costs of pumping the water into the network is a one part of the energy costs, but also the energy needed to pump the water from the aquifer to the treatment facility and the treatment itself is a considerable cost. The Dutch water companies published how much energy is presented in a cubic meter of potable water. That turned out to be around 0,52 kWh / m3. From that it is easy to calculate the loss of energy in relation to the loss of water. In figure 4 the energy loss per day is shown. It is related to the leakage rate and the daily water consumption. The 300 ltrs / capita / day water consumption is more related to the US, whereas the 130 ltrs/capita/day is more related to The Netherlands. Figure 4: Energy loss per day for a city of 100.000 inhabitants depending on daily consumption and leakage rate.

THE OLD PIPE SYSTEMS In cities, people find the most extensive services and facilities, reason why they attract more people and as a consequence, the cities grow continuously. In many cities around the world we see that individual houses are demolished and replaced by apartment buildings. Not seldom a change from one family to 50 or more families is seen. That means at that same spot there is not only a need to supply one family with water and to discharge the waste water of one family, but now the amounts are 50 fold. The old, sometimes ancient, water supply systems and waste water discharge systems have not been designed for that. In most cases however, the systems have been luckily over-designed in the past, which helps. But on the other hand the capacity of the old, sometimes ancient, systems have degraded because of encrustation, siltation, joint displacements etc. The pipe roughness has increased a lot over the years and the internal diameter has become smaller. In figure 5 an example is given where an old concrete sewer pipe is evaluated. The pipe has a diameter of 300 mm and a gradient of 0.5% The system roughness of the new pipe was 0.4. But due to siltation and cementation, as well as joint displacement and encrustation the k-value has increased in the course of time. Studies in Denmark showed that old concrete pipes may have a k-value of 15. Others have mentioned K-values of 0,6 after 4 years, 1.0 after 10 years, 2.0 after 20 years and 6 after 40 years. By replacing this pipe, the capacity can be increased again. In many situations however there is no need to


replace but Close-fit renovation technologies can be used and also the capacity re-instated, as shown in figure 5. Figure 5 : Example of re-instatement of the capacity an old sewer system by renovation

In big cities, replacing a sewer or water supply system is not really easy. The underground hides many pipes, cables, runnels etc. Deep trenching to replace for instance old sewer pipes is a risky activity as this may affect the foundation of buildings. To further illustrate the energy and cost issue an example is given where a water main is compared before and after lining with a close fit lining like Compact Pipe. Table 1: Operational costs related to an old and a renovated pipeline. Information Value

Application Water pressure

Pressure, pumped system 10 bar

Flow 250 m3/hr

Length 4.000 meter

Efficiency electrical 90%

Efficiency pumps 75%

Utilisation (operational time) 65%

Old pipe Iron

Liner PE pipe-SDR17, roughness k=0.0015, close fit , gap 2%

Case 1 Old iron, leakage rate 20%, roughness k= 2.0

Case 2 Old iron, leakage rate 20%, Encrustation 5%, roughness k = 2.5

The savings in operational costs as well as the performance improvement (less pressure loss) for the three cases is shown in figure 6.


Figure 6: Improvements realised by renovation

What can be concluded from the simulation is that the renovation of the old pipe improves the performance considerably. There is significant less pressure loss and the operational costs (energy for pumping) is considerably lower. For the end-user, the customer , the effect of renovation is at least that the pressure at the tap increases as well as the water quality. It shall be noted that the actual saving is higher than what is shown here, because now also the leakage is solved. Every cubic meter of clean water that leaks out of the system represents a certain amount of energy and costs, which with the water leaks away into the subsoil. THE COST AND ENVIROMENTAL ISSUE

Everything has a cost tag. Although costs are generally considered on an action to be taken, it should also be realised that the no-act has a cost.

Struggling with costs is mainly the struggle to obtain the best possible balance on costs related to doing nothing, social related costs, costs to the environment, cost related to the technology chosen, etc. The problem with costs, especially the costs related to doing nothing, is that some of them are very difficult to quantify, like the costs related to health issues. People that pick up diseases from poor quality drinking water, water and waste water that get mixed, ground water that contaminated, costs of disturbing traffic etc. are not so easy to quantify. The other issues is that the costs are divided over different stakeholders. They are not coming to only one party. That means that coordination and cooperation, called governance, is key.

Infrastructure that it designed and installed, has a cost. The costs can be divided in “Cost of the system”, “Cost of installing the system”, “Cost of Maintenance”, “Cost of operation” and “Cost of Dismantling”. Most designers tend to focus on the costs of the system, sometimes also on the cost of installation. The other costs however, probably because they will pop-up further on in the future, or because it is simply not part of their assignment in the project, are many times not considered. However, like the installation costs they can be a multiple of the system costs and may become a burden for the society. And what is valid for costs, is also valid for the environmental impact of the design of a new system. In order to get a better idea about this issue, below a case is discussed showing the different savings. This case shows the rehabilitation of sewer system of a German city in the period 1984-2010.

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1 2

Change of pressure loss due to

relining relative to old pipe[%]

-60

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-40

-30

-20

-10

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1 2

Change energy requirement, as a

result of renovation


Table 2 : Estimated savings by using NODIG technologies instead of replacements in a German city over a period of 25 years Aspect Information

Total length of pipe 800 km Cost saving compared to open cut Euro 70.000.000 Avoid opening roads etc 1.300.000 m2 Avoid the digging and transport of soils 2.400.000 m3 Saving truck loads 198.000

o Less traffic disruption o Less consumption of fuels o 10.000.000 kg less CO2 emission

Saving groundwater level management 215.000.000 m3 o Avoiding settlement of buildings and

foundations o Avoiding settlement of other pipes and

structures More information about the considerations regarding renovation, can be found in Lit.1,2 Information about renovation with Compact Pipe can be found in Lit.3

STORMWATER THE GAME BREAKER

In the water cycle, the amount of potable water needed to be supplied and waste water to be

collected and discharged, can be calculated quite well The storm water however is a game

breaker in designing sustainable Urban Water Systems. Although many times, one discusses

SUDS (Sustainable Urban Drainage Systems) it is important to evaluate Sustainable Water

Systems (SWS) instead. In lit. 4 more detailed information about water management can be

found.

Functions in the design

Water management also includes dirt management. In the same way as managing the water as

soon as it falls, also the dirt should be managed from the very beginning. The following 4 functions,

as shown in figure 7, are recognized in urban water management.

Figure 7: Functions in an urban water management system


The water collection from the roof can be done using a traditional roof drainage system. Especially

with bigger roofs, the so-called Quickstream system can be used to get the water quickly and

efficiently from the roof. For more details about this system, one is referred to Lit.5.

As example, an urbanization in Belgium is shown. In the green field, a business center is build.

Several office buildings are built as well as parking’s, roads and other impermeable areas. The

layout of the site is shown in figure 8.

Figure 8: Layout of building site.

The data of the site are given in table 3

Table 3: Site information

Aspect Information

Total area [ha] 7 Area impermeable (roofs, parking) 3,65 Level of the sewer / city drain relative to surface [m]

-1.5 m

Design discharge [m3/ha] 100 Max. discharge to city drain [l/s/ha] 10 Groundwater level [m] -1.9

Both, the “End of pipe” solution and the “At source” solution are shown in table 4.


Table 4: “End of Pipe” solution

Aspect End of pipe solution At source solution Pipe work 2 x 600 meter, diameter 700 mm 1200 m, Diameter 400 mm

(also possible to use a row of 1000 m aquacell)

Level at discharge point

-2.10 m (city drain at -1.5 m !!) -1.20 m

Tank 20x20x3.10 m (1.240 m3) De-centralised (pre-assembled 2.4 m3] totally 215 m3

Installation Long period, big effect on other building activities

Quick. No effect on other building activities

Required pumping capacity [l/s]

550 0

Pumping energy [kw] 2.5 0 Maintenance Pumps and tank clean out

(critical) Clean out the small road gullies. (Not criticial)

What is seen with the “End of pipe” solution is that it involves big diameter pipes, a big centrally

placed tank, high impact on the building site, maintenance of tank and pumps and energy costs

to pump the water into the city drain. The pumps would have also have to be designed as a double

system to be sure that the pumping function indeed works when needed.

With the “At source” solution the total volume of the buffer could be reduced because the water

could be infiltrated. And the excessive water can be discharged to the city drain without pumping,

because of the fact that the design could be kept very shallow. If infiltration would not have been

possible then a bigger tank would have to be built, but again it could have been a shallow tank

and the storage easily decentralized.

Figure 9: The use of prefab tanks (left) and in-situ built (right)


CONCLUSIONS

Mankind separate reality in small boxes and focus is exercised on each and every box. The idea is that if every single box is optimised, the overall is optimal. Nature however is not “boxed” but is an integral system where the performance within one of our “boxes” has an effect on the others and on the overall system. The issues of water, environment and energy are such ones. It is dangerous to separate / “box” a specific issue and forget about the rest. When looking at SUDS it is important to realise that also this is just a part of a broader water issue.

The choices initially made in the design stage do not only have an effect on the initial investments to be done to develop and install a specific system. Also in that stage the future costs related to maintenance, operation and dismantling (cyclic economy) are determined.

Water and energy are very much related to each other. It has been shown that the choice of the pipe system for potable water is decisive in the energy costs for the next 50 years!

When evaluating the old / ancient systems, then by using smart renovation techniques such as Compact Pipe, a lot of energy can be saved and the development of CO2 be prevented. This saving becomes especially considerable when rehabilitating pipes line systems in old city centres. Some specific advantages of Compact Pipe are the proven quality before installation, the environmental sound installation (no chemicals are released during installation), and the solution stays inside the old pipe and does not damage other services in the underground.

The example of storm water management has demonstrated that when an “at source” solution is used, pumping energy can be minimised or even prevented and the water systems can really be managed.

Other aspects , such as mobility, recreation and smart city design has not been discussed in this paper but are part of the Integral approach in the development of Sustainable cities.

Literature:

1. Alferink, Frans & Elzink , Wim : Renovation with Compact Pipe: quick, cost effective and

durable. 2nd Latin American Congress of Trenchless Technologies.Efficient Solutions for

UNDERGROUND INFRASTRUCTUREICTIS COLOMBIA – ISTT. Cartagena de Indias,

Colombia,17-18 May 2012

2. Elzink, Wim; trenchless replacement with dedicated PE pipes. Tenchless Middle East

2007. Dubai 12-13 March 2007

3. Alferink, Frans & Hamjediers, Ines : Important aspects when developing plans for

improving existing underground sewer, gas and water networks. 2nd Latin American

Congress of Trenchless Technologies.Efficient Solutions for UNDERGROUND

INFRASTRUCTUREICTIS COLOMBIA – ISTT. Cartagena de Indias, Colombia,17-18

May 2012

4. Alferink, Frans; Urban water management: Principles, design and application; Aprocof;

19, 20 April 2012, Bogota Colombia

5. Alferink, Frans : Water management around buildings having large roofs and other impermeable surfaces. Aprocof 2010, Bogota , Colombia

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Alferink - Urban water management - paper vs 2