Abstract

To ensure the sustainability and reliability of water supply infrastructure, a basic pre-condition must be applied related to its continual renewal. For renewal planning, there are a number of methods, techniques and software tools for decision-support, but in many cases most of them focus only on water mains. However, water supply systems consist of more various parts and structures than simply water pipes. Therefore, it is not appropriate to invest in renewal planning for a single part of the water supply infrastructure only. An effective and detailed evaluation of the technical condition requires the deployment of specialists and a reliable database, as well as considerable amounts of time, instrumentation and software. Therefore, it is preferable to first perform a rapid and efficient preliminary identification of problematic areas and elements of the entire water supply system. This paper presents the methodology and Technical and Energy Audit (TEA Water), as well as an effective preliminary assessment of the technical condition of water supply systems (WSSs). The paper presents the structure of proposed technical indicators, the method of their determination and evaluation, as well as including a presentation of case studies.

INTRODUCTION

The water supply infrastructure is aging and its renewal is a global issue. The huge funds to be invested in the continuous renewal of the water supply infrastructure estimate that, over the next 20 years, investment in the water supply systems in the USA will total USD 77 billion. Similarly in Canada, such investments over the next 15 years will amount to 12.5 billion dollars a year according to Al-Barqawi & Zayed (2008). In the Czech Republic, the annual investments total about 592 million euro, according to Barák (2015). The situation is similar in other European countries.

Funds for continuous renewal are restricted and therefore must be spent efficiently wherever needed most. The decisions on investments are based on Infrastructure Asset Management (IAM).

The IAM of urban water infrastructures is a set of processes, the first and most basic of which is objective knowledge of the current technical condition of existing infrastructure. Setting up the assessment criteria, metrics and targets is a crucial stage for establishing the technical audit of water supply infrastructure according to Alegre & Coelho (2012). Since 2005, the biannual LESAM (Leading-Edge Strategic Asset Management) conferences of the International Water Association have clearly demonstrated the increasing interest in and recognition of this field, according to Alegre & Almeida (2009).

Agathokleous & Christodoulou (2016) describe an expanded methodology for evaluating the condition of urban water distribution networks using a mathematical analysis of data relating to water mains as well as failure incidents for individual fittings and home connection to networks. A set of water-loss-related performance indicators and an integrated decision support system (DSS) used for the evaluation of water supply networks in some Mediterranean countries is presented by Kanakoudis et al. (2013). Potential methods of setting the degradation and residual water main service life are provided by Cabral et al. (2016).

Assessments are, to some extent, limited by legal requirements in each country. In some countries, the law lays down a relatively precise process and recommends the method of that assessment, according to Heywood et al. (2006) or US EPA (2012).

Other countries, such as the Czech Republic, do not have any legal method defined, nor a method of assessing the technical condition. Under the current laws of the Czech Republic, each water utility assesses its water supply system by the percentage of degradation in comparison with the specified ‘theoretical life’ of its individual parts and objects of water supply infrastructure. However, it is impossible to objectively compare the technical condition of various water supply systems using only the degradation method.

Therefore, as part of dealing with the project described below (in cooperation with selected Czech water utilities) a methodology has been developed that permits a preliminary assessment of the technical condition of the water supply infrastructure so as to enable efficient identification of hot-spots and parts of drinking water supply systems as well as to compare the assessed systems and their individual structures between themselves.

METHODOLOGY

The draft methodology of preliminary assessment is based on the general method, the FMEA. The FMEA method (Failure Mode and Effects Analysis) allows for semi-quantitative assessment of relevant systems and their components. Assessing systems by using the FMEA requires establishing specific technical indicators for each drinking water supply system component and structure. For each technical indicator defined, their determination method, necessary input data, physical dimensions and method of assessment and presentation are listed.

In order to assess the various components and structures of these water distribution systems, the methodology is divided, similar to the water supply system, into the following separate modules:

  • Module TEAR: water resources;

  • Module TEAT: water treatment plants;

  • Module TEAM: water transmission mains;

  • Module TEAA: water tanks;

  • Module TEAP: pumping stations;

  • Module TEAN: water distribution networks;

  • Module TEAS: water pipes.

A more detailed description of individual modules, such as the TEAN module, is shown in Tuhovčák et al. (2016). TEAR and TEAT modules are described in Kučera et al. (2016). This paper focuses on the details of the TEAP and TEAS modules, including a presentation of proposed indicators and case studies.

The total assessment of the relevant structure or part of the assessed water supply system (WSS) by the relevant module is based on evaluation of two basic parts of each structure or part of the WSS:

  • Structural–technical part (ST) – includes facilities, buildings, shafts, etc.

  • Technological–operating part (TP) – includes technologies, operational indicators, etc.

The evaluation of these specific parts consists of the following:

  • Structural–technical part (ST) part – assessment of structural–technical indicators (ST1, … ,STn), where, for each module, a set of ST indicators is proposed for each ST in order to capture the actual structural and technical condition of the assessed structure.

  • Technological–operating (TP) part – assessment of technological–operating indicators (TP1, … ,TPn), where, for each module, a set of indicators is proposed in order to capture the actual operating parameters.

Compared with the standard FMEA method, the proposed methodology is expanded by another level – factors (F). Technical indicators are not assessed directly, but their evaluation is based on a set of factors proposed for each technical indicator. A uniform four-point rating assessment system was established for each and every factor, with qualifications and recommendations for the specific score for each factor. Each factor and each technical indicator also comes with a weight, which reflects the importance of the relevant factor indicator in the proposed assessment system. The factors are the only level that is assessed on the basis of defined input data. Assessment made at higher levels (indicators, parts of structures, structures) is calculated based on the relevant indicator factor assessment.

The point ranking of factors is as follows:

  • 0 – factor not assessed, insufficient input data to assess the relevant factor;

  • 1, 2 or 3 – where the value of 1 is the most favourable condition, while the value of 3 is the least favourable condition of the factor assessment.

The technical condition assessment structure based on the proposed methodology is presented in Figure 1.

Figure 1

Structure of the technical condition assessment of a civil structure.

Figure 1

Structure of the technical condition assessment of a civil structure.

Based on the assessment, the assessed objects, their structural–technical and technological–operating parts and specific indicators may fall within the assessment categories shown in Figure 2.

Figure 2

Assessment categories.

Figure 2

Assessment categories.

This is a multi-criteria assessment. The proposed methodology is based on the weighted-sum method. For this method it is particularly important to set the weights of the individual factors and indicators. The proposed methodology defines weights on the basis of the findings and experience of the research team, as well as discussions with water utility staff. A sensitivity analysis of the influence of the proposed weights was also performed, based on the factors and indicators for real and fictitious WSSs for all seven modules.

Weight sensitivity analysis

The overall rating of the structure was originally proposed in five categories, without the intermediate stage + and −. The sensitivity analysis of the effects of the weights of the factors and indicators on the overall assessment of the structure was carried out in such a way that all structure factors were first assessed by the lowest value 1. The assessment was then changed to the opposite extreme with the highest value 3. Factors with the greatest impact on the overall evaluation of each part of each module were subsequently examined.

Testing shows that, despite the low effect of some factors, their change from 1 to 3 or vice versa may lead to a change in the overall assessment of a part of the module by one entire category. However, in practice this could mean that, if there is incomplete information about any factor and it is still assessed, this could considerably influence the final result by a single mistake or incomplete information in the input data. This is especially true when the rating approaches the boundaries between the categories.

Therefore, after consultations with water company experts, the final evaluation of WSS objects of category + and − (for example B and B+) was extended. A key role for this method is played by setting the weights for the individual factors and indicators. Therefore, great attention was paid to weights set for various levels in the sensitivity analysis. The initial weight setup was based on the findings of the research team and based on discussions with experts who have practical experience from water utilities. This setup was tested by using a random number generator with uniform distribution probability in order to generate a rating for all factors in the tested structure. All four options to assess each factor had the same probability of generation.

The results for the initial weight setup showed a tendency in the final assessment of the structure towards the middle category C. This means that the influence of the weight of a factor or indicator on specific rating levels shows its relatively small impact on the overall rating. After using a Saaty method (Saaty & Peniwati 2008), a weight review was performed. After changing the weight setting, all rated objects were reassessed by the same random factor assessment as in their initial weight setting. Achieved results make for a more balanced overall assessment of assessed structures. However, this method allows the users to adapt to these factor and indicator weight settings.

TEAP module

The TEAP module focuses on pumping stations. The structure of indicators and their factors within the TEAP module for the structural–technical part is presented in Table 1. Four TP indicators exclusively related to the technological and operating conditions of pumps, pipe distribution systems (including fittings) and surge protection of the pumping stations were subsequently proposed for the technological and operating part and its assessment.

Table 1

Structure of TEAP module indicators and factors including the weights – structural–technical part

Structural–technical part weight 
 Structural–technical indicators 0.35 
 ST1 – Condition of structures 0.40 
 F1 Condition of roof structures 0.20 
 F2 Condition of windows and doors 0.20 
 F3 Condition of floors 0.15 
 F4 Condition of walls 0.15 
 F5 Condition of ceiling structures 0.15 
 F6 Condition of metal fittings 0.15 
ST2 – Condition of storage tanks 0.40 
 F1 Condition of bottom and sludge pit 0.20 
 F2 Condition of walls 0.20 
 F3 Condition of tank inlet elements 0.15 
 F4 Condition of pipes 0.15 
 F5 Condition of roof structures 0.10 
 F6 Condition of ceiling structures 0.10 
 F7 Condition of ventilation 0.10 
ST3 – Environment at the pumping station 0.20 
 F1 Condition of building security system 0.30 
 F2 Condition of ventilation 0.20 
 F3 Condition of heating 0.20 
 F4 Hoisting system 0.20 
 F5 Lighting method 0.10 
Structural–technical part weight 
 Structural–technical indicators 0.35 
 ST1 – Condition of structures 0.40 
 F1 Condition of roof structures 0.20 
 F2 Condition of windows and doors 0.20 
 F3 Condition of floors 0.15 
 F4 Condition of walls 0.15 
 F5 Condition of ceiling structures 0.15 
 F6 Condition of metal fittings 0.15 
ST2 – Condition of storage tanks 0.40 
 F1 Condition of bottom and sludge pit 0.20 
 F2 Condition of walls 0.20 
 F3 Condition of tank inlet elements 0.15 
 F4 Condition of pipes 0.15 
 F5 Condition of roof structures 0.10 
 F6 Condition of ceiling structures 0.10 
 F7 Condition of ventilation 0.10 
ST3 – Environment at the pumping station 0.20 
 F1 Condition of building security system 0.30 
 F2 Condition of ventilation 0.20 
 F3 Condition of heating 0.20 
 F4 Hoisting system 0.20 
 F5 Lighting method 0.10 

TEAS module

The TEAS module focuses on the assessment of water mains. Figure 3 presents an example of assessing factor F1, which is related to pipe covers. This factor is part of the ST2 indicator – construction and technical design, structural–technical part of the main.

Figure 3

Structure of TEAS module indicators and factors – structural–technical part.

Figure 3

Structure of TEAS module indicators and factors – structural–technical part.

TEA Water application

From the very beginning, the TEA Water software tool was conceived of as a web application implementing the presented methodology of preliminary assessment of the technical condition of water infrastructure. It is a project-oriented application, enabling each system to be evaluated as a separate project. The project may be the entire water supply system or a single structure, or even a group of structures from various water supply systems. Project users may have various levels of authorisation, from the ability to carry out assessments, including adjusting the weights, to merely viewing the results of the project.

The web application makes it possible to attach documents such as images, descriptions and other files (doc, pdf, jpg) to assess individual factors. Figure 4 shows the initial screen of the selected project, with an overview of its individual modules. As part of the presented project, the following objects were assessed: five water resources, five pumping stations and two pressure zones. The results achieved by this assessment can be sorted and filtered into required printouts, as needed. The TEA Water software tool is described in detail in Tuhovčák et al. (2016).

Figure 4

Modules in the TEA Water application.

Figure 4

Modules in the TEA Water application.

RESULTS AND DISCUSSION

As part of the verification of the presented methodology, all the modules were tested in real and modelled WSSs. This paper presents case-studies with implementation of TEAP and TEAS modules in real WSSs.

TEAP

Within the TEAP module, the assessment of the technical condition of a booster pumping station was presented for a higher-elevated group water supply system. This means the pumping station does not have its own storage tank. The pumping station has two horizontal centrifugal pumps, which are operated evenly. The pumped volume is 105 l.s−1, while the yearly delivery is 551,880 m3. The output pressure at the delivery pipe at the outlet from the pumping station is at 135 mH2O. The total installed power is 225 kW.

The pumping station was built in 1986 and reconstructed in 2012. As shown in Figure 5, the overall assessment is A and the total percentage of degradation is set in the interval of 6–15%. The final assessment of the technical condition of the pumping station shows adequate reconstruction. The last column shows the weights set for the individual parts as well as their indicators in the assessment system.

Figure 5

Final assessment – TEAP module.

Figure 5

Final assessment – TEAP module.

TEAS

An assessment of water mains located in a pressure zone supplied from a water reservoir located upstream of the service area was carried out as part of the TEAS module testing. It is therefore a gravity water main. The assessed water main leads directly from the water reservoir and supplies other service areas. In the event of a serious defect in this main it must be disconnected, which results in water supply interruption to other related pressure zones as well. It is man-made of grey cast iron, DN 400, with a length of 854 m. It was built in 1979 and connects 68 water service pipes.

An important indication is also the maximum hydrostatic pressure of 53 mH2O and an average hydrostatic pressure across the entire main of 35 mH2O. The final assessment of the main and the monitored indicators in the TEA Water application are presented in Figure 6.

Figure 6

Final assessment – TEAS module.

Figure 6

Final assessment – TEAS module.

CONCLUSIONS

The methodology submitted presents the results of the efforts to develop a simple but efficient method for preliminary assessment of the technical condition of water supply infrastructures. Individual modules are used for the assessment and semi-quantitative categorisation of the technical condition of the specific components and objects of the water supply systems. The outputs of this methodology can also serve as the basis for comparative analyses, repairs planning, renewal planning and development of renewal financial plans as well as the basis for further detailed structural–technological surveys, etc.

The proposed methodology can interpret the technical condition of the relevant infrastructure, reveal potential hot-spots and rank the operated objects described above as per their defined technical condition categories for various objects of water supply infrastructure. The advantage of the proposed methodology developed into the TEA Water software tool is its ability to perform continuous and sufficiently precise assessments of the technical condition of the infrastructure, as well as to identify the problematic parts to which more attention must be paid. The software tool is developed as a web application, enabling remote access and information-sharing amongst projects defined by users.

ACKNOWLEDGEMENTS

The article paper was drawn up within project No. LO1408 ‘AdMaS UP – Advanced Building Materials, Structures and Technologies’ supported by the Ministry of Education, Youth and Sports as part of the targeted support programme ‘National Programme for Sustainability I’ and under Project No. FAST-S-17-4643 supported by Brno University of Technology.

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