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Modular Sustainable Sewage Treatment Plant The New Standard

is a joint venture between the Peel en Maasvallei water authority and the Roer en Overmaas water authority

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© 2012 WBL

All rights reserved

Nothing of this publication may be reproduced, stored in an automated database or published, in any way shape or form, either electronically, mechanically, by photocopying, recordings or any other method, without the prior written consent of the publisher.

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Colophon

Title


Date

26 April 2012

Project owner

Ing. E.M. Pelzer MMO (director)

Client

Waterschapsbedrijf Limburg

Steering group

Ing. E.M. Pelzer MMO Ing. O.L.C. Durlinger Ing. A.L.J. Houtappels Ing. H.A.M. Speetjens MBI

Project team

Ing. O.L.C. Durlinger (project leader) Ing. J.J.G.A. Belleflamme Ir. R.H.J.M. Crousen Ing. J.P. M. Janssen Ir. A.W.A. de Man Ing. W. F. Verkuijlen Ing. A.P.M. Vonken

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Table of contents 1. Management summary 8

2. Introduction 12

2.1 Motive and background 12 2.2 Evolution of sewage treatment in the Netherlands 13

3. Conventional sewage treatment plant 15

4. Modular Sustainable Sewage Treatment Plant 17 4.1 Introduction

17 4.2 Description and technical design 17 4.3 Modular Sustainable Sewage Treatment Plant versus conventional plants 19

4.3.1 Lower net annual costs 20 4.3.2 Management and maintenance

22 4.3.3 High degree of flexibility 22 4.3.4 High degree of sustainability 23 4.3.5 Short design and construction times

24 4.3.6 Work experience 25 4.3.7 Conclusions 26

5. Business Case 27

5.1 Introduction 27 5.2 Description of versions 28 5.3 Financial comparison 30 5.4 Sustainability comparison 33 5.5 Conclusions business case 34

6. Conclusions 35

Glossary

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Appendix Appendix 1. Technological process choice Appendix 2. Characteristics of principal treatment technologies Appendix 3. Technological design Appendix 4. Process diagrams (Ulbas-UCT, Nereda) Appendix 5. Financial comparison for cost diagram Appendix 6. Comparison of construction time Appendix 7. Management and maintenance Appendix 8. External developments Appendix 9. Example of flexibility of MSSTP in the case of external developments Appendix 10. Sustainability comparison business case Appendix 11. Overview dimensions versions business case Appendix 12. Financial substantiation business case

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1. Management Summary

External factors have forced water authorities and water authority executives to take measures that:

- reduce net annual costs; - increase sustainability of activities; - Improve the quality of treated water at low costs.

In the Administrative Agreement on Water Affairs (April 2011), the Climate Agreement (2010) and the long-term agreement on energy efficiency, the water authorities have made specific agreements about sustainability and reducing costs. The implementation of the Water Framework Directive influences the quality of treated water and the costs involved. In addition to external stimuli to make changes, Waterschapsbedrijf Limburg ("WBL") has the intrinsic motivation of a high-performance organisation that wants to distinguish the company's future position in terms of relevant financial and non-financial results. The internal and external impulses have prompted Waterschapsbedrijf Limburg to develop an innovative way of designing and constructing water treatment plants, enabling customised treatment. This report demonstrates that this new method ensures the company will be able to face the above challenges and build up a strong competitive position1. The product of this new design and construction method is called the Modular Sustainable Sewage Treatment Plant (MSSTP). The strength of this innovation lies in the modular design and construction philosophy. In contrast with traditional sewage treatment plants, the modular character of the MSSTP makes it possible to modify communal and industrial wastewater treatment plants in a flexible, inexpensive and sustainable manner in accordance with changing environmental factors and to anticipate innovations fast. The 1st generation MSSTP, the one discussed in this report, lays the foundations for future modular systems. The MSSTP philosophy should be regarded as a growth process with ample opportunities. In order to confirm the potential of the MSSTP concept, and to reduce the risk, we only use proven technologies for the 1st generation MSSTP. The innovative character of the MSSTP mainly manifests itself in the design and construction of the supply2 and treatment3 phases of a plant. This is why we will discuss both steps in great detail, considering the financial analysis. The options for the follow-up process4 are given, but they will not be included in the financial deliberations. For the water treatment process specifically, this means that the financial analysis was made from the point where influent is taken in, up to effluent. The sludge line is limited to the disposal of thickened sludge. Developments such as effluent recycling, the generation of energy through fermentation, recovering raw materials and the final processing of sludge affect (operational) sustainability, but they do not form part of the financial scope of this study. We feel it will be useful to take such expansions of the MSSTP into account only when it has been proven that the basic model yields insufficient gain.

1 A patent application has been submitted for the innovative design and construction method. 2 The supply step (the initial section) comprises any booster systems, grids/filters and sand collection. 3 The treatment step (the central section) comprises the biological treatment processes and a rainwater buffer. 4 The follow-‐up process (the post-‐section) is intended for subsequent treatment of the effluent.

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To analyse the advantages of the MSSTP, we opted for the comparative method. First, we compared the 1st generation MSSTP with an existing, conventional sewage treatment plant. In this comparison, we did not use the inherent qualities of the MSSTP, such as the flexibility to adjust capacity, waste load, and technology. We did set off the advantages of the MSSTP in terms of maintenance, deployment of personnel and energy consumption. We stress that this comparison is based on the least favourable scenario for the MSSTP. In specific terms, it means we assumed a scenario in which the MSSTP, like a conventional sewage treatment plant, is maintained in the same location, with the same capacity, waste load and layout for a period of 30 years. The results of this comparison are astounding. Despite not using the flexibility in the calculated scenario and regardless of scale, the implementation of the MSSTP results in a significant reduction of the net annual costs compared to a conventional sewage treatment plant of the same size. Depending on the technology used and capacity, savings of net average annual costs lie between 10 and 20% compared to a conventional water treatment plant. In addition to the cost advantage, this analysis shows that the MSSTP scores considerably better than a conventional water treatment plant in terms of:

- sustainability; - design and construction times, innovativeness; - flexibility; - Work experience.

The sustainability comparison demonstrates that, for the total energy demand of a treatment plant during its life, daily energy consumption is so much more important than the energy consumption required for materials to construct the treatment plant. Modular treatment plants come out better in the analysis on the basis of lower material use and, depending on the treatment technology applied, less daily energy consumption than conventional sewage treatment plants. The strong construction (large concrete tanks)) and long preparation and realisation periods of conventional water treatment plants5 make it virtually impossible to anticipate new technologies. As a result, the sector fails to offer sufficient innovative challenges for the supplying companies. Like the highly conservative aviation industry, it takes an average 10 to 15 years before innovations in the wastewater industry are widely implemented6. The modular character of the MSSTP7 opens up possibilities to properly anticipate new technological developments. This will considerably lower the time-to-market of innovations, while the innovativeness of suppliers and the sector as a whole will increase. Based on the evolution in other industries, we can conclude that an increase of innovativeness of the industry will lead to continued improvements in terms of performance and a reduction of costs. In contrast with a conventional sewage treatment plant, the modular character of the MSSTP offers unique opportunities to flexibly and inexpensively anticipate relevant developments, such as the

5 For conventional constructions, an average completion time of 2 to 3 years must be taken into account. 6 Interview with TNO. 7 The design and construction method of the MSSTP requires an average completion time of 6 months to 1 year. This is a reduction of 60% compared to conventional construction methods.

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tightening of effluent standards, changes to supply, the use of residual heat and the treatment of overflow water. Finally, the MSSTP is an inspiring innovative process with interdisciplinary challenges, encouraging pioneering ideas and actions. The innovative character and long-term potential result in a working environment where people are encouraged to give it their all and where intrinsic rather than extrinsic motivation is an important incentive to perform well. In addition to this general comparison between a conventional water treatment plant and the MSSTP, we also made a detailed comparison of net annual costs and sustainability for seven types of water treatment plants with a capacity of 60,000 PE (population equivalents) (150 g of total oxygen demand). This comparison takes into account differences in construction time, flexibility gains and different effluent levels. The analysis is based on a comparison between a conventional plant with an active sludge process with pre-sedimentation and pre-precipitation, inspired by an existing plant of WBL, and MSSTP versions that use Ulbas-UCT and Nereda technology. The financial analyses show a highly favourable result for all MSSTP versions compared to a conventional sewage treatment plant. Depending on effluent quality, the Nereda MSSTP versions show 17 to 24% lower net annual costs8 than the conventional versions. For the MSSTP that uses Ulbas-UCT technology, that figure is 15 to 22%. Versions of the Nereda MSSTP score slightly better in terms of net annual costs than versions of the Ulbas-UCT MSSTP. On a scale of 60,000 PE, making a comparison between a new conventional treatment plant and a new Nerada MSSTP, the annual advantage in terms of net costs is approximately EUR 500,000. Widely extrapolated in Limburg, this would yield an average annual advantage of approximately EUR 15,000,000. Another important fact is that the Nereda MSSTP versions score better in terms of sustainability than versions of the Ulbas-UCT MSSTP. The Nereda MSSTP versions score better in terms of sustainability, using fewer materials but specifically consuming less energy on a daily basis compared to all other versions. Sustainability is not a principle that can be ignored in today's social context, especially since the water authorities have ambitions in areas such as climate change, having confirmed this in the Climate Agreement. Based on our analyses9, we can justifiably conclude on a sectoral level that conventional sewage treatment plants are surpassed by this modular innovation. The modular sustainable sewage treatment concept performs better on certain characteristics and is less expensive than conventional systems. We think the MSSTP is the new standard for our sector. A standard that has global potential, thanks to its flexible and all-round deployability on a small and large scale. In terms of follow-up steps, we recommend Waterschapsbedrijf Limburg to make a detailed analysis of potential partners for the development and construction of the concept. Taking the results of the patent application into account, WBL should also start thinking about how it can play the most effective role in the commercialisation process. The specifics of this role, the organisational and administrative form of this activity will form the subject of a follow-up study. However, we feel the MSSTP has such potential that this analysis should not preclude a separate activity.

8 Net annual costs are taken to mean the average net annual costs over a 30-‐year period. 9 The analyses and calculations that form the basis of this report go deeper than we can explain within the context of this report.

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Concluding, the table below offers a comparison between conventional sewage treatment plants and the MSSTP. This comparison was made independently of the treatment technology used in order to be able to demonstrate the MSSTP philosophy independently of the effect of the technology.

Table - comparative overview Characteristics Conventional sewage

treatment plant MSSTP

Costs o ++ Sustainability o o/+ General innovativeness o ++ Flexibility regarding

- Tightening of effluent standards - Supply of different types of water - Changes to supply - The use of residual heat - The treatment of overflow water - Technological developments

o

o/+ + - -

o/+ -

++

+ + + + + +

Design and construction times - ++ Management and maintenance

- Reliability - Availability - Maintainability - Safety - Costs

+ o o + o

+ +

++ + +

Work experience - Interdisciplinary cooperation as a team - Using and stretching knowledge and talent - Stimulating the intrinsic motivation

o o o

+

++ ++

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2. Introduction

External factors have forced water authorities and water authority executives to consider alternative methods and technologies. Based on the intrinsic motivation of a high performance organisation, Waterschapsbedrijf Limburg ("WBL") has developed an innovative design and construction technology for sewage treatment plants, the so-called Modular Sustainable Sewage Treatment Plant ("MSSTP"). This philosophy is characterised by a modular design and construction technology for wastewater treatment plants, enabling customised treatment. The analyses conducted within the context of this report show that a new concept offers a solution for the many challenges in the water authority industry, allowing for a strong competitive position. This introduction will first briefly discuss the evolution of the wider economic and social context, indicating how this led to innovation in various sectors and, as a derivative, to modular innovation forms. We will then discuss the specific context of, and the developments relevant for the water authorities and water authority executives. The conclusion is that the industry is facing challenges in terms of costs, sustainability and the quality of treated water. For those who are not familiar with the water authority subject matter, chapter 3 offers a brief explanation of a traditional sewage treatment plant and its main characteristics. Chapter 4 explains the Modular Sustainable Sewage Treatment Plant in great detail. In the same chapter, we also make a comparison between a representative conventional plant and the MSSTP. We will demonstrate that the MSSTP distinguishes itself from a conventional sewage treatment plant in the following areas: lower net annual costs, a higher degree of flexibility in terms of various external developments and innovation, sustainability, shorter design and construction times and an inspiring work experience. Chapter 5 offers a further substantiation for the advantages in terms of costs and sustainability of the MSSTP on the basis of a comparative analysis between a number of versions of the conventional water treatment plant and MSSTP versions. It demonstrates that MSSTP versions score significantly better than traditional water treatment plants. The Nereda MSSTP in particular is the most sustainable version. Chapter 6 of this report gives a summary of the main findings of the report. 2.1 Motive and background The gravity of various social challenges, combined with an increase in competition leads to more pressure on organisations, regardless of industry, to act innovatively, fast and flexibly. The fast pace of innovation and opportunities that arise as a result prompts many companies in a direction of initiatives that considerably differ from the way in which these companies used to work. Industries characterised by mature technologies and products and services are experiencing an evolution towards decentralisation on the basis of disruptive technological and business model innovations. In these mature industries specialisation and strategic collaboration take over from vertical integration, resulting in a continued increase of innovative strength in combination with lower costs. Some industries, such as the energy and healthcare industries, are experiencing a trend for

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local production and consumption, enhancing the development and implementation of platform and modular innovation. A similar evolution is being detected in the wastewater industry. In past years, interest for innovative water treatment technologies saw a rise in general and in the Netherlands. Sneek for instance, saw a world first in 2010 when a new water treatment system was introduced. Since late 2010, wastewater from the Noorderhoek district is collected separately and treated at a small treatment plant in a district that has 232 dwellings. The new water treatment system generates energy from wastewater, it removes medicine residuals and recovers fertilizers for recycling. On the basis of this experiment, the partners are looking for a balance between efficiency and affordability on the one hand and working on innovation and sustainability on the other10. Sneek is a local concept that cannot be deployed in all circumstances. However, it symbolises the many examples of how water authorities innovatively anticipate a new context. 2.2 Evolution of sewage treatment in the Netherlands It would be impossible to fathom the evolution in the Dutch water treatment industry without having an understanding of a number of important trends that influence the industry. On the basis of these trends and developments, the Foundation for Applied Water Research (Stowa)11 identified influencing factors. This established that - in addition to the primary objectives of protecting public health, surface water quality and the environment - the factors of costs, energy neutrality, effluent quality12, and nutrient recovery are the main additional influencing factors for future sewage treatment plants. A lot of influence is exerted by the political policy, which emphasises quality improvement of management of the water system and water chain at the lowest possible costs to society. The Administrative Agreement on Water Affairs (April 2011, p. 27) states:

"Water chain efficiency is open to improvement, which can be realised by continuing to professionalise management and by bundling knowledge and capacity. A regional approach, more focus on knowledge and innovation and an improvement of the actual working processes are focal points in that respect. More cost-effective investment decisions and a more systematic and more efficient implementation of operational duties should lead to results."

The water treatment industry is the centre of the social and economic debate about climate change and sustainability. Stowa formulates this as follows:

"During the next few decades, anticipating climate change and increasing sustainability will play a leading role in the continued development of the (waste) water chain."

The Water Framework Directive ("KRW") influences the quality of effluent. This means that the requirements with regard to phosphor and nitrogen will be tightened further and that standards will be

10 Source: http://www.duurzaamnieuws.nl/bericht.rxml?id=57329 11 Stowa, April 2010, "Op weg naar de RWZI 2030" p. 5 12 Effluent is a term used for treated wastewater. Effluent usually still contains some of the original contamination and is not suitable as drinking water.

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attached to other substances (such as priority substances and medicine residuals). This is also the case if the aim is to reuse effluent as cooling water, farm water or as a source for demineralised water or even drinking water. The Association of Regional Water Authorities and the government have set out their plans with regard to climate change in a Climate Agreement (2010) and a long-term agreement on energy efficiency. Summarising, they are13:

• 30% energy - working more efficiently and more economically between 2005 and 2020; • 40% self-reliance thanks to in-house sustainable energy production in 2020; • 30% less emissions of greenhouse gases between 1990 and 2020; • 100% sustainable procurement in 2015.

An action programme has been prepared for the implementation of the climate agreement. By applying innovative technologies, the water authorities now use energy efficiently. By increasing the production of biogas from wastewater, the water authorities become more and more self-reliant. In time, treatment plants will be able to supply energy to third parties. Water authorities are looking for alternative sustainable energy sources such as wind energy, solar energy and hydropower. They are also engaged in sustainable procurement and tendering. Where relevant, the influencing factors in the comparative analysis below between conventional sewerage treatment plants and the MSSTP will be taken into account.

13 http://www.uvw.nl/beleidsveld-‐klimaatakkoord.html

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3. Conventional sewerage treatment plant

In order to have a better understanding of the new concept of Modular Sustainable Sewage Treatment Plants (MSSTP), this chapter first briefly explains how sewage treatment plants work. We will then discuss the characteristics of the traditional construction method. In a sewage treatment plant, wastewater from sewers is treated before it reaches the surface water. The incoming polluted water, the influent, is treated in the plant in a number of different stages. The treated water is referred to as effluent. The coarser particles are separated with a grid or separator, followed by the finer particles (in sediment tanks) and finally the dissolved substances. The treatment process releases "treatment sludge", a residual product, which needs to be disposed of. Figure 1 represents a diagram of a conventional sewage treatment plant, based on an existing plant of Waterschapsbedrijf Limburg, which applies pre-sedimentation and pre-precipitation. Pre-precipitation is a dosing of iron salts in order to remove phosphates. Figure 1. General design of a conventional sewage treatment plant

AeratietankVuilrooster

Vijzel

EffluentInfluent

Voorbezinktank

Nabezinktank

Regenwaterbuffer

Influent - mortar - dirt grid - rainwater buffer - pre-sedimentation tank - aeration tank - post-sedimentation tank - effluent

There are several technologies to treat the mixed communal and industrial wastewater supplied to the WBL sewage treatment plants. A literature study and interviews with respected researchers14 has demonstrated that Ulbas-UCT, Nereda and MBR are currently the main proven technologies (more information can be found in appendix 1). Ulbas-UCT (a University of Cape Town process) is an ultra low-burden active sludge process. Nereda is an active pellet sludge system and MBR is a membrane bioreactor. The three technologies are characterised by organic de-phosphatising and the removal of nitrogen. When these technologies are applied, wastewater is treated directly, without pre-sedimentation. The main characteristics of these technologies are explained in appendix 2. In this report, we discuss two of these three technologies, namely: Ulbas-UCT and Nereda. MBR is not discussed in detail in this report. The use of this technology is useful only under circumstances

14 The accuracy of this restriction is confirmed by Professor Jules van Lier, professor “Environmental Engineering / Wastewater Treatment” at Delft University of Technology, Faculty of Civil Engineering and Geosciences, Department of Water Management, Section Sanitary Engineering, and Dr. Sarah Slaughter President and Executive Director, Built Environment Coalition, MIT, USA.

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with very high effluent requirements. Furthermore, it is not an attractive technology in terms of costs (see paragraph 4.3.1). Conventional construction or the current construction method for sewage treatment plants is characterised by:

-‐ A high degree of capital intensity and restrictions in terms of locality; -‐ Long design and construction times; -‐ Robust construction methods, often comprising part-underground concrete structures and

underground pipework; -‐ Maintenance is time-consuming and has to be carried out in far from attractive working

conditions;

-‐ Inflexibility with regard to external change: technological developments, changes to supply, amended legislation and the supply of other types of water; Changes to the conventional concept are very expensive and lead to less than perfect solutions;

-‐ A high claim on space. The characteristics of the conventional systems against the background of a changed context which, as explained in paragraph 2.2, is typified by a pressure on costs, new effluent requirements within the framework of the KRW, and the importance of sustainability declare a wide interest in innovation and more flexible forms of sewage treatment systems.

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4. Modular Sustainable Sewage Treatment Plant 4.1 Introduction This chapter introduces the 1st generation Modular Sustainable Sewage Treatment Plant (MSSTP). The strength of this innovation lies in the modular design and construction philosophy. We will then, on the basis of a comparison with the conventional design and construction method, explain the potential of this modular innovation.

In the financial comparison, we did not take into account the unique character of the MSSTP, such as the flexibility to adjust capacity, waste load, and technology. It is obvious that when the MSSTP performs well in this less favourable scenario (for the MSSTP), the benefits in a full financial analysis can only get better. The 1st generation MSSTP forms the basis for future generations. In order to confirm the potential of the MSSTP concept, and to reduce the risk, we use proven technologies for the 1st generation MSSTP, namely Ulbas-UCT and Nerada. The innovative character of the MSSTP mainly manifests itself in the design and construction of the supply phase (the initial section) and treatment phase (the central section) of a plant. This is why we will discuss both steps in great detail, considering the financial analysis. The options for the follow-up process (the post-section), intended for the post-treatment of effluent, are given, but they will not be included in the financial deliberations. For the water treatment process specifically, this means that the financial analysis was made from the point where influent is taken in, up to effluent. The sludge line is limited to the disposal of thickened sludge. Developments such as effluent recycling, the generation of energy through fermentation, recovering raw materials and the final processing of sludge affect (operational) sustainability, but they do not form part of the financial scope of this study. It is useful to take such expansions of the MSSTP into account only when it has been proven that the basic model yields insufficient gain. 4.2 Description and technical design The design of the MSSTP is subdivided into three large sections: the initial section, the central section and the post-section.

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The initial section comprises the following elements: booster systems, grids and sand collection This section is characterised by:

• A succession of modules, linked to a single drain; • Transportable modules; • Plug and Play modules; • Aboveground setup.

The central section comprises the organic treatment section and buffer basin. This design is characterised by15:

• A flexible relationship between organic and mechanical treatment; • Ulbas-UCT, Nereda and MBR technologies; • Multiuse tanks; • Flexible tank size; • The option to apply multiple technologies in a single MDR; • A flexibly organised buffer basin (processing of first flush); • Aboveground setup.

The post-section comprises elements with end-of-pipe technologies.

• A succession of modules for the supply of different types of water, linked to a single drain; • Transportable modules; • Plug and Play modules; • Aboveground setup.

The specific characteristics of the initial and central sections16, where the innovativeness of the MSSTP manifests itself, are: Characteristics of the supply phase of the MSSTP:

-‐ A central drain distributes the sewage stream across machines and equipment; -‐ The central drain has a capacity of 10,000 to 100,000 PE. Depending on the machines

installed, approximately 8 hydraulic connections (machines/equipment) can be realised; -‐ The machines and equipment are installed on branches of the central drain. This means these

machines can be moved and replaced easily and quickly, referred to as Plug and Play. The branches can be temporarily shut off quite simply;

-‐ The central drain comprises grid sections with a fixed length and shape; -‐ Connections to the drain have the same dimensions;

-‐ The machines and equipment are similar to those for conventional sewage treatment plants. No special modifications to machines are required for the MSSTP.

The specific characteristics of the treatment phase of the MSSTP are:

15 The basic principle is part organic and part mechanical treatment. 16 See also appendix 3 for more details.

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-‐ High-volume tanks are needed for the treatment processes. Every tank module is subject to a single functional process step;

-‐ The modification options of the separate tanks are larger than the fixed dimensions of the tank with compartments. Separate tanks can be made of sustainable materials, as the dimensions of these tanks are smaller than those of combined tanks.

-‐ The tanks can be of a modular build thanks to the use of segments. Various materials such as concrete, steel, stainless steel, wood, etc. can be used for the segments. This is further discussed in 4.3.4 with regard to sustainability; The tank segments have a long life (more than 40 years) and can be reused to construct tanks at different locations or for tanks with different dimensions in the same location;

-‐ At the Ulbas-UCT MSSTP (see Figure 1, Appendix 4), flexibility is realised by allowing the various technological processes to take place in separate tanks, whereas they are normally combined in a single tank with multiple zones or compartments. The process steps are: anaerobic tank for organic de-phosphatising, selector to control sludge sedimentation properties, denitrification tank and two nitrification tanks for the removal of nitrogen. This results in a separation of hydraulics (capacity in m3/h) and waste load (contamination units in PE). There are also options to shortcut or bridge the various technological processes, making it easier to carry out maintenance;

-‐ At the Ulbas-UCT MSSTP (see Figure 2, Appendix 4), flexibility is realised by installing an interim buffer, creating another disconnection of hydraulics and waste load. Two Nereda tanks are sufficient. The Nereda operates in batches: supply and draining, aerating and sedimentation. The processes of organic de-phosphatising and nitrogen removal take place in a single tank. Basically, Nereda comprises 2 or more parallel connected tanks that are alternately supplied by the buffer. The Nereda technology is a recently developed aerobic pellet sludge technology, which is applied in Epe at a scale of approximately 60,000 PE. The space needed for the Nereda MSSTP is approximately 50% compared to a conventional Ulbas-UCT.

-‐ The MSSTP version with an MBR process comprises various compartments where different processes take place: organic de-phosphatising and nitrogen removal. Sludge water is separated by means of membranes. This version is not elaborated, as the MBR is considerably more expensive than the other two versions (see 4.3.1).

4.3 Modular Sustainable Sewage Treatment Plant versus conventional plants The 1st generation MSSTP offers a comprehensive approach, in the course of which various stages of the life of a plant (design, execution, use and disassembly) are integrated and combined in the best possible design. In accordance with this best possible design, the MSSTP distinguishes itself from conventional plants in the following areas17: 4.3.1 Lower net annual costs for the plant's period of use; 4.3.2 Management and maintenance; 4.3.3 High degree of flexibility; 17 In accordance with the QWENC principle (Quality, Work Experience, Net Costs)

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4.3.4 High degree of sustainability; 4.3.5 Shorter design and construction times; 4.3.6 Work experience 4.3.7 Conclusions

4.3.1 Lower net annual costs In this paragraph we will compare three MSSTP versions, the Ulbas-UCT treatment technology MSSTP, the Nereda treatment technology MSSTP and the MBR treatment technology MSSTP, with the reference, being a conventional sewage treatment plant with Ulbas-UCT treatment technology. For the reference we opted for the Ulbas-UCT technology as it is a popular active sludge process at a scale of 10,000 to a number of 100,000 PE and it is characterised as a robust technology that leads to low effluent N and P levels. The table below shows the various basic principles. Table - basic principles of financial comparison

Costs Basic principles

Investments with a 30-year technical life In EUR, calculated per version

Investments with a 15-year technical life In EUR, calculated per version

Estimate accuracy approximately 10%

Repayment interest 4.75%

Inflation 2%

Deployment of personnel EUR 54,000 per FTE

EUR 1.60 per PE, subject to a lower limit of EUR 54,000

Energy consumption EUR 0.092 per kWh

Consumption in kWh determined per version

Consumption of chemicals due to sludge thickening Polymer EUR 2.56 per kilo

Maintenance for a 30-year technical life 0.8% of the construction costs

Maintenance for a 15-year technical life 3% of the construction costs

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For the financial comparison, the costs for the different versions are reconverted into net annual costs in EUR/PE. The calculations for the financial comparison were made for a scenario in which the MSSTP versions (Ulbas-UCT, Nereda and MRB) are seen as green sewage treatment plants that continue to exist in the same location for a period of 30 years, with the same capacity (m3/h) and waste load (PE). For the sake of the comparative analysis, the flexibility of the MSSTP with regard to adjustment of capacity, waste load and technology is not included in the calculations. We did set off the advantages of the MSSTP in terms of maintenance, deployment of personnel and energy consumption. The specifications of these setoffs are explained in chapter 5 and the relevant appendices. The MSSTP concept has lower maintenance costs thanks to standardisation, localisation, less corrective and breakdown maintenance and lower staffing levels. The MSSTP-related maintenance philosophy is characterised by speed and permanent availability of the plants. The modular construction makes it possible to quickly disconnect and replace individual modules during maintenance. Maintenance can be carried out in the appropriate indoor facilities, professionalising this activity and thus making it labour-friendly. The following variables apply to the financial comparison:

-‐ Depreciation period for a 30-year technical life: 30 years -‐ Depreciation period for a 15-year technical life: 15 years -‐ Calculation period: 30 years

The cost diagram of 10,000 to 100,000 PE looks like this: Figure 2. Average net annual costs per PE (treatment and sludge thickening)

AVERAGE TOTAL ANNUAL COSTS N=10 and P=1 / Costs in EUR/PE / Conventional UCT / Load in PE

€ 20,00

€ 40,00

€ 60,00

€ 80,00

€ 100,00

€ 120,00

€ 140,00

€ 160,00

-‐

10.00

0

20.00

0

30.00

0

40.00

0

50.00

0

60.00

0

70.00

0

80.00

0

90.00

0

100

.000

Kos

ten

in €

/ie

Belasting in ie

GEMIDDELDE TOTALE JAARLIJKSE KOSTEN N=10 en P=1

MDR Nereda

MDR UCT

Convengoneel UCT

MDR MBR

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Despite not using the flexibility in the calculated scenario and regardless of capacity, the figure shows that the MSSTP results in a significant reduction of the net annual costs compared to a conventional sewage treatment plant of the same size18. Depending on the technology used (Ulbas-UCT or Nereda) and capacity, savings of net average annual costs lie between 10 and 20%.

18 This result is further substantiated on the basis of the business case, explained in detail in chapter 5.

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4.3.2. Management and maintenance

For maximum management and maintenance of the plant during the use phase, the following characteristics have been mapped out: the degree of reliability, availability, maintainability and safety. When we assess these four characteristics, we speak of a RAMS analysis.

The objective of a RAMS analysis The information from the analyses of these four characteristics can be translated into RAMS requirements. They express the performances we should expect from a plant. RAMS can also be used to control risks in terms of performance, to compare performance alternatives or to locate weak spots in the design of a system.

Results of the RAMS analysis and the costs of management and maintenance The RAMS analysis was conducted for the conventional Ulbas-UCT, the Ulbas-UCT MSSTP and the Nereda MSSTP19. The summary of results of this analysis for a plant of 60,000 PE is shown in the table below. More information about the details and explanation of the RAMS analysis can be found in appendix 7. Table - results of RAMS analysis

Versions Reliability Availability Maintainability Safety Costs 1. Conventional Ulbas-UCT + o o + o 4a. Nereda MSSTP + + ++ + + 4c Ulbas-UCT MSSTP + + ++ + + The RAMS analysis shows that both MSSTP concepts score better on Availability and Maintainability compared to a conventional Ulbas-UCT. The Nereda MSSTP scores slightly lower on Reliability, as this concept has two critical steps (a fine filter and a Nereda pump phase). A high level of safety for man, the environment and plant is pursued at all times, also with the existing, conventional Ulbas-UCT plant. This also explains why all three concepts score the same in that respect.

Application of the Plug and Play principle and a central workshop with maximum stock control of spare parts is translated into an estimated cost reduction of 20% of the maintenance budget for plant parts with a 15-year technical life and an estimated 10% cost reduction of personnel20. 4.3.3. High degree of flexibility

The MSSTP concept has been tested for flexibility with regard to a number of developments such as tightening of effluent standards, the supply of different types of water, changes to supply, the use of residual heat, technological developments and the treatment of overflow water. The table below gives a summary. External developments are discussed in more detail in appendix 8. Appendix 9 describes the examples, which the MSSTP concept and conventional treatment plant can anticipate. 19 Appendix 7 substantiates the coherence and method of RAMS. RAMS as a full part of Asset Management, Systems Engineering and Life Cycle Cost was discussed with Professor T.M.E. Zaal, Emeritus Associate Professor, Utrecht University of Applied Sciences, Faculty for Nature and Technology. 20 Appendix 5 provides a detailed substantiation of the maintenance costs and staff deployment with regard to maintenance and operation.

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Table - overview of assessment of flexibility of the MSSTP and conventional treatment plant

MSSTP Conventional treatment plant

Tightening of effluent standards

+ o/+

Supply of different types of water

+ +

Changes to supply + -

The use of residual heat + -

The treatment of overflow water

+ o/+

Technological developments + -

In terms of flexibility, the MSSTP scores higher than a conventional treatment plant with regard to tightening of effluent standards, changes to supply, the use of residual heat, the treatment of overflow water and technological developments. 4.3.4 High degree of sustainability

A sustainability comparison21 shows that the Nereda MSSTP versions score better than a conventional treatment plant. The sustainability of the MSSTP versions was compared to that of a conventional treatment plant. In this comparison, the required energy was stipulated for:

• The production of the materials used • The construction of the sewage treatment plant

• The running of the treatment plant: energy and chemicals • Pulling down the treatment plant.

The total energy consumption for the owner throughout the period of use is expressed as the Total Energy use of Ownership (TEO). The application of the tried and tested TEO methodology is based on assessing the total energy consumption on the basis of GER values. GER (Gross Energy Requirement) is a measure for the gross energy content of a substance, expressed in primary energy.

TEO comprises the energy for the material of the plant, the energy needed to construct the plant, the energy needed for the day-to-day running of the plant and the energy required to pull down the plant at the end of its life22.

21 See RIONED Foundation, 2012, "Water en energie. Feiten over energieverbruik in het stedelijk waterbeheer.” See also Dr. Jeroen Kluck, “Total Energy of Ownership voor rwzi,”2012. A study by Dr. Kluck, an expert on urban water and sewage and a lecturer at the Amsterdam University of Applied Sciences, at the request of WBL. Relevant parts of this study are included in appendix 10.

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The sustainability comparison demonstrates that, for the total energy consumption of a treatment plant during its life, daily energy and chemical consumption is so much more important than the energy consumption required for the construction method and materials to realise the treatment plant. From a sustainability point of view it is therefore necessary, when designing a plant, to pursue a low energy and chemical consumption.

The modular treatment plants that operate on the basis of the Nereda process (versions 4a and 4b in chapter 5) come out favourable from the analysis on the basis of less material use, but mainly because of a lower daily energy consumption than conventional sewage treatment plants. Chapter 5 provides specific details about this subject on the basis of a comparison between different versions of a treatment plant of 60,000 PE.

A study was conducted into the use of different materials for the construction of the plant. The final material selection forms part of the follow-up study.

4.3.5 Short design and construction times

So as to be able to anticipate new development fast and efficiently, it is important to know how fast a sewage treatment plant can be realised. Long preparation and realisation times will hamper the ability to adequately anticipate new developments.

The design and construction times of the MSSTP are significantly shorter than those for the current conventional plants. For conventional constructions, an average completion time of 2 to 3 years must be taken into account23. The design and construction method of the MSSTP requires an average completion time of 6 months to 1 year, a reduction of approximately 60%.

The general characteristics of the MSSTP are:

- In contrast with the conventional method, 90% of the MSSTP is constructed aboveground. It means the construction phase is less dependent on weather conditions such as frost. During the use phase, the systems are easier to modify thanks to better access.

- Modules are designed in such a way that they can be transported by road. - Modules are produced in series. Within the module, the process is reduced to a single

functional step. The aim is to standardise modules. The number of modules for one functional step is kept low. Example: 3 types of machines to remove pollution, suitable for a range between 10,000 and 100,000 PE.

- Prefabrication prevents errors, and if they do occur they can be resolved by the supplier or manufacturer. Quality is high. Tested and prefabricated plants reduce errors to a minimum;

- Every module is fitted with its own uniform controls, and the modules are linked by a network. - The use of modules facilitate simplicity and standardisation in maintenance and operation;

22 This concept is a clear simplification of a life cycle analysis (LCA), which includes all sorts of sustainability aspects on a wider scale. The restriction results in an understandable methodology that includes a number of important sustainability aspects: recycling materials and energy use. 23 Appendix 6 provides a detailed overview of the completion times of a conventional Ulbas-‐UCT versus the Nereda MSSTP for 60,000 IU.

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- Modular construction offers scope for specific customer requirements. Flexibility makes it possible to integrate customer requirements in the short term;

- Future technologies and equipment can be geared to the modules. On the basis of the aforementioned basic principles, manufacturers can realise new designs that fit in with the basic design. This also makes it possible to realise a growth model for sustainable material use;

- In the event of emergencies, solutions can be realised quicker by splitting up the modules into one functional step;

- Initial design costs may be higher. However, these costs can be recovered quickly if multiple plants are constructed in series.

- The design includes implementation aspects, making implementation more efficient and generating fewer failure costs. The design also includes user aspects that result in a more efficient use.

- The MSSTP provides a framework for the new construction philosophy, which assumes shorter construction cycles. As such, new technologies can be implemented earlier, enabling further savings on running costs.

4.3.6. Work experience

The MSSTP concept is synonymous for the continued growth as a high performance for Waterschapsbedrijf Limburg. It is an inspiring and innovative project, prompting everyone to work together in an interdisciplinary team context. The innovative growth process of the MSSTP offers all those involved major substantive challenges to come up with pioneering ideas and actions. As a result, the knowledge and skills of everyone involved are used to a maximum extent. The innovative character and potential of the MSSTP result in a working environment that gets the best out of people. It is a continuous process of 'learning, improvement and innovation' and as such a process of 'committing and captivating' the talent in our organisation. This working culture encourages innovative behaviour and results in an environment where people act on instinct instead of displaying risk-avoiding behaviour (leaning by doing). Working as a team, pioneering ideas, creativity, flexibility, risk appetite and an entrepreneurial spirit are vital key skills if we want to realise the strategic objectives of our organisation. The intrinsic motivation of people (the willingness to give a maximum performance and the ability to conquer obstacles) is an important success factor for the realisation of the MSSTP project. Participation in the MSSTP project requires a lot of passion, inspiration, commitment, loyalty and engagement from everyone involved. A recent MTO study showed that our organisation scores high on these aspects. 4.3.7 Conclusions

The comparison in this chapter between the conventional water treatment plant and the innovative MSSTP system clearly is in favour of the MSSTP system. The MSSTP scores better on all

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characteristics that are important, now and in the future, for an optimal and socially responsible water treatment plant. The MSSTP allows for a response to the external influencing factors of pressure on costs, sustainability and innovation and as such the need for flexibility. The MSSTP symbolises a strong competitive position in the world of wastewater. The table below confirms the analysis that the MSSTP scores better on various aspects compared to a conventional sewage treatment plant. Table - analysis overview

Aspect Conventional concept MSSTP concept Net annual costs o ++ Management and maintenance o + Flexibility o + Sustainability o + Design and construction times o ++ Work experience o + In the next chapter we will further substantiate the drop in net annual costs and higher sustainability on the basis of a comparison between different versions of a conventional sewage treatment plant and an MSSTP.

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5 Business Case: water treatment plant of 60,000 PE 5.1. Introduction The power of the modular design and construction philosophy was demonstrated in the previous chapter by means of a comparison with a conventional water treatment plant. The major potential of this philosophy was recently confirmed, despite the fact that the unique character of the MSSTP in terms of flexibility and short construction time was ignored in the financial analysis. This chapter reinforces the substantiation for the financial and sustainability benefits of the MSSTP. Paragraph 5.3 outlines two comparative analyses of the net annual costs of different types of water treatment plants with a capacity of 60,000 PE (150 g of total oxygen demand)24. This comparison takes into account construction times and flexibility gains of the MSSTP. An initial analysis compares two versions of existing conventional treatment plants - a version that does and a version that does not use the latest technology - with two versions of the MSSTP (one with Ulbas-UCT and one with Nereda technology) for a waste load scenario of (N=16.5 mg/l). The second analysis compares a newly built conventional treatment plant that uses the latest technology with the two aforementioned MSSTP versions for a waste load of (N= 10 mg/l). Both analyses demonstrate the exceptional result of a drop in net annual costs of approximately 20% and higher when using the MSSTP versions compared to the conventional water treatment versions. Paragraph 5.4 outlines a similar analysis for the different versions, but for sustainability. The sustainability comparison too confirms the enormous potential of the MSSTP. Before focusing on the analyses, paragraph 5.2 offers a more detailed description of the different versions. The chapter is concluded with summarising conclusions. 5.2 Description of versions 24 The capacity of 60,000 PE was chosen for the sake of the realistic character of the business case. Waterschapsbedrijf Limburg has detailed data about this version. This made it possible to make calculations with an accuracy of 10%. On average, this version is one of the most popular sewage treatment plants in the Netherlands on the basis of capacity.

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The analysis compares three versions of the conventional sewage treatment plant with four versions of the MSSTP system. The seven versions with effluent requirements about P and N are shown in the table below. A rainwater buffer has been provided parallel to organic treatment for all versions. Appendix 11 provides an overview of the dimensions of the plant sections. Table - description of versions

Versions 1 2 3 4a 4b 4c 4d

Active sludge process

Pre-sedimentation

Pre-precipitation

Ulbas-UCT

Ulbas-UCT

Nereda MSSTP

Nereda MSSTP

Ulbas-UCT

MSSTP

Ulbas-UCT

MSSTP

N (mg/l) 16.5 16.5 10 16.5 10 16.5 10

P (mg/l) 0.5 0.5 1 0.5 1 0.5 1

Version 1 is inspired on an existing treatment plant of WBL that applies pre-sedimentation and pre-precipitation. For the other versions, wastewater is treated directly, without pre-sedimentation. Ulbas-UCT (a University of Cape Town process) is an ultra low-burden active sludge process with far-reaching organic de-phosphatising and nitrogen removal. The Nereda technology is a recently developed aerobic pellet sludge technology, which is applied in Epe at a scale of approximately 60,000 PE. Details of versions of the conventional sewage treatment plant: Version 1 Reconstruction of the existing treatment plant: pre-sedimentation; pre-precipitation and plug flow active sludge process, underground tanks and N = 16.5 mg/l and P = 0.5 mg/l. Version 2 Newly constructed treatment plant using the latest technology: direct treatment in Ulbas-UCT with organic de-phosphatising, concentric rings and underground tanks and N = 16.5 mg/l and P = 0.5 mg/l. Version 3 Newly constructed treatment plant using the latest technology: direct treatment in Ulbas-UCT with organic de-phosphatising, concentric rings and underground tanks and N = 10 mg/l and P = 1 mg/l.

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Details of versions of the MSSTP: Version 4a Newly constructed Nereda MSSTP: direct treatment in Nereda with organic de-phosphatising with intermediate buffer tank, aboveground tanks and N = 16.5 mg/l and P = 0.5 mg/l. Version 4b Newly constructed Nereda MSSTP: direct treatment in Nereda with organic de-phosphatising with intermediate buffer tank, aboveground tanks and N = 10 mg/l and P = 1 mg/l. Version 4c Newly constructed Ulbas-UCT MSSTP: direct treatment in Ulbas-UCT with organic de-phosphatising, aboveground tanks and N = 16.5 mg/l and P = 0.5 mg/l. Version 4d Newly constructed Ulbas-UCT MSSTP: direct treatment in Ulbas-UCT with organic de-phosphatising, aboveground tanks and N = 10 mg/l and P = 1 mg/l. The table below shows the influent details that serve as a basis for the technological calculations. Table - influent details

Influent value unit

COD load 6,570 kg/day

OOD load 2,731 kg/day

SS load 3,000 kg/day

N-Kj load 532 kg/day

N-NO3 load 8 kg/day

P-tot load 80 kg/day

Dry weather supply ("DWA") 930 m³/h

Maximum supply

Maximum supply rainwater buffer

4,371

2,914

1,457 m3/h

DWA period 12 hour/day

Average capacity (Qaverage) 14,250 m³/day

PEs (at 150 g of total oxygen 60,000 -

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demand)

5.3 Financial comparison The tables below show the average net annual costs for a 30-year period25 with regard to the different types of water treatment plants (60,000 PE at 150 g of total oxygen demand). We studied two effluent scenarios26. Table - financial comparison for effluent requirements N=16.5 mg/l and P=0.5 mg/l and 60.000 PE (150 g of total oxygen demand)

Effluent scenario I 1 2 4a 4c

Plug flow Conventional UCT

Nereda MSSTP

UCT MSSTP

Effluent quality N =16.5 N =16.5 N =16.5 N =16.5

P =0.5 P =0.5 P =0.5 P =0.5

average net annual costs € 2,220,500 € 2,029,800 € 1,684,900 € 1,726,800

comparison with version 1 100.0% 91.4% 75.9% 77.8%

Table - financial comparison for effluent requirements N=10 mg/l and P=1 mg/l and 60.000 PE (150 g of total oxygen demand)

Effluent scenario II 3 4b 4d

Conventional UCT

Nereda MSSTP

UCT MSSTP

Effluent quality N=10 N=10 N=10

P=1 P=1 P=1

average net annual costs € 2,039,900 € 1,695,100 € 1,737,000

comparison with version 3 100.0% 83.1% 85.2%

The calculations demonstrate that all MSSTP versions, without exception, are less expensive than conventional versions. Depending on effluent quality, the Nereda MSSTP versions show 17 to 24%

25 Appendix 10 substantiates the amounts included under running costs; this relates to energy costs (10.0), costs for chemicals consumption and costs for maintenance and operation (10.2). 26 Appendix 10.3 gives the entire calculation model on the basis of which we arrived at the figures in the table above. The calculation model was checked and approved by Professor Ronald Mahieu, Professor of Entrepreneurial Finance, at Eindhoven University of Technology.

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lower net annual costs than the conventional versions. Approximately 60% of this gain can be attributed to the use of the MSSTP design and construction concept. For the MSSTP that uses Ulbas-UCT technology, that figure is 15 to 22%. Versions of the Nereda MSSTP score slightly better in terms of net annual costs than versions of the Ulbas-UCT MSSTP. On a scale of 60,000 PE, making a comparison between a new conventional treatment plant (version 1) and a new Nerada MSSTP (version 4a), the annual advantage in terms of net costs is approximately EUR 500,000. Widely extrapolated in Limburg, this would yield an average annual advantage of approximately EUR 15,000,000.

Sensitivity analysis

The above financial calculations were subjected to sensitivity analyses. The calculation parameters in the calculation model, which cannot be influenced by WBL, have been subjected to a risk analysis on the basis of the Monte Carlo simulation27, using @RISK software.

The parameters that could not be influenced have been defined and the spread is given for each parameter. The parameters as well as the spread were determined by units at WBL on the basis of historic data and trends. They are shown in table 4.

Table - calculation parameters that could not be influenced and spread

Parameter Unit Lower limit Basis Upper limit

Inflation % 1.5 2 2.5

Interest % 3.75 4.75 5.75

Personnel costs €/ie 1.42 1.60 1.81

Energy price €/kWh 0.083 0.092 0.106

PE for water line and thickening €/kg 1.57 2.15 2.73

Aluminium product for water line €/kg 162.39 222.45 282.51

Iron product for water line €/kg 93.98 128.08 162.18

The net annual costs and corresponding spread have been determined for each version. The figures below show that the most negative scenario for the MSSTP versions is still better than the most positive scenario for a conventional version.

27 The Monte Carlo simulation is a simulation technique, in the course of which a physical process is simulated not once, but multiple times, each time with different start conditions. The result of this series of simulations is a spread function that visualises the entire scope of possible outcomes.

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Figure 3 - annual costs (N=16.5 mg/l, P=0.5 mg/l)

Average net annual costs

(versions: N = 16.5 mg/l / P = 0.5 mg/l)

Version 1 Version 2 Version 4a Version 4c

Figure 4 - annual costs (N=10 mg/l, P=1 mg/l)

Average net annual costs

(versions: N = 10 mg/l / P = 1 mg/l)

Version 3 Version 4b Version 4d

Explanation: in the interval diagrams, the small circle represents the average value of the annual costs, while the lines above and below the circle represent the spread that follows from the variation on the parameters that cannot be influenced.

Variant 4cVariant 4aVariant 2Variant 1

2400000

2300000

2200000

2100000

2000000

1900000

1800000

1700000

1600000

1500000

€

Variant 4dVariant 4bVariant 3

2200000

2100000

2000000

1900000

1800000

1700000

1600000

1500000

€

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5.4 Sustainability comparison

Sustainability plays an important role in the choice of treatment plant. As indicated in paragraph 4.3.4, construction method, construction materials and the running of each design form of a version are compared to each other by means of a transparent and objective methodology. In order to set off the total energy use of these aspects against each other, the total energy consumption for the owner throughout the period of use is determined (the Total Energy use of Ownership (TEO)).

The comparison looks at different design versions of a plant with a capacity of 60,000 population equivalents. The total energy consumption for the different versions is shown in the figure below. The energy for the construction phase shows the construction method (underground/aboveground) and construction materials. The remainder is full operation/energy use.

Figure 5 - comparison of energy use of different versions

Energy use in primary energy per person [Watt] Chemicals sludge line / Chemicals water line / Operational energy / Energy construction phase RWZI = sewage treatment plant

The figure shows that daily energy use (operational and chemicals) for all versions is much more important than the energy use for the construction phase. This indicates that from a sustainability point of view, it is particularly important to optimise this part: in other words: to achieve the required effluent quality at the lowest possible use of energy and chemicals.

The extent of extra energy use (construction phase) with a shorter period of use of a plant is relatively small. This indicates that the shorter period of use for a modular construction hardly affects the total energy use (TEO). On the basis of TEO it is therefore justified to opt for a modular plant that can be modified in accordance with the current situation to the greatest possible extent.

0

2

4

6

8

10

12

RWZI 1 RWZI 2 RWZI 3 RWZI 4a RWZI 4b RWZI 4c RWZI 4d Ene

rgie

gebr

uik

in p

rimai

re e

nerg

ie p

er p

erso

on [W

att]

Chemicalien sliblijn

Chemicalien w aterlijn

Operationele energie

Energie aanlegfase

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A comparison of the versions based on total energy use for construction method, construction materials and running shows that Nereda MSSTP versions 4a and 4b score best. This applies to the amount of material required, but mainly to the running of the plant (daily energy and chemicals use).

The MSSTP versions with Ulbas-UCT (versions 4c and 4d) perform virtually the same as conventional plants when it comes to material use. However, in terms of running they score worse than conventional plants. Among other things, this is caused by the aboveground construction method, which requires extra pump energy. The Nereda MSSTP versions are also constructed aboveground, but thanks to hydropower screw pumps, these versions can recover part of this pumping energy in a profitable way.

The operational energy use of a conventional sewage treatment plant with pre-sedimentation tank and pre-precipitation (sewage treatment plant 1) is lower than that of the other versions. This is because in the process of pre-precipitation by means of chemical dosing, a lot of organic material is collected before it enters the biology unit. This unit then needs a lot less energy to treat the wastewater. With this version therefore, operational energy use should not be regarded separately from the energy use for the chemicals water line.

To compare the construction phase of the various versions, we looked at the amount of energy needed to construct the plants (see appendix 10). We also compared the various materials, taking the possibilities of reuse into account. A final material choice based on sustainability is yet to be made and will be determined in a follow-up study.

5.5 Conclusions business case

The analysis in this chapter demonstrates that all MSSTP versions score considerably better than the conventional sewage treatment plants in terms of net annual costs. The Nereda MSSTP versions score better than the Ulbas-UCT MSSTP versions. Another important fact is that the Nereda MSSTP versions score significantly better in terms of sustainability than versions of the Ulbas-UCT MSSTP. Sustainability is not a principle that can be ignored in today's social context, especially since the water authorities have ambitions in areas such as climate change, having confirmed this in the Climate Agreement (see paragraph 2.2, p. 16).

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6 Conclusions

External factors have forced water authorities and water authority executives to take measures to reduce costs levels, to increase sustainability of activities and to improve the quality of treated water at lower costs. In order to improve its competitive position, Waterschapsbedrijf Limburg has developed an innovation called the Modular Sustainable Sewage Treatment Plant. The strength of this innovation lies in the modular design and construction philosophy, which allows customised treatment. The analyses conducted within the context of this report show that a new concept offers a solution for the many challenges in the water authority industry, allowing for a strong competitive position. Compared to a conventional sewage treatment plant, the MSSTP offers excellent performances in terms of cost savings, sustainability, innovativeness, flexibility with regard to external developments such as the tightening of effluent standards, changes to supply, the use of residual heat, the treatment of overflow water, design and construction times, management and maintenance and work experience. The Nereda MSSTP performs slightly better than the Ulbas-UCT MSSTP. This is not considered in the table below. Table - comparative overview

Characteristics Conventinoall sewerage treatment

plant

MSSTP

Costs o ++ Sustainability o o/+ General innovativeness o ++ Flexibility regarding

- Tightening of effluent standards - Supply of different types of water - Changes to supply - The use of residual heat - The treatment of overflow water - Technological developments

o

o/+ + - -

o/+ -

++

+ + + + + +

Design and construction times - + Management and maintenance

- Reliability - Availability - Maintainability - Safety - Costs

+ o o + o

+ +

++ + +

Work experience - Interdisciplinary cooperation as a team - Using and stretching knowledge and talent

o o o

+

++ ++

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- Stimulating the intrinsic motivation Based on our analyses, we can justifiably conclude on a sectoral level that conventional sewage treatment plants are surpassed by this modular innovation. We think the MSSTP is the new standard for our sector. A standard that has global potential, thanks to its flexible and all-round deployability on a small and large scale. In terms of follow-up steps, we recommend Waterschapsbedrijf Limburg to make a detailed analysis of potential partners for the development and construction of the concept. Taking the results of the patent application into account, Waterschapsbedrijf Limburg should also start thinking about how it can play the most effective role in the commercialisation process. The specifics of this role, the organisational and administrative form of this activity will form the subject of a follow-up study. However, we feel the MSSTP has such potential that this analysis should not preclude a separate activity.

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Glossary

Aerobic pellet sludge technology Treatment technology with pellet-like sludge.

Anaerobic tank Process section of the treatment plant with anaerobic conditions (no oxygen and low levels of nitrate), required for organic de-phosphatising.

COD load Chemical oxygen demand in kg/d, required for full oxidation

Communal wastewater Urban wastewater: a mixture of domestic and industrial wastewater and rainwater

Demineralised water Demineralised water is water which has all salts removed

Effluent Treated wastewater

First flush A term in (urban) hydrology, indicating that during rainfall, most of the pollution can be found in the firs section of the water supplied to the sewage treatment plant

MBR Membrane bioreactor

N-Kj load Supply of Kjeldahl nitrogen in kg N/d

N-NO3 load Supply of nitrate nitrogen in kg N/d

Nereda Aerobic pellet sludge technology

OOD load Organic oxygen demand in kg/d, required for organic oxidation

Operation in batches Operations during which wastewater is continuously discharged

Organic de-phosphatising The absorption of phosphate in sludge

PE Population equivalent, the average waste load discharged by one person in wastewater per day. PE = 150 g of total energy demand

Plug & Play A property of (system) parts, making it easier to exchange them quickly

Plug flow active sludge process

Hydraulic term, in the course of which a liquid enters a tank and flows towards the exit of the tank without any

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noticeable internal mixing

Pre-precipitation A de-phosphatising method in the course of which iron salts are dosed in the influent, and the chemical deposit is separated in the pre-sedimentation tank

Priority substances Substances are regarded as priority substances if, due to their hazardous properties, emissions and/or degree of occurrence in the environment, they pose a more than negligible risk to man and/or the environment

Raw material recovery The recovery of raw materials from wastewater and sludge streams

SS load Volume of suspended substances

Ulbas-UCT Ultra-low burden active sludge process with organic de-phosphatising, developed by the University of Cape Town

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