Wastewater Reuse, Volume 2 E-Book

Kader Gaid

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: ISTE Invoiced
• Sprache: Englisch

Seitenzahl: 327

Veröffentlichungsjahr: 2025

Beschreibung

Water issues are inextricably linked to sustainable development since water must meet the needs of present and future generations.

The reuse of wastewater is a socioeconomic challenge for the development of drinking water and wastewater services. It has the following advantages: it increases usable water resources, preserves natural resources and alleviates water shortages caused by climate change.

Wastewater Reuse 2 provides a comprehensive and educational overview of the many ways wastewater can be reused, the variety of treatments, their performance, their conditions of use and how to combine them to give wastewater a new lease on life. Droughts are already a concern in many parts of the world; however, we now have new technologies to rely on.

Leseprobe

Table of Contents

Cover

Table of Contents

Title Page

Copyright Page

1 Case Studies with Tertiary Treatment

1.1. Limited urban use, irrigation of non-food or processed crops

1

1.2. Nosedo plant (Milan, Italy): irrigation

1.3. The Hermitage station (Reunion Island)

1.4. The Barcelona plant (Spain): regeneration of wetlands, irrigation

1.5. Ajman (United Arab Emirates): irrigation and non-drinkable urban use

1.6. Al Wathba treatment plant (Abu Dhabi): recreational areas, green spaces, industries

1.7. Burj Khalifa lake (Dubai): reuse wastewater for a recreational area

1.8. Darling Quarter (Sydney, Australia): wastewater reuse in a neighborhood

1.9. References

2 Micropollutants

2.1. Introduction

2.2. Pesticides

2.3. Pharmaceuticals and industrial residues

2.4. Technologies for removing pesticides and emerging micropollutants

2.5. References

3 Microfiltration and Ultrafiltration Membranes

3.1. Operating principle and mechanisms

3.2. Sizing parameters

3.3. Microfiltration and ultrafiltration applied to wastewater treatment

3.4. Improved secondary treatment: membrane bioreactors

3.5. Membrane layout in the reuse process

3.6. Hybrid process: combining chemical processes with MF/UF membranes

3.7. Conclusion

3.8. References

4 Reverse Osmosis

4.1. Membranes

4.2. Principles of operation and separation

4.3. Wastewater treatment with reverse osmosis membranes

4.4. Reverse osmosis in the wastewater reuse process

4.5. Performance

4.6. Conclusion

4.7. References

5 Applications for Drinking Water, Specific Industrial Water and Groundwater Recharge

5.1. Windhoek: drinking water, specific industries and groundwater recharge

5.2. The Durban plant (South Africa)

5.3. Kranji (Singapore): irrigation, indirect drinking water, specific industries

5.4. Illawarra (Australia): application, ocean protection, irrigation and industry

5.5. Honolulu: irrigation and industrial applications

5.6. Gerringong and Gerroa (Australia): controlled irrigation and beach protection applications

5.7. Playgrounds and leisure parks (France)

5.8. References

6 What Does the Future Hold for Wastewater Reuse?

6.1. Challenges and prospects

6.2. What about drinking water?

6.3. Wastewater: Is it a real alternative?

6.4. References

Index

End User License Agreement

List of Tables

Chapter 1

Table 1.1. Uses with tertiary treatment

Table 1.2. Reduction across the entire chain: from raw water to water for reus...

Table 1.3. Water quality at the outlet of the Nosedo tertiary treatment plant

Table 1.4. Tertiary filtration dimensions

Table 1.5. UV reactor dimensions

Table 1.6. Water quality at tertiary treatment inlet and outlet

Table 1.7. Water quality requirements for wastewater reuse at the Barcelona si...

Table 1.8. Performance of the Barcelona wastewater reuse plant

Table 1.9. Operating conditions for tertiary treatment

Table 1.10. Fecal coliform guarantees at the Al Wathba plant (Abu Dhabi)

Table 1.11. Dimensions of the recreational lake

Table 1.12. Actiflo dimensions (Veolia)

Table 1.13. Disk filter dimensions (Hydrotech)

Table 1.14. Quality of water produced

Table 1.15. Comparison of parameters to be removed at the Darling Quarter plan...

Chapter 2

Table 2.1. Main families and organic compounds

Table 2.2. Example of an assessment of micropollutant concentrations in water

Table 2.3. Examples of micropollutant concentrations in treated wastewater

Table 2.4. Redox potentials of some conventional chemical oxidizers

Table 2.5. Ozonation performance on drug residues

Table 2.6. AC reactor design parameters (Veolia)

Table 2.7. Adsorption of pesticides on activated carbon

Table 2.8. K and 1/n parameters of the Freundlich model

Table 2.9. Characteristics and adsorption parameters of micro-grain activated ...

Table 2.10. Freundlich parameters (K and 1/n) for some drugs

Table 2.11. Characteristics of some granular activated carbons used for microp...

Table 2.12. Adsorption state of some drug residues on activated carbon

Table 2.13. Performance of two PACs combined with ozone

Chapter 3

Table 3.1. Single-bore and multi-bore hollow-fiber membranes

Table 3.2. Examples of flux size and chemical backwash frequencies for pressur...

Table 3.3. Advantages of microfiltration and ultrafiltration

Table 3.4. Examples of process guarantees in MF/UF

Table 3.5. Physicochemical and microbiological results obtained at a MBR stati...

Chapter 4

Table 4.1. Examples of SDI results for two types of water

Table 4.2. Limit values for some acceptable elements and substances in high-pr...

Table 4.3. Physicochemical composition of treated wastewater, permeate and con...

Table 4.4. Pore diameters of nanofiltration and low-pressure reverse osmosis m...

Table 4.5. Retention percentage of Toray HMA and XLE membranes (Dow/Filmtec) a...

Table 4.6. Low-pressure reverse osmosis membrane effectiveness with regard to ...

Chapter 5

Table 5.1. Physicochemical quality of plant inlet water and produced water

Table 5.2. Bacteriological analysis results compared with required guarantees

Table 5.3. Composition of raw wastewater from Umlaas treatment plant

Table 5.4. Clarifier operating characteristics

Table 5.5. Sizing dual-media filters

Table 5.6. Sizing granular activated carbon filters

Table 5.7. Performance and compliance of different parameters of produced wate...

Table 5.8. Bacteriological compliance of produced water

Table 5.9. Some parameters of the effluent leaving the Kranji treatment plant

Table 5.10. CMF-S workshop performance

Table 5.11. Sizing and performance of RO membrane workshop

Table 5.12. Some parameters of produced water

Table 5.13. Flow connected to the Wollongong (Illawarra) treatment plant

Table 5.14. Average raw wastewater characteristics

Table 5.15. Water quality required at treatment plant outlets

Table 5.16. Physicochemical and microbiological characteristics of water to be...

Table 5.17. Water quality after microfiltration and reverse osmosis

Table 5.18. Physicochemical characteristics of raw effluent

Table 5.19. Guaranteed quality of produced water

Table 5.20. Composition of raw wastewater, and produced and distributed water

Chapter 6

Table 6.1. Physicochemical performance of different processes

Table 6.2. Performance comparison between the various technologies available

List of Illustrations

Chapter 1

Figure 1.1. Tertiary treatment with various filters and chlorine disinfection ...

Figure 1.2. Reusing water for non-drinking urban use

Figure 1.3. Wastewater treatment plant with reuse (Nosedo, Milan)

Figure 1.4. Nosedo wastewater treatment plant including tertiary treatment

Figure 1.5. On-site spraying with reused water (Nosedo)

Figure 1.6. Map of Reunion Island (France)

Figure 1.7. UV reactors and filters

Figure 1.8. Tertiary treatment plant (Reunion Island, France)

Figure 1.9. Treatment plant for wastewater reuse in Barcelona

Figure 1.10. Barcelona plant with tertiary treatment

Figure 1.11. Wastewater reuse in Ajman (United Arab Emirates)

Figure 1.12. Reverse osmosis membrane and service station for reused wastewate...

Figure 1.13. Distribution of treated wastewater by “non-drinking water” tanker...

Figure 1.14. Al Wathba wastewater treatment and reuse plant

Figure 1.15. Tertiary treatment plant (Al Wathba, Abu Dhabi)

Figure 1.16. Free chlorine residual at tertiary treatment outlet

Figure 1.17. Changes in turbidity and TSS in reused water

Figure 1.18. Changes in BOD5 at tertiary treatment outlet

Figure 1.19. Applications for reused wastewater

Figure 1.20. Treatment plant for Burj Khalifa lake (Dubai)

Figure 1.21. Burj Khalifa lake water quality with reused wastewater

Figure 1.22. Water features on the lake

Figure 1.23. Darling Quarter (Sydney)

Figure 1.24. Wastewater reuse in a neighborhood

Figure 1.25. Reuse station equipment

Figure 1.26. Reuse for cooling towers, irrigation and toilet flushing

Chapter 2

Figure 2.1. Different categories of micropollutants.

Figure 2.2. Simplified diagram of the water cycle containing pesticides, drug ...

Figure 2.3. Outcome of some substances in wastewater treatment plants

Figure 2.4. Three-tank ozonation reactor

Figure 2.5. Ozonation of atrazine and by-products at different ozone doses

Figure 2.6. Alachlor oxidation by-products

Figure 2.7. Percentage of drug elimination with different ozone doses (DOC: di...

Figure 2.8. Ozonation performance at pH 6.0 for different O3 dosages (6.9 mg.L...

Figure 2.9. Ozonation of micropollutants at various g O3/g DOC ratios (DOC at ...

Figure 2.10. Identification of diclofenac ozonation by-products

Figure 2.11. Identification of carbamazepine ozonation by-products

Figure 2.12. Some advanced oxidation solutions

Figure 2.13. Main combinations used in drinking water

Figure 2.14. Advanced chemical oxidation with O

3

/H

2

O

2

Figure 2.15. Percentage of pesticide and drug oxidation with UV/H

2

O

2

.

Figure 2.16. By-products identified with UV/H2O2 for carbamazepine and diclofe...

Figure 2.17. Disposal of activated carbon in the water reuse process

Figure 2.18. PAC reactor with recirculation

Figure 2.19. Adsorption capacity (mg.g−1) of pesticides as a function of log K...

Figure 2.20. Micropollutant removal performance with different dosages of Puls...

Figure 2.21. Opaline® C process: combination of powdered activated carbon and ...

Figure 2.22. Removal of micropollutants with Opaline® C process (Veolia)...

Figure 2.23. Removal of micropollutants using GAC or in combination with ozone

Figure 2.24. Adsorption of four drugs on a GAC filter (Aquasorb 2000)

Figure 2.25. Effectiveness of GAC against various drugs as a function of log K...

Figure 2.26. Summary of Actiflo® Carb performance with O3/PAC reactor coupling...

Figure 2.27. Removal of micropollutants with the in situ O3 /PAC combination (...

Figure 2.28. LC UVD of samples treated with Actiflo® Carb with and without act...

Figure 2.29. Evolution of atrazine elimination, with ozonation alone and with ...

Figure 2.30. Removal of some drugs with O

3

/GAC according to two O

3

/DOC ratios.

Chapter 3

Figure 3.1. Classification of different species according to size and membrane...

Figure 3.2. Microorganism cut-off with filtration, microfiltration and ultrafi...

Figure 3.3. Ultra-filtered water outlet feed points.

Figure 3.4. Example of a hollow fiber module in internal/external configuratio...

Figure 3.5. Membranes in a pressurized configuration.

Figure 3.6. Vertical/horizontal configuration for pressurized membranes.

Figure 3.7. Horizontal filtration mode (Xiga for Cabot-Norit)

Figure 3.8. Horizontal backwash filtration mode (Xiga for Cabot-Norit)

Figure 3.9. Recommended net flux for both configurations as a function of turb...

Figure 3.10. Membranes in a submerged configuration.

Figure 3.11. Membranes in a submerged configuration.

Figure 3.12. Washing efficiency based on resistance to fouling

Figure 3.13. Tangential and frontal filtration.

Figure 3.14. Different types of clogging

Figure 3.15. Development of clogging on an MF membrane after several backwash ...

Figure 3.16. Sequential diagram of permeability recovery after clogging

Figure 3.17. Turbidity of filtered water as a function of MF/UF pore diameter

Figure 3.18. Specific energy consumption by MF/UF flux

Figure 3.19. Wastewater treatment with membrane process

Figure 3.20. Compact solution with membrane process

Figure 3.21. Clogging mechanisms of MBR membranes

Figure 3.22. Size of viruses present in water and associated pathogenic risk

Figure 3.23. MBR and disinfection

Figure 3.24. MBR followed by ultrafiltration

Figure 3.25. Microfiltration installed downstream of a wastewater treatment pl...

Figure 3.26. Gravity filtration upstream of microfiltration

Figure 3.27. Gravity filtration upstream of ultrafiltration

Figure 3.28. Gravity filtration and advanced treatment upstream of UF

Chapter 4

Figure 4.1. Pressure tube assembly

Figure 4.2. Interconnectors in a high-pressure membrane.

Figure 4.3. Various pressure tube components (baseplate a), Victaulic b) and f...

Figure 4.4. Simplified conceptual diagram of membrane separation

Figure 4.5. Separation into two streams (permeate and concentrate (reject))

Figure 4.6. Pre-treatment with a MBR upstream of the RO membrane train

Figure 4.7. Pre-treatment with conventional treatment upstream of the RO membr...

Figure 4.8. Pre-treatment with MF or UF membrane upstream of the RO membrane t...

Figure 4.9. Experimental determination of the MFI

Figure 4.10. Factors affecting membrane clogging

Figure 4.11. Specific energy consumption as a function of flux/conversion rate...

Figure 4.12. Mass flow diagram

Figure 4.13. Membrane bioreactor/reverse osmosis system

Figure 4.14. Conventional wastewater treatment plant followed by a double memb...

Figure 4.15. Double-membrane filter with advanced post-treatment oxidation

Figure 4.16. Correlation between molecular weight and molecule diameter

Chapter 5

Figure 5.1. Windhoek wastewater reuse plant (Namibia)

Figure 5.2. Windhoek wastewater reuse plant process

Figure 5.3. Flotation unit a) and ultrafiltration unit b)

Figure 5.4. Plant performance on organic substances expressed in DOC, COD and ...

Figure 5.5. Changes in turbidity and fecal coliforms throughout the process

Figure 5.6. Diagram of wastewater reuse in Durban (South Africa)

Figure 5.7. Durban wastewater treatment plant

Figure 5.8. Wastewater treatment plant secondary clarifier

Figure 5.9. Use of Jacobs industrial sewer to compensate for Umlaas flow defic...

Figure 5.10. Tertiary treatment process

Figure 5.11. View of the wastewater reuse plant

Figure 5.12. Multiflo clarifiers

Figure 5.13. Ozone generator (Siemens (ex-Trailigaz))

Figure 5.14. Granular activated carbon filters

Figure 5.15. Residual iron measured in produced water

Figure 5.16. Guaranteed and measured common germs

Figure 5.17. Performance assessment of each stage of treatment

Figure 5.18. Kranji wastewater reuse treatment plant (Singapore)

Figure 5.19. CMF-S a) and reverse osmosis b) membranes

Figure 5.20. Evolution of transmembrane pressure on CMF-S membranes

Figure 5.21. Water output from UV disinfection unit

Figure 5.22. Wollongong’s three treatment processes

Figure 5.23. General view of the Wollongong treatment plant (Illawarra, Austra...

Figure 5.24. Microfiltration workshop a) and reverse osmosis workshop b)

Figure 5.25. Port Kembla a) and Wollongong outfall b)

Figure 5.26. Reverse osmosis membrane workshop

Figure 5.27. General view of the Honolulu wastewater treatment and reuse plant

Figure 5.28. Location of the towns of Gerringong and Gerroa

Figure 5.29. General diagram of the Gerringong-Gerroa wastewater treatment sys...

Figure 5.30. Continuously washed sand filter a) and microfiltration b)

Figure 5.31. Diagram of the wastewater reuse plant

Figure 5.32. (A) A year of MBR operations

Figure 5.32. (B) A year of MBR operations (continued)

Figure 5.33. Two applications for reused water

Chapter 6

Figure 6.1. The best way to reuse wastewater.

Guide

Cover Page

Table of Contents

Title Page

Copyright Page

Begin Reading

Index

WILEY END USER LICENSE AGREEMENT

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Wastewater Reuse 2

Micropollutants, Membranes and Treatment Procedures

Kader Gaid

First published 2025 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd27-37 St George’s RoadLondon SW19 4EUUK

www.iste.co.uk

John Wiley & Sons, Inc.111 River StreetHoboken, NJ 07030USA

www.wiley.com

© ISTE Ltd 2025The rights of Kader Gaid to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s), contributor(s) or editor(s) and do not necessarily reflect the views of ISTE Group.

Library of Congress Control Number: 2024950901

British Library Cataloguing-in-Publication DataA CIP record for this book is available from the British LibraryISBN 978-1-78630-980-8

1Case Studies with Tertiary Treatment

The effective integration of wastewater reuse into water resource management is based on the quantity of water required for a specific application, as well as the associated water quality requirements.

The key challenge lies in choosing the most appropriate process to meet local constraints. The technical tools available are those already used for wastewater or drinking water treatment.

The process of selecting a tertiary treatment system involves at least three steps, the first of which is to assess the performance of available processes in relation to the quality of the water to be treated and the end use. The next step is to analyze regulatory constraints. The techno-economic assessment takes into account existing infrastructure and equipment, as well as sources of financing for investment and operation.

The quality requirements for each use are not the same. Generally speaking, non-drinking uses only require minor treatment.

A significant number of tertiary filtration-disinfection plants have been built for urban water reuse applications such as parks, school grounds and golf courses, as these processes involving solid/liquid separation and disinfection are simple and inexpensive.

There are significant regional and seasonal variations in water use models. For example, in urban areas, industrial, commercial and non-drinkable urban water requirements are the main demand for water. For agricultural applications in arid and semi-arid regions, irrigation is the main reason for water demand. Water requirements for irrigation applications tend to vary seasonally, while industrial water needs are more constant.

Tertiary treatment can therefore be used for a variety of purposes, as summarized in Table 1.1.

Table 1.1.Uses with tertiary treatment

Use categories

Uses

Non-drinking, urban

Water for public parks, sports facilities, private gardens, roadsides, street cleaning, fire hydrants, vehicle washing, air conditioning and dust control

Agricultural uses

Non-commercially processed food crops, commercially processed food crops, dairy pastures, forage, fibers, seed crops, ornamental flowers, orchards, hydroponics, aquaculture, greenhouses and viticulture

Industrial uses

Cooling water, recirculating cooling towers, washing water, washed aggregates, concrete making, soil compaction and dust control

Recreational areas

Golf courses, recreational ponds with/without public access (e.g. fishing, canoeing and swimming) and aesthetic reservoirs without public access

Environmental areas

Wetlands, swamps, marshes, flow augmentation, wildlife habitat and forestry

The choice of tertiary treatment includes the following processes:

membranes included in secondary treatment (membrane bioreactor (MBR));

simple disinfection: chlorine, peracetic acid, performic acid;

combined disinfection: ozone-chlorine, UV-chlorine;

tertiary filtration-disinfection: chlorine tertiary filtration, ozone-chlorine tertiary filtration, UV-chlorine tertiary filtration;

quaternary treatment: ozone-granular activated carbon, advanced chemical oxidation;

microfiltration (MF) membranes, ultrafiltration (UF) membranes, MF or UF followed by nanofiltration (NF) or reverse osmosis (RO) membranes;

MF and UF can be coupled with advanced oxidation, ozone-GAC, etc.

The choice of process depends on a number of factors, the most important of which are effluent quality, type of use, quality requirements and plant size. Depending on local conditions and technical and economic criteria, different processes can be considered.

Combined filtration-disinfection technologies or MF membranes guarantee improved water quality for the various uses listed in Table 1.1. Their implementation is helping to ensure better environmental protection and new applications in urban areas.

They reliably ensure good water quality (removal of suspended solids, viruses and pathogens). The most common method of disinfecting wastewater is chlorination. In some countries, the potential toxicity of chlorine by-products makes this technique less appealing. Ultraviolet irradiation appears to be an emerging method. Its efficacy is comparable, if not often superior, to the elimination of viruses and bacteria, but it has no residual. Ozone disinfection is not widely used, but it is gaining ground due to its excellent effectiveness in inactivating pathogens.

Tertiary treatment therefore allows direct reuse, in other words, the immediate use of treated wastewater, without passing it through or diluting it in the natural environment.

Due to consumer quality requirements, this treatment can only be applied for non-drinkable uses in the agricultural (irrigation), industrial and urban sectors.

The microbiological guarantees expected for each use are summarized in Table 1.2.

Table 1.2.Reduction across the entire chain: from raw water to water for reuse

Uses

Reduction of viruses Log 10

Reduction of protozoa Log 10

Reduction of bacteria Log 10

Irrigation of food crops

7.0

6.5

7.0

Car washing

5.5

4.5

5.5

Laundry

4.5

3.5

4.5

Cooling towers

4.5

4.0

4.5

Irrigation of non-food crops

3.5

2.5

3.5

Recreation and leisure areas

4.0

3.5

4.0

Toilet flushing

5.5

5.0

5.5

Treatment systems must contain both design and operating requirements, so as to ensure treatment reliability. Reliability features, such as alarm systems, emergency power supplies, duplication of treatment processes, emergency storage or disposal of inadequately treated wastewater, monitoring devices and automatic controllers, are important. From a public health perspective, measures must be taken to ensure reliable disinfection.

1.1. Limited urban use, irrigation of non-food or processed crops1

These applications are relatively common examples of water reuse in areas of restricted access or activity. Typical examples of this category are as follows: landscape irrigation (golf courses, cemeteries, road verges and highway medians), restricted recreational uses (recreational fishing, canoeing and other non-contact recreational activities), agricultural irrigation (forages, fibers, grain crops, pastures, nurseries, sod farms and commercial aquaculture). Water quality requirements are the same for all uses in this category.

1.1.1. Irrigation

The aim is to reduce the number of pathogens in treated wastewater by installing several barriers designed to reduce the likelihood of microorganisms being present.

The main health risk control measures for irrigation with treated and reused wastewater include the following:

wastewater treatment and quality control during distribution and in storage facilities;

the choice of appropriate irrigation methods and cultivation practices, such as irrigation of restricted areas (such as freeway landscapes, other areas where the public has limited access or exposure to reclaimed water) and irrigation in areas with free public access (such as golf courses, parks, playgrounds, schoolyards and residential landscape);

public access conditions (recreational areas, parks, green spaces, etc.);

other measures, including control of human exposure (e.g. protective measures for farm workers such as gloves and masks), harvesting measures, education of the public concerned and promotion of good hygiene practices.

Figure 1.1.Tertiary treatment with various filters and chlorine disinfection for irrigation purposes

Non-drinking treated wastewater is used as a new water source to promote agricultural and aquaculture production, industrial uses, reclamation uses such as irrigation, washing and flushing, recreation and artificial recharge. The reuse of effluent from tertiary wastewater treatment increases water sustainability in an environmentally friendly way.

Tertiary treatment is essential for compliance with the World Health Organization (WHO) guidelines and European and national wastewater discharge standards. In other words, the removal of phosphorus and other pollutants from wastewater is a legal obligation. In France, treated wastewater is most often reused for agricultural irrigation and watering green spaces. The efficiency of tertiary treatment is therefore essential to guarantee water quality prior to reuse. The various methods used ensure the complete removal of undesirable substances, allowing predefined quality objectives to be met.

For example, if wastewater is to be reused for vegetable irrigation, pathogens must be removed. In urban reuse, on the other hand, nitrogen and phosphorus are targeted during treatment. The same applies to groundwater recharge. This avoids any risk of eutrophication.

1.1.2. Industrial reuse and recycling

Industrial reuse of treated wastewater and internal recycling are now a technical and economic reality. Thermal and nuclear power plants (cooling water) are among the sectors that use wastewater in large quantities. Other applications are possible when the quality of the reused water is not very demanding, such as the mechanical and metal industries, construction (aggregate washing, concrete manufacture, equipment cleaning, cooling tower feed, excluding evaporative cooling), chimney cleaning and manufacturing water (excluding food processing).

1.1.3. Urban non-drinking water

In urban and suburban areas, treated wastewater reuse can be highly beneficial for municipalities. The most common uses are irrigation of green spaces (parks, golf courses, sports fields), landscaping (waterfalls, fountains, ponds), street or vehicle washing and fire protection, amenity ponds, swimming pools, ponds for fishing and boating, etc.

Figure 1.2.Reusing water for non-drinking urban use

1.1.4. Storage

All wastewater reuse plants require a certain amount of storage, in order to regulate daily variations in production flow. In certain sensitive cases, storage is needed to cope with the risk of interrupted production of treated wastewater or failures in the treatment plant. In water-deficient regions in particular, storage is seasonal: it will store water that is not needed in winter, to be used as and when required. It will even out daily variations in the flow from the treatment plant and store the surplus when the average wastewater flow exceeds irrigation requirements.

Storage is therefore an essential link between the treatment plant and the irrigation system. It is also used to provide insurance against the possibility of inappropriate wastewater entering the irrigation system.

1.2. Nosedo plant (Milan, Italy): irrigation

The Nosedo wastewater treatment plant (Milan, Italy) treats the wastewater of 1,250,000 population equivalent (P.E.) with nitrification and denitrification. It is the largest plant in Europe, with almost 60–70% of treated wastewater destined for agricultural use:

432,000 m

3

treated per day;

5 m

3

/s treated in dry weather;

15 m

3

/s in rainy weather;

60–70% of treated water is used for agricultural purposes.

Urban wastewater comes from the central-eastern area of Milan, from the discharger emissary of Nosedo and the Ampliamento Est collector.

The Milano-Nosedo wastewater treatment plant is one of Europe’s largest. It treats 50% of Milan’s wastewater, in particular from the central and eastern parts of the city. The plant is capable of treating around 157,000,000 m3/year of wastewater, which is then returned to the water system (Roggia Vettabbia), but also reused for irrigation purposes.

During the design phase of this plant, great attention was paid to certain aspects related to energy efficiency, such as the choice of equipment with inverters, the installation of a high-efficiency fine-bubble aeration system for oxygen transfer, and O2 probes to monitor and control oxygen concentration in each biological treatment line. It should also be noted that the Nosedo plant features biological oxidation/nitrification stages with a high sludge age, tertiary sand filtration and high-level disinfection.

Figure 1.3.Wastewater treatment plant with reuse (Nosedo, Milan)

The plant was commissioned on October 30, 2004.

Treated wastewater is used to irrigate rural areas and is accepted as a valuable resource by farmers.

The wastewater treatment plant is an excellent example of how to reduce the demand for water from conventional sources and make efficient use of water resources in many areas. Indeed, the project also includes improvements to the surrounding areas aimed at recomposing the landscape and environmental features of part of the historic Vettabbia valley, dominated by the Chiaravalle Abbey, and creating diverse habitats that are interconnected to maximize biodiversity.

Figure 1.4.Nosedo wastewater treatment plant including tertiary treatment

During the irrigation period (April–September), water is discharged into a ditch called Roggia Vettabbia Bassa. This water is then diverted to the fields through channels.

In the area served by the Emissario Nosedo, Roggia Vettabbia and Redefossi agricultural water networks, the farming system is mainly extensive and traditional, with forage crops (grass, corn), rice and cereals.

Table 1.3.Water quality at the outlet of the Nosedo tertiary treatment plant

Parameters

Raw water inlet (mg.L

−1

)

Treated water outlet (mg.L

−1

)

% of reduction

BOD5

170

<5

99

COD

300

<15

97

Total N

27

6.5

76

Total P

3.5

0.9

74

TSS

190

<5

99

Microorganisms (CFU per 100 mL)

Total coliforms

10

5

40

–

E. coli

10

4

<10

–

Water quality parameters for influent and effluent are shown in Table 1.3.

Figure 1.5.On-site spraying with reused water (Nosedo)

Operating costs for the Nosedo wastewater treatment plant amount to €0.139/m3. The main component of operating costs is the cost of chemicals (30%), including peracetic acid used for disinfection. Other operating costs include labor (20%), energy (20%), sludge disposal (15%) and maintenance (15%).

The main feature of the Nosedo plant is the large volume of treated water that is reused for agricultural purposes.

The Nosedo wastewater treatment plant is one of the best examples of water reuse in Europe. The challenge was to guarantee the best conditions for water reuse. This is why the treated wastewater complies with European directives.

The plant is equipped with software for real-time optimization of process performance. It provides control data to optimize the entire wastewater system, including the sewer network and treatment plant, energy consumption, chemicals, as well as biological and hydraulic capacity improvement.

The farmers’ associations known as Consorzio Vettabbia comprise 84 member farms.

1.3. The Hermitage station (Reunion Island)

Figure 1.6.Map of Reunion Island (France)

Improving local management of water resources is one of Réunion’s fundamental challenges in terms of sustainable development.

The targets set are still based on supplying the population with adequate quality drinking water, as well as on efficient wastewater treatment and reuse of treated water for irrigation or industrial purposes.

For example, the rehabilitation program for the Hermitage wastewater treatment plant involved bringing the plant’s discharges up to standard, and doubling its treatment capacity from 12,500 to 25,000 P.E. in 2010.

1.3.1. Pollutant loads

The basic pollutant load data taken into account for tertiary treatment are defined by hydraulic load parameters.

1.3.1.1. Hydraulic load

The maximum hydraulic flow rate is 300 m3/h for:

6,500 m

3

/day for 22 h in dry weather;

14,000 m

3

for 47 h in wet weather.

1.3.1.2. Treatment targets

The system is designed to meet the requirements for water intended for irrigation and potentially for non-food industrial use.

The tertiary treatment process includes the following facilities:

a lift station;

a technical building with:

electrical room, reagent room, air and backwash filter equipment,

wash water tank,

sand filter and UV reactor,

venturi meter with discharge to existing drain,

a wastewater discharge station.

The tertiary treatment lift station is fed by gravity from refining lagoon No. 3. A 3-mm mesh strainer is placed on the station’s feed pipe to stop large particles and miscellaneous debris. This strainer is self-cleaning, thanks to a ramp equipped with nozzles for countercurrent injection of pressurized water. Pressurized water is drawn from the pumping station’s discharge manifold through a “tapped” pipe.

The self-cleaning strainer is cleaned by a pump connected directly to the storage tank. Four pumps (3 + 1 back-up) supply the tertiary treatment system in 100 m3/h flow steps. The start-up of one, two or three pumps is controlled by a level measurement on the infiltration lagoon.

The nominal flow rate of 300 m3/h is discharged through two in-line, selfcleaning pre-filters with a mesh size of 50 μm, each rated at 150 m3/h. Turbidity is measured downstream of the pre-filters, and a coagulant, such as ferric chloride, is injected at a configurable turbidity threshold.

Raw water and coagulant are mixed by an in-line static mixer. The pressurized sand filters are fed from a general feeder with pre-filtered and possibly pre-coagulated water.

1.3.2. Tertiary filtration

An in-line injection of ferric chloride upstream of the sand filters is therefore projected. Coagulation is triggered when the total suspended solids (TSS) concentration of the water pumped into lagoon No. 3 exceeds 25 mg.L−1. Injection of ferric chloride is triggered by a turbidity threshold in the water pumped into lagoon No. 3. In addition to reducing particle-bound phosphorus, ferric chloride injection also slightly reduces dissolved phosphorus precipitated by the iron salt. Ferric chloride is delivered in 1 m3 containers.

The coagulant is injected by a dosing pump (1 + 1 backup) into the main line, upstream of the static mixer. The static mixer, made up of helicoids, ensures turbulence for homogenization and good coagulation. Reagent injection is not continuous and depends on the quality of the water fed to the tertiary filters.

Tertiary filtration is carried out using six pressurized filters, fed by the water lift station of lagoon No. 3, after pre-filtration and possibly pre-coagulation. The filter layer is made up of 1.35 mm expanded clay media (Biodagene) resting on a strained floor.

1.3.2.1. Choice of filtration

The choice of particle size – 1.35 mm – and filter bed height – 2 m – offers the following advantages:

prevents rapid clogging of the surface filter, by favoring a higher layer height for TSS trapping;

prevents significantly reduced filtration cycles in the event of TSS peaks, and limits degradation of the filtered water;

prevents filtration speeds of 15 m.h

−1

.

Stable filtered water quality is also beneficial for UV disinfection.

The water to be treated is fed into the filters through a gully at the top, which has a dual role: intake of the water to be filtered and discharge of the wash water.

The filter media consists of a 2-m thick layer of Biodagene (Table 1.4). Beneath the filter layer is a 10-cm layer of gravel and a metal floor fitted with nozzles.

The floor ensures perfect homogeneity of fluid distribution within the filter mass, both during filtration itself and during washing operations.

The filtered water is discharged through a pipe at the bottom of the filter. This pipe also serves as a water inlet for filter washing. The design of the system allows simultaneous washing and filtration. Filters are washed in turn during or outside operating periods.

Washing is triggered by a timetable, clogging threshold or operator decision. Filter pressure loss is checked by measuring the difference in pressure between the filtered water inlet pipe and the filtered water outlet pipe (contact differential pressure gauge).

Filters are preferably washed at night, when the flow treated at the WWTP is reduced. This will limit the hydraulic impact on the plant.

1.3.2.2. Filter cleaning

The various washing operations take place automatically. A wash cycle comprises several distinct phases:

First phase: detasseling. Air is blown in at a rate of 50 Nm

3

.h

−1

.m

−2

for 1 min.

Second phase: air + water. Air is blown in at a rate of 50 Nm

3

.h

−1

.m

-2

combined with a countercurrent of water limited to 8 m

3

.h

−1

.m

−2

for 8 min.

Third phase: rinsing and evacuation of dirty water with water alone at a flow rate of 50 m

3

.h

−1

.m

−2

for 8 min.

Wash water is run through the same pipe as the filtered water outlet. Air is supplied through a pipe running under the floor. Wash water is supplied by a pump providing the required flow rate of 200 m3.h−1 for maximum manometric head.

The wash water is pumped into the 20 m3 filtered water tank and disinfected. Dirty water is then collected in a station equipped with two 60 m3.h−1 unitary drainage pumps (1 + 1 backup) discharging to the biological tank.

Table 1.4.Tertiary filtration dimensions

Parameters

Unit

Values

Total incoming flow (over 15 h)

m

3

.h

−1

300

Number of filters

u

6

Filtration rate on N filters

m.h

−1

13.2

Filtration rate on N

−

1

m.h

−1

15.8

Unit surface area

m

2

3.8

Unit diameter

m

2.2

ES Biodagene

mm

1.35

Height of material (gravel + Biodagene)

m

0.1 + 2.0

Minimum cycle time (TSS input 25 mg.L

−

1

)

h

24

1.3.3. UV disinfection

Figure 1.7.UV reactors and filters

The principle of disinfection by UV radiation has developed considerably over the last few decades for wastewater treatment, and it is considered a good alternative to chlorination. With UV radiation, disinfection is not accompanied by the formation of any reaction products with organic matter in the water. UV rays are light waves with wavelengths between 100 and 400 nm. Their germicidal power depends on the wavelength emitted. UVC between 200 and 280 nm is the most germicidal.

Low-pressure lamp technology was chosen for this installation. These have the advantage of emitting maximum radiation in the wavelength corresponding to the optimum germicidal band (254 nm):

long service life: 15,000 operating hours (12,000 guaranteed operating hours), 15,000 reported hours;

low-power consumption;

96% of the spectrum is emitted at 253.7 nm for maximum efficiency;

the applied dose is 400 J.m

−2

at the end of the lamp life.

Three lines (Figure 1.7), each equipped with a 100 m3.h−1 in-line low-pressure UV reactor, are installed downstream of the tertiary filtration unit. They are independent and can be isolated from one another. The system is controlled by an electrical cabinet, which switches on the lamps, operates them and counts up the operating hours, and is equipped with an alarm to indicate any malfunction.

The reactors (Table 1.5) feature automatic lamp cleaning by sweeping. The cleaning frequency is adjustable according to water quality and intensity measurement.

The UV reactors are as follows:

arranged horizontally to facilitate inspection and maintenance operations;

equipped with two draining and cleaning valves;

equipped with three mixers to homogenize effluent and disinfection.

In addition, turbidity is measured to assess the presence of suspended matter in the filtered water, which is known to reduce UV efficiency. The UV disinfection stage can be bypassed by a set of manual valves in the event of significant degradation of the filtered water.