BEST AVAILABLE TECHNOLOGIES FOR WATER REUSE AND RECYCLING.

NEEDED STEPS TO OBTAIN THE GENERAL IMPLEMENTATION OF WATER

REUSE.

ANA URKIAGA*/LIBE DE LAS FUENTES (*: person presenting the paper)

FUNDACIÓN GAIKER

Parque Tecnológico de Bizkaia

Edificio 202, ZAMUDIO (48170) BIZKAIA-SPAIN

Abstract

In this paper a review about water reuse currently situation is given. Different aspects as types of

applications and main constraints, treatment technologies, legislation and currently applied water

reuse projects have been considered. Special attention has been dedicated to the best available

technologies for these applications, focusing in membrane processes and disinfection processes (UV

and ozone). Wastewater recycling and reuse is a very emerging alternative to obtain water

resources. Its application depends on many different factors as for example legislative and political

issues, technical, economical, environmental and social issues so a suitable Water Management will

require to take into consideration all of these aspects.

Keywords

Water reuse; membrane processes; tertiary treatments; ozone; UV light

1. Introduction

The Second World Water Forum in The Hague in March 2000, showed very clearly to the world

public that Water will be one of the central issues of the 21st century of this globe, and the life of

billions of people will depend on the wise management of this resource. Water is an essential and

basic human need for urban, industrial and agricultural use and has to be considered as a limited

resource. In this sense, only 1% of the total water resources in the world can be considered as fresh

water and in 2025 nearly one-third of the population of developing countries, some 2.7 billion

people, will live in regions of severe water scarcity. They will have to reduce the amount of water

used in irrigation and transfer it to the domestic, industrial and environmental sector" [1].� Moreover,

water pollution by human interference, e.g. by industrial effluents, agricultural pollution or

domestic sewage will increase and the world's primary water supply will need to increase by 41% to

meet the needs of all sectors which will be largely due to the increase in the world population.

In this scenario, a unique and viable opportunity to augment traditional water supplies provides

water reclamation and reuse. Water reuse and recycling are the only solutions to close the loop

between water supply and wastewater disposal. Promising is the fact that since many years it is

feasible to treat wastewater to a high quality. Hence, wastewater could be regarded as a resource

that could be put to beneficial use rather than wasted; so in many parts of the world reclaimed water

is used as a water resource and water reuse is called the greatest challenge of the 21st century. Water

reuse accomplishes usually two fundamental functions: the treated effluent is used as a water

resource for beneficial purpose and the effluent is kept out of streams, lakes, and beaches: thus

reducing pollution of surface water and groundwater [2]. In addition to the economic savings due to

water reuse, valuable substances and heat recovery can be achieved by water recycling obtaining a

zero emission process.

Wastewater should be treated using very effective wastewater treatment technologies that guarantee

protecting public health and the environment and the industry demands. Among the most promising

technologies to achieve the mentioned objectives of zero emission, membrane technology

(membrane bioreactors, micro, ultra and nanofiltration and reverse osmosis) and advanced

oxidation technologies (ozone, UV light, PhotoFentonn,….) point up.

A common misconception is that reclaimed wastewater represents a low-cost new water supply.

This assumption is true only when wastewater reclamation facilities are conveniently located near

large agricultural or industrial users. Also it is true when no additional treatment is required beyond

the facilities from which reclaimed water is delivered. The conveyance and distribution systems for

reclaimed water represent the principal cost of most proposed water reuse projects.

2. Categories of water reuse.

During the planning and implementation of water reclamation and reuse, the reclaimed water

application will usually govern the type of wastewater treatment needed to protect public health and

the environment, and the degree of reliability required for each sequence of treatment process and

operations. Water reuse application, from a global perspective, have been development to replace or

increase water resources for specific applications depending of course on local water use standard.

Generally depend on water origin and treatment process; water reuse application can be divided in

seven categories:

1. Agricultural irrigation represents the largest current use of reclaimed water throughout the

world. This reuse category offers significant future opportunities for water reuse in both

industrialized countries and developing countries.

2. Landscape irrigation is the second largest user of reclaimed water in industrialized

countries and it includes the irrigation of parks; playgrounds; golf courses; freeway

medians; landscaped areas around commercial, office, and industrial developments; and

landscaped areas around residences. Many landscape irrigation projects involve dual

distribution systems, which consist of one distribution network for potable water and a

separate pipeline to transport reclaimed water.

3. Industrial activities represent the third major use of reclaimed water, primarily for cooling

and process needs. Cooling water creates the single largest industrial demand for water and

as such is the predominant industrial water reuse either for cooling towers or cooling ponds.

Industrial uses vary greatly and water quality requirements tend to be industry-specific. To

provide adequate water quality, supplemental treatment may be required beyond

conventional secondary wastewater treatment.

4. Groundwater recharge is the fourth largest application for water reuse, either via

spreading basins or direct injection to groundwater aquifers. Groundwater recharge includes

groundwater replenishment by assimilation and storage of reclaimed water in groundwater

aquifers, or establishing hydraulic barriers against salt-water intrusion in coastal areas.

5. Recreational and environmental uses constitute the fifth largest use of reclaimed water in

industrialized countries and involve non-potable uses related to land-based water features

such as the development of recreational lakes, marsh enhancement, and stream flow

augmentation. Reclaimed water impoundments can be incorporated into urban landscape

developments. Man-made lakes, golf course storage ponds and water traps can be supplied

with reclaimed water. Reclaimed water has been applied to wetlands for a variety of reasons

including: habitat creation, restoration and/or enhancement, provision for additional

treatment prior to discharge to receiving water, and provision for a wet weather disposal

alternative for reclaimed water.

6. Non-potable urban uses include fire protection, air conditioning, toilet flushing,

construction water, and flushing of sanitary sewers. Typically, for economic reasons, these

uses are incidental and depend on the proximity of the wastewater reclamation plant to the

point of use. In addition, the economic advantages of urban uses can be enhanced by

coupling with other ongoing reuse applications such as landscape irrigation.

7. Potable reuse is another water reuse opportunity, which could occur either by blending in

water supply storage reservoirs or, in the extreme, by direct input of highly treated

wastewater into the water distribution system. [3].

Water from recycling systems used in each one of the seven categories should fulfil four criteria:

hygienic safety, aesthetics, environmental tolerance and technical and economical feasibility.

3. Current applications and legislation

In Europe, most of the northern European countries have abundant water resources and they all give

priority to the protection of water quality. In these countries, the need for extra supply through the

reuse of treated wastewater is not considered as a major issue, but on the other hand, the protection

of the receiving environment is considered important. However, industry is generally encouraged to

recycle water and to reuse recycled wastewater. The situation is different in the southern European

countries, where the additional resources brought by wastewater reuse can bring significant

advantages to agriculture (e.g. crop irrigation) and tourism (e.g. golf course irrigation). Some of

water recycling and reuse technologies have been practised in Mediterranean region since ancient

civilisations but nowadays wastewater recycling and reuse is increasingly integrated in the planning

and development of water resources.

One of the most important aspects that contribute to development and implementation of water

recycling and reuse projects is legislation. In Europe there is not a specific legislation in this

subject, so some countries or regions are implementing different guidelines. Table 1 summarises the

level of legislation in different countries. This is still a pending issue that shall be solved.

4. Water reuse- treatment and water quality.

Wastewater reclamation and reuse have become significant elements in water resources planning

and management, particularly in arid and semiarid regions. Proper and integrated planning the reuse

of reclaimed water may provide sufficient flexibility to respond the short-term needs as well as to

increase the long-term reliability of water supply. Moreover, water quality criteria, economic

analyses and project management, in the context of water resources, are essential components in the

implementation of any water reuse project. The essential foundation for successful implementation

of such a project is the capability of producing water of a desired quality to provide adequate public

health protection and meet the environmental and socio-economic goals than can be practically

achieved at given time. There are many methods of water treatment. Different methods can be

employed to renovate effluent for utilisation for agricultural, industrial, environmental and domestic

applications. Direct human consumption of the treated effluent, although it is possible to obtain,

will be very rarely applied due to psychological and probably religious reasons.

Upgraded wastewater use in various application categories shall specify the following conditions:

− Reuse water shall be safe for its intended use and shall not jeopardise the safety of the

product through the introduction of chemical, microbiological or physical contaminants in

amounts that represent a health risk to the consumer;

− Reuse water should not adversely affect the quality (flavour, colour, texture) of the product;

− Reuse water intended for incorporation into a food product shall at least meet the

microbiological and, as deemed necessary, chemical specification for potable water. In

certain cases physical specifications may be appropriate;

− Reuse water shall be subjected to on going monitoring and testing to ensure its safety and

quality. The frequency of monitoring and testing are dictated by the source of the water or

its prior condition and the intended reuse of the water; more critical applications normally

require greater levels of reconditioning than less critical uses;

− The water treatment system(s) chosen should be such that it will provide the level of

reconditioning appropriate for the intended water reuse;

− Proper maintenance of water reconditioning systems is critical;

− Treatment of water must be undertaken with knowledge of the types of contaminants the

water may have acquired from its previous use; and

− Container cooling water should be sanitised (e.g., chlorine) because there is always the

possibility that leakage could contaminate product.

The choice of the right wastewater treatment technologies is the most important thing in planning

the water reuse system because they are the important way of decreasing or eliminating the

environmental risk. The environmental risk is connected with the contamination that can be finding

in the upgraded wastewater and generally risk can be divided into chemical and microbiological.

The fundamental purpose of water treatment is to protect the consumer from pathogens and from

impurities in the water that may be injurious to human health or offensive. Where appropriate,

treatment should also remove impurities which, although not harmful to human health, may make

the water unappealing, damage pipes, plant or other items with which the water may come into

contact, or render operation more difficult or costly [4]. These purposes are achieved, by

introducing successive barriers, such as coagulation, sedimentation, filtration and advanced

treatments, to remove pathogens and impurities. The final barrier is often disinfection. Table 2

provides an overview of water treatment technologies and their applications.

In many parts of the world, agricultural irrigation using reclaimed water has been practised for

many centuries. Landscape irrigation of golf courses, parks and playgrounds has been successfully

implemented in many urban areas for over 30 years. Salt management in irrigated croplands may

require special attention in many arid and semi-arid regions. Main treatment trains utilised for

agricultural wastewater reuse including the obtained quality depending on the use is represented in

Figure 1. Beyond irrigation and non-potable urban reuse, indirect or direct potable reuse need

careful evaluation and close public scrutiny. It is obvious from public health and acceptance

standpoints that non–potable water reuse options must be exhaustively explored prior to any notion

of indirect or direct potable reuse.

Among the different treatments used to regenerate wastewater we can divide them into extensive

and intensive treatments (Table 3). As extensive treatments, lagooning, wetlands, soil aquifer

treatment and infiltration-percolation stand out. Usually extensive treatments are located in non-

developed countries [5]. These types of treatments are cheaper than the intensive ones, they usually

require longer times and great zones of land and they do not require as much technical knowledge

(experts). On the other hand, the quality of the reclaimed water is not as high as in the case of the

intensive treatments and moreover different aspects as for example climate (temperature, winds) or

soil’s composition will determine the obtained yield.

Advanced technologies are usually utilised in developed countries where every day more

restringing requirements and legislation is implemented. In this sense, the full application in Europe

of the 91/271/EU Directive, which obliges to the European countries to have a suitable treatment

and depollution system of their urban wastewaters before the end of the 2005, will contribute to

count with a very important source of an alternative water resource with a high quality. In Europe

usually urban wastewaters are treated by a physico-chemical treatment followed by a biological

treatment and to finish in some cases a tertiary system. It is for this reason that in this section we

will focus our work in the intensive treatments and more specifically in membrane processes

(micro, ultra and nanofiltration, reverse osmosis and membrane bioreactors) and advanced

oxidation processes (ozone and UV light).

In the case of membrane processes, they are separative processes. The mechanism of separation is a

physical one. Among advanced treatment processes, membrane applications have clearly emerged

as a promising alternative to conventional, advanced physical-chemical treatment, which ususally

includes chemical coagulation, floculation and granular-medium filtration. Membrane processes are

finding their way to cost-comparable applications for removal of microorganisms, trace organic

substances, ions and dissolved solids. There are different membrane materials and configurations

with different characteristics. The utilisation of one or other process will depends on the range of

the sizes or molecular weights of the substances or compounds to remove. While membranes have

multiple applications, the useful life of a membrane depends on conditions that can cause fouling,

scaling or chemical interactions. The success of membrane processes is highly dependent on pre-

treatment.

Membrane bioreactors (using micro or ultrafiltration membranes) can be considered as very

promising processes and their implementation is currently being increased. These systems obtain

best yields than conventional activated sludge systems, they can operate with higher solids loads so

they can reduce the treatment times, or work with higher effluent flows and they do not require so

much space as conventional biological systems. Due to these advantages their implementation is

being very extensive, mainly in tourist zones where the wastewater flows suffer great fluctuations

along the year, and in islands where there are land problems. In this sense, the use of membrane

bioreactors in many buildings in Japan in order to treat and reuse wastewater for irrigation and toilet

flushing is very common. The main companies that commercialise this type of bioreactors are

Zenon, Kubota and Mitsubisi.

Micro and ultrafiltration are used for both industrial and non-industrial applications of water reuse.

They can be utilised as tertiary treatments due to microbiological retention (< 0.45 µm). As physical

barriers they can guarantee the suitable microbiological quality without eliminating other valuable

compounds as for example nutrients or fertilisers. In the same way, in the industry they can be used

for process water recycling, for example in the case of rinsing baths in order to recycle or recover

valuable substances (raw material, chemical agents, detergents, heat,…). These treatments can be

used as single processes or as pre-treatment for other processes as for example nanofiltration or

reverse osmosis. Reverse osmosis as final step will produce regenerated water of a very high

quality. Reverse osmosis has been extensively used for seawater desalination but some authors have

verified that reverse osmosis from wastewater is more cost effective than from seawater [6]. The

improvements in the technology and the increase of reverse osmosis utilisation have contributed to

a very important decrease of the cost of this process.

On the other hand, advanced oxidation processes, and more specially ozone and UV light are

increasing their application as disinfection steps. Disinfection is an essential component of many

wastewater reclamation and reuse treatment systems that has as objective to inactivate or destroy

pathogen organisms. Although the most common method of wastewater disinfection is chlorination,

the potential toxicity of chlorination by-products makes this process less atractive. UV irradiation

has emerged in France and the USA as a viable alternative to chlorination with a comparable and

often more effective disinfection efficiency for control of viruses and bacteria. As can be observed

in the Table 4 where different technologies are compared, UV irradiation as a highly efficient and

cost competitive advanced disinfection process. The higher cost of ozone is outbalanced by the

better water quality and virus removal. Therefore, ozone may be recommended as a viable technical

solution for large scale plants, specially when viruses and/or protozoa cysts are targeted [7].

Moreover, disinfection, these single treatments or combination of treatments (as for example

UV+H2O2, ozone+H2O2, UV+ozone,…) can oxidise different micropollutant compounds as for

example endocrine disruptors, solvents, etc., obtaining a carbon organic reduction of the treated

water.

The costs of these types of processes have been estimated in 0.8-1.6 €/kg ozone for ozone operation

and production costs or 0.05-0.1 €/m3 of treated water. The costs for the same system with UV

would be of 0.01 €/m3.

5. Examples of water reuse

In this section a brief analysis of different implemented water reuse projects will be given. Although

different water reuse applications will be analysed, we will focus the study on the use of advanced

technologies (especially membrane and disinfection (UV and ozone) processes) for water

regeneration for industrial and non-industrial (irrigation, marsh enhancement, toilet flushing,…)

applications.

• NON INDUSTRIAL WATER REUSE

Vitoria: wastewater reuse for irrigation (Spain). In the Spanish city of Vitoria-Gasteiz a program

for the integral wastewater reuse is being carried out [8]. The total amount of wastewater in this city

is of 45 Hm3/year. The treatment for water regeneration consists on a biological treatment and an

ulterior tertiary one (coagulation, filtration and disinfection with Cl2). The treated flow is 400 l/s

and the regenerated water is applied for agricultural irrigation (60 % of the produced wastewater). A

final step by reverse osmosis is applied. The obtained water has a very high quality (T-22 type) and

it would be susceptible of application for potable uses. The total estimated cost of the regenerated

water, including the system repayment, was of 0.057 €/m3 (0.18 €/m3 in the case of using a final

reverse osmosis step). In Spain there are a very special concern about water resources. In this sense

in the “Plan Hidrológico Nacional” (Spanish Hydrological Plan) it is planned that for the year 2012,

the 3% of the Spanish Water Demand will be supplied by reclaimed water. This means that the

actual water reuse will be increased by 4 times, as the current reclaimed water in Spain (2001) was

only the 0.7 % (= 260 Hm3/year) of the national water demand. The distribution of the total water

reuse by different Spanish zones can be observed in the Table 5.

Almería: wastewater reuse for irrigation (Spain). The Almería province is an arid region of the

southern Spain where the main activity is irrigated greenhouse horticulture (22,000 ha) followed by

tourism. A water reuse plant with a capacity of 32,000 m3/d for irrigation of 3,000 ha has been

running since 1997. The wastewater treatment train includes activated sludge, sand filtration and

ozonation. Moreover the socio-technical economic benefits of the project, the impact of the

environment has been crucial with improvement of the littoral bathing conditions and limitation of

saline intrusion of the aquifers.

Valencia: land irrigation and marsh enhancement (Spain). A new reuse plant is being implemented

in Valencia (Pinedo II) with two different treatments, one with phosphorous removal for marsh

enhancement (31 Hm3/year) and the other one with no phosphorous removal (nutrients are

preferable) for agricultural irrigation (93 Hm3/year). As can be observed sometimes the best

alternative is not a unique application and treatment, but two or more treatments for different

applications. The treatment for application in marsh enhancement is the following one: physico

chemical (phosphorous removal)+sand filtration+ disinfection (UV). The installed UV system with

a disinfecting capacity of 15,000 m3/h will be the biggest UV installation in Spain and the third one

in Europe. The other two ones are located in Dublin (39,000 m3/h) and Edinburg (22,000 m3/h)

respectively.

Sooke (British Columbia): toilet flushing and garden irrigation (Canada). In the bed and breakfast

of Sooke Harbour House all grey water and black water is treated and recycled for toilet and urinal

flushing, and the excess of the regenerated wastewater is used in a garden drip irrigation system.

The design capacity of the system is 22,700 L/day. The effluent from a bio-reactor is treated by a

hollow fibre membrane filter, followed by a granulated activated carbon filter, ultraviolet

disinfection, and storage. If storage is full, the carbon filter is by-passed, and excess wastewater is

discharged to the irrigation system. The capital cost of the system-including permissions, design,

construction, and commissioning has been of $320,000. The total annual costs of power, operations

management, and monitoring have been estimated as $19,100, plus 4 hours per week of on-site

labour.

• INDUSTRIAL REUSE

Power station boiler feed. In Australia, recycled water from the Dora Creek sewage treatment

works is pumped to the 2,640 megawatt Eraring Power Station at Lake Macquarie, about 100 km

north of Sydney. There it is further treated by microfiltration and reverse osmosis to produce a

water of potable grade which is then further treated in the existing demineralisation plant to produce

purified water which is used as boiler feed to provide steam for the power station turbines. This

recycled water replaces 1.2 Mm3/yr of potable water previously supplied from the town water

supply system [9]. The total construction cost for the plant was less than A$6,000,000, whereas the

production cost reached A$ 0,126. In 99/00, the total savings reached A$ 3 million and the expected

pay back period of 7-8 is 7-8 years.

Oil refining. In Australia, a 14,000 m3/d dual membrane water reclamation plant has been installed

at the Luggage Point sewage treatment plant in Brisbane to supply process water to the BP oil

refinery [10].

Semi-conductor manufacture. The Singapore Public Utilities Board has installed since February

2003 the Singapore NEW Water project, with a capacity of a 72,000 m3/d. A dual membrane

process using microfiltration and reverse osmosis followed by ultraviolet light filtration has been

used to obtain regenerated water of high purity utilised for high technology and semiconductor

industries [11].

Piaggio V.E. factory, producing scooters and motorbikes. In this factory located in Pontedera (Italy)

a feasibility study has been carried out in order to reuse both urban and industrial wastewater to be

applied in this factory instead of the currently used well water [12]. The evaluated wastewater

treatment was the following one moreover the usual wastewater treatment (physico-chemical and

biological treatments): sedimentation, sand filtration, (ozone and activated carbon filtration or

ultrafiltration) and reverse osmosis and air stripping. The first method (ozone plus activated carbon)

is more effective at reducing chemical oxygen demand (COD) whereas the second method

(ultrafiltration) is more effective in removing bacteria. Nonetheless, both methods deliver water for

re-use of a quality comparable with or better than that of well-water. In principle, the reverse

osmosis permeate from either process could be re-used in all production phases at the industrial

plant. However, the method base upon oxidation with ozone followed by activated carbon filtration

is preferred, because, the process is simpler and continuous. The economic analysis of this process

gives an estimated cost of Euro 0.55 per m3 for treated water. This compares favorably with other

treatment processes and with the cost of other forms of water supply, which are projected to

increase.

On the other hand, [13] published a paper about feasibility of membrane bioreactor processes

(MBR) for water reclamation. Recent studies at Aqua 2000 Research Centre (San Diego) and the

Water Factory 21 in California have confirmed that membrane filtration is the most cost-effective

and reliable treatment process for preparing treated wastewater for the desalting process. Since

membrane filtration is now required as pre-treatment to desalting, the economics shift to make the

MBR process attractive for treatment of domestic sewage. The preliminary cost evaluation has

shown that the MBR process is cost competitive (total cost US$ 2.15/1000 gal) with other

conventional wastewater treatment processes, as oxidation ditch (total cost US$ 2.40/1000 gal) or

conventional activated sludge treatment (total cost US$ 2.38/1000 gal)

Moreover two successful applications of ultrafiltration (UF) and reverse osmosis (RO) membrane

technology used to reclaim water, and to reduce waste water discharge costs have been described

[14]. The first case covers oily wastewater treatment at a major aluminium beverage can

manufacturing plant. The second case describes treatment of wastewater from a multi-plating bath

section of a major wheelchair manufacturing facility.

6. Conclusions

Wastewater recycling and reuse is a very emerging alternative to obtain water resources. Its

application depends on many different factors as for example legislative and political issues,

technical, economical, environmental and social issues. Although there are currently different

countries with specific legislation in this subject, the approval of wastewater reuse legislations in

more countries as well as a unique European legislation in this sense will increase the utilisation of

this alternative water resource. Moreover political decisions will have to be taken in order to fund,

subsidise or promote regenerated water use. Different educational and social campaigns will have

also to be carried out in order to explain to the public opinion (final users) the different advantages

and constraints of wastewater reuse to promote its use.

Although the most extended application of regenerated water is for irrigation purposes, more

restrictive legislations and other applications where a higher quality of the reclaimed water is

needed are promoting the use of different intensive treatments as for example membrane processes

and oxidation processes.

The use of water recycling and reuse in the industry is usually easier to implement because they do

not usually have as many social constraints as other applications (irrigation, aquifer recharge,…)

and each industry knows exactly which are the requirements that this reclaimed water must fulfil.

Some of the most extended uses of water reuse in the industry are the following ones: cooling,

process water, to feed boilers,… For boilers and cooling reverse osmosis is the most used treatment

in order to avoid incrustations. Disinfection treatments (UV, Ozone) are also used in order to

guarantee the suitable microbiological quality. Membrane processes, as separative processes, are

preferable in those cases where some valuable material wants to be recycled, as for example rinsing

baths where acids, alkalis or detergents want to be recycled. On the other hand, advanced oxidation

processes (UV, UV+H2O2, ozone,…) as destructive processes are preferable when for example

organic micropollutants as for example pesticides, plasticizers or other types of endocrine disruptors

want to be eliminated.

In the case of non-industrial applications of wastewater reuse, membrane processes and advanced

oxidation processes are also very emerging technologies, and not only as tertiary or quaternary

treatments but for other purposes. In this sense, membrane bioreactors permit increasing the yield of

conventional activated sludge treatments, and working with higher influent flows or needing lower

space requirements as they operate with higher concentrations of suspended solids. These

characteristics are given rise to their implementation in tourist zones and places with land problems

(as for example islands). In this sense in Japan there is an extensive use of membrane bioreactors in

each building for wastewater treatment and water reuse for example for toilet flushing.

Micro or ultrafiltration processes only or followed by nanofiltration or reverse osmosis can

guarantee reclaimed water of high quality and as they are physical barriers they can guarantee a

suitable microbiological quality. Reverse osmosis has been utilised for example in aquifer

recharging moreover for water desalting.

Among the oxidation processes, UV light and ozone treatments are increasing and chlorine

utilisation is decreasing due to the possibility of formation of organochloride compounds. UV light

use has been recognised by different American States as the best process to obtain disinfected

reclaimed water. Both treatments are cost effective ones, although it looks that ozone is preferable

for great installations. In opinion of some authors UV light is better for microbial disinfection and

ozone for compounds removal (Total Organic Carbon decrease).

To finish, in this paper some different implemented wastewater reuse projects for industrial and

non-industrial applications have been described.

Acknowledgements

Some of the information showed in this paper will be utilised in the development of the European

project “Integrated Concepts for Reuse of Upgraded Wastewater”, Contract number: EVK1-CT-

2002-00130 funded by the European Commission.

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Illustrations and Tables

Table 1. Legislation for treated wastewater reuse.

Country Practices Existence of legislation Contemplating legislation No legislation at all

Albania �

Algeria �(a)

Australia �

Austria �

Belgium �

Bosnia andHerzegovina

�

Croatia �

Cyprus �

Denmark �

Egypt �(a)

Finland �

France �

Germany �

Greece �(b)

Ireland �

Israel �

Italy �

Lebanon �

Luxembourg �

Lybia �

Malta �

Monaco �

Morocco �

Portugal �

Slovenia �

Spain �(c)

Sweden �

Syria �

The Netherlands �

Tunisia �

Turkey �

United Kingdom �

USA �

(a) Programme-strategy(b) Under the form of sanitary regulation(c) In some regions of Spain (Balearic, Andalucia, Canary islands, Catalonia)

Table 2. Overview of representative unit processes and operations used in water reclamation.

Process Description Application

Solid/liquid separation

Sedimentation

Filtration

Gravity sedimentation ofparticulate matter, chemical flock,and precipitates from suspensionby gravity settling.

Particle removal by passing waterthrough sand or other porousmedium.

Removal of particles from turbidwater those are larger than 30µm.

Removal of particles from waterthose are larger than about 3 µm.Frequently used aftersedimentation orcoagulation/flocculation

Biological Treatment

(Wastewater)

Aerobic biologicalTreatment

Oxidation pond

Biological nutrientremoval

Waste stabilization ponds

Biological metabolism ofwastewater by microorganisms inan aeration basin or biofilmprocess

Ponds up to one metre in depth formixing and sunlight penetration.

Combination of aerobic, anoxic,and anaerobic processes tooptimise conversion of organicand ammonia nitrogen tomolecular nitrogen (N2) andremoval of phosphorus.

Pond system consisting ofanaerobic, facultative andmaturation ponds linked in seriesto increase retention time.

Removal of dissolved andsuspended organic matter fromwastewater.

Reduction of suspended solids,BOD, pathogenic bacteria, andammonia from wastewater.

Reduction of nutrient content ofreclaimed water.

Reduction of suspended solids,BOD, pathogenic bacteria, andammonia from wastewater.Facilitates water reuse forirrigation and aquaculture.

Disinfection The inactivation of pathogenicorganisms using oxidizingchemicals, ultraviolet light, causticchemicals, heat, or physicalseparation processes (e.g.membranes).

Protection of public health byremoval of pathogenic organisms.

Advanced treatment

Activated Carbon

Air stripping

Ion exchange

Process by which contaminants arephysically adsorbed onto thesurface of activated carbon.Transfer of ammonia and othervolatile components from water toair.

Exchange of ions between an

Removal of hydrophobic organiccompounds.

Removal of ammonia and somevolatile organics from water

Effective for removal of cationssuch as calcium, magnesium,

Chemical coagulationand precipitation

Lime treatment

Membrane filtration

Reverse osmosis

exchange resin and water using aflow through reactor.

Use of aluminium or iron salts,polyelectrolytes, and/or ozone topromote destabilization ofcolloidal particles from reclaimedwater and precipitation ofphosphorus.The use of lime to precipitatecations and metals from solution.

Microfiltration, nanofiltration,ultrafiltration

Membrane system to separate ionsfrom solution based on reversingosmotic pressure differentials.

iron, ammonium, and anions suchas nitrate.

Formation of phosphorusprecipitates and flocculation ofparticles for removal bysedimentation and filtration.

Used to reduce scale-formingpotential of water, precipitatephosphorus, and modify pH.

Removal of particles andmicroorganisms from water.

Removal of dissolved salts andminerals from solution; alsoeffective for pathogen removal.

Figure 1. Main treatment trains for agricultural wastewater reuse.

Pretreatment Coagulation

Flocculation

Disinfection

Cl, UV, O3

Raw

sewage

Anaerobic

ponds

Facultative

stabilisation ponds

Maturation

ponds

Raw

sewage

Pretreatment Primary

settling

Disinfection

Cl, UV, O3

Raw

sewage Activated

sludge

Disin

fectionCl, UV,

O3

Raw

sewage

Pre

treatment

Primary

settling

Activated

sludgeFiltrationClarifier

Infiltration

percolation

Pasture, cooked vegetables,

fruits

Vegetables eaten raw

Canaries island (<2,2

TC/100 ml)

Israel (2,2 FC/100 ml)

California (<2,2 FC/100 ml)

Florida (<1 FC/100 ml)

Arizona (<1 FC/100 ml)

virus <1PFU/40L)

Industrial crops, forest

Pasture, cooked vegetables,

fruits

Australia (<3000 and <750

FC/100 ml)

California (<23 TC/100 ml)

EPA, US (<200 FC/100 ml)

South Africa (<1000 FC/100

ml)

Catalonia (<1000 FC/100 ml)

Industrial crops, forest

Example: Mexico City (45 m3/s)

100% of irrigation needs

(WHO: <1 helm eg/L;

<1000FC/100 ml)

Industrial crops, forest

Israel (60 mg BOD/L; 50

mgSS/L)

Table 3. Recommended treatment schemes as a function of wastewater reuse applications.

Type of reuse application Extensive treatment Intensive treatment1. Irrigation of restricted crops E.1. Stabilisation ponds in

series or aerated lagoons;wetlands; infiltration -percolation

I.1. Secondary treatment byactivated sludge or tricklingfilters with pr withoutdisinfection

2. Irrigation of unrestrictedcrops, vegetables eaten raw

E.2. Idem as E.1. with polishingsteps and storage reservoirs

I.2. Idem as I.1. with tertiaryfiltration and disinfection

3. Urban uses for irrigation ofparks, sport fields, golf courses

E.3. Idem as E.2. I.3. Idem as I.2. filtration in thecase of unrestricted publicaccess

4. Groundwater recharge foragricultural irrigation

E.4. Idem as E.2. completed bysoil-aquifer treatment

I.4. Idem as I.2. with nutrientremoval (when necessary)

5. Dual distribution for toiletflushing

E.5. Not applicable I.5. Idem as I.3. with activatedcarbon (when necessary) ormembrane bioreactors anddisinfection

6. Indirect and direct potableuse

E.6. Not applicable I.6. Secondary, tertiary andquaternary treatment, includingactivated carbon, membranefiltration (included reverseosmosis) and advanceddisinfection

Table 4. Comparison of different disinfection treatments.

Characteristics/Criteria

Chlorination/

dechlorination

UV Ozone MF UF NF

Safety + +++ ++ +++ +++ +++

Bacteriaremoval

++ ++ ++ ++ +++ +++

Virus removal + + ++ + +++ +++

Protozoaremoval

- - ++ +++ +++ +++

Bacterialregrowth

+ + + - - -

Residualtoxicity

+++ - + - - -

By-products +++ - + - - -

Operating costs + + ++ +++ +++ +++

Investmentcosts

++ ++ +++ +++ +++ +++

-: none; +: low; ++: middle; +++: high

Table 5. Main actions of water reuse in Spain

CITY TYPE OF TERTIARYTREATMENT

WATERREUSE FLOW

(Hm3/year)

USE OF THERECLAIMED WATER

Costa del SolOccidental

Sand filtration and ozone 5.5 Golf courses, municipaluses

Vitoria Physico chemical+sandfiltration+chlorination

5,5 Agricultural irrigation

Chiclana sand filtration+chlorination 2.2 Golf courses, municipaluses

Almería

(BajoAndarax)

(Comarca dePoniente)

Sand filtration+disinfection(ozone)

Reverse osmosis

10.0

9.7

Agricultural irrigation

Agricultural irrigationand aquifer injection(salt water intrusionbarrier)

Alicante Secondary treatment(wetlands) (tertiarytreatment only for waterirrigation )

Physico chemical+microfiltration+disinfection

10.6

0.75

Agricultural and golfcourses irrigation (0,9Hm3/year)

Irrigation of municipalparks

Valencia Physico chemical(phosphorousremoval)+sand filtration+disinfection (UV)

(non phosphorous removalfor agricultural irrigation)

31

93

Marsh enhancement(Albufera)

Agricultural irrigation

Murcia Only secondary treatment 11.1 Agricultural irrigation

Cartagena Only secondary treatment(wetlands)

6.5 Agricultural irrigation

Mallorca Only tertiary treatment fora reduced flow of 3,65Hm3/year

24.5 Agricultural irrigation

Tenerife Filtration+chlorination 6.0 Agricultural irrigation

Villaseca-Salou

Physico chemical+filtration+chlorination

6.1 Agricultural irrigation,municipal andrecreational uses