1

Laundry wastewater treatment using coagulation and membrane filtration

S. Šostar Turk1, I. Petrinić1,*, M. Simonič2

1Faculty for Mechanical Engineering, Institute for Textile, University of Maribor, P.O. Box 224, Smetanova

ulica 17, SI-2000 Maribor, Slovenia 2Faculty of chemistry and Chemical Engineering, University of Maribor, P.O. Box 219, Smetanova ulica 17, SI-

2000 Maribor, Slovenia

Abstract

This paper presents the results obtained from laundry wastewater treatment using

conventional methods namely precipitation/coagulation and the flocculation process with

adsorption on granular-activated carbon (GAC) and an alternative method, membrane

filtrations, namely ultrafiltration (UF) and reverse osmosis (RO). Chemical analyses showed

that parameter values of untreated wastewater like temperature, pH, sediment substances, total

nitrogen and phosphorous, COD, BOD5, and the amount of anion surfactants had being

exceeded in regard to Slovenian regulation. These regulations can be used as requirements for

wastewater reuse and make treated wastewater an available source for the existing water

supply.

The study of conventional treatment was based on a flocculation with Al2 (SO4)3x18 H2O and

adsorption on GAC. Membrane filtrations were studied on a pilot wastewater treatment plant:

ultrafiltration (UF) and reverse osmosis (RO) units. The membranes used in this experiment

were ceramic UF membrane and spiral wounded – polyethersulfone – RO membranes. The

quality of the wastewater was improved by both methods and the specifications of a

concentration limit for emission into water were confirmed. The disadvantage of GAC is that

there is no possibility of any kind of selection, which is essential for recycling and re-use,

while permeate coming from RO met the required regulation as well as requirements for

reusing in washing process. However, the economical analyses showed that the membrane

filtrations are more expensive compared to the GAC treatment process.

Keywords: laundry wastewater, chemical analyses, coagulation, membrane filtration, pilot

plant

* Corresponding author. Tel.: +386-2-220-7906; fax: +386-2-220-7990.

E-mail address: irena.petrinic@uni-mb.si (I.Petrinic).

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1. Introduction

Laundering processes, including water-washing processes and dual-phase washing, use

significant amounts of water. The cleanliness obtained when laundering is the result of

synergistic actions between the so-called Sinner parameters, these being mechanical energy,

chemical energy, thermal energy and time. These factors have to perform a simple separation

process in which soil is removed from a textile substrate (Warmoeskerken et al., 2002).

Bleach, water softeners and surfactants are the most important ingredients of laundry

detergents (Jakobi and Löhr, 1987). The concentration, type, and amounts of chemicals added

during the water-washing process depend on the type of cleaned items, and the degree to

which the items are soiled. Surfactants have the unique ability to remove both water-soluble

and non-water-soluble soils. One end of the surfactant molecule (the lipophilic or oil-loving

end) penetrates oily soils, whilst the opposite end of the molecule (the hydrophilic or water-

loving end) solubilizes the oils. This action loosens soils and disperses them in the water.

As environmental regulations tighten, concern increases about reducing the surfactant

concentration in effluent streams. It has been reported that the wastewater from a laundry,

where very dirty items are being washed, contains mineral oils, heavy metals and dangerous

substances that have COD values of 1200 up to 20 000 mg O2/l. The wastewater from

hospitals contains fat, the remains of food, blood and urine that have COD values of 400 up to

1200 mg O2/l. Laundries washing items from households and hotels, pollute water with COD

values from 600 to 2500 mg O2/l (Gosolits et al., 1999).

The most widely used systems for laundry wastewater treatment are conventional methods;

such as precipitation/coagulation and flocculation, sedimentation and filtration or combination

of these. Coagulation and flocculation aids are usually added to facilitate the formation of

large agglomerated particles (EPA, 2000). These systems remove colour insufficiently and are

clearly ineffective in decolourising laundry effluents, even when mixed and treated together

with sewage. Adsorption on the granular activated carbon (GAC) after the process of

flocculation can improve the treatment due to the large surface area that allows carbon to

adsorb a wide range of compounds. However, the level of colour removal depends on the dye

type (Faria, 2004).

Membrane processes offer a number of advantages over conventional water and wastewater

treatment processes including fulfilment of higher standards, reducing environmental impact

of effluents, land requirements and the possibility to use mobile treatment units.

Bhattacharyya et al. (1987) showed that the recycled ultrafiltrate from laundry and shower

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wastewater could be used as non-potable water. Ahn et al. (1999) reported that physically

filtered wastewater with various types of ceramic membranes from a resort complex can be

used effectively in creating recycled wastewater for such secondary purposes. Industrial

laundries have a variety of opportunities to recycle/reuse water at their facilities (EPA, 2000).

The main problems in practical applications of membrane filtrations are the reduction of

permeate flux with time, caused by the accumulation of feed components in the pores and on

the membrane surface (Mulder, 2000). Membrane fouling involves specific interaction

between the membrane or adsorbed solutes and other solutes in the feed stream and it is

characterized by an irreversible and time dependent decline in flux. Membrane needs proper

feed pre-treatment and a well-developed cleaning protocol because fouling can directly

influence on membrane lifecycle costs. In a wastewater treatment, polymer membranes have

wider usage due to their lower price. However, there are limitations in chemical, thermal and

mechanical stability. For this reason, when treating wastewater from industrial laundry, the

ceramic UF membrane was used as a pre-treatment stage for RO membrane.

The authors performed several experimental investigations concerning laundry wastewater

purification (Petrinic et al., 2002; Petrinic et al., 2003). This paper includes the results of

laboratory trials on wastewater using:

• conventional methods; precipitation/coagulation, flocculation and adsorption on active

carbon and

• membrane filtrations; UF and RO processes.

Based on recommendation and good results achieved when treating the wastewater from

metal, textile and electronic component industry, the membrane system described in the paper

was introduced to laundry industry in Slovenia. The investments and operating costs of

membrane filtrations were estimated and compared to those of GAC.

2. Materials and methods

2.1. Laundry wastewater description

The composition of the laundry wastewater is shown in Table 1.

Table 1

The measured parameters for the laundry wastewater were chosen according to the Slovenian

regulation called ”Decree of substance emission during removal of wastewater from laundry

and dry cleaning” (Official Gazette of the Republic of Slovenia, 2002) as well as their

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concentration limits of emission into water. These regulations meet the requirements for

wastewater reclamation and reuse and make it an available source for the existing water

supply.

It can be seen that the values of some parameters exceeded the outflow limit value in the

water. The exceeded parameters were: temperature, pH, sediment substances, total nitrogen

and phosphorous, COD and BOD5, and the amount of anion surfactant. It is known, that the

presence of anionic surfactant, builder and other oil substances in the wastewater could

increase the COD concentration (Seo et al., 2001). The washing flow was 200 L/h, eight

hour’s per day from Monday to Friday. The wastewater was coloured (green). Thus, the

wastewater treatment was needed to fulfil the regulation standards.

2.2. The washing process

Wastewater was taken from the laundry that washes hospital clothes using a tunnel washer

(type Senking, Jensen Group, Denmark). Tunnel washer is shown in Fig. 1 and consists of 12

modules. The laundry items pass automatically from one module to the next. The effluent was

collected from the third cell and used as feed. Water consumption for the preach and main

wash was 5 l/kg (cells 1-9) and for rinsing process, 8 l/kg (cells 9-12).

Fig. 1

2.3. Description of conventional plant

Water was flocculated with 5 mg/l of Al3+ added as Al2 (SO4)3x18 H2O. After 20 min the

water was filtered through silicic sand (Puconci, Slovenia) in a column with a diameter of 3.2

cm, the height of the sand layer was 1 m, the velocity of filtration was 10 m/h, the granulation

of sand grains was 0.5 -2 mm and the contact time was 6 min. The filtrate was adsorbed on

GAC in a column, with a diameter of 3.2 cm, the height of the GAC layer was 1 m, the

velocity of filtration was 5 m/h, the granulation of GAC was 1 mm and the contact time was

12 min. The GAC (type “Chemviron F-400”, Belgium) made from selected grades of coal to

produce a high-density, durable granular carbon product with high internal surface area up to

1200 m2/g .

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2.4. Description of the membrane pilot plant

UF and RO trials were carried out on a pilot scale. For UF a tubular module with ceramic

membrane was used. The membrane was 25.4 mm in diameter and 900 mm in length. This

membrane is a multi-channel membrane with an active surface layers made of Al2O3, TiO2

and ZrO2. It has a filtrating surface area of 0.13 m2. The nominal molecular cut-off size of the

membrane was from 20 – 400 kD (nominal pore diameter of 0.05 micron). Figures 2 and 3

show the test equipment.

The wastewater was poured into storage tank 1 from where it was pumped into the UF

module. The retentate circled back into the storage tank under pressure of 4 – 5 bar, while the

permeate was collected in the storage tank 2. The permeate flow velocity was 15 – 20 m/s.

Back-flushing was achieved by using pressurized air to push small amounts of permeate

through the membrane every 3 minutes. The pressure of the back-flushing air was 6 – 8 bar.

Fig. 2

The permeate from UF unit was introduced into the RO system from where it was pumped

under pressure of 1 – 2 bar through a prefiltration unit. The feed was then pumped under high-

pressure of 20 – 30 bar into the spiral-wound module from where the permeate was collected

into a storage vessel, while the retentate was recycled into the feed tank. The membrane used

for the tests was made from polyethersulfone material with filtering surface area of 1.5 m2.

The equipment and the membrane have been cleaned with 1% Ultrasil (Ecolab, USA) solution

after filtrations. After washing, the membrane was rinsed three times with the tap water and

once with the demineralised tap water.

Fig. 3

3. Results and discussion

3.1. Coagulation and adsorption

Table 2

Analyses (Table 2, 3rd column) show that coagulation alone could not remove anionic

surfactant from wastewater, COD removal was only 36 % and BOD only 51%. This is why

after coagulation, adsorption on GAC was also needed. The graphite structure gives the

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carbon a very large surface area, which allows the carbon to adsorb a wide range of

compounds. Activated carbon has the strongest physical adsorption forces or the highest

volume of adsorbing porosity. The water after the GAC treatment was analysed. Table 2

shows the effects of GAC filtration. After GAC treatment, COD removal was 93 %, both

BOD5 and anionic surfactants removals were 95 %. Table 2 shows that all measured

parameters were below the concentration limit of emission into water after GAC wastewater

treatment.

3.2. Pilot scale investigations of UF and RO processes

Correlation of flux decline with time was conducted to obtain preliminary information about

fouling tendency of the membrane. The behaviour of the permeate flux as a function of the

operation time was studied.

Fig. 4

From the Fig. 4, it can be seen that the UF permeate flux appears very stable with the

operating time. Flux versus time experiments for UF unit was performed at optimum

transmembrane pressure (3-5 bar). This indicates that fouling is not a problem on the UF

system during 150 min operation. During the UF, the temperature increased again (54±2°C)

due to the working conditions, and therefore, more favourable permeation rates can be

achieved due to the decrease in viscosity (Mallevialle et al., 1996). Permeate flux was

expressed as volume per unit membrane area per unit time, e.g. Lm-2h-1, (LMH).

Results of analyses of wastewater showed that the temperatures can be up to 80°C, the pH

value is between 9 and 11 as well as the presence of some oxidants like chlorine ions has been

determined. In that case, usage of ceramic membranes is recommended because polymer

membranes such as polyamide membranes can be chemically damaged. However, the

dechlorination of the feed before it enters the membrane system should still be used. The most

popular methods are carbon sorption or the addition of sodium bisulphite or gaseous sulphur

dioxide for removal of chlorine from the effluent (Wakeman, 2001).

From the Fig. 5, it can be seen that no fouling was presented at the RO unit, neither. The

performance was stable; the purity and the consistency of the cleaned wastewater were

maintained.

Fig. 5

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3.3. Membrane filtrations

Chemical analyses were carried out on samples of wastewater, ultrafiltration and reverse

osmosis permeate (Table 3). Concentrated water volume discharged is 20% of the treated one.

Table 3

All measurements were done in the laboratory at room temperature, 25ºC. Adequate total

phosphorous was obtained after ultrafiltration. The COD, BOD5, mineral oil, AOX and

anionic surfactant was not reduced enough, so the reverse osmosis step was necessary. The

ultrafiltration step, however, guaranteed a good performance and duration of reverse osmosis

membrane. The RO permeate had good analytical characteristics, almost all total anionic

surfactant (99.2%) and all organic content was removed. The COD value was reduced by up

to 98.9%, BOD5 up to 99.2 % and mineral oil up to 75%. Almost complete colour removals

were achieved with the RO membrane.

The quality of the permeate produced by the RO module fed on the UF permeate was

satisfactory and acceptable for water reuse in the laundry industry.

3.4. Economical analyses

Economic considerations can be drawn to foresee the economical feasibility of the

implementation of both mentioned methods for a large-scale plant of 200 m3/day. Data

needed for simulation was obtained from laboratory experiments using actual wastewater. The

costs for both techniques are based on operation costs quoted by suppliers for a full-scale

treatment plant and are reported in Table 4.

Table 4

When comparing investment costs between the two kinds of water purification, GAC seems

much more promising. In our case, membranes were economically poor compared to GAC,

when analyzing the total annual costs. However, due to the increasing requirements for

effluent quality and increasing fees for wastewater discharge, the need for water reuse is

increasing. Recycling of water using membrane filtrations is sustainable and environmentally

friendly, because only 25 % of effluent water ends in the environment and about 75 % is

recycled. That means 46 800 m3 of water per year is saved which saves around 50 000 Euros.

Furthermore, in the flocculation process followed by GAC, the wastewater is filtered through

a carbon column to remove residual colour, soluble salts and surfactants. Membrane filtration

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uses no carbon and produces low quantities of waste unlike GAC with 17 tons of waste

production per year.

If 75 % of the water is recycled, the membrane filtration would still be around 50 % more

expensive then GAC method. The main reason for that is the usage of ceramic UF membrane.

Ceramic membranes are considerably more expensive then the standard UF membrane and

are approximately 10 times more expensive then polymer membranes. Ceramic UF

membranes have life expectancy of 10 years and the polymer membranes 3 years. There are

several reasons for use of ceramic UF including lower chemical requirements, superior quality

of the produced water and implementation of higher standards. Today, membrane ceramic

module with an area of 10.7 m2 costs 10 000 euros. It is expected that this price will drop to

5500 euros per module mainly due to two factors: the increase of membrane surface area per

module and the mass production of membrane modules.

Although the costs of membrane systems are higher than conventional treatment systems,

their application is suitable if the costs of land and water supply are very high.

3.5. Market analyses

The ecological and technological standards for modern laundry wastewater treatment were

enforced, within the two projects carried out (Šostar-Turk, 2000; Šostar-Turk, 2003). The

potential market within Slovenia was analysed for membrane water treatment applications. It

was discovered, that out of 140 Slovenian laundries most use conventional methods for

wastewater treatment such as flocculation, sedimentation and filtration. Only three laundries

with water flows between 35 000 to 45 000 m3 per year had ultrafiltration introduced in

addition to conventional treatment. For this reason, membrane treatment consisting of

ultrafiltration followed by reverse osmosis was performed in laboratory. This system allows

up to 75 % of the water to be recycled. In Slovenia there are ten potentional laundries where

such a system would be remunerative, five of them having water flow between 35 000 m3 up

and 100 000 m3 per year.

In addition, a bilateral research project is being carried out between Slovenia and Croatia

(Šostar-Turk, 2002). Presently, market analyses is taking place in Croatia, similar to that

carried out in Slovenia. This country is a very interesting turist destination because of the long

Adriatic coastline with lots of hotels, restaurants, hospitals, where among others, laundry

goods need to be washed. Croatian legislation does not demand any laundry wastewater

treatment at all.

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4. Conclusions

A study of the possibility for wastewater reuse is essential because of its’ large quantities in

the laundering process of industrial laundries. Laundry wastewater possesses the potential for

reclamation and reuse. Such reclamation and reuse of laundry discharge is important to save

water supply and significantly improve urban environments.

Good results were achieved using the conventional methods. These methods are especially

effective in the case of minimizing the organic pollutants to the point where wastewater is

drained into communal sewage or directly into a water. The disadvantage is that there is no

possibility of any kind of selection, which is essential for recycling and re-use. The

consumption of chemicals can be reduced because of better separation characteristics of

membranes compared to the coagulation and adsorption methods. No coagulators and active

carbons are used for membrane filtration. Decreased sludge production has positive ecological

effects. However, membrane filtration is more expensive compared to the GAC treatment

process. Widespread use of membranes will depend on the availability of significantly

cheaper membranes, or the tightening of regulatory standards.

Acknowledgements

We are thankful to the European Commission for its financial support in preparing this paper,

through a grant from EU project EKV1-CT-2000-00049.

5. References

1. Ahn K-H and Song K-G. Treatment of domestic wastewater using microfiltration for reuse

of wastewater. Desalination 1990; 126 (1-3): 7-14.

2. Bhattacharyya D et al. Ultrafiltration of complex wastewaters: recycling for nonpotable

use. J.WPCF 1987; 50 (5): 846-861.

3. EPA, Environmental Protection Agency. Technical Development Document for the Final

Action Regarding Pretreatment Standards for the Industrial Laundries Point Source Category

No 821-R-00-006, Chapter 6, Washington DC, USA, March 2000.

4. Faria PCC et al. Adsorption of anionic and cationic dyes on activated carbons with different

surface chemistries. Water Research 2004; article in Press.

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5. Gosolits J et al. Waschmittel und Wasserrecycling in Gewerblicher und

Krankenhauwaeschereien (Phase 1), project BMBF-FKZ:01 RK 9622, Bekleidungs-

physiologisches Institut Hohenstein, Hohenstein, Germany, 1999.

6. Jakobi G., Löhr A. Detergents and Textile Washing: principles and practise, VHC,

Weinheim, Germany; 1987.

7. Mallevialle J, Odendaal PE, Wiesner MR. Water treatment, membrane processes, McGraw-

Hill, New York, USA; 1996.

8. Mulder M. Basic Principles of Membrane Technology. Kluwer, second edition, Dordrecht.

The Netherlands, 2000.

9. Official Gazette of the Republic of Slovenia. Decree of substance emission during the

removal of wastewater from laundry and dry cleaning 46/02. Slovene Government. Ljubljana,

Slovenia, 2002, p. 4579-4582 (in Slovenian).

10. Petrinić I, Šostar-Turk S, Simonič M. Pročiščavanje otpadnih voda u praonicama rublja

pomoću aktivnog ugljena. Tekstil 2002; 51 (10): 463-469.

11. Petrinić I, Šostar-Turk S, Simonič M. Upotreba naprednih tehnologija za pročišćavanja

otpadnih voda u praonicama rublja. Tekstil 2003; 52 (9): 455-462.

12. Seo GT et al. Ultrafiltration combined with ozone for domestic laundry wastewater

reclamation and reuse. Water Science and Technology, Water Supply 2001; 1 (5/6): 387-392.

13. Šostar-Turk S. Ecological-Technological Standards and Criterion for initiation of proper

technologies for wastewater emissions from laundries and dry cleaner's. Research Project No

2511-00-200011, Faculty of Mechanical Engineering, Maribor, Slovenia, 2000 (in Slovenian).

14. Šostar-Turk S. Programm Setting of Working Monitoring for systems, where washing and

dry cleaning is taking place and analyses of existent systems in the Republic of Slovenia.

Research Project, No 2523-02-100146, Faculty of Mechanical Engineering, Maribor,

Slovenia, 2002 (in Slovenian).

15. Šostar-Turk S. Ecology of textile care. Research Project No. SLO-HRV 3/03-04, Faculty

of Mechanical Engineering, Maribor, Slovenia, 2003 (in Slovenian).

16. Wakeman RJ. Pretreatment methods for membrane filtration. 7th Nordic Filtration

Symposium, 27-28 August 2001, Copenhagen, Denmark.

17. Warmoeskerken MMCG et al. Laundry process intensification by ultrasound. Colloids

and Surfaces A: Physicochemical and Engineering Aspects 2002; 210 (2-3): 277-285.

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Table 1

Parameters of wastewater, standard procedure, methods and concentration limit of emission in

water

Parameter WastewaterConcentration

limit of emission into water

Standard Method/Apparatus

Temperature (°C) 62 30 DIN 38404-C4 / thermometer

pH-value 9,6 6,5-9,0 SIST ISO 10523

electrochemical / pH-meter Iskra MA

5740

Suspended substances (mg/L) 35 80 ISO/DIN 11923

gravimetrical / weighing machine

Mettler AE 100

Sediment substances (mL/L) 2 0,5 DIN 38409-H9 sedimentation

Cl2 (mg/L) < 0,1 0,2 ISO 7393/2 reagent DPD–colourmetric

Total nitrogen (mg/L) 2,75 10 SIST EN 25663 titrimetric

Nitrogen ammonia (mg/L) 2,45 5 SIST ISO 6778

spectrophotometer / Perkin Elmer Cary

1E

Total phosphorus (mg/L) 9,9 1,0 SIST ISO 6878-1

spectrophotometer / Perkin Elmer Cary

1E

COD (mg O2/L) 280 200 SIST ISO 6060 titrimetric

BOD5 (mg O2/L) 195 30 SIST ISO 5815

electrochemical / oximeter WTW

Mineral oil (mg/L) 4,8 10 DIN 38409-18

gravimetrical / weighing machine

Mettler AE 100

AOX (mg/L) 0,12 0,5 SIST ISO 9562

colourmetric / DX-200 Dorhmann

Anionic surfactant (mg/L) 10,1 1,0 SIST ISO 7875-1

spectrophotometer / Perkin Elmer Cary

1E

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Table 2

The determination of parameters in the wastewater before and after treatment with

coagulation

Parameter Wastewater Measured values

in wastewater after coagulation

Measured values in wastewater after

coagulation and active carbon

Concentration limit of emission into

water

Temperature (°C) 62 22 22 30

pH-value 9,6 7,9 6,8 6,5-9,0

Suspended substances (mg/L)

35 <5 <5 80

Sediment substances (mL/L)

2 < 0,5 < 0,5 0,5

Cl2 (mg/L) < 0,1 < 0,1 < 0,1 0,2

Total nitrogen (mg/L) 2,75 2,60 2,60 10

Nitrogen ammonia (mg/L)

2,45 2,40 2,30 5

Total phosphorus (mg/L) 9,9 1,0 1,0 1,0

COD (mg O2/L) 280 180 20 200

BOD5 (mg O2/L) 195 100 10 30

Mineral oil (mg/L) 4,8 2,5 <1 10

AOX (mg/L) 0,12 0,12 <0,1 0,5

Anionic surfactant (mg/L)

10,1 10,0 <0,5 1,0

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Table 3

The determination of parameters in the wastewater before and after treatment with membrane

technology

Parameter Wastewater Permeate UF

Permeate RO

Concentration limit of emission into water

Temperature (°C) 62 53,8 27,8 30

pH-value 9,65 8,3 7,62 6,5 – 9,0

Suspended substances

(mg/L) 35 18 8 80

Sediment substances (mL/L) 2 < 0,5 < 0,5 0,5

Cl2 (mg/L) < 0,1 < 0,1 < 0,1 0,2

Total nitrogen (mg/L) 2,75 0,03 0,03 10

Nitrogen ammonia (mg/L) 2,45 0,03 0,03 10

Total phosphorus (mg/L) 9,92 0,46 0,14 2,0(1.0)

COD (mg O2/l) 280 130 3 120

BOD5 (mg O2/L) 195 86 1,5 25

Mineral oil (mg/L) 4,8 4,4 1,2 10

AOX (mg/L) 0,12 0,11 0,08 0,5

Anionic surfactant (mg/L) 10,06 7,20 0,91 1,0

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Table 4

Investment and operating costs (evaluated in Euro) for UF/RO membrane treatment of 200

m3/day or 62 400 m3/year (full-scale plant)

total annual % of total cost per m3

GAC Membrane plant GAC Membrane

plant GAC Membrane plant GAC Membrane

plant

Cost of plant (investment in 10 years) :

69 600 390 000 6 960 39 000 31 46 0,11 0,63

Energy: - - 1 060 25 200 5 30 0,02 0,4

Chemicals: 28 800 - 2 880 10 000 13 12 0,05 0,16

Membrane replacement (change every 3 years for RO plant)

- 15 000 - 5 000 - 6 - 0,08

Man work: - - 10 200 5000 46 6 0,16 0,08

Waste deposit 10 500 - 1 050 - 5 - 0,17 -

Total 108 900 405 000 22 150 84 200 100 100 0,51 1,35

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Input of Fresh Water

1 2 3 4 5 6 7 8 9 10 11 12

Wastewater

Fig. 1. Tunnel washer

TANK

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Fig.2. The equipment for ultrafiltration.

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Fig.3. The equipment for reverse osmosis.

18

0

20

40

60

80

100

120

140

160

0 50 100 150 200Time (min)

Flux

(LM

H)

0

10

20

30

40

50

60

Tem

pera

ture

(C)

FluxTemperature

Fig.4. Flux versus time for UF.

19

0

10

20

30

40

0 20 40 60 80 100 120 140Time (min)

Flux

(LM

H)

0

10

20

30

Tem

pera

ture

(C)

FluxTemperature

Fig.5. Flux versus time for RO.

20