- Email: [email protected]
Analysis and monitoring: costing textile effluent recovery and reuse
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Filtration+Separation June 2006
Analysis and monitoring:
costing textile effluent recovery and reuse C
ost analysis is a vital exercise to undertake for any process, and in this month’s column we look at a study that tests the implications of a proposed membrane process on reuse and recovery – within a textile process environment in Istanbul, Turkey.
Introduction
About the study
Researchers in Istanbul have investigated the economic feasibility of installing a membrane process for recovering and reusing effluents, within a process at a textile factory based in Istanbul, Turkey.
The study aims to look at whether the use of membrane systems in combination with physicochemical and biological processes is a plausible method for recovery and reuse in the textile industry*.
The recovery system components consist of a sand filter (SF), together with Ultrafiltration (UF) and Reverse Osmosis (RO) (see figure 1).
In addition, before feeding effluent into the membrane system, pretreatment must be carried out to reduce high pollution loads. If suitable pretreatment is not incorporated within the process, the membrane system can be fouled more quickly, leading to problems and inefficiencies within the separation process.
The cost of such membrane systems has decreased through recent technological innovations in membrane technology, and this has lead to an increase in the use of membrane systems for drinking water and wastewater treatment processes. It is now possible to recycle water using membrane systems, and this is one of the most important advantages that such systems have over other pollution control systems. Membrane processes provide the ability to recover dyes and other chemicals without any physical and chemical deformation. Recovered materials can be dewatered – or made more concentrated – and then be reused in various processes. While in some processes water is provided by the recovery system, quantities of both fresh water for process needs (and wastewater discharge) are reduced. Therefore, industrial pollution control and the preservation of water resources are undertaken with a view towards sustainable development. And in this regard membrane systems provide both economical and ecological benefits.
quantities of wastewater from different manufacturing processes. It is essential to study the recovery and reuse of water in the textile industry because of high water consumption and legislative discharge standards in different regions. There have already been studies investigating the recovery and reuse of effluent within the textile industry, and some have obtained the cost of producing water: • Marcucci et al. (2002) studied how two different membrane pilot plants effected
Furthermore, variations in the volume and pollution of wastewater loads make it difficult to determine wastewater characteristics, and this situation has adverse effects on the membrane system’s performance.
Why was the textile sector chosen for the study? The textile industry is one of the most important sectors of the Turkish economy, using intensive amounts of water and therefore generating enormous
Figure 1: proposed wastewater treatment plant units (to be incorporated within the units currently in use).
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Filtration+Separation June 2006
The cost of textile effluent recovery and reuse (Istanbul, Turkey) – in brief
the recovery system was also achieved (see tables 5 and 6).
•
The study: I. about the operation
•
It is technologically possible to produce the specified quality of process water from the treated wastewater, using a membrane system; An industrial wastewater disposal cost of 1.35 /m3 is based on domestic wastewater quantity in Istanbul, and water softening costs in the factory of 0.10 /m3;
• The textile company, which carries out the dyeing and printing of knitting fabric, was established in Istanbul in 1995 – with an area of 10,000 m²; • The maximum production capacity of the factory is 5.5 tonnes/day for dyeing, and 15,000 m/day for printing; • The raw materials used in the dyeing and printing processes are cotton, viscon, lycra, and polyester knitting fabric. In addition, the factory contains dyeing, emprime printing, ram, pad batch, waving, sanforising and sliting units. Reactive and pigment dyes are used for the dyeing process*).
•
The unit cost for the recovery of the treated wastewater – investment, operation and maintenance cost – was worked out to be 0.42 /m3 (based on the current market price in Turkey);
•
Recovered water can be used in such processes;
II. Water consumption and supply
•
The quantity of wastewater discharged can be reduced by 63% using the system proposed;
Process water is supplied from three drilling wells; the flow rates for the first and second wells are 2 lt/sec and that of the third is 5 lt/sec.
•
The utility/cost (F/M) ratio was calculated as 2.2; also, less ground water usage leads to savings in ground water reserves;
•
The reduction in costs associated with running the recovery system indicates that membrane processes can be feasibly used at such factories.
recovery of wastewater within the textile industry. The cost of producing water was found to be 0.40 /m³. • Madwar et al. (2002) studied the cost of recovering wastewater and found it to be US$0.47/m3. • Defrawy (2001) used UF+RO to recover wastewater and generated water recovery costs amounting to US$0.43/m3. Apart from these however, there are only a limited number of studies looking into the recovery – and reuse – of textile effluents using membrane systems. With this in mind, there is a need for new studies to assess the economic applicability of using membrane technology for producing process water from industrial wastewater.
Wellwater is pre-treated by four ionexchange units, in order to obtain the required specification and properties of the process water (the characteristics of the pre-treated wellwater is shown in table 1)*.
III. Current wastewater treatment plant within the factory • The capacity of the extended aeration activated sludge treatment plant is 1000 m3/day. This treatment plant currently used within the process consists of screening, equalisation, neutralisation, coagulation-flocculation, settling, aeration, thickening and a filterpress; • There are no wastewater recovery and reuse units in the current plant; • Water requirements for the factory are 1000 m³/day and thus, 1000 m³/day of wastewater is produced. The COD, TSS, total sulphur, sulphate, and colour are the main pollutants within the wastewater that need to be dealt with.
IV. What did the researchers propose?
In the study we now describe, a recovery system using membranes was proposed for a textile company in Istanbul. The cost of investment, operation and maintenance of the proposed system was determined based on current market prices within Turkey.
The current wastewater treatment plant in the factory was investigated for recovery and reuse, and it was decided that an advanced treatment unit such as a membrane system could be added to treat effluents generated by the present biological wastewater treatment plant – with a view to recovery and hence reuse. The advanced treatment units consisted of a SF, together with UF, and RO (see figure 1).
A cost comparison of water softening, wastewater discharge and water produced by
The removal efficiencies of the SF+UF (and RO) were used to determine the
The textile company chosen by the Turkish researchers carries out the dyeing and printing of textiles such as knitting fabric (pictured); it was established in Istanbul in 1995 – with an area of 10,000 m²
characteristics of the suggested recovery system effluents for the study. As seen in table 3, the RO effluent meets the required process water quality given in table 1. According to the removal efficiency of SF, UF and RO (see table 2), together with the permeate characteristics in table 3, the characteristics of concentrated flow were calculated for the suggested system. Discharge standards into the ISKI’s (Istanbul Water and Sewage and Administration) canal, and concentrated flow characteristics are shown in table 4. As seen in table 4, concentrated flow characteristics do not exceed the discharge standards of ISKI. With these considerations in mind, the treated water coming from the recovery plant was considered for use within processes such as dyeing and washing, as well as for boiler water.
Cost analysis – observations Table 5 shows the design and operating parameters used to obtain costs, and table 6 shows the total cost of the suggested recovery system and process water production from the drilling well. • The wellwater was treated by ionexchange for use in the processes, and wastewater coming from the biological treatment plant is discharged into ISKI canal. Therefore, the factory has to meet water production costs and pay KSUB (a disposal charge for wastewater) to ISKI – for disposal of the biological treatment
27
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Filtration+Separation June 2006
plant effluents. The KSUB cost was about 1.35 /m³. • 0.10 /m3 of water production unit cost was obtained according to the cost of process water production by ion-exchange treatment system from the drilling well (see table 6).
Parameters Total hardness Perm. hardness Temp. hardness (P) Alkaline (M) Alkaline pH Conductivity Chlorine Silis Total ferrum Phosphate Bicarbonate Bicarbonate
Unit °Fr °Fr °Fr ppm CaCO3 ppm CaCO3 µS/cm ppm Cl ppm SiO2 +2,+3 ppmFe ppm PO4 ppm CaCO3 ppm HCO3-
Mignani et al (1999) determined the cost of water production by using an ion-exchange treatment system from a drilling well as 0.11 /m3 for the textile industry. • 0.635m3 water of every 1m3 of process water can be reused in the factory. Thus,
Raw water 12,0 12,0 0,0 0 400 8,06 1295 177,5 13,5 0,03 0 400 488
Soft water 0,1 0,1 0,0 0 430 8,01 1310 177,5 13,6 0,02 0 430 524,6
Washing 0,5 0,0 0,5 0 160 7,00 465 71,0 4,9 0,01 0 -
Boiler water 1,0 0,0 1,0 1600 2320 11,97 10660 1136 79,6 0,14 Trace -
Table 1: characteristics of pre-treated well water, together with the specification of the required process water.
Parameters COD TSS Turbidity Conductivity T. hardness T. Sulphur Sulphate Chloride Colour
Unit mg/l mg/l NTU µS/ cm °F mg/l mg/l mg/lt Ref.
SF+UF 50,00 95,00 90,00 5
Removal efficiency (%) RO Total 87,50 93,75 95,00 90,00 95,91 95,91 99,29 99,29 100,00 100,00 98,70 98,70 99,02 99,02 >95 90,25
Table 2: removal efficiency of membranes (using a SF, followed by UF and RO*) – Marcucci et al (2001) studied SF+UF, together with RO, on a pilot scale plant for the recovery of textile effluent, and obtained removal efficiencies of pollutants are shown above.
Parameter Flow rate COD TSS pH Turbidity Conductivity Tot. hardness Tot. Sulphur Sulphate Chloride Colour removal %
Unit m3/day mg/l mg/l NTU µS/ cm °F mg/l mg/l mg/lt
Influent of SF 1000 240.0 60.0 7.5 7.1 7580 14 0.6 615 1127 Ref.
UF Permeate 850 120 3 7.5 0.71 7580 14 0.6 615 1127 5
RO Permeate 635 15 3 7.5 0.71 310 0.1 0 8 11 >95
Table 3: permeate characteristics of the proposed recovery system (SF & UF and RO).
water demand from the factory processes can be reduced by 63.5%, due to the reuse of recovered water. • The required process water supplied from the well can be reduced, and the cost of water production can also be decreased by 63.5% through reuse (in addition, the biological treatment effluent discharged into the ISKI canal can be decreased to 63.5%, and wastewater disposal costs can be reduced to 63.5%). So, 0.86 /m3 can be saved due to the recovery of 63.5% of the biological wastewater effluent, and 0.06 /m3 can also be saved through reusing the 63.5% of recovered water. As a result, 0.92 /m3 can be saved by reusing 63.5% of the wastewater. The benefit/cost (F/M) ratio was calculated as 0.92/0.42=2.2:1. • The ISKI water tariff for industrial activity was approximately 2 /m3, and the water tariff of the tanker was 2-3 /m3. Thus, the cost of the recovery and reuse of wastewater by advanced treatment methods is a very logical method for supplying water.
Conclusions In this study, a recovery system consisting of SF, UF and RO is suggested for the treatment of 1000 m3/day of biological wastewater effluents. The unit water production cost of the proposed recovery system is 0.42 /m3 based on the current market conditions in Turkey. Furthermore, 0.10 /m3 of water production unit cost is obtained for process water production by an ion-exchange treatment system from a drilling well. Biological wastewater treatment effluent disposal costs of 1.35 /m3 are determined. Water demand of the factory processes and the quantity of biological treatment effluent discharges can be decreased by 63.5% using the suggested recovery and reuse system. The F/M ratio was calculated to be 2.2:1, showing that the suggested recovery system can be applied economically. Significant benefits would be achieved by operating the recovery plant and reducing the fresh water up to 63.5%, and thus a considerable amount of ground water reserve can be preserved. Also, the more the quantity of wastewater discharge is reduced, the less is paid to ISKI.
Parameter Flowrate COD TSS Tot-Sulphur Sulphate
Unit m3/day mg/l mg/l mg/l mg/l
Wastewater 1000 240 60 0.6 615
Concentrated flow Discharge standards 365 618 800 156 350 1.62 2 1668 1700
Table 4: characteristics of activated sludge effluents, concentrated flow and discharge standards of ISKI (Istanbul Water and Sewage and Administration).
Recovery and reuse in a textile industry can therefore be considered technically and economically feasible because of the reduced well water consumption and quantity of wastewater discharge.
•
Important note: Estimating the cost of membrane processes is very difficult, and the
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Cost parameter Value Design & cost parameters Plant capacity (m3/day) 1000 Plant annual operation period (day) 360 Plant life-span ( year) 10 Interest rate ( ) 10% UF recovery rate 85% RO recovery rate 75% Chemical costs Sodium hypochlorite unit Cost %12 liquid (/kg) 0.17 Sodium bisulphite unit Cost % 95 powder (/kg) 0.40 Sulphuric acid unit cost %98 (/kg) 0.10 Antiscalant unit cost %100 liquid (/kg) 11 Sodium hydroxide unit Cost %50 (/kg) 0.15 Energy/cartridge and membrane unit costs Electricity unit cost ()/kW hour) 0.07 Cartridge filter unit cost (/unit) 5 RO membrane ( /unit) 800 Active carbon unit cost (/kg) 2.5 Table 5: design and operating parameters used to obtain costs.
Filtration+Separation June 2006
Cost compounds
Cost (A) Direct capital cost () 300,000 Indirect capital cost () 100,000 Total capital cost () 400,000 / Year) Operation costs( Energy consumption (/ year) 41,453 Membrane change (/ year) 40,000 Staff (/year ) 39,600 Maintainance (/year ) 15,500 Chemicals (/ year ) 39,600 Cartridge change (/ year ) 2,340 Total annual operation cost /year ) ( 178,493 Present worth of operation cost () 1,097.870 Present worth of total production cost () 1,497.871 Total water 3,600.00 (m3/10 years ) Total water production / m ) Cost ( 0.42 0.10
(B) 30,000 10,000 40,000
35,000 6,000 6,000 5,500 -
52,500 322,590
following observations must be taken into consideration – the cost of membrane systems depends on various components; the capital and operational costs are variable – even for the same implementation – because of raw water characteristics; the efficiency of the membrane module; the system’s capacity, technological innovations, and permeate characteristics; plant recovery life-span and interest rates must be determined to obtain investment amortisation; design criteria and the unit costs of suggested recovery system components are given in table 5. The total cost of the suggested recovery system and required processes for water production from wellwater, was calculated according to the unit costs (using the current market price in Turkey) in table 5. *For details of references, please contact the authors or the editor.
362,590 3,600.00
Table 6: total cost of the proposed recovery system, and process water production, from a drilling well (1000 m3/day) [a: cost of suggested recovery plant consisting of SF, UF and RO; b: cost of the process water production with ionexchange system from drilling well]
Authors: Selma Babursah, Mehmet Çakmakci, Cumali Kinaci Istanbul Technical University, Faculty of Civil Engineering, Environmental Engineering Department 34469 Maslak-Istanbul/TURKEY E:[email protected]; E: [email protected]; E: [email protected]
Column
Filtration+Separation June 2006
Analysis and monitoring:
costing textile effluent recovery and reuse C
ost analysis is a vital exercise to undertake for any process, and in this month’s column we look at a study that tests the implications of a proposed membrane process on reuse and recovery – within a textile process environment in Istanbul, Turkey.
Introduction
About the study
Researchers in Istanbul have investigated the economic feasibility of installing a membrane process for recovering and reusing effluents, within a process at a textile factory based in Istanbul, Turkey.
The study aims to look at whether the use of membrane systems in combination with physicochemical and biological processes is a plausible method for recovery and reuse in the textile industry*.
The recovery system components consist of a sand filter (SF), together with Ultrafiltration (UF) and Reverse Osmosis (RO) (see figure 1).
In addition, before feeding effluent into the membrane system, pretreatment must be carried out to reduce high pollution loads. If suitable pretreatment is not incorporated within the process, the membrane system can be fouled more quickly, leading to problems and inefficiencies within the separation process.
The cost of such membrane systems has decreased through recent technological innovations in membrane technology, and this has lead to an increase in the use of membrane systems for drinking water and wastewater treatment processes. It is now possible to recycle water using membrane systems, and this is one of the most important advantages that such systems have over other pollution control systems. Membrane processes provide the ability to recover dyes and other chemicals without any physical and chemical deformation. Recovered materials can be dewatered – or made more concentrated – and then be reused in various processes. While in some processes water is provided by the recovery system, quantities of both fresh water for process needs (and wastewater discharge) are reduced. Therefore, industrial pollution control and the preservation of water resources are undertaken with a view towards sustainable development. And in this regard membrane systems provide both economical and ecological benefits.
quantities of wastewater from different manufacturing processes. It is essential to study the recovery and reuse of water in the textile industry because of high water consumption and legislative discharge standards in different regions. There have already been studies investigating the recovery and reuse of effluent within the textile industry, and some have obtained the cost of producing water: • Marcucci et al. (2002) studied how two different membrane pilot plants effected
Furthermore, variations in the volume and pollution of wastewater loads make it difficult to determine wastewater characteristics, and this situation has adverse effects on the membrane system’s performance.
Why was the textile sector chosen for the study? The textile industry is one of the most important sectors of the Turkish economy, using intensive amounts of water and therefore generating enormous
Figure 1: proposed wastewater treatment plant units (to be incorporated within the units currently in use).
Column
Filtration+Separation June 2006
The cost of textile effluent recovery and reuse (Istanbul, Turkey) – in brief
the recovery system was also achieved (see tables 5 and 6).
•
The study: I. about the operation
•
It is technologically possible to produce the specified quality of process water from the treated wastewater, using a membrane system; An industrial wastewater disposal cost of 1.35 /m3 is based on domestic wastewater quantity in Istanbul, and water softening costs in the factory of 0.10 /m3;
• The textile company, which carries out the dyeing and printing of knitting fabric, was established in Istanbul in 1995 – with an area of 10,000 m²; • The maximum production capacity of the factory is 5.5 tonnes/day for dyeing, and 15,000 m/day for printing; • The raw materials used in the dyeing and printing processes are cotton, viscon, lycra, and polyester knitting fabric. In addition, the factory contains dyeing, emprime printing, ram, pad batch, waving, sanforising and sliting units. Reactive and pigment dyes are used for the dyeing process*).
•
The unit cost for the recovery of the treated wastewater – investment, operation and maintenance cost – was worked out to be 0.42 /m3 (based on the current market price in Turkey);
•
Recovered water can be used in such processes;
II. Water consumption and supply
•
The quantity of wastewater discharged can be reduced by 63% using the system proposed;
Process water is supplied from three drilling wells; the flow rates for the first and second wells are 2 lt/sec and that of the third is 5 lt/sec.
•
The utility/cost (F/M) ratio was calculated as 2.2; also, less ground water usage leads to savings in ground water reserves;
•
The reduction in costs associated with running the recovery system indicates that membrane processes can be feasibly used at such factories.
recovery of wastewater within the textile industry. The cost of producing water was found to be 0.40 /m³. • Madwar et al. (2002) studied the cost of recovering wastewater and found it to be US$0.47/m3. • Defrawy (2001) used UF+RO to recover wastewater and generated water recovery costs amounting to US$0.43/m3. Apart from these however, there are only a limited number of studies looking into the recovery – and reuse – of textile effluents using membrane systems. With this in mind, there is a need for new studies to assess the economic applicability of using membrane technology for producing process water from industrial wastewater.
Wellwater is pre-treated by four ionexchange units, in order to obtain the required specification and properties of the process water (the characteristics of the pre-treated wellwater is shown in table 1)*.
III. Current wastewater treatment plant within the factory • The capacity of the extended aeration activated sludge treatment plant is 1000 m3/day. This treatment plant currently used within the process consists of screening, equalisation, neutralisation, coagulation-flocculation, settling, aeration, thickening and a filterpress; • There are no wastewater recovery and reuse units in the current plant; • Water requirements for the factory are 1000 m³/day and thus, 1000 m³/day of wastewater is produced. The COD, TSS, total sulphur, sulphate, and colour are the main pollutants within the wastewater that need to be dealt with.
IV. What did the researchers propose?
In the study we now describe, a recovery system using membranes was proposed for a textile company in Istanbul. The cost of investment, operation and maintenance of the proposed system was determined based on current market prices within Turkey.
The current wastewater treatment plant in the factory was investigated for recovery and reuse, and it was decided that an advanced treatment unit such as a membrane system could be added to treat effluents generated by the present biological wastewater treatment plant – with a view to recovery and hence reuse. The advanced treatment units consisted of a SF, together with UF, and RO (see figure 1).
A cost comparison of water softening, wastewater discharge and water produced by
The removal efficiencies of the SF+UF (and RO) were used to determine the
The textile company chosen by the Turkish researchers carries out the dyeing and printing of textiles such as knitting fabric (pictured); it was established in Istanbul in 1995 – with an area of 10,000 m²
characteristics of the suggested recovery system effluents for the study. As seen in table 3, the RO effluent meets the required process water quality given in table 1. According to the removal efficiency of SF, UF and RO (see table 2), together with the permeate characteristics in table 3, the characteristics of concentrated flow were calculated for the suggested system. Discharge standards into the ISKI’s (Istanbul Water and Sewage and Administration) canal, and concentrated flow characteristics are shown in table 4. As seen in table 4, concentrated flow characteristics do not exceed the discharge standards of ISKI. With these considerations in mind, the treated water coming from the recovery plant was considered for use within processes such as dyeing and washing, as well as for boiler water.
Cost analysis – observations Table 5 shows the design and operating parameters used to obtain costs, and table 6 shows the total cost of the suggested recovery system and process water production from the drilling well. • The wellwater was treated by ionexchange for use in the processes, and wastewater coming from the biological treatment plant is discharged into ISKI canal. Therefore, the factory has to meet water production costs and pay KSUB (a disposal charge for wastewater) to ISKI – for disposal of the biological treatment
27
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Filtration+Separation June 2006
plant effluents. The KSUB cost was about 1.35 /m³. • 0.10 /m3 of water production unit cost was obtained according to the cost of process water production by ion-exchange treatment system from the drilling well (see table 6).
Parameters Total hardness Perm. hardness Temp. hardness (P) Alkaline (M) Alkaline pH Conductivity Chlorine Silis Total ferrum Phosphate Bicarbonate Bicarbonate
Unit °Fr °Fr °Fr ppm CaCO3 ppm CaCO3 µS/cm ppm Cl ppm SiO2 +2,+3 ppmFe ppm PO4 ppm CaCO3 ppm HCO3-
Mignani et al (1999) determined the cost of water production by using an ion-exchange treatment system from a drilling well as 0.11 /m3 for the textile industry. • 0.635m3 water of every 1m3 of process water can be reused in the factory. Thus,
Raw water 12,0 12,0 0,0 0 400 8,06 1295 177,5 13,5 0,03 0 400 488
Soft water 0,1 0,1 0,0 0 430 8,01 1310 177,5 13,6 0,02 0 430 524,6
Washing 0,5 0,0 0,5 0 160 7,00 465 71,0 4,9 0,01 0 -
Boiler water 1,0 0,0 1,0 1600 2320 11,97 10660 1136 79,6 0,14 Trace -
Table 1: characteristics of pre-treated well water, together with the specification of the required process water.
Parameters COD TSS Turbidity Conductivity T. hardness T. Sulphur Sulphate Chloride Colour
Unit mg/l mg/l NTU µS/ cm °F mg/l mg/l mg/lt Ref.
SF+UF 50,00 95,00 90,00 5
Removal efficiency (%) RO Total 87,50 93,75 95,00 90,00 95,91 95,91 99,29 99,29 100,00 100,00 98,70 98,70 99,02 99,02 >95 90,25
Table 2: removal efficiency of membranes (using a SF, followed by UF and RO*) – Marcucci et al (2001) studied SF+UF, together with RO, on a pilot scale plant for the recovery of textile effluent, and obtained removal efficiencies of pollutants are shown above.
Parameter Flow rate COD TSS pH Turbidity Conductivity Tot. hardness Tot. Sulphur Sulphate Chloride Colour removal %
Unit m3/day mg/l mg/l NTU µS/ cm °F mg/l mg/l mg/lt
Influent of SF 1000 240.0 60.0 7.5 7.1 7580 14 0.6 615 1127 Ref.
UF Permeate 850 120 3 7.5 0.71 7580 14 0.6 615 1127 5
RO Permeate 635 15 3 7.5 0.71 310 0.1 0 8 11 >95
Table 3: permeate characteristics of the proposed recovery system (SF & UF and RO).
water demand from the factory processes can be reduced by 63.5%, due to the reuse of recovered water. • The required process water supplied from the well can be reduced, and the cost of water production can also be decreased by 63.5% through reuse (in addition, the biological treatment effluent discharged into the ISKI canal can be decreased to 63.5%, and wastewater disposal costs can be reduced to 63.5%). So, 0.86 /m3 can be saved due to the recovery of 63.5% of the biological wastewater effluent, and 0.06 /m3 can also be saved through reusing the 63.5% of recovered water. As a result, 0.92 /m3 can be saved by reusing 63.5% of the wastewater. The benefit/cost (F/M) ratio was calculated as 0.92/0.42=2.2:1. • The ISKI water tariff for industrial activity was approximately 2 /m3, and the water tariff of the tanker was 2-3 /m3. Thus, the cost of the recovery and reuse of wastewater by advanced treatment methods is a very logical method for supplying water.
Conclusions In this study, a recovery system consisting of SF, UF and RO is suggested for the treatment of 1000 m3/day of biological wastewater effluents. The unit water production cost of the proposed recovery system is 0.42 /m3 based on the current market conditions in Turkey. Furthermore, 0.10 /m3 of water production unit cost is obtained for process water production by an ion-exchange treatment system from a drilling well. Biological wastewater treatment effluent disposal costs of 1.35 /m3 are determined. Water demand of the factory processes and the quantity of biological treatment effluent discharges can be decreased by 63.5% using the suggested recovery and reuse system. The F/M ratio was calculated to be 2.2:1, showing that the suggested recovery system can be applied economically. Significant benefits would be achieved by operating the recovery plant and reducing the fresh water up to 63.5%, and thus a considerable amount of ground water reserve can be preserved. Also, the more the quantity of wastewater discharge is reduced, the less is paid to ISKI.
Parameter Flowrate COD TSS Tot-Sulphur Sulphate
Unit m3/day mg/l mg/l mg/l mg/l
Wastewater 1000 240 60 0.6 615
Concentrated flow Discharge standards 365 618 800 156 350 1.62 2 1668 1700
Table 4: characteristics of activated sludge effluents, concentrated flow and discharge standards of ISKI (Istanbul Water and Sewage and Administration).
Recovery and reuse in a textile industry can therefore be considered technically and economically feasible because of the reduced well water consumption and quantity of wastewater discharge.
•
Important note: Estimating the cost of membrane processes is very difficult, and the
30
Column
Cost parameter Value Design & cost parameters Plant capacity (m3/day) 1000 Plant annual operation period (day) 360 Plant life-span ( year) 10 Interest rate ( ) 10% UF recovery rate 85% RO recovery rate 75% Chemical costs Sodium hypochlorite unit Cost %12 liquid (/kg) 0.17 Sodium bisulphite unit Cost % 95 powder (/kg) 0.40 Sulphuric acid unit cost %98 (/kg) 0.10 Antiscalant unit cost %100 liquid (/kg) 11 Sodium hydroxide unit Cost %50 (/kg) 0.15 Energy/cartridge and membrane unit costs Electricity unit cost ()/kW hour) 0.07 Cartridge filter unit cost (/unit) 5 RO membrane ( /unit) 800 Active carbon unit cost (/kg) 2.5 Table 5: design and operating parameters used to obtain costs.
Filtration+Separation June 2006
Cost compounds
Cost (A) Direct capital cost () 300,000 Indirect capital cost () 100,000 Total capital cost () 400,000 / Year) Operation costs( Energy consumption (/ year) 41,453 Membrane change (/ year) 40,000 Staff (/year ) 39,600 Maintainance (/year ) 15,500 Chemicals (/ year ) 39,600 Cartridge change (/ year ) 2,340 Total annual operation cost /year ) ( 178,493 Present worth of operation cost () 1,097.870 Present worth of total production cost () 1,497.871 Total water 3,600.00 (m3/10 years ) Total water production / m ) Cost ( 0.42 0.10
(B) 30,000 10,000 40,000
35,000 6,000 6,000 5,500 -
52,500 322,590
following observations must be taken into consideration – the cost of membrane systems depends on various components; the capital and operational costs are variable – even for the same implementation – because of raw water characteristics; the efficiency of the membrane module; the system’s capacity, technological innovations, and permeate characteristics; plant recovery life-span and interest rates must be determined to obtain investment amortisation; design criteria and the unit costs of suggested recovery system components are given in table 5. The total cost of the suggested recovery system and required processes for water production from wellwater, was calculated according to the unit costs (using the current market price in Turkey) in table 5. *For details of references, please contact the authors or the editor.
362,590 3,600.00
Table 6: total cost of the proposed recovery system, and process water production, from a drilling well (1000 m3/day) [a: cost of suggested recovery plant consisting of SF, UF and RO; b: cost of the process water production with ionexchange system from drilling well]
Authors: Selma Babursah, Mehmet Çakmakci, Cumali Kinaci Istanbul Technical University, Faculty of Civil Engineering, Environmental Engineering Department 34469 Maslak-Istanbul/TURKEY E:[email protected]; E: [email protected]; E: [email protected]