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Current_situation_of_urban_wastewater_treatment_plants_in_megacity_Istanbul-

Current situation of urban wastewater treatment plants

in megacity Istanbul

Idil Arslan-Alaton*, Gulen Iskender, Aysegul Tanik, Melike Gurel,

Suleyman Ovez, Derin Orhon

Department of Environmental Engineering, Faculty of Civil Engineering, Istanbul Technical University, ITU,

34469 Maslak, Istanbul, Turkey

Tel. +90 212 285 3786; Fax: +90 212 285 3781; email: arslanid@https://www.wendangku.net/doc/039526831.html,.tr

Received 05 September 2007; revised 15 April 2008; accepted 22 April 2008

Abstract

Within the framework of a European Union-funded project, a comprehensive questionnaire has been prepared and a survey has been realized among the already existing urban wastewater treatment plants of the country with the aim of investigating the reuse possibility of treated effluents. This study forming one of the project milestones,aimed at putting forth the existing situation of the urban wastewater treatment plants of the Greater Metropolitan Istanbul which is one of the most crowded cities of the world. The current situation revealed that as the city has scarce available land and is surrounded by sea, primary treatment is favored. Some of the plants own biological treatment units where the effluents comply with the discharge to receiving water standards. Most of the plants serve to populations over 100 000 and face operational problems such as lack of automation, clogging of pipes,old-fashioned equipment and working over-capacities. The Water and Sewerage Administration of Istanbul (ISKI) has to supply high quality drinking water to the inhabitants of the city and is responsible for the treatment of the urban wastewater. ISKI has started to initiate not only secondary but also advanced biological treatment units to the already existing plants and urges the companies in charge of their construction to operate the plants for 20 years.

Keywords:Urban wastewater treatment plants; Primary treatment; Biological treatment; Advanced biological

treatment; Marine discharge systems; Istanbul

1. Introdu ction

Istanbul is one of the highly populated cities of the world facing unplanned and uncontrolled

urbanization. With regard to its strategic geo-graphical location, climatic conditions, ease of transportation and employment opportunities,almost half of the industries in the country are set-tled within and/or in the vicinity of this metropo-lis. The population of Istanbul in 2007 has been

*Corresponding author.Presented at the: MEDA WATER International Conference on Sustainable W ater Management, Tunis, March 21–24 2007.

246 (2009)409–416

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stated as 12.5 million inhabitants by the National Statistical Institute [1]. Currently, almost all the inhabitants are served with high quality water for domestic purposes through the existing surface water reservoirs scattered in the city [2]. There are five water treatment plants in operation sup-plying suitable drinking water to the city. After 1980’s, efforts have been realized on the manage-ment of wastewater arising from the metropolis [3–5]. Wastewater treatment plants are being installed. Of late, there are a total number of 15 wastewater treatment plants.

In this study, the results of a detailed survey on the existing situation of Istanbul’s urban wastewater treatment plants (UWWTPs) will be summarized. Location of urban wastewater treat-ment plants are shown in Fig. 1. A comprehen-sive questionnaire was prepared and sent to the technical staff of these urban wastewater treat-ment plants within the framework of an EU-funded project (acronymed “MEDAWARE”) where Istanbul Technical University’s (ITU)Department of Environmental Engineering acts as one of the Turkish project partners [6]. Even though the aim of this completed project (July 2007) was to investigate the reuse possibilities of treated urban wastewaters in agricultural activities, one of the remarkable conclusions of the project was the unfeasibility of reusing the treated effluents in agriculture, since presently none of the biological treatment plants bear dis-infection units.

The prepared questionnaire covered all techni-cal information on the treatment technologies applied, wastewater treatment capacity, start-up date, treatment units installed together with the mechanical equipments and facilities used, treat-ment efficiency in terms of national discharge standards, effluent discharge method and location, sludge management practices, technical personnel in charge of the operation, energy consumption, and finally the major operational problems encountered together with future suggestions for

capacity increase and upgrading considered [7]. Fig. 1. Location of wastewater treatment and discharge systems of Greater Metropolitan Istanbul [8]. (1. Yenikapi UWWTP, 2. Buyukcekmece UWWTP, 3. Uskudar UWWTP, 4. Kadikoy UWWTP, 5. Kucukcekmece UWWTP, 6. Kucuksu UWWTP, 7. Atakoy UWWTP, 8. Tuzla UWWTP, 9. Pasakoy Advanced UWWTP, 10. Terkos UWWTP, 11. Bahcesehir UWWTP, 12. Baltalimani UWWTP, 13. Canta UWWTP, 14. Silivri UWWTP and 15. Gumusyaka UWWTP). 410

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2. General information on the urban

wastewater treatment plants of Istanbul

Until 1994, only 9% of daily wastewater had been treated, while this percentage increased to 85% by the installation of new plants. The daily amount of wastewater treated in Istanbul over years till 2007 is shown in Fig. 2. As evident from the figure, the construction and operation of the UWWTPs have shown a significant increase since 2002, as the daily average treated waste-water increased dramatically from 942 000 in 2002 to 2 085 000 m3/d in 2006 [2]. In 2007, the average treated urban wastewater was 1 995 146 m3/d including storm and seawater due to intru-sion. Approximately 15% of the treated waste-water consisted of intruded water. Thus the net treated amount of urban wastewater was 1 691 000 m3/d. On the other hand, Table 1 presents the general characteristics of the UWWTPs located in Greater Metropolitan Istanbul. It is important to note that only quite limited information is available for the more recently established waste-water treatment plants such as Gumusyaka, Silivri and Canta UWWTPs. The tender stage of installing advanced treatment units (for phospho-rus and nitrogen removal) to the already existing biological treatment plants (Terkos and Tuzla UWWTPs) is over, and the Water and Sewerage Administration of Istanbul (ISKI) plans to com-plete the construction of these advanced treat-ment units till the end of year 2008. For the rest of the existing treatment plants, it is among the most urgent and short-term plans of ISKI to intro-duce advanced biological treatment units to the existing preliminary treatment plants that cur-rently have marine outfall systems for effluent discharge. However, only Yenikapi treatment plant faces insufficient available area to install secondary biological treatment units. F urther, construction of advanced treatment units are listed by ISKI as priority issues regarding the compliance of the discharged effluent quality with the national receiving water standards. Among the most critical ones, Terkos plant, dis-charging its effluent to the Terkos Dam can be addressed. Thus, ISKI has given the priority of installing advanced treatment units to this partic-ular plant.

The current legislation on discharge of wastewater in Greater Metropolitan Istanbul has been revised on 15.06.2007 and published on 27.06.2007 [10]. According to the changes made, discharge standards into the sewer system

is divided into two groups, namely the discharge Fig. 2. Daily amount of urban wastewater in Istanbul treated for the period 1993–2007 [8].

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standard into sewer system that connects to a wastewater treatment plant, and a discharge standard to the sewer system that ends with marine outfall. Therefore, urban wastewater has to comply with the standard according to the final discharge type. For instance, chemical oxy-gen demand (COD) discharge limit values are given as 4 000 mg/L (for discharge into sewer system ending up with treatment) and 600 mg/L (for marine outfall) and suspended solids (SS) discharge limit values are 500 mg/L (for dis-charge into sewer system ending up with treat-ment) and 350 mg/L (for marine outfall). No total nitrogen and total phosphorus limits exist for into sewer system ending up with treatment, however, the limit values for total nitrogen and total phosphorus are 40 mg/L and 10 mg/L for outfall, respectively.

Table 1

General characteristics of the urban wastewater treatment plants of Istanbul [7,9]

Maximum Treatment Average Treated

Capacity (Treated Urban Wastewater

Urban Wastewater Start-up Wastewater)in the Year 2007Treatment Final Discharge Treatment Plant Date(× 103m3/d)(× 103m3/d)Technology Environment Yenikapi1988864.000633.090Primary treatment Deep Sea Outfall

(Sea of Marmara) Buyukcekmece1998155.12036.042Primary treatment Deep Sea Outfall

(Sea of Marmara) Uskudar199277.76027.195Primary treatment Deep Sea Outfall

(Sea of Marmara) Kadikoy2003833.000368.249Primary treatment Deep Sea Outfall

(Istanbul Strait) Kucukcekmece2003354.000120.828Primary treatment Deep Sea Outfall

(Sea of Marmara) Kucuksu2004640.000144.492Primary treatment Deep Sea Outfall

(Istanbul Strait) Atakoy19967.650 6.863Biological treatment Creek and then

Deep Sea Outfall

(Marmara Sea) Tuzla1998150.000241.581Biological treatment Deep Sea Outfall

(Sea of Marmara) Pasakoy2000125.00065.657Advanced Biological Creek (Riva) and

treatment then Deep Sea

Outfall (Black Sea) Terkos2000 1.730545Advanced Biological Terkos Dam Lake

treatment(Black Sea) Bahcesehir20047.400 6.161Biological treatment Creek Baltalimani1997625.000339.257Primary treatment Deep Sea Outfall

(Istanbul Strait) Canta 2005 1.600 1.846Biological treatment Deep Sea Outfall

(Sea of Marmara) Silivri2006 1.200 2.077Biological treatment Deep Sea Outfall

(Sea of Marmara) Gumusyaka2007 1.700 1.253Biological treatment Deep Sea Outfall

(Sea of Marmara) Total 3.845.160 1.995.146

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In all the UWWTPs in Istanbul, primary (physical/mechanical) treatment is applied, all of them are equipped with coarse screens, fine screens, grit chambers and primary sedimentation tanks. One of the major common operational problems of the preliminary treatment systems are continuous clogging of coarse and fine screens. Seldom organic material settling is observed in the grit chambers. In case of insuffi-cient performance maintained in the grit cham-bers, the wastewater transfer pumps are worn-out and may require regular maintenance. Only at the Kadikoy and Pasakoy UWWTPs, oil and grease removal is additionally realized. Preliminary treatment efficiencies rely highly on proper oper-ation and maintenance of the mechanical equip-ments used. This can only be achieved by the employment of qualified and well trained techni-cians. Otherwise, the expected efficiency cannot be provided. The common desire of the local authorities is to install automation to these sys-tems. Manual monitoring and control of these mechanical plants that especially serve to a pop-ulation of >100 000 becomes difficult, causing malfunctioning. Besides making the monitoring of the plants easily, the automation techniques enable the personnel to overcome the troubles in the most quickest and efficient manner. This cir-cumstance is clearly defined in the questionnaires distributed to the operators.

Although currently 15 UWWTPs are in opera-tion, 7 practice preliminary treatment, 6 secondary (biological) treatment and only 2 of them are advanced (biological) treatment systems. Out of the 6 secondary biological treatment systems, only Atakoy treatment plant operates a trickling filter, whereas the rest practice activated sludge treat-ment. The advanced UWWTPs (located in Pasakoy and Terkos) have extended aeration systems for fur-ther phosphorous and nitrogen removal. It is observed that anaerobic treatment as an alternative has not yet been applied in any of the plants.

The major problem of these biological sys-tems is that they presently lack sufficient sludge treatment systems. The sludge arising from the plants are finally sent to solid waste landfills of the Metropolis and their disposal is not well mon-itored. The main reason of retarding to install sludge treatment units is the high investment costs. However, ISKI has started to deal with this problem, besides searching for feasible alterna-tives for sludge treatment; their reuse alternatives are also being investigated. The sludge arising from primary treatment systems is directly deliv-ered to the nearest municipal sanitary landfill. In the secondary treatment units, the sludge is first collected, thickened with polyelectrolyte addition and dewatered via belt press filters. Only Atakoy plant has an anaerobic digester instead of a sludge thickening unit. Finally the sludge cake is sent to the nearest sanitary landfill. More detailed infor-mation was gathered from Tuzla Biological and Pasakoy Advanced Biological Treatment Plants; the sludge treatment of Tuzla plant consists of a sludge thickener, dissolved air flotation (DAF), anaerobic sludge digester and dewatering units. On the other hand, Pasakoy plant has two sludge treatment units, namely, DAF and sludge dewa-tering (centrifuge).

None of the biological treatment plants bear disinfection units as the final polishing units prior to discharge. This is because the national receiv-ing water discharge standards do not contain any of the bacteriological parameters [11].

Pasakoy and Terkos plants serve a population of 250 000 and 7 000, respectively. No significant operational problems have yet been recorded for these treatment plants.

3. Treatment efficiencies of the wastewater

treatment plants and main operational

problems faced

The treatment performances of the existing plants have to be determined by analyzing the grab samples taken from the influent and effluent of the treatment plants regularly. However, the influent analyses are seldom conducted at the

I. Arslan-Alaton et al. / Desalination 246 (2009) 409–416413

I. Arslan-Alaton et al. / Desalination 246 (2009) 409–416 wastewater treatment plants that practice primary

treatment in Istanbul. Discharged effluent analy-

ses are preferred for marine outfall. The main

reason of this circumstance is to monitor the

quality of the effluent and check the compliance

of the quality with the stated discharge limits.

The national discharge standards for marine out-

fall are as follows: 5-day biochemical oxygen

demand (BOD

5) = 250 mg/L; COD = 350 mg/L

and SS = 400 mg/L [11,12]. These standards are

for the marine outfall systems where preliminary

treatment is required.

The national discharge standards for

UWWTPs depend on population. The limits

(daily sampling) stated for a population ranging

between 10 000 – 100 000 are as follows: BOD

5 = 45 mg/L; COD = 100 mg/L and SS = 30 mg/L

[11,12]. For instance, Bahcesehir UWWTP has to

obey to these limits.

Pasakoy UWWTP serving a population of 250 000 capita has to comply with the limits for pop-ulation over 100 000,namely BOD

= 35 mg/L; COD = 90 mg/L and SS = 25 mg/L [11,12].

The analysis results of the influent and efflu-ent samples of the treatment plants are given in Table 2 and Table 3 for primary and secondary-advanced UWWTPs, respectively. As it is evident from the effluent parameters, Terkos and Pasakoy treatment plants applying advanced treatment, exhibit highest treatment performance. Uskudar Treatment Plant on the other hand, facing opera-tional problems, has the lowest pollutant removal efficiencies. For the time being, the wastewater that has to be treated at Uskudar Treatment Plant is directed to Kadikoy Treatment Plant till its operational troubles are overcome. Apart from the Uskudar Treatment Plant, the others comply with the discharge standards to the sea environment.

Table 2

Influent and effluent values given for the primary urban wastewater treatment plants of Istanbul

Influent/Effluent (2006 Values)

Treatment Plant BOD

(mg/ L)COD (mg/ L)SS (mg/ L) Baltalimani 248/194489/399188/201 Buyukcekmece 200/143500/400–/258 Kadikoy –/196–/371–/23 Kucukcekmece –/160–/349–/182 Kucuksu 360/223516/374307/223 Uskudar 430/353–/612–/307 Yenikapi –/214–/485–/225

Table 3

Influent and effluent values given for the biological and advanced biological urban wastewater treatment plants

Influent/Effluent (2006 Values)

Treatment Plant BOD

5(mg/ L)COD (mg/ L)SS (mg/ L)NH

+-N (mg/ L)PO

3?-P (mg/ L)

Atakoy 250/14500/46250/1725/321/16 Bahcesehir –/18–/58–/22–/––/–Pasakoy 236/16432/49324/3348*/13 4.4/3.0 Terkos 125/8322/23218/436*/11.2 4.8/1.4 Tuzla 348/124672/241628/139–/––/–*Nitrogen is measured as Total Kjeldahl Nitrogen (TKN).

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I. Arslan-Alaton et al. / Desalination 246 (2009) 409–416Table 4

Energy consumption and number of technical personnel of the treatment plants

Wastewater Energy Treatment Plants Consumption Number of of Istanbul (kW/month)Technical Personnel Atakoy N.A.

Bahcesehir 45 450

9Baltalimani 818 00019Buyukcekmece 98 000

24Kadikoy 916 00034Kucukcekmece 252 600

19Kucuksu 142 710

20Pasakoy 781 560

66Terkos 9 0306Tuzla 1 300 000

85Uskudar 74 88018Yenikapi 1 100 000

N.A: no data available.

Tuzla Treatment Plant has had some operational problems like filamentous bulking and foaming and thus the national discharge limits could not be complied in 2006. However, improvements in the processes have provided better removal effi-ciencies in 2007.

The COD standard of 350 mg/L is met only at the plants that have a biological treatment system.Obviously, the COD treatment efficiency of pri-mary (mechanical/physical) treatment is quite low, thus the effluent COD’s remain far above the discharge limits. None of the treatment plants currently face treatment problems related with the SS parameter. Sufficient SS values are achieved for all treatment plant effluents.

The treatment performances of the plants indi-cate that secondary treatment has to be applied to achieve sufficient removal efficiencies. Hence ISKI has started to plan construction of second-ary, biological treatment units in addition to the primary treatment plants. In cases where second-ary or even advanced treatment is applied to the wastewater, the search for reuse possibilities should be considered.

No automation is available in the plants for the time being. Most of the treatment plants have primary treatment systems operating man-ually. F urther suggestions of the authorities include, extension of the already existing facil-ities to biological treatment units. From 2006onwards, all the tenders for the installation of wastewater treatment plants will depend on the Build-Operate-Transfer model. Operation of the plant will be conducted by ISKI; however, the maintenance will be under the responsibility of the construction company that installs the plant for a period of 20 years starting from the oper-ation date. The operational costs of the plants are mainly the energy costs to run the mechan-ical equipments. Polyelectrolyte is the only chemical used especially in the biological treat-ment systems.

Table 4 shows the energy consumption and number of technical personnel in charge of the

operation of the plants. According to the plant operators and the authorities, the major problems of the plants are the lack of automation that highly hinders proper operation of these large plants [2]. Secondly, insufficient maintenance in the plants causes clogging problems in the equip-ments. Moreover, some mechanical parts are worn-out increasing electricity costs. If proper maintenance is practiced at the plants, energy costs will be kept at a minimum and also the serv-ice lives of the equipments will be longer.Employing qualified personnel is an obligation at the plants especially in the biological treatment plants. The only treatment plant with qualified technicians is the Pasakoy Advanced Wastewater Treatment Plant, where mainly environmental engineers are in charge of the treatment plant.4. Conclu sions

Most of the UWWTPs installed in the Greater Metropolitan Istanbul serve to populations over 100 000 and 7 are primary treatment plants that discharge their partially treated effluents to the marine environment. Only 6 of the UWWTPs bear biological treatment systems and two of

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them are advanced biological treatment facilities that discharge their effluent to receiving waters apart from the marine environment. There is a high interest and tendency in the whole Metrop-olis to extend the existing treatment systems by installing biological and advanced treatment units. Sludge treatment and disposal systems also need to be upgraded. These problems are planned to be solved in the nearest future. Automation is also lacking which is a necessity for proper control of the treatment plants and for minimized energy consumption/ optimized treat-ment performance. ISKI has already started to take necessary protective measures in 2006 and initiated the application of some strict rules. At the tender stage, the companies are asked to offer for the investment of the treatment systems as well as the operation costs for the 20 years of operation. The construction companies from now onwards will be responsible for the quality of the effluents. This situation has enforced the compa-nies to employ trained personnel in the operation of the systems and to consider the spare parts that may be required during the 20 years of operation. Acknowledgements

This study was conducted within the framework of the EU-funded MEDA-Water project named “Development of Tools and Guidelines for the Promotion of the Sustainable Urban Wastewater Treatment and Reuse in the Agricultural Produc-tion in the Mediterranean Countries” (project acronym is MEDAWARE). The technical support of ISKI technical staff for supplying the authors with the required 2006–2007 data is gratefully acknowledged.References

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