Environ Monit Assess (2012) 184:5275–5281 DOI 10.1007/s10661-011-2338-6
Characterization and assessment of a large-scale domestic advanced wastewater treatment plant in Turkey Oktay Özkan & Merve Oğuz & Özgür Özdemir
Received: 17 September 2010 / Accepted: 30 August 2011 / Published online: 20 September 2011 # Springer Science+Business Media B.V. 2011
Abstract The paper presents new studies about the removal efficiencies and characterization of the Municipal Wastewater Treatment Plant (MWWTP) in Kayseri, Turkey, which is serving for 800,000 population equivalents with the capacity of 110,000 m3/day, between 2006 and 2009. Kayseri discharges its effluents to Karasu Creek that downstream joins the Kizilirmak river, the longest river in Turkey discharging into the Black Sea. Four years of operation data between 2006 and 2009 calendar years were obtained from KASKI General Directorate. Influent and effluent samples were collected daily and suspended solids (SS), chemical oxygen demand (COD), biochemical oxygen demand in 5 days (BOD5), total nitrogen (TN), and total phosphorus (TP) were measured, aiming to study the evolution of the removal efficiencies for each year. The following yearly mean removal efficiencies were performed in the treatment plant: 94%, 97%, 97%, 95% for SS; 94%, 96%, 95%, 95% for COD; 98%, 98%, 98%, 98% for BOD5; 84%, 87%, 89%, 82% for TN; and 71%, 86%, 80%, 86% for TP, in O. Özkan (*) : M. Oğuz Department of Environmental Engineering, Erciyes University, Kayseri, Turkey e-mail:
[email protected] Ö. Özdemir Wastewater Treatment Department, Kaski General Directorate, Kayseri, Turkey
2006, 2007, 2008, and 2009, respectively. The performance of Kayseri MWWTP was given both in terms of influent and effluent quality and in comparison with the current legislation on discharge limits to the receiving body. During the studied period, mean concentrations in the effluent did not exceed the imposed limits, but sometimes, higher values were noticed for SS, TN, and TP. In conclusion, the plant performances concerning these parameters were excellent and Kayseri MWWTP was operating efficiently according to the conventional control parameters. Keywords Wastewater treatment plant . Characterization . Removal efficiency
Introduction Most MWWTPs have primary treatment which achieves physical removal of floatable and settleable solids and secondary treatment that assures the biological removal of dissolved solids (Brucculeri et al. 2005; Dima et al. 2006; Huertas et al. 2008; Matamoros et al. 2009; Meglei et al. 2006; Vaiopoulou et al. 2007). In order to remove nutrients like nitrogen and phosphorus compounds in the secondary treatment stage, nitrification–denitrification processes are also expected to occur. The number of wastewater treatment plants has been rising in Turkey in recent years because of European Union harmonization process. The municipal wastewater treatment plant (WWTP) of Kayseri (Tur-
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key) has an important mission for the removal of the pollutants that are discharged as effluent in the River of Kizilirmak. Kayseri Province is located in the central region of Turkey with a population of around 1,000,000. Kayseri WWTP has been operated since 2004 by Kayseri Metropolitan Municipality Water and Sewerage Directorate and was designed in two stages. Currently, only the first stage is under operation, serving for 800,000 population equivalents with the capacity of 110,000 m3/day. The WWTP consists of screenings, grit and grease chamber, primary sedimentation, selector, aeration, secondary sedimentation, primary thickening, digestion, secondary thickening, sludge dewatering, and gas storage and energy production units (Fig. 1). The WWTP includes nitrogen and phosphorus removal along with carbon removal. Thirty percent of the daily total energy demand (∼42,300 kWh) of the treatment plant is supplied with energy produced via combustion of methane obtained from the system. The design parameters of the plant are shown in Table 1. The purpose of this study was to assess the performance of Kayseri wastewater treatment plant as one of the big treatment plants in Turkey which discharges into Kizilirmak Basin and to present original results concerning the removal efficiencies related to suspended solids (SS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), nitrogen and phosphorus, between 2006 and 2009. The significance of this study
is that the effluent characteristics of Kayseri WWTP are very important because of discharging the effluents to Kizilirmak basin where Ankara and Kirikkale cities may use Kizilirmak water as a drinking water supply.
Material and method In this study of conventional characterization and assessment, samples were taken daily as 24 h composite samples from the influent and the effluent of the treatment plant throughout 2006–2009. Average values for each month of the studied years were constructed by analyzing influent and effluent 5-day BOD, COD, total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) parameters. For the determination of all parameters concentration, the samples were analyzed immediately after sampling. Three individual measurements were performed and the mean value was reported. All reagents used were analytical reagent grade. All analyses were performed in accordance with Standard Methods (APHA et al. 1998).
Results and discussion Kayseri WWTP should ensure pollutant removal in order to improve the discharged effluent quality in the River of Nitrification and Denitrification
Final Settling Tanks
Primary Settling Tanks
Barracks Grit and Grease andscreen Chamber
Discharge
Bio P/selector tank
Pumping
Pre Sludge Thickener Strain Press ActivatedSludge
CHP Unit LastSludge Thickener
Mechanical Dewatering Sludge Discharge
Anaerobic Digestion
Digester
Fig. 1 Kayseri wastewater treatment plant
Return Sludge
Sludge Mixing
Environ Monit Assess (2012) 184:5275–5281 Table 1 Design parameters of Kayseri Wastewater Treatment Plant
INF. influent, EFF. effluent, R. EFF. removal efficiency
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Parameter
Load (kg/d) Inf.
Eff.
Concentration (mg/l)
R. Eff.
Inf.
Percentage (%)
Eff.
BOD5
42,000
2,200
382
<20
95
NH4-N
6,000
1,100
55
<5
91
Norg
3,140
220
29
2
93
TKN
9,140
1,320
83
<15
82
PO4-P
1,905
220
17
<2
89
TSS
51,340
2,200
469
<20
96
In the national legislation, the receiving water standards are based on organic load/population equivalence. The current standards cover four main parameters without considering the bacteriological status of the effluent. The limits become stricter as the population increases (Table 3). Considering these discharge limits, it can be stated that the treatment plant complies with the related discharge standards in terms of organic matter. The results presented in Table 2 indicated that the treatment plant operated efficiently especially in terms of organic matter removal respect to the fulfilling the discharge standards. The removal efficiencies for all years were found comparable for the parameters of TSS, COD, BOD5,
Kizilirmak. The WWTP secondary treatment stage is important for the removal of organic substances and nutrients, as well as for the overall effluent quality. Table 2 summarizes the data collected during the years of 2006– 2009. The annual average influent and effluent TSS, COD, BOD5, TN, and TP concentrations and removal efficiencies are presented. Standard deviations of the parameters are also given. Figures 2, 3, 4, 5, and 6 are the plots of the average influent and effluent concentrations for BOD5, COD, TN, TP, and TSS, as a function of time in months between 2006 and 2009. Based on the information obtained from the management of the treatment plant, the plant did not encounter to any heavy metal problems during the investigated period.
Table 2 Annual average influent/effluent TSS, COD, BOD5, TN, and TP concentrations and removal efficiencies by years Years
TSS (mg/l) Inf.
2006 Average Max Min
340.9 20 387.4 97
Min
Min
Min
27.2
R. Eff. Inf.
Eff.
R. Eff.
Inf.
Eff.
R. Eff.
7.9 25
51.9 57.1
8.1 23
84%
10 10.7
2.9 5
71%
665.2 41.3 94% 665.2 124
331 380
575.2 15
265.7 4
47.8
3
8.5
1
56.5
36.6
3.2
5.5
0.7
1.4
52.7 64.9
7.1 20
10.1 11
1.4 4.0
46.3
4
9.4
0
5.9
4.3
0.5
0.9
55.6 64
6.3 11
10.2 11.8
2 6
48.3
3
8.5
0
4.6
2.2
1.2
1.6
56.2 66.6
9.8 30
9.5 10.5
1.4 3
32.4
329.2 6
596.2 23
304.2 4
60.9
48.2
5.7
715.8 39.2 95% 829.7 65
407.4 6.7 458.7 11
336.8 8
627.2 31
357.3 4
62.6
33.6
9.5
98%
1.6
413.9 12.7 97% 535.7 22 4.5
98%
6.1
358 6.3 476.1 9
5
Total nitrogen (mg/l) Total phosphorus (mg/l)
Eff. R. Eff. Inf.
675.2 29.8 96% 797.4 39
Stand. D. 56.4 2009 Average Max
94%
Eff.
375 12.2 97% 457.3 21
Stand. D. 39.7 2008 Average Max
R. Eff. Inf.
278.9 6
Stand. D. 37.7 2007 Average Max
Eff.
BOD5 (mg/l)
COD (mg/l)
98%
2.5
89%
442.8 19.8 95% 532.7 53
779.1 36.6 95% 987.9 86
379 6.9 439.3 15
374.8 7
647.5 14
307.4 3
48
2
8.5
1
102.1 22.3
41.2
6.1
9.2
0.7
0.8
Stand. D. 48.1
16
Inf. influent, Eff. effluent, R. Eff. removal efficiency
3.6
98%
87%
82%
86%
80%
86%
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Fig. 2 TSS value changes by year
600
2006
2008
2007
2009
TSS (mgL-1)
500
400
influent
300
effluent 200
100
0 1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 MONTH
which are greater than 94%. The highest removal efficiencies were obtained in BOD5. The TN removal efficiencies were higher than 82% showing the WWTP was capable of producing a nitrified effluent. As far as TP was concerned, the removal efficiency was slightly lower in 2006 and it reached the highest value in 2009. Overall, the reported performances showed high removal efficiencies for all pollutants that were mainly reduced by the biologial processes. Thus, the effluent of the WWTP was in high quality. Concentrations of raw domestic wastewater components were classified weak, middle, and strong by Metcalf and Eddy (2003). According to the average values for the influent wastewater of KWWTP, TSS, COD, BOD5, TN, and TP parameters were found strong. Fig. 3 COD value changes by year
1000
The average values of BOD5/COD ratio were found to be 0.50, 0.53, 0.60, and 0.57 for 2006– 2009 influent wastewaters, respectively. BOD to COD ratio reveals the treatability of wastewater. If the ratio of BOD/COD is above 0.5, the wastewater is considered to be highly biodegradable (Henze et al. 2008). Thus, the biodegradability of Kayseri Municipal Wastewater has been considered to be good. Since most wastewater treatment processes are based on biological degradation and the conversion of the substances, the degradability of the components is important. TKN/COD ratios according to the average values of the influents were 0.08 for all years, and also relevant with the data (0.06–0.08) given by Henze et al. (2008).
2006
2007
2008
2009
900 800
COD (mgL-1)
700 600 influent 500
effluent
400 300 200 100 0 1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47
MONTH
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Fig. 4 BOD5 value changes by year
500
2006
2007
2008
2009
450 400
BOD5 (mgL-1)
350 300
influent
250
effluent 200 150 100 50 0 1
3
5
7
9
11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47
MONTH
trations. The facility exceeded the maximum TN concentrations in January 2006 and 2007; in June and July 2009 (Fig. 5). Similarly, the maximum effluent TSS concentration was exceeded four times during February and April 2006, and April and June 2009 (Fig. 2). Effluent TP concentrations surpassed the permitted limit as seen in Fig. 6. The results show higher values than the imposed limits for TP. The imposed TP concentration in the effluent was respected mostly in 2007 and 2009. These differences could be explained by the complex processes which occur in the aeration tanks (biological treatment with effluent filtration).
The wastewater treatment facility of Kayseri met all permit requirements for TSS, COD, BOD5, TN, and TP for the years 2006–2009, although some peak values were observed for TSS, TN, and TP. According to Urban Wastewater Treatment Directive, discharge standards for secondary treatment plants are as follows: 2 mg/L for TP and 10 mg/L for TN. Figure 4 indicates that KWWTP facility consistently achieved average effluent BOD5 concentrations or less over the entire years. Effluent permits based on COD were also able to meet effluent limits or less (Fig. 3). The WWTP was capable of producing a nitrified effluent although four times violations were reported for effluent TN concen-
Fig. 5 Total nitrogen value changes by year
70
2006
2007
2008
2009
60
TN (mgL-1)
50
influent 40
effluent
30
20
10
0 1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47
MONTH
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Fig. 6 Total phosphorus value changes by year
14
2006
2007
2008
2009
12
TP (mgL-1)
10 8 influent effluent
6 4 2 0 1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 MONTH
The results of the conventional characterization study of Kayseri MWWTP wastewaters showed that the characteristics of the influent wastewater varied in a wide range. It was observed that the concentrations for each parameter seemed to increase from 2006 to 2009. This might be explained by additional wastewaters due to the connection of new residential areas to the sewage system. Besides, since the organized industrial zone wastewater characterization changed and its flow rate increased, the influent wastewater characteristics also changed over the course of the studied time. In addition, the strength of the parameters in the influent appeared to be risen in the second half of the years. That might be caused by the increase of the pollution load due to heavy precipitation. On the other hand, despite the differences in the parameter concentrations in the influent, the results of the conventional characterization study of Kayseri MWWTP wastewaters indicated that the characteristics of the effluent wastewater were stable and did not vary in a wide range except
Table 3 Discharge standards of domestic wastewater to receiving bodies in Turkey (WPCR 2004)
minor changes such as in TN in 2 months in 2009. The treatment facility exceeded the maximum TN concentration in June and July 2009. In addition, the effluent concentrations for the parameters of TSS, COD, BOD, and TN reached peak values in February of 2006 compared with typical effluent concentrations. That might be explained by the excessive loading coming from the wastewater of the sugar industry in a short period of time. After this industry's wastewater separated from the sewage system, the effluent concentrations were back to the normal values.
Conclusion In this study, the performance of Kayseri Wastewater Treatment Plant was evaluated between 2006 and 2009. This study is the first for determination of general performance and characterization of wastewater in Kayseri.
Parameter
Composite sample (2 h), pop. 1,000–10,000
Composite sample (24 h), pop. 1,000–10,000
Composite sample (2 h), Pop. >100,000
Composite sample (24 h), pop. >100,000
BOD5, mg/L
50
45
40
35
COD, mg/L
160
110
120
90
TSS, mg/L
60
30
40
25
pH
6–9
6–9
6–9
6–9
Environ Monit Assess (2012) 184:5275–5281
Kayseri Wastewater Treatment Plant was projected for minimum 92% BOD5 and 94% TSS removal. The removal efficiencies considered at the design were achieved for all years. Average removal efficiencies were 98% and 96% for BOD5 and TSS, respectively. Overall determined efficiencies were 96% for COD, 86% for TN, and 80% for TP. The results emphasize that the wastewater treatment plant has high removal performance and the facility met its respective effluent limitations for BOD, TSS, COD, TN and TP and the flow. The wastewater influent concentrations decreased during the spring months at regard of the figures because of the spring rainfall. The drinking and irrigation water of Kayseri city is supplied by groundwater. Due to possible drought during summer months, it is very likely to encounter the lack of the irrigation water supply. Taken into consideration of global warming, it would be recommended to use the effluent wastewater of Kayseri Wastewater Treatment Plant as irrigation water. Farmers who come across shortage of water for the duration of hot summer months could attempt to use the untreated sewage wastewater for the irrigation. On the other hand, wastewater reuse will be one of the most important environmental issues in Turkey in the nearest future (WHO 2006). Therefore, after detailed analyses and examinations were performed, if treated wastewater is found suitable, practice of wastewater reuse for irrigation can be considered consciously. Effluent filtration may be required to reach irrigation standards. Further investigations should be carried out especially to study about reuse of Kayseri MWWTP effluent.
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