Evaluating the Performance of Accelator Clarifier in Eliminating Turbidity by Using Chemical Coagulants

Home , Clarifier

American-Eurasian J. Agric. & Environ. Sci., 13 (4): 565-569, 2013 ISSN 1818-6769 © IDOSI Publications, 2013 DOI: 10.5829/idosi.aejaes.2013.13.04.741

11Bahador Neamati1, Majid Hashemi Cholicheh, 1Hossein Farrokhzadeh, 12 Mehdi Hajian and Narges Khanjani

1Environmental Health Engineering, School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran 2Epidemiology, School of Public Health, Kerman University of Medical Sciences, Kerman, Iran

Abstract: The Accelator system due to its several advantages including putting together different mixing processes, flocculation and sedimentation in one unit, the possibility of simultaneous softening and clarification and relatively acceptable yield, has now attracted the attention of treatment facility designers. Although this method has been used in some areas of Iran, sufficient research about the operation of this unit in real scale and in pilot has not been done. In this study in order to evaluate the operation of the Accelator system in elimination of

turbidity by using chemical coagulants (FeCl3 , PACL) a system in pilot scale was designed and operated in controlled conditions (Temperature = 25°C and pH= 7.2), different turbidities, coagulant doses and detention times. The study showed a significant difference between the detention time and the turbidity of the exiting water (r = -0.98, p-value< 0.05). The maximum yield of the Accelator system in eliminating turbidity was 95% and by injecting 10 mg/l of the coagulating chemical

FeCl3 after 240 minutes, sedimentation was achieved and the turbidity which was 100 NTU in the

entering water reached 5 NTU in exiting water. The efficiency of FeCl3 in eliminating turbidity in Accelators is more than PACL.

Key words: Accelator Clarifier Turbidity PACL Kaolin Pilot

INTRODUCTION This clarifier is a combination of coagulation, flocculation and sedimentation units. This basin due to Nowadays water pollution is one of the most several reasons including no need for sludge collectors or important environmental problems and drinking electro-pumps for returning sludge from the sedimentation safe water with desired quality is an essential part of area to the initial coagulating zone and also no need for human health [1]. Turbidity is one of intercurrent the flash mixing stage and a relatively acceptable yield, factors in useful utilize of water. Conventional has gained many supporters among the designers even drinking water treatment plant consists of coagulation, up to recently and in some situations, especially when the flocculation, sedimentation, filtration and disinfection two processes of softening by lime and clarification are units that coagulation, flocculation, sedimentation and needed simultaneously, is suggested [4]. filtration units use for turbidity removal [2]. The This basin, if designed and operated correctly, Accelator clarification basin was a combination of the despites its difficult operation and requirement for first successful clarifiers, its designing was done about maintenance and frequent adjustment, can operate half a century ago and at its own time was among the efficiently and provide clear water with satisfactory most advanced clarifiers [3-4]. quality. Although in some of the wastewater treatment

Corresponding Author: Majid Hashemi Cholicheh, Environmental Health Engineering, School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran. 565 Am-Euras. J. Agric. & Environ. Sci., 13 (4): 565-569, 2013 facilities in Iran (such as the Jalalieh, Tehran treatment detention time. Whenever the situation changed a grab facility) this type of purifying device is used; because of sample from the exiting water would be taken. In order to its relative sophistication, its operation has faced some control better and compare the operation of different difficulties [5-6]. Meanwhile in the recent years there has FeCl3 and PACL coagulants in optimum conditions, been some improvement in recognizing the mechanisms of different turbidities of entering water were prepared in the coagulation process, however still it is not mentioned the lab. In order to do this, turbidities in 4 ranges as an accurate or thorough science. Because of this, (15- 20, 30- 50, 50- 80, 80- 100) were prepared in a 1500 liter choosing and determining the optimum quantities of container by using Kaolin chemical material coagulants instead of using mathematical formulas is (Hydrated Aluminum Silicate, formula H2 Al 22 Si O,8.8 H 2 O) through experience and by jar tests [6-7]. Jar test has to be and water and then were pumped to the Accelator system. performed for any water which the coagulation process is Initially the effect of detention time alone and then the supposed to be done and then repeated for any effect of detention time and coagulant material with 3 significant change in the water quality [8-14]. Coagulants different concentrations (in which their mean is play an important role in the treatment of water and determined by the jar test) were evaluated in wastewater and in the treatment and disposal of sludge. eliminating turbidity. The Kaolin used was light and in Aluminum sulfate, alum, ferric chloride and etc. are the appearance looked like a white powder and was made in common chemical coagulant used in the coagulation Germany. The results of this exam were used for process. [8, 15]. determining the kind and the dose of the coagulant that The objective of this study was to determine had to be used per unit. the optimum concentration and optimum detention time First the entering water turbidity was determined by for eliminating water turbidity by using chemical the portable turbidity meter model Utech Turbidimeter. coagulation material in the Accelator system and at pilot Then the coagulant was injected by injecting pumps and scale. after a determined detention time for allowing sedimentation of the coagulants, from the exiting tab the MATERIAL AND METHODS turbidity of the exiting water was measured. The range of the detention time was between 90 to 240 minutes and This study was an experiment for evaluating the the dose of the coagulant used was between 5 to 20 operation of the Accelator system in eliminating turbidity milligrams per liter. by using chemical coagulants, at pilot scale. A schematic All of the experiments were conducted according to view of the designed pilot can be seen in Figure 1. the Book of Standard Methods for Water and Wastewater The pilot operated at a certain temperature and pH, but Examination (Standard Method – 2005) [3] and the data different entering water turbidity, coagulant dosage and was analyzed by the Excel and SPSS software.

Fig. 1: A schematic view of the pilot Accelator used in this study

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Effluent Turbidity vs detention time without coagulant 100 90 80 70 60 50 40

Turbidity, NTU 30 20 10 0 80 120 160 200 240 time, min

Turbidity in,20 NTU 5O NTU 100 NTU

Fig. 2: The exiting turbidity in different detention times and without adding coagulants.

PACL effectiveness on effluent turbidityin different PACL effectiveness on effluent turbidityin different detention times (inlet turbidity=20 NTU) detention times ( inlet turbidity=50NTU) 14 39 13 12 34 11 29 10 24 9 8 19 Turbidity, NTU 7 Turbidity, NTU 14 6 9 5 ab 4 4 80 120 160 200 240 80 120 160 200 240 time, min time, min

PACL Dose,5mg/l 10mg/l 20mg/l PACL Dose,5mg/l 10mg/l 20mg/l

PACL effectiveness on effluent turbidityin different detention times ( inlet turbidity=100NTU) 74 64 54

Turbidity, NTU 24 14 c 4 80 120 160 200 240 time, min

PACL Dose,5mg/l 10mg/l 20mg/l

Fig. 3: The exiting turbidity in different detention times by adding different doses of PACL and with entrance turbidities of a)20 b)50 c) 100 mg/l.

RESULTS AND DISCUSSION According to Figure 3, the maximum turbidity elimination by using PACL was in entrance According to Figure 2, without using the coagulant, turbidity of 100 NTU and by injecting 10 mg/l of elimination of turbidity from the system was not efficient. this chemical, in which after 240 minutes of The maximum efficiency of turbidity elimination without sedimentation, turbidity dropped down to 7.5 using the coagulant was 30%, in which the entrance NTU. Therefore the maximum efficiency of PACL turbidity of 20 NTU after 240 minutes dropped down to 14 in eliminating turbidity was about 92% which is a

NTU. The minimum efficiency was 8% in which the little less than the efficiency of FeCl3 in similar entrance turbidity of 100 NTU after 90 minutes of conditions (turbidity, coagulating dose and detention sedimentation reached 92 NTU. time). (Figure 4)

567 Am-Euras. J. Agric. & Environ. Sci., 13 (4): 565-569, 2013

FeCl3 effectiveness on effluent turbidityin different FeCl3 effectiveness on effluent turbidityin different detention times ( inlet turbidity=50NTU) detention times ( inlet turbidity=20NTU) 12 27 11 10 22 9 8 17 7 6 12 Turbidity, NTU Turbidity, NTU 5 7 4 ab3 2 2 80 120 160 200 240 80 120 160 200 240 time, min time, min

PACL Dose,5mg/l 10mg/l 20mg/l PACL 10mg/l 20mg/l

FeCl3 effectiveness on effluent turbidityin different detention times ( inlet turbidity=100NTU)

22 Turbidity, NTU 12 c

2 80 120 160 200 240 time, min

P A C L D o s e , 5mg/l 10mg/l 20mg/l

Fig. 4: The exiting turbidity in different detention times by adding different doses of FeCl3 with entrance turbidities of a)20 b)50 c)100 mg/l.

The minimum efficiency of PACL in the entrance according to Duncan's description the maximum turbidity of 50NTU was seen by adding 5 mg/l of difference was when a coagulant was not added to the coagulant after 90 minutes of sedimentation, in which the system. In other words by increasing the dose of FeCl3 turbidity of the exiting water was measured to be 11 NTU. the efficacy of turbidity elimination increased and the

In other words, the minimum efficiency of turbidity efficacy of FeCl3 in eliminating turbidity in the Accelator elimination was by using FeCl3, 45%. system was more than PACL. According to the Pearson's Correlation test, a CONCLUSION significant difference was detected between the detention time and the turbidity of the exiting water in this pilot According to the One Way ANOVA Test that were and the coefficient (r) was equal to -0.98 (p-value< 0.05). done in different turbidities of entering water in this In other words as the detention time increases, the pilot study, there was a significant difference in the turbidity of the exiting water deceases dramatically. exiting water turbidities without the coagulant between the experiments using PACL and using FeCl3 REFERENCES (p- value< 0.001). In other words, adding coagulants to the Accelator system in 25°C and pH= 7.2 was very 1. Pirsaheb, M., T. Khosravi, K. Sharafi, L. Babajani effective in eliminating turbidity. Also there was a and M. Rezaei, 2013. Measurement of Heavy significant difference in the turbidity of the exiting Metals Concentration in Drinking Water from water in this study when comparing the situation of Source to Consumption Site in Kermanshah – Iran. not using coagulant and after injecting doses of PACL World Appl. Sci. J., 21 (3): 416-423. (p- value< 0.001). There was also a significant difference 2. Angreni, E., 2009. Review on Optimization of in water turbidity in comparing the situation of not using Conventional Drinking Water Treatment Plant. World coagulants and after doses of FeCl3 (p- value < 0.001) and Appl. Sci. J., 7(9): 1144-1151.

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