Expert answer:COAGULATION AND FLOCCULATION TREATMENT OF WASTEWAT

Expert answer:these are tow more articles all what you have to do is reading carfully then answer the questions .its the same questions for both of them .
artical_222.docx

article111.docx

questions.docx

Unformatted Attachment Preview

December 2010, Volume 1, No.2
International Journal of Chemical and Environmental Engineering
Improvement of Coagulation-Flocculation Process
for Treatment of Detergent Wastewaters Using
Coagulant Aids
A. Ayguna, T. Yilmazb
a
Department of Environmental Engineering, Selcuk University, Konya, Turkey, ahmetaygun@selcuk.edu.tr
b
Kocaeli Provincial Department of Environment and Forestry, Kocaeli, Turkey, tuba.ertugrul@gmail.com
Abstract
In this study, coagulation-flocculation process was used to treat detergent wastewater with ferric chloride as coagulant. The
improvement of the process by using polyelectrolytes and clay minerals (montmorillonite and bentonite) as coagulant aids was also
investigated. The results of the wastewater characterization showed that the concentration of organic matter expressed as che mical
oxygen demand (COD) was as high as 24.3 g/L while the biochemical oxygen demand was low. Chemical treatment can be
considered as a suitable option for treatment of detergent wastewater due to the low ratio of BOD5/COD. Coagulation/flocculation and
precipitation studies were performed in a conventional jar-test apparatus. The coagulant dosage of ferric chloride ranged between 0.5
g/L and 3 g/L, whereas the concentrations of polyelectrolyte and clay minerals varied between 5-75 mg/L and 25-750 mg/L,
respectively. The optimal condition was obtained at the dosage 2 g/L ferric chloride at pH 11 with the COD removal efficiency of
71%. Addition of coagulant aids provided higher removal efficiencies. Using clay minerals at the dose of 500 mg/L with ferric
chloride provided 84% of COD removal and the removal efficiency of COD increased with using polyelectrolyte, resulting in an
efficiency of 87%. The maximum removal efficiency was obtained with the addition of polyelectrolyte and it was found that the ferric
chloride combination with coagulant aids, at certain pH and agitation speed, provided higher removal efficiencies compared to
coagulation with ferric chloride alone.
Key Words: coagulation-flocculation, detergent wastewater, ferric chloride, polyelectrolyte, clay minerals
1. Introduction
Detergent wastewater discharge can cause serious
environmental problems because detergent product and its
ingredients can be relatively toxic to aquatic life [1].
Anionic and nonionic surfactants are major components
of synthetic detergents. In order to protect the water
environment, an efficient treatment process must be
applied [2]. Due to its complexity, detergent wastewater
is very difficult to treat [3].
Methods for removal of surfactants involve
processes such as chemical and electrochemical
oxidation, membrane technology, chemical precipitation,
photocatalytic degradation, adsorption and various
biological methods. Each of them has limitation and some
drawback in application [4].
Treatment of surfactant wastewaters by biological
processes such as activated sludge is problematic due to
the low kinetics of degradation and foam production [5].
Hence, among the currently employed chemical unit
processes in wastewater treatment, coagulationflocculation has received considerable attention because
of high impurity removal efficiency.
Coagulation/flocculation is a commonly used
process in water and wastewater treatment in which
compounds such as ferric chloride and/or polymer are
added to wastewater in order to destabilize the colloidal
materials and cause the small particles to agglomerate
into larger settleable flocs [6]. FeCl 3 is an important
coagulant in wastewater treatment and can be used for
color removal [7-8], organic matter removal in leachate
[9], solid removal from fisheries wastewaters [10],
treatment of municipal wastewater [11], surfactant
removal from microelectronic plant wastewater [4].
Abdulhassan et al, [4] found that coagulationflocculation process using FeCI 3 can be used effectively
for removal of surfactants and COD from microelectronic
plant wastewater and the removal efficiencies of 99% and
88% were obtained, respectively. Also they found that the
rate of COD removal decreased if the pH was lower than
7 or higher than 9.
High operating costs due to the use of chemical
substances and high amount of sludge and its disposal
costs are shown as the important disadvantages of
chemical treatment [12]. Therefore, researchers have
focused on new alternative methods to reduce chemical
usage by improving discharge standard with adding low
cost natural substance.
Clay minerals are natural substances used in
wastewater treatment and have high ion exchange
2.1Experimental Procedure
capacity, absorption, and catalysis properties as well as
natural and low-cost materials [13]. Some researchers
reported that clay minerals can be preferable coagulant
aid for removal of toxic compounds, pesticide, herbicide,
heavy metals and color removal [14].
It is clear that all treatment methods in use have
some drawbacks, and there is a need to look for other
alternative methods. In the literature, there is some
evidence that clay minerals, when used in conjunction
with coagulants result in improved COD removals, as
compared to used alone [15]. However, there are no
detailed studies in the literature about the comprehensive
investigation of using clay minerals in coagulation
process for treatment of detergent wastewater.
The aim of this study is treatment of detergent
wastewater by coagulation-flocculation process using
ferric chloride as coagulant. And also, improvement of
process performance is investigated by using
polyelectrolytes and clay minerals as coagulant aids in
flocculation step.
Coagulation-flocculation and precipitation studies were
performed in a six-place conventional jar-test apparatus,
equipped with 6 beakers of 500 mL volume. Before
coagulation/flocculation process, wastewater sample was
thoroughly shaken to avoid possibility of settling solids.
The experimental process consisted of the initial rapid
mixing stage that took place for 5 min at 150 rpm, the
following slow mixing stage for 30 min at 30 rpm and the
final settling step for 1 h. After 1 hour settling period,
samples were withdrawn from supernatant for analyses.
Process performance was monitored by using COD
values.
Table 2.Chemical analyses of the clay minerals used in this study
Properties
Unit
By Mass
SiO2
Al2O
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
52.69
12.19
8.63
6.15
4.15
1.92
0.11
0.46
13.86
Specific Surface Area
(m2/g)
538.72
>45 µm
(%)
12.56
>10 µm
(%)
28.82
>2 µm
(%)
48.67
3
Fe2O
3
CaO
MgO
TiO2
K2O
Na2
O
Loss on Ignition
2.Materials and Methods
Wastewater sample was collected from outfall of a
recycling plant located in Dilovası Organized Industrial
Zone, Kocaeli city, Turkiye. In the recycling plant, IBC
tanks, used for storage and transport, are brought for
cleaning of detergent residues before they are used again.
Cleaning is carried out by using high pressurized water
and after cleaning, wastewater containing detergent has to
be treated before it is discharged to sewage system. The
average flow rate of wastewater is about 25 m 3/day.
Wastewater sample collected from the plant was placed in
plastic containers to be transported to the laboratory and
stored at 4 0C in a refrigerator. The composition of the
detergent wastewater is presented in Table 1.
.Experimental studies carried out in three steps. In
the first step, optimum pH for the treatment was
determined. The study was carried out between the pH
values of 4-12. Desired pH values of wastewater were
adjusted by using 6N and 0.1 N H2SO4 and NaOH. In the
second step coagulation-flocculation was performed
between ferric chloride concentration of 0.5-3 g/L and
optimum concentration was investigated. In the last step
polyelectrolyte and clay minerals were added as coagulant
aids for improving process performance and the most
efficient coagulant aid was determined. The
concentrations used in this step were between 5-75 mg/L
for polyelectrolyte and 25-750 mg/L for clay minerals.
Table 1.the composition of detergent wastewater
Parameter
Value
pH
12.31
24.3
Chemical oxygen demand (COD) (g/L)
Biochemical oxygen demand (BOD5) (g/L)
3.2
BOD5/COD
0.05
In this study, two kinds of coagulant aids were used.
One of them was polyelectrolyte (anionic 1858 S)
whereas the other was clay minerals. The clay minerals
used in this study were collected from an area in
Ermenek, Konya City (Turkey). Chemical analyses of the
clay minerals are illustrated in Table 2.
pH, COD, BOD5 were analysed in the laboratory
according to the methods given in the Standard Methods.
pH measurements were done by using the WTW
Multiparameter 340i. Closed reflux colorimetric method
(Method 5220 C) was used for COD analysis and BOD 5
was analysed (Method 5210) as dictated by Standard
Methods [16].
3.Results and discussion
Coagulation-flocculation process was conducted for
the treatment of the detergent influent. Numerous jar tests
were carried out in order to establish a practical
understanding of the coagulation performance and to find
optimum pH, coagulant dosage and coagulant aid dosage.
3.1 Effect of pH on Coagulation
In the coagulation–flocculation process, pH is very
important since the coagulation occurs within a specific
pH range for each coagulant. In this study, a wide range
of pH between 4-12 was selected.
98
The results of the study showing the effect of pH
on COD removal efficiencies and effluent COD
concentrations when FeCl3 was used as a coagulant are
presented in Figure 1. To determine optimum pH value,
FeCl3 dosage was constant at 1.5 g/L. When pH increased
from 4 to 11, COD removal efficiency increased from
34% to 57% and COD concentration of effluent was
10560 mg/L. At higher pH value, COD removal
efficiency decreased. It is clear that optimum pH was 11
for the coagulation-flocculation process at 1.5 g/L FeCl 3
dosage.
pH is an important parameter for coagulation process
since it controls hydrolysis species. When a coagulant
such as aluminum or ferric salt is added to water, a series
of soluble hydrolysis species are formed. These
hydrolysis species have positive or negative charges
depending on the water pH. They are positively charged
at low pH (< 6) and negatively charged at high pH. The positively charged hydrolysis species can absorb onto the surface of colloidal particles and destabilize the stable colloidal particles. This mechanism is called ‘charge neutralization’. A precipitate of aluminum or ferric hydroxide is formed at sufficiently high coagulant dosage. These precipitates can physically sweep the colloidal particles from the suspension. This mechanism is called ‘sweep-floc coagulation’ [17]. In this study, after FeCl 3 addition as a coagulant, mechanism of coagulation showed properties of sweep-floc coagulation due to the high pH in operation. leading to total COD removal of 47%. Mahvi et al. [2] reported that when lime, alum and ferric chloride were used as a coagulant, COD removal resulted in 21%, 37% and 89%, respectively. This results shows that ferric chloride can be noteworthy option and provide higher removal efficiencies than lime, alum and their combinations. Figure 2. Effect of FeCl3 dosages on the effluent COD and COD removal efficiency 3.3 Effect of Polyelectrolyte Polyelectrolytes are commercial coagulant aids. Synthetic polyelectrolytes are currently the most widely used chemicals in the treatment of industrial wastewaters. Generally, a little amount of polyelectrolyte dosage is enough to reach high efficiency. Because of they have some advantages including the possibility of structuration in response to specific requirements, greater purity, higher quality, stability and greater efficiency [19]. With polyelectrolytes as coagulant aids, the metal coagulant dosage can be reduced without cutting down the performance [20]. Yu et al, [21] reported that the charge density and molecular weight of polyelectrolyte play important role in the coagulation. Effluent COD and COD removal efficiencies versus different polyelectrolyte dosages are given in Figure 3. At the lowest concentration of polyelectrolyte, COD removal efficiency was 74% and effluent COD concentration was 6.4 g/L . With increase in polyelectrolyte concentration, removal efficiency increased up to 87%. At a higher concentration than 50 mg/L, effluent COD decreased thus 50 mg/L polyelectrolyte dosage was accepted as optimum dosage. Optimum concentration of polyelectrolyte forms a bridge between particles and cause good flocculation. However high concentration of polyelectrolyte forms an envelope on the suspending particles and causes them to remain in suspension thus removal efficiency decreases [18]. Similar result was obtained from this study and when the polyelectrolyte concentration was increased, process performance was decreased. Figure 1. COD removal efficiency and effluent COD concentrations at different pH values 3.2 Determination of the optimal coagulant dosage Effect of FeCl3 dosages on the COD removal efficiency is shown in Figure 2. Coagulation-flocculation was performed between ferric chloride concentrations of 0.5-3 g/L. At a concentration of 2 g/L, removal efficiency was 71% that was accepted as the optimum dosage. COD removal efficiency decreased by increasing FeCl 3 concentration. At high coagulant doses, metal hydroxides are produced and organic substances are removed by incorporation into or sorption onto hydroxide flocs [18]. According to the study of Papadopoulos et al. [3] use of 1.5 g/L lime in coagulation-flocculation process provided COD removal efficiency of 29%, combination with 1.5 g/L alum improved COD removal up to 18%, 99 Figure 3. Effect of polyelectrolyte dosages on the effluent COD and COD removal efficiency Figure 4. Effect of clay minerals dosages on the effluent COD and COD removal efficiency 3.4 Effect of clay minerals on coagulation Clay minerals may be used as coagulant aids in flocculation step of binding already formed small flocs into larger particles when aluminum or iron salts have been used as the primary coagulant. Coagulation with clay minerals followed by sedimentation can clean up industrial effluent when the flocs formed are dense enough [22]. Effect of clay minerals dosages on the effluent COD and COD removal efficiency is illustrated in Figure 4. When clay minerals used as a coagulant aids in the range of 25-500 mg/L, effluent COD value decreased from 24.3 g/L to 6.08 at minimum clay concentration and to 3.84 g/L at maxium clay concentration Maximum removal efficiency was 84% and obtained at the concentration of 500 mg/L which was accepted as the optimum dosage. Although COD removal was slightly higher at 750 mg/L, the difference was only 1% that can be accepted insignificant. In addition to this, Dilek and Bese [15] reported that the clay addition during alum coagulation had a positive effect on the dewaterability of the sludge in treating pulp-and-paper industry wastewaters. This improvement was more pronounced in combinations with higher clay dosages. In this study, removal efficiencies of clay minerals and polyelectrolyte were similar to each other. Clay minerals are natural and local sources, so when clay minerals and polyelectrolyte used as coagulant aids, if the removal efficiency of each coagulant aid is close to each other, the operation cost of treatment with clay minerals may be lesser than polyelectrolyte. In the study of Demirci et al. [18], the results were shown clearly and the cost of the annual waste water treatment of 2.16x106 m 3 using the common coagulant alum together with clay or polyelectrolyte was calculated. The results indicated that the cost in the treatment with clay was about 50 000 dollars whereas it was about 1 600 000 dollars in the treatment with polyelectrolyte. 4. Conclusion In treatment of detergent wastewater that contains relatively high COD and low BOD, coagulation process can be used as a pretreatment process. In this study, FeCl3 had the lowest COD removal efficiency when it was used alone and it was determined that addition of polyelectrolyte and clay minerals to FeCl 3 as coagulant aids, improved the COD removal efficiency. The highest removal efficiency was obtained from the combination of FeCl3 with clay minerals. Comparing all the results and possibilities, using clay minerals as coagulant aid accompanied with FeCl3 can be advisable and more economical option for the treatment of detergent wastewater since it has similar removal efficiency compared with polyelectrolyte and more economic. REFERENCES [1] Kowalska I., Kabsch-Korbutowicz, M., Majewska-Nowak, K., Pietraszek, M., Removal of Detergents from Industrial Wastewater in Ultrafiltration Process, Environment Protection Engineering, Vol.31, No. 3-4, pp. 207-219, 2005. [2] Mahvi, A.H., Maleki, A., Roshani, B., Removal of Anionic Surfactants in Detergent Wastewater by Chemical Coagualation, Pakistan Journal of Biological Sciences, Vol. 7, No. 12, pp. 22222226, 2004. [3] Papadopoulos, A., Savvides, C., Loizidis, M., Haralambous, K.J., Loizidou, M., An assessment of the quality and treatment of detergent wastewater, Water Science and Technology, Vol. 36, No. 2-3, , pp. 377-381, 1997. [4] Aboulhassan, M. A., Souabi, S., Yaacoubi, A., Baudu, M., Removal of surfactant from industrial wastewaters by coagulation flocculation process, International Journal of Environmental Science and Technology, Vol. 3, No. 4, pp. 327-332. 2006. [5] Dhouib, A., Hamad, N., Hassaïri, I. and Sayadi, S., Degradation of Anionic Surfactants by Citrobacter Braakii, Process Biochemistry, Vol. 38, pp. 1245-1250, 2003. 100 [6] Amuda, O.S., Amoo, I.A., Coagulation /flocculation Process and Sludge Conditioning in Beverage Industrial Wastewater Treatment, Journal of Hazardous Materials, Vol. 141, No. 3, , pp. 778-783, 2007. [7] Papic, S., Koprivanac, N., Bozic, A. L., Removal of Reactive Dyes from Wastewater Using Fe(III) Coagulant, Coloration Technology, Vol. 161, No. 11, pp. 352–358, 2000. [8] Errais, E., Duplay, J., Darragi, F., Textile Dye Removal by Natural Clay – Case Study of Fouchana Tunisian Clay, Environmental Technology, Vol. 31, No. 4, pp. 373-38, 2010. [9] Yilmaz, T., Apaydin, S., Berktay, A., Coagulation-Flocculation and Air Stripping as a Pretreatment of Young Landfill Leachate, The Open Environmental Engineering Journal, Vol. 3, pp. 42-48, 2010. [10] Genovese C.V., González, J. F., Solids Removal by Coagulation from Fisheries Wastewaters, Water SA, Vol. 24, No. 4, pp. 371372, 1998. [11] Odegaard, H., Optimised Particle Separation in the Primary Step of Wastewater Treatment, Water Science and Technology, Vol. 37, No. 10, pp. 43-53, 1998. [12] Alpaslan, M.N., Dolgen, D., Akyarli, A., Liquid Waste Management Strategies for Coastal Areas, Water Science and Technology, Vol. 46, No. 8, pp. 169-175. 2002. [13] Ingram, D.S., Vince-Prue, D., Gregory, P.J., Science and the Garden: The Scientific Basis of Horticultural Practice. Blackwell Science Ltd., Oxford, 2003. [14] Hascakir, B., Dolgen, D., Utilization of Clay Minerals in Wastewater Treatment: Organic Matter Removal with Kaolinite, Ecology, Vol. 66, pp. 47-54,2008 [15] Dilek, F.B., Bese, S., Treatment of pulping effluents by using alum and clay-Colour removal and sludge characteristics, Water SA, Vol. 27, No. 3, pp. 361-366, 2001. [16] APHA, AWWA, WEF, Standard Methods for the Examination of Water and Wastewater (21th edition) Washington: APHA, AWWA, WPCF, 2005. [17] Kim, S.H., Moon, B.H., Leeb, H.I., Effects of pH and Dosage on Pollutant Removal and Floc Structure During Coagulation, Microchemical Journal, Vol. 68, No. 2-3, pp. 197-203. 2001. [18] Demirci, S., Erdogan, B., Ozcimder, R., Wastewater Treatment At The Petroleum Refinery, Kirikkale, Turkey Using Some Coagulants And Turkish Clays As Coagulant Aids, Water Research, Vol. 32, No. 11, 3495-1499, 1998. [19] Aguilar, M.I., Saez, J., Llorens, M., Soler, A., Ortuno, J.F., Meseguer, V., Fuentes, A., Improvement of Coagulation– Flocculation ... Purchase answer to see full attachment

How it works

1. Paste your instructions in the instructions box. You can also attach an instructions file
2. Select the writer category, deadline, education level and review the instructions 
3. Make a payment for the order to be assignment to a writer
4.  Download the paper after the writer uploads it 

Will the writer plagiarize my essay?

You will get a plagiarism-free paper and you can get an originality report upon request.

Is this service safe?

All the personal information is confidential and we have 100% safe payment methods. We also guarantee good grades