Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 170-174

170

Optimization of Coagulation/Flocculation for Treatment of

Wastewater

Abdolreza Karbassi, Maryam Pazoki

Department of Environment, University of Tehran, Tehran, Iran

Received: 19/04/2015 Accepted: 08/06/2015 Published: 30/06/2015

Abstract

One of the industrial areas in the south of Iran is Bandar Imam Petrochemical Economic Zone which has a lot of

petrochemical complex, Farabi Petrochemical complex is one of those places. Coagulation/flocculation could be a typical

methodology in water and wastewater treatment that a number of chemicals are added to assist the coagulation/flocculation and

causes to the sedimentation. In this paper, the sampling and measurement of characteristics wastewater containing turbidity, pH,

COD, TDS and etc. were done, also Efficiency of coagulant was assessed in terms of the COD, TDS and turbidity also the

optimum concentration to determine the coagulant and the pH effluent were investigated.The results show that the optimum

coagulants for decreasing organic matters of wastewater, the amount of coagulant is 10mm per liter of wastewater. With this

amount can be reduced by more than 50% of COD.

Keywords: Wastewater, effluent, Farabi Petrochemical complex, coagulant, jar test

1 Introduction

Industrial wastewater containing organic material

which enters to the groundwater or surface water is an

environmental concern. Due to characterization of these

pollutants such as non-biodegradable, high toxicity,

cumulative and carcinogenic effects are considered.

Discharge of effluents containing organic material is not

only harmful to aquatic life and plants, but also, is very

dangerous due to ecosystem changes [1].

Due to the increasing applications of petrochemical

products, destructive and negative effects on the

environment caused by the production of wastewater, solid

waste and gas emissions to the environment should be

considered.

Coagulation/flocculation could be a typical methodology in

water and wastewater treatment [2, 3, 4& 5] that a number

of chemicals are added to assist the

coagulation/flocculation and causes to the sedimentation.

Mentioned chemical materials are sodium hydroxide to

regulate the pH range, metallic ions and commercial

anionic or cationic-based poly-electrolytes (PEs) [6].

Coagulation process was found to be economical, easy

to work and uses less energy than various treatment

methods. Coagulation is extensively utilized in several

water treatment plants and has been found to be desirable in

the treatment of wastewaters from petroleum refineries and

industrial treatment plant [7, 8].

In recent years, due to vast oil and gas resources in the

country and and the government's economic policies, the

petrochemical industry has developed considerable, and

Corresponding author: Maryam Pazoki, Department of

Environment, University of Tehran, Tehran, Iran.

E-mail: mpazoki@ut.ac.ir

Recent research has strongly implies that the Persian Gulf

is seriously polluted with toxic metals and oil.

In recent years, in many parts of the country, using

wastewater for irrigation of farmlands in most cases due to

lack of water and increasing of wastewater is inevitable [9].

The management of wastewater and leachate from landfill

for irrigation or using energy leads to costs reduction. [10,

11] Also, it would increase agricultural production,

especially in dry climates and less water situation. With

respect to the notes, the development of green space is one

of the advantages of the effluent [12].

Considering shortage of water in arid and semi-arid

areas, reusing of unconventional water including municipal

and industrial wastewater and at the same time in

compliance with environmental considerations, is

necessary. For reusing of wastewater in different parts,

quality of wastewater effluent and standards should be

considered [13]. Presence of heavy metals in wastewater

treatment and the accumulation of these metals, especially

cadmium and lead in soil, are considered as important

environmental issues [14].

In the present study, at first the quantity of the

wastewater after each stage and the amount of overall

wastewater was analyzed. Efficiency of coagulant was

assessed in terms of the COD, TDS and turbidity also the

optimum concentration to determine the coagulant and the

pH effluent were investigated.

2 Materials and Methods

In this study, firstly identifying of Farabi

petrochemicals production process, consumables chemicals

and research for identifying the amount of wastewater

production at each stage and whole process was

investigated. Then, the sampling and measurement

characteristics of wastewater are done that containing pH,

Journal web link: http://www.jett.dormaj.com

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 170-174

171

COD, TDS, … and the effectiveness of coagulant test (poly

aluminum chloride) and jar test was studied to determine

the optimum concentration of coagulant and suitable pH

range for the final wastewater. It should be mentioned that,

the tests were carried out according to the APHA standard

[15]. All tests were repeated three times and the mean

values are showed in this paper.

2-1- specifications of the region under study

2-1-1- Farabi petrochemical facility specifications

Farabi petrochemicals department with an area of 20

acres on the northwest side of the Persian Gulf, port of

Imam Khomeini and in the vicinity of Imam Petrochemical

port, Razi and at petrochemical special economic zone are

located.

Now, in this department, wastewater without any

settling was entered in Khor Mousa River and then Persian

Gulf. According to the carcinogenic of food and substances

productive and since the fish, birds, plant tissue and finally

human are in danger so it is necessary for wastewater

settling and disposal of organic materials. Figure 1 shows

map of khor mousa and Farabi complex and Figure 2 shows

Wastewater treatment process diagram.

2-2- Characteristics of wastewater

Characteristics of total wastewater have been measured.

Wastewater flow was 720 m

/day and temperature of

wastewater was 250 C. table 1 shows characteristics of

total wastewater.

Fig.1- Khor Mousa and Farabi complex

Table 1- Characteristics of wastewater

Fecal Coliform (Mpv/100 ml)

s/cm

Total Hardness

(CaCO

) mg/l

TDS

mg/l

BOD

mg/l

COD

mg/l

1100

3878

6.8

700

2000

800

2677

0.1

2-3- Sampling

The effluent samples were collected from Farabi

Petrochemical wastewater discharge to the Khor Mousa

rever.

Sampling and measurements of various characteristics of

wastewater were conducted in according to the standard

methods for the examination of treated water and

wastewater [15].

2-4- Jar tests

The jar test was used to optimize the addition of

coagulants and flocculants and poly aluminum chloride

coagulant were utilized in different dose. For coagulation

test, 200 rpm was used for mixing in five minutes and for

flocculation, slow mixing rate (40 rpm) was used for five

minutes also settling time was 30 minutes. Two series of jar

tests were taken accordance with the standard test methods

[16].

3 Results and Discussion

In this section the results of water quality and quantity

of the wastewater and effectiveness of the coagulant (poly

aluminum chloride) were provided then the jar test were

done to determine the optimum concentration of coagulant

and a suitable pH range for maximum efficiency.

3-1- Results of quality and quantity of wastewater

The following chart compares the volume of

wastewater produced and COD effluent compared to the

output in the different processes.

Figure 3 shows that highest amount of organic material

is related to the washing process. Esterification, recycling

and dewatering stages have an organic load between 3000-

4000 mg/l.

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 170-174

172

Figure 2: Wastewater treatment process diagram

Figure 3: comparing of effluent COD in different processes

According to Figure 4, the maximum volume of

wastewater production are form resin restoration, road

washing, backwashing of sand filters and steam traps

respectively.

3-2- Effect of coagulants on wastewater

Table 2 shows the results of the effect of coagulants on

the removal of COD and turbidity. As can be seen, removal

percentage of COD and turbidity was 38% and 99%

respectively, which both test results were acceptable.

3-3- Jar test results

Sampling (6 samples every 2 hours, 1 liter for each time)

was done from the second pond of treatment plant.

COD and TDS of the raw wastewater were 1870 and 3290

mg/l also in pH of 6.4, turbidity was 970 NTU. Jar test No.

1 shows the optimum pH in a fixed dose of coagulant.

According to the table 2, the best result for COD removal is

occurred in pH of 9. Jar test number 3: shows the optimum

dose of coagulant – in a fixed pH. According to the table 4

the best dose of coagulant is 10ml. Jar test No. 3 shows the

optimum pH in the fixed optimum dose of coagulant with a

higher pH.

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

COD (mg/l)

Process

Esterification

Alkaline wash

Alcohol recovery

Washing

Dewatering

DOP

Sand filters for cooling towers

Sand filter for water treatment

Resin restoration

Road washing

Steam Traps

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 170-174

173

Figure 4: comparing of wastewater production volume (liters per hour) in the effluent of processes

Table 2: Results of coagulants tests on wastewater

Sample

Turbidity NTU

EC (µs/cm)

TDS (mg/l)

T(°C)

COD (mg/l)

TSS (mg/l)

Control

8.5

461

4875

2830

29.5

1060

1540

6 cc coagulants

7.55

5158

3010

29.8

673

10 cc coagulants

7.06

4.6

5565

3260

29.1

684

Table 3- Jar test results – fixed dose of coagulant –sample temperature: 15 C°

Sample

Coagulants

primary

Turbidity

NTU

TDS

mg/l

Final pH

COD

mg/l

Reduction% COD

Sludge volume

ratio

160

4160

1270

Normal

240

4260

4.1

1235

Normal

7.5

213

2200

4.1

1310

Normal

3310

4.4

810

High

Table 4- Jar tests result- fixed pH, sample temperature: 15 C°

Sample

Coagulants

(%)

primary

Turbidity

NTU

TDS

mg/l

Final

COD

mg/l

Reduction

(%) COD

Sludge

volume ratio

0.01

3820

6.69

1640

Normal

0.02

3260

5.25

1120

High

0.05

105

3240

4.34

910

High

0.07

167

3390

4.14

1120

Normal

Table 5: Jar test results - optimum dose of coagulant - sample temperature 15 C°

Sample

Coagulants

primary

Turbidity

NTU

TDS

mg/l

Final

COD

mg/l

Removal

percentage

Volume ratio of

sludge

210

2240

4.1

1320

Normal

3298

4.4

821

Normal

120

3100

4.5

952

High

138

3207

4.7

998

High

According to the table 5 the best range of pH for maximum

COD removal is 9. According to the results obtained in the

three jar test, it can be said that the experimental error was

less than 10%.

4 Conclusions

At analyzing of output characteristics of wastewater

over a period of 6 months, was determined that in most

cases, organic pollution is far more than the designed

(COD=2677mg/l), so serious attempt should be made to the

wastewater production volume (l/h)

Process

Esterification

Alkaline wash

Alcohol recovery

Washing

Dewatering

DOP

Sand filters for cooling towers

Sand filter for water treatment

Resin restoration

Road washing

Steam Traps

Journal of Environmental Treatment Techniques 2015, Volume 3, Issue 2, Pages: 170-174

174

wastewater settling. Because the system of DOP production

is a batch system and because the current volume of

wastewater storage tank (90m3), every day at least 8 times

wastewater is discharged in to the Khor. And a simple

sampling can’t determine the characteristics of outcome

wastewater so composite sampling is required. In this

study, the effect of chemical coagulation by poly-aluminum

chloride coagulants of on wastewater as pre-settling was

tested in the laboratory. According to the current test results

indicate that the optimum coagulants for decreasing organic

matters of wastewater, the amount of coagulant is 10mm

per liter of wastewater. With this amount can be reduced by

more than 50% of COD. According to the wastewater

production rate at the maximum (currently) 700 cubic

meters per day, in this case for pre-settling 7000 liters of

coagulant 2% or 1000 liters of coagulant 14% should be

consumed.

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