Feasibility study of wastewater treatment in specialty chemical plants

APPROVAL SHEET

INDIVIDUAL ASSIGNMENT REPORT

TK 4090 INTERNSHIP

SEMESTER I 2014/2015

Annisa Mienda Chintyarani (13011071)

Note/comment :

Internship Location : Map Tha Put Industrial Estate, Rayong, Thailand.

Internship Period : May 22nd

2014 July 31st 2014

Has been examined and approved by:

Mentor Advisor

Supranee Kanokwajamrus

Senior Process Engineer

Dr. Dwiwahju Sasongko

Date : _____________ Date :____________

i

PREFACE

The author would like to acknowledge her countless thanks to the Most Gracious and the Most

Merciful, Allah SWT who always gives their all the best of this life, so the author is able to

complete the internship and its report during May 22nd

2014 July 31st 2014 in PTT Global Chemical Company Limited. Shalawat and Salaam to the Prophet Muhammad SAW and his

family. This script is presented to fulfill one of the requirements in accomplishing the Bachelor

Degree at Chemical Engineering Department, Faculty of Industrial Technology, Institut

Teknologi Bandung.

The authors would like to take their opportunity to express their deep and sincere gratitude to the

following:

1. Dr. Dwiwahju Sasongko, as the advisor who has guided the authors patiently during the internship period

2. Dr. IGBN Makertihartha, as the coordinator of TK4090 Internship 3. Nittaya Boonyarit, as Process Engineer Manager in PTT Global Chemical 4. Supranee Kanokwajamrus, as Senior Process Engineer as well as authors mentor from

Process Engineer Division in PTT Global Chemical.

In addition, author would also thank others who give their full help and support during the

internship, they are:

1. Dilok Tuekla, as Vice President of Human Resources PTT Global Chemical Company who gave an opportunity for us to get new experience throughout this internship program

2. Supat Arunlerktawin, as Manager of Training Center Management PTT Global Chemical Company

3. Kammasit Wichitphan, as HR Officer at PTT Global Chemical Company 4. Jaratsri Rakkaew, as Senior HR Officer at PTT Global Chemical Company 5. Sirinun Sirisaard, as HR Officer PTT at Global Chemical Company 6. Kevin Wun, as Internship Manager at PTT Global Chemimal 7. All employees in PTT Global Chemical Company 8. All family in Bandung who always give support during internship program.

This report is not perfect and is open for corrections. Hope it will be useful for the readers.

Rayong, 31st July 2014

Author

ii

TABLE OF CONTENTS

CHAPTER I .................................................................................................................................... 1

INTRODUCTION ........................................................................................................................... 1

1.1 Background ............................................................................................................................ 1

1.2 Objectives .............................................................................................................................. 1

1.3 Scopes of work ...................................................................................................................... 1

CHAPTER II ................................................................................................................................... 2

LITERATURE ................................................................................................................................ 2

2.1 The importance of wastewater treatment ............................................................................... 2

2.2 Wastewater treatment selection ............................................................................................. 2

2.3 Physical, biological, and chemical wastewater treatment ..................................................... 4

2.4 General PO/SM, polymer polyol, and polyether polyol plants wastewater characteristics . 5

CHAPTER III .................................................................................................................................. 6

METHODOLOGY .......................................................................................................................... 6

CHAPTER IV .................................................................................................................................. 7

RESULTS AND DISCUSSION ..................................................................................................... 7

4.1 Wastewater Characteristics .................................................................................................... 7

4.1.1 Wastewater sources ......................................................................................................... 7

4.1.2 Wastewater composition ................................................................................................. 7

4.1.3 Wastewater classification .............................................................................................. 10

4.2 Available Technology for Wastewater Treatment ............................................................... 11

4.2.1 Technology for high polluted and low polluted stream .......................................... 11

4.2.2 Technology for salt stream ...................................................................................... 29

4.3 Technology Selection .......................................................................................................... 37

CHAPTER V ................................................................................................................................. 41

CONCLUSIONS AND RECOMMENDATIONS ........................................................................ 41

5.1 Conclusions.......................................................................................................................... 41

5.2 Recommendations ................................................................................................................ 41

APPENDIX A ............................................................................................................................... 42

REFERENCES .............................................................................................................................. 44

iii

TABLE OF FIGURES

Figure 2.1 Wastewater treatment method selection ........................................................................ 3

Figure 2.2 Inhibitory compounds for biological treatment ............................................................. 5

Figure 3.1 Workflow diagram of feasibility study .......................................................................... 6

Figure 4.1 Wet air oxidation process ............................................................................................. 13

Figure 4.2 Scheme of ozone oxidation process ............................................................................. 14

Figure 4.3 Repsol PACT system unit ......................................................................................... 15

Figure 4.4 Comparison between external and internal membrane configuration ......................... 17

Figure 4.5 Process scheme of external membrane system in Commune De Monteux WWT ...... 18

Figure 4.6 Oxidation ditch system ................................................................................................ 20

Figure 4.7 Block diagram of TAR system .................................................................................... 25

Figure 4.8 Schematic figures of multiple hearth (left) and fluidized bed (right) .......................... 30

Figure 4.6 Block diagram of Ozone oxidation-MBR system ........................................................ 32

Figure 4.7 Block diagram of Fenton oxidation-oxidation ditch .................................................... 32

Figure 4.9. Schematic diagram of electrodialysis reversal system ................................................ 35

iv

TABLE OF TABLES

Table 4.1 Summary of wastewater characteristic from POSM, Polyether Polyol, and polymer

polyol unit ........................................................................................................................................ 8

Table 4.1 Summary of wastewater characteristic from POSM, Polyether Polyol, and polymer

polyol unit (contd.) .......................................................................................................................... 9

Table 4.2 Wastewater classification .............................................................................................. 10

Table 4.2 Wastewater classification (contd.) ................................................................................ 11

Table 4.3 Required wastewater specification to discharge to Hemmaraj ..................................... 11

Table 4.4 Summary of single wastewater treatment method ........................................................ 20

Table 4.5 Reference plants and vendors of single methods .......................................................... 21

Table 4.5 Reference plants and vendors of single methods (contd.) ............................................. 22

Table 4.6 Summary of TAR system .............................................................................................. 24

Table 4.7 Summary of ozone oxidation MBR system ............................................................... 26

Table 4.8 Summary of ozone oxidation MBR system ............................................................... 27

Table 4.9 Summary of Fenton oxidation oxidation ditch system ............................................... 29

Table 4.10. Comparison between fluidized bed and multiple hearth ............................................ 33

Table 4.11 Strengths and weaknesses of thermal oxidation system .............................................. 33

Table 4.12 Summary of technical and economic information about thermal oxidation system ... 34

Table 4.13 Summary of technical and economic information of EDR system ............................. 36

Table 4.14 Scoring of wastewater treatment method .................................................................... 39

Table 4.14 Scoring of wastewater treatment method (cotd.) ........................................................ 40

Table 4.15 Summary of HPW & LPW treatment methods ........................................................... 41

Table 4.15 Summary of HPW & LPW treatment methods (contd.) ............................................. 42

Table 4.16 Summary of salt treatment methods ............................................................................ 42

Table 4.16 Summary of salt treatment methods (contd.) .............................................................. 43

Table 4.17 Scoring result of HPW and LPW treatment methods ................................................. 44

Table 4.17 Scoring result of HPW and LPW treatment methods (contd.) .................................... 45

Table 4.18 Scoring result of salt stream treatment methods ......................................................... 46

Table 4.18 Scoring result of salt stream treatment methods (cotd.) .............................................. 47

1

CHAPTER I

INTRODUCTION

1.1 Background

As environmental issue has been spread widely all over the world, people are now more concern

to the life of environment. One of the efforts that they do to save the environment is by reducing

waste that is dumped to the surroundings. This waste reducing effort is undertaken by various

parties, including industries which its activities are one of the largest waste producers in the

world.

PTT Global Chemical is an industry that has high concern to the life of environment. Though its

running production process definitely produces waste, PTTGC always strives to meet

specification of waste disposal. One of the projects that has been carried out recently by process

engineers in this company is about the propylene oxide, polyether polyol, and polymer polyol

plants, including its wastewater treatment system. Due to their concern on waste and

environment, they are striving to look for the best wastewater treatment method that could

reduce the wastewater contaminants and minimize its adverse impact on environment.

1.2 Objectives

The objectives of this feasibility study are:

1. To explore available methods for treating propylene oxide, polymer polyol, and polyether

polyol plants wastewater

2. To recommend commercially available technology for the selected method

3. To propose technology and vendor for treating the wastewater

4. To propose the most suitable method/technology for treating the wastewater

1.3 Scopes of work

The scopes of work of this feasibility study are:

1. Identify the PO, polyether polyol, and polymer polyol plants wastewater characteristics

2. Determine the general wastewater treatment process based on the wastewaters characteristics

3. Explore the information of the available wastewater treatment methods

4. Compare and select the most suitable wastewater treatment method based on specified criteria

5. Explore the information of the selected methods licenses

6. Compare and select the most suitable license for the selected method based on specified

criteria

2

CHAPTER II

LITERATURE

2.1 The importance of wastewater treatment

Across the world, there continues to be huge volumes of wastewater pumped directly into rivers,

streams and the ocean. The impact of this is severe, aside from the damage to the marine

environment and to fisheries it, it does little to preserve water at a time when many are predicting

that a global shortage is just around the corner.

As it stands this method of disposing of wastewater any form of water that has been

contaminated by a commercial or domestic process, including sewage and byproducts of

manufacturing and mining is largely an issue in developing nations. The regulation of waste

disposal in developing nations is seems not too firm, especially in monitoring the maximum

amount of wastewater contaminants that discharged by the industries. In the other hand, perhaps

the waste water treatment technology itself is still not capable to provide safe and

environmentally friendly treated water due to the high cost of installation and operation of

sophisticated wastewater treatment system. As an example, The World Bank estimated that

Vietnam will need an investment of $8.3 billion in order to provide the necessary wastewater

services (Wright, 2014). The underdeveloped wastewater treatment technologies and lack of

regulation regarding wastewater disposal are indeed threats to the environmental sustainability. If

such situation keep abandoned, we will probably no longer have water to use in everyday life.

When water is used by our society including industrial activities, the water becomes

contaminated with pollutants. If left untreated, these pollutants would negatively affect the water

and environment. For example, organic matter can cause oxygen depletion in lakes, rivers, and

streams. This biological decomposition of organics could result in fish kills and/or foul odors.

Nutrients in wastewater, such as phosphorus, can cause premature aging of the lakes, called

Eutrophication. Additionally, there are many pollutants that could exhibit toxic effects on aquatic

life and the public. Therefore, pollutants must be removed from the water to protect the

environment and public health.

2.2 Wastewater treatment selection

The applied wastewater treatment method actually depends on the characteristics of the

wastewater itself. Different characteristics of wastewater will result in different wastewater

treatment method. Therefore, it is important to determine the characteristics of the wastewater

before deciding which wastewater treatment is best to be applied.

Selecting wastewater treatment method based on wastewater characteristics is carried out

through the steps shown in Figure 2.1.

3

Figure 2.1 Wastewater treatment method selection

(Source: Setiadi, 2014)

Aliran air limbah

Inorganik Organik

Pretreatment

Insinerasi atau wet

air oxidation

ya

ya

ya

ya

ya

Off-gas treatment

Limbah Padat

Filter atau

regenerasi media

adsorpsi

Solid / Concentrated Phase

Perlunya

Pretreatment

untuk netralisasi

tidak

Dapat

terbiodegradasi

Perlunya

pretreatment

penghilangan

minyak dan lemak

Tersedia ruang

lahan yang luas

Perlunya aerasi

Perlunya solids

recovery

Kolam ekualisasi

tidak

tidak

ya

tidak

ya

Air / Steam

Stripping

Koagulasi,

flokulasi, dan

sedimentasi

Filtrasi atau

Adsorpsi karbon

aktif

Evaporasi atau

ekstraksi

Pemisahan minyak

/ air

Trickling filter

atau Fixed-film

Biotreatment

Lumpur aktif atau

aerated lagoon

Anaerobic

treatment

ya

ya

tidak

yaMengandung

kontaminan yang

dapat di-stripping

mis. amonia

Mengandung

kontaminan yang

dapat dipresipitasi

Mengandung

kontaminan yang

dapat disaring atau

diadsorb

Limbah dapat

dimanfaatkan

kembali atau

direduksi

volumenya

Limbah harus

dihancurkan

tidak

tidak

tidak

tidak

Mengandung

kontaminan yang

dapat di-stripping

Mengandung

kontaminan yang

dapat disaring atau

diadsorb

Limbah dapat

dimanfaatkan

kembali atau

direduksi

volumenya

Limbah harus

dihancurkan

tidak

tidak

tidak

tidak

Mengandung

kontaminan yang

dapat dioksidasi

atau direduksi

secara kimia

minyak

tidak ya

ya

ya

ya

Insinerasi atau wet

air oxidation

Air / Steam

Stripping

Oksidasi / reduksi

kimia

Evaporasi atau

ekstraksi

Solid / Concentrated Phase

Filtrasi atau

Adsorpsi karbon

aktif

Filter atau

regenerasi media

adsorpsi

Off-gas treatment

Wastewater stream

Inorganic Organic

Requires

pretreatment for

neutralization

Contains

contaminants that

can be stripped

Contains

contaminants that

can be

precipitated

Contains

contaminants that

can be filtered or

adsorbed

Waste can be reused

or its volume can be

reduced

Destroy the waste Incineration

Evaporation or

extraction

Filtration/activated

carbon adsorption

Coagulation,

flocculation,

sedimentation

Solid waste

Filter /

adsorption

Biodegradable

Needs

pretreatment to

remove oil &

grease

Large land area is

available

Requires aeration

Requires solids

recovery

Equalization tank

Activated sludge /

aerated lagoon

Tricking filter / fixed

film biotreatment

Oil water

separation

Contains

contaminants that

can be stripped

Contains

contaminants that

can be filtered or

adsorbed

Filtration/activated

carbon adsorption

Filter /

adsorption

Contains

contaminants that

can be chemically

reduced or

oxidized

Chemical

oxidation/reduction

Waste can be reused

or its volume can be

reduced

Destroy the waste Incineration

Evaporation /

extraction

No

Oil

No

No

No No

No

No

No No

No

No

No

No

4

2.3 Physical, biological, and chemical wastewater treatment

Physical wastewater treatment methods include processes where no gross chemical or

biological changes are carried out and physical phenomena are used to treat the

wastewater. Physical methods are usually carried out in order to remove large entrained

object in the wastewater such as solids. Examples of physical wastewater treatment

method are screening, sedimentation, clarification, filtration, and many others. Physical

treatment is usually carried out at the preliminary step of wastewater treatment before the

wastewater is routed to the next treatment steps.

Biological wastewater treatment is a method to treat wastewater by biological activity,

mostly microorganisms. Biological treatment is an important part of any wastewater

treatment plant that treats wastewater from either municipality or industry having soluble

organic impurities or a mix of two types of wastewater sources. Compared to chemical

treatment, biological treatment has more obvious economic advantage, both in terms of

capital investment and operating cost.

Although biological treatment seems economically promising, there are stringent

requirements for wastewater that will be treated biologically. The main requirement is that

the wastewater has to meet a certain amount of biological oxygen demand and chemical

oxygen demand ratio (BOD/COD). Wastewater with BOD/COD ratio is less than 0.1

shows that the wastewater is hard to be treated biologically. Therefore, the wastewater

should be treated by other method first before sent to biological treatment in order to

increase its BOD/COD ratio. A BOD/COD ratio of 0.4 0.6 shows that the wastewater

should be treated by aerobic biological treatment, which involves contacting wastewater

with microbes and oxygen to optimize the growth and efficiency of biomass. Wastewater

with BOD/COD ratio >0.6 shows that it should be treated by anaerobic biological

treatment which does not require addition of oxygen.

In biological treatment, the performance of the treatment is dependent upon the activity of

microorganisms and their metabolism which can be dramatically affected by toxic

compounds in the wastewater. Many materials such as organic and inorganic solvents,

heavy metals, and biocides can inhibit the biological activity in the treatment plant. Figure

2.2 lists inhibitory levels reported for some metals, inorganic, and organic substances

which affect the effectiveness of biological treatment.

If wastewater has low BOD/COD level and/or contains inhibitory compound which makes

it infeasible to be treated by biological treatment, then other options of wastewater

treatment needs to be carried out. One promising option is by chemical treatment, which

consists of using chemical reactions to improve the wastewater quality. Chemicals used in

chemical treatment are usually strong oxidizers such as chlorine, hydrogen peroxide,

ozone, and many others. Such oxidizers can remove nearly all contaminants in the

wastewater, including materials that are recalcitrant or even refractory to biological

treatment.

5

Contrary to biological treatment, influent requirements to enter chemical treatment are not

as stringent as biological treatment. However, the cost of chemical treatment is usually

higher, especially to treat highly contaminated wastewater.

Figure 2.2 Inhibitory compounds for biological treatment

(Source: Wastewater Treatment Manuals, 1997)

2.4 General PO/SM, polymer polyol, and polyether polyol plants wastewater

characteristics

In general, one of major wastewater sources in PO/SM, polymer polyol, and polyether

polyol plant is the alkaline washing unit. This alkaline washing produces an aqueous

stream, also called alkaline purge, highly loaded in organic compounds and sodium which

can be taken integrally to water treatment, without any prior pre-treatment, which permits

the recovery of organic matter. The typical composition of the alkaline purge is included

between values of 4 and 8% of compounds of alcoholic nature, largely monopropylene

glycol and methylbenzyl alcohol, between values of 3 and 6% of organic salts, largely

sodium benzoate and phenolate and a content greater than 2% of sodium hydroxide.

The purification treatment of waste water arising in the process of PO/SM, polyether

polyol, and polymer polyol is very expensive, mainly due to three aspects: its high content

in organic matter which is translated into a high value of the chemical oxygen demand

(COD greater than 40% by weight), the high flow of said stream and, finally, the fact that

it contains organic compounds which are not easily degradable.

6

CHAPTER III

METHODOLOGY

The main objective of this feasibility study is to determine the most suitable commercial

wastewater treatment method to treat wastewater from PO/SM, polyether polyol, and

polymer polyol plant. The objectives can be achieved through the following steps:

1. Studying wastewater characteristics

The aim of wastewater characteristics study is to determine the characteristics of the

wastewater. The wastewater characteristic is determined through studying data of

wastewaters contaminants.

2. Studying commercially available technology for the wastewater treatment

After determining characteristic of the wastewater, study about commercially available

technologies that are possible to treat the wastewater is carried out. These technologies

are further selected based on specified criteria to determine which technologies are the

best to be applied in the wastewater treatment system.

3. Technology selection

Selecting wastewater treatment technology is carried out through scoring. Before

scoring, criteria for selecting the wastewater treatment methods are determined. Those

criteria are then being scored based on the wastewater treatment data from the study.

Each criteria will contribute a certain percentage to the overall score. Method that has the

highest score will be considered as the most suitable wastewater treatment method. A

workflow diagram of this feasibility study is shown below.

Figure 3.1 Workflow diagram of feasibility study

Studying wastewater

characteristic

Wastewater

characteristic

Start

Studying commercially

available technology

Commercially

available

technologies

Technology selection The most suitable

wastewater treatment

method

Finish

7

CHAPTER IV

RESULTS AND DISCUSSION

4.1 Wastewater Characteristics

4.1.1 Wastewater sources

The wastewater given in this case comes from three main units. These units are Propylene

Oxide/Styrene Monomer (POSM) Unit, Polyether Polyol (PoP) Unit, and Polymer Polyol

(PoP) Unit. More detailed information about the wastewater coming from each unit is

described below:

1. Propylene Oxide/Styrene Monomer (POSM) Unit

The POSM Unit generates five streams of wastewater. These streams are Highly Polluted

Water (HPW), Acid Purge (AP) Stream, Low Polluted Water (LPW), rain water, and

laboratory residual stream. The HPW is a caustic wastewater generated from washing

section and dehydration reaction in POSM unit, while the AP stream is generated in the

oxidation section. The LPW comes from final emptying of equipment that could not be

pumped out.

2. Polyether Polyol (PeP) Unit

The Polyol Unit consists of two subunits: Flexible and Rigid & CASE Unit. Each subunit

generates five streams of wastewater namely HPW, LPW, rain water, laboratory residual

stream, and by-product (high salt) stream. However, though the types and composition of

the stream from both subunits are identical, the flow rate is different between one and

another.

3. Polymer Polyol (PoP) Unit

The polymer polyol unit generates two types of wastewater: highly polluted water (HPW)

and low polluted water (LPW). The HPW comes from monomers recovery system and

condensate vacuum system. The LPW consists of liquid from final emptying of equipment,

rain water collected from process area, effluent from gas abatement device, and laboratory

residual stream.

4.1.2 Wastewater composition

The composition of wastewater that is generated in each unit is summarized in Table 4.1.

8

Table 4.1 Summary of wastewater characteristic from POSM, Polyether Polyol, and polymer polyol unit

(Source: OSBL Basis Design Data for Repsol, 2014)

Unit Type Flow rate (m

3/h)

Temperature (oC)

Contaminants (mg/l) Note

Normal Max pH COD BOD SS Oil TDS

Propylene

Oxide-

Styrene

Monomer

(POSM)

Highly Polluted Water

(LPW) 27-32 32

Depends on the waste

water stream (usually

30-40C from the

washing sections).

The storage tank for

this streams usually

operates between 15-

20C

13-14 180,000 -

200,000 4-5

Using either

biological waste

water

treatments and

incinerator Acid Purge (AP) Stream 5.7 6.7 6.7 75 1.8-2 75,000

Low Polluted Water

(LPW)

Rainwater

Laboratory residual

stream

Polyether

Polyol

(Flexible)


(LPW) 0.07 12-14 46% 21%

Low Polluted Water

(LPW) 4.38

7.5-8.5 (vacuum

system), 0.5

(abatement

device)

1.1% (vacuum

system), 5%

(abatement

device)

0.1-0.6%

(vacuum

system), 3%

(abatement

device)

Rainwater

Laboratory residual

stream

By-product stream (high

salt) 0.225

Potassium

content >14%

Polyol content

9

Table 4.1 Summary of wastewater characteristic from POSM, Polyether Polyol, and polymer polyol unit (contd.)

(Source: OSBL Basis Design Data for Repsol, 2014)

Unit Type Flowrate (m

3/h)

Temperature (oC)

Contaminants (mg/l) Note

Normal Max pH COD BOD SS Oil TDS

Polyether

Polyol

(RIGID &

CASE)


(LPW) 0.078 12-14 46% 21%

Low Polluted Water

(LPW) 6

7.5-8.5 (vacuum

system), 0.5

(abatement

device)

1.1% (vacuum

system), 5%

(abatement

device)

0.1-0.6%

(vacuum

system), 3%

(abatement

device)

Rainwater

Laboratory residual

stream 0.15

By-product stream (high

salt)

Potassium

content >14%

Polyol content

10

According to wastewater compositions and characteristics in Table 4.1, it is shown that

contaminants in the wastewater are mostly organic compounds, which is represented by

chemical oxygen demand (COD) level. The range of COD level in the wastewater streams

varies greatly, from 3,000 ppm to 180,000 ppm. Some of the streams also have very low

ratio of BOD/COD (< 0.1) which indicates that those streams are hard to be degraded

biologically. In addition, by-product streams from polyether polyol plant consist of polyol,

a chemical compound which is recalcitrant to biological treatment.

Although some streams are seem to be hardly biodegradable, some of the remaining

streams are likely possible to be sent to biological treatment due to its low level of COD.

Those streams are the LPW of polyether polyol (flexible) unit which has BOD/COD level

of 0.47, LPW from PO/SM plant, and also LPW from polyether polyol plant.Beside

organic contaminants, some streams in the wastewater also have nitrogen, salt

components, and even a small amount of oil.

4.1.3 Wastewater classification

The variety of contaminants in the wastewater makes the streams should be classified

based on the type and level of contaminants. This is done because some types of

contaminants may inhibit treatment process to remove the other contaminants type. For

example, the presence of salt in the wastewater may inhibit chemical process to remove

organic contaminants. Thus, salt and organic-containing wastewater should be separated

and treated by different method.

Based on the types and contaminants level, the wastewater is separated into three main

streams. The first and the second streams are streams without salt content while the third

streams are streams that contain salt, namely salt stream. The major contaminants in the

first and second streams are organics and nitrogen. The first streams are those that contain

high COD level (>10,000 ppm) as well as low BOD/COD ratio (

11

Table 4.2 Wastewater classification (contd.)

Classification Streams Final characteristics

Salt stream By-product from polyether polyol

(rigid & CASE) unit

Flow rate: 0.5 m3/h

Potassium content: 100,382

ppm

Polyol content: 35,581 ppm

BOD: 62,160 ppm

COD: 136,160 ppm

By-product from polyether polyol

(flexible) unit

HPW from polyether polyol

(rigid & CASE) unit

HPW from polyether polyol

(flexible) unit

All of the streams will be discharged to Hemmaraj Industrial Wastewater Treatment. The

required wastewater specification to be discarged to Hemmaraj is shown in Table 4.3.

Table 4.3 Required wastewater specification to discharge to Hemmaraj

(Source: Hemmarajs wastewater discharge specification, 2014)

Contaminant Maximum level

BOD < 500 mg/l

COD 750 mg/l

Suspended solid 200 mg/l

TDS 3000 mg/l

TKN 100 mg/l

pH 5.5 9.0

Temperature 45oC

Oil and fat 10 g/l

4.2 Available Technology for Wastewater Treatment

As we separate the wastewater into three main streams, the treatment method for each

stream should be different. Available technologies that may be possible to treat the

wastewater streams are described below.

4.2.1 Technology for high polluted and low polluted stream

4.2.1.1 Single method

In order to reduce the contaminant as well as to meet the wastewater discharge

requirement to Hemmaraj, the wastewater needs to be treated by several means of

technology. The technology could be chemical, biological, or even combination of

chemical and biological treatment. If the contaminant in the wastewater is not too high, the

wastewater can be treated by only one technology to meet the Hemmarajs discharge

specification. The technology is referred as a single method. The following explanation

12

will describe available single methods that could be applied to reduce the wastewater

contaminant. All of the following single methods have been applied commercially, either

as industrial or municipal wastewater treatment method.

1. Wet Air Oxidation (WAO)

The wet air oxidation process is a type of chemical treatment. It is an oxidation reaction

that occurs in the liquid phase. The chemistry of wet oxidation is such large molecules

which are difficult to treat biologically are oxidized by dissolved oxygen at an elevated

pressure and temperature. The elevated pressure in wet air oxidation process is required to

maintain the water in the liquid phase.

Wet oxidation reaction kinetics has been the subject of numerous studies. It is then

indicated that the oxidation proceeds by a free-radical reaction mechanism. In the absence

of initiators, free radicals are formed by reaction of oxygen with the weakest C-H bond of

the oxidized organic compound. The free radicals which has large electron affinity then

oxidizes organics and other compounds, such as sulfur, halides, nitrogen, and phosphor.

The formation of free radicals is shown in reaction (1) (4), while oxidation of wastewater

contaminants is shown in reaction (5) (10).

RH + O2 Ro + HO2

0 (1)

RH + HO2o Ro + H2O2 (2)

H2O2 + M 2OHo (3)

H2O2 H2O + O2 (4)

Organics + O2 CO2 + H2O + RCOOH*

(5)

Sulfur species + O2 SO42-

/other inorganic sulfates (6)

Halides species + O2 inorganic halides (7)

Organic Cl + O2 Cl- + CO2 + RCOOH

* (8)

Organic N + O2 NH3/NO3/elemental nitrogen + CO2 + RCOOH (9)

Phosphorus + O2 PO43-

(10) * Major fraction of residual organic compound

Since the liquid phase in wet air oxidation is not vaporized, this process requires less

energy for auto thermal operation rather than incineration. The nitrogen and sulfur

compound that may present in the waste water stream are not released as gaseous NOx and

SOx, but remain in the solution as acceptable nitrate and sulfate, meanwhile the

hydrocarbon compounds are converted to CO2 and water. The complete oxidation is rarely

happens, so a portion of organic COD will remain and ready to be treated biologically. The

wet oxidized effluent usually exhibits BOD: COD ratio of 0.6-0.7

The oxidation reaction is usually carried out at temperatures of 150oC to 320

oC and

pressure from 150 to 3200 psig. Oxygen as the oxidizing agent can be introduced from

compressed air or even pure compressed oxygen. However, the use of air as oxygen source

could lead to larger compressor cost, higher pressure rated equipment, and heat loss to

13

nitrogen component in the air. Therefore, the use of pure oxygen as the oxidizing agent is

such an attractive option.

During the operation, the feed of wet air oxidation system is pumped through heat

exchangers by a high pressure pump combined with a small amount of compressed air.

Introducing the feed stream along with small amount of compressed air is carried out in

order to prevent fouling in the heat exchangers, which are used to heat the cold feed. For

starting up, an external source of heat is needed to heat the cold feed. Heating the cold feed

for starting up can be carried out in trim heater using steam or hot oil as the external

sources of heat. The hot feed is then introduced from the bottom of the WAO reactor and

the oxygen is introduced from another bottom part of the reactor.

The outlet stream leaving the WAO reactor contains of two phase; hot gas and hot liquid.

The outlet stream is then sent through heat exchanger to be cooled forthwith heating the

incoming feed. The stream then goes through process cooler to be cooled by cooling water

prior to pressure let-down across the pressure control valve. The cooled two-phase stream

is sent to pressure control valve to be flashed before entering the separator. The separator

receives the flashed two-phase stream, resulting separation of liquid effluent and non-

condensable gas. The off-gas exits at the top of the separator and sent to the final treatment

unit or being used for other process heating, such as in PO/SM boilers

An application of wet air oxidation as wastewater treatment method can be seen at POSM

plant of Repsol YPF in Tarragona, Spain. In its wastewater treatment plant, the oxidation

of waste water occurs in bubble reactor at 295oC at 95 bar and 1.5 hour of reaction time

using pure compressed oxygen as the oxidant.. The nominal COD reduction of waste water

being treated by wet air oxidation is approximately 61%, resulting liquid effluent with

COD range of 20,000-30,000 mg/L which is further treated by PACT. The scheme of wet

oxidation process in POSM Plant of Repsol Tarragona is shown in Figure 3.

Figure 4.1 Wet air oxidation process

(Source: The Use of WAO and PACT for the Treatment of PO/SM Industrial Wastewater, 2002)

14

2. Ozone Oxidation

Ozone (O3) is one of the strongest commercially available oxidizing agents. This molecule

consists of three oxygen atoms which is unstable and very reactive under normal near-

earth condition. When decomposes in water, ozone creates hydroxyl radicals which react

quickly with a number of organic and inorganic compounds containing accessible amino

groups, double bonds, or aromatic systems. A complex chain of reaction that occurs and

results formation of OH* and superoxide

* radicals is shown by reaction (1) (4) (Karat,

2013).

O3 + OH- O2

*- + HO2

* (1)

O3 + O2*-

O3*-

+ O2 (2)

O3*-

HO3*-

(3)

HO3*-

OH* + O2 (4)

Ozone reaction with inorganic or inorganic compounds is shown by reaction (5) and (6).

CN- + O3 CNO

- + O2 (5)

RCH2OH + 2O3 RCOOH + 2O2 + H2O (6)

Oxidation by ozone can be performed in ozonation reactor at a large range of pH. The OH*

radical formation is dominant at high pH (>10), while the oxidative reaction with O3 is

more selective at low pH (

15

3. Powdered Activated Carbon (PACT)

PACT unit combines activated carbon adsorption and biological degradation to remove

organic components in the wastewater. The biological activity is combined with carbon

adsorption due to the wastewater components characteristic, which mostly contains

aromatic and polyol compound that are hard to be degraded by microorganisms. The

addition of activated carbon helps to adsorb organic components that can hardly be

degraded by microorganisms, so they could cling to their food source more efficiently.

An ordinary PACT unit consists of an aeration basin followed by a clarifier. The aeration

basin is used for treating the wastewater by activated carbon absorption forthwith

biological treatment. The effluent stream exiting the PACT unit is then sent to the clarifier

to separate the liquid effluent and the sludge that contains microorganisms as well as

activated carbon. Due to the presence of both biological growth and adsorption of organic

components occurring in the PACT system, wasting of spent carbon is required. This

wasted carbon is regenerated and returned to the PACT system.

In order to optimize the removal of organic compound, PACT system is usually combined

in series. Such system is applied in the waste water treatment of Repsol YPFs POSM

plant. The PACT unit consists of two aeration basins, each followed by a clarifier. The

first and the second set of PACT unit are called PACT-1 and PACT-2. The PACT-1

consists of 65 m diameter concrete aeration basin and a 17 m diameter clarifier while

PACT-2 consists of 30 m diameter aeration basin and a 17 m diameter clarifier. The flow

rate of wastewater that enters this system is 90 m3/h and average COD level of 26,000

ppm. The total COD reduction of both PACT tank is 97.6%. The scheme of the PACT unit

is shown in Figure 4.3.

Figure 4.3 Repsol PACT system unit

(Source: The Use of WAO and PACT for the Treatment of PO/SM Industrial Wastewater, 2002)

16

In some plants, the presence of PACT system is followed by wet air regeneration (WAR).

This system is used to recover the spent carbon from the PACT system. The recovered

activated carbon is then sent back to PACT unit to adsorb organic contaminant in the

wastewater.

The process for wet air generation is actually similar to the wet air oxidation process but

compressed air is used instead of oxygen. Before entering the wet air regeneration process,

the PACT sludge is thickened to ~5% solids content to obtain sufficient COD content for

auto thermal operation. The sludge is then pumped using hydraulic exchange pump and

compressed air is added to the sludge before passing the heat exchanger to be heated to

210oC. The hot stream sludge is then injected to the bottom of stainless steel bubble

reactor which operates at 243oC and 63 bar. The effluent leaving the reactor passes through

heat exchanger and cooled, resulting cooled fluid which sent to two phase separator. The

two phase separator successfully results two separated phases: gas and slurry. The gas

phase is sent to POSM plant boilers and the regenerated activated carbon slurry returns to

PACT aeration tank. The inert ash from in the bottom of the reactor is collected and

purged periodically to the storage drum, from where it is sent to filter press to be

dewatered before disposal.

4. Fenton Oxidation

Fenton oxidation is a process of oxidizing contaminants in the wastewater by using a

mixture of hydrogen peroxide (H2O2) and ferrous ion (Fe2+

). The process is based on

formation of reactive oxidizing species by two reaction pathways: a radical pathway,

which considers an OH radical formation (reaction 1) and a non-radical pathway

considering ferryl ion production (reaction 2). Each reaction is shown as the following:

Fe2+

+ H2O2 Fe3+

+ OH- + OH

* (1)

Fe2+

+ H2O2 FeO2+

+ H2O (2)

The Fenton reagent destroys a wide variety of organic compounds without formation of

toxic by-products (Barbusinski, 2009). Fenton oxidation process is characterized by its

cost effectiveness, simplicity, and suitability to treat aqueous wastes with variable

compositions. Comprehensive investigations show that Fenton oxidation is effective in

treating various industrial wastewater contaminants including aromatics, dyes, pesticides,

surfactans, explosives, and many other substances. Fenton reagent can also be effectively

used to for destruction of toxic waste and non-biodegradable compounds to render them

more suitable for a secondary biological treatment.

An application of Fenton oxidation in wastewater treatment plant was shown by its

effectiveness to treat a highly contaminated wastewater from a pharmaceutical plant. The

wastewater has COD level of 300,000 ppm, BOD level of 2900 ppm, and total suspended

solid (TSS) of 45,950 ppm. The Fenton oxidation process could reduce approximately

90% COD level in the wastewater.

17

5. Membrane Bioreactor (MBR)

The MBR process is a suspended growth activated sludge that utilizes microporous

membrane for solid-liquid separation. In this system, contaminants in the wastewater are

degraded by biological activity within the bioreactor. Treated wastewater and solids that

include biomass are then separated by ultrafiltration or nanofiltration membrane.

The typical arrangement of MBR system includes an aerated portion of the bioreactor,

anoxic zone, and the membrane filter. Based on the membrane location, there are two

configurations of MBR system: external and internal/submerged MBR sytem. Comparison

between the two MBR systems configurations is provided in Figure 4.4.

Figure 4.4 Comparison between external and internal membrane configuration

(Source: MBR for Municipal Wastewater Treatment)

18

Based on the fact that our wastewater has quite high flow rate, external membrane

configuration seems to be preferred due to its ability to handle higher flux. The external

MBR system has been widely applied either in industrial or municipal wastewater

treatment. One of the applied external MBR configuration is at municipal wastewater

treatment of Commune De Monteux, where its MBR can handle maximum flow rate of

400m3/h and has COD removal up to 96%. This MBR system is provided by Siemens

Water. The process scheme of external MBR system is shown in Figure 4.5.

Figure 4.5 Process scheme of external membrane system in Commune De Monteux WWT

(Source: Siemens Water Technology, 2010).

MBR system operates at ambient pressure and temperature and has transmembrane

pressure (TMP) up to 150 kPa. Standard flux rate for external MBR system ranges

between 50 to 200 L/m3/hr. Typical sludge retention time within the bioreactor is 5 30

days.

6. Thermophilic Membrane Bioreactor

The principle of thermophilic MBR is actually similar to MBR; a bioreactor equipped with

membrane filter which facilitates separation of solids and liquid effluent from the

bioreactor. A major different between them is that the bioreactor in thermophilic MBR

operates at temperature over 50oC, usually 75

oC. The elevated temperature can be

achieved by autoheating due to the heat produced by aerobic metabolism of the

microorganisms that consume abundant organic material present in the wastewater.

However, a minimal quantity of organic material is needed to sustain self-heating. Juteau

(2006) stated that a theoretical minimum of 24 g/l COD, oxygen consumption of 1.42

kg/kg organic matter oxidized, and BOD/COD ratio of 0.5 can produce heat of 20,000

kJ/kg volatile solid destroyed (assumed specific heat: 4.2 kJ/kgoC).

19

Thermophilic bioreactor performs well at higher organic loading rates and operates at

higher biodegradation rates compared to mesophilic (ambient temperature and pressure)

bioreactor. This is due to the enhancement of contaminants solubility, such as organics,

oil, and grease at higher temperatures. The effectiveness of thermophilic MBR in

degrading contaminants results a smaller size of bioreactor which also means smaller

footprint. On the contrary to these advantages, thermophilic conditions cause poor

settleability of sludge due to deterioration of sludge settling properties (Abeynayaka &

Visvanathan, 2010).

Another characteristic revealed in the investigation of aerobic thermophilic bioreactor is

the absence of nitrification (NH4+ NO3-) over 40oC. As a result, various hypothesis

arise, such as there is only ammonification occurs at thermophilic bioreactor, there is direct

aerobic deammonification, or there is actually nitrification of ammonia but quickly

denitrified. What is clear is the fact that an important part of the nitrogen is in the form of

ammonia. Due to the high temperature, ammonia can be completely volatilized and cause a

very bad smells (Abeynayaka & Visvanathan, 2010). This problem can be avoided by

recuperating ammonia vapors with scrubber or lower the ammonia volatilization by using

highly efficient aerator with oxygen transfer rate (OTE) of >90%.

The application of thermophilic MBR in wastewater treatment plant has recently been

spread widely. This technology has been applied in specialty chemical plant, food industry,

pharmaceuticals, and many others. An applied thermophilic MBR system in a specialty

chemical plant could handle wastewater with COD loading up to 180,000 ppm and has an

average COD removal of 90%.

7. Oxidation Ditch

Oxidation ditch is a modified activated sludge biological treatment that utilizes long solid

retention time to remove biodegradable organics. Typical oxidation ditch consists of a

single or multichannel configuration within ring, oval, or horseshoe-shaped basin. The

wastewater within the basin is circulated by the work of surface aerators. The circulating

wastewater helps to mix the oxygen with the wastewater which could foster microbial

growth and ensures contact of microorganisms with the incoming wastewater. A scheme of

oxidation ditch system is shown in Figure 4.6.

Oxidation ditch system operates at ambient temperature and pressure. The wastewater that

enters the ditch is aerated and circulated at about 0.25 0.35 m/s to maintain the solids in

suspension. The RAS recycle ratio is from 75 150% and the OTE ranges from 2.5 3.5

lb/Hp-hour. Required BOD loading that enters the system rates vary, from less than 160

ppm to more than 40,000 ppm (US Environmental Protection Agency, 2000).

20

Figure 4.6 Oxidation ditch system

(Source: US Environmental Protection Agency, 2000)

The main advantage of oxidation ditch is the ability to achieve removal performance with

low operational requirements as well as operating and maintenance costs. There is also

added measure of reliability and performance over other biological processes owing to a

constant water level and continuous discharge which lowers the overflow rate. Oxidation

ditch system also has long hydraulic retention time and complete mixing, which minimize

the impact of shock load or hydraulic surge. In addition, it produces less sludge than other

biological treatment processes due to the extended biological activity during the activated

sludge process. The last, the operation of oxidation ditch is more energy efficient and

result in reduced energy cost compared to other biological treatment processes.

Contrary to the advantages, oxidation ditch system has disadvantages such as is high

suspended solids concentration in the effluent and requirement of larger land area than

other biological treatment processes. This can prove costly, limiting the feasibility of

oxidation ditch in urban, suburban, or other areas where land acquisition costs are

relatively high.

In summary, information about commercially available single method is given in Table 4.4

Table 4.4 Summary of single wastewater treatment method

Method Organic loading Operating condition COD removal Scale

WAO Up to 150,000 ppm

COD

T: 150320oC P: 11 217 atm

55 75%

Industry

Ozone Oxidation >100,000 ppm COD T&P: ambient 60 92%

Fenton Oxidation Up to 300,000 ppm

COD

T: 20 80oC ; P: atm pH: 3.5

90%

PACT

BOD/COD: 0.4 0.6

T & P: ambient

98.5 99%

MBR 89 97%

Thermophilic MBR Up to 98.5%

Oxidation ditch T: 40 75oC Up to 97%

21

Reference plants of each method along with the vendors are listed in Table 4.5.

Table 4.5 Reference plants and vendors of single methods

Method Reference plants Vendors

WAO 1. Atofina Italias methyl methacrylate plant, Rhoo, Italy

2. BASF ethylene facility, Port Arthur, Texas 3. Tosco refinery 4. Municipal treatment plant of The Passaic

Valley, New Jersey

5. Ontario Hydros Bruce Spent Solvent

Siemens (1 4)

Kenox (5)

Ozone Oxidation 1. Wastewater treatment plant city of Kalundborg, Denmark (20% municipal and 80%

pharmaceuticalsinsulin production plant, 1200 m3/h) (ITT)

2. Municipal wastewater treatment plant in Regensdorf, Switzerland (900 m3/h) (Xylem)

3. Hospital Waldbrohi wastewater treatment, Germany (648 m3/h) (Xylem)

ITT (1)

Xylem (2 3)

Fenton Oxidation 1. Specialty chemical maufacturer, Louisiana (40 GPM wastewater with 400 - 600 mg/l phenol

compound and 4000 - 5000 mg/L COD)

2. Refinery Plant, Southeast US (15 GPM scrubber blowndown system containing COD,

phenols, and organic compounds)

3. Emergency treatment of phenol contaminated wastewater at chemical plant, Alabama

4. Aircraft Painting Stripping and Maintenace Facility, Midwest US (wastewater containing

toxic compounds e.g. methylene chloride,

pentachlorophenol, nitrophenols)

5. Wood treating facility (wastewater containing phenols, naphtols, and cresols)

US Peroxide

MBR 1. Syral, Groupe Tereos, Nestle, France (250 v/h) (Degremont Industry)

2. Groupe SCA, Laakirchen, Austria (2,500 m3/h) (Degremont Industry)

3. PetroChina Company Ltd. (1600 m3/h ) (Degremont Industry)

4. Gebt Lang Papier GmbH Ettringen paper mill (396 m3/h) (Xylem)

5. SCA Graphic Laakirchen AG, Austria paper mill (826.5 m3/h) (Xylem)

Degremont industry (1 3)

Xylem (4 5)

Thermophilic

MBR

1. Sartomer Specialty Chemicals 2. Alpharma Pharmaceuticals 3. Glaxo Pharmaceuticals 4. K&K Foods 5. Specialty Food Chemicals 6. Ferro Specialty Chemicals 7. Groundwater remediation 8. Sartomer Specialty Chemicals 9. Wolverhampton Chemicals

BioConversion

Solutions

22

Table 4.5 Reference plants and vendors of single methods (contd.)

Method Reference plants Vendors

PACT

Siemens

Oxidation ditch 1. Central water reclamation facility, Florida (capacity of 22.4 MGD)

2. Municipal wastewater treatment of Santa Rosa Country, Florida (capacity of 3 MGD)

Westech Engineering

Xylem

S & N Airoflo

4.2.1.2 Combined method

Although there are many commercial single wastewater treatment methods, it is known

that none of the said single methods is able to treat the wastewater to meet the discharge

requirement to Hemmaraj. All of the contaminants are still over the limit of Hemarajs

wastewater discharge requirement. Moreover, some of the streams are not feasible to be

combined and treated in a single method because contaminants in a certain stream can

inhibit the treatment. Therefore, a combination of single method is needed in order to meet

the discharge requirement.

The idea of single method combination is to combine the chemical and biological

treatment. The highly polluted water (HPW) will be treated by both methods: chemical

treatment first and followed by biological treatment. The chemical treatment is needed to

reduce BOD/COD ratio of HPW, so that the ratio meets the requirement to enter biological

treatment. The low polluted water (LPW) is directly sent to biological treatment due to its

BOD/COD ratio that has met the requirement of biological treatment. Below are detailed

23

descriptions of wastewater treatment method combination that could possibly treat the

HPW and LPW.

1. Wet Air Oxidation Powdered Activated Carbon Wet Air Regeneration

Combination of wet air oxidation, powdered activated carbon, and wet air regeneration is

called TAR. In this method, the wet air oxidation system acts as a chemical treatment

which treats the highly polluted water at the beginning. The effluent leaving the WAO

system is then enters the PACT to be treated by biological means and activated carbon

along with the LPW. The mixture of WAOs effluent and LPW that has been treated will

leave the PACT system and enter the sand filter for final treatment before being discharged

to Hemaraj.

In our case, the HPW wastewater with flow rate of 45.7m3/h will first enter the wet air

oxidation system. Here, the organic contaminant which is represented by COD will be

oxidized and converted into carbon dioxide, water, and organic acid. In the other hand, the

organic nitrogen contaminant will be converted into ammoniac, nitrate, or elemental

nitrogen, carbon dioxide, and organic acid.

If we consider a 65% removal of organic contaminant by the WAO, (similar to WAO

performance in POSM Plant of Repsol Tarragona, Spain) the HPWs COD concentration

will be reduced to 50,827 ppm. Along with the LPW, this WAO effluent is sent to the

PACT. However, due to the acidic pH of LPW, the LPW stream needs to be neutralized

first until reach a certain pH. The neutralized LPW which flow rate is 10.38m3/h and COD

concentration of 19,373 ppm is then combined with the WAOs effluent and routed to the

PACT system.

If we consider the PACTs maximum performance of COD and organic nitrogen

contaminant removal are 83%, the COD concentration in the PACT effluent will be 360

ppm and TKN concentration will be 36 ppm. This concentration has actually met the

discharge specification of Hemmaraj. However, to ensure that the amount of suspended

solid has already met the discharge requirement as well, this PACT effluent is routed to the

sand filter to reduce the remaining suspended solid. After being treated by the sand filter,

the wastewater is ready to discharge to Hemmaraj.

As the fresh activated carbon cost that is used in PACT system has a large contribution in

the overall cost of the method, this activated carbon needs to be regenerated. Regeneration

of activated carbon is done by the WAR. The sludge containing activated carbon and

biomass leaving the PACT system will be separated from the liquid effluent and enter the

WAR to be burnt by air. After being treated in the WAR, the regenerated activated carbon

will be sent back to the PACT system. It is also important to note that the amount of

activated carbon is usually lost approximately 10% of the initial mass in the WAR system.

Therefore, a 10% addition of fresh activated carbon is needed to the PACT system.

Summarized information about the TAR system is listed in Table 4.6.

24

Table 4.6 Summary of TAR system

Operating condition Pros & Cons Performance Estimated cost

WAO T/P: 150

oC 320oC/11

217 atm Retention time: 15 120 min

Flow rate: 1 50 m3/h

PACT T/P: ambient

Minimum dissolved

O2 : 2 ppm

Flow rate: 0.1 378.5 m

3/h

WAR T/P: up to 260

oC/up to

75 atm

Flow rate: > 0.5 m3/h

Sufficient energy due to the liquid

Oxidation

Autothermal operation

No oxides of nitrogen or sulfur in

the off-gases

High operating condition

Needs special material for the

WAO reactor

Needs VOCs treatment

Large footprint

COD removal:

WAO: 75 90% PACT: 83% TKN removal: up to

83%

Capital cost: $4,831,396/m

3/h

Operating cost: $ 2.6/m

3

2. Ozone Oxidation Membrane Bioreactor (MBR)

The combination of ozone oxidation and membrane bioreactor utilizes ozone oxidation as

the chemical treatment followed by membrane bioreactor as the biological treatment. As it

has been mentioned before, ozone is a strong oxidizing agent which can destroy a wide

range of contaminants. The treated wastewater from ozone oxidation is routed to the

membrane bioreactor to be treated by biological activity.

In the given case, if we consider the maximum performance of COD removal in ozone

oxidation system is 90% (Stacy, 2007), the treated effluent will have COD level of 1452.2

ppm. The treated effluent from ozone oxidation system will be combined with LPW which

has been neutralized to a certain level of pH. The combined stream is then routed to the

MBR system which consists of de-nitrification tank, nitrification tank, and ultrafiltration

membrane.

The combined effluent from ozone oxidation system and neutralized LPW will enter the

MBR system. If we take the maximum COD and TKN removal of MBR system is 97%

and 98% each (Stacy, 2007), the COD level in the treated effluent of MBR system will be

333.84 ppm and the TKN level will be 5.9 ppm. Such levels of COD and TKN have

already met the requirement discharge to Hemmaraj. Therefore, the treated effluent leaving

ozone oxidation-MBR system can be directly discharge to Hemmaraj. A simple flow

diagram of this system is shown in Figure 4.7. Summarized information about the

combination of ozone oxidation and MBR system is listed in Table 4.7.

25

Figure 4.7 Block diagram of TAR system

Fresh activated carbon 10%

HPW

45.7 m3

/h

COD: 145,219 ppm

N: 295 ppm

HPW

COD: 50,827 ppm

Dewatered ash to

disposal

Ash

Regenerated act.

carbon

Sludge

Wet Air Oxidation (WAO) Powdered Activated Carbon

(PACT) Sand filter

Wet Air Regeneration

(WAR)

Filter press

Neutralization

HPW + LPW

LPW

10.38 m3

/h

COD: 19,373 ppm

pH < 1

LPW

pH: 6 - 9

Discharge to Hemmaraj

56 m3

/h

COD: 360 ppm

TKN: 36 ppm

Org. + O2 CO

2 + H

2O + RCOOH

*

Org. N + O2 NH

3/NO

3/elemental N + CO

2 + RCOOH

Air

O2

26

Table 4.7 Summary of ozone oxidation MBR system


Ozone oxidation T/P: ambient

Flow rate: 1 10,000 m

3/hr

O3 dosage: 0.7 1.1 g / g COD eliminated

T in Catalytic Ozone

destructor : 30 70oC Catalyst in catalytic

destructor: palladium,

manganese, nickel

oxides)

MBR T/P: ambient

TMP: up to 150 kPa

Standard flux rate: 50

200 L/m2.hr SRT: 5 30 days

Very powerful oxidizing agent

Remove wide range of pollutant

Environmentally friendly

Ozone minimizes sludge production

Small footprint (10 40 % to conventional)

High operating cost Low energy

efficiency

Requires corrosion-resistant material

due to ozones corrosivity

COD removal:

Ozone oxidation: 60 99%

MBR: 89 - 97% TKN removal: up to

96 - 98%

Capital cost: $136,017.6/m

3/h


3

3. Thermophilic Membrane Bioreactor Chemical Treatment

The combination of thermophilic MBR and chemical treatment has been recently used in

industrial waste water treatment. The utilization of thermophilic MBR may be relatively

new and is believed to have better performance than the existing biological treatment. One

of hundreds vendor that has been widely trusted to provide this combination of technology

is BioConversion solution, which gives a commercial name of this wastewater treatment

combination as Advanced Fluidized Composting.

Chemical treatment that used in this method is usually utilization of oxidizing agent such

as hydrogen peroxide (H2O2). The oxidizing agent will oxidize and destroy contaminant in

the wastewater. The amount of oxidizing agent used depends on the amount of

contaminant in the wastewater itself.

Contrary to the previous methods, the applied combination of thermophilic MBR-chemical

treatment has reversed order between the chemical and biological treatment. The

wastewater will be routed to the MBR first (biological treatment) and then to the chemical

treatment. The vendor claimed that this treatment order can be used in almost all kinds of

wastewater stream, even in wastewater with high COD content. They also claimed that this

treatment order is done to reduce the operating cost, because routing the HPW alone

directly to the chemical treatment will consume high amount of chemical.

If we follow the applied order of thermophilic MBR-chemical treatment, we need to

combine the HPW and LPW together in the beginning and send them to the thermophilic

bioreactor system. The combination of HPW and LPW will result wastewater flow rate of

56 m3/h, COD content of 121,926 ppm, and TKN content of 240 ppm. The treated effluent

leaving the thermophilic bioreactor is sent to the ultrafiltration membrane to separate

27

liquid effluent and sludge containing biomass and hardly biodegradable compounds. The

sludge is routed to the chemical treatment tank. Here, the oxidizing agent (usually H2O2)

will oxidize the remaining contaminants in the wastewater which are hard to degrade

biologically. The treated effluent from chemical treatment tank will be routed back to the

MBR system to reduce more levels of contaminant. Take the maximum performance of

COD and TKN removals are 99.8% and 75% (similar to the commercial scale of this

technology that treats pharmaceuticals wastewater with COD level of 200,000 ppm). The

wastewater effluent leaving this method will have COD level of 244 ppm and TKN level

of 60 ppm and is ready to discharge to Hemmaraj. A simple block diagram of this method

is shown in Figure 4.6.

Due to the very high amount of COD level and low ratio of BOD/COD in our HPW, a

pilot test should be done before deciding whether the treatment order is reversed

(biological first followed by chemical treatment) or not. If the pilot scale tests result

shows that routing the wastewater directly to MBR system is inefficient (take a long time

to reach the mentioned percentage of performance), then separating entrance for HPW and

LPW is needed. The HPW is firstly sent to the chemical treatment to lower its COD level

as well as increasing the BOD/COD ratio. The effluent of chemical treatment is then

combined with the neutralized LPW and treated in the MBR system. The effluents

contaminant will have accepted levels to be discharged to Hemmaraj.

Summarized information about the combination of thermophilic MBR and chemical

treatment system is listed in Table 4.8.

Table 4.8 Summary of ozone oxidation MBR system


Thermophilic bioreactor

T: 45oC 75oC

Retention time: 20 30 min for readily

biodegradable

compounds

Flow rate: up to 158

m3/h

Minimum OTE: 10 15%

Minimum dissolved

O2 : 1 ppm

Ultrafiltration membrane

T/P: ambient

Flux range: 40 135 l/m

2 . h

TMP: up to 210 kPa

Chemical treatment tank

T/P: ambient

Lower even zero waste sludge

production

High loading rate capability

Smaller footprint (10 - 40% smaller

than conventional

technology)


Achieve equivalent result to WAO

for most waste

stream with less cost

Require operation and maintenance

which is more

complicated than

disposal

COD removal: Up t0

99.8%

TKN removal: up to

75%

Capital cost: $56,574/m

3/h


3

28

4. Fenton Oxidation Oxidation Ditch

Fenton oxidation has been widely used in wastewater treatment plant due to its powerful

and selective activity in reducing contaminants in the wastewater. Such high performance

of Fenton oxidation makes the requirement of biological treatment that follows the Fenton

oxidation is not too high. A simple yet effective biological treatment is enough to be

placed after Fenton oxidation system. The choice of biological treatment then falls on

oxidation ditch which is more energy intensive, produces less sludge, and many other

excellences than other biological treatments.

In the combination of Fenton oxidation and oxidation ditch, the HPW is first routed to the

chemical treatment tank where oxidation reaction of contaminant by Fenton regent occurs.

If we take the maximum COD removal in Fenton oxidation system is 90% (similar to the

applied Fenton oxidation system in paper mill wastewater with COD level of 300,000

ppm), the effluent leaving chemical treatment tank will have COD level of 14,522 ppm. It

is important to note that oxidation reaction by Fentons reagent is only effective at acidic

pH (approximately at pH 3.5). Therefore, an acidification of HPW stream is needed before

this stream is treated in the chemical treatment tank.

The chemical-treated effluent is then routed to the oxidation ditch to be treated by

biological treatment. Before entering the oxidation ditch system, this stream is combined

with the neutralized LPW which pH is around 6 9. The effluent leaving oxidation ditch

will pass through the clarifier to separate the sludge and the liquid effluent. The sludge

which contains biomass will be routed back to the oxidation ditch while the liquid effluent

will be sent to the disinfection system to remove the remaining biomass. The disinfection

system usually uses chlorine to kill the remaining microbes in the wastewater before being

discharge to environment. If we take the maximum COD and TKN removal in oxidation

ditch each is 98.5% and 94%, the final COD and TKN level in the effluent will be 501 and

17.7 ppm. This level of contaminant in the wastewater is accepted to be discharged at

Hemmaraj.

A simple block diagram of Fenton oxidation-oxidation ditch is shown in Figure 4.7.

Summarized information about the combination of Fenton oxidation and oxidation ditch

system is listed in Table 4.9.

29

Table 4.9 Summary of Fenton oxidation oxidation ditch system


Fenton oxidation (H2O2/Fe

2+)

T/P: 20oC 80oC /

atmosphere

pH around 3.5

Retention time: 5 10 min

Flow rate: 15.75 1800 m

3/h

Amount of H2O2: 35 50% (w/w)

Catalyst: Fe salt:

Fe(NO3)3,

FeSO4.7H2O,

FeCl2.4H2O

H2O2 : Fe = 10 : 1

Oxidation ditch T/P: ambient

pH: 6 9 Minimum dissolved

O2 : 2 4 ppm Circulated wastewater

velocity: 0.25 0.35 m/s

HRT: 6 30 hours SRT: 15 30 days

Very selective oxidizing agent

Does not require special material

for the reactor


Can save energy saving up to 40%

compared to

conventional

biological treatment

Requires high concentration of

H2O2 which cost is

higher than air

Requires larger land area than

conventional

biological treatment

TSS in effluent is relatively higher

than other biological

treatment process

COD removal:

Fenton: 90% Oxidation ditch: 95

98.5% TKN removal: up to

90 94%

Capital cost: $55,713.4/m

3/h


3

4.2.2 Technology for salt stream

As the salt content in the salt stream may disturb the chemical and biological treatment, the

salt stream needs to be treated by special treatment. Technologies that have been

commercially used to treat salt-contained wastewater and become consideration in our

method selection are described as the following.

1. Thermal Oxidizer

Thermal oxidizer is a unit where combustion of contaminants, especially organic content

in the waste occurs. The combusted organic content will be converted to carbon dioxide,

water, and ash. The phase of waste that can be combusted in thermal oxidizer could be

either liquid or solid. Thermal oxidizer has been widely used in industrial waste treatment

especially to treat high solid-content and highly contaminated waste. By thermal oxidizer,

almost all contaminants in the waste will be burnt and converted to ash and gases.

There are two types of thermal oxidizer that have been commercially available. The first

one is the fluidized bed technology which consists of windbox section where combustion

30

air is introduced, a bed section where the waste is fluidized along the sand, and a freeboard

section where combustion is completed. In fluidized bed, waste and auxiliary fuel are

injected co-currently to the unit. The exhaust gases and ash that are produced from the

combustion will pass through energy recovery facilities before it is treated in air pollution

control system. The ash is usually removed in a slurry form by wet scrubbing system and

some of thermal oxidizer units have a dry ash removal system upstream of the scrubbers.

The residence time in fluidized bed thermal oxidizer is 5 60 seconds.

The second type of thermal oxidizer is multiple hearth technology. It is a vertical

refractory-lined cylinder with a series of horizontal refractory brick hearths and rotating

center shaft. The multiple hearth is separated into three zones; the top hearth or drying

zone where water is evaporated, the middle hearth or the combustion zone where volatile

contaminants are oxidized, and the cooling zone where the ash is cooled by incoming

combustion air. In multiple hearth, the waste and auxiliary fuel are injected counter

currently to the system. The residence time in multiple hearth system is 40 60 minutes.

Schematic figures of fluidized bed and multiple hearth thermal oxidizers are shown in

Figure 4.8.

Figure 4.8 Schematic figures of multiple hearth (left) and fluidized bed (right)

Source:

The operation of thermal oxidizers can be run autothermally. In general, about 70% of heat

required by waste incineration come from the waste itself (Dangtran, dkk,200x). The

remaining 30% of the heat are obtained from auxiliary fuel and/or from the combustion air.

31

The supplementary heat can also be recuperated from the flue gas to preheat the

combustion air up to 1250oF to achieve autogenous combustion.

Although fluidized bed and multiple hearth function are similar, the different in their basic

design leads to some advantages for the fluidized bed system. Some plants even replaced

multiple hearth with fluidized bed Manchester Water Pollution Control Facility,

Manchester, NH, Wyoming Valley in Wilkes Barre, PA, and T.Z. Osborne in Greensboro,

NC and claimed that the replacement results a better performance. Some of the

excellences of fluidized bed compared to multiple hearth are lower NOx formation, lower

CO formation, lower THC formation, easier for control and automation, wider rang in feed

variability, lower fuel usage, lower maintenance cost, lower power requirement, etc.

Summarized comparison between fluidized bed and multiple hearth is shown in Table 4.10

32

Figure 4.6 Block diagram of Ozone oxidation-MBR system

Concentrate containing biomass & untreated compounds

LPW

pH: 6 - 9

HPW

45.7 m3

/h

COD: 145,219 ppm

N: 295 ppm

HPW

COD: 1452,2 ppm

N: 260 ppm

Ozone oxidation De-nitrification tank Nitrification tank Ultrafiltration

membrane O

3

Neutralization

LPW

10.38 m3

/h

COD: 19,373 ppm

pH < 1

Organic N NH4

+

NO2

-

+ NO3

-

Discharged to

Hemmaraj

56 m3

/h

COD: 333.84 ppm

N: 5.9 ppm

NO3

-

NO2

-

NO N2O

N

2

O3

destructor

Unreacted O3

O2

Sludge

Acidification

HPW

45.7 m3/h

COD: 145,219 ppm

N: 295 ppm

HPW

COD: 14,522 ppm

Neutralization

Clarifier Disinfection

LPW

10.38 m3/h

COD: 19,373 ppm

pH < 1

Fenton Oxidation ditch

LPW

pH: 6 - 9

Discharge

56 m3/h

COD: 501 ppm

TKN: 17.7 ppm

H2O

2/Fe

2+

Figure 4.7 Block diagram of Fenton oxidation-oxidation ditch

33

Table 4.10. Comparison between fluidized bed and multiple hearth

Parameters Multiple hearth Fluidized bed

Flow Counter current Intense back mixing

Heat transfer Poor High

Waste detention time - 3 hours 1 5 minutes

Gas detention time at high

temperature 1 - 2 seconds 6 8 seconds

Combustion temperature 1500 1800 oF 1400 1500 oF

Gas exit temperature 800 1000 oF 1500 1600 oF

Excess air 75 100% 40%

Thermal oxidation system can handle a large range of feed flowrate and contaminants as

well as remove nearly all contaminants in the wastewater. Even so, the application of

thermal oxidizer also raises cons. This is due to the pollutant gas released which make this

process is considered as not green process. A summary of strengths and weaknesses of

thermal oxidation system is shown in Table 4.11.

Table 4.11 Strengths and weaknesses of thermal oxidation system

Strength Weakness

Complete stabilization process destroying all volatile solids and pathogens

Large volume and mass reduction lowers truck traffic as compared with other biosolids handling alternatives

Low life cycle cost for medium and large facilities Low potential for onsite or offsite odors Requires small land area and can operate continuously in all

weather conditions

Lower auxiliary fuel requirements than other biosolids handling alternatives

Strictest monitoring and reporting requirement ensure public of proper operation

Produces recoverable energy that can be used to produce heated air, gas, water, and oil that can be used for heating and

electricity

Pre-stabilization process not required

High initial capital cost Poor public image and acceptance due to

misinformation and perceptions

May not be appropriate for non-continuous operation

Permitting is more complex than for other biosolids alternatives

Not perceived as green process Ash reuse programs have not been well

developed

Emits pollutant gases such as CO, NOx, SOx, and THC (total hydrocarbon, usually exhibits as CH4)

In the end, technical and economic information of thermal oxidizer system is provided in

Table 4.12.

34

Table 4.12 Summary of technical and economic information about thermal oxidation system

Allowable inlet flow rate

Main equipment

Fluidized bed:

Windbox section where combustion air is introduced Refractory arch where hot air distributed homogenously through the bed Combustion zone where biosolids and fuel is introduced Freeboard which acts a s afterburner to complete combustion of volatile

hydrocarbon

Multiple hearth:

Upper hearth where biosolids water and organic compounds evaporated Middle hearth/combustion zone Lower hearth/cooling zone

Operating condition

Fluidized bed:

Bed area/combustion zone: 1350 1500oF Freeboard: 50 1000F higher than combustion zone Biosolids detention time: - 3 hours Multiple hearth:

Upper hearth: 800 1000oF Middle hearth: 1500 1700oF Lower hearth: 350 400oF Biosolids detention time: 1 5 min

Additional equipment

Heat exchangers Air pollution control system which includes venturi/nozzle scrubber, cooling

tray, and electrostatic precipitator

Operating mode Continuous (24 hours, 4 5 days per week)

Operation & Maintenance

70% of the heat required by biosolids come from the biosolids: 25% of the flue gas can preheat the combustion ait up to 1250

oF to achieve autogenous

combustion

The remaining 30% of the heat are from auxiliary fuel Autogenous combustion condition: combustion air temperature: 1200oF and

solid content 25 28%

Cost

Capital cost $175,000 - $250,000

Operating

cost (per dry

ton organics)

$155 - $260 (fluidized bed) $172 - $313 (multiple hearth)

Applied scale Industry

Available vendors

Degremont Technology Hitachi Zosen Industrial Furnace Company Cockerill Maintenance & Ingenierie

Reference Plants

Municipal wastewater treatment of Waldwick, New Jersey Pharmaceutical waste Chemical and paper mill waste Petrochemical waste

35

2. Electrodialysis Reversal

Electrodialysis is a membrane process for recycling water from electrolyte, including salt

solution. The electrodialysis system consists of cation and anion exchange membrane,

dilution and concentration chamber, and also cathode and anode.

The principle of electrodialysis system is that the dissolved salts which have positive and

negative charge will migrate through ion-selective semipermeable membranes. This

phenomenon happens as a result of their attraction to two electrically charged electrodes.

The anions will pass through the anion-selective membrane but are not able to pass by the

cation selective membrane, which blocks the anion in the brine stream. Similarly, cations

move in the opposite direction through cation selective membrane under the negative

charge and are trapped by anion-selective membrane.

EDR system is a variation of ED process. EDR uses electrode polarity reversal to

automatically clean the membrane surface. EDR works the same way as ED, except the

polarity of the power is reversed two to four times per hour. When the polarity is reversed,

the source water will dilute and concentrate compartments are also reversed and so are the

chemical reactions at the electrodes. This polarity reversal will prevent the formation of

scale on the membrane. A schematic diagram of EDR system and a summary of its

technical and economic information are shown in Figure 4.9 and Table 4.13.

Figure 4.9. Schematic diagram of electrodialysis reversal system

(Source: U.S. Department of the Interion Bureau Reclamation, 2010)

36

Table 4.13 Summary of technical and economic information of EDR system

Allowable inlet flow rate 10 25 gallons/day/ft2 membrane area

Main equipment

Cation-exchange membrane Anion-exchange membrane Dilution and concentration chamber Cathode and anode

Operating condition

pH: 2 11 Pressure: atmosphere Ratio of permeate and feed water flow rate: 85 95%

Additional equipment

Raw water pumps Debris screen Slow mix flocculator Clarifier Gravity filters Chlorine disinfection Clearwell storage

Operating mode Continuous

Operation & Maintenance

Reversal frequency: 15 30 minutes Cleaning using 5% hydrochloric acid solution Average membrane life: 12 15 years

Energy consumption 2.4 kWh/m3 with elect

Documents

Feasibility study of wastewater treatment in specialty chemical plants