Electro fenton treatment of poultry wastewater
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CHAPTER 1
INTRODUCTION
Food and beverage industry is one of the largest industry sectors and is
essential to all economies. It has its dominating role in satisfying basic needs and
requirements of every person. The last 5 decades has seen a dramatic increase in
the demand for food due to the rapid growth in world population. Annual dairy
production accounts for 514 million tonnes; cereal production (including rice, wheat
and coarse grains) is approximately 2 billion tonnes where as meat production is in
the order of 200 million tonnes.
With the development in the industrial sector consequently there is
increase in raw material usage. Water is an inevitable raw material for food
industries. The main sources for the industrial sector are groundwater and surface
water. Ground water has emerged as an important source to meet the water
requirements of the industries in recent years. According to World Development
Report (WDR) of 2003, in developing countries, 70 percent of the industrial waste
water are dumped without proper treatment, thereby polluting the usable water
supply. According to Centre for Science and Environment (CSE) report in 2004 on
an average each litre of wastewater discharged further pollutes 5-8 litres of fresh
water.
Meat industry is one of the highly polluting industries which require great
concern with the environmental aspect. The primary steps in poultry processing
includes bleeding, scalding or skin removal, evisceration, washing, chilling, cooling,
packaging and cleaning. In all these processes water plays a key role. Poultry
processing expels a more difficult waste stream to treat. The killing and rendering
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processes creates blood by-products and waste streams, which are very high in
BOD (1200-3800 mg/L) and COD (2650-6720 mg/L) values.
Waste streams from poultry processing can be generalised in to
carcasses, skeleton waste, rejected or unsatisfactory animals, fats, animal faeces,
eviscerated organs, blood and waste water. All the solid waste are subjects to
rendering and are converted to useful by-products. They are rich in protein, nitrogen
and minerals like phosphorus. They are used to produce animal feed, cosmetics,
fertilizers fish and pet feed.
In conventional system of poultry waste water system follows
coagulation, flocculation, aeration, flotation and biological treatment. Most of the
times it is treated waste water is discharged into nearby water bodies or open
lands. Sometimes it is used for irrigation of garden and lawns. Improper processing
and discharging of wastewater in water bodies is a severe thread to aquatic lives.
Whereas discharging it in open land leads to outspread of diseases. Drawbacks
associated with this conventional wastewater treatment system are high sludge
production which is difficult to process further. If resins or membranes are used for
wastewater treatment it has to be recharged or changed periodically. And also this
conventional system is less efficient remove some of the biological compounds and
colour to make it reuse into the production process.
The advent of various technical developments led to the discovery of
various treatment processes. One among them is Advance Oxidation Process. It
refers to chemical treatment a process which employs oxidation techniques to
degrade biologically toxic and non degradable chemicals. This treatment process is
based on the production on highly reactive hydroxyl radicals as the primary oxidant.
Advance oxidation process is broadly classified into Fenton process, Photo-Fenton
process, UV based process, photo catalytic redox process, sonolysis, Electro
Fenton process etc., The main function of this AOP is generation of highly reactive
free radicals primarily Hydroxy radicals which are effective in destroying number of
organic chemicals because they are reactive electrophiles that react rapidly and
non selectively.
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Fentons Reagent system of AOP is an attractive and effective
technology because it uses only Iron and Hydrogen peroxide. Iron is an abundant
material in nature and hydrogen peroxide is environmentally safe. Fentons method
is capable of degrading large number of hazardous organic pollutants and there are
no toxic reagents are involved in this process it also leaves no residues and the
technology of this process is so simple. But the ferrous ions consumed in this are
regenerated at a very slower rate. And it becomes a rate limiting step in this
process.
Electrochemical advanced oxidation processes (EAOP) based on
Fentons reaction chemistry are eco-friendly methods that have received much
attention for water treatment. The most popular EAOP is the electro Fenton
process. Electro fenton process has two different configurations. In the first one
Fenton reagents are added to the reactor from outside and inert electrodes with
high catalytic activity are used as anode material while in the second configuration,
only hydrogen peroxide is added from outside and Fe2+ is provided from sacrificial
cast iron anodes. Compared to conventional Fenton process, the electro Fenton
process has the advantage of allowing better control of the process.
In the presence of ferrous ions and in acidic aqueous medium the
oxidation power will be enhanced due to the production of very reactive one
electron oxidizing agent hydroxyl radical (OH) from the Fenton reaction. This
electro Fenton process can generate OH by the simultaneous electrochemical
reduction of O2 in the presence of catalytic amounts of ferrous ions. And this
method is found to be effective for the degradation of number of organic pollutants.
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CHAPTER 2
REVIEW OF LITERATURE
This chapter deals with review of literature for industrial water usage,
poultry wastewater, wastewater treatment, advance oxidation processes and
electro fenton process.
2.1 GLOBAL WATER AVAILABILITY
70% of the earth surface is covered with water, which amounts to 1400
million cubic kilometres (m km3). However, 97.5% of this water being sea water, it
is salty. Fresh water availability is only 35 m km3. Out of the total fresh water,
68.7% is frozen in ice caps, 30% is stored underground and only 0.3% water is
available on the surface of the earth. Out of the surface water, 87% is stored in
lakes, 11% in swamp and 2% in rivers. As all the sweet water is not extractable,
only 1% of the total water can be used by human beings. As water was available in
plenty, it was considered as a free resource since generations. However, with
growing demand for water and depletion of the available water, assured supply of
good quality water is becoming a growing concern. (Anon., 2006).
2.2 INDUSTRIAL WATER USAGE
The World Bank estimates that the current industrial water use in India is
about 13 percent of the total freshwater withdrawal in the country and the water
demand for industrial uses and energy production will grow at a rate of 4.2 per cent
per year, rising from 67 billion cubic metres in 1999 to 228 billion cubic metres by
2025. All these estimates reveal that the industrial water demand is not negligible in
India and that it is bound to grow in the coming years.
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Industries not only consume water but also pollute it. In developing
countries, 70 percent of industrial wastes are dumped without treatment, thereby
polluting the usable water supply. Note that industrial water demand is not the
demand for water as in other sectors, as a large part of the water withdrawn for
industrial use is discharged as polluted water by the industries. According to Centre
of Science and Education (CSE, 2004) report on an average, each litre of
wastewater discharged further pollutes about 58 litres of water which raises the
share of industrial water use to somewhere between 3550 percent of the total
water used in the country. (World Development Report, 2003)
2.3 POULTRY PROCESSING INDUSTRY AND WATER USAGE
Food processing industry can be divided into four major sectors
including fruit and vegetable processing, meat, poultry and sea food, beverage and
bottling and dairy operations. All of these sectors consume huge amount of water
for processing food. A considerable part of these waters are potential wastewaters
to be treated for safe disposal to the environment.
Poultry processing industries offer a more difficult waste stream to treat.
The killing and rendering processes create blood by-products and waste stream,
which are extremely high in BOD. The primary steps in processing chicken include
1. Rendering and bleeding
2. Scalding and skin removal
3. Internal organ evisceration
4. Washing, chilling and cooling
5. Cleaning
Solid wastes which include skin, fat, faeces, muscles etc, are subjected
to rendering process and converted to useful by-products. Wastewater is tedious to
treat and Discharge of this effluent without proper treatment in water bodies is a
severe threat to aquatic lives and affects the ground water.
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2.4 POULTRY AND WASTE WATER TREATMENT
Number of methods has been studied previously for the treatment of
meat industry wastewater. The maximum of 85% of COD removal is obtained in
Upward-flow anaerobic sludge blanket (UASB) reactor treatment for poultry
wastewater (Anna Kwarciak-Kozowska, et al., 2011). And a COD removal of 54-
67% is obtained in the treatment of meat industry waste water using dissolved air
flotation (Rennio F. De. Sena, et al., 2009)
2.5 ADVANCE OXIDATION PROCESSES (AOPS)
Advance Oxidation processes (AOPs) are an attractive for treatment of
contaminated grounds, surface and wastewaters containing heavy pollutants.
These technologies generate hydroxyl radical (OH) which is a highly reactive
oxidant (E = 2.8 V versus SHE) (Farre et al., 2006; Guinea et al., 2008; Pera-Titus
et al., 2004). These methods are attractive because of the possibility of the
mineralizing the target compounds (Zoh and Stenstrom, 2002). The main
interesting of OH radicals are also characterized by a non selectivity of attack
which is a useful attribute for an oxidant used in wastewater treatment and to solve
pollution problems. OH is the second strongest oxidant after fluorine.
Methods based on chemical and photolytic catalysis have been included
in a group of new technologies denominated. AOPs generated highly degrading
OH radicals. As OH radicals are so reactive and unstable, they must be produced
continuously. These radicals are produced by several methods such as hydrogen
peroxide/ultraviolet irradiation (H2O2/UV), hydrogen peroxide/ozone (H2O2/O3),
ozone/ultraviolet irradiation (O3/UV), TiO2-catalyzed UV oxidation, and also the
combination of H2O2 with ferrous ions (Fenton reagent).
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Oxidation Species Oxidation power (V)
Fluorine (F2) 3.03
Hydroxyl radical (OH) 2.80
Atomic Oxygen 2.42
Ozone (O3) 2.07
Hydrogen peroxide (H2O2) 1.77
Permanganate (KMnO4) 1.67
Chlorine (Cl2) 1.36
Table No.2.1 Oxidation power of selected oxidizing species (Beltran et al., 1998)
2.6 FENTON PROCESS
Fenton process is known to be very effective in the removal of many
hazardous organic pollutants from water based on an electron transfer between
H2O2 and iron. The reactivity of this process was first observed in 1894 by its
inventor H.J.H. Fenton, its utility was not recognized until the 1930s when a
mechanism based on hydroxyl radicals was proposed. The main advantage is the
complete destruction of contaminants to harmless compounds, e.g. CO2, water and
inorganic salts. The Fenton reaction causes the dissociation of the oxidant and the
formation of highly reactive OH that attack and destroy the organic pollutants. The
reaction mechanism can be described by means of the following reactions: the
generation of hydroxyl radicals (OH) between H2O2 and Fe2+ (Reaction 2.1), the
degradation of organic substance by the OH (Reaction 8). In the mean time, some
reversed reactions and side reactions (Reactions 2.2, 2.3, 2.5, and 2.6) also occur
(Kang et al., 2002; Kang and Hwang, 2000; Neyens and Baeyens, 2003; Oturan et
al., 2001).
Fe2+
+ H2O2 Fe3+ + OH + OH- (Reaction 2.1)
Fe2+
+ OH Fe3+ + OH- (Reaction 2.2)
Fe3+
+ H2O2 FeOOH2+ + HO2 + H+ (Reaction 2.3)
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OH + Organic Products (Reaction 2.4)
H2O2 + Organic Products (Reaction 2.5)
OH + H2O2 HO2 + H2O (Reaction 2.6)
OH + OH H2O2 (Reaction 2.7)
FeOOH2+
Fe2+ + HO2 (Reaction 2.8)
HO2 + Fe2+
HO2 - + Fe3+ (Reaction 2.9)
HO2 + Fe3+
O2 + Fe2+ + H+ (Reaction 2.10)
The reaction rate of reaction 2.3 is much slower than that of reaction 2.1
meaning that Fe2+ is consumed quickly, but reproduced slowly. Thereby, the
oxidation rate of organic compounds is fast when large amount of Fe2+ is present
because large amount of OH is produced (Behnajady et al., 2007). Numerous
competing reactions which involve Fe2+, Fe3+, H2O2, OH, hydroperoxyl radicals
(HO2) and radicals derived from the substrate, may also be involved. OH radicals
may be scavenged by reacting with Fe2+ or H2O2 as seen in reactions 2.2 and 2.6.
Fe3+ formed through reactions 2.1 and 2.2 can react with H2O2 following a radical
mechanism that involves OH and HO2 with regeneration of Fe2+ as shown in
reactions 2.3, 2.8, 2.9 and 2.10 (Lucas and Peres, 2006).
The Fenton reaction also has several important advantages such as
short reaction time among all advanced oxidation processes, iron and H2O2 are
cheap and non-toxic, and the process is easily to run and control (Argun et al.,
2008).
However, in Fenton process, a large amount of sludge will be produced
during the neutralization process, especially when the high strength wastewater is
treated (Oturan et al., 2001; Qiang et al., 2003; Zhang et al., 2007). To solve this
problem, the Fenton reaction efficiency can be enhanced in the presence of UV
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irradiation and electrochemical as commonly called photo-Fenton and electro-
Fenton process, respectively.
2.7 ELECTRO-FENTON PROCESS
The application of electrochemical method in Fenton process, named
electro-Fenton process, could be generally divided into four categories (Khataee et
al., 2009; Ting et al., 2009; Zhang et al., 2006). In the first one, H2O2 is externally
applied while a sacrificial iron anode is used as Fe2+ source. In the second
category, Fe2+ ion and H2O2 are electro-generated using a sacrificial anode and
cathode via the two electro reduction of sparged oxygen, respectively. In the third
category, Fe2+ ion is externally applied, and both of H2O2 and Fe2+ are concurrently
generated at cathode, but primarily focusing on H2O2 generation on mercury pool,
carbon felt, reticulated vitreous carbon, graphite, activated carbon fiber, stainless
steel plate or carbon-PTFE cathode. In the fourth category, Fentons reagent is
utilized to produce OH radicals in the electrolytic cell, and Fe2+ ion is regenerated
via the reduction of Fe3+ ion or ferric hydroxide sludge on the cathode.
Fenton reaction involves several sequential reactions as shown in
reaction 2.1-2.10. The well known Fentons reaction (reaction 2.1) constitutes a
source of OH radicals production by chemical means. The H2O2 and Fe2+ ions are
simultaneously generated on the working electrode, according to the following
electrochemical reactions.
On the cathode side
O2 + 2H+ +2e
- H2O2 (Reaction 2.14)
Fe3+ + e
- Fe2+ (Reaction 2.15)
H2O + e- H2 + OH- (Reaction 2.16)
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On the anode side
2H2O 4H+ + O2 + 4e- (Reaction 2.17)
Fe2+
Fe3+ + e- (Reaction 2.18)
Fentons reaction (reaction 2.1) takes place then in homogeneous
medium leading to the formation of OH radicals.
The anodic reaction is the oxidation of water to molecular oxygen
(reaction 2.17) which is used for optimal production of H2O2 (reaction 2.14)
necessary for Fentons reaction. Figure shows two catalytic cycles taking place
during this process. Electrochemical reactions 2.14 and 2.15 can take place when
the aqueous solution is maintained under oxygen saturation by bubbling
compressed air.
The electro-Fenton process can be considered very efficient and much
cleaner techniques than chemical ones for improving the quality of water resources
and eliminating organic compounds in water.
In this study, a novel electro-Fenton process, in which Fentons reagent
was utilized to produce OH in the electrolytic cell and Fe2+ ion is regenerated via
the reduction of Fe3+ ion on the cathode was investigated.
2.8 OPERATIONAL PARAMETERS
It has been proved that the Fentons reaction is a chain reaction. Various
factors were found to have significant impacts on the electro-Fenton performance.
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2.8.1 pH
pH is one of the most important factors for the electro-Fenton process. It
has been confirmed that the optimum value of pH is 2-4. In addition, when the pH
increases, the iron ions especially the Fe3+ precipitate. Therefore, the amount of
catalyst of Fentons reaction decreases. When pH is lower than 2, H2O2 cannot be
effectively decomposed to OH by Fe2+. This can be explained that in lower pH, the
scavenging effect of the OH by H+ is severe to form an ozonium ion such as H3O2
+; result in reducing the generation of OH (Sun et al., 2008). H3O2 + is electrophilic
leading to the decreasing rate of reaction between H2O2 and Fe2+. The optimum pH
for removal aniline and 2,6 dimethylaniline was 2 (Anotai et al., 2006; Ting et al.,
2009). At the pH above 3 the composition rate of synthetic dyes decreased
because the oxidation potential of OH and also the dissolved fraction of iron
species decrease with increasing pH (Panizza and Cerisola, 2009).
In fact, the optimum pH indicates a disadvantage of electro- Fenton
process because the pH of most water is not within the optimal range. There are
two ways to decrease the pH of wastewater. One is to add acid, and then other is to
mix the target wastewater with some acidic wastewater. Some researchers
investigated the wastewater treatment at neutral pH and the organics can also be
removed successfully. But, in that case, the wastewater is treated mainly by
coagulation rather than by degradation of OH
2.8.2 DISTANCE BETWEEN ELECTRODES
The decrease of the distance between the electrodes leads to a
decrease of the ohmic drop through the electrolyte and then an equivalent decrease
of the cell voltage and energy consumption (Fockedey and Lierde, 2002). It can be
concluded that the closer the electrode are, the better the performance. However, it
is necessary to keep appropriate distance between the electrodes for installation
and avoidance of short circuit between anode and cathode.
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2.8.3 TIME
Time is one of the important parameters in the electro Fenton treatment
of waste water. The treatment efficiency, COD, Turbidity and Colour removal is
progressive as the time increases. And after a period of time it reaches a stable
point after which there is very low or no removal of COD.
2.8.4 H2O2 CONCENTRATION
H2O2 Concentration is a crucial factor for electro Fenton treatment.
Although Fe2+ can react with H2O2 to generate OH and greater OH radicals could
be generated with increasing Fe2+ concentration. Fe2+ and H2O2 cannot be
excessive unilaterally because of the occurrence of undesired side reactions
(reaction 2.2 and 2.6). In reaction 2.6, the HO2 is also an oxidant, but has an
oxidation potential much less than OH. COD removal efficiency increased with the
increasing Fe2+ to H2O2 molar ratio (Zhang et al., 2007). Increasing the H2O2
concentration from 10 to 25 mM increased the removal efficiency, 46% of 2,6-
dimethyaniline but increase from 25 to 30 mM decrease in removal efficiency , 35%
(Ting et al., 2009).
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CHAPTER 3
MATERIALS AND METHODS
This chapter deals with material and methods involved in Electro Fenton
treatment, coagulation and water parameter analysis. The parameters like pH, TDS,
COD, BOD, Turbidity, Color, Sulphide and chloride contents are analyzed.
3.1 METHODOLOGY
Wastewater from poultry processing industry was collected from poultry
processing industry and stored at refrigerated conditions at pH 2. Initial
characteristics of the wastewater were analysed. And after adjusted to necessary
pH the electro fenton treatment was carried out. Then characteristics of the treated
water was analysed and optimisation was carried out. And then combined
coagulation and electro fenton was done and the results were compared.
3.1.1 PROCESS FLOW CHART
Raw wastewater collection
Storage of wastewater at pH=2 under refrigerated condition
Study of initial characteristics
Electro fenton treatment
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Optimisation
Combined coagulation and Electro fenton
Analyse and compare the results
3.2 ELECTRO FENTON REACTOR
The reactor used in this study is a batch type lab scale reactor made of
glass. The total volume of this reactor is 500ml. And 300 ml of waste water is
measured and treated in this reactor for specified operational parameters. pH,
Electrode distance, time and amount of H2O2 are the parameters changed and
studied in this experiment. pH is changed using 0.1N HCl and 0.1NaOH with the
help of digital pH meter. A constant DC current of 0.1 Ampere is maintained
throughout the treatment with the help of lab scale Regulated Power Supply (RPS).
Iron is used as electrode in this treatment to produce Fe2+ ions. Effective electrode
area is about 42cm2.
3.3 COAGULATION
In wastewater treatment coagulation process is particles adhesion
process with formation of large flocs, as a result of addition of a chemical reagent
(coagulating agent) for the purpose of destabilization of suspended colloidal
particles and their subsequent coagulation (aggregation). In this experiment alum
(aluminium sulphate) is used for coagulating agent. Alum is easily available and
cheap in cost. And optimum amount of alum for coagulating meat industry
wastewater is found to be 250 mg/L (Vanerkar A. P. et al).
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3.4 PHYSIOCHEMICAL ANALYSIS
3.4.1 CHEMICAL OXYGEN DEMAND (COD)
Chemical oxygen Demand test is used to indirectly measure the amount
of organic compound in water. It is expressed in mg/L which indicates the amount
of oxygen consumed per litre of solution for complete oxidation of pollutants in the
solution.
The organic matter present in the sample gets oxidized completely by
potassium dichromate (K2Cr2O7) in the presence of sulphuric acid (H2SO4), silver
sulphate (AgSO4) and mercury sulphate (HgSO4) to produce CO2 and H2O. The
sample is refluxed with known amount of K2Cr2O7 in sulphuric acid medium and the
excess of K2Cr2O7 in determined by titration against ferrous ammonium sulphate,
using ferroin as an indicator. The amount of O2 required oxidizing the organic
matter.
Take 1 ml of sample in two COD vials and 1 ml of distilled water in
another COD vial. Add 10 ml of 0.25N K2Cr2O7 to all the COD vials. Add 11 ml of
sulphuric acid-silver sulphate reagent to all the vials. Add a pinch of mercury
sulphate to all the vials. Place all the vials in COD digester and digest it at 80C for
2 hours. After digestion transfer the contents to conical flasks and add 33 ml of
distilled water and 3 drops of ferroin indicator to each of the conical flasks. Then
titrate it against 0.1N ferrous ammonium sulphate solution. The end point is sharp
colour change from blue green to reddish brown.
Chemical Oxygen Demand = A B N 8 1000
Volume of sample taken mg/L
A Blank titre value
B Sample titre value
N Normality of ferrous ammonium sulphate
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And COD removal is calculated using the formula
COD removal percentage = COD of RWW COD of treated wastewater
COD of RWW*100
RWW Raw wastewater
3.4.2 BIOLOGICAL OXYGEN DEMAND (BOD)
The Biological oxygen demand is a chemical procedure for determining
the amount of dissolved oxygen needed by the aerobic organisms in a water body
to break the organic materials present in the given water sample at certain
temperature over a specific period of time. BOD is the principle test to give an idea
of biodegradability of any sample and the strength of the waste. Hence the amount
of pollution can be easily measured.
The sample is filled in an airtight bottle and incubated at specific
temperature for five days. The dissolved oxygen (DO) content of the sample is
determined before and after five days of incubation at 20 C and the BOD is
calculated from the difference between initial and final DO. The initial DO is
determined shortly after the dilution is made all the oxygen uptake occurring after
this measurement is included in the BOD measurement.
Add 10 ml of sample to each of two BOD bottles and fill the remaining
quantity with the dilution water. Dilution water is prepared by adding 5ml of Calcium
chloride solution, 5ml of magnesium sulphate solution, 5 ml of ferric chloride
solution and 5ml of phosphate buffer solution to five litres of high quality organic
free water and aerated for 12 hours and allowing it to stabilize by incubating it at 20
C for four hours. Then add dilution water alone to another two BOD bottles (for
blank). Preserve one of the sample and blank solution at in a BOD incubator at 20
C for five days. Measure the dissolved oxygen content of that blank and sample
solution by digital DO meter (for initial DO and blank correction). And after five days
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measure the dissolved oxygen content of stored sample and blank bottles (for DO
after five days and blank correction).
Biochemical Oxygen Demand = ((DO-D5-BC) Volume of the diluted sample)
mg/L
Volume of the sample taken
DO Initial DO of the diluted sample, mL
D5 DO at the end of 5 days for the diluted sample, mL
BC Blank correction (blank initial - blank final), mL
And BOD removal percentage is calculated using the formula,
BOD removal percentage = (BOD of raw wastewater BOD of treated wastewater) 100
BOD of raw wastewater 3.4.3 SULPHATE ESTIMATION
Sulphate content is estimated by gravimetric method. Sulphate is
precipitated as barium sulphate on reacting with barium chloride in the presence of
hydrochloric acid. The precipitate barium sulphate is dried, ignited and weighed as
BaSO4.
BaCl2 + SO42- BaSO4 + 2Cl-
Take 200 ml of sample in a beaker and adjust the pH of the sample to
4.5 to 5.0 with HCl. Then add additional 2 ml HCl. Boil this solution for one minute
and add 10 ml of hot barium chloride slowly using a pipette. Keep the beaker on a
water to digest the precipitate at 80 to 90 C for two hours. Filter the contents of the
beaker through an ashless filter paper. And place the filter paper in a previously
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weighed crucible and char the filter paper by heating with a loosely closed lid on the
top. And weigh the ash in the crucible for amount of BaSO4.
mg/L sulphate as SO42- =
mg BaSO 4
Vol .Sample taken in ml 411.5
3.4.4 CHLORIDE ESTIMATION
Silver nitrate reacts with chloride ions to form silver chloride. The
completion of reaction is indicated by red colour produced by the reaction of silver
nitrate with potassium chromate solution which is added as an indicator.
AgNO3 + Cl AgCl + NO3-
2AgNO3 + K2CrO4 Ag2CrO4 + 2KNO3
Take 100 ml of sample in a conical flask. Adjust the pH of the sample in
the range of 7 to 9.5 using sulphuric acid or sodium hydroxide. Add 1ml of
potassium chromate as indicator. Titrate against standard silver nitrate solution until
a slight perceptible reddish colour persists.
Chloride (Cl-) mg/L = Sample titre Blank titre Normality of AgNO 335.451000
ml of sample taken for estimation
3.4.5 COLOUR REMOVAL MEASUREMENT
To measure the colour reduction efficiency the max of filter raw waste
water is calculated using the UV spectrometer. And it is found to be 403nm. Then at
this wave length the absorbance of treated sample is measured. And colour
reduction percentage is calculated using the formula,
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Colour removal percentage
=(Absorbance of RWW Absorbance of treated wastewater)
Absorbance of RWW 100
RWW Raw wastewater 3.4.6 pH
The pH was determined by using a digital pH meter. The pH meter was
standardized with double distilled water of pH 7.0 and buffers at pH 4.0.
3.4.7 TURBIDITY
The turbidity was measured using the digital turbidity meter. And it was calibrated using standard naphthalene solution. 3.4.8 TDS
TDS was measured using hand TDS meter. It was calibrated using
standard sodium chloride solution.
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CHAPTER 4
RESULTS AND DISCUSSION
In this chapter the results and discussions of the study are presented. It
deals with the raw water characteristics, preliminary studies, optimisation of electro
fenton treatment and combination of coagulation and electro fenton and
comparisons.
4.1 INITIAL WASTEWATER CHARACTERISTICS
pH 7.4
Chemical oxygen demand 4960 mg/L
Biological oxygen demand 2800 mg/L
Turbidity 210 NTU
Sulphate 600 ppm
Chloride 665 ppm
Protein 1160ppm (1.16gm/L)
TDS 1800 ppm
Table 4.1 Initial water characteristics
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Initial analysis of wastewater shows that it has very high values of COD
and BOD. So it has high amount of pollutant in it. And Turbidity value is about 210
NTU which shows that it has high amount of suspended solid particles than the
normal water. It is found that the wastewater has only 1.16gm/L of protein. And
salts like sulphate, chloride values are slightly above the normal water value. TDS
value was about 1800ppm.
4.2 POSSIBILITY FOR PROTEIN RECOVERY
The amount of protein present in the wastewater is very low (1.16gm/L).
It is due to efficient screening of wastewater in industries before discharge. And the
screened solid particles are subjected to rendering process and are converted into
useful by products. And most of the protein present in the wastewater is water
soluble hemeprotein. So only there is very low amount of protein is discharged
through wastewater. If some more water is used for cleaning process then
obviously the amount of protein in the wastewater is going to decrease. So recovery
of protein from the wastewater is not feasible as it built up unnecessary increase in
cost.
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4.3 PRELIMINARY STUDIES
The preliminary analysis is done to study whether the electro fenton
treatment is suitable for treatment of poultry wastewater and to screen out the
parameters and their range which can give high treatment efficiency for the
treatment.
10
20
30
40
50
60
70
0 1 2 3 4 5 6 7 8
Rem
ov
al
Eff
icie
ncy
%
pH
pH Vs Removal Efficiency
pH Vs COD
removal
pH Vs
Turbidity
removal 40
45
50
55
60
65
70
75
80
85
0 30 60 90 120R
emo
va
l E
ffic
ien
cy %
Time (min)
Time Vs Removal Efficiency
Time Vs
COD
removal
Time Vs
Turbidity
removal
Time- 15min
H2O2- 5ml
ED- 3cm
Time- 15min
H2O2- 5ml
ED-3cm
Fig. 4.2a Preliminary analysis pH Vs
Removal Efficiency
Fig. 4.2b Preliminary analysis Time Vs
Removal Efficiency
-
23
From the preliminary analysis we come to know that all the parameters
have considerable effect on the treatment efficiency of electro fenton. For pH the
maximum COD and turbidity removal is obtained in the range 2-4. And the treatment
efficiency increases with increase in time till 90 min after which it tends to reach a
stable condition. So the time range for maximum removal is selected as 75-105min.
For electrode distance and amount of hydrogen peroxide the maximum removal of
turbidity and COD is achieved in the range 2-4cm and 10-20ml respectively.
40
50
60
70
80
90
100
0 2 4 6
Rem
ov
al
Eff
icie
ncy
%
Electrode Distance (cm)
Electrode Distance Vs Removal
Efficiency
Electrode
Distance Vs
COD
removal
Electrode
Distance Vs
Turbidity
removal
80
82
84
86
88
90
92
94
0 5 10 15 20 25
Rem
ov
al
Eff
icie
ncy
%Hydrogen Peroxide (ml)
Amount of Hydrogen peroxide Vs
Removal Efficiency
H2O2 Vs
COD
removal
H2O2 Vs
Turbidity
removal
pH- 3
Time- 90min
H2O2- 5ml
pH- 3
Time- 90min
H2O2- 5ml
Fig. 4.2c Preliminary analysis ED Vs
Removal Efficiency
Fig. 4.2d Preliminary analysis H2O2 Vs
Removal Efficiency
-
24
4.4 OPTIMISATION
4.4.1 pH OPTIMISATION
Interactive effect of pH with other parameters for the removal of
Chemical oxygen demand is shown in this figure. The maximum removal of COD is
obtained at the pH 3.
This optimum pH is a disadvantage for electro fenton treatment because
the pH of effluent is around neutral pH. So acid has to be added to get this optimum
60
65
70
75
80
85
90
95
0 2 4 6
CO
D r
em
ov
al
%
pH
ED=1cm
ED=2cm
ED=3cm
60
65
70
75
80
85
90
95
0 2 4 6
CO
D r
em
ov
al
%pH
H2O2=10ml
H2O2=15ml
H2O2=20ml
60
65
70
75
80
85
90
95
0 2 4 6
CO
D r
em
ov
al
%
pH
Time=75min
Time=90min
Time=105min
Fig. 4.3a Effect of pH with other parameters for COD
removal
-
25
pH. Adding incoming water with the treated water can be a solution to decrease the
pH of wastewater.
In the above figure the interactive effect of pH with electrode distance,
volume of hydrogen peroxide and time for the turbidity removal is shown. The
maximum turbidity removal is achieved at pH 3.
60
65
70
75
80
85
90
95
0 2 4 6
Tu
rbid
ity
Rem
ov
al
%
pH
ED=1cm
ED=2cm
ED=3cm
60
65
70
75
80
85
90
95
0 1 2 3 4 5
Tu
rbid
ity
Rem
ov
al
%
pH
H2O2=10ml
H2O2=15ml
H2O2=20ml
60
65
70
75
80
85
90
95
0 2 4 6
Tu
rbid
ity
Rem
ov
al
%
pH
Time=75min
Time=90min
Time=105min
Fig. 4.3b Effect of pH with other parameters for turbidity
removal
-
26
The effect of pH with other parameters for colour removal is shown in
the above figure. And the maximum colour removal is achieved in pH 3.
So pH 3 is taken as optimum pH for the electro fenton treatment of
poultry wastewater. The decrease in pH below 3 affects the conversion of Fe3+ to
Fe2+. So there is decrease in efficiency of the treatment. Increase in pH will lead to
the production of ferric hydroxide which is undesirable and decrease the efficiency
of treatment.
60
65
70
75
80
85
90
95
100
0 1 2 3 4 5
Co
lou
r R
emo
va
l E
ffic
ien
cy %
pH
ED=1cm
ED=2cm
ED=3cm
60
65
70
75
80
85
90
95
100
0 2 4 6
Co
lou
r R
emo
va
l E
ffic
ien
cy %
pH
H2O2=10
ml
H2O2=15
ml
82
84
86
88
90
92
94
96
0 2 4 6
Co
lou
r R
emo
va
l E
ffic
ien
cy %
pH
Time=75 min
Time=90min
Time=105min
Fig. 4.3c Effect of pH with other parameters for colour removal
-
27
4.4.2 ELECTRODE DISTANCE OPTIMISATION
Electrode distance is an important parameter for electro fenton
treatment. If the distance is low there is decrease in power consumption because of
decrease in ohmic drop and vice versa. Also it is necessary to keep certain
distance between the electrodes to prevent short circuit.
From this interactive study of effect of electrode distance with other
parameter we get the maximum colour removal at electrode distance of 2cm.
60
65
70
75
80
85
90
95
0 1 2 3 4
CO
D r
emo
va
l ef
fici
ency
%
Electrode distance (cm)
pH=2
pH=3
pH=4
60
65
70
75
80
85
90
95
0 1 2 3 4
CO
D r
em
ov
al
effi
cien
cy %
Electrode distance (cm)
H2O2=10ml
H2O2=15ml
H2O2=20ml
80
82
84
86
88
90
92
94
0 1 2 3 4
CO
D r
em
ov
al
effi
cien
cy %
Electrode distance (cm)
Time=75min
Time=90min
Time=105min
Fig. 4.4a Effect of Electrode distance with other parameters for COD
removal
-
28
From this graph we come to know that at the electrode distance of 2 cm
we can obtain the maximum turbidity removal.
60
65
70
75
80
85
90
95
0 1 2 3 4
Tu
rbid
ity
rem
ov
al
effi
cien
cy %
Electrode distance (cm)
pH=2
pH=3
pH=4
60
65
70
75
80
85
90
95
0 1 2 3 4
Tu
rbid
ity
Rem
ov
al
effi
cien
cy %
Electrode distance (cm)
H2O2=10ml
H2O2=15ml
H2O2=20ml
78
80
82
84
86
88
90
92
0 1 2 3 4
Tu
rbid
ity
rem
ov
al
effi
cien
cy %
Electrode distance (cm)
Time=75min
Time=90min
Time=105min
Fig. 4.4b Effect of Electrode distance with other parameters for
turbidity removal
-
29
The maximum colour removal is obtained at the electrode distance of
2cm. So the optimum electrode distance is 2cm. And overall treatment efficiency is
high at this electrode distance.
60
65
70
75
80
85
90
95
100
0 1 2 3 4
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Electrode Distance (cm)
pH=2
pH=3
pH=4
80
82
84
86
88
90
92
94
96
0 2 4
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Electrode Distance (cm)
H2O2=10
ml
H2O2=15
ml
82
84
86
88
90
92
94
96
0 1 2 3 4
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Electrode Distance (cm)
Time=75min
Time=90min
Time=105min
Fig. 4.4c Effect of Electrode distance with other parameters for colour
removal
-
30
4.4.3 AMOUNT OF HYDROGEN PEROXIDE OPTIMISATION
The amount of hydrogen peroxide is a very important factor for electro
fenton treatment. The treatment efficiency increases with the increase in amount of
hydrogen peroxide. But if it exceeds a level it will lead to unwanted side reactions.
And favours the production of ozonium ion which is a very weak oxidizing agent
compared to hydroxyl ion. From the above figure the maximum removal of COD is
obtained at 50ml/L of hydrogen peroxide.
60
65
70
75
80
85
90
95
0 10 20 30
CO
D r
em
ov
al
effi
cien
cy %
Amount of H2O2 (ml)
pH=2
pH=3
pH=4
60
65
70
75
80
85
90
95
0 10 20 30C
OD
rem
ov
al
effi
cien
cy %
Amount of H2O2 (ml)
ED=1cm
ED=2cm
ED=3cm
80
82
84
86
88
90
92
94
0 10 20 30
CO
D r
em
ov
al
effi
cien
cy %
Amount of H2O2 (ml)
Time=75min
Time=90min
Time=105min
Fig. 4.5a Effect of Hydrogen peroxide with other parameters for COD
removal
-
31
From the above graph we come to know that the maximum turbidity
removal is achieved at 50ml/L of hydrogen peroxide.
60
65
70
75
80
85
90
95
0 10 20 30
Tu
rbid
ity
rem
oa
l ef
fici
ency
%
Amount of H2O2 (ml)
pH=2
pH=3
pH=4
60
65
70
75
80
85
90
95
0 5 10 15 20 25
Tu
rbid
ity
rem
ov
al
effi
cien
cy %
Amount of H2O2 (ml)
ED=1c
m
ED=2c
m
80
82
84
86
88
90
92
0 5 10 15 20 25
Tu
rbid
ity
rem
ov
al
eff
icie
ncy
%
Amount of H2O2 (ml)
Time=75min
Time=90min
Time=105min
Fig. 4.5b Effect of Hydrogen peroxide with other parameters for turbidity
removal
-
32
The maximum colour removal is also achieved at 50ml/L of hydrogen
peroxide. So the best treatment efficiency for the electro fenton treatment of poultry
waste water is achieved at 50ml/L of hydrogen peroxide.
80
82
84
86
88
90
92
94
96
0 10 20 30
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Amount of H2O2 (ml)
pH=2
pH=3
pH=4
80
82
84
86
88
90
92
94
96
0 10 20 30
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Amount of H2O2 (ml)
ED=1cm
ED=2cm
ED=3cm
78
80
82
84
86
88
90
92
94
96
0 5 10 15 20 25
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Amount of H2O2 (ml)
Time=75min
Time=90min
Time=105min
Fig. 4.5c Effect of Hydrogen peroxide with other parameters for colour
removal
-
33
4.4.4 TIME OPTIMISATION
The efficiency of the electro fenton treatment increases with increase in time.
But after a certain period of time it reaches a stable value. Beyond that time there is no COD
removal or very low removal.
From the graph we come to know that up to 90min there is increase in COD
removal. And after that time there is no significant change in removal of COD.
78
80
82
84
86
88
90
92
94
0 50 100 150
CO
D r
em
ov
al
effi
cien
cy %
Time (min)
pH=2
pH=3
pH=4
80
82
84
86
88
90
92
94
0 50 100 150
CO
D r
em
ov
al
effi
cien
cy %
Time (min)
ED=1cm
ED=2cm
ED=3cm
80
82
84
86
88
90
92
94
0 50 100 150
CO
D r
em
ov
al
effi
cien
cy %
Time (min)
H2O2=10ml
H2O2=15ml
H2O2=20ml
Fig. 4.6a Effect of Time with other parameters for COD removal
-
34
The turbidity removal increases with increase in treatment time up to 90min.
After 90 min there is no significant increase in turbidity removal. So treatment of wastewater
more than 90min will lead to unnecessary loss in time.
60
65
70
75
80
85
90
95
0 50 100 150
Tu
rbid
ity
rem
ov
al
effi
cien
cy %
Time (min)
pH=2
pH=3
pH=4
78
80
82
84
86
88
90
92
0 50 100 150
Tu
rbid
ity
rem
ov
al
effi
cien
cy %
Time (min)
ED=1c
m
ED=2c
m
80
82
84
86
88
90
92
0 50 100 150
Tu
rbid
ity
rem
ov
al
effi
cien
cy %
Time (min)
H2O2=10ml
H2O2=15ml
H2O2=20ml
Fig. 4.6b Effect of Time with other parameters for turbidity removal
-
35
The colour removal tends to increase with increase in time till 90min. But after
90min there is no significant increase in colour removal. Prolonging the treatment time more
than 90min will lead to unnecessary waste of time. So the optimum time for electrode fenton
treatment is taken as 90min.
82
84
86
88
90
92
94
96
0 50 100 150
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Time (min)
pH=2
pH=3
pH=4
82
84
86
88
90
92
94
96
0 50 100 150
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Time (min)
ED=1cm
ED=2cm
ED=3cm
78
80
82
84
86
88
90
92
94
96
0 50 100 150
Co
lou
r R
emo
va
l E
ffic
ien
cy %
Time (min)
H2O2=10ml
H2O2=15ml
H2O2=20ml
Fig. 4.6c Effect of Time with other parameters for colour removal
-
36
4.5 OPTIMISED POINT
From the above graphs the optimised point is found as
Parameter Optimised point
pH 3
Electrode distance 2
Hydrogen peroxide 15ml/300ml (50ml/L)
Time 90 min
4.6 TREATED WATER CHARACTERISTICS
Characteristics
Raw waste water
Electro Fenton
Coagulation and Electro Fenton
Chemical Oxygen Demand (mg/L) 4960
360
(93% reduction)
160
(96.8% reduction)
Biological Oxygen Demand (mg/L) 2800
200
(92.85% reduction)
60
(97.85% reduction)
Turbidity (NTU) 210
19
(91% reduction)
7
(96.67% reduction)
Sulphate (ppm) 600
320
(46.67% reduction)
440
(26.67% reduction)
Chloride (ppm) 665
260
(60.9% reduction)
180
(72.93% reduction)
TDS (ppm) 1800
990
(45% reduction)
840
(53.33% reduction)
Amount of sludge production - 7.8 gm 36.7 gm
Table 4.3 Characteristics of treated water treated by Electro fenton and
combined coagulation with electro fenton
Table 4.2 Optimised point for electro fenton treatment of poultry wastewater
-
37
4.7 ELECTRO FENTON AND COMBINED COAGULATION WITH ELECTRO
FENTON
The above figure shows a comparison between electro fenton and combined
coagulation with electro fenton. It shows that electro fenton has a good effect for the
treatment of poultry wastewater. And combined coagulation with electro fenton is more
efficient than electro fenton. But the sludge production is more in this combined technique.
So this sludge has to be treated further through landfill or some other techniques. Also the
sulphate content of the water treated through the combined technique is higher because the
addition of alum (aluminium sulphate) which have certain interruption in the sulphate
content of the treated water.
86
88
90
92
94
96
98
100
COD BOD Turbidity Colour
Rem
ov
al
%
EF Vs Combined Coagulation and EF
Electro Fenton
Coagulation and Electro
fenton
Fig. 4.7 Characteristics of treated water treated by Electro fenton and
combined coagulation with electro fenton
-
38
CHAPTER 5
SUMMARY AND CONCLUSION
Wastewater from the meat industry is very difficult to purify due to its specific
characteristics; irregular scatter; and considerable amounts &organic, mineral and biological
matter. This investigation shows that electro fenton treatment can be successfully applied to
the treatment of poultry effluent with minimal sludge production. Combined coagulation
with electro fenton is more efficient when compared to electro fenton. But the sludge
production is higher in this combined technique which has to be disposed or treated further
through landfill or some other technique. And the waste water has very low amount of
protein content. So the recovery of protein from the wastewater is not feasible as it increases
the cost of recovery.
-
39
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