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293
INTRODUCTION
The confectionery industry is one of the most
widespread and important industries around the
world. It manufactures sweets including choco-
late confectionery and gum products which are
characterized by signicant amounts of sugar
and sugar substitutes, cocoa, fats, emulsiers,
and avours used in the production process (Ed-
wards 2000; El-kalyoubi et al. 2011; García-Mo-
rales et al. 2018).
The development of dierent industry branch-
es has signicantly improved people’s qual-
ity of life in many aspects. However, industrial
plants developing so numerously have started to
emit a lot of water pollution (Próba and Wolny
2013). In many cases, sewage is discharged
into rivers without any purication (Ntuli et al.
2011) which causes eutrophication, due to the
high concentration of phosphorus and nitrogen
(Demirel et al. 2005; Qasim and Mane 2013) and
causes pollution of waters which could be used as
a source of drinking water. The pollution of wa-
ter caused by sewage input is a serious threat for
people and animals (Elhassadi 2008).
Industrial waste consisting of a lot amount of
organic compounds uses the oxygen dissolved in
water to biochemical disintegration of these sub-
stances. The excessive oxygen usage by sewage
may result in its total reduction in receiving wa-
ter. This inuences on generating anaerobic con-
ditions which cause the extinction of aerobe and
blocks the oxygen process of sewage self-clean-
ing. Water de-oxidation has also a bad inuence
on organisms living in the aquatic environment
(Gromiec et al. 2014).
Water protection from industrial pollu-
tions is one of the basic elements of sustainable
Journal of Ecological Engineering Received: 2019.07.30
Revised: 2019.08.23
Accepted: 2019.09.16
Available online: 2019.09.24
Volume 20, Issue 9, October 2019, pages 293–304
https://doi.org/10.12911/22998993/112557
Wastewater Treatment Methods for Euents from
the Confectionery Industry – an Overview
Magdalena Zajda1, Urszula Aleksander-Kwaterczak1*
1 AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection; al.
A. Mickiewicza 30, 30-059 Krakow, Poland
* Corresponding author’s e-mail: aleksa@geolog.geol.agh.edu.pl
ABSTRACT
Wastewater from the confectionery industry is characterized by daily and seasonal variability of composition and
quantity which adversely aects the process of their disposal. Confectionery plants discharge about 300-500 m3
per month of technological wastewater. Sewage from the confectionery industry belongs to biologically degrad-
able. It is characterized by high values of chemical oxygen demand (COD) and biological oxygen demand (BOD).
The article reviews various methods used to treat wastewater from the confectionery industry. Attention was
paid to the applicability of a particular method, its advantages and disadvantages and the costs of implementa-
tion. The technology of industrial wastewater treatment uses both mechanical and physicochemical methods as
well as biological ones. Techniques of sewage treatment usually consist of several stages which use dierent
processes. Low-cost materials such as natural minerals, agricultural waste, industrial waste, biosorbents, and
others contribute to the improvement of aerobic sewage conditions. The main weakness of typical sewage treat-
ment plants is their large area, high investment, and exploitation costs. Therefore, a good solution may be the
use of the membrane biological reactor which combines the classical technique of activated sludge and ltration
on micro-ltering membranes.
Keywords: confectionery industry, wastewater treatment, biological oxygen demand, chemical oxygen demand,
low-cost material
Journal of Ecological Engineering
294
development. In order to achieve this, it is nec-
essary to purify the industrial wastewater more
eciently and to change the technologies to
more friendly to the environment (Rajman 2007;
Qasim and Mane 2013). A good method of con-
trolling water pollution is the monitoring of in-
dustrial plants that discharge sewage directly to
municipal channels. However, the task is often
too expensive especially for largely industrialized
regions (Ntuli et al. 2011). Quite often the costs
that a production plant has to pay for the emission
of poor quality sewage are very high. Therefore,
factories are more and more often using dierent
methods of sewage pretreatment.
The work reviews various methods used to
treat wastewater from the confectionery indus-
try. It was paid attention to the possibilities of
using a particular method and its advantages and
disadvantages.
CHARACTERISTIC OF WASTEWATER
FROM THE CONFECTIONERY INDUSTRY
The main source of sewage in the confection-
ery industry is the cleaning process of the installa-
tion, so the amount of sewage generated depends
on its frequency. For this reason, it is character-
ized by daily and seasonal variations in the com-
position and the quantity. This aects the process
of its disposal. The confectionery plants discharge
about 300-500 m3 per month of technological
wastewater (Rucka et al. 2012). This sewage is
biodegradable and it consists primarily of organic
compounds and suspensions which aects the high
values of chemical oxygen demand (COD) and
biological oxygen demand (BOD) (Krzanowski et
al. 2008). The COD index has usually values with-
in the limits of 1000-12000 mg O2/L, while BOD5
up to 500-8000 mg O2/L (Table 1). The organic
substances that are contained in wastewater are
mainly sugars, fats, and dyes (Colic et al. 2009;
Esparza-Soto et al. 2013; García-Morales et al.
2018; Rucka et al. 2012; Qasim and Mane 2013).
Confectionery sewage often contains solutions for
washing and disinfecting agents too, which can
cause changing the pH value and increasing the
content of nitrogen and phosphorus compounds
(Krzanowski et al. 2008).
WASTEWATER TREATMENT METHODS
The treatment of wastewater is a relatively
modern practice. The rst mechanical and biolog-
ical processes designed to treat municipal waste-
water emerged early by the end of the 19th century
(Environmental Protection Agency 1997).
The technology of industrial wastewater treat-
ment uses both mechanical and physicochemical
methods as well as biological ones (Figure 1)
(Bhargava 2016).
Mechanical treatment
Mechanical wastewater treatment, this so-
called rst stage of purication, are intended
to eliminate larger oating and dragged solids,
granular particles with a diameter greater than
0.1 mm, and easily falling suspensions, oils and
fats. This is achieved through the use of grates
and screens that trap and separate solid objects
Table 1. The main properties of sewage from the exemplary confectionery plants
Kind of industry BOD
[mg O2/L]
COD
[mg O2/L]
EC
[μS/cm]
pH
-
NH4
+-N
[mg/L]
P total
[mg/L] Literature
Candy manufacturing plant
in Mexico 8000 2500 ‒ ‒ ‒ ‒ Colic et al. (2009)
Chocolate manufacturing
industry in Mexico ‒3608 750 7.4 ‒ ‒ García-Morales
et al. (2018)
Confectionery plants in
Poland 5400 10,996 633 4.1 28.5 13.2 Rucka et al. (2014)
Food industries (dairy
euent, sweet-snacks and
ice-cream), India
442-523 8960-11,900 794-1082 5.6-7.1 89-120 78-157 Qasim and Mane
(2013)
Food processing industry
in India 6860 11,220 ‒ 4.1-4.3 ‒ 3.2 Vanerkar et al.
(2013)
Sugar industry, Ethiopia ‒ 3682 ‒ 5.5 ‒ 5.9 Sahu (2017)
Confectionery factory –
sugar line, Turkey ‒ 20,025 680 3.8 ‒ ‒ Ozgun et al. (2012)
Sugar industry, Pakistan 3132 12,211 ‒ 9.5 ‒ ‒ Khan et al. (2003)
Note: ‒ not determined.
295
Journal of Ecological Engineering Vol. 20(9), 2019
from the bulk wastewater. At this stage, pro-
cesses such as ltration, drainage, sedimentation
and otation take place. As a result, the content
of organic compounds in wastewater can be re-
duced by a few percents (Bartkiewicz and Um-
iejewska 2010).
Physicochemical treatment
Sorption
The process of sorption includes two phe-
nomena. The rst of them is adsorption, which
involves the attachment of molecules on the sur-
face of a solid or liquid. The second is the absorp-
tion consisting of the sorption of one substance
by another forming any continuous phase. Meth-
ods using the adsorption process is considered as
one of the most competitive because they are not
complicated and do not require high operating
temperature (Hashemian et al. 2014).
Activated carbon is a material that adsorbs
organic compounds very well (Dakhil 2013). This
is due to its large surface area, porosity and resist-
ance to chemical and thermal changes (El-Dars et
al. 2014). For this reason, it is the most versatile
adsorbent used in the wastewater treatment pro-
cess. It reduces BOD and COD values by more
than 90% (Devi et al. 2008; Nayl et al. 2017; Sa-
nou et al. 2016; Yamina et al. 2013). The main
disadvantage of its use is the high cost of produc-
tion (El-Dars et al. 2014) and regeneration as well
as disposal problems. That’s why scientists search
for the cost-eective and more environmentally-
friendly sorbents with similar properties as car-
bon (Carvalho et al. 2011).
The ideal adsorbents should be solids with a
large surface area, porosity, inertness, and good
physical and chemical properties (Paprowicz
1990; Parande et al. 2009). As low-cost adsor-
bents natural minerals (bentonite, kaolinite, zeo-
lites, silica beads), agricultural waste (eggshells,
corn cobs, chicken feathers, rice husks, coconut
shells), industrial by-products, biosorbents (chi-
tosan, peat, biomass) and others (e.g. starch, cy-
clodextrin, cotton) were tested (Al-Jlil 2009; Ar-
in et al. 2017; Carvalho et al. 2011; Parande et
al. 2009). It was found that also such elements
as wool, sawdust, cocoa shell, sugar beet pulp,
distillery sludge or maple saw dust can be eec-
tive in metals reduction and the improvement of
aerobic conditions in wastewater. Furthermore,
metakaolin and carbon made from dates nuts
and tamarinds in the condition of neutral pH can
signicantly improve the oxygen conditions in
wastewater with a high content of organic com-
pounds (Parande et al. 2009). It was also demon-
strated that a perfect absorbent is an active carbon
produced from almond shells and orange peels
wastes (Hashemian et al. 2014).
It was observed that active carbon produced
by activation with phosphoric acid (H3PO4) from
olive stones has a very well developed pore struc-
ture, which will result in the high level of pollu-
tion sorption (Yakout and Sharaf El-Deen 2016).
The low-cost absorbents as coconut tree sawdust,
silk cotton hull, sago waste, maize cob, and ba-
nanas were also used from preparation an active
carbon. It was generated to remove high-density
metals and dyes from water solution. The results
of the experiment prove that all kind of carbon
Fig. 1. Wastewater treatment methods
Journal of Ecological Engineering
296
was eective in the removal of pollution from
water (Henze et al. (Eds.) 2008).
Qasim and Mane (2013) conducted experi-
ments of clearing the sewage coming from the
production of sweets and ice cream with the us-
age of powdered activated charcoal as absorbent.
They proved that such kind of carbon can sig-
nicantly improve oxygen conditions of sewage.
It was also showed that biological wastes from
squid processing can reduce BOD values by 90-
95% (Park et al. 2001).
The advantages and disadvantages of the ad-
sorption process in the BOD and COD reduction
are presented in Table 2.
Coagulation and occulation
In wastewater treatment, these methods are
mainly used to remove suspended solids and or-
ganic compounds. The eectiveness of processes
depends on the selection of suitable coagulant.
The most popular are aluminium and iron salts as
well as active silica (Bhargava 2016). In the case
of wastewater from the food industry, the use of
ferrous sulphate as a coagulant can cause a reduc-
tion of BOD from about 33% to 58% and COD
from about 30% to 53%. While the use of limes
led to slightly larger improvement aerobic con-
ditions (BOD: 34%-66% and COD 32%-59%)
(Vanerkar et al. 2013).
Vanterkar et al. (2013) conducted an experi-
ment in which they used as a coagulant: lime,
alum, ferrous sulphate or ferric chloride in com-
bination with dierent polyelectrolytes as lime
200 mg/L + anionic-synthetic polyelectrolyte
(Magnaoc - E-207), lime 200 mg/L + nonionic
- synthetic polyelectrolyte (Zetag - 7650) and
lime 300 mg/L + cationic - synthetic polyelec-
trolyte (Oxyoc - FL-11). The analysis showed
that 0.3 mg/L Magnaoc E-207 in combination
with the optimal dose of lime 200 mg/L, was
very eective in the reduction of COD - 67.6%
and BOD - 71.0%.
The widely available and economical ma-
terials as lime, alum, polymer, and dried leaves
were also tested as coagulants for the reduction
of BOD and phosphorus in wastewater after bio-
logical treatment. It has been shown that the ma-
terials do not change the pH but has contributed
to a signicant reduction of the phosphorus con-
centration and BOD ratio up to 80-90% (Mortula
et al. 2011). Good coagulants can also be organic
compounds, e.g. “chitosan”, which comes from
shells of some crustaceans. They could be used
to remove organic matter that causes high BOD
levels (Bough 1976). The advantage of this natu-
ral substance is the ability to recover sediment
(Table 3) (Park et al. 2001).
Electrocoagulation
Electrocoagulation (EC) is an electrochemi-
cal technology increasingly used in wastewater
treatment (Mollah et al. 2001; Mollah et al. 2004;
Sahu et al. 2014). The EC is simple and ecient
process in which iron or aluminium anodes that
are electrolytically dissolved are commonly used
(Akbal and Camcı 2011; Mollah et al. 2004). The
production of the coagulating agent is carried out
in situ by electro-oxidation of a sacricial anode
and there is no need to add any chemical coagu-
lants or occulants (Keshmirizadeh et al. 2011;
Thirugnanasambandham et al. 2013).
Investigation of wastewater from the sugar
industry using electrocoagulation with zinc elec-
trodes in a bipolar system shows a signicant
reduction of COD (81%), BOD (89%) and total
solids content (90%) (Byadgi et al. 2017). While
treatment using an electrochemical process with
hybrid iron and aluminium electrodes resulted in
Table 2. The advantages and disadvantages of the adsorption process in the wastewater treatment technology (ac-
cording to Arin et al. 2017; Park et al. 2001)
Advantages Disadvantages
− large BOD and COD reduction
− easy-to-use
− cheap technology
− adsorbent loses its eectiveness over time
− problems with the utilization of waste
Table 3. The advantages and disadvantages of the coagulation and occulation processes in wastewater treatment
technology (according to Arin et al. 2017; Mortula et al. 2011; Park et al. 2001)
Advantages Disadvantages
− good BOD and COD reduction
− cheap technology using natural coagulants
− large amount of sediment generated
− problem with the utilization of waste
297
Journal of Ecological Engineering
the reduction of COD by 90% and of the colour
by 93.5% (Sahu 2017). The integrated electro-
coagulation process using aluminium sacricial
anodes and the sand ltration process as a pre-
treatment of wastewater from the chocolate al-
lowed reducing turbidity, colour and COD by
about 96%, 98% and 39%, respectively. What is
more, hybrid electrodes are safe to operate and
economical (García-Morales et al. 2018).
An analysis of the clearing eectiveness of
articial wastewater from milk powder by the
electrocoagulation method using the aluminum
anode showed a signicant decrease of turbid-
ity, total phosphorus and nitrogen. The eec-
tiveness of COD reaches only 61%. While, the
chemical coagulation with aluminium sulphate
contributed to the improvement of turbidity and
nitrogen, but the eectiveness of phosphorous
reduction, as well as COD, was slightly higher.
The advantage of electrocoagulation over coag-
ulation is because the electrocoagulation process
uses fewer reagents and the wastewater treated
by electrocoagulation has lower conductivity
and neutral pH value, which allows recycled
treated water for some industrial applications
(Tchamango et al. 2010).
The wastewater treatment experiment using
electrocoagulation with aluminum electrodes was
also performed on wastewater from the produc-
tion of sweets and ice cream. After electrocoagu-
lation, the reduction of turbidity reached 100%,
phosphorous of 89% and COD index reduced by
61%, indicating that this technique is the best and
more ecient in treating such type of euents
(Qasim and Mane 2013). Other scientists used
electrocoagulation with the same kind of elec-
trode to separate pollutants from the restaurant
wastewater. The analysis showed that the elec-
trodes eectively remove organic compounds
and can neutralize the pH of sewage (Chen et al.
2000). It was indicated that the pH plays an im-
portant role in determining the removal ecien-
cies of the electrocoagulation process, and the
removal of the COD parameter increases with
increasing of pH to 6.5 (Thirugnanasambandham
et al. 2013).
However, the initial capital expenditures and
projected operating costs of the electrocoagula-
tion process in wastewater treatment are high and
are estimated at USD 140,000 and USD 40,000/
year, respectively (Tab. 4) (Park et al. 2001).
Ozonation
Ozone is a strong oxidant and is easily solu-
ble in water, therefore it is used in the wastewater
treatment processes. Ozonation is most eective
for well-diluted wastewater. In wastewater with
a high concentration of organic compounds, this
process can only be used as a preliminary phase
in the entire treatment technology (https://www.
ozonetech.com).
The experiment involving the oxidation of
raw sewage from the confectionery industry using
ozone was carried out by Benincá et al. (2013). It
was performed in a semi-batch reactor at the tem-
perature of 20ºC for two hours and an ozone mass
ow rate of 1.158 × 10−6 kg/s. At such condition,
a total decrease of TOC was no higher than 60%
and a reduction in the colour of the raw wastewa-
ter to almost 10% was noticed.
Table 5. The advantages and disadvantages of the ozonation process in wastewater treatment technology (accord-
ing to US EPA 1999)
Advantages Disadvantages
− lack of harmful waste
− short time of wastewater contact with ozone
(15-20 minutes)
− weak reduction of high BOD and COD values
− it requires the complicated equipment and a control system
− high operating and maintenance costs
Table 4. The advantages and disadvantages of the electrocoagulation process in wastewater treatment technology
(according to Arin et al. 2017; Park et al. 2001)
Advantages Disadvantages
− minimal chemical additives
− low sludge production
− large reduction suspensions and colour
− simple equipment required
− easy operation and automation
− short retention time
− relatively low reduction of high BOD and COD values
− electrodes require to be regular exchange
− high operating and maintenance costs
Journal of Ecological Engineering Vol. 20(9), 2019
298
The investment costs were estimated at USD
190,000 and annual operating costs at USD
40,000 (Park et al. 2001) (Table 5).
The use of membranes
Membranes can be considered as selective
barriers, allowing the passage of certain constitu-
ents from the mixture and retaining others. The
driving force of transport is the gradient of some
potential, such as pressure, temperature, concen-
tration or electrical potential (Mai 2014). One of
the particular advantages of this process is that
it relies on physical separation, usually with-
out the addition of chemicals. The most popular
membrane treatment technologies are pressure
processes that are divided into microltration,
ultraltration, nanoltration and reverse osmosis
(Van der Bruggen et al. 2003). Table 6 shows the
relationships between the type of membrane, pore
size, type of process, and retained contaminants.
The membrane test was used to treat waste-
water from the calamari processing line with a
very high BOD value (1000-5000 mg/L). The
rst stage of the experiment showed that the sin-
gle-stage test using ultraltration membrane (UF)
did not reduce BOD eectively because proteins
and other organic substances passed through the
membrane. The permeate from the rst stage was
directed to the nanoltration membrane (NF).
This caused the reduction of the BOD to about 300
mg/L. In the two-stage system, the BOD indicator
decreased by over 90% (Park et al. 2001). Ultra-
ltration and nanoltration membranes were also
used for the treatment of wastewater from restau-
rants which served typically Malay foods. De-
pending on membrane type, very high reduction
of COD (up to 97.8%) and turbidity (99.9%) and
strongly removal of BOD5 (86.8%) and conduc-
tivity (82.3%) were found. The restaurant owner
may have the additional benet of reusing treated
wastewater for non-drinking purposes (Zulaikha
et al. 2013). The disadvantage of membrane sys-
tems is that there is about 75% water recovery -
which means that about 25% of the leachate re-
mains (Table 7).
Biological methods
The use of activated sludge
Wastewater treatment with activated sludge
under aerobic conditions is one of the most com-
monly used technologies (Henze et al. (Eds.)
2008; Scholz 2016) but costs associated with the
purchase and operation can be often too high for
industrial applications (Park et al. 2001). The
activated sludge is a biological system in which
both physical processes and biochemical reac-
tions take place. Macroscopically, it is a suspen-
sion consisting of occulating agglomerations of
heterotrophic bacteria. Physical processes occur
on the surface of ocks, which are based on the
adsorption of organic compounds and as a result
Table 6. Characteristics of membranes (according to Ratajczak 2013)
Process: Microltration Ultraltration Nanoltration Reverse osmosis
Emulsion, Colloids, Bacteria
Proteins, Viruses
Dye
Polyvalent ions
Monovalent cons
Simple carbohydrates
Pressure range [MPa] 0.1-0.3 0.3-1.0 0.5-3.0 2.0-5.0
Membrane construction symmetrical, porous asymmetric, porous asymmetric,
composite
asymmetric,
composite
Pore size 0.05-10 µm 0.01-0.05 µm 1.00-8.00 nm solid
Approximate size of
separated molecules 0.1 µm 2.0-20.0 nm 0.001 µm 0.0001 µm
Table 7. The advantages and disadvantages of the membrane in wastewater treatment technology (according to
Park et al. 2001)
Advantages Disadvantages
− lack of chemical additives
− high reduction of BOD and COD using multi-stage systems
− leachates with a high concentration of pollutants
− high operating and maintenance costs
299
Journal of Ecological Engineering Vol. 20(9), 2019
they decompose into smaller fragments. They are
then absorbed by the microbial cells in which
they undergo a further transformation. Bacteria
in the activated sludge produce enzymes that ca-
talyse the series of biochemical reactions, result-
ing in decomposition of inorganic and organic
compounds in wastewater (Scholz 2016). Waste-
water treatment using activated sludge was used
in many confectionery plants.
El Diwani et al. (2000) designed an inte-
grated pilot plant consisting of an equalizer, a
chemical mixer, an aerator, a clarier, a disinfec-
tant tank, and a sand lter for wastewater treat-
ment from the production of gums and sweets.
After the purication process, the BOD index
decreased from 3200 mg/L to 70 mg/L and the
COD from 5000 mg/L to 100 mg/L. Experiments
of wastewater treatment by the activated sludge
were also carried out in the laboratory conditions
using in the periodic operation reactors (SBR).
Three reactors worked in two cycles per day and
included the aeration and sedimentation phase.
The results of the analysis showed over 95% ef-
ciency of COD and BOD removal. The values
of these indexes in treated wastewater were sig-
nicantly lower than the admissible values for
sewage entering into the sewage system (Rucka
et al. 2014).
The main disadvantage of the described tech-
nologies is too high costs, the complicated tech-
nique and extinction of compacted bacteria in the
activated sludge (Park et al. 2001) (Table 8).
Treatment under anaerobic conditions
Anaerobic treatment is based on a microbio-
logical process, such as methane fermentation,
during which properly selected bacterial strains
to convert organic waste contained in sewage into
biogas (methane and CO2). The bacteria involved
in the process are found in anaerobic sludge: oc-
culent and granular.
Many methods of wastewater treatment are
carried out based on anaerobic technologies. An-
aerobic digestion was used to treat not only for
many types of waste but also biosolids (Amani et
al. 2010; Park et al. 2001). The Up-ow Anaero-
bic Sludge Blanket (UASB) reactor has become
very popular in recent years and has been widely
used for the treatment of various kinds of waste-
water (Seghezzo et al. 1998). The advantages of
using this reactor result from high removal e-
ciency even at low temperature, low energy con-
sumption and low space requirements. It is very
useful in the treatment of organic wastewater due
to the high biomass concentration and rich micro-
bial diversity (Liu et al. 2003).
Tanksali (2013) treated wastewater from a
sugarcane factory in the UASB reactor with non-
granular anaerobic activated sludge at the temper-
ature of 26-39°C under the laboratory conditions.
It was obtained the high COD removal eciency
ranged from 80% to 96%, while the maximum
volume of biogas production was 13.72 L/d and
the methane concentration in biogas was 71%.
The same reactor was tested by Atashi et al.
(2010) for treatment the inuent from the sugar
factory. The best level of COD values reduction
that they obtained was 90% at pH=7 and tempera-
ture of 35-38°C.
Park et al. (2001) conducted a pilot treat-
ment of sewage from the squid processing. He
obtained a BOD reduction by about 80%. The
capital equipment costs of this technology were
estimated at USD 490,000 and operating costs at
USD 45,000 per year (Table 9).
DISCUSSION
Many confectionery plants struggle a seri-
ous problem concerning the quality of industrial
wastewater. The confectionery industry contrib-
utes a large extend to the generation of wastewater
Table 8. The advantages and disadvantages of the activated sludge under aerobic conditions in the wastewater
treatment technology (according to Park et al. 2001)
Advantages Disadvantages
− lack of odours
− high reduction of BOD and COD
− complicated technique
− high operating costs
− formation of a large amount of sludge
− sudden increase in volume or change in the composition
of sewage may have a negative eect on the operation of
the process
300
with a high content of organic compounds (sug-
ars, fats, proteins) which result in the increase of
the BOD and COD indices. Industrial wastewater
is generated as a result of cleaning the installation
due to which they are characterized by signicant
quantitative and qualitative volatility. To limit and
control the emission of pollutants into the environ-
ment, most countries have introduced various le-
gal acts regulating the quality and quantity of dis-
charges of pollutants (Ntuli et al. 2011). The Coun-
cil Directive 91/271/EEC applies to the countries
of the European Union concerning the treatment of
municipal wastewater. Its purpose is to protect the
environment against the adverse eects of munici-
pal sewage discharges from some of the industrial
sectors (91/271/EEC). On the other hand, waste-
water re-use standards have been introduced in the
Eastern Mediterranean (CEHA 2006).
Due to the growing limitations of environ-
mental standards, confectionary plants incur huge
costs associated with non-compliance. For this
reason, such plants are looking for an optimal in
terms of the environmental and economic method
of treating sewage.
Various methods have found, to a greater or
lesser extent, their application in the treatment of
wastewater from the confectionery industry. The
selection of methods is inuenced above all by
the eciency of treatment and economic aspects.
In order to obtain the best eciency and comple-
mentarity of wastewater treatment, techniques that
consist of several stages and dierent processes are
used. The integrated process can be an attractive
alternative to the initial treatment of wastewater to
improve the quality of water in conventional treat-
ment methods or it can be used as a pre-treatment
of wastewater (García-Morales et al. 2018).
The multi-phase sewage treatment process
was presented by Al-Jlil (2009). He conducted
research to improve the quality parameters of
domestic sewage using sedimentation, aeration,
sand ltration, active carbon, and chlorination.
The study showed that by applying the dier-
ent physicochemical and biological processes,
the reduction of BOD and COD reached 92.2%
and 97.7%, respectively. Yamina et al. (2013)
showed that initial physicochemical methods can
improve the oxygenic conditions of wastewater.
They used a bi-layer ltration system consisting
of a mixture of active carbon and sand dune. As
a result, rates of BOD and COD reduced by 99%
and 98%, respectively.
Ozgun et al. (2012) also presented a multi-
stage scheme of sewage treatment which comes
from dierent production lines in the confection-
ery industry generated about 170,000 m3/year
of wastewater. The system of wastewater treat-
ment consisted of screens, equalization tanks,
dissolved air otation, an anaerobic expanded
granular sludge bed reactor (EGSB), and a con-
ventional activated sludge system with the sludge
treatment line. The research proved that the re-
duction of COD in an anaerobic reactor reached
88%, while the use of the anaerobic reactor led to
a decrease in COD by 95%. It is promoted the use
of anaerobic technology as a pre-treatment before
conventional oxygen treatment.
The combination of biological aerobic and
anaerobic processes was also used in sewage
treatment plants in Tymbark fruit processing in
Poland. The technological line consisted of the
following stages: sewage pre-treatment on the
grate, grate and sieve to retain solids, biological
aerobic and anaerobic treatment and separation
of suspensions in the process of otation under
pressure The use of aerobic and anaerobic reac-
tors involves many benets, such as a positive
energy balance, reduced sludge production and
space-saving. An additional advantage is a pos-
sibility of using biogas which is generated during
anaerobic processes, as fuel in the factory boiler
room which is extremely benecial in terms of
sewage exploitation costs (http://www.veoliawa-
tertechnologies.pl).
The assessment of the eectiveness of COD,
turbidity and colour removal was also carried out
during the integration of the electrocoagulation
process using aluminium anodes and the sand
Table 9. The advantages and disadvantages of the biological treatment under anaerobic conditions in the wastewa-
ter treatment technology (according to Park et al. 2001)
Advantages Disadvantages
− possibility of energy recovery
− high reduction of BOD and COD
− low sludge production compared to oxygen methods
− high operating and maintenance costs
− considerable sensitivity of methanogenic bacteria to
changes in environmental conditions
− need for expansion tanks
301
Journal of Ecological Engineering
ltration process as pre-treatment of sewage from
the chocolate manufacturing plant in Mexico. In
the integrated process, the decrease of turbidity
by 96% has appeared. Whereas the disposal of
colour and COD reached 98% and 39%, respec-
tively (García-Morales et al. 2018).
The main weakness of typical sewage treat-
ment plants is their large area, high investment and
exploitation costs. A good solution, in this case,
can be the use of a membrane biological reactor
(MBR). It combines the classical technique of ac-
tivated sludge and pressure membrane methods.
The membrane is an absolute barrier to suspended
matter and microorganisms. Its advantage, com-
pared with traditional methods of sewage treat-
ment, is the total separation of solids by ultra-l-
tration, the possibility of reuse of treated sewage,
high concentration of activated sludge and low op-
erating costs (Cicek 2003; Fazal et al. 2015; Judd
2006; Lin et al. 2012; Marrot et al. 2004).
The eectiveness of wastewater treatment us-
ing the MBR systems was tested in the case of sew-
age from the eld crop processing, seafood, the
dairy and the winery industry. In treated sewage,
in high removal of basic pollution can be observed
(COD usually >90%). Phuong et al. (2018) tested
the eectiveness of wastewater treatment from a
cake shop using a Submerged Membrane Bioreac-
tor with a hollow bre membrane. The experiment
conrmed that the integrated MBR system removes
organic compounds from sewage successfully.
Therefore, there are many dierent methods
of wastewater treatment from the food industry,
which can be selected in an optimal way for a
given object. It is very important to be guided not
only by economic criteria but also by environ-
mental ones.
CONCLUSIONS
The sewage coming from the confectionery
industry is characterized by daily and seasonal
variability of composition and quantity which ad-
versely inuences the process of their neutraliza-
tion. The wastewater features are high values of
oxygen indicators – BOD and COD. Methods of
the sewage treatment use various processes, both
mechanical and physicochemical as well as bio-
logical ones. Each of them has its pros and cons.
Mechanical methods are used as a pre-
liminary stage of wastewater treatment. They
contribute to reducing organic compounds by
several percents. The adsorption process on the
natural sorbents causes a high decrease of BOD
and COD but the disadvantage of this technique
is the problem of waste disposal. Coagulation
and occulation are not good methods for the
discussed wastewater, because it only partly re-
duces BOD as well as COD and its main dis-
advantage is the production of a huge amount
of waste. Electrocoagulation contributes to a
signicant reduction of oxygen indicators and it
does not require chemical additives. However,
membrane techniques using multi-stage sys-
tems, although they are characterized by a high
reduction of BOD and COD, have some disad-
vantages. It is high exploitation costs and the for-
mation of leachates with a large waste concen-
tration. Both aerobic and anaerobic processes of
activated sludge cause a decrease in the content
of organic compounds in sewage. However, une-
ven sewage inow can lead to degradation of the
activated sludge. These techniques are therefore
often unprotable for the confectionery industry.
The main drawback of classic wastewater
treatment plants is their large area, high invest-
ment and operating costs. That is why MBR
Membrane Biological Reactor has become very
popular. It combines the classical technology of
activated sludge with ltration on microltration
membranes.
Acknowledgments
The work was nanced as part of the statutory
tasks of the AGH University of Science and Tech-
nology in Krakow - 11.11.140.017.
Magdalena Zajda has been partly sup-
ported by the EU Project POWR (Progra-
mu Operacyjnego Wiedza Edukacja Rozwój)
- 03.02.00-00-I038/16-00
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