The New Methods for Purifying the Industrial Effluents by Submerged Biofilm Reactors

doi:10.4236/jep.2011.27114

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Journal of Environmental Protection, 2011, 2, 996-1001

doi:10.4236/jep.2011.27114 Published Online September2011 (http://www.SciRP.org/journal/jep)

The New Methods for Purifying the Industrial

Effluents by Submerged Biofilm Reactors

Seyed Alireza Mousavi Shirazi

Department of Physics, South Tehran Branch, Islamic Azad University, Tehran, Iran.

Email: [email protected]

Received June 12th, 2011; revised July 18th, 2011; accepted August 27th, 2011.

ABSTRACT

Life on the earth is dependent on dynamic interactions between its physical, chemical and biological components. In

fact, all the individual processes are responsible for regulating the environmental equilibrium which can provide bio-

sphere for multiple forms o f human life. In order to overcome on shortcomings, the use of immob ilized cell bioreactor

technology which provides a valuable effective for treatment of waste water is discussed. An immobilized system which

in this matter is applied is about absorbed or captured microorganisms in a solid substratum to retain them in a reactor

or analytical system. The multiply of these immobilized cells is done when by nutrients be supplied and then migrate to

the surfaces which are referred to biofilms. The biofilms can be developed on various support systems such as polypro-

pylene pall, rocks, sands, charcoal, ceramics, and glass beads. The controllable reaction vessels which are used for

these colonized surfaces are referred to bioreactors. Bioreactors in both up flows and down flows mode which use of

either batch or continuous processes principle can be operated. Synchronic with development in biotechnology, there is

also an extensive development in the field of bioreactors like: pumped tower loop reactor (PTLR), liquid impelled loop

reactor (LILR), multipurpose tower bioreactor (MTB), fluidized-bed and packed-bed bioreactor, that in this a rticle are

discussed them.

Keywords: Biofilm, Bioreactor, Effluent, Environment, Liquid, Waste Water

1. Introduction

These facts that increasing the human population and

excessive agricultural activities and modern industriali-

zation can damage environment and biosphere, as an

important and serious problem are enumerated. The

deleterious effects of human activities on the biosphere

are collectively known as pollution. The pollution pre-

vention and its controlling have been caused a major

problem in present century. Waste waters management

and environment protection is commensurate with social

and economical relations and public health of society.

The waste water of various industries is including the

complex mixtures of solid materials and dissolved parti-

cles which have either high biological oxygen demand

(BOD) or chemical oxygen demand (COD) values and it

indicates their toxic effects on the plankton. Heretofore

abundant researches that deal on activities for elimination,

conversion the toxic pollution on industrial waste waters

have been reported. There is a similar problem which is

related to sewages produced due nutrients and beverage

industries [1].

The influence of the ratio carbon-nitrogen and phos-

phorus concentration on the performance of a biofilm

fluidized bed reactor has already bee used for denitrifica-

tion [2]. The thickness and the density of the biofilms

were related mainly with the shear stress in the reactor

and the composition of biofilms was dependent on the

composition of the medium and related with higher ac-

tivities of the microorganisms. Th e surface concentration

depended on the surface characteristics of the biofilms.

The biofilm is a dynamical structure, in which formation

of cracks and fissures is taking place continuously [3].

There are two process configurations based on the

BAS reactors, for nitrogen removal from wastewater by

integration of nitrification in biofilms and denitrification

in suspension. The first setup consists of a conventional

nitrifying BAS reactor coupled with a suspended biomass

reactor. The second process configuration is a single

BAS reactor which is sequentially aerated and non-aer-

ated, by cyclically recirculation the off gas [4].

A wake model is used to predict the liquid holdup,

while the solids holdup is obtained by iteration based on

The New Methods for Purifying the Industrial Effluents by Submerged Biofilm Reactors997

material balance [5].

The numerous numbers of both biodegradable organic

particles and dissolved substances in the waste waters

have high BOD value which must be reduced before

disposal of them into sewerage [6]. BOD is the amount

of dissolved oxygen which is consumed by a diluted

waste water sample and is kept for a specified time (5

days) at 20˚C. The COD is an indicator of the overall

parameter which by a hot and acidic solution of K2Cr2O7

can be chemically oxidized [7].

2. Materials and Methods

In primary stage of waste water treatment usually the sol id

sediments such as grits, soils, the suspended large particles

through grid and firm oil by suction are rem oved.

The secondary treatment is based on biological oxida-

tion that its aim is reduction of effluent’s BOD by using

the activated sludge, trickling filters, lagoons and anaero-

bic digesters individual l y or i n combinational form at s.

These treatment methods are slow and occupy a large

space and generate a large amount of sludge that is

caused disposal problems. In biological activity on waste

water treatment, free and suspended microorganisms

such as activated sludge and fixed biofilm such as trick-

ling filter are used [8]. The problem of activated slud ge is

production of a large amount of sludge and thereby bar-

ring the trickling filter. These shortcomings by using the

bioreactors are eliminated in which the immobilized cells

for treatment have been used.

An immobilized system is a system in which the mi-

croorganisms in a solid substratum either are superficial-

ity absorbed or captured for maintenance in bioreactor. It

is shown in the Figure 1.

These immobilized cells when be fed by nutrient ma-

terials then are multiplied and steadied on the surfaces

which are entitled biofilm. Biofilms by various mainte-

nance systems such as polypropylene pall rings, rocks,

sand, charcoal, ceramics and glass beads can be devel-

oped [7]. The biofilm rectors have reaction ability. The

bioreactors can be applied either up flow or down flow

mode which use either batch principle or continuous

process that these are shown in Figures 2-5 [9].

The volumes of bioreactors for various usages are as

Table 1 [9].

Gel Entrapment Adsorption

 Biocatalyst

Figure 1. Approaches of immobilized biocatalysts.

Table 1. The volumes of used bioreactors in biotechnological processes.

Product groups Bioreactor volume (m3)

Beer, wine

Cheese, bread, sauerkraut

Organic acids (citric acid, acetic acid)

Vitamins (Vit C, Vit E, VitB2)

Enzymes (amylase, lactase, protease)

Antibiotics (penicillin)

Pharmaceuticals (insulin, interferon)

Biomass (bakers/brewers yeast)

Single cell protein

Cheese industry

Milk processing

Wine distillery

Enzyme production

Jam manufacture

Cane molasses distillery

Yeast production

1000

200

100

10 - 50

200

1500 (continuous)

110

4150

5600

2000

430

1700

1280

The New Methods for Purifying the Industrial Effluents by Submerged Biofilm Reactors

998

Figure 2. Batch reactor (Type 1 of bioreactor).

Figure 3. Continuous reactor (Type 2 of bioreactor).

Figure 4. Up-flow reactor (Type 3 of bioreactor).

Figure 5. Down-flow reactor (Type 4 of bioreactor).

Figure 6. Pumped tower loop reactor (PTLR).

The PTLR reactor for batch production of Xanthan has

specially been developed and it eliminates the posed

problems in treatment by high viscosity and plastically

behavior of polysaccharide.

These achievements by helping a specially designed-

pump are afforded that this pump for keeping the liquid

in kinetic movement and shorter time of fermentation

and more concentration is applied. The LILR bioreactor

for some instances among applications for biocatalyst in

organic solvents is developed. This bioreactor consists of

two parallel tubes connected at the top and bottom.

The bioreactors which have newly been developed are

illustrated as Figures 6-12 [9].

In the LILR bioreactor the organic solvent which has

low density into a continuous non organic fluid with high

density from bottom is distributed and through difference

between densities, the fluid with continuous phase is cir-

culated. The MTB bioreactor uses of the air lift principle

and for cells of sensitive to shear can be used. Both mi-

crobe flocculating and microorganisms culturing in three

different modes can be performed: 1) bubble column. 2)

Bioreactor with inner loop that this loop has relevancy to

airlift which by riser pipe its activity is performed. 3)

Bioreactor with inner loop dependent on airlift which by

down comer pipe its activity is performed [8]. The ad-

vantage of the MTB bioreactor is that in this bioreactor

the modular design is causer for preparation of a system

based on biological processes requirements. The fluid-

ized bed and packed bed reactors which are as samples of

bioreactors, for decrement of related processes fees and

prevention of biocatalysts have been developed. In the

fluidized bed reactors, the immobilized catalyst floated in

water exists freely around airlift source while in the

packed bed reactors the catalyst along with oxygen is

almost saturated.

These bioreactors including biofilm reactors have ei-

ther round or flat drum.

The New Methods for Purifying the Industrial Effluents by Submerged Biofilm Reactors 999

Figure 7. Liquid impelled loop reactor (LILR).

Figure 8. As a bubble column.

Figure 9. Airlift loop reactor with draft tube as riser.

Figure 10. Airlift loop reactor with draft tube as down

comer.

Figure 11. Fluidized bed reactor.

The New Methods for Purifying the Industrial Effluents by Submerged Biofilm Reactors

1000

Figure 12. Packed bed reactor.

Dairy industries usually generate a large amount of

waste water. According to Internationa l Dairy Federation

for generation of milk and Milk Products, 10.7 million

ton cheese has been used and 88.34 million ton whey is

annually generated [10].

Anyway in forthcoming view, pouring the waste water

of dairy industries like whey and cheese industries to

either rivers or seas is one of the most important prob-

lems from the environmental pollution aspects. This

problem concerns and must accurately be considered

because these waste waters have high BOD with 32,000

ppm - 60,000 ppm that these amounts depend on proc-

esses of manufactory of waste water’s producer. One of

the usage instances of produced waste water in cheese

industry is pro duct i o n o f or ganic gases [11].

3. Disscusion

There are several applications of this technology in

treatment processes of industrial waste waters according

to Table 2 [1].

The wastewaters due various industries are including a

mixture of solids complex and solved particles with high

BOD (according to table2). The BOD before disposal in

common sewerage may reduce. The various chemical

and physical processes like steam stripping, ion ex-

changing and solvent extraction for separation toxic par-

ticles of waste waters can be used. The environmental

refinement of waste water might able to use live micro-

organisms in a free state to either suspended biofilm or

fixed forms. In this state a lot of produced sewerage or

wastewaters by using the immobilized cell bioreactor

technology under aerobic or anaerobic conditions can be

refined [12,13]. There is an economical and feasible de-

vised method to treat cheese whey. This method is for-

mulated of 1% glucose, 1% extracted yeast in laboratory.

4. Conclusions

At all two main aims are deduced: 1) preparing a method

for practical and economic applications of submerged

biofilm reactor in refinement of industrial wastewaters. 2)

Developing a batch of processes relating immobilized

submerged biofilm reactors for treatment of wastewaters

due dairy industries. Cheese whey is compounded of

lactose, nitrogenous compounds, vitamins and minerals

which by microorganisms to growth can be used. The

microorganisms which don’t use of lactose can be

growth through consuming other components of cheese

whey. There is a major problem for usage of cheese

whey to growth the yeast and this problem is that some

of the yeasts are relatively able to ferment the lactose.

There are several methods such as hydrolyze of cheese

whey, yeast adaptation and pressure selection which are

attempted to overcome on this problem [7,14]. A sub-

merged fixed biofilm reactor by using the culture in

Table 2. Strong effluents from food and beve rage industr ie s.

Type of waste Main pollutants

Abattoir

Beet sugar

Cannery (meat)

Distillery

Domestic sewage

Dairy

Grain washing

Fermentation industry

Starch reduction of flour

Suspended solids, protein

Suspended solids, fat, protein

Suspended solids, carbohydrates, protein

Suspended solids, oil-grease

Carbohydrates, protein

Carbohydrates, fat, protein

Suspended solids, carbohydrates

Suspended solids, carbohydrates, protein

The New Methods for Purifying the Industrial Effluents by Submerged Biofilm Reactors 1001

laboratory can be applied to treat cheese whey and all

dairy effluents for reducing BOD. At all one of the fast-

est environment to growth the microorganisms are both

slimy and effluent where the various types of extracted

wastewaters exist.

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