Anaerobic waste water treatment Plant, for dairy factory.
With this report design, we'll make an effort to outline the water treatment processes used in the food business, specifically the milk processing plant. The treatment of discharged water can be done in two ways, with aerobic and anaerobic methods. The aerobic method requires larger investments but manages to make the best conversion of matter, which means that the COD (chemical oxygen demand) from 100 kg decreases to 2-10 kg after treatment. The anaerobic method is economically more attractive considering that from this method we can extract usable energy, and the area required for the application of this method is significantly smaller, the COD value from 100 kg decreases to 10-20 kg COD after treatment. It is recommended that the aerobic method be applied as a second stage, to the anaerobic methods, with which the applicable standards for industrial discharged waters are reached.
By the anaerobic method of wastewater treatment, we mean the treatment of waste which is biodegradable with microorganisms without the presence of oxygen. This type of process also occurs in nature, on the subsurface, such as lakes and under the sediment of the oceans, a process known as "anaerobic activity", during this activity methane and carbon dioxide are released.
Anaerobic methods of wastewater treatment can be applied in industry and in households, in which case usable energy can be produced. This type of carbohydrate released during this process can be used as fuel or can be treated to obtain natural biogas. The waste that is created during the treatment of discharged water can also be used as a fertilizer in agriculture. One of the main reasons that developed countries have raised interest in the treatment of discharged water with anaerobic methods, is the release of a large amount of usable energy which is released during this process. This way of treating discharged water has been applied since 30 years ago, in Western Europe. It is worth noting that the surface for the treatment of discharged water with the anaerobic method is much smaller than the surface needed for the treatment with the aerobic method.
Feasibility report for anaerobic waste treatment in Dairy plant
Design, engineering, construction
and startup of treatment plant for processing of waste water from dairy
production.
The anaerobic digester, biogas
conditioning, pipes, pumps, instruments, cabling, and control cabinet are the
essential components.
The viability of an anaerobic
wastewater treatment system for a dairy business is presented in the document.
This file contains:
1. 1. Basic
information on anaerobic technology
2. 2. The
dairy industry's waste water technology comparison
3. 3. Determining the feasibility
A. Anaerobic
waste water treatment
a.1 Anaerobic waste water
treatment principles: context
In the absence of oxygen,
microbes break down biodegradable material through a variety of processes known
as anaerobic digestion. The procedure is used to treat trash, waste water, and
to generate energy for industrial or home applications. Food and beverage
production accounts for a large portion of industrial use.
Anaerobic activity is the term
used to describe the natural occurrence of anaerobic digestion in some soils,
lake sediments, and oceanic basin sediments. This is source of marsh gas
methane as discovered by Volta in 1776.
The procedure for treating
biodegradable garbage and sewage sludge includes anaerobic digestion. In
addition, anaerobic digesters can be fed with organic waste from the food and
agricultural industries or with crops developed specifically for energy
production.
Moreover, anaerobic digestion is
frequently exploited as a renewable energy source. Methane and carbon dioxide
are the major components of the biogas produced by the process. This biogas can
be converted to natural gas or utilized as fuel directly in gas engines for
combined heat and power. The solid digestate residues, which are nutrient-rich,
can be used as fertilizer.
Anaerobic digestion has gained
more attention from governments in a number of nations throughout the world in
recent years due to the re-use of waste as a resource and innovative technology
approaches that have reduced capital expenditures. In the past 20 years,
numerous plants have been constructed for the treatment of sewage sludge and
industrial waste fluids. Anaerobic treatment of municipal waste water is also
practiced in nations with warm climates. An intriguing feature of anaerobic
waste water treatment is that its footprint is significantly less than that of
comparable aerobic plants.
a.2 The Anaerobic process
Many microorganisms, such as
methane-producing archaea and bacteria that produce acetic acid (acetogens),
have an impact on anaerobic digestion (methanogens). These organisms support a
variety of chemical reactions and transform biomass into biogas. Aerogenesis,
methanogenesis, acidogenesis, and hydrolysis are the four main phases of
anaerobic digestion. Chemical reactions can be used to explain the overall
process, which involves anaerobic microbes biochemically digesting organic
material like glucose to produce carbon dioxide and methane.
C₆H₁₂O₆ 3CO₂ + 3 CH₄
Anaerobic treatment process of
discharged waters is
1. Hydrolysis
2. Acidification
3. Acidogenesis
4. Methanogenesis
1. Hydrolysis
Biomass occurs in large organic
polymer particles that are dissolved, which must be converted into simple
monomers. This enables the reaction of bacteria with these organic matter,
their chain structure must be destroyed into smaller parts. These monomers,
like sugar, are completely permeable to bacteria. So this process of destroying
the chain structure of polymers, transforming them into smaller molecules in
solution is called Hydrolysis
2. Acidification
Acidogenesis is the second of the four
stages of anaerobic digestion: it represents the continuous process of breaking
down the components by acidogenic bacteria. This is a biological reaction where
simple monomers are converted to volatile fatty acids, along with ammonium,
carbon dioxide and hydrogen sulphatic.
3. Acetogenesis
Acetogenesis represents the third
phase of treatment through the anaerobic method by converting it into
acetogens, this represents a phase where simple molecules are created through
the process of acetogenesis which continue to degrade by converting into acetic
acid, carbon dioxide, and hydrogen.
4. Methanogenesis
The final phase of the anaerobic
wastewater treatment process is Methanogenesis. Here, methanogens use the intermediate
products to convert them into methane, carbon dioxide and water. So it
represents a biological process where acetates are converted into methane and
carbon dioxide, while hydrogen is consumed.
B. Configuration of the Reactor for
the treatment of discharged water using the anaerobic method
Nowadays, different types of reactors
are configured in Europe. But those that are implemented the most are of the
most complete mixing type, other types of reactors are with anaerobic filters
and those with the creation of the top layer of sludge known as cover (UASB).
The types will be explained one by one below.
b.1 Thoroughly mixed reactors
Full-mix reactors actually represent a tank in which discharged water is heated and mixed with an active mass of microorganisms. The amount of fluids entering this reactor is the same as the output, thus maintaining the same level of fluids in the reactor. Microorganisms that form methane and come out of the tank from the digester with the spilled fluids. To achieve an optimal amount of biogas, the flowing fluids should be kept for 20-30 days. Liquid retention can be reduced below 4-6 days when some of the microorganisms return to the digester. In fully mixed systems, solid solids settle in a sieve while the necessary microorganisms are returned to the digester.
b.2. Anaerobic Filter
The anaerobic filter represents a
fixed biological layer which is used for the treatment of discharged water, it
creates a surface connection where anaerobic microorganisms are found in the
form of a biofilm. The treatment is carried out in such a way that the liquids
for treatment flow upwards through this fixed layer, so that the pollutants to
be treated are absorbed in the biofilm. Anaerobic filters are anaerobic systems
that eliminate the need for solids separation and recycling, creating a large
amount of sludge and low level of wastewater for treatment. The limitation of
anaerobic filters are mainly physical ones related to the deterioration of
their surface structure due to the gradual accumulation of non-biodegradable
solids. This eventually leads to channelization and short-circuiting of the
flow, and therefore anaerobic filters are unsuitable for wastewater with high
solids content.
b.3. Anaerobic Upstream Flow Sludge (UASB)
In these reactors, the microbes are continuously suspended
(separated) by the flow of liquid which flows from the bottom to the top
(uphill). The flow is determined in such a way as to allow the small particles
to flow upstream, while preventing the removal of large particles by keeping
them in the digester. Microorganisms create the biofilm around the sludge, and
methane-creating substances (microbial granules) remain in the digester. The
effluent is sometimes returned to the digester being recycled, while
maintaining a constant flow from bottom to top (uphill). In these cases of
digesters the retention time can be from one hour to one day, while the
retention of large solid materials is up to 90 days. In this way, this system
is able to separate the solid matter and increase the retention time through the
cover created by the sludge.
C. Waste water
engineers' research
Five dairy enterprises were
visited in September 2015 to assess the situation with regard to waste and
waste water, as well as to carry out sampling and analysis of the pertinent
waste streams. The quantity of whey generated is crucial to the viability of a
waste water treatment plant with biogas generation due to the high level of
biodegradable elements and, consequently, the great potential for energy
production.
A case has been developed to
evaluate the viability of biogas plants at the dairy sector based on the
findings of the study and analyses. The economics of the investments, taking
into consideration the costs and advantages, in particular the value of energy
and the profits that arise, are the main emphasis of the feasibility study.
D. Comparison of
treatment technologies for the dairy industry
It is possible to use biological,
chemical, or physical methods to treat the wastewater from a dairy industry.
The advantage of physical and
chemical processes is that they frequently take up little space and can be
found inside of closed structures. Nevertheless, these procedures have
drawbacks in that they utilize a lot of chemicals and generate a lot of sludge,
which must then be disposed of. Running expenses for these procedures are
comparatively expensive due to chemical prices and sludge disposal costs.
The harmful elements in garbage
and waste water will undergo natural biodegradation during biological
processes. As has been shown throughout the world, a biological process can be
the best and most economical method of treating dairy waste water if the right
system is selected and built appropriately.
Anaerobic and aerobic biological
systems can be distinguished from one another. In aerobic systems, the oxygen
in the water must be supplied with energy in order for the organic contaminants
to decompose through biodegradation. Without oxygen, anaerobic bacteria will
biodegrade organic contaminants in anaerobic systems, producing biogas in the
process.
Aerobic System
Feasible for waste
water
Low
temperatures 10-20 0C
Low COD strength
Treatment
efficiency
More than 95 %
Possible to
meet standards for discharge at surface water
By product A
lot of sludge
Anaerobic System
Feasible for waste water with:
Medium/ high strength/ COD
Treatment efficiency: Around 85%
To meet standards for discharge
at surface water additional aerobic treatment is needed Biogas
highly desired
Operating expenses
High (Aeration- costs)
Small amount of energy used, small
costs for sludge removal.
d.1. Anaerobic and
aerobic systems are compared in terms of cost
Whey, which is highly
concentrated have a temperature of 30 0C, in case is added lot of cleaning
and rinsing water, create less concentration and has a lower temperature. To
meet the requirements for discharge at surface waters, there are two methods
for biological waste water treatment.
1.) Aerobic
treatment of the waste water
2.) Anaerobic
treatment of the waste water with an additional aerobic treatment of the
anaerobically treated waste water.
Investment
expenses for the two strategies are equivalent. The operating costs,
particularly the energy expenditures, are the most significant difference.
Basis
assumption:
Ø COD
load waste water is 1440 COD / day
Ø 300
production days per year
Ø Hydraulic
load about max 50 m3 day estimation
Ø 80
% of the biogas produced can be used effectively as an energy source in the
factory or in another way
The contamination in the wastewater is
comparable to that of a small town with 15.600 residents.
Aerobic Treatment Anaerobic
treatment waste water an aerobic post treatment
Net
production of CH₄ gas;349 Nm3/day
CH₄
gas used effectively 279 Nm3/ day
Costs aeration energy which corresponds
with 299 l diesel/day
25.920 euro/ year Profit
83.520 euro/ year
Sludge production 151.200 kg Cost energy for aeration in
post treatment system 3.900 €/day
Dry solids / year or 5.040 m3year Sludge production 21.600 +
22.800= 44.400 kg dry solids/ year
or
432 + 760= m1.192 m3 / year
Due to energy expenses associated
with aeration, full aerobic treatment of wastewater results in a yearly cost of
32.000 euros, whereas anaerobic treatment followed by aerobic post-treatment
results in a profit of 82.500–3.900=78.620 euros.
Calculation:
d.1.1 Aerobic treatment
Oxygen demand is 1440 (COD load)
x 0.60 (COD in sludge 35%) and rest COD (5%)= 864 kg O₂/ day.
Specific energy demand of
aeration is about 0.8 kWh/ kg O₂.
Total energy demand aeration is
691 kWh / day. Costs are 691 x 0.12= 83 euro/ day.
Total costs are 300 x 83= 25,920
euro/ year.
Sludge production: 0.35 x 1440=
504 kg dry solids/ day or 504 x 300 =151,200 kg/ year is 5,040 m3sludge/year
(sludge 3% dry solids).
d.1.2. Anaerobic treatment and Aerobic post treatment
Biogas production from anaerobic
treatment: 1,440 x 0,8 (85% COD efficiency + 5 % COD in waste sludge) x 0,35
(specific gas production 0.35 Nm3/ kg COD removed) is 403 Nm3
gas CH₄/
day.
To keep reactor content at 30 0C
to 35 0C, methane gas has to be used for heating of the waste water.
It is assumed that the wastewater has to be raised 10 degrees in temperature.
Energy need is 10 x 50 x 4,2 (energy raise 1 m3 1 0C is
4.2 MJ)= 2100 MJ per day which corresponds with 2100/ 38,6= 54 m3
methane gas. Net gas production is 403- 54= 349 m3/day
Gas used effectively 0.8 x 349=
279 Nm3/ day.
1 Nm3 CH₄
gas corresponds with 1.07 l diesel, 279 Nm3 gas corresponds with 299
l diesel. Costs diesel are 1.1 euro /l
Yearly profit is (production 300
days a year) 300 x 299 x 1.1 = 98,670-euro year
Production sludge 0.05 x 1440 =
72 kg dry solids / day or
300 x 72 = 21,600 kg dry solids/ year is 432 m3 sludge (sludge 5% dry solids)
d.1.4. Aerobic
treatment
COD load of
aerobic post treatment is 0.15x 1.440= 216 kg COD / day.
Oxygen demand
is 216 (COD load)x 0.60 (COD in sludge 35% and rest COD 5= 130 kg O₂/
day.
Specific energy
demand aeration is about 0.8 kW/ kg O₂.
Total energy
demand aeration is 0.8 x 130= 104 kW/ day Costs are 104 x 0.12= 14 euro day
Total costs 300 x 14 = 3900 euro / year
Production
sludge 0.35 x 216= 76 kg dry solids / day or 300 76 = 22,800 kg dry solids/
year is 760 m3 sludge (sludge 3% dry solids).
Information
on waste water
The following
input data and fundamental assumptions were used to calculate the anaerobic
waste water treatment system's viability.
ü
There are two main waste products from the
cheese-making process: concentrated whey waste and waste water, which includes
cleaning fluids.
ü
Milk processed 24 m3/ day during 12
hours per day and 6 days per week (with extension 30 m3).
ü
Production of whey: 20 m3/ day, COD
whey is approximately 68.000 mg/ l and sulfate SO₄ concentration 1100 mg/ l
ü
Production of waste water: 51 m3/
day, COD waste water approximately 4000 mg/ l and sulfate SO₄
concentration 500 mg/ l.
ü
Waste water and whey are both treated by the
system.
ü
To keep the reactor content at 30- 35 C, methane
gas has to be used for the heating of the waste water. I am assumed that, in
average, the temperature of the waste water is 20- 25 C and has to raise by 10
degrees in temperature.
ü
Biogas will be recovered and will be used for
heating purposes and will so substitute the use of diesel oil. Biogas can be
used for heating of the waste water and for production of the hot water.
F. Basic
design information
Building
Local
earthquake regulations will be followed during the construction of the plant.
Concrete will be used to build the foundations, hydrolysis ring, and digester
tanks. Pumps, a control unit, flares for biogas, and other control equipment
will all be supported by concrete.
Design
guidelines
1. Two
stage treatment process: mixing/ hydrolysis (MHT), anaerobic digestion (AD).
2. WWT
plant design is based on existing processing capacity.
3. Plant
is capable to handle all effluents from dairy factory.
4. Input
material waste water free of stones and other obstructive material.
5. Input
material is provided mainly during daytime (16 hours per day).
6. Mixing
of the collection tank is not provided. Volume 20 m3 with feed
pumps.
7. The
temperature of the anaerobic digester sludge is set to 30 0C
(mesophilic temperature range). No heating of the digester will occur, but
heating of the waste water in the mixing tank is possible.
8. Anaerobic
digester volume 150 m3, provided with sludge/ biogas/ effluent
separator and gas roof.
9. The
bacteria within the fermenter transforms the organic material into biogas.
10. The
biogas is stored underneath the flexible roof which consist of a membrane.
11. Desulphurization
device is provided on basis oxygenation of hydrogen sulphonyl in biogas.
12. Conditioning
of biogas by automatic Colling device.
G. Construction of
the waste water treatment
The proposed technology is based on aerobic biological
treatment process, which consists of:
Step 1: reception – conditioning tank (MHT)
Step 2: anaerobic digestion tank (AD)
Step 3: biogas conditioning system (BC)
The output from the waste water treatment system will be:
a)
Biogas with high calorific value
b)
Treated effluents
c)
Biological sludge
G. 1. Services and apparatus
1.
Design and Engineering
2.
Collection and hydrolysis in to the mixing tank.
3.
Anaerobic
digester, including piping, instruments and controls
4.
Biogas conditioning unit
5.
Civil work design and support structures.
6.
Construction management, project coordination.
7.
Biological process monitoring
8.
Manual and documentation.
9.
License and permits.
Conclusion
The use or treatment of the whey that is released during cheese processing is one of the biggest concerns nowadays. Considering that it contains large amounts of organic matter, and considering the large amount released during cheese production, this represents a serious problem for the environment. However, the potential production of biogas (methane), hydrogen or other marketable products, with simultaneous high COD reduction through proper treatment proves that the whey which is released during cheese production should be considered as a source of energy and non-polluting. The presence of biodegradable components in whey, together with the advantages of anaerobic processes, makes the anaerobic treatment method more attractive for whey treatment. This project aims to examine the most representative applications that are currently being carried out in whey, which processes are being perfected based on the scientific studies that are being developed.
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