Study on Optimum Utilization of Sludge from Sewage
Treatment Plants
K.Prasanna⃰, KS.Anandh⃰ and Lakshminarayanan.B#
* Assistant Professor, Department of Civil Engineering, SRM University
# UG Scholar, Department of Civil Engineering, Valliammai Engineering College.
lprasanna.env@gmail.com
2lakshminarayanan303@gmail.com
Abstract— The rapid growth in today’s construction industry has obliged the civil engineers in searching for more
efficient and durable alternatives far beyond the limitations of the conventional brick production. Many attempts have been made to
incorporate wastes into the production of bricks. The sewage treatment plant (STP) sludge is extremely close to the brick clay in
chemical composition. In this study we experimentally describe the recycling of the waste products like STP sludge by incorporating
them into bricks. It is a practical solution for problems like cost expenditure on waste management and its effect on environment.
Among all disposal options, the use of STP sludge in producing constructional element that is brick is considered to be the most
economic and environmentally sound option. The overall objective is to incorporate the large volume of STP sludge produced in the
wastewater treatment plant in SRM University. Various tests were carried out whose results stated that sludge proportion and firing
temperature were the two key factors determining the quality of brick. Increasing the firing temperature and decreasing the amount
of sludge in the brick resulted in a decrease of water absorption. The appropriate percentage of sludge content for producing quality
bricks was in the range of 10 to 30% by weight with a 13 to 15% optimum moisture content prepared in the moulded mixture and
firing at 1000ᵒC for 6 hrs. With 10% sludge content, the sludge-clay bricks exhibited higher compressive strength than normal clay
bricks. This study showed that the pulverised sludge could be used as brick material. The bonding strength can be further enhanced
by controlling the operating conditions. Finally the study concluded that the sludge can be used in as an additive to sludge-clay bricks
as one of the available disposal options for SRM University sewage treatment plant.
Keywords— Sewage Treatment Plant, Sludge, Waste management, Characteristics of sewage, Brick production.
I. INTRODUCTION
The amount of generated wastewater sludge has been rapidly increased due to development of urbanization and
industrialization. Today, most of sludge is disposed by land filling and spreading on agriculture land. The large volume of
waste water sludge generated, increasing of environment concerns and the scarcity of landfill site made land filling and
agriculturally uses of sludge are limited. So, new alternative applications have to be considered for the disposal of waste water
sludge diverted away from the landfills and agriculture. One of the these alternatives is the use of wastewater sludge in
construction materials field. The possible use sludge as construction and building materials would provide a new option of
alleviating the sludge in significant quantity. Also this option has an economic and energy saving advantage.
In this study, we systematically investigated the incorporation of sewage sludge in manufacturing of bricks. In order to obtain
the suitable manufacturing conditions, the proportion of sludge in the brick and the firing temperature that might affect the
qualities of bricks were investigated. This chapter presents a summary of relevant studies carried out in the area conversion
wastewater sludge into construction materials.
II. USE OF SLUDGE WORLDWIDE
Sludge must be treated or stabilized to be safe for use of dispose. Worldwide, wastewater sludge is disposed be different
methods. The most common methods of disposal depend on land application, landfill or incineration. Landfills option can be
used carefully due to high costs and risk materials is sludge which may contaminate surface and ground water. Use of the
incineration method to dispose sludge reduces only sludge volume. The remaining ash would still needed to be disposed in a
land fill. The incineration process requires large capital investment and expensive safeguards against pollution.
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Large quantities of sludge are also used in agriculture field as composts. This option faced a problem which makes them
unsuitable. This problem came from the existence of toxic materials in some sludge types. Therefore, there is an increasing need
for exploring new fields of sludge disposal. One of these new fields is to use dry sludge as an additive material using sludge
clay bricks that result from incineration process.
III. STATEMENT OF THE PROBLEM
The SRM campus wastewater plants produce an increasing volume of sludge. The quantities of sewage in all SRM campus
are estimated to be 30,25,000lit/day. The large quantities of sludge and the scarcity of land area are significantly increasing the
sludge risk to public health. The growing problem of wastewater sewage sludge disposal in the SRM campus can be alleviated
if new disposal options other than landfill can be found. New emerging studies world wide spotlight on reusing sludge, sludge
and treated wastewater in construction technology. This work was directed toward establishing the use of waste water sludge to
mixture of clay bricks. The successful use of sludge will help in reducing the environmental and health problems related to bad
handling of sewage sludge at wastewater treatment plants and the scarcity of land area needed for disposal.
IV.MATERIALS AND METHODS
The details of methodology is sown in figure.1
Fig.1
A. Sludge production and collection
The resulted sludge from wastewater treatment plants has a large volume. This volume consisting of high water content.
Removal of this water from sludge will improve efficiency of subsequent treatment process, reduce storage of volume and so
decrease operation and transportation costs. After reduction of sludge of sludge water content, another treatment process is
needed to stabilize the sludge and killing pathogenic organisms. Several treatment process are carried out to reduce sludge water
content including conditioning, thickening, dewatering and stabilization.
Other treatment process aims to kill organisms by subjecting sludge to high temperatures or high PH. This process is a
sanitation process of sludge done by number of treatment such as anaerobic digestion, pasteurization, and composting and lime
stabilization. There are different treatment process can be applied on sewage sludge, depending on the disposal or recycling.
Sewage sludge production is a continuous process needs a suitable disposal method. The options for ultimate use of wastewater
sludge is called sludge disposal. These options should be economically and environmentally acceptable.
B. Casting of Bricks
Sludge and clay are blended from variable speed box feeders, equipped with rotating tines, discharging on to a conveyor. The
resulted mixture was extruded into brick samples. The bricks dried and fired in a kiln. Currently 30% by volume of sludge is
added to the clay for the production of bricks. Air drying takes place under at ambient temperature for a period of
approximately 2 weeks or drying in heated chambers where the bricks remain for 48 hours at an average temperature of
between 60 degree and 65 degree C.
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C. Mix ratio
Table – I Composition of bricks
S.No Mix ratio Sludge ( % ) Clay ( % )
1 Sample 1 0 100
2 Sample 2 10 90
3 Sample 3 20 80
4 Sample 4 30 70
5 Sample 5 40 60
6 Sample 6 50 50
The sludge clay mixture were then intruded into a series of standard brick moulds ( length 190mm, width 90mm, thickness
90mm ). The moulding process is the key to success in making the brick from 100%sludge without any additives, so it must be
carefully carried out. Also temperature should be carefully controlled to prevent black core and breaking. A clay only mixture
was used as a reference specimen. After 24 hours maturation followed by another 24 hours 105 degree C for chamber drying
period. Molded mixture were fired ina combustion chamber a the design temperature of 950 Degree C for 6 hours. The
produced bricks then received a tests, water absorption and compressive strength to determine the suitable conditions for
producing qualified bricks.
D. Testing of Bricks
1. Water absorption test
Water absorption is a key factor affecting the durability of brick. The less water infiltrates into brick, the more durability of
the brick and resistance of the natural environment are expected. Thus, the internal structure of the brick must be intensive
enough to avoid the instrusion of water. The water absorption was determined by using the procedures described in ASTM C
67-60 ( 1998 ). The value of water absorption, is directly proportional to the quantity of ash added. Increasing the firing
temperature resulted in a decrease of water absorption, thereby increasing the weathering resistance. According to the criterion
of water absorption of bricks in ASTM C67-87 ( 1998 ), the ratio is below 17% for the first class bricks and 17 to 22% for
second class brick.
2. Compressive Strength of Bricks
The compression test is the most important test for assuring the engineering quality of a building material. The results
indicate that the strength is greatly dependent on the amount of sludge in the brick and the firing temperature. The optimum
amount of sludge that could be mixed with clay to produce good bonding bricks was 20 % by weight. As shown with upto 40%
sludge added to the bricks. The strength achieved at 950 degree C can be as high as that of normal clay bricks. The compressive
strength of the bricks made from sludge clay mixtures all meet the CNS382 R2002 standards ( CNS1999b) for the bricks
requirements 150kg/cm2 for a first class bricks and 100kg/cm2for a second class brick. It is concluded that sludge ash can be
blended with clay in different proportions to produce a good quality of brick under a certain firing temperature
V. RESULT AND DISCUSSION
Table – II Characteristics of sewage on 21.08.2015 and 23.08.2015
S.No Name of the
Characteristics
21.08.2015 22.08.2015 23.08.2015
Before treated After treated Before treated After treated Before treated After treated
1 BOD 140 Mg/L 85 Mg/L 350 Mg/L 140Mg/L 125Mg/L 90Mg/L
2 COD 350 Mg/L 185 Mg/L 350 Mg/L 350 Mg/L 355Mg/L 185Mg/L
3 PH 7.5 6.5 7.5 7.5 7.5 6.5
4 TDS 1375 PPM 900 PPM 1375 PPM 1375 PPM 1400PPM 800PPm
Table – III Characteristics of sewage on 24.08.2015 and 26.08.2015
S.No Name of the
Characteristics
24.08.2015 25.08.2015 26.08.2015
Before treated After treated Before treated After treated Before treated After treated
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1 BOD 100 Mg/L 85 Mg/L 140 Mg/L 85 Mg/L 120 Mg/L 95 Mg/L
2 COD 325 Mg/L 185 Mg/L 350 Mg/L 185 Mg/L 325 Mg/L 175 Mg/L
3 PH 7.2 6.5 7.5 6.5 7.5 6.5
4 TDS 1300 PPM 850 PPM 1400 PPM 850 PPM 1400 PPM 1000 PPM
The BOD content of before treated 140Mg/L and after treated 85Mg/L. But normally the BOD content range 300 to100. So
its coming 85Mg/L. So we can use for agriculture and co
nstruction purpose. The COD content before treated 350Mg/L and after treated 185Mg/L. But normally the COD content
value according the VLAREM II basic environmental quality standards for sewage water the range should <150Mg/L. So this
sample is not with in the range, so we can use for construction and agriculture.
The PH value before treated 7.5and after treated 6.5. But normally the PH value varying from 6.5 to 8.0. so its below 7. So
we can use construction and agriculture purpose. The TDS value before treated 1375ppm and after treated 900ppm. But
normally the TDS value varying from>250Mg/L. So we can use construction and agriculture purpose.
Table – VI Characteristics of sewage on 21.08.2015 to 26.08.2015
S.No Name of the
Characteristics
21.08.2015 22.08.2015 23.08.2015 24.08.2015 25.08.2015 26.08.2015
1 Alkalinity 135 Mg/L 135 Mg/L 140 Mg/L 150 Mg/L 160 Mg/L 135 Mg/L
2 Hardness 425 Mg/L 425 Mg/L 430 Mg/L 455 Mg/L 500 Mg/L 500 Mg/L
3 Electrical Conductivity 1.3 MS 1.3MS 1.5 MS 1.3 MS 1.3MS 1.5 MS
4 Dissolved Oxygen 4 Mg/L 4 Mg/L 4 Mg/L 4 Mg/L 4 Mg/L 4 Mg/L
5 Chloride 258 Mg/L 258 Mg/L 260 Mg/L 250 Mg/L 258 Mg/L 258 Mg/L
6 Phosphates 2 Mg/L 2 Mg/L 2.2 Mg/L 2 Mg/L 2 Mg/L 2.1 Mg/L
The drinking water Alkalinity is IS 10500-1991 is 200 to 600 Mg/L. But the sewage alkalinity value is range from 135 to 160
Mg/L. So, Shell be unfit for domestic purpose. The hardness of drinking water range is 300 to 450 Mg/L. But the sewage
hardness is 425 to 500 Mg/L. So it is not fit for domestic purpose.
The sewage water can be recycled or reused as a source of water for a multitude of water demanding activities such as
agriculture, aquifer recharge, aquaculture, fire fighting, flushing of toilets, snow melting, industrial cooling, parks and golf
course watering, formation of wet lands for wild life habitats, recreational impoundments, and essentially for several other non
potable reuse of wastewater depends on the hydraulic and biochemical characteristics of wastewater. Which determine the
methods and degree of treatment required. While agriculture irrigation reuse, in general, require lower quality levels of
treatment, domestic reuse the highest treatment level.
Table – V Chemical properties of sludge
S.No Chemical tests Protocol Result
1 Calcium ( Ca ) EPA 3050 B 3.24
2 Magnesium ( Mg ) EPA 3050 B 0.82
3 PH EPA 9045 D 6.96
(10% Suspension )
4 Phosphorous ( P ) IS 10158:1982
( Reaff.2033)
1.33%
5 Sodium ( Na ) EPA 3050 B 2414mg/Kg
6 Specific gravity By Cylinder method 0.71
7 Sulphate ( SO4 ) By ICOPOES 3.46 %
8 Aluminium ( Al ) EPA 200.8 4517mg/kg
9 Total Chromium EPA 200.8 25.9mg/kg
10 Lead ( Pb ) EPA 200.8 17.8mg/kg
11 Nickel ( Ni ) EPA 200.8 25.9mg/kg
12 Manganese ( Mn ) EPA 200.8 422 mg/kg
13 Chloride ( Cl ) APHA 2IST EDN:2005 4631 mg/kg
14 Silver ( Ag ) EPA 200.8 5.2mg/kg
15 Tin ( Sn ) By ICPOES 2.3mg/kg
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VI.CONCLUSIONS
This work has demonstrated a feasible way of using sewage sludge a clay substitute to produce quality bricks. Different
measurements of both clay sludge admixtures and brick were carried out to evaluate the factors that could affect brick quality.
Major findings in this study are as follows.
1. The brick manufactured did not show any deformation or uneven surfaces occurring at firing temperature when a 13
to 15 % optimum moisture content was applied in the moulded mixtures. Increasing the firing temperature and
decrease the amount of sludge in the brick resulted in a decrease in water absorption. In might be much easier to
manufacture a brick to meet the second class brick water absorption criteria, but for a first class brick. One should
control the sludge to less than 25% and fire at greater than temperature.
2. The results of compressive strength tests on the bricks made from both clay and sludge indicate that the strength is
greatly dependent on the amount of sludge in the brick and the firing temperature. The optimum amount of sludge
that could be mixed with clay to produce good bonding of bricks was 10% by weight with upto 30% sludge added to
the bricks, the strength at temperature can be as high as that of normal clay bricks.
3. We revealed that sludge is a potential material for the brick components. The advantages gaining more compressive
strength in making an sludge clay brick would stimulate the use of sludge as a brick additive in the near future.
4. The development of the use of sludge in brick making has led to a viable commercial manufacturing process, to
their considerable mutual benefit. The paper work is evaluates the exact proportion of sludge which will not affect
the clay sludge bricks. As the objective was one dimensional, thus there may be some limitations.
VII. ACKNOWLEDGMENT
The authors would like to thank the officials and management of SRM University for their support in doing this work.
VIII. REFERENCES
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