62
World Review of Entrepreneurship, Management and Sust. Development, Vol. 7, No. 1, 2011
Characteristics and potential uses of sewage sludge
in the commercial capital of Bangladesh
M.M. Abdullah-Al-Mamun
Institute of Forestry and Environmental Sciences,
Chittagong University,
Chitagong-4331, Bangladesh
E-mail: almamun1000@gmail.com
Kazi Mohammad Masum*
Department of Forestry and Environmental Science,
Shahjalal University of Science and Technology,
Sylhet-3114, Bangladesh
E-mail: km_masum@yahoo.com
*Corresponding author
Mohammed Shafiul Alam
Institute of Forestry and Environmental Sciences,
Chittagong University,
Chitagong-4331, Bangladesh
E-mail: shaficu@yahoo.com
Abstract: Based on contrasting properties, sewage sludge can be co-recycled
in order to take simultaneously the best profit and minimise environmental
pollution. The present study was conducted to assess the physical and chemical
properties of sewage sludge generated from different sources in the commercial
capital of Bangladesh and on the basis of these characteristics a variety of ways
had been fixed to seek out its potential uses. Presence of plant nutrients and
organic matter in sufficient quantities, make sludge disposal on land an
attractive option. Nitrogen has received most attention and it is normally the
most abundant sludge nutrient. The other two prime nutrients phosphorus and
potassium content in sewage found significantly higher than the normal soil. To
inquire the possible utilisation the growth performance of one tree species was
tested in an experiment using the sewage sludge and normal soil and found
significant positive growth variation in sewage application compare to the
normal soil.
Keywords: sewage sludge; potential use; disposal; commercial capital; tree
growth; Bangladesh.
Reference
to
this
paper
should
be
made
as
follows:
Abdullah-Al-Mamun, M.M., Masum, K.M. and Alam, M.S. (2011)
‘Characteristics and potential uses of sewage sludge in the commercial capital
of Bangladesh’, World Review of Entrepreneurship, Management and
Sustainable Development, Vol. 7, No. 1, pp.62–76.
Copyright © 2011 Inderscience Enterprises Ltd.
Characteristics and potential uses of sewage sludge
63
Biographical notes: M.M. Abdullah-Al-Mamun received his MSc in
Environmental Science from Institute of Forestry and Environmental Sciences,
Chittagong University, Chitagong-4331, Bangladesh. He is a Project
Coordinator in ‘Homestead agroforestry through improved management
practices project’, USAID Project, Prottyahsi, Chittagong, Bangladesh. His
research interests include pollution control and climate change adaptation.
Kazi Mohammad Masum received his MSc in Forestry from Institute of
Forestry and Environmental Sciences, Chittagong University, Chitagong-4331,
Bangladesh. He is a Lecturer in the Department of Forestry and Environmental
Science, Shahjalal University of Science and Technology, Sylhet-3114,
Bangladesh. Previously, he was an Assistant Conservator of Forest (ACF) in
Bangabandhu Sheikh Mujib Safari Park, Chakaria, Cox’sBazar, Bangladesh.
His research interests include ecology, biodiversity conservation and wildlife
management.
Mohammed Shafiul Alam received his PhD with a thesis on ‘Pollution effect
on plant and soil system’ from Aberdeen University. He is a Professor in
Institute of Forestry and Environmental Sciences, Chittagong University,
Chitagong-4331, Bangladesh. His research interests include environmental
management and pollution control.
1
Introduction
With the industrial revolution, new factories started coming up which gave birth to
numerous new cities. Small towns started taking the shape of big cities and big cities
started becoming metropolitan cities. This gave birth to water supply and sanitary
problems (Singh and Singh 1984). It also pragmatically noted that the millions of tons of
sewage sludge (SS) generated each year must go somewhere. A relatively high
proportion, for example in UK 67%, of sludge produced in many countries is applied to
agricultural land as a means of disposal. If not applied to land, most sludge would have to
be burned in incinerators or land filled (Renner, 2000).
The N, P, K are often deficient in almost all the soils because of their heavy
depletion. The deficiency is corrected by application of fertilisers (Gupta, 2000). Sewage
sludge can be the alternative option of this fertiliser. But, Renner (2000) reported the
application of sewage sludge to land, especially on agricultural lands, has been
contentious since the late 1980s, when national and international clean water regulations
prohibiting the ocean dumping of sludge were first enacted. Berry (1986) found More N,
P, and organic matter on sludge treated plots. The substantial N and P concentration in
sludge render is a useful fertiliser material and its organic constituents give it beneficial
soil conditioning properties. The improved aeration and drainage following sludge
amendments can have indirect effects on the soil-plant relationships of heavy metals
through affecting growth, nodulation in leguminous plants and other properties
(Heckman et al., 1986; Roberts et al., 1988). Nutter et al. (1979) pointed forest floor
increased in all nutrients except N in waste water irrigation experiment and P increased in
the upper 15 cm soil layers only. In most of the developing countries like Bangladesh
application of sewage sludge is a very new concept. Though our population pressure is
very high and a good quantity of sludge is produced, but due lake of awareness,
information and facilities they are not been used in a well manner so far. In Dhaka we
64
M.M. Abdullah-Al-Mamun et al.
have only one treatment plant and there is no other. Amin et al. (1998) found in Dhaka
the sewage treatment plant at Pagla was designed to treat a maximum flow of 120000
m3/day of domestic sewage generated from about 18% population of the metropolitan
area. Anon. (2000) found that, drainage and sewerage load in Dhaka city: Annual
drainage volume: 560 million m3 (rain water: 230 million m3, waste water: 330 million
m3); Sewage load: 1,040,000 m3/day; treatment capacity: 120,000 m3/day, population
covered by sewage system: 20%; area of the city covered by sewerage system: 30%.
2
Methodology
2.1 Location and topography
Chittagong City is not only the principal city of the district of Chittagong but also the
second largest city of Bangladesh. It is situated within 22°–14’ and 22°–24’–30’’N
latitude and between 91°–46’ and 91°–53’ e longitude and on the right bank of the river
Karnafuli. Chittagong the commercial capital of Bangladesh has a land of 209.66 km2 a
population of 2.096 million bearing a density of 9,996 individuals per sq. km (Mian,
2003).
2.2 Site selection
Firstly, reconnaissance survey was conducted to find out three different areas under
Chittagong City Corporation (CCC) to collect SS of residential area (RA), commercial
area (CA), Industrial Area (IA). Normal Soil (NS) was collected from the hill of
Chittagong University Campus (CUC). Whole area of CCC was surveyed and categorised
namely Khulshi as (RA), Agrabad as (CA) and Baijid Bostami as (IA). Sewage sediments
were collected from sewerage of these three areas with three replications in each of them.
The NS was used as a control.
2.3 Sampling
SS samples were collected from each of the three different areas described above from
the last week of May to first week of June 2008. Soil samples were collected from
surface of the drain and put in poly bag after collection to bring the sample in the
laboratory. Adequate samples were used for studying physical and chemical properties
and remain samples were used to growing seedlings to evaluate the growth performance.
2.4 Sample preparation
In the laboratory, collected moist soil samples were first sieved through 10 mm mesh
sieve to remove gravel, small stones and coarse roots and ten passed through 2 mm sieve.
Then the sieved samples were dried under room temperature. Besides, some sub-samples
were dried in an oven at 105°C for eight hours. Some dry samples were used for
determining pH and oven dry samples to determine organic matter, total nitrogen,
available potassium and available calcium (Ca) and other parameters.
Characteristics and potential uses of sewage sludge
65
2.5 Analysis
Soil colour was determined with the help of Munsell soil colour chart. Texture was
determined by hand feeling. The pH of the suspension was measured with a digital pH
meter (TOA, Japan). The filtered water was then measured with a digital conductivity
meter (TOA, Japan). Before taking conductivity reading of filtered water, the meter was
standardised. Percentage of carbon and organic matter were calculated from the following
relationship % C = 0.476 X (% LOI – 1.87); % organic matter = % C X 1.72. Nitrogen
was determined by micro-kjeldhal digestion process (Jackson, 1973). Phosphorous was
measured by Olsen’s method. Zn, Ca and Mg are determined by atomic absorption
spectroscopy (AAS). B was measured by spectrophotometer (420 nm).
2.6 Growth performance for tree species
The soil was sieved well (<3mm) and lay on the cemented ground. Fruits of Samanea
saman were collected from the IFESCU and dried in the sunlight and stored in airtight
poly bags till the treatments were given. Seeds were extracted from fruits by
removing fealty covering. Randomised complete block design (RCBD) with three
replications was used. Each replication consisted of ten seeds and each treatment
consisted of thirty seeds. So, total one hundred and twenty seeds are used in four different
media. Different treatments combination using different types of growing media in the
experiment were as follows: T1: SS from RA; T2: SS from CA; T3: SS from IA and
T0: NS from IFESCU.
2.7 Assessment of Samanea saman seedlings
The germination was recorded alternate day from the date of sowing and continued up to
last germination. The seedlings were allowed to grow altogether for two months.
At the end of the experiments, three seedlings from each replication were randomly
selected and uprooted very carefully to estimate the seedling biomass. Then fresh
weight of shoots, roots and leaves are recorded. Shoots and roots were oven dried at 70oC
for 72 hours and oven dry weight was determined. From the available data daily and
cumulative germination counts, quality index, volume index, and seedling vigor were
identified.
Data were statistically analysed for studying the morphological growth variations
each treatment.
3
Results and discussion
3.1 Physical characteristics
Sewage sludge (SS) contain a wide range of environmental contaminants owing to
diverse sources of effluents discharged into sewers. Based on the sources, the
environmental contaminants of SS includes household chemicals, human excretion
products, automobile fuels, lubricants, runoff from highways containing hydrocarbons
66
M.M. Abdullah-Al-Mamun et al.
and other fuel combustion products, and effluent from many diverse industries.
Hence the physical and chemical properties of SS certainly varied depending on the
sources from where they are generated. The SS has also many useful properties
for agricultural use as it is a source of N and P and it acts as physical soil conditioner.
The present study attempts identify the nature of properties of SS of three different
sources.
3.1.1 Colour and texture
Sewage sludges (SS) vary in colour with their origin. Soil properties some times depend
on its colour. The collected samples were also with various colours. The RA gets mainly
kitchen decomposed wastes, papers and other home used products. It carries black colour
where as, SS from IA look like grayish brown. Singh and Singh (1984) described, fresh
sewage has light brown or yellowish grey colour, dark or black colour indicates its septic
or stale state. In CA the usable products are quite different such as paper, packages,
remains of food products, etc which contain mostly carbon. As so it carries black colour.
IA possessed greyish brown colour as its origin was fully different than that of RA and
CA. There are various elements such as irons, manganese, sulphur, used here. The NS
looked brown colours. Perhaps it was predominate in slightly decomposed plant
materials.
Table 1 Colour and texture of NS and SS collected from three different sources in the study area
Location
Colour
Texture
RA
Black
Loamy
CA
Black
Loamy
IA
Grayish brown
Sandy loamy
NS
Brown
Sandy loamy
Notes: RA – residential area, CA – commercial area, IA – industrial area,
NS – normal soil.
Texture of the SS of different sources and NS differed in between sandy to loamy. The
origin of the sludge and parent materials determined the texture of the soil. It influences
on density, aeration, chemical reaction and so on. The percentage of sand and clay is <52
and <20 in sandy loamy soil. On the other hand loamy soil contains <52% sand,
28%–50% silt and 7%–27% clay. Species which are light demanding and pioneer show
good growth on coarse textured soil. Tree such as teak and eucalyptus grow well in fine
textured soil, since they require more water at the seedling stage. On the other hand trees
like Babul, Casuarina, Khair, etc. con grow on coarse textured soil since they require less
water in their life. This study found loamy texture in RA and CA where as sandy loamy
in IA and NS.
3.2 Chemical characteristics
In recent years the importance of soil chemical properties has gained considerable
attention, because of increasing popularity of short rotation and intensively managed
Characteristics and potential uses of sewage sludge
67
forest, seed orchard and forest nursery in many parts of the world. Problem soil is another
subject of discussion matter as it intermingled with the agricultural production system.
The information about the soil chemistry is pre-requirement for the management and
utilisation of the soil. SS is nothing less than a mixture of decomposed materials and soil.
The macro and micro nutrients concentration and their nature help to the decision maker
on particular tract of land. This study tried to find out properties of some common
elements present in the SS and NS.
3.2.1 Electrical conductivity
The Figure 1 showed that the NS has the higher electrical conductivity (EC) than that of
the SS. The NS has the EC of 1012 µs\m. Then the Industrial sewage sludge has the
second highest EC of 489.66 µs\m. After that SS of CA contained 468.33 µs\m and RA
233 µs\m. But some report ravelled the controversial value, i.e., the sewage sludge has
higher EC than that of normal soil. The statistical analysis explained there was significant
difference in between NS and SS of different areas.
Figure 1
EC (µs/m) of normal soil and three different sewage sludge of varied sources in the
study area
1200
EC( µs/m)
1000
800
600
400
200
0
RA
CA
IA
NS
Source s
3.2.2 PH
PH is the most important characteristics of soil because it changes the dimension, speed
and nature of the chemical reaction of elements. This study found the PH of the SS and
the NS both are slightly acidic to neutral. The SS of RA, CA, and IA got the value of
6.033, 6.667 ad 6.433 respectively. The NS also contained like the same result, 6.45.
Forsberg and Ledin (2005) and Arcak et al. (2006) also supported this result respectively
6.6 and 7.90. It is the neutral range of the PH (around seven) and help in growing a wide
range of species in the sludge. There is no significant difference of PH value in between
NS and SS of IA and CA. The other SS of RA has a significant difference than that of
NS. Though the difference of PH between NS and SS of RA was significantly differ from
each other but, still they are not out side normal range.
68
M.M. Abdullah-Al-Mamun et al.
Figure 2
PH of normal soil and three different sewage sludge of varied sources in the study area
6.8
6.6
pH
6.4
6.2
6
5.8
5.6
RA
CA
IA
NS
Sour ce s
3.2.3 Organic matter
SS contains significant amount of organic matter (OM). Many report found more than
half percent of the sewage sludge is OM. It was depicted from Figure 3 that SS of IA has
the highest percentage of OM (9.22%). SS of the RA and CA and the NS contains the
lowest (0.461%). But this result do not support the previous findings of 60% organic
matter (Heckman et al., 1986; Roberts et al., 1988) This is because, the reported sludge
was coming from the sewerage only, but in our country sewerage lines are mixed with the
road side drains and the characteristics of sludge also changed. The present result showed
that OM content was significantly higher in the SS generated from IA in comparison to
NS. No significant difference in the content of OM was observed between the NS and SS
of CA and RA.
Figure 3
Organic matter (%) of normal soil and three different sewage sludge of varied sources
in the study area
10
OM(%)
8
6
4
2
0
RA
CA
IA
Sources
NS
Characteristics and potential uses of sewage sludge
69
3.2.4 Nitrogen
Nitrogen (N) is the main nutrient elements in the soil. That is why the farmers use urea
fertiliser to the crop land to reduce the nitrogen deficiency. SS is a good source of
nitrogen. More over the N in chemical fertiliser is inorganic but in sewage sludge it retain
in organic form. The organic nitrogen breaks down slowly into the soil and gives support
the crop with a long period. On the other hand the chemical N break down very soon after
application and it leached out. In Figure 4 SS of CA had the highest percentage of N
(0.146%). Then it follows the RA (0.146%) and IA (0.053%) and at last the NS
(0.019%). The statistics showed there was significant difference in between NS and RA
and CA. One the other hand there was no significant difference in between NS and IA.
Researchers explained a wide range of N content in SS (Hossain, 2006; Heckman et al.,
1986 reported 17.6%; Roberts et al., 1988 reported 3% and Arcak et al., 2006 reported
1.54% and in normal soil 0.13%). Those findings proved that the N contents in SS
depend upon the nature and source. But all the results including this one it could be
depicted that N% was higher in SS in comparison with NS.
Figure 4
Nitrogen (%) of normal soil and three different sewage sludge of varied sources in the
study area
1.2
1
N(%)
0.8
0.6
0.4
0.2
0
RA
CA
IA
NS
Sour ce s
3.2.5 Phosphorus
After N, Phosphorus (P) is the second prime nutrient to the crop. In this regard SS may be
contributing a good amount of P to the plants. The very common triple super phosphate
(TSP) fertiliser is used through out all over the country both in agri and forest fields. But,
if SS is applied to the field it can save a lot of money of the farmers. In the Figure 5 it
was found that the RA possessed the best range of P (24.8 µg/g). CA contains almost
same (22.767 µg/g) as RA. Then IA and NS possessed 2.65µg/g and 0.91 µg/g. P in
sewage sludge was 581 mg kg–1, found Arcak et al. (2006) and in normal soil
17.48 mg kg1. The analysis report found there was no significant difference of
P concentration in NS than that of IA. But there existed significant difference in between
NS in compared with RA and CA.
70
M.M. Abdullah-Al-Mamun et al.
Figure 5 Phosphorus (µg/g) of normal soil and three different sewage sludge of varied sources in
the study area
30
P(µg/g)
25
20
15
10
5
0
RA
CA
IA
NS
Sour ce s
3.2.6 Potassium
Potassium in SS of RA recorded as the highest (0.787 meq/100g) among the sources,
which was followed by CA (0.447 meq/100g), IA (0.137 meq/100g) and lowest in NS
(0.057 meq/100g). The very use of Murate of Potash (MP) is going on through out the
country. As the normal soil can’t give the potential support to the plants then the SS
application into the ground can help the alternatives of this fertiliser. Kumarasinghe
(1995) found K2O in sewage sludge in residential origin 7.8 mg/g, in sludge 4.9 mg/g and
in industrial origin 5.8 mg/g. The statistical analysis found that NS had significantly
lower amount in comparison with RA and CA. But, there was no significant difference in
IA and NS. This means the SS possessed a high degree of K that could help to the crops
in K limitation soil.
Figure 6
Potassium (meq/100g) of normal soil and three different sewage sludge of varied
sources in the study area
0.9
K(meq/100)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
RA
CA
IA
NS
Sour ce s
3.2.7 Calcium
Davies et al. (1977) explained Ca is an essential element and it maintains the pH level in
the soil. In this report RA 24.65 meq/100g of Ca has found. Similarly followed by IA
Characteristics and potential uses of sewage sludge
71
(22.2 meq/100 g) and CA (14.8 meq/100 g). NS possessed the lowest limit of the Ca
(1.212 meq/100g). Ca found in SS is mainly in the form of CaO, Kumarasinghe (1995)
pointed in sewage sludge in residential origin 56.8 mg/g, in sludge 153.5 mg/g and in
industrial origin 142 mg/g. The SAS analysis found there was a significant difference in
between NS and SS of the described three sources. This gives us a opportunity to apply
SS in Ca deficient soil.
Figure 7
Calcium (meq/100g) of normal soil and three different sewage sludge of varied sources
in the study area
30
Ca(meq/100g)
25
20
15
10
5
0
RA
CA
IA
NS
Sour ce s
3.2.8 Magnesium
Magnesium takes place mostly in oxide form into the soil and discharges slowly from the
soil. This study showed that the lowest content of mg was found in NS (0.148 meq/100 g)
and gradually increasing in CA (0.743 meq/100 g), RA (1.497 meq/100 g) and then in IA
(2.353 meq/100 g). A study pointed (Heckman et al., 1986; Roberts et al., 1988).
1.5% MgO in sewage sludge. Other explained that MgO in SS in residential origin
9.2 mg/g, in sludge 31 mg/g and in industrial origin 33 mg/g (Kumarasinghe, 1995). In
case of Mg also, there was the significant difference in between the NS and all the three
different sources of SS. So, SS can also apply to the Mg poor soil.
Figure 8
Magnesium (meq/100g) of normal soil and three different sewage sludge of varied
sources in the study area
Mg(meq/100g)
2.5
2
1.5
1
0.5
0
RA
CA
IA
Sour ce s
NS
72
M.M. Abdullah-Al-Mamun et al.
3.2.9 Sulpher
Industry is the main source of sulpher (S) related materials. The analysis also supported
the idea as the SS of IA was the prime S holder (246.033 µg/g) than that of the other
areas. After IA the second one was the RA (143.4 µg/g). Both of the results were the
higher concentration in relation to necessity. After them, CA and NS posses 36.75 µg/g
and 26.03 µg/g of S respectively. Hossain (2006) found 1.5% S in sewage sludge. In the
statistical analysis it showed the concentration of S in SS of industrial and residential
origin was significantly higher in comparison with NS. But, there was significant
difference in between CA and NS.
Figure 9
Sulpher (µg/g) of normal soil and three different sewage sludge of varied sources in the
study area
300
250
S(µg/g)
200
150
100
50
0
RA
CA
IA
NS
Sour ce s
Figure 10 Zinc (µg/g) of normal soil and three different sewage sludge of varied sources in the
study area
25
Zn(µg/g)
20
15
10
5
0
RA
CA
IA
NS
Sour ce s
3.2.10 Zinc
Paper, talcum powders, battery, etc., contain zinc (Zn). The industries which produce this
type of products contain Zn. That is why SS of IA contain the maximum amount of Zn
Characteristics and potential uses of sewage sludge
73
(21.403 µg/g), follows gradually lower in NS (10.853 µg/g), RA (6.42 µg/g) and CA
(2.377 µg/g). Arcak et al. (2006) found Zn in Sewage sludge was 109 mg kg-1 and in
normal soil 0.35mgkg–1. In our country Zn found in sewage treatment plant at Pagla was
1193 ppm but in domestic septic tank it was 0.025–0.050 ppm (Amin et al., 1998). The
SAS revealed that Zn had no significant variation between NS and SS of RA and CA. but
it found significant difference between NS and IA.
3.2.11 Boron
Crops need minor amount of B for their growth. But access boron (B) may cause toxicity
to the human body. Normally in soil B has an amount of 20–50 ppm. But this result
pointed a lower limit of B in all the four different areas of soil. The lowest amount
possessed IA (0.507 µg/g). Then gradually increase in NS (0.677 µg/g), CA (0.987 µg/g)
and lastly RA (1d.1 µg/g). The satisfactory content of boron in the soil ranges from about
2–7 kg/ha. The statistical analysis revelled that SS of RA and CA origin had significant
difference in compare with NS. There was found no significant difference between IA
and NS.
Figure 11 Boron (µg/g) of normal soil and three different sewage sludge of varied sources in the
study area
B (µg/g soil)
1.2
B(µg/g)
1
0.8
0.6
0.4
0.2
0
RA
CA
IA
NS
Sour ce s
3.3 Growth performance of raintree (Samanea saman)
3.3.1 Germination percentage
The highest germination (86.667%) was observed in SS of RA followed by SS of CA
(79%) and lowest germination (56%) was in SS of IA (Figure 12). This was because the
RA had got the greater nutrient concentration than others especially in P and K. In case of
N also SS of RA had optimum amount. The SS of CA had the highest value of N and
second highest of P and K. That’s why in this treatment CA got the second highest
germination percentage.
74
M.M. Abdullah-Al-Mamun et al.
(%)Germination
Figure 12 Germination percentage of Samanea saman in different treatment media
90
80
70
60
50
40
30
20
10
0
SS of RA
SS of CA
SS of IA
NS
SS of RA
SS of CA
SS of IA
NS
Different Tre atme nt me dia
3.3.2 Seedling morphological growth
The shoot length of the seedlings was found to be maximum (21.2 cm) in T1 followed by
T3 (17.53 cm). T1 also showed highest collar dia (4.21 mm), whereas lowest collar dia
was observed in control treatment, T0 (1.79 mm). Highest root length was found in T1
(21.2 cm) which was higher from the other treatments. Treatment, T1 showed maximum
leaf number (8.33) followed by treatment, T2 and T3 (7). The imbibitions period was
shortest in T3 (three days), whereas, it was highest in T2 (five days). The fresh weight of
the seedlings had found highest in T1 and followed by CA, IA and NS. The post hoc test
found significant difference in fresh weight in SS of different sources in comparison with
NS.
Table 2
Effect of different growing media on germination and imbibitions of seed, and shoot
length, root length, total length, collar diameter and leaf number of Samanea saman
seedling in the nursery
Length (cm)
Collar
dia
(mm)
Leaf
no.
Total
fresh
weight
40 a
4.21
8.33
2.256a
14.9
31.467b
2.59
7
2.477a
14.03
32.767b
3.05
7
2.27a
24.9b
1.79
5.33
0.87b
Imbibitions
(days)
Shoot
Root
Total
T1
4
21.2
18.8
T2
5
16.57
T3
3
17.53
T0
4
12.06
12.83
Treatment
Notes: Same alphabetic letter(s) in the same column do not vary significantly at P < 0.05,
according to post hoc test.
3.3.3 Dry matter production, vigor index, volume index, and quality index
Shoot dry weight was highest (0.72 g) in T1 treatment. But, root dry weight was highest
in T3. In case of total seedling dry weight, T1 attained the highest (0.89 g), followed by
T2 (0.85g) and it was significantly different from the other treatments. Control treatment
Characteristics and potential uses of sewage sludge
75
(T0) attained the lowest total seedling dry weight (0.69 g). In case of vigor index, T1
(3466.68) attained the highest value followed by T2 (2485.893). Both the volume index
and quality index were highest (375.75 and 0.095 respectively) in T1 and lowest in
control treatment, T0. Sturdiness of seedling was highest in control T0 (67.37) and it was
significantly higher from T1, T2, and T3 treatments (Table 2).
Table 3
Treatment
Effect of different growing media on shoot dry weight, root dry weight, total dry
weight, vigor index, volume index and quality index of Samanea saman seedling in
the nursery
Dry weight (g)
Index
Shoot
Root
Total
Vigor
Volume
Quality
T1
0.72
0.17
T2
0.71
0.14
0.89a
3466.68
375.75
0.095
0.85a
2485.893
111.15
0.074
T3
0.59
T0
0.60
0.20
0.79a
1834.952
163.07
0.090
0.09
0.69b
1859.208
38.64
0.051
Notes: Same alphabetic letter(s) in the same column do not vary significantly at P < 0.05,
according to post hoc test.
4
Conclusions and recommendation
Sewage sludge, also known as biosolids, which is high in organic content and plant
nutrients and, in theory, makes good fertiliser. The millions of tons of sewage sludge
generated each year must go somewhere. If not applied to land, most sludge would have
to be burned in incinerators or land filled. US total annual production of sludge is stable
or only growing slowly; however, in Western Europe, where tougher clean water laws are
beginning to take effect, sludge production is growing significantly, as small
communities build and improve waste treatment plants to comply (Renner, 2000).
Though Bangladesh is a developing country, but a huge amount of SS is produced here. It
can be used in many more option. It contains 48% organic carbon, 17.6% nitrogen,
14.3% P, 1.5% sulphur and other elements like Ca, Mg, Al etc. which we supply through
excessive use of inorganic fertiliser. Our land needs the organic matter. It is life to her
(Hossain, 2006). This study found the different chemical and physical properties of SS of
three types of sources, which shows a better quality than that of the NS. Besides a nursery
experiment also conducted on growth performance of Samanea saman. That study also
shows significant positive growth performance in SS. So, it flourishes a great opportunity
to manage the SS. Like a poor country, ours SS management is very poor. This study
found out a large scale opportunity of uses of SS. It can be used as a growth media, in
crop land, farmyard, incinerator, and land fill, etc. Dowdy et al. (1978) reported that the
increase of crop yield by sludge application often exceed that of well-managed fertilised
controls. In the late 1980s, US researchers also applied sludge to fields of clover and
other legumes. These experiments showed no adverse effects on nitrogen fixation for
plants other than clover (Heckman et al., 1986). In our country heavy metal is not a
serious concern like other developed country. So for a better future, an immediate and
proper step along with economically suitable technology should be taken for gaining the
beneficial services from the SS through scientific management in a developing country
like Bangladesh.
76
M.M. Abdullah-Al-Mamun et al.
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