Journal of Geoscience and Environment Protection, 2014, 2, 14-18
Published Online April 2014 in SciRes. http://www.scirp.org/journal/gep
http://dx.doi.org/10.4236/gep.2014.22003
How to cite this paper: Al-Musharaf i, S. K. et al. (2014). Environmental Contamination by Industrial Effluents and Sludge
Relative to Heavy Metals. Journal of Geoscience and Environment Protection, 2, 14-18.
http://dx.doi.org/10.4236/gep.2014.22003
Environmental Contamination by Industrial
Effluents and Sludge Relative to Heavy
Metals
S. K. Al-Musharafi1, I. Y. Mahmoud2, S. N. Al-Bahry3
1Department of Applied Biotechnology, Sur College of Applied Sciences, Sur, Oman
2Department of Biological Sciences and Chemistry, University of Nizwa, Nizwa, Oman
3Department of Biology, College of Science, Sultan Qaboos University, Muscat, Oman
Received Dec emb er 2013
Abstract
Oman is located in the tropic of Cancer with extremely hot temperatures ranging between 15˚C
-25˚C in winter and 30 - 48˚C in the summer with low rainfall. Most of the water source is desali-
nated seawater. Recycling of sewage effluent is a common practice used for farming, public parks
and industry. The dried sludge product is used as fertilizer. The highly concentrated sludge with
heavy metals is either incinerated or buried in landfills. Heavy metals were analyzed and com-
pared in treated sewage effluent (TSE), slurry sludge, dried sludge, landfill and underground wa-
ter. Heavy metal concentrations were analyzed using the inductive coupled plasma optical emis-
sion spectrometer (ICP-OES). All samples contained the same heavy metals with different concen-
trations. The heaviest concentrations were Zn, Cr, Cu and Ni with traces of V, Cd, Pb and Ba. TSE
and sludge were the main sources of landfill and underground water contamination. Due to water
evaporatio n, heavy metals concentrations in sludge were higher compared to TSE and under-
ground water. Dried sludge and landfill contained higher concentrations than the others. Based on
this investigation, it appears that the source of heavy metals is from TSE originated mainly in in-
dustries. If the infiltration of heavy metals to underground water continues, it will be a serious en-
vironmental and health problem in the future.
Keywords
Cont aminatio n ; Heavy Metal s; Treated Sewage Effluent; Sludge; Landfill ; Underground Wa ter
1. Introduction
Due to low rainfall in Oman, seawater desalination is the main source of potable water. Sewage water is rec-
laimed through sewage treatment plants established in main metropolitan areas in Oman. Treated sewage efflu-
ent (TSE) is predominantly used for irrigation, which consequently is the major source of heavy metal contami-
nation. In Oman, during the last few years, there has been a steady increase in heavy metal concentrations at

S. K. Al-Musharafi et al.
15
different habitats (Al-Bahry et al., 2011, Al-Musharafi et al., 2012, 2013a, 2013b, 2013c; Al-Rawahi et al.,
2007). It was also reported that heavy metal concentration in the three sewage treatment plants (STP) was re-
lated to heavy metals in sludge irrigated with TSE (Al-Musharafi et al., 2012).
The accumulation of heavy metals in aquatic and terrestrial habitats is dramatically on the rise, especially in
the industrial countries of the world. The heavy metal contamination ends up infiltrating ecological niches such
as soil which consequently reaches underground water and wells. In addition, heavy metals can also contaminate
agriculture fields, rivers and seas (Al-Bahry et al., 2011; Al-Musahrafi et al., 2013c; Al-Rawahi, 2007). Heavy
metals in some sectors of the world are contaminating wild life, crops, domestic animal and humans (Fent, K.,
1996; Harper et al., 2007; Jeffree et al., 2006; Kojadinovic et al., 2007; Kannan et al., 2006; Mapanda et al.,
2007; Storelli et al, 2008; Zauke et al., 2003). Heavy metal contamination might develop into severe health
problems which can lead to serious diseases (Mishra et al., 2010).
Some heavy metals are toxic to animals and plants because of their affinity to bind with proteins (Al-Musharafi
et al., 2012). Heavy metal accumulation can be a factor in poisoning some organisms which in turn can be fatal
(Harper et al., 2007; Kojadinovic et al., 2007; Storelli et al., 2008; Kannan et al., 2006; Jeffree et al., 2006;
Zauke et al., 2003). However, some heavy metals such as Co, Cu, Mn and Zn are essential for the enzymatic
reactions but they can be toxic at high concentrations (Fent et al., 1996).
Rules and regulations must be set internationally concerning heavy metals usage in industry and agriculture.
International committees must be organized to set up regulations controlling and minimizing heavy metal con-
tamination of the environment.
The aim of this investigation is to evaluate the impact of heavy metal contamination from sludge generated
from industrial source STP, buried in landfills and to assess its contamination of underground water which may
affect environment and human health.
2. Materials and Met hod s
The study area is located near the industrial sector in Oman. Samples were collected from the STPs recycled in-
dustrial effluents. TSE and sludge were collected twice monthly during March through September. During the
study period, temperature ranged between 30˚C - 48˚C, with no precipitation.
One liter effluent and underground water samples were collected for heavy metal analysis (Carter et al., 2000).
Samples were preserved in a cooler at 10˚C (APHA, AWWA, & WEP, 1998).
Sterile plastic bags were used to collect sludge and landfill samples. The samples were dried at 105˚C for 3 h.
0.2 g of samples were placed in perfluoroalkoxy polymer container and mixed with concentrated nitric acid (4
ml) and of hydrofluoric acid (0.5 ml), and heated in a microwave for 40 min. The samples were diluted to 100
ml water. All solutions from the samples were diluted to a final concentration of 1 g/l (Moor et al., 2001).
Underground water and TSE samples were filtered and analyzed for Ba, Cd, Cr, Cu, Ni, Pb, V and Zn using
inductively coupled plasma optical emission spectrometer (ICP-OES) type Perkin Elmer 3300 DV ICP (USA).
Blank, certified control samples were used as references.
3. Results
Heavy metals concentrations in TSE were slightly lower than in sludge and landfill but higher than the under-
ground water (Figures 1- 5 ). Analyses of heavy metals in all samples revealed that the major metals in order of
their abundance were Zn, Cr, Cu, Ni followed by traces of V and Cd (Figure 2).
When the slurry sludge was desiccated and the water evaporated completely, the concentrations of the same
metals increased because of the decrease in sludge volume (Figure 3). When the heavy metals in the dry sludge
and landfills were compared, the dry sludge had a slightly lower concentration (Figure 4).
The underground water contaminated by TSE and sludge showed lower concentration than the rest of the
study samples (Figure 5).
4. Discussion
In an arid region, such as Oman, the water resource is inadequate which forces the authorities to establish the
desalination program throughout the country. In addition, reclaimed sewage water is on the increase to be used
in farming and industrial sectors. As a result of this practice, there is a wide spread of heavy metals throughout

S. K. Al-Musharafi et al.
16
Figure 1. Heavy metal concentration in TSE.
Figure 2 . Heavy metal concentration in slurry sludge.
Figure 3. Heavy metal concentration in dried sludge.
Figure 4. Heavy metal concentration in landfill.

S. K. Al-Musharafi et al.
17
Figure 5. Heavy metal concentrations in underground water.
the environment.
Based on this study, it appears that the major source of heavy metal contamination is from TSE and sludge.
There is a strong indication that the heavy metals in Oman are spreading rapidly throughout different habitats
because of rapid increase in population and industries (Al-Bahry et al., 2011, Al-Musharafi et al., 2012, 2013a,
2013b, 2013c; Al-Rawahi et al., 2007).
In this study, sewage water, slurry sludge, dried sludge, landfill and underground water were examined to
evaluate the heavy metal contamination. The data revealed that there is widespread heavy metal contamination
in the study areas. It was also found that water and sewage samples were contaminated by heavy metals caused
by STP from the industrial effluents and was correlated with sludge and underground water. STPs used from
industries had higher concentration compared to STP from residential communities, hospitals and public institu-
tions (Al-Musharafi et al., 2012).
Based on the present data, it was revealed that heavy metals contaminated underground water but with less
intensity than the rest of sampling areas. It was also reported that heavy metals accumulated in soil can penetrate
into the underground water (Al-Musharafi et al., 2012; Skeat, 1969).
Heavy metal contamination resulting from industrial effluents was reported in snails, grass roots, TSE and se-
diment (AlMusharafi et al., 2013a). In addition, heavy metal contaminations in different habitats were found in
Oman (Al-Bahry et al., 2011; Al-Musharafi et al., 2013a).
Further investigations concerning heavy metal pollution in different areas in Oman are needed in order to
compare the degree of heavy metal contamination in the various regions.
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