Abstract
This present study evaluated the levels of heavy metals and microbial properties of leachate and hard water samples obtained from lemna dumpsites. The heavy metals in leachate and hard water samples were determined using the WAGTECH photometer (Model 7100) for the analysis of iron, chromium, manganese, zinc, copper and aluminium while WAGTECH Arsernator Model W5000063 for the analysis of arsenic. Microbial population in samples were determined using standard microbiological procedures. The result showed that the leachate samples yielded the highest total heterotrophic bacteria counts of 6.2× 105 CFU/ml, while the hard water yielded the highest total coliform counts of 3.07 × 105 CFU/ml and total fungi count of 4.2 × 105 CFU/ml. The prevalent bacteria species from the leachate and hard water samples were Streptococcus feacalis, Escherichia coli, Pseudomonas aeruginosa, Serratia marcensen, Staphylococcus aureus and Bacillus subtilis and four fungal species were identified: Penicillium spp, Aspergillus spp, Fusarium spp and Yeast spp. The result of the heavy metal analysis shows that the sequence of leachates content in the heavy metals determined in this study follows the trend: Cu > Al > Zn > Fe > Cr > Mn > As while the sequence in hard water was Fe > Al > Cu > Zn > Mn > Cr > As having the lowest to be arsenic indicating absence of Arsenic in the hard water samples. This imply that virtually most of the parameters determined were above the World Health Organization/Nigeria Drinking Water Quality Standard permissible limits for drinking water. It was concluded that the levels of contaminants present in the dumpsite could be hazardous to the management staff of the dumpsite. Government should develop a sustainable plan for effective management and recycling of generated wastes to caution it impact on neighboring underground water table.
Keywords: Pollution; Leachate; Dumpsites; Hard-Water; Microbes; Lemna
Abbreviations: WHO: World Health Organization; NDWQS: Nigeria Drinking Water Quality Standard; LSD: Least Significant Difference Test; NS: No Significance; THBC: Total Heterotrophic Bacteria Count; TCC: Total Coliform Count; TFC: Total Fungi Count; LSD: Least Significant Difference; H2S: Hydrogen Sulphides; WSA: Water Sample Containing Leachate; WSB: Water Sample Containing Hard Water
Introduction
Solid waste management is of global concern in both developing
and developed countries. Despite much awareness aimed at
reducing the waste generated due to anthropogenic activities,
there has been an increase in solid waste generation throughout
the world [1]. This could partly be due to increase in population,
industrialization and urbanization. Different efforts geared
toward effective management of solid waste due to the perceived
adverse health and environmental impacts have been reported [2]. Landfilling remains one of the most commonly used methods for
solid waste management in most parts of the world. Its efficiency
and safety coupled with cost make it the preferred method [3].
Several advances in landfill technology have been reported to
enhance its suitability for solid waste management. Leachate is
defined as any contaminated liquid that is generated from water
percolating through a solid waste disposal site, accumulating
contaminants, and moving into subsurface areas. Leachate is often
generated from landfill processes due to the increasing presence
of soil moisture and other favorable environmental factors. In
most developing countries, the facility for leachate collection and
treatment is often not part of the design of landfill sites. One of
the adverse effects caused by solid waste disposal onto landfills
is the contamination of surface and groundwater by leachate. The
extent of such contamination depends on the quality of leachate
generated from the landfill. Solid wastes that constitute nuisance
to the environment consist of household waste, construction
and demolition debris of residence and street wastes generated
from residential and commercial complexes. Garbage has often
originated enormously from the rapid urbanization, changes in the
life style and food habits, resulting in increase in the amount and
types of solid waste [4].
In the absence of a confining barrier beneath or surrounding
the waste disposal site, this leachate can migrate and contaminate
subsurface and surface waters. The volume of leachate generated
varies with the amount of precipitation and storm water run-on and
run-off, the volume of groundwater entering the waste-containing
zone, and the moisture content and absorbent capacity of the
waste material. When leachate is collected via perforated pipes,
rainfall significantly affects leachate volume and contaminant
concentrations [5,6] listed SZ landfill age, ambient air temperature,
precipitation and refuse permeability, depth, temperature, and
waste composition as factors that affect leachate quantity and
composition. It has been reported that leachate composition and
strength vary widely from landfill to landfill and even within a given
landfill. Variability in leachate volume and pollutant concentration
is generally less predictable than variability in groundwater flow;
hence the design of collection and treatment systems must include
provisions for addressing uncertainty. In such instances, flow
equalization may be used to offset variable leachate volume and
contaminant loading. Leachate control should, therefore, be included
in the design of solid waste management systems. The volume and
flow rate of the leachates are dependent upon the percolation of
water through the waste layers. The transfer of contaminants into
the leachate and biodegradation processes is affected by the flow
patterns and velocity of the leachate [7]. Percolation from the
unsaturated zone into the saturated zone is thus possible, and this
gives a pathway for groundwater contamination. Surface runoff
through the landfill also provides a possible route to surface water
contamination majorly during precipitation events.
The generation of leachate from landfills if not properly
managed can lead to several adverse environmental and health
impacts [8,9]. The risks of leachate generation can be mitigated by
properly designed and engineered landfill sites, such as those that
are constructed on geologically impermeable materials or sites that
use impermeable liners made of geomembranes or engineered clay.
In addition, most toxic and difficult materials are now specifically
excluded from land filling. However, despite much stricter statutory
controls, leachates from modern sites are often found to contain
a range of contaminants stemming from illegal activity or legally
discarded household and domestic products [10].
Materials and Method
Leachate and hard water samples were collected at Lemna dumpsite in Calabar Municipality, Cross River State. The leachate was collected from the base of the solid waste heap, the leachate drained from the heap as a result of gravity while the hard water sample was collected from the surrounding of Lemna dumpsite. The samples were transported to the laboratory for analysis.
Microbial Analysis
The total heterotrophic bacterial count (THB) was determined by cultural techniques i.e., by plating into nutrient agar (NA), and fungi by plating into Sabouraud dextrose agar. Ten (10) fold serial dilutions with one gram of the sample, 0.1ml of 10-4 dilution was placed on the plates in triplicate and incubation at 280C for 18 hours and 370C for 72 hours for bacteria and fungi respectively. The colonies were then counted and expressed as colony forming units per gram,
Heavy Metal Analysis
Estimation of the heavy metal content in the water sample was analyzed using the WAGTECH Photometer Model 7100 for the determination of Iron, Chromium, Manganese, Zinc, Copper and Aluminium; WAGTECH Arsenator Model W5000063 was used for the determination of Arsenic.
Statistical Analysis
Data collected were subjected to a one-way analysis of variance (ANOVA). While significant means were separated using least significant difference (LSD) test at 5% probability level.
Results and Discussion
Heavy Metal Content in Water Samples Collected from the Dumpsites
The result as presented on Table 1 revealed different levels of leachate and hard water contents in water samples obtained from the Lemna dumpsite. The parameters used includes iron, chromium, manganese, zinc, copper, arsenic and aluminum. Comparing with the WHO/NDWQS standards high significant difference was observed in some heavy metals, with no significant difference in chromium and manganese. The Environmental Protection Agency (EPA) considers iron in water as a secondary contaminant, which means it does not have a direct impact on health. The secondary Maximum Contaminant Level set out by the WHO is 0.3 milligrams per litre. Iron present in the leachate samples was 2.31mg/l exceeded the WHO/NDWQS standards of 0.3mg/l while the Fe in hard water was 0.39mg/l also above the set standard. Chromium and its compounds are toxic when inhaled and ingested. The EPA considers iron in water as a secondary contaminant, which means it does not have a direct impact on health. The Secondary Maximum Contaminant Level set out by the WHO is 0.05 milligrams per litre. Chromium in leachate was 0.54mg/l higher than the WHO/NDWQS standards of 0.05mg/l while the Cr in hard water was 0.01mg/l, therefore the level of chromium is not enough for contamination. Manganese toxicity can result in permanent neurological disorders known as manganese. The Mn in hard water was 0.012mg/l while the Mn in the leachate was 0.0017mg/l below the WHO/NDWQS standards of 0.1mg/l making it partially fit for consumption. Zinc is an essential trace element with very low toxicity in humans.
From the result, the Zn in the leachate samples was 2.66mg/l while the Zn in hard water was 0.07mg/l below the WHO/NDWQS standards which is 3mg/l making it fit with a major significant difference between them. Copper present in leachate was 6.60mg/l exceeded the WHO/NDWQS standards of 1mg/l while Cu in the hard water was 0.34mg/l did below the WHO/NDWQS standards. The leachate had Arsenic value of 0.01mg/l while the hard water sample has Arsenic level of 0.00mg/l below the WHO/NDWQS standards making it less injurious to human health. Aluminium present in the leachate was 2.68mg/l and the hard water had Al of 0.38mg/l, these values exceeded the WHO/NDWQS standards of 0.2mg/l which is unfit and ingestion by humans could cause serious health problems. The sequence of heavy metals in leachate samples determined in this study follows the trend: Cu > Al > Zn > Fe > Cr > Mn > As while the sequence in hard water was Fe > Al > Cu > Zn > Mn > Cr > As having the lowest to be arsenic. The heavy metal content in the samples showed high significant differences. The LSD at 5% showed that Arsenic and Aluminium had the highest significant difference followed by zinc and iron next to copper in that order, meanwhile, Chromium and Manganese had no least significant difference.
Microbial Analysis of Water Samples Collected from the Dumpsites
Table 2 show the mean total bacterial, coliform and fungi counts in samples from the dumpsite. The analysis therefore reveals total heterotrophic bacteria counts ranged from 5.67×105 cfu/ml to 6.2×105 cfu/ml, the highest bacteria counts was obtained in the leachate samples while the hard water had the least bacterial counts. Coliform counts ranged from 2.0×105 cfu/ml to 3.07×105 cfu/ml, the highest coliform counts were obtained in the hard water sample with mean of 3.07×105 cfu/ml, significantly higher than the coliform counts in leachate sample 2.0×105 cfu/ml. The mean total fungi count ranged from 3.0×105 cfu/ml to 4.2×105 cfu/ml in hard water sample, significantly higher than the fungi counts in leachate sample with a count of 3.0×105 cfu/ml. The bacterial, coliform and fungal counts from the dumpsite samples showed significant differences. The least significant difference test at 5% probability showed that the fungal counts was the highest, followed by the coliform and bacterial counts.
Cultural Characterization and Identification of Microbial Isolates
The microbial isolates were identified on the basis of their cultural cellular morphology, gram’s reaction, biochemical characterization and net mount techniques. The tentative bacteria and coliform isolates from the various samples were Escherichia coli, Pseudomonas aeruginosa, Serratia and Staphylococcus aureus. The above organisms were confirmed after a careful comparism of the various test results carried out with the Bergy manual for bacteriological identification. Meanwhile, the fungi isolates include Penicillium spp, Yeast spp, Aspergillus spp and Fusarium spp they were confirmed using the mycological manual for fungi identification (Tables 3 & 4).
Discussion
Lemna solid waste dumpsite is an unlined, uncontrolled planned
and open dumpsite. This dumpsite harbored E-wastes, agricultural
wastes, medical wastes and all forms of hazardous wastes. A
discussion is provided in Table 1 regarding the maximum limit of
contaminants in leachate and hard water prior to its disposal into
the environment. However, due to extreme variation of leachate
composition and operating conditions in different landfills, no
guideline or standard operating procedures for leachate treatment
and disposal can be effectively chalked out. Solid waste are being sorted out into biodegradable and non-biodegradable wastes as is
the practice in developed countries due to the current management
availed to the control of waste deposited in the environment.
Industrial waste which normally contains toxic chemicals and
sometimes radio-active substances including electronic wastes,
are dumped together with domestic, market and commercial
wastes, when mashed together generates fluids known as leachate
during the dry and wet season there is a constant run-off from
this compost. In this compost, there is presence of bacteria, fungi,
and other pathogens including the presence of heavy metals. It is
known that the run-of is connected to major water pathways which
causes contamination and makes it unfit for consumption. The
observed characteristics of leachate and heavy metal contaminated
water samples maybe associated with the heavy rainfall that
occurs during the rainy season and liquid content present in the
waste which might encourage the leaching of the pollutants in the
surrounding water.
The present observation indicates that the water samples
are indeed polluted when compared with the World Health
Organization and Nigerian Drinking Water Quality standards.
Additionally, the extent of the pollution of the groundwater
increases with decreasing distance from the landfill. Inorganic and
heavy metals have been reported to be retained at a lower level
than organic chemicals and pesticides [11,12], also reported that
the concentrations of pollutants in leachate vary with depth of
groundwater and the distance from the landfill. Generally, the total
bacteria population of the water samples is higher in wet season
than in dry season, this observation is evident in the study conducted
out by Hammond and Beliles [13]. The presence of coliform
bacteria in the water samples as observed in this study is a source
of concern. These bacteria have been associated with a number of
health problems such as cholera, vomiting and diarrhoea [14]. The
use of leachate contaminated water for domestic purposes may
cause several pathological diseases as indicated earlier. Presence
of E. coli and total coliform bacteria indicates microbial pollution of
the groundwater by anthropogenic activities. All bacterial isolates
recovered from the waste dumpsite samples except Serratia spp
are directly implicated in food-borne infections such as diarrhoea,
typhoid and gastroenteritis. The usual disease pathway includes
placing contaminated hands in the mouth or eating food, through
vector insects such as cockroaches or mosquitoes or directly
inhaling airborne dust particles contaminated with pollutants.
The study further revealed that the concentration of waste
materials in the landfill site had systematically polluted the soil and
groundwater over time. The effect of such pollution as determined
from the study declined away from the polluting source. This
implied that the contamination of the surrounding water was more
dependent on proximity to dump sites. The less dependency has
been attributed to the influence of topography, type, state of waste
disposal systems and to some extent, the hydrogeology of the area.
Conclusion
The level of pollution, seepage into surrounding water at the dumpsite was studied by sampling water at the dumpsite containing leachate and heavy metals to reveal the microbial properties, heavy metal contents, characterization. The study revealed that the composition and disposal of solid waste in Calabar metropolis potentially have environmental and public health implications. Therefore, it is pertinent to conclude that the open waste dump at the lemna dumpsite constitute a source of microbial and toxic chemical contamination of the dumpsite. The dumpsite has to a greater extent influenced the pollution or contamination of the surface water bodies within the vicinity.
Acknowledgement
We acknowledged all researchers whose articles were cited during this research and appreciate my co-authors for their contributions in make up this article.
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