1 Heavy Metals in the Environment
Heavy metals are the primary pollutants which were ranked by Disability-Adjusted
Life Years (DALYs) as the world’s worst pollution that causes countless deaths and
disabilities [1]. Heavy metals are metals with density at least five times than that of
water [2]. The most common toxic heavy metals are lead, cadmium, chromium,
mercury, and arsenic. Human activities are the primary driver of heavy metal
production and pollution. Some of the common industries that produce heavy metals
are battery recycling, metal mining and processing, smelting, industrial and municipal dumping grounds, chemical and product manufacture, tannery, and industries
related to the dye [1, 3].
Heavy metal contamination occurs when these toxic metals enter a water supply
by industrial and consumer wastes. Acidic rain also breaks down soils and releases
heavy metals into water streams, groundwater, lakes, rivers, and ocean. Exposure to
a high level of heavy metals is a real threat not only to human but also to animals and
the ecosystem at large. The carcinogenicity and toxicity of the heavy metals with
their tendency to accumulate in biological system and ecosystem make them a
significant health hazard that contributes to disease and poverty on a global scale
[4–6]. For instance, in an aquatic ecosystem, heavy metals accumulate in fish tissues
which magnify as the fishes move up in a food chain system [7]. As the fishes grow,
more heavy metals accumulate in its tissues, thus, causing more toxicity to its
predators. Mercury, which is one of the most toxic heavy metals in the environment,
causes a decline in the rate of hatching for aquatic species such as fish and waterfowl.
This event affects the number of species, causing significant changes in the aquatic
ecosystem. Wright and Welbourn [8] also reported that lead affects the daily
function of fish by damaging its gill and also stopping the production of enzymes
for photosynthesis. Another study by Bradl [9] found that cadmium contamination
causes skeletal deformities and kidney damage in fishes. The report also mentioned
abnormal plant growth due to the cadmium pollution.
Although some heavy metals such as copper and zinc are essential to human
health in minuscule amounts, these heavy metals are dangerous and pose adverse
health effects at high concentrations [9]. Table 9.1 tabulates some of the effects of
heavy metal contamination on human health.
2 Agricultural Waste Biomass
The high impact of heavy metal pollution in water has spurred numerous studies on
this subject. There are a variety of techniques used in controlling water pollution due
to heavy metals. Some of the commonly used methods are chemical precipitation,
coagulation, electrochemical treatment, filtration, and ion exchange. However, the
drawbacks for these methods include high initial or operational costs, large use of
chemicals, large amount of sludge and extra cost for its removal, and excessive
374
S.-F. Lim et al.
Heavy metals are the primary pollutants which were ranked by Disability-Adjusted
Life Years (DALYs) as the world’s worst pollution that causes countless deaths and
disabilities [1]. Heavy metals are metals with density at least five times than that of
water [2]. The most common toxic heavy metals are lead, cadmium, chromium,
mercury, and arsenic. Human activities are the primary driver of heavy metal
production and pollution. Some of the common industries that produce heavy metals
are battery recycling, metal mining and processing, smelting, industrial and municipal dumping grounds, chemical and product manufacture, tannery, and industries
related to the dye [1, 3].
Heavy metal contamination occurs when these toxic metals enter a water supply
by industrial and consumer wastes. Acidic rain also breaks down soils and releases
heavy metals into water streams, groundwater, lakes, rivers, and ocean. Exposure to
a high level of heavy metals is a real threat not only to human but also to animals and
the ecosystem at large. The carcinogenicity and toxicity of the heavy metals with
their tendency to accumulate in biological system and ecosystem make them a
significant health hazard that contributes to disease and poverty on a global scale
[4–6]. For instance, in an aquatic ecosystem, heavy metals accumulate in fish tissues
which magnify as the fishes move up in a food chain system [7]. As the fishes grow,
more heavy metals accumulate in its tissues, thus, causing more toxicity to its
predators. Mercury, which is one of the most toxic heavy metals in the environment,
causes a decline in the rate of hatching for aquatic species such as fish and waterfowl.
This event affects the number of species, causing significant changes in the aquatic
ecosystem. Wright and Welbourn [8] also reported that lead affects the daily
function of fish by damaging its gill and also stopping the production of enzymes
for photosynthesis. Another study by Bradl [9] found that cadmium contamination
causes skeletal deformities and kidney damage in fishes. The report also mentioned
abnormal plant growth due to the cadmium pollution.
Although some heavy metals such as copper and zinc are essential to human
health in minuscule amounts, these heavy metals are dangerous and pose adverse
health effects at high concentrations [9]. Table 9.1 tabulates some of the effects of
heavy metal contamination on human health.
2 Agricultural Waste Biomass
The high impact of heavy metal pollution in water has spurred numerous studies on
this subject. There are a variety of techniques used in controlling water pollution due
to heavy metals. Some of the commonly used methods are chemical precipitation,
coagulation, electrochemical treatment, filtration, and ion exchange. However, the
drawbacks for these methods include high initial or operational costs, large use of
chemicals, large amount of sludge and extra cost for its removal, and excessive
374
S.-F. Lim et al.