Page 220 - Materials Chemistry, Second Edition

Green and Eco-Friendly Materials for Removal of Phosphorus 201

oxygen and toxicity in fish. The existence of heavy metals such as arsenic, mercury,
lead, cadmium, copper, chromium, manganese, nickel, and zinc causes extreme
health issues, and damages aquatic flora and fauna (Wang and Peng, 2010). Some of
the organic pollutants are non-biodegradable and persist in nature, thus affecting the
environment for decades (La Farre et al., 2008). Also, most of them are highly toxic
and carcinogenic in nature.

10.1.2 HarMful effecTs of pHospHorus
Phosphorus is a non-renewable resource, necessary for the growth of different
organisms in the ecosystem. Elemental phosphorus is toxic and exists in ortho, tri-
poly, pyro, and organic states. Phosphorus is used in nature in very limited and
small quantities (Weikard and Seyhan, 2009; Frossard et al., 2000). It is found in the
Earth’s crust in igneous and phosphorus rocks in relatively large proportions, while
small quantities are available in sea water (Nash, 1984). Phosphorus enters into the
environment by natural biogeochemical processes such as weathering. It plays an
important role in different cycles of nature, such as the carbon and phosphorus cycle
(Mackenzie et al., 2002). This delicate balance of phosphorus in the environment
is maintained adequately by nature’s forces (Schroder et al., 2011). Weathering is
a lengthy process, through which phosphorus enters naturally into the system in a
calculated manner, but interference through manual weathering leads to an increase
in the rate of extraction, resulting in global changes disturbing the stability. Most
importantly, excessive availability of phosphorus disturbs the ecological balance
by triggering the eutrophication of water bodies, thereby resulting in the uncon-
trolled growth of aquatic plants and algae. Thus, excessive growth of water weeds
and algae is the result of high levels of phosphorus in the aquatic system. Blooming
of algae increases the chlorine dosage that needs to be supplied for treating water
to be made palatable (Fisher et al., 2004), leading to the formation of high levels
of cancer-causing disinfectant by-products (Wang et al., 2007). Furthermore, the
excessive level of phosphorus stimulates the activity of noxious microbes (Nygaard
and Tobiesen, 1993). Noxious Microcystis cyanobacteria produces a toxic substance
(microcystin), which is poisonous to aquatic species and may cause hepatocellular
carcinoma in humans (Vezie et al., 2002; Chong et al., 2000). Quantitatively, the
−1
addition of even 0.1–5.6 μg L triggers the process of algal blooming (Bowman et al.,
2007). Moreover, depletion of dissolved oxygen is one of the serious consequences of
enhanced levels of phosphorus in the aquatic system (Tiessen, 1995). Another source
of phosphorus is the fertilizers used in agriculture and treated and untreated sew-
age wastewater (Kirkham, 1982). Phosphorus occurs in nature in an insoluble form,
which often controls the proliferation of the soluble form, with major implications
for agriculture (Bennett et al., 2001). Phosphorus is considered to be one of the main
constituents of domestic sewage, which includes phosphorus from detergents and
human feces. Sewage sludge ranks second on the basis of phosphorus content and
is a promising source for its recovery (Cordell et al., 2011; Havukainen et al., 2016).
Phosphorus is widely used in detergents. Soaps and detergents contain large amounts
of phosphorus as their basic ingredient; it emerges into the aquatic system through
washing. During World War II, soaps were replaced by biodegradable detergents,