Page 33 - Materials Chemistry, Second Edition

14 Life Cycle Assessment of Wastewater Treatment

bodies. The depletion of dissolved oxygen affects the aquatic organisms by decreas-
ing the immunity of fish, resulting in growth inhibition and early death, and it affects
the population of the living organisms (Okereke et al., 2016). The optimum level
−3
of dissolved oxygen in the wastewater is around 8–10 g m . When the biological
−3
oxygen demand (BOD) levels of wastewater are below 4 g m , the stream is said
to possess healthy levels of dissolved oxygen, and the stream framework can man-
age the amount of waste without influencing the fish. At a dissolved oxygen level of
3
−3
5 g/m , the fish become noticeably stressed, and at 2 g m , the fish will die from
lack of oxygen unless they can move to more oxygenated waters (Ministry for the
Environment New Zealand).

1.5.6 persisTenT organic polluTanTs
A group of chemicals which are discharged in waste from certain industries have
high stability, and these are a growing threat to living organisms globally. These
pollutants are generally released as a final waste product during manufacture and
can also be by-products. Highly chlorinated compounds, such as polychlorinated
biphenyls (PCB), dichlorodiphenyltrichloroethane (DDT), polychlorinated dioxins
(PCD), dibenzofurans and polycyclic aromatic hydrocarbons (PAH), are highly toxic
and bioaccumulative. They seriously affect the health of human beings by causing
cancer, thyroid imbalance, psychological issues, diabetes, and many fatal diseases.
They are highly harmful and act as EDC (Schwarzenbach, 2010).

1.6 IMPACTS OF WASTEWATER ON PUBLIC HEALTH
Basically, wastewater contains contaminants such as heavy metals, dyes, pesticides,
EDC, persistent organic pollutants, and nutrients. Each contaminant has a unique
negative impact on the human body and poses a serious threat to human health.

1.6.1 Heavy MeTal poisoning
Heavy metal poisoning is one of the major issues caused by industrial wastewater,
and it results from the aggregation of heavy metals in lethal concentrations in the
delicate tissues of the human body (Naushad et al., 2017). The extent of toxicity var-
ies according to the type of metal accumulated. In general, low concentrations of
heavy metals are required for the proper functioning of the human body, and when
the bio-recommendation for heavy metals is exceeded in the tissues, heavy metal
poisoning occurs. The most toxic heavy metals, which cause harmful diseases even
in trace concentrations, are mercury, lead, arsenic, and cadmium. Industrial activi-
ties and other anthropogenic activities are the main sources of heavy metal poison-
ing. Table 1.2 clearly explains the different ill effects caused by heavy metals.
Lead is the most noteworthy of the metals that cause heavy metal poisoning, and
it is mainly taken in through ingestion in food, water and mostly through air. Lead
poisoning affects hemoglobin production, the kidneys, the joints, the regenerative
systems, and the cardiovascular framework and causes major and irreversible harm
to the brain. Its different impacts include harm to the gastrointestinal tract (GIT), the