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Freshwater Shortage Brings Need for Wastewater Treatment Essay

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CHAPTER 1 INTRODUCTION Despite the fact that the world is two-thirds water, most of it is not potable. Population expansion and industrial development has deteriorated the quality of freshwater reservoirs around the world and has caused freshwater shortages in certain areas. To meet the growing population’s demand for freshwater, wastewater treatment techniques aimed at remediating municipal wastewater and industrial wastewater should be employed. Municipal wastewater mainly consists of domestic wastewaters originated from households, sewer overflows and partially (or pre-) treated industrial wastewaters. Different industries produce various kinds of industrial wastewater based on their own specific combination of pollutants. Among…show more content…
During primary treatment, pretreatment is performed which involves the usage of bar screens to remove large solids from the wastewater. The water is then pumped to pre-aeration tanks where grit (sand, eggshells, etc.) is removed. Next, the wastewater is fed to a primary clarifier where suspended solids are allowed to settle (primary settlement). After the primary clarifier, the wastewater still contains high amount of organic content and should be sent to secondary treatment. During the secondary treatment, the organic content of the wastewater is degraded by microorganisms within the aeration tanks, and waste sludge is allowed to settle in the secondary clarifiers. Sludge that settles on the bottom of the primary and secondary clarifiers is pumped to a digester via a sludge thickener to produce methane and carbon dioxide [4]. However, the water leaving the secondary clarifier still contains significant amounts of nitrogen and phosphorus. Also in this process, there is no special method employed during the treatment cycle to remove heavy metals from wastewater. 1.2 Nitrogen, Phosphorus and Heavy metal Contamination 1.2.1 Nitrogen and Phosphorus Contamination (a) Sources Conventional wastewater treatment can remove phosphorus and nitrogen concentrations in wastewater to a limited extent [5]. Discharge of this untreated water leads to high release of nitrates and
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