Characteristics of Wastewater

Characteristics of Wastewater

DOI: 10.4018/978-1-5225-9441-3.ch001

Abstract

Wastewater is defined as any water that has been negatively affected in quality by humans and is a complex mixture of inorganic and organic materials. Wastewater is used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff or stormwater, and any sewer inflow or sewer infiltration. As technological changes take place in manufacturing, changes also occur in the compounds discharged and resulting wastewater characteristics. High amounts of inorganic and organic matter discharged via process effluent can seriously impair water sources or result in toxic levels in soil. Therefore, the purpose of this wastewater characterization chapter is to provide a plan for sampling and analysis of the wastewater to obtain baseline data for an expanded list of wastewater characteristics. The characterization results will assist in further identifying locations of concern and any additional pollutants that may require control or could interfere with wastewater operations.
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Characterization Of Wastewater

To design an efficient maneuver of treatment process, characterization of wastewater is perhaps the most critical step. Concentrations of pollutants vary significantly from industry to industry hence the need for characterization of effluent discharges (Henze and Comeau). Wastewater can contain physical, chemical and biological pollutants (Odlare, 2014). Water pollutants may originate from point sources or from dispersed sources. A point-source pollutant is one that reaches water from a single pipeline or channel, such as a sewage discharge or outfall pipe. Dispersed sources are broad, unconfined areas from which pollutants enter a body of water. Food and beverage manufacturing can require large amounts of water and thus generate large volumes of wastewater. Types of wastewater include: domestic wastewater from households, municipal wastewater from communities (also called sewage) or industrial wastewater from industrial activities.

Effluent from the manufacturing processes typically contain high concentrations of organic contaminants such as biochemical oxygen demand (BOD), total suspended solids (TSS), as well as fats, oils, and grease (FOG). Effluent pH, temperature and nutrients (e.g., nitrogen in the form of nitrate and phosphorus in the form of phosphate) may pose treatment and disposal issues. Surface runoff from farms, for example, is a dispersed source of pollution, carrying animal wastes, fertilizers, pesticides, and silt into nearby streams (Inamori and Fujimoto). Proper wastewater treatment and dispersal is paramount to protecting the environment in which we live and the life-sustaining water that humans consume. A wastewater characterization study helps to set an overall approach to achieving compliance with regulations.

The quality of sewage can be checked and analyzed by studying and testing its physical, chemical and bacteriological (biological) characteristics as explained below:

Physical Characteristics of Wastewater

Turbidity

It is a measure of light transmitting properties of water (Spellman, 2013). Sewage is normally turbid representing dirty dish water or wastewater from baths having other floating matter like fecal matter, pieces of paper, cigarette ends, match sticks, greases, vegetable debris, fruit skins, soaps, etc. The turbidity depends on the quantity of solid matter present in suspension state. The turbidity can be determined by the turbidity rod or by turbidimeters. Turbidity is usually measured in nephelometric turbidity units (NTU) or Jackson turbidity units (JTLJ), depending on the method used for measurement. Higher turbidity increases water temperatures because suspended particles absorb more heat. This, in turn, reduces the concentration of dissolved oxygen (DO) because warm water holds less DO than cold. Higher turbidity also reduces the amount of light penetrating the water, which reduces photosynthesis and the production of DO (S.K Garg, 2009).

Color

The color of the sewage indicates the freshness of sewage. If its color is greyish brown or yellowish, it indicates fresh sewage. With passage of time, as putrefaction starts it begins to get black. The color of stale and septic sewage is black (When all the oxygen has disappeared from sewage, it becomes septic).Other colors may also be formed due to presence of some specific industrial waste. The color of the sewage can normally be detected by the naked eye.

True color is the measurement made following the removal of colloidal or suspended sources of turbidity. The term “apparent color” includes not only color due to substances in solution, but also that due to suspended matter. Apparent color is determined on the original sample without filtration or centrifugation. In some highly colored industrial wastewaters color is contributed principally by colloidal or suspended material. In such cases both true color and apparent color should be determined.

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