What are the characteristic of sewage?
The classification of wastes is critical for a successful and cost-effective waste management programme. It aids in the selection of treatment methods, determining the scope of treatment, evaluating the beneficial applications of wastes, and strategically using the waste purification capability of natural bodies of water.
While a thorough examination of the wastewater in each case is recommended, data from other cities can be used in the early stages of planning. Domestic sewage is made up of waste water from the bathroom, kitchen, and lavatory, among other places. Daily per capita water use, quality of water supply, type, condition, and extent of sewerage system, and people's lifestyle are all elements that influence the characteristics of domestic sewage.
Municipal sewage, which includes both domestic and industrial wastewater, can vary based on the types of industries and industrial establishments in a given area. Here are some of the most important characteristics of sewage.
Characterization of Sewage/Factors Affecting its Composition -
1 Temperature: The temperature of sewage can be used to determine the solubility of oxygen, which influences the aeration equipment's transfer capacity and the rate of biological activity in aerobic systems. Extremely low temperatures have a negative impact on the efficacy of biological treatment systems and sedimentation.
In general, the temperature of raw sewage in India ranges from 15 to 35 degrees Celsius at various locations and times of year.
2 The pH: The hydrogen ion concentration, given as pH, is an important parameter in biological unit operation. The pH of the fresh sewage is somewhat higher than that of the community's drinking water. Decomposition of organic matter, on the other hand, can drop the pH, while industrial wastewater can cause significant fluctuations.
The pH of untreated sewage is usually between 5.5 and 8.0.
3 Colour and odour: Depending on the concentration, fresh residential sewage appears slightly soapy and hazy.
Due to microbial activity, sewage grows stale over time, darkening in colour and emitting a strong odour.
4 Solids: Although sewage typically comprises less than 0.5 percent solids, with the remainder being water, the inconvenience caused by solids should not be underestimated, as these solids are highly degradable and require careful disposal.
Dissolved solids, suspended solids, and volatile suspended solids are the three types of sewage solids. The assessment of organic and inorganic suspended solids provides an overall view of the load on the sedimentation and grit removal systems during sewage treatment. When sewage is used for land irrigation or any other reuse, the dissolved inorganic portion must be taken into account.
5 Chlorides: The concentration of chlorides in sewage exceeds the chloride content of drinking water. The amount of chloride in the sewage that exceeds the amount of water given, might be used as an indicator of the sewage's strength.
Chloride contributes roughly 8 gram per person per day on average.
6 Organic Material: Organic compounds found in sewage are of special interest to environmental engineers. A wide range of microbes interact with organic matter by utilising it as a source of energy or material.
Metabolism is the process through which microbes use organic matter. Catabolism is the conversion of organic material into energy by microorganisms, whereas anabolism is the incorporation of organic material into cellular material.
It is required to characterise quantitatively the concentration of organic matter in different forms in order to describe the metabolism of microorganisms and the oxidation of organic material. It is completely impractical to determine each individual organic compound in sewage due to the vast diversity of organic chemicals present.As a result, a parameter that characterises a property that all of these have in common must be employed.
7 Metals and compounds that are Toxic: Through industrial discharges, harmful heavy metals and compounds such as chromium, copper, and cyanide may find their way into municipal sewage. If the sewage is to be treated biologically or disposed of in a stream or on land, the concentration of these compounds is critical. These chemicals are generally safe in sanitary sewage, but they may exceed dangerous limits in municipal wastewaters if they receive industrial discharges.
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