There are 3 main characteristics of sewage as listed below.
- Physical Characteristics
- Chemical Characteristics
- Biological Characteristics
We will learn about these three characteristics of sewage in detail.
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Table of Contents
1. Physical Characteristics
(a) Smell
Fresh wastewater is virtually odorless. However, stagnant sewage stinks of hydrogen sulfide and other sulfur compounds produced by sewage decomposition. Odor is tested with an osmoscope.
(b) Specific Gravity
The specific gravity of sewage is almost the same as that of water
(c) Color
Fresh sewage is yellowish or gray or light brown. When the drainage reaches the putrefaction stage, it turns black or dark brown. The color of the sewage can usually be discerned by the eyes of the throat.
(d) Temperature
The sewage temperature is usually slightly higher than the water temperature. The average sewage temperature in India is 20 °C.
Temperature affects the bioactivity of bacteria present in wastewater. The biological activity in wastewater increases with increasing temperature. Temperature also affects the solubility of gases in wastewater. In addition, temperature also affects the viscosity of wastewater, which affects the sedimentation process during treatment.
(e) Turbidity
Wastewater is usually cloudy. Turbidity is directly related to the amount of suspended solids. Turbidity can be measured and confirmed with a turbidity bar or turbidity meter.
2. Chemical Characteristics
(a) Solid
Wastewater usually contains a very small amount of solids for a large amount of water. Contains only about 0.05-0.1% of total solids. Solids in wastewater can be in one of four forms:
- Suspended matter.
- Dissolved solids.
- Colloidal solid.
- Sedimentary solid.
It is estimated that approximately 1000 kg of wastewater contains approximately 0.45 kg of total solids, of which 0.225 kg is solution, 0.112 kg suspension and 0.112 kg sediment. Colloidal solids remain in solution or suspension. Additionally, solids in wastewater include both organic and inorganic solids. Organic materials make up about 45% of the total solids, with the remaining about 55% being inorganic materials. Distribution Solids in 1000 kg of wastewater may be present according to the diagram below.
The total amount of solids present in a given effluent can be determined by evaporating a known volume of effluent sample and weighing the remaining dry solids.
(b) pH
pH is defined as the logarithm of the reciprocal of the concentration of hydrogen ions present in water. Used to indicate the acidity and alkalinity of water.
So pH value – Log[H+]
Fresh sewage and treated sewage are alkaline in nature, and putrid sewage is acidic in nature. The pH of fresh wastewater is generally above 7 and that of putrid wastewater is below 7.
A potentiometer allows you to quickly and automatically measure the pH value.
(c) Chloride Content
Chlorides are generated from garbage, human waste, and industrial waste. The normal chloride content of domestic wastewater is 120 mg/L.
A high chloride content in wastewater indicates the presence of industrial wastewater or seawater intrusion.
Chloride content can be determined by titration with a silver nitrate standard solution using potassium chromate as an indicator.
(d) Nitrogen Content
The presence of nitrogen in wastewater indicates the presence of organic matter. It comes in one or more of the following formats:
- Free ammonia
- Albuminoid nitrogen
- Nitrite
- Nitrates
The presence of free ammonia marks the first step in the decomposition of organic matter. Albuminoid nitrogen indicates the amount of nitrogen present in the wastewater before organic matter begins to decompose.
Nitrite indicates the presence of partially decomposed organic matter. Nitrates indicate the presence of fully oxidized organic matter.
The amount of free ammonia in wastewater can be easily measured by simply boiling the ammonia gas and measuring it.
Albuminoid nitrogen content can be measured by adding a strong alkaline solution of potassium permanganate to a boiled wastewater sample and boiling it again. The amount of nitrite or nitrate present in a wastewater sample can be determined by a color comparison method.
(e) Dissolved Oxygen (DO)
It represents the amount of oxygen present in the wastewater in dissolved form. Wastewater usually does not contain dissolved oxygen. Its presence in raw sewage indicates that the sewage is fresh.
Its presence in the effluent after treatment indicates that significant oxidation was achieved by the effluent treatment process. Dissolved oxygen in fresh wastewater is temperature dependent. If the effluent temperature is high, the DO content will be low. The DO content of wastewater is commonly determined using the Winkler method.
3. Biological Characteristics
(a) Bacteria
Bacteria are microscopic single-celled organisms. There are the following types:
Pathogens: They are the cause of all water-borne diseases.
Non-pathogenic bacteria: They are harmless.
Aerobic bacteria: Helps decompose wastewater in oxidation ponds, lagoons, etc.
Anaerobes: Useful for decomposing sewage in tanks, cesspools, etc.
Optional Bacteria: There is no waste water treatment function.
(b) Microorganisms
Microorganisms such as algae, fungi, and protozoa support wastewater degradation processes through photosynthesis or decomposition of organic compounds.
FAQ
What Are 3 Characteristics Of Sewage?
Physical, chemical and biological are the 3 characteristics of sewage.