CHARACTERISTICS OF DOMESTIC WASTEWATER

Physically, domestic wastewater is usually characterised by a grey colour, musty odour and has a solids content of about 0.1%. The solid material is a mixture of faeces, food particles, toilet paper, grease, oil, soap, salts, metals, detergents, sand and grit.

Characteristics of Wastewater 

The three main characteristics of wastewater are classified below. 

1. Physical Characteristics 

· Turbidity 

· Color 

· Odor 

· Total solids 

· Temperature 

2. Chemical Characteristics due to Chemical Impurities 

· Chemical Oxygen Demand (COD) 

· Total Organic Carbon (TOC) 

· Nitrogen 

· Phosphorus 

· Chlorides 

· Sulfates 

· Alkalinity 

· pH 

· Heavy Metals 

· Trace Elements 

· Priority Pollutants 

3. Biological Characteristics due to Contaminants 

· Biochemical Oxygen Demand (BOD) 

· Oxygen required for nitrification 

· Microbial population . 

Physical Characteristics of Wastewater 

· Color - 

Fresh sewage is normally brown and yellowish in color but over time becomes black in color. 

· Odor –

 Wastewater that includes sewage typically develops a strong odor. 

· Temperature -

 Due to more biological activity, wastewater will have a higher temperature. 

· Turbidity - 

Due to suspended solids in wastewater, wastewater will have a higher turbidity, or cloudiness. 

Chemical Characteristics of Wastewater ; 

Wastewater contains different chemicals in various forms as mentioned below. 

 Chemical Oxygen Demand (COD) - 

COD is a measure of organic materials in wastewater in terms of the oxygen required to oxidize the organic materials. 

· Total Organic Carbon (TOC) -

 TOC is a measure of carbon within organic materials.

Nitrogen -

 Organic nitrogen is the amount of nitrogen present in organic compounds. 

Phosphorous - 

Organic phosphorous (in protein) and inorganic phosphorous (phosphates, PO4- ) 

· Chlorides (Cl-) 

· Sulfates (SO4-2) 

· Heavy metals 

Mercury (Hg) 

Arsenic (As) 

Lead (Pb) 

Zinc (Zn) 

Cadmium (Cd) 

Copper (Cu) 

Nickel (Ni) 

Chromium (Cr) 

Silver (Ag) 

Biological Characteristics of Wastewater ; 

Biochemical Oxygen Demand (BOD) - 

BOD is the amount of oxygen needed to stabilize organic matter using microorganisms. 

Nitrogenous Oxygen Demand (NOD) - 

 NOD is the amount of oxygen needed to convert organic and ammonia nitrogen into nitrates by nitrifying bacteria. 

Microbial life in wastewater - 

Wastewater contains the following microbes: 

 Bacteria , 

 Protozoa , 

 Fungi , 

 Viruses , 

 Algae , 

 Rotifers , 

Nematodes , 

Oil and Grease - 

Oil and grease originate from food waste and petroleum products. The amount of oil and grease in raw wastewater varies from 10 to 109 mg/L. 

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