sewage treatment plant

INTRODUCTION

Sewage -general considerations

It is the technique of removing harmful impurities from wastewater and household waste waters, both runoff (effluents) and domestic. This process involves physical, chemical, and biological processes to remove all types of contaminants. Its objective is to zero liquid discharge and provide useful fresh water in the environment. The sewage water is often adversely contaminated with many toxic organic and inorganic compounds.

sewage treatment plant (Project picture)

Sewage can be defined as the wastewater that is collected form some area and then conveyed to some point of disposal. The liquid wastes will require treatment before they are discharged into the water body or otherwise disposed of without endangering the public health or causing offensive conditions.

With the growth of population and the modern cities the conventional method of wastewater disposal has been replaced by the planed water-carried sewage system. Even in the small cities the greater safety of sewerage, its convenience, and freedom from nuisance have caused it to be adopted wherever finances permit.

Definitions:

Sewage: It may be defined as unwanted or undesirable matter either in solid, semi solid or liquid form. The dry wastes are garbage, ashes etc. In other words, the waste which contains suspended, colloidal and dissolved solids, is called sewage.

Sullage: The liquid waste form kitchens, bathrooms and wash-basins are called as sullage. So it is a type of sewage in a very wet condition

Storm water: It is the liquid flowing in sewage during the rainy season or after a period of rainfall is known as storm water

Combined system: A combined system sanitary sewage and storm water in combined form are carried in a single sewer. So only one set of sewers is laid for carrying both i.e. storm Water as well as sanitary

Separate system: A separate sewage system two set of sewers are laid. One for carrying sanitary sewage and the other for carrying storm water. So the storm water is discharged directly into the natural stream or river whereas the sanitary sewage is carried to the treatment plant for further treatment.

Partially separate system: A partially separate sewage system, the storm water within permissible limits disposed off along with sanitary sewage through the sewer. The excess quantity of storm water is collected and conveyed separately. So the remaining portion of storm water is diverted into a separated set of sewers or stream.

Sewer: An underground pipe or conduit which is used to carrying sewage is known as sewer

Sanitary sewer: The sewers which carry sanitary sewage and excludes all other types of sewage like storm sewage, surface water and ground water is called as sanitary sewers

Sewerage: the various pipe are used to carry sewage. The network of sewers or pipe used for transporting the sewage is called sewerage.

Dry weather flow: The normal flow in a sewer during a dry weather is known as Dry weather flow (D.W.F.)

Dilute sewage: The sewage which contain less than 150 ppm of suspended solids and B.O.D. is called dilute sewage. It includes animal dung and horse drooping but they are less foul in nature and so does not create bed smell.

Fresh sewage: The sewage which contains dissolved oxygen (D.O.) at the point of treatment is called fresh sewage.

Septic sewage: The sewage which is under the treatment process is known as septic sewage

Per capita demand: Per capita demand may be defined as total yearly consumption of water for water supply scheme divided by the population of that area and the number of days in a year’s

Advantages/Disadvantages

Advantages

•          Eliminates 97% percent of solid waste
•          Helps in improving public health and environment
•          Helps natural nitrification without the need of chemicals
•          Oxidation and nitration achieved
•          Biological phosphorous removal
•          Solids and liquids separation
•          Removes organics
•          Cost effective
•          Easily to maintained mechanical work
•          Self-sustaining system

Disadvantages

•          Cleaning is a hassle
•          Most plants need at least three tanks
•          Temperature changes affect the tank greatly
•          This type of plant requires a big area to be build.