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Chapter: Civil : Environmental Engineering : Planning For Sewerage Systems

Important Question And Answer: Planning For Sewarage Systems

Important Question And Answer: Planning For Sewarage Systems

Important Question And Answer: Planning For Sewarage Systems



1.What are the types of treatment processes?



        Preliminary treatment


        Primary treatment


        Complete final treatment


        Secondary treatment


2. What are the various sources of wastewater generation?



        Industrial Wastes


        Domestic wastes


        Agricultural  Wastes


3.  List out the types of anaerobic biological units?



        Anaerobic lagoons


        Septic tank


        Inhoff tank



4.  What is means by screening?


Screening is the very first operation carried out at a sewage treatment plant and consists of passing the sewage through different types of screens so as to trap and remove the floating matter such as process of cloth, paper, wood, cork, hair, fiber etc.



5. What is the purpose of providing screen?


The main idea of providing screens is to protect the pumps and other equipments from the possible damages due to the floating matter of the sewage.It should be used for removing the floating matters.

6. What are the types of screen?


Classification based on size of the opening


        Coarse screens


        Medium screens


        Fine screens



7. Define bar screen?


Rectangular shaped coarse and medium screens are made of steel bars fixed parallel to one another at desired spacing on a rectangular frame and are called bar screen.



8. Define Communicators?


Comminutes or shredders are the patented devices, which break the larger sewage solids to about 6 mm in size. When the sewage is screened through them such devices are used only in developed countries like USA.



9. What is meant by Screening?


The material separated by screens is called the screenings. It contains 85 to 90% of mixture and other floating matter. It may also contain some organic load which may putrefy, lacing bad smells and nuisance.



10.            What are the methods adopted for disposal of screenings?









11.              Define Grit Chamber?


Grit chambers, also called or grit channels or grit basins, are intended to remove the inorganic particles (specific graving about 2.65) such as sand, graver, grit, egg, shells, bones etc of size 2 mm or larger to prevent damager to the pumps and to prevent their accumulation in sludge digesters.



12. Define unit process?


Methods of treatment in which the application of physical forces predominate are known as unit operations while methods of treatment in which chemical or biological activities are involved are known as unit process.

13. What are the types of unit operations & processes?


Physical unit operations


Chemical unit process


Biological unit process



14.Give any two advantages of unit operations/ process?


        It gives better understanding of the process as inherent in the treatment and of the capabilities of these processes in attaining the objectives.


        It helps in the development of mathematical and physical models of treatment mechanisms and the consequent design of treatment plants.



15.Define phase transfer?


Most waste water treatment process bring about changes on concentration of a specific substances by moving the substance either into or unit of the waste water it self. This is called phase transfer


16. Define definition time?


The definition time (t) of a settling tank may be defined as the average theoretical time required for the sewage to flow through the tank. Otherwise known as definition period or retention period



17. Define the term Displacement efficiency?


The                ratio    of   ughthe   period''Flowing tothrothe    'detention


displacement efficiency.



18. What is meant by principle of sedimentation?


The turbulence is retarded by offering storage to sewage these impurities tend to settle down at the bottom of the tank offering such storage. This is the principle of sedimentation.



19.   Define   the   term   'Sedimentation   Burin'?


The  burin  in  which  the flow  of  sewage  is  retarded  is  called  the  settling tank  or  the


sedimentation Tank or the sedimentation Burin.



20.   Define   the   term   'Detention   Period'?


The theoretical average time for which the water is detained is called the detention period.

21. Give any two advantage of chemical coagulation process in sewage treatment?


Sedimentation aided with coagulation produces better efficient with lesser BOD and suspended solids, as compared to plain sedimentation. Coagulated settling tank requires less space than that required by an ordinary plain settling tank.





22.What are the Demerits of coagulation in sewage treatment?


Cost of chemicals is added to the cost of sedimentation, with out much use, and thereby making the treatment costlier.


        The process of coagulation requires skilled supervision and handling of chemicals.



23.                  What are the types of sedimentation tank?


Based on flow


        Vertical flow tank


        Horizontal flow tank


        Radial flow tank


According to use







24.What are the chemical used for precipitation of sediment?




Ferrous sulphate


Ferric sulphate


Ferric chlorides


Sodium alluminate


Sulphuric acid






25.What are the factors that affect the precipitations?


        Kind of chemical


        Quality of chemical


        character and concentration of sewage


        Ph values of sewage


        time of mixing and flowlations




        Violence of agitation


26.What are the merits of chemical precipitation?



           More rapid and through clarification


           Removal of higher percentage of suspended solids.


           Simplicity of operation


           Small size tank is enough




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