Question

Q.

(a)  What is the significance of different Stages of Sewage Treatment Processes? As a Plant Manager, what factors you would consider important in decision making regarding selection of any or more of these Stages?   

(b) What criteria are used in checking Process Efficiency of an Activated Sludge Process? Explain your understanding of SVI Index.

Answer 1

ANSWER -

SWEAGE TREATMENT PROCESS -

it is a process of removing contaminants from wastewater and household sweage, both effluents and domestic. it includes physical and chemical and biological processes, for remvoing physical, chemical and biological contaminants.

it involves three stages -

primary stage

secondary stage

and tertiary stage

in primary stage, it have three stages, SCREEN, GRIT CHAMBER AND CLARIFIERS. they remove large suspended and floating material, grit and silt sand heavy material respectiviely.

in chemical treatment, chemical reacctors are used to purify dissolved chemcials.

then, in biological treatment, trickling filters, activated sludge, rotating biological contactors are used to purify dissolved organic chemicals.

primary treatment removes materials like trash, tree limbs leaves branches , also the settled and floated materials are removed, like cans rags sticks plastic packets,

in secondary treatment, the suspended biological matter is removed, typically performed by water borne micro organisms in a managed habitat. there are trickling filters , rotating biological contractors and other equipnments to remove the biological waste.

in secondary treatment, filteration and chlorination also takes place. also activated sludge is present in huge amount which biologically kills the mircro organisms present in the waste.

in the end in tertiary stage, a final screening is carried out , by purifying and filtering it again and again and then is taken in use.

b) process efficiency of activated sludge can be carried out by the process of removal of microorganisms. in this process fresh air is provided to the waste which results into production of new organisms, carbon dioxide and oxidation of the sweage. this is how basics of activated sludge efficiency.

the activated sludge efficiency is somewhat ranges from 59percent to 81 percent in various tanks.

SVI INDEX - sludge volume index is a process of find the settling percentage of the sludge in the activated sludge tank. it is a controlled process of determining the activated sludge of the tank.

it is calculated by dividing the seatability by the MLSS concentration. its units are in mL/g

MLSS - mixed liquid suspended solids, it si the concentration of solids in the suspended tank.