Sewage Processing & Disposal 12-2

Question 1

Definition of sewage

Answer 1

Sewage is the waste & wastewater produced by residential & commercial sources that is discharged into sewers.

Question 2

History of Sewage Disposal

Answer 2

The Minoan culture of Creta had an advanced sewage management system.
-Romans constructed a sewage system & aqueducts.

Question 3

Sewage Processing & Disposal

Answer 3

Sewage includes wastewater that is generated by people in homes & businesses, which are conveyed by sewer pipes to sewage treatment plants.
-Sewage is treated with chemicals & bacteria to produce clean water, which is then returned to rivers or ponds.
~Modern technology involves: 1) removing solids
2) Deactivating bacteria
3) Producing wastewater that can be returned safely to waterways or in some cases can be reused or recycled.

Question 4

Continued sewage processing & disposal:

Answer 4

When bacteria act upon the organic matter in sewage or certain industrial wastes that are discharged into waterways, large amounts of dissolved oxygen are rapidly used up. (resulting in fish death & other alterations in the aquatic environment).

The most used measurement of the amount of organic material polluting water is a parameter referred to as a Biochemical Oxygen Demand (BOD).

Question 5

What is BOD (Biochemical Oxygen Demand)?

Answer 5

BOD, is the amount of dissolved oxygen used by microorganisms during the oxidation of organic matter.

Is an indication of how much putrescible organic material is present

Question 6

Process of Sewage Treatment: Primary Stage

Answer 6

During the primary stage of sewage treatment, ~60-65% of suspended solids are removed & BOD is reduced ~25-40%.

Large materials removed may be composted or shipped to landfills.

Question 7

Process of Sewage Treatment: Secondary Stage

Answer 7

The secondary stage of sewage treatment promotes bacteria digestion of the organic material.
~Uses microorganisms naturally present in sewage or other microorganisms (protozoans, nematodes) to enhance organic digestion**

Question 8

Tertiary Treatment

Answer 8

-Chemical coagulation-flocculation, by adding polymers (neutralize of charge) induce aggregation of small particles together into large aggregates, making easier separation from water. Also, removes phosphates.

• Activated carbon, activates carbon generating small, low volume pores to increase adsorption of particles like synthetics, chemicals, or bad odors.