Waste Treatment and Disposal

Question 1

Steps in the Primary Treatment of Waste

Answer 1

(Feed)> Screens > Grit Chamber > Sedimentation Tank

Sludge may or may not be sent to secondary treatment. If not, sludge goes to the digester then drying beds

Question 2

Steps in the Secondary Treatment of Waste

Answer 2

(From Sedimentation tank)> Aeration Tank > Final Sedimentation Tank (If not dry, recycle to aeration) > (May or may not be sent to disinfection tank, if not) > Digester> Drying bed

from sedimentation, if sent to disinfect, discharge is sent to rsurface water

Question 3

Physical Methods of Wastewater Treatment

Answer 3

1. Physical barriers (Screens, filters, barriers)
2. Plain Sedimentation (gravity)
3. Centrifugation (for grit and heavy solids)
4. Flotation
5. Adsorption
6. Ion Exchange
7. Stripping
8. Scrubbing

Question 4

Chemical Treatment Methods

Answer 4

1. Neutralization
2. Oxidation/Reduction
3. Chemical Precipitation
4. Coagulation
5. Chemical Extraction or Leaching
6. Ion Exchange

Question 5

Solid Waste Biological Treatment Methods

Answer 5

1. Aerobic
2. Anaerobic

Question 6

Process that involves decomposition of organic waste into humus known as compost which is a good fertilizer for plants

Answer 6

Composting

Question 7

Operator has control over the process. Type of composting that has no odor, short time needed. Not weather sensitive. Con’s include being costly and need of manpower.

Answer 7

In-vessel Composting

Question 8

Organic waste is placed into rows of long piles. Aerated by periodically turning the pile. 4-8ft high, 14-16ft width, applicable for large volume of diverse wastes

Answer 8

Windrow Composting

Question 9

Mixes organic waste in one large pile instead of rows. Layers of loosely piled bulking agents are included to ensure adequate oxygen flow. Can also use blowers for aeration. Applicable for homogeneous mix of organic waste.

Answer 9

Aerated Static Pile

Question 10

Products formed from anaerobic digestion

Answer 10

Biogas
digestate
Fertilizer

Question 11

Simplest digester. Operation consists of loading the digester with organic materials and allowing it to digest. Retention time depends on temperature and other factors

Answer 11

Batch Digester

Question 12

Organic material is continuously fed into the digester. produces biogas without interruption of loading

Answer 12

Continuous Digester.

Question 13

(Liquid Waste) Refers to a multi-chamber reactor unit that makes use of highly concentrated microorganisms to degrade organics and remove nutrients from wastewater to produce high quality effluent. Sewage is aerated in the aeration tank.

Answer 13

Activated Sludge Process

Question 14

Second commonly used type of aerobic treatment. Commonly used to remove compounds such as ammonia from the water after primary treatment

Answer 14

Trickling filters

Question 15

Treatment Pond that is provided with mechanical aeration that introduces oxygen into the pond in order to promote biological oxidation of the wastewater

Answer 15

Aerated Lagoon

Question 16

Ponds involve interaction between bacteria, algae, and other organisms which feed on the organic matter received from primary effluent. Slow process, requires huge land area.

Answer 16

Oxidation pond

Question 17

utilized to treat high strength waste water and employs organisms that function in the absence of oxygen.

Answer 17

Biological Anaerobic Treatment

Question 18

Aims to minimize the spread of pollution by converting the contaminated materials into solid impermeable mass with a low surface to volume ratio. Often achieved by adding a binder such as cement and quicklime to the waste material

Answer 18

Solidifaction

Question 19

Form of solidification where reagents are added which converts the contaminant to a less soluble form by chemical reaction or pH adjustment. The combined process of solidification are often termed–waste fixation or encapsulation

Answer 19

Stabilisation

Question 20

Used to immobilize a range of inorganic contaminants and some organic contaminants. Usually ex situ, may be described according to the chemical reagents used

Answer 20

S/S (Stabilisation and Solidification)

Question 21

Used to stabilize the contaminants in the waste

Answer 21

Binders

Question 22

Types of Binders

Answer 22

Inorganic
Organic

Question 23

Two principal types of this type of binder are cement binders and pozzolanic binders (lime, kiln, dust, fly ash, etc)

Answer 23

Inorganic Binders

Question 24

Used to solidify hazardous waste, stabilization is achieved by the formation of low solubility compounds

Answer 24

Cement Process

Question 25

Uses Pozzolan as principal binding agent, contains active silicates or aluminates which react with lime in the presence of water to form a stable material. Solidification depends on the formation of calcium silicate gels, which gradually harden over a period of time, relatively inexpensive

Answer 25

Pozzolan Process

Question 26

type of binder that is mainly used to solidify radioactive or hazardous organic wstes that cannot be destroyed thermally

Answer 26

Organic Binders

Question 27

Involves mixing waste with reactive monomers which join to form a solid incorporating the waste.

Answer 27

Thermosetting

Question 28

Involves bending with a polymer such as asphalt, polyethylene or other thermoplastic binders.

Answer 28

Thermoplastic

Question 29

Added to improve immobilisation of specific contaminants. Can also be incorporated to mitigate certain effects of inhibitors

Answer 29

Additives

Question 30

No chemical Interaction is needed between the soil contaminants and solidifying agents, results in monolithic mass, contaminants are held within the matrix by physical encapsulation

Answer 30

Solidification

Question 31

Use of chemical reagents which react with the soil contaminants and transform them into an immobile form. Does not necessarily lead to improved characteristics of soil

Answer 31

Stabilisation

Question 32

Fundamental mechanisms of stabilisation

Answer 32

Encapsulation
Absorption and Adsorption
Precipitation
Detoxification

Question 33

Contaminants are physically trapped in the pore spaces of the stablished materials

Answer 33

Encapsulation

Question 34

Electrochemical bonding between contaminants and agents in the solid matrix

Answer 34

Absorption and Adsorption

Question 35

Uses high temperatures to form a solid glassy monoliths mass from a contaminated soil. Inorganic materials incorporated into this ceramic-like matrix whilst organic compounds are destroyed in incineration.

Answer 35

Vitrification

Question 36

Refers to the processes that use heat to treat waste materials.

Answer 36

Thermal Waste Treatment

Question 37

commonly used thermal waste treatment techniques

Answer 37

Incineration
Gasification and Pyrolysis
Open Burning
In Situ Thermal Treatment

Question 38

One of the most common thermal waste treatment methods, involves combustion of waste in the presence of oxygen. Converts waste into ash, flue gas, water vapor and carbon dioxide. Reduced waste volume

Answer 38

Incineration

Question 39

Two similar thermal treatment method in which organic waste is decomposed by exposing waste to low amounts of oxygen and high temperature.

Answer 39

Pyrolysis and Gasification

Question 40

A legacy thermal waste treatment that is environmentally harmful

Answer 40

Open burning

Question 41

Method of thermal treatment that moves or mobilizes harmful chemicals in soil and groundwater using heat.

Answer 41

In Situ Thermal Treatment