Waste Treatment and Disposal Flashcards
Steps in the Primary Treatment of Waste
(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
Steps in the Secondary Treatment of Waste
(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
Physical Methods of Wastewater Treatment
- Physical barriers (Screens, filters, barriers)
- Plain Sedimentation (gravity)
- Centrifugation (for grit and heavy solids)
- Flotation
- Adsorption
- Ion Exchange
- Stripping
- Scrubbing
Chemical Treatment Methods
- Neutralization
- Oxidation/Reduction
- Chemical Precipitation
- Coagulation
- Chemical Extraction or Leaching
- Ion Exchange
Solid Waste Biological Treatment Methods
- Aerobic
- Anaerobic
Process that involves decomposition of organic waste into humus known as compost which is a good fertilizer for plants
Composting
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.
In-vessel Composting
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
Windrow Composting
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.
Aerated Static Pile
Products formed from anaerobic digestion
Biogas
digestate
Fertilizer
Simplest digester. Operation consists of loading the digester with organic materials and allowing it to digest. Retention time depends on temperature and other factors
Batch Digester
Organic material is continuously fed into the digester. produces biogas without interruption of loading
Continuous Digester.
(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.
Activated Sludge Process
Second commonly used type of aerobic treatment. Commonly used to remove compounds such as ammonia from the water after primary treatment
Trickling filters
Treatment Pond that is provided with mechanical aeration that introduces oxygen into the pond in order to promote biological oxidation of the wastewater
Aerated Lagoon
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.
Oxidation pond
utilized to treat high strength waste water and employs organisms that function in the absence of oxygen.
Biological Anaerobic Treatment
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
Solidifaction
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
Stabilisation
Used to immobilize a range of inorganic contaminants and some organic contaminants. Usually ex situ, may be described according to the chemical reagents used
S/S (Stabilisation and Solidification)
Used to stabilize the contaminants in the waste
Binders
Types of Binders
Inorganic
Organic
Two principal types of this type of binder are cement binders and pozzolanic binders (lime, kiln, dust, fly ash, etc)
Inorganic Binders
Used to solidify hazardous waste, stabilization is achieved by the formation of low solubility compounds
Cement Process
