Wastewater Treatment and Disposal

Wastewater Treatment

• Wastewater treatment involves processes and mechanisms to treat contaminated water generated from residential or industrial areas.
• The main goal of wastewater treatment is to recycle or reuse the water, discharge it directly to the environment, or into a sanitary sewer.

Levels of Wastewater Treatment

• The selection of treatment processes occurs at the design stage and is based on hydraulic and pollutant loading, and the level of treatment required.
• There are preliminary, primary, secondary, tertiary, and advanced treatment levels.

Preliminary Treatment

• Preliminary treatment serves as a solid's separation phase prior to biological or chemical treatment technologies.
• It includes screening and grit removal to remove objects and insoluble particles that may damage downstream equipment and processes.
• Preliminary treatment also includes the control of incoming wastewater using flow splitters, overflow tanks, and balance tanks.

Water Treatment

• Water treatment is any process that improves the quality of water to make it suitable for a specific end-use.
• The end-use may be drinking, industrial water supply, irrigation, water recreation, or safely returning it to the environment.
• Water treatment removes contaminants and undesirable components, or reduces their concentration, to make the water fit for its desired end-use.

Drinking Water Treatment

Screening

• Screens are used to remove large floating and suspended solids present in the inflow to protect the main units of a treatment plant and aid in their efficient operation.

Aeration

• Aeration involves passing water over a series of steps to take in oxygen from the air, which helps expel soluble gases such as carbon dioxide and hydrogen sulfide, and removes iron and manganese by oxidation.

Coagulation and Flocculation

• Coagulation involves adding a chemical coagulant to neutralize the negative electrical charge of fine particles, allowing them to combine and form larger particles called flocs.

Sedimentation

• Sedimentation is a process where heavy or insoluble particles are collected and separated from the wastewater.
• The water is separated from the insoluble material when the insoluble material settles down at the bottom of the water.

Filtration

• Filtration is the process where solids are separated from a liquid by passing the water through sand and gravel beds.

Chlorination

• Chlorination involves disinfecting the water to eliminate any remaining pathogenic micro-organisms using chlorine as a disinfectant.

Biological Method of Wastewater Treatment

• Biological treatment involves the use of biological processes to break down organic matter like oils, human waste, soap, and food present in the wastewater.

Mechanical Methods of Wastewater Treatment

• Ceramic membrane technology uses ceramic membranes to filter wastewater.
• Sand filter technology is applicable where there are downward-flowing fluids driven by gravity or pressure.

Tertiary/Advanced Treatment Processes

• Tertiary treatment processes include sand filtration, ultraviolet disinfection, sludge treatment, chemical precipitation for phosphorus removal, and membrane filtration.

Methods of Wastewater Treatment

• There are four different wastewater treatment methods: physical, biological, chemical, and supplementary treatments.
• Each method has a different treatment process, and every treatment process must start with an assessment and evaluation.