Wastewater Treatment and Oxygen Demand

Study Notes

Measures the pollution potential of organic matter present in a sample.
Indicates the amount of oxygen required to oxidize the organic matter in a water sample.
Uses potassium dichromate (K2Cr2O7) as the oxidant.
Expressed in milligrams per liter (mg/L) of oxygen equivalent.

Measures the amount of oxygen consumed by microorganisms during the decomposition of organic matter.
Indicates the biodegradable organic matter present in a sample.
BOD5 is the standard test, carried out over 5 days at 20°C.
The BOD test is based on the principle that aerobic microorganisms will continue to oxidize organic matter as long as oxygen is available.

Primary treatment: Removes solids through physical processes like screening and sedimentation.
Secondary treatment: Removes organic matter using biological and chemical processes.
Tertiary treatment: Removes nutrients like phosphorus and nitrogen through biological and chemical processes.

This process is commonly used for secondary wastewater treatment.
Aerobic bacteria are used to break down organic matter.
Wastewater is mixed with activated sludge (a suspension of microorganisms) in an aeration tank.
The mixture is continuously aerated, promoting the growth of bacteria.
Wastewater then flows into a secondary settling tank where the bacteria-laden sludge is removed.
The sludge is recycled to the aeration tank to maintain a sufficient biomass for efficient treatment.

An aerobic attached growth type wastewater treatment system.
Wastewater trickles through a bed of media (stones or plastic) covered in bacteria.
The bacteria break down organic matter and remove pollutants from the wastewater.
The system utilizes a rotating distributor to evenly distribute wastewater across the bed.

A combination of suspended growth and attached growth processes.
Anaerobic microorganisms grow on the surface of the media, expanding the apparent volume of the medium.
Also known as an "expanded bed reactor".

The partial destruction of disease-causing (pathogenic) organisms in wastewater.
Aims to reduce the risk of waterborne illnesses.
Ideal disinfectants possess characteristics like:
- Availability
- Deodorizing ability
- Homogeneity
- Non-corrosive and non-staining
- Toxic to microbes
- Penetration
- Solubility and stability

Chemical: Halogens (chlorine), Ozone, Phenolics, Alcohols, Metals, Detergents
Physical: Heating, Solar insolation
Mechanical: Chemical precipitators and biofilters
Radiation: Gamma radiation and Cobalt-60 radiation