Lesson 5 - Effluent Treatment SAQ
This lesson allows you to test yourself on the material covered in the Effluent Treatment lesson and determine the level to which you have met the learning outcomes.
Suggested Response - Q1
* Explain the differences between the following:
a) COD and BOD
b) Aerobic and anaerobic processes
c) Effluent balancing and pH control of effluent
Response:
a) The chemical oxygen demand (COD) measures the theoretical amount of oxygen required to break down biological matter to a level acceptable for discharge.
The biological oxygen demand (BOD) measures the amount of oxygen required by micro-organisms to digest the most readily available nutrients present in the effluent. The amount of oxygen consumed is measured over a five-day period. The test is thus known as BOD 5. This value is usually lower than the COD, and the difference indicates the ease/difficulty of digestion.
b) Aerobic processes use aerobic microorganisms that use oxygen to convert the biomass into CO2, water, and a growth in the aerobic biomass.
Anaerobic processes use anaerobic microorganisms that convert the biomass into methane, CO2, and anaerobic biomass.
c) Balancing is the process of collecting effluent from different sources over a period of time to ensure it provides a relatively consistent stream to the effluent treatment process. pH adjustment ensures that the effluent pH is optimal for the downstream treatment processes by adding caustic or acid to the effluent.