Water Quality Analysis and Pesticides

Flashcards covering key concepts in water quality analysis, particularly BOD, COD, organochlorine compounds, and their environmental impact.

What are the two types of BOD contributions in water samples?

Carbonaceous BOD (C-BOD) and Nitrogenous BOD (N-BOD).

What is the primary reaction involved in measuring C-BOD?

The oxidation of reduced carbon in organic matter: CH2O + O2 → CO2 + H2O.

What are nitrifying bacteria responsible for in the context of N-BOD?

They catalyze the oxidation of the reduced nitrogen component of organic matter through nitrification.

Why is only C-BOD measured during the initial days of wastewater treatment?

The populations of nitrifying bacteria are insufficient to produce measurable N-BOD.

What is the primary purpose of Chemical Oxygen Demand (COD) testing?

To approximate the BOD of a water sample using a strong oxidizing agent.

What is the oxidizing agent commonly used in COD testing?

Dichromate (Cr2O7 2-).

What is the half-reaction for the reduction of dichromate?

Cr2O7 2− + 14 H+ + 6 e− → 2 Cr3+ + 7 H2O.

What is the relationship between the oxidizing capacity of dichromate and oxygen?

A dichromate ion has 1.5 times the oxidizing capacity of a molecule of oxygen.

What are organochlorine compounds?

Organic compounds that contain at least one chlorine atom covalently bonded to carbon.

What is a pesticide?

Any compound that can directly kill an unwanted organism.

What is the main concern regarding organochlorines in the environment?

Their stability and bioaccumulation in the food chain.

What does bioconcentration refer to?

The increase in the concentration of a chemical in a biological organism over time.

How is the bioaccumulation factor (BCF) measured?

By the ratio of the concentration of the chemical in the fatty tissue of an organism to the concentration in surrounding water.

What is the octanol-water partition coefficient (Kow)?

The equilibrium constant representing the ratio of solute concentrations in octanol and water.

What is the significance of a high Kow value?

It indicates a compound's potential for bioaccumulation in living organisms.