t hether each of the following statements are true or false

t hether each of the following statements are true or false: T F Stoke\'s Law can be used to model the oxygen sag curve T F Phosphorus is more often a limiting nutrient than nitrogen T F Hardness is more often a problem in surface water than in groundwater T F BODs measures CBOD, not NBOD T F The amount of available substrate will affect the biomass growth rate cons 2. [4 points] Lis t two advantages and two disadvantages of chlorination as a disinfection method. 3. [4 points] Explain the main advantage and disadvantage of combined sewer systems. secondary clarification in wastewater treatment. Consider removal mechanism(s) and the main constituent(s) to be removed. 4. [4 points) List one similarity and one difference between primary sedimentation and

Solution

2.

Advantages of Chlorination

- Residual chlorine helps in disinfection against further contamination throughout the flow of water through pipes and at the time of usage.

-relatively cheap ,simple,reiable and quick

Disadvantages of Chlorination

-imparts a peculiar taste to the water

-toxic to aquatic life

-chlorine is corosive

3.

Advantages

-stormwater and wastewater are managed together

-use of runoff for wastewater transportation is helpful in water conservation

-moderate costs

-health risk and insect problems are reduced by dilution of wastewater

Disadvantages

-Installation cost is high because of larger size sewers.

-Not suitable for areas of unpredictably varying storms.

-Larger sized and more efficient pump and pipe systems needed.

-Expertise is required for design.

4. Similarity- Sedimentation by gravity is used for settling of matter within a given settling time.

Difference: Primary clarifier mainly removes suspended impurities and in secondary clarifier microbes are removed by settlement.