Reference no: EM132416453

Water Treatment Homework

Question 1. Define the meaning of the term pathogen and give the names of pathogen groups. What determines the kinds and concentrations of pathogens in wastewater? Define the meaning of fecal-oral route in the transmission of diseases.

Question 2. Historically in the United States, the prevalent infectious diseases have been typhoid, cholera, and dysentery. How have these diseases been virtually eliminated? Currently, the prevalent infectious diseases are giardiasis and cryptosporidiois, causing diarrhea that can be life-threatening for persons with immunodeficiency syndrome. What actions are being taken to reduce the probability of waterborne transmission of these diseases?

Question 3. Why can coliform bacteria be used as indicators of drinking water quality? Discuss the limitations of coliforms as an indicator.

Question 4. What are the significant differences between Escherichia coli and Escherichia coli O157:H7?

Question 5. Discuss the source of lead in drinking water.

Question 6. What defined the meaning of the term C⋅t product. With reference to Table 11.6, what kind of microorganism is most readily inactivated by free chlorine? What kind is the most difficult to inactivate? What are the most and least effective disinfectants for inactivating E. coli? (After 11.39, Viessman and Hammer, 1998)

Question 7. What is the MCL for disinfection by-products? What is their source in drinking water?

Question 8. Why are iron and manganese included in secondary standards for aesthetics in drinking water?

Question 9. Why is there a standard for turbidity?

Question 10. Cooper et al., 2000 problems 6.17, 6.20 (W=2.25 ft, L=2.25 ft, D=2.83 ft, HRT=37 sec), 6.21, 6.22 (HRT=3.10 hr, Q/A = 694 GPD/ft²), and 6.23.

Question 11. If a jar test demonstrates that the optimum dosage for coagulation is 25 ppm Al³+, how many pounds per day of alum (Al₂(SO₄)₃·14 H₂O) are required for a 45 MGD water treatment plant? 103,000 lbs/day

Question 12. If 130 mg/L of bulk ferric sulfate (18.5 % Fe(III) by weight) is required for coagulation, how much alkalinity (mg/L as CaCO₃) is destroyed if there are three equivalents per mole of Fe(III) in the reaction? 65 mg/L as CaCO₃

Question 13. Define the meanings of the terms coagulation and flocculation in reference to destabilization of colloidal suspensions. When these terms are used by an environmental engineer in reference to water treatment processes, what are their meanings? (Viesmann and Hammer 11.12).

Question 14. Assuming the rate of kill of organisms follows Chick’s Law

dN/dt = - kCN

where N is the concentration of organisms at time t, C is the disinfectant concentration, and k is the rate constant,

a. Calculate the total CSTR tank volume required for a 99.9% kill of enteric viruses if k = 4 L/mg/min, C = 0.2 mg/L and the flow rate Q = 1000 gal/min. 1.26 x 10⁶ gallons.

b. Calculate the time required to achieve the same results in a batch reactor. 8.6 min.