Posted: September 13th, 2017

Water Treatment Plant Design

Paper, Order, or Assignment Requirements

 

 

4 calculation questions outta which question number 2&4 needs to be solved only using a software called AQUASIM. question 1 is kinda big as we need to find Coagulation, Rapid-Mix, Flocculation, Sedimentation, Filtration and Disinfection. 3 graphs are required for SEDIMENTATION and 2 for COAGULATION. I have further attached the tables and values for your perusal.

 

Assignment 1: Water Treatment Plant Design

 

Instructions: Total points 35 for the assignment.

 

A newly formed city wants to construct a drinking water treatment plant and distribution system. Design capacity of the treatment plant is 1+0.2* (the last digit of student ID whichis 5 )m³/s, with an initial demand expected to be only half the design capacity. First customer is expected to receive water after 24 hr of disinfection and customer at the end of treatment system is expected to be around 3 days after the disinfection. Consider chlorine as disinfectant.

 

1. Design coagulation, flocculation, sedimentation, rapid sand filtration, and disinfection facilities.
2. Using the data on enhanced coagulation (Table 2), propose modification to the design necessary to meet the new regulation that will be specifying a maximum 80 and 60 ppb of TTHM and HAA5, respectively.
3. If customers are neither expected to receive more than 0.6 mg/L nor less than 0.2 mg/L of chlorine (aesthetic requirement), how do you think you would meet this condition?
4. Calculate the CT value achieved by your dosing and compare with the table of values given in the lecture notes to understand whether the CT value is met by your dosing.

 

DATA

 

Source water quality:

Water temperature = 12 – 24^oC

Ca²⁺ – 95.20

Mg²⁺ – 13.44

Na⁺ – 25.76

CO₂ – 19.36

HCO₃^– – 241.46

SO₄^2- – 53.77

Cl^– – 67.81

DOC – 4.5 mg/L

Turbidity – 15

Total Coliforms = 10000 /100mL

Giardia = 20/L

 

 

A jar test conducted to understand the turbidity removal characteristics when turbidity was at 15 NTU showed the performance shown in Table 1.

 

Table 1

	1	2	3	4	5	6
pH Fe dose (mg/L) Settled water turbidity (NTU)	5.0 10 11	5.5 10 7	6.0 10 5.5	6.5 10 5.7	7.0 10 8	7.5 10 13

 

	1	2	3	4	5	6
pH Fe dose (mg/L) Settled water turbidity (NTU)	6.0 5.0 14	6.0 7 9.5	6.0 10 5.0	6.0 12 4.5	6.0 15 6.0	6.5 20 13

 

 

According to mEnCo program following final DOC was obtained at given doses for the water. Suggest how you would treat water by enhanced coagulation (i.e. define dose and pH) to get the final DOC necessary to achieve regulatory DBP requirements.

 

 

 

Assume the settlement characteristics of flocs is similar to that in Table 3.

 

Table 3: Results of laboratory flocculation tests. Initial sediment concentration was 20 mg/L. Table lists the concentration measured at each point at different time.

  Depth, m	Sampling Time, min
	10	25	40	55	70	85
0.5 1.0 1.5 2.0 2.5	14.0 15.0 15.4 16.0 17.0	10.0 13.0 14.2 14.6 15.0	7.0 10.6 12.0 12.6 13.0	6.2 8.2 10.0 11.0 11.4	5.0 7.0 7.8 9.0 10.0	4.0 6.0 7.0 8.0 8.8

 

 

 

 

 

 

Filter bed is to be designed using the sand with the characteristics given in Table 4.

 

Table 4: Filter bed material characteristics.

US Standard Sieve No	Mass percent retained
8 12 16 20 30 40 50 70 100	0.03 0.05 0.32 6.70 22.90 43.00 23.20 3.70 0.10

 

Make reasonable assumptions as done in the examples. While the complete filter bed should cater for future demand (the capacity), it should have the capability to handle the current demand by having few filters offline. Depth can be assumed to be 0.75 m, specific gravity of sand is 2.80, shape factor is 0.91, and specific porosity is 0.40.

Mainly carry out calculation of head loss of the clean bed, expanded bed, number of beds, width x length etc. Indicate the position(s) of various elements of the filter bed.

 

Chlorine decay characteristics usually follow parallel second order (Fisher et al., 2011).

 

Reaction rate = k_F*F*Cl + k_S*S*Cl

k_F, k_S are reaction rates of fast and slow reacting agents. F and S are concentrations of fast and slow reacting agents.

The reaction rate, k_T, at any temperature (T^oC) can be described as

k_T= k₂₀*exp[-E/R(1/(273+T)-1/(273+20)].

where k₂₀ is the reaction rate coefficient at 20^oC.

 

Assume that initial fast and slow decaying agents are 0.255*DOC-0.0307 and 4.582*DOC-5.602 mg/L. Fast and slow decay rate constants at 20^oC are 2, 0.002 hr^-1.mg^-2.L². The E/R value is found to be 7000 K^-1.

 

TTHM and HAA5 formation characteristics are given as 25+5*(remainder if ID is divided by 5) and 10 +3*(remainder if ID is divided by 5) mg/mg chlorine reacted respectively. The last customer is located 3 days from the initial chlorine dosing. The final chlorine concentration has to be at least 0.2 mg/L. Assume the water is spending all three days in the pipeline.

 

Aesthetic consideration demands the chlorine levels to be maintained below 0.6 mg/L.

Hint: Use aquasim to simulate the chlorine decay and THM formation characteristics.