Water Polishing Treatment System by pengxuebo


									Water Polishing Treatment System for Carnegie Mellon University Department of
                    Civil and Environmental Engineering

                                                                   July 18, 2006
                                                                   Heather Coile
                                                        Advised by Dr. Dzombak
                                             Civil and Environmental Engineering
                                                     Carnegie Mellon University

The purpose of this project was to design a drinking water polishing treatment system for
the Civil and Environmental Engineering (CEE) department, of Carnegie Mellon
University. Water tests were conducted to determine the existing quality of tap water in
the CEE department lounge, and what type of treatment would be necessary. These water
tests showed that the amount of chlorine, total organic carbon, and total suspended solids
were at levels sufficient to affect water taste. The Aquasana AQ-4000 filtration and
absorption treatment system was chosen to remove chlorine, TOC, and TSS. The
Aquasana AQ-4000 has a treatment capacity of 30 gallons per hour. A taste test and a
survey on usage were also conducted. From these investigations it was determined that a
chilling and heating unit for the treated water would also be necessary. The Elkay ERS1
water chiller was selected and the Quick and Hot heating unit was chosen. A treatment
system installation plan for the CEE lounge was developed in which the equipment is
made visible for educational purposes. Content for signage to be installed with the
equipment was also developed.

This project examined the cost, feasibility, design, and operation of a drinking water
polishing treatment system for the Carnegie Mellon Civil and Environmental Engineering
Department (CEE). A treatment system was designed based on analysis of the current
set-up, water quality, use and projected use, and user requests.


Time series tests were conducted on the tap water from the sink in the CEE lounge. The
tests performed were: three chlorine tests, one total solids (TS) test, one total organic
carbon (TOC) test, one total dissolved solids (TDS) test, one total suspended solids (TSS)
test, one turbidity test, and one total iron test.

The residual chlorine tests were taken at different days of the week and times of the day.
Chlorine test one was conducted Thursday, February 9, 2006, 3:30-5:30pm; chlorine test
two was conducted Monday, February 13, 2006, 1:45-3:15pm; and the final chlorine test
was conducted Wednesday, March 1, 2006, 9:00-10:30pm. Results of the water quality
tests are presented in Figures 1-3. The measured residual chlorine, particularly in the test
conducted at 9:00 pm, was high, with readings greater than 2.5 mg/L. The elevated
chlorine does not cause any adverse health affects but does negatively affect the taste.
Chlorine levels over 2mg/L are said to give the water questionable odor and taste
(reference, 2006).

  Chlorine (mg/L)

              0           20            40           60         80           100
                                          Time (min)

Figure 1 Free Residual Chlorine in CEE Lounge, Tap Water vs Time. Test 1, February 9,
2006, 3:30-5:30pm.

 Chlorine (mg/L)






             0       20          40       60            80         100
                                  Time (min)

Figure 2 Free Residual Chlorine in CEE Lounge, Tap Water vs Time. Test 2, February
13, 2006, 1:45-3:15 pm.

   Chlorine (mg/L)

            0         20           40       60              80           100
                                    Time (min)

Figure 3 Free Residual Chlorine in CEE Lounge, Tap Water vs Time. Test 3, March 1,
2006, 9:00-10:30pm.

As seen in Figure 4, the measured total organic carbon (TOC) concentration of the water
was moderate. Moderate to high levels of TOC in supplied drinking water may indicate
that a bio-film has developed on the inside of the pipe, causing the water to taste and
smell musty.


        30        31       32     33          34       35
                           Time (min)

Figure 4 TOC Mass vs Time

As shown in Figure 5, the highest amount measured of total solids in the water was 300
mg/L. When the total solids exceed 500 mg/L, a noticeable salty taste occurs (Reference
2006). Water with total solids less than 300 mg/L is considered excellent. Total
suspended solids (TSS) and total dissolved solids (TDS) were also tested, Figure 6 and
Figure 7, and it was found that both TSS and TDS levels were low.

 Solids (mg/L)








            0   10      20      30   40      50    60        70   80   90   100
                                          Time (min)

Figure 5 Total Solids vs Time

 TSS mg/L







            0   10     20       30   40      50         60   70   80   90   100
                                           Time (min)

Figure 6 Total Suspended Solids vs Time

  Solids (mg)






            0     10      20      30      40      50        60   70   80     90     100
                                               Time (min)

Figure 7 Total Dissolved Solids vs Time

The turbidity was very low, with the highest level of 1.25 NTU, and does not affect the
taste or aesthetics of the water (Figure 8).









               0              20            40 Time         60          80               100

Figure 8 Turbidity vs Time

The iron content of the water was also very low (Figure 9), with the highest reading of
55.6 parts per billion (ppb). This is level of iron is well below the test threshold.1

    Iron (ppb)

               0         20           40       60                 80       100
                                       Time (min)


Figure 9 Iron Content vs Time

These tests suggested the need for a fixed-bed filtration / absorption system to remove
residual chlorine and total organic carbon. A reverse osmosis system would not be
necessary due to the low levels of TDS. Also, because the chlorine level is relatively
high, the chlorine could damage a reverse osmosis membrane. A filtration / absorption
system including activated carbon and ion exchange would be ideal due to its ability to
remove chlorine and TOC.

2.2 Usage Analysis
A questionnaire was issued to the faculty, staff, and graduate students in the CEE
Department asking about the usage of the existing water buffalo and sink. The
questionnaire was not issued to the undergraduates of the Department due to the fact that
most of them never enter the lounge where the sink is located and almost none of them
enter the staffroom where the water buffalo is located.

The questionnaire is reproduced in Table 1, and the results of the survey are given in
Table 2.

Table 1. Questionnaire distributed to CEE graduate students, faculty, and staff in
February 2006.

How many times a day do you use the water DISPENSER (Water buffalo) in
the staffroom for: please indicate Never, Monthly, Weekly, or Daily

Washing Dishes:
Washing Your Hands:
Drinking Water:
Watering Plants:
Other (please explain):

How often do you use the SINK in the lounge for: please indicate:
Never,     Monthly, Weekly, or Daily

Washing Dishes:
Washing Your Hands:
Drinking Water:
Other (please explain) :
Watering Plants:

Table 2. Results of CEE Community Survey, February 2006

                   Use of water from Buffalo (Tyler water dispenser)

                                 Never       Monthly   Weekly     Daily
                   Dishes              38          0          0            0
                   Hands               38          0          0            0
                   Cooking             35          2          1            0
                   Tea                   0         0          1            4
                   Water                 7         0          5           26
                   Plants              32          1          0            0

                   Use of Water from Sink
                                 Never       Monthly   Weekly     Daily
                   Dishes                9         1          6           17
                   Hands               13          5          7            8
                   Cooking             25          0          4            4
                   Tea                   0         0          2            0
                   Water               26          3          3            2
                   Plants              27          1          3            3

From the survey that was e-mailed to the graduate students, faculty and staff, a total of
100 people (75 graduate students, 15 faculty, 10 staff), there were 45 responses. Of those
responses, 7 people indicated that they were using the water buffalo for tea and hoped

that there would continue to be filtered hot water available. Also people asked for
filtered hot water so that they could use it for cooking. Based on analysis of these results,
it was determined that individual respondents used 0.6 liters of filtered water a day.

In addition to e-mail distribution of the questionnaire, another questionnaire was taped to
the water buffalo asking about one-day hot water usage. The results of the assessment of
one day usage of the hot water on the water buffalo were as follows: 24 people wrote
that they were using the hot water supply, and 4 people said that they were not. One of
these people put their name under both yes and no. It is likely that more people would
have checked yes as the yes column became completely full and no one flipped the paper
over the paper to continue the tally on the backside. One respondent noted that he was
confused as to what to do.

CEE staff member Michael Balderson indicated that approximately 20-25 five gallon
jugs were being used in the water buffalo per month as of February 2006. That comes to
4-5 a week, or 0.8-1 jug per day. Based on the number of responses that were received
about hot water usage, it can be assumed that at least one fifth of the filtered water used is
hot water. This is about 20-25 gallons a month, 4-5 gallons a week, or about 1 gallon a

From this survey it was determined that continued hot water supply would be necessary,
as well as filtered water for cooking and drinking. The estimated per person water supply
is about 4 liters.

2.3 Taste Analysis
A taste test was performed using the water from the sink, the water fountain in the
hallway, and from the water buffalo. The water from the sink was put in red plastic cups,
the water from the water fountain was put in yellow plastic cups, and the water from the
water buffalo was put in green plastic cups. Tasters were presented with a small amount

of water in a green, yellow, and red cup and were asked which one the they liked the best.
The results were then put in table form and are as follows:

Table 3. Table of Taste Test Results

Who                    Buffalo                 Hallway Water           Sink
Graduate student       1
Undergraduate          1
Undergraduate                                  1
Staff                  1
Staff                                          1
Faculty                                        1
Faculty                1
Staff                                                                  1
Staff                                          1
Undergraduate          1
Undergraduate          1
Post-doc                                                               1
Undergraduate                                                          1
Totals                 6                       4                       3

Of the 13 individuals who took the taste test, the water from the CEE water buffalo
(Tyler water dispenser) was the most preferred (6), followed by the water from the
hallway water fountain (4) and the CEE lounge sink (3). People had difficulties picking
the water they liked best when they narrowed the device to the water buffalo and the
water fountain. The water from the water fountain was served at a cooler temperature, as
was the water buffalo product since both of these units include a chiller.. Thus, it is
concluded that a water chiller should be included in the water polishing system.


3.1 Adsorption / Filtration Sytem

A variety of fixed – bed adsorption / filtrations systems were considered for removal of
residual chlorine and TOC, and any suspended solids. The complete list of considered
systems is provided in appendix A. Based on water tests it was decided that a reverse
osmosis system would not be necessary due to low TDS. Also, because the chlorine level
is relatively high, the chlorine could damage the reverse osmosis membrane.

A combination fixed bed treatment, heating, and cooling unit was considered, and then
ruled out because it would need to be rented, and because if one part malfunctions, the
entire system would not be usable

The system chosen is the Aquasana AQ-4000 Dual-Filtration Drinking water system.
This system was chosen because of its dual unit system. The “A” cartridge is an
activated carbon unit that filters out sediment and turbidity, and adsorbs chlorine. The
“B” cartridge is an ion exchange unit that removes ionic chemicals such as iron, lead, and
other metals by ion exchange adsorption. The “B” cartridge also contains a 0.5 micron
mechanical filter that removes chlorine resistant microscopic organisms. The adsorption
/ filtration system provides up to 30 gallons per hour of treated water. Replacement
cartridges are needed every 500 gallons, or approximately five times a year. The
maintenance of the system is limited to replacing the cartridges. The system has a
lifetime warranty that includes free product upgrades. This systems main advantage is
the dual-cartridge treatment system, and also the speed that it treats the water.

3.2 Cooling Unit
The Elkay water chiller system was selected for several different reasons. The Elkay
system is the best choice for its price and usage capacity. The system dispenses 2.5
gallons per hour which satisfies the estimated chilled water usage. The price of the unit is
$580, which in comparison of price with other chilling unit suppliers is the best deal. The
other suppliers units such as the Doulton UC-2 or the Bright Water ® UCCHILL-2 Under
Counter Water Chiller priced out much higher (around $700). Also, the Elkay system is
low on energy usage; at 185 watts per hour.

3.3 Heating Unit
The Quick & Hot system by Anaheim Manufacturing was selected for several reasons.
This system satisfied our estimated hot water usage. The system has 60 cups per hour
capacity of instant hot water. Also, the design is compact, satisfying spatial limitations.
Other units considered were the Franke, In-Sink-Erator, Whirl-Away systems. These
systems were satisfactory, but the overall usage capacity and efficiency of the Quick &
Hot system made it a better choice.

In addition to providing highly treated water for drinking, another important objective for
the design was to make the treatment system visible for educational purposes. It was
decided that the complete system should be put in a transparent case in the kitchen area of
the CEE department. The case would be raised from the ground, and people would be
able to look into the box to see the different parts of the water polishing treatment system.

The proposed design (Figures 1 and 2) is the case. It will be the height of the kitchen
cabinet (36 inches), 30 inches long, and 20 inches deep with glass for the front panel.
The top of the box will also be made of glass and will be fitted with a shallow stainless
steel sink and two faucets (one from the water heater, one from the water chiller). Water
will come in through a feed located at the back of the box, go into the dual cartridge

water treatment unit, out of the treatment unit, and then will split into two lines. One line
will go to the water chiller, and another, smaller line, will go to the water heater. The
water heater and water chiller will have an outgoing line that runs up the side and
connects to a faucet located at the top of the box.

Three plaques will be placed on the box describing the filtration unit, heating unit, and
chilling unit. Wording for these plaques is indicated in Table 4.

Table 4. Wording for Explanatory Plaques
Filtration Unit: Aquasana AQ-4000
Dual filtration system
Activated carbon removes dissolved organic matter and chlorine from the water
Ion exchange resin removes metal and other organic materials from the water
Filtration rate is 30 gallons an hour
Heating Unit: Quick and Hot
Public supply water flows into the tank where it is heated by an electric coil
The heated water expands, filling an expansion chamber in the upper part of the tank
When the faucet is turned on, more cold water is released into the bottom of the storage
tank, forcing the heated water up through the faucet
A 750 watt per hour, ½ gallon tank will produce up to 60 cups of hot water per hour
An adjustable thermostat, with temperatures ranging from 150-190 degrees Fahrenheit
Chilling Unit: Elkay
Works similar to a home refrigerator of air conditioner
Freon lines are wrapped around the holding tank. The liquid refrigerant is allowed to
move from a high-pressure zone to a low-pressure zone, so it expands as it evaporates. In
evaporating, it absorbs heat from the water in the holding tank rendering the water cold.
Temperature of chilled water is 50 degrees Fahrenheit under normal conditions
185 watts per hour electric water consumption
Serves 2.5 gallons of chilled water per hour

The only certain maintenance for the water polishing system in cartridge replacement for
the absorption / filtration unit. The predicted replacement rate of the filters is about one
per month during the regular school year, and one per two months in the summer. From
this calculation it was determined that 10 filters +/- 1 would be needed per year. The
water chiller and heater have no routine maintenance requirements.

The cost analysis is based on maintenance prediction, cartridge cost, energy usage, and
cost of systems.

Table 5. Initial cost
Aquasana AQ-4000 filtration unit                $120.00
Quick and Hot Heating Unit                      $130.29
Elkay Chilling Unit                             $550.00
Building / Plumbing Materials                   $500.00
Faucets                                         $150.00
Total                                           1450.29

Table 6. Subsequent yearly cost
5 filter / absorption cartridges                $280.00

The water polishing system will provide the Civil and Environmental Engineering
department filtered, heated and chilled water. It will replace the Tyler water buffalo
currently in the staff lounge. The water polishing system has a capital cost of $400.00
and a yearly operating cost of $225.00. The yearly operating cost is $1175.00 less than
the current systems annual cost. The components of the system will be placed in a box
with a clear panel in the kitchen of the Civil and Environmental Engineering lounge.

Appendix. A

Chlorine Data:
Chlorine 1 test taken Thursday, February 9, 3:30-5:00pm
Chlorine 2 test taken Monday, February 13, 1:45-3:15pm
Chlorine 3 test taken Wednesday, March 1, 9:00-10:30p
Time (min)              Chlorine 1 (mg/L)       Chlorine 2 (mg/L)      Chlorine 3 (mg/L)
                  0.5                    0.70                   1.58                   4.26
                    1                    0.24                   0.15                       0.7
                    3                    0.65                   0.24                   2.32
                    5                    0.09                   0.64                   2.83
                   10                    0.87                   2.17                   2.24
                   20                    0.15                   1.06                   2.92
                   30                    0.10                   0.34                   0.49
                   40                    0.05                   0.83                   0.72
                   50                    0.12                   1.38                   2.79
                   60                    0.91                   1.60                   0.16
                   70                    0.63                   0.99                   2.53
                   80                    0.25                   0.81                   1.97
                   90                    0.13                   0.43                       2.6

TOC Data:
Mass                                            Concentration
                                         71.1                                              7.1
                                         64.5                                              6.5

                                               68.6                                                    6.9
                                               59.7                                                       6
                                               61.1                                                    6.1

Total Solids:
Used 100mL of H20
                  Initial Pan      Final pan                                               Total Solids
Time (min)        weight (mg)      weight (mg)        Chlorine          Turbidity          mg/L
              0           5500.9           5521                   0.7                0.9               201
             10           5510.1          5536.8                 2.17               1.05               267
             30           5476.6           5506                  0.34               0.75               294
             70           5433.1          5458.2                 0.99               1.25               251
             90             5451          5475.7                 0.43               0.65               247

Total Suspended Solids:
Time (min)                                            Total Suspended Solids (mg/L)
                                                 0                                                        -9
                                                10                                                     96
                                                30                                                     85
                                                70                                                     25
                                                90                                                     35

Total Dissolved Solids:
Used 100 mL of H20
                  Initial Pan      Final pan                                               Dissolved
Time (min)        weight (mg)      weight (mg)        Chlorine          Turbidity          Solids (mg/L)
              0             5479           5500                   0.7                0.9               210
             10           5496.4          5513.5                 2.17               1.05               171

             30         5456         5476.9               0.34               0.75     209
             70       5412.1         5434.7               0.99               1.25     226
             90       5430.3         5451.5               0.43               0.65     212

Chlorine data was obtained from test two, which was the test that ran while the samples
used for turbidity were obtained.
Time min                       Chlorine mg/L                     Turbidity
                           0                               0.7                         0.9
                           5                              0.64                         1.2
                          10                              2.17                        1.05
                          20                              1.06                         1.3
                          30                              0.34                        0.75
                          40                              0.83                        0.95
                          50                              1.38                         0.9
                          60                               1.6                         0.8
                          70                              0.99                        1.25
                          90                              0.43                        0.65

Time (min)                                     Fe (ppb)
                                          0                                         29.335
                                         10                                         30.445
                                         30                                         30.765
                                         50                                          29.92
                                         70                                         38.385
                                         90                                          55.62


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