-
Evaluation of Chemical and Non-Chemical Treatment
Methods for Condenser Water
Ng Wai Lun1, Yoon Li Wan1 and Satesh Narayana Namasivayam1, Chen
Thiam
Leong2
1 School of Engineering, Faculty of Innovation and Technology,
Taylor’s University Lakeside Campus, No. 1, Jalan
Taylor’s, 47500 Subang Jaya, Selangor, Malaysia. 2 Green
Building Index Sdn Bhd, Level 4, PAM Centre, 99L, Jalan Tandok,
Bangsar, 59100, Kuala Lumpur,
Malaysia
*Corresponding author: [email protected]
Abstract. In the Heating, Ventilation and Air Conditioning
(HVAC) field, condenser water is used to remove heat from
the refrigerant cycle and is cooled at cooling towers. Due to
the high operating temperatures of 29°C to 38°C, the condenser
water cycle is vulnerable to operating issues such as scaling,
corrosion and microbiological proliferation; which can be
mitigated through either chemical or non-chemical treatment
methods. In this paper, the chemical and non-chemical
treatment methods for condenser water treatment in the Heating,
Ventilation and Air Conditioning (HVAC) systems are
compared in terms of efficiency (scaling, corrosion and
microbiological proliferation control) and environmental
impact.
The efficiency of one chemical treatment system (descalant) and
three non-chemical treatment systems (Merus Ring, Power
Pulsed and Ultra Low Frequency) are investigated by taking
condenser water samples from the cooling tower basins
biweekly for three months to characterize for pH, water
alkalinity, iron content, chloride content, total dissolved
solids
(TDS) content, electrical conductivity and water hardness, which
are compared to the Japan Refrigeration and Air
Conditioning Industry Association Standards (JRA-GL-02-1994) and
applied to the Langelier Saturation Index (LSI),
Ryznar Stability Index (RSI) and Practical (Puckorious) Scaling
Index (PSI) to predict the scale formation in condenser
water samples. The temperature differences between chilled
waters for all systems investigated are recorded to relate the
characterized parameters to chiller efficiency. The
environmental impacts for all systems investigated are assessed
by
focusing on the operational stage of all system where the main
source of environmental damage is due to the electrical
consumption by the HVAC systems. The results yield that all
systems investigated comply to the industrial standards. LSI
and RSI proved that all condenser waters are saturated with
calcium ions but PSI proved that scale formations in the
systems
investigated are unlikely as the scales are likely to remain
dissolved in the condenser water. Consistent temperature
differences of chilled water are observed throughout the
research period which show that the performance of chillers in
each system are optimal, which proves that non-chemical
treatment systems are as efficient (in terms of corrosion,
scaling
and microbial activity control) as chemical treatment system.
Environmental impact analysis concluded that chemical
treatment system has the highest annual equivalent CO2 emission
per cooling capacity of 868.30 kg CO2 e/year RT. Thus,
non-chemical treatment systems have lesser environmental impact
than chemical treatment system.
Key words: HVAC System, Condenser Water Treatment Systems,
Corrosion, Scaling, Microbiological Proliferation
mailto:[email protected]
-
INTRODUCTION
The typical Heating, Ventilation and Air-conditioning (HVAC)
system of a commercial building consists of key
systems such as the chilled water cycle, refrigerant cycle and
the condenser water cycle. As seen in Figure 1, the
chilled water first enters the Air Handling Unit (AHU) where it
exchanges heat with the air in the room or space. The
air turns cooler and the chilled water temperature increases.
The chilled water then flows to an evaporator where it
exchanges het with the refrigerant to be cooled before repeating
the cycle again. The warm refrigerant is then
compressed to enter the condenser where it exchanges heat with
condenser water before passing through an expansion
valve to be heated up again in the evaporator. The warm
condenser water first enters the cooling tower to be cooled
by using ambient air. After being cooled, the condenser water
then repeats the cycle by entering the condenser again
to exchange heat with the warm refrigerant.
FIGURE 1: Illustration of a typical HVAC system of a commercial
building.
As illustrated in Figure 1, all three systems are operating in
closed loops. Thus, if no proper treatment was done to
the systems, impurities in the chilled water and condenser water
could cause issues such as scaling, corrosion and
microbiological proliferation, which can decrease the efficiency
of the cooling system [1]. The condenser water system is highly
vulnerable to these operational issues due to the high operating
conditions
of 29°C to 38°C [2], as compared to chilled water with the
operating temperatures of 5°C to 7°C.As temperature
increases, the possibility of corrosion and scaling increases as
soluble solids at low temperatures starts forming at high
temperatures [1]. In addition to that, microbiological
activities typically take place at ambient temperatures.
Condenser water treatment methods can be separated into chemical
methods that include the use of chemicals such
as biocides, corrosion and scaling inhibitors as well as the
non-chemical treatment methods that include the use of
devices that use physical principles such as interfering and
resonance oscillations [3], power-pulsed device [4] and
ultra-low frequency in the control of scaling, corrosion and
microbial activity.
To catalyze the application of non-chemical treatment methods
for condenser water loops in HVAC systems,
Malaysia’s first green rating tool, Green Building Index (GBI)
pledges to award one (1) innovation point for buildings
that use non-chemical methods for the treatment of condenser
water [5].
Although numerous studies have proven the effectiveness of the
non-chemical treatment methods in controlling
scaling, corrosion and microbiological proliferation [3, 4],
these studies are conducted without benchmarking with
chemical treatment methods. This shows that the efficiency
comparison (in terms of scaling, corrosion and microbial
activity control) between chemical treatment systems and
non-chemical treatment systems is yet to be investigated.
In the cradle to grave lifecycle of both chemical and
non-chemical treatment methods for condenser water in the
HVAC systems, there will certainly be environmental impact such
as the production of greenhouse gases (GHG) due
-
to various activities ranging from the manufacture stage to the
transportation, construction, maintenance and operation
as well as the demolition stage [6].
Quantification of environmental impact requires lifecycle
assessments and that there are no known studies
conducted to compare the environmental impacts between the
chemical and non-chemical treatment methods for
condenser water in HVAC systems.
In this study, the first objective is to identify the suitable
system with effective corrosion and scaling control for
condenser water treatment among the chemical and non-chemical
treatment systems investigated. The second
objective is to evaluate the environmental impact during the
operational stage of the chemical and non-chemical
treatment systems for condenser water treatment.
RESEARCH METHODOLOGY
In this study, three non-chemical treatment methods for
condenser water are investigated. The first system uses
Merus ring magnetic device, denoted as system A, the second
system uses ultra-low frequency technology, denoted
as system B that and the third system uses power pulsed device,
denoted as system C. The chemical treatment method
that is investigated that uses descalant and biocide, denoted by
system D.
Efficiency Analysis
The efficiency analysis is conducted in two aspects, treatment
efficiency and chiller efficiency. Treatment
efficiency includes the sampling and characterization of
condenser water as well as the prediction of scaling and
corrosion. The chiller efficiency is analyzed by taking the
temperature differences of chilled water in the chillers of
the systems investigated.
Sampling and Characterization of Condenser Water
The sampling of the condenser water from systems A to D are
conducted biweekly for nine (9) weeks with the
assistance from engineers responsible for the cooling tower
operations of the systems investigated. During each
sampling trial, three (3) samples are taken at random for all
running cooling towers during the time of sampling. The
condenser water samples are stored at 4°C before further testing
and analysis.
The characterization of condenser water samples is conducted by
analyzing for the pH, water alkalinity, water
hardness, electrical conductivity, total dissolved solids (TDS)
content, chloride and iron content. The pH, TDS and
electrical conductivity can be measured by using the pH meter
(Eutech, pH700, Fisher).
Test kits such as the iron test kit, alkalinity test kit and
chloride test kit are purchased from Merck and are used to
test for the iron content, water alkalinity and chloride content
respectively. Spectrophotometer (Prove 300, Merck,
VSA) is used to measure the absorbance at respective wavelength
for different tests.
The water hardness is evaluated through the colorimetric
titration method that uses ethylene diamine tetra acetic
acid (EDTA) and Solochrome black-T (EBT). In this method, EBT
and ammonium buffer solution are added to the
condenser water samples. EDTA is then used to titrate the water
samples until it turns from wine red to steel blue.
This method requires a calibration curve constructed by using
standard hard water in replacement of the condenser
water in the titration to relate the water hardness to the
volume of EDTA required to reach the end point of titration
where the color change occurs.
For microbiological proliferation, the heterotrophic plate count
(HPC) method is used to characterized the colonies
of heterotrophic bacteria present in the condenser water
samples. In addition, the test for Legionella sp. is conducted.
The test for microbiological proliferation will be conducted
twice throughout the study period.
The raw data obtained from the characterization is initially
compared with Japan Refrigeration and Air
Conditioning Industry Association Standards (JRA-GL-02-1994) to
check if the operating parameters of the condenser
water are met. Appendix 1 shows a copy of the JRA-GL-02-1994
extracted from the Japan Refrigeration and Air
Conditioning Industry Association [7].
The analysis of variance (ANOVA) single factor is used to assess
the significance of batch to batch variations in
readings. The significance is evaluated at p
-
Prediction of Scaling and Corrosion
The scaling and corrosion potential for the condenser water
samples are predicted by using LSI, RSI and PSI as it
is widely applicable in the study of potentially corrosion and
circulating water [8, 9, 10],. The formulae for the calculations of
LSI, RSI and PSI are tabulated in Table 1. Table 2 shows the
interpretation of the indices calculated.
TABLE 1: Tabulation of formulae for LSI, RSI and PSI.
Index Equations
Langelier Saturation Index
(LSI)
𝐿𝑆𝐼 = 𝑝𝐻 − 𝑝𝐻𝑠 Eq. (1) 𝑝𝐻𝑠 =
𝐴 + 𝐵 − 𝑙𝑜𝑔10(𝐶𝑎2+) − 𝑙𝑜𝑔10(𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦)
For pH ≤ 9.3
Eq. (2)
𝑝𝐻𝑠 = (9.3 + 𝐴 + 𝐵) − (𝐶 + 𝐷) For pH > 9.3 Eq. (3) 𝐿𝑆𝐼 = 𝑝𝐻 −
𝑝𝐻𝑠 Eq. (4)
Ryznar Stability Index (RSI) 𝑅𝑆𝐼 = 2𝑝𝐻𝑠 − 𝑝𝐻 Eq. (5)
Practical (Puckorious) Scaling
Index (PSI)
𝑃𝑆𝐼 = 2𝑝𝐻𝑠 − 𝑝𝐻𝑒𝑞 Eq. (6)
𝐴 = 𝑙𝑜𝑔10[𝑇𝐷𝑆] − 1
10 Eq. (7)
𝐵 = −13.2 × 𝑙𝑜𝑔10(°𝐶 + 273) + 34.55 Eq. (8) 𝐶 = 𝑙𝑜𝑔10[𝐶𝑎
2+𝑎𝑠 𝐶𝑎𝐶𝑂3] − 0.4 Eq. (9) 𝐷 = 𝑙𝑜𝑔10[𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦] Eq. (10)
𝑝𝐻𝑒𝑞 = 1.465 × 𝑙𝑜𝑔10[𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦] + 4.54 Eq. (11)
[𝐴𝑙𝑘𝑎𝑙𝑖𝑛𝑖𝑡𝑦] = [𝐻𝐶𝑂3−] + 2[𝐶𝑂3
2−] + [𝑂𝐻−] Eq. (12)
TABLE 2: Tabulation of index values and the corresponding water
condition.
Index Index Values Water Conditions
LSI LSI > 0 Super saturated, tend to precipitate calcium
carbonate
LSI = 0 Saturated, calcium carbonate is in equilibrium
LSI < 0 Under saturated, tend to dissolve solid calcium
carbonate
RSI RSI < 6 Super saturated, tend to precipitate calcium
carbonate
6 < RSI < 7 Saturated, calcium carbonate is in
equilibrium
RSI > 7 Under saturated, tend to dissolve solid calcium
carbonate
PSI PSI < 6 Scaling is unlikely to occur
6
-
LSI takes the difference between the pH and the saturation pH of
the condenser water to determine the potential
of scaling but does not giving insights on how much scale is
expected to form [11], which is why this index is
commonly used in combination of other indices such as the RSI to
accurately describe the scaling potential of the
given condenser water.
In the RSI, the saturation term is doubled to increase the
sensitivity of the index to the saturation pH of calcium
carbonate in the water sample, which can approximate the
tendency of precipitation of calcium carbonate. RSI is
proven to be more accurate and sensitive than LSI as proven by
Hoseinzadeh et al. [12] where RSI yielded a smaller
percentage error of corrosion potential of 5.5% when compared to
LSI with 18.1%.
PSI considers the equilibrium pH instead of the actual pH, which
minimizes the effect of buffering agents such as
caustic and ammonia that can result in inaccurate conclusion of
scaling tendency calculated by LSI and RSI [13]. All indices are
calculated and the interpretations of the condenser water are based
on Table 2.
Chiller Temperature Difference Analysis
The chiller efficiency can be measured from the temperature
difference of the chilled water that enters and leaves
the chiller. The operational load of the chiller changes with
respect to the demand for cold air by the occupants of the
buildings, which is also dependent on the duration of the
day.
Operational load refers to the demand of cooling required by the
building. For instance, in the morning with lesser
occupants in a building, the cooling demand is lesser than when
in the afternoon with more occupants.
Due to these changes, the temperature difference readings are
taken consistently biweekly on site with the sampling
schedule at the specified time as shown below:
System A: 11.00 A.M. – 11.30 A.M.
System B: 12.00 P.M. – 12.30 P.M.
System C: 10.00 A.M. – 10.30 A.M.
System D: 2.30 P.M. – 3.00 P.M.
The readings obtained are plotted in a line graph to monitor the
trends of the temperature differences of the systems
investigated over the study period to investigate the impact of
the operational parameters of condenser water
characterized with the chiller efficiency.
Environmental Impact Analysis
Quantification of environmental impact by the HVAC systems can
be done through lifecycle assessment (LCA)
from cradle to grave [6]. This research only focuses on the
environmental impact of HVAC systems during the
operational stage. According to the inventory analysis by Chen
et al. [14], the most significant environmental impact
during the operational stage of the HVAC systems is due to the
electricity consumption.
According to the local energy provider, Tenaga Nasional Berhad
(TNB), the emission factor per kWh of power
produced is 0.55 kg CO2 e/kWh [15]. From this information, the
environmental impact analysis for all systems of
condenser water treatments is carried out by evaluating the
annual equivalent carbon dioxide (CO2) released per
cooling capacity which can be calculated by multiplying the
emission factor with the annual power consumption by
each system investigated.
The assumptions made for the calculation of environmental impact
analysis include:
1. Chiller as the major power consumer in the HVAC system. 2.
80% average motor operating load. 3. Chiller is operational for 12
hours per day. 4. Chiller is operational for 260 days per year.
The chiller power consumption is calculated by considering of
the rated power input and the total number of
chillers present at the HVAC systems.
For comparison of the environmental impact between the systems
to be possible, the annual CO2 emission
calculated must be divided by the respective system
capacities.
-
During the operational stage, the biocide and descalant used by
system D in the control of scaling, corrosion and
microbial activity control may have environmental impacts which
are not considered while calculating for the annual
emission of carbon dioxide equivalent.
However, the SDS for the chemicals used by system D will be
analyzed to check for any environmental impacts
that the chemicals may have.
RESULTS AND DISCUSSIONS
Efficiency Analysis
The efficiency analysis includes the characterization of
condenser water samples, the scaling and corrosion
prediction analysis and the chiller performance analysis.
Characterization of Condenser Water Samples
(a) (b)
(c) (d)
-
(e) (f)
FIGURE 2: Results from characterization of condenser water
samples for (a) pH (b) alkalinity (c) chloride content (d)
water
hardness (e) water conductivity and (f) TDS.
The red lines in Figure 2(a), (b), (e) and (f) show the limit of
the respective operating parameters in accordance to
JRA-GL-02-1994. Figure 2(c) and (d) does not have red lines
because the operating limits are out of range from the
chart. The limits for chloride content and water hardness are
200 mg/L Cl- and 600 mg/L CaCO3 respectively.
pH and Alkalinity
From Figure 2(a) and (b), all systems are by complying the
standards except for sampling trial 1 system C and
sampling trial 4 system A. The exception of these two cases can
be explained.
Firstly, for sampling trial 1 system C, it is reported that
there is maintenance conducted not long before the
sampling of condenser water at system C. This causes residual
impurities to be within the condenser water line that
contributes to the high readings.
On the other hand, for sampling trial 4 system A, it is reported
that the sand filter used on site was offline for
maintenance for the week where sampling of condenser water is
conducted. During this week, only one sand filter
was online and it is insufficient to maintain condenser water
quality. This immediately resulted in the spike of reading
for all operating parameters except chloride content.
Chloride Content and Water Hardness
From Figure 2(c) and (d), it is seen that all systems are
operating well below the standards. However, the most
significant reading found is on sampling trial 4 system A. The
reason of the high readings is explained previously due
to the maintenance of the sand filter on site.
It is also worth noticing that the readings taken in system D
are generally lower and more consistent when
compared to the non-chemical treatment systems for chloride
content, water hardness, conductivity and TDS. At the
same time, the non-chemical treatment systems can be said that
it has lesser consistency and that the readings are
generally higher than the chemical treatment system.
Water Conductivity and TDS
From Figure 2(e) and (f), it is seen that all systems generally
operate below the standards. The spike of reading for
sampling trial 4 system A is explained earlier as the
maintenance of sand filter on site. However, it is also worth
mentioning that system B operates near the standards for water
conductivity after the first sampling trial.
This is due to the faulty TDS sensor on site that resulted in
insufficient bleeding of condenser water which leads
to the high readings of both conductivity and TDS content from
sampling trail 2 to sampling trial 5. It is known that
the faulty TDS sensor was not replaced.
-
Similar to the chloride content and water hardness, system D
generally has readings that are lower and more
consistent when compared to systems A, B and C.
System A, B and C showed
-
TABLE 5: Tabulation of calculations and implications of LSI, RSI
and PSI.
Index Implication
Samples LSI RSI PSI LSI RSI PSI
Trial 1
A 0.02 7.51 7.85 SSa USa SDa
B 0.51 6.94 7.47 SS Sa SD
C 0.70 6.65 7.13 SS S SD
D 0.18 7.28 7.61 SS US SD
Trial 2
A 0.61 6.68 7.19 SS S SD
B 0.78 6.57 7.37 SS S SD
C 0.67 6.76 7.42 SS S SD
D 0.44 7.05 7.55 SS US SD
Trial 3
A 0.48 6.94 7.67 SS S SD
B 0.52 7.03 8.17 SS US SD
C 0.50 6.98 7.63 SS S SD
D 0.65 6.89 7.95 SS S SD
Trial 4
A 1.00 5.94 6.33 SS SS Sta
B 0.72 6.59 7.26 SS S SD
C 0.33 7.31 7.99 SS US SD
D 0.33 7.32 8.15 SS US SD
Trial 5
A 0.75 6.47 7.05 SS S SD
B 0.72 6.45 6.92 SS S St
C 0.49 6.84 7.24 SS S SD
D -0.14 7.72 8.0 US US SD aSS: Super Saturated; US: Under
Saturated; SD: Scale Dissolves; S: Saturated; St: Stable
Contradictory results between LSI and RSI are also published in
literature by Kim et al. [16], Al-Huseini [17],
Shams et al. [18] and Shankar [19]. The contradictory results
are often caused by the actual pH values of the water
samples. By using pH to compare between Table 5 and Figure 2(a),
it can be seen that water samples with pH of less
than 7.8 generally yields ‘US’ result RSI while having ‘SS’ for
LSI. Because of the relatively low pH, both LSI and
RSI values are at the borderlines of the descriptions of water
conditions as shown in Table 2. In these cases, the water
conditions need to be verified by using PSI to check for the
scaling condition.
For condenser water samples that have pH values of more than
7.8, the LSI remains to have ‘SS’ and that the RSI
gives ‘S’. From the two indices, it is agreeable that calcium
ions in these water samples are saturated. However, the
degree of saturation remains unknown due to the contradicting
results from LSI and RSI. Hoseinzadeh et al. [12] proved that RSI
is more accurate when compared to LSI as the sensitivity to the
saturation pH of calcium carbonate
is increased. This implies that RSI is a more reliable index to
indicate the scaling potential due to the degree of
saturation of the water samples. Shankar [19] supported this
statement by justifying that the range of water condition
for the LSI is more limited as a solid zero is needed to show
that the water is saturated as shown in Table 2. On the
other hand, RSI provides a range of 6 to 7 for a saturation zone
which allows more flexibility in terms of the water
condition. Therefore, in these cases where the pH values of the
condenser water samples are more than 7.8, the water
condition is concluded from RSI instead of LSI.
As LSI and RSI only describe the tendencies of the scale
formation in water bodies without giving insights on how
much scale is expected, PSI must be used in addition to LSI and
RSI to confirm the condenser water conditions. The
PSI readings show that all condenser waters are likely to
dissolve scale except for sampling trial 4 system A and
sampling trial 5 system B. This shows that the condenser water
samples do not have scale formation tendencies. The
stable condition of condenser water for sampling trial 4 system
A is caused by the maintenance of sand filter on site.
The stable condition of condenser water for sampling trail 5
system B is caused by the faulty TDS sensor on site that
leads to insufficient bleeding of condenser water.
-
In summary, although that the condenser water samples are
saturated with calcium ions as proven by LSI and RSI,
the scale formations in the systems investigated are unlikely as
the scales will remain dissolved in the condenser water
as proven by PSI.
Chiller Performance Analysis
Figure 3 shows the graph of temperature difference of chilled
water for systems A to D across the study period.
As mentioned, the timings of the registration of readings for
the chilled water temperatures from each system are
different but consistent. Therefore, instead of comparing system
by system, the consistencies of each system in terms
of the temperature difference of chilled water are
investigated.
From Figure 3, it is seen that the temperature differences for
systems A, B and D are consistently in the range of
3.0°C to 5.0°C. For system C, the inconsistent temperature
difference readings are due to the different operating loads
of the chiller on site.
For systems A, B and D, the consistent temperature differences
of chilled water are the results of the operation of
condenser water that is generally below the industrial
standards. Because of this, operational issues such as
corrosion,
scaling and microbiological proliferation are prevented which
allows optimal operation of the HVAC systems in
system A, B and D.
For system C, the fluctuations in the temperature differences
between the chilled water in the chiller does not
necessarily mean that the operation of condenser water exceeds
the industrial standards. This is further reinforced by
the excellent results obtained by system C in the
characterization of condenser water in Figure 2.
FIGURE 3: Chilled water temperature difference in chillers.
Therefore, the fluctuations of temperature difference between
the chilled water in the chiller in system C is not
caused by operational issues of condenser water such as
corrosion, scaling and microbiological proliferation. The
fluctuation in the temperature difference of chilled water is
however due to the different chiller operating loads.
In system C, for sampling trials of 1, 2 and 5, the chiller is
running at operating loads of 103%, 100% and 98%
respectively, while for sampling trials of 3 and 4, the chiller
is running at operating loads of 58% and 51%, although
that the readings are taken consistently between 10.00 A.M. to
10.30 A.M.
It is clear that the temperature difference fluctuations of
system C is caused by the operational load of the chiller.
Therefore, based on the results obtained from the
characterization of condenser water samples, it can be
concluded
that the HVAC system in system C operates optimally without
issues such as corrosion, scaling and microbiological
proliferation.
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
0 1 2 3 4 5 6
Chil
led
Wat
er T
emp
erat
ure
Dif
fere
nce
,
°C
Sampling Trials
Chilled Water Temperature Difference
System A
System B
System C
System D
-
Environmental Impact Analysis
Table 6 shows the tabulation of information required for the
calculation. The rated power inputs for the chillers in
system C are unobtainable. Thus, the calculation of the power
input to the chillers in system C is evaluated by using
the chiller efficiency information as shown in Table 6.
TABLE 5: Tabulation of system specifications for environmental
impact calculations.
System Number of Chillers Power Input (kW) Chiller
Efficiency
(kW/RT)
Cooling Capacity
(RT)
A 3 342 0.670 2700
B 3 310 0.670 1650
C 7 NAa 0.175 8000
D 4 253 NA 1600 aNA: Not Applicable (For information that are
unobtainable)
By considering the assumptions listed out for the calculations,
the annual electricity consumption of the chillers
for each system can be evaluated, followed by the annual
equivalent emission of CO2 per RT. Table 7 shows the
tabulation of the results calculated for the environmental
impact analysis.
TABLE 6: Tabulation of results for environmental impact
analysis.
System
Annual
Electricity Consumption
(kW/year)
Annual Equivalent
CO2 Emission
(kg CO2 e/year)
Annual Emission per
Cooling Capacity
(kg CO2 e/year RT)
A 2,560,896 1,408,493 521.66
B 2,321,280 1,276,704 773.76
C 3,494,400 1,921,920 240.24
D 2,525,952 1,389,274 868.30
As observed in Table 7, the annual emission per cooling capacity
for system D is the highest at 868.30 kg CO2
e/year RT when compared to the non-chemical treatment systems of
A to C. This indicates that the non-chemical
treatment systems for condenser water in the HVAC systems causes
lesser environmental impact (in terms of CO2
emission) when compared to the chemical treatment system.
From Tables 6 and 7, it is seen that the chiller in system D
consumes only 253 kW, but when the comparison of
the same cooling capacity is made, system D yields the highest
annual emission per cooling capacity. This shows that
the chillers in system D are not as efficient as the chillers in
system A, B and C because that it requires more energy
to produce 1 RT of cooling capacity. Therefore, from the
environmental impact analysis, it can be seen that the
chemical treatment system not only produces more CO2 equivalent
annually per RT, it is also shown to have the least
efficient chillers when compared to the non-chemical treatment
systems.
In addition, there are three (3) chemicals used in the control
of scaling, corrosion and microbial activity control in
system D. The three chemicals are labelled as CL-320, CL-650 and
CL-653.
CL-320 is an organo-phosphonate based corrosion and scale
inhibitor that has the combination of calcium
carbonate inhibitor, dispersant, dual phosphonate and yellow
metal inhibitor to control corrosion of mild steel, copper
and admiralty brass. This chemical also minimizes hardness salt
formation in alkaline cooling water.
CL-650 is a non-oxidizing blend of quaternary ammonium
compounds-based biocide that functions to control the
activity of bacteria, fungi and algae in open re-circulating
cooling water systems. It also contains dispersing agents
that ensure good distribution throughout the system and
efficient penetration of slime masses.
CL-653 is a non-oxidizing mixture of isothiazolin based biocide
that is designed specifically for the control of
bacteria, fungi and algae in open re-circulating cooling water
system. This product has low foaming tendency and is
compatible with most treatment chemicals.
According to the SDS of the chemicals, CL-320 has no
environmental impact during the usage, but CL-650 and
CL-653 have reported to have category 3 acute aquatic hazard,
which means that short term exposure (15 minutes) of
10 mg/L to 100 mg/L of the chemicals can cause damage to aquatic
environment and subsequently to the aquatic
-
organisms. Thus, this concludes that the non-chemical treatment
systems might cause lesser environmental impact
when compared to the chemical treatment system.
CONCLUSION
In conclusion, the efficiency analysis proves that the chemical
and non-chemical treatment systems are capable in
maintaining operating parameters such as the pH, water
alkalinity, iron content, chloride content, TDS, water
electrical
conductivity and water hardness by complying the industrial
standards such as the JRA-GL-02-1994. In addition to
that, the calculations of LSI, RSI and PSI concluded that all
condenser water samples are saturated with calcium ions,
but scale formations are unlikely as the scales are likely to
remain dissolved in the condenser water. Because of the
adherent to the industrial standards, the chillers in all
systems are able to run optimally with consistent temperature
difference between the chilled water taken at consistent
timings.
Secondly, the environmental impact analysis concluded that the
non-chemical treatment systems have lesser
environmental impact compared to the chemical treatment system
with an annual equivalent emission of CO2 of
868.30 kg CO2 e/year RT which is the most among the systems
investigated. Due to the chemicals used, the chemical
treatment system might have more negative environmental impact
when compared to the non-chemical treatment
systems.
ACKNOWLEDGMENT
The authors would like to express gratitude to panels from Green
Building Index, EnGreen, Greneco and Taylor’s
University for the support and cooperation throughout the
research project.
REFERENCES
[1] J. P. Guyer, P.E., R.A., F. ASCE and F. AEI, "An
Introduction to Cooling Tower Water Treatment," Continuing
Education and Development, Inc., New York, 2014.
[2] American Society of Heating, Refrigerating and
Air-Conditioning Engineers (ASHRAE), The ASHRAE
GreenGuide: The Design, Construction, and Operation of
Sustainable Buildings, ASHRAE Press, 2006.
[3] Hawari, Z. A. Rahman and Yahaya, "Merus Ring Technology for
Boiler Feed Water Treatment," Malaysia Palm
OIl Board, Kuala Lumpur, 2012.
[4] Y. I. Cho, J. Lane and W. Kim, "Pulsed-power treatment for
physical water treatment," International
Communications in Heat and Mass Transfer, vol. 32, pp. 861-871,
2005.
[5] Green Building Index Sdn Bhd, GBI Assesment criteria:
industrial new construct ion (INC), Kuala Lumpur:
Green Building Index Sdn Bhd, 2011.
[6] S. Chen, "System Dynamics Based Models for Selecting HVAC
System for Office Buildings: A Life Cycle
Assessment from Carbon Emission Perspective," School of Civil,
Environmental and Chemical Engineering,
College of Science, Engineering and Health, RMIT Univetsity,
Melbourne, 2012.
[7] Japan Refrigeration and Air Conditioning Industry
Association Standards, Water Quality Standard for Cooling
water, Cold water, Hot water, Makeup water, Japan: Japan
Refrigeration and Air Conditioning Industry
Association, 2011.
[8] M. Mirzabeygi, M. Naji, N. Yousefi, M. Shams, H. Biglari and
A. H. Mahvi, "Evaluation of corrosion and
scaling tendency indices in water distribution system: a case
study of Torbat Heydariye, Iran," Desalination and
Water Treatment, vol. 10, pp. 1-9, 2016.
[9] A. Gholizadeh, M. Mokhtari, N. Naimi, B. Shiravand, M. H.
Ehrampoush, M. Miri and A. Ebrahimi,
"Assessment of corrosion and scaling potential in groundwater
resources; a case study of Yazd-Ardakan Plain,
Iran," Groundwater for Sustainable Development, vol. 5, pp.
59-65, 2017.
-
[10] U. M. Etesin1, T. Harry, I. O. Isaac and U. G. Isotuk, "A
Study of Potential Corrosivity of Borehole Waters in
Eket, Nigeria by Saturation Index Measurement," Asian Journal of
Environment & Ecology, vol. 7, no. 3, pp.
1-13, 2018.
[11] Y. Chen, Y. Cui, A. G. Barrett, F. Chille and S. Lassalle,
"Investigation of calcite precipitation in the drainage
system of railway tunnels," Tunnelling and Underground Space
Technology, vol. 84, pp. 45-55, 2019.
[12] E. Hoseinzadeh, A. Yusefzadeh, N. Rahimi and H. Khorsandi,
"Evaluation of Corrosion and Scaling Potential
of a Water Treatment Plant," Archives of Hygiene Sciences, vol.
2, no. 2, pp. 41-47, 2013.
[13] A. Takdastan, M. M. (Radfard), A. A. Mahmood Yousefi, R.
Khodadadia, H. Soleimani, A. H. Mahvi and D. J.
Naghan, "Neuro-fuzzy inference system Prediction of stability
indices and Sodium absorption ratio in Lordegan
rural drinking water resources in west Iran," Data in Brief,
vol. 18, pp. 255-261, 2018.
[14] S. Chen, K. Zhang and S. Setunge, "Comparison of Three HVAC
Systems in an Office Building from a Life
Cycle Perspective," School of Civil, Environmental and Chemical
Engineering, RMIT University, Melbourne,
2011.
[15] Tenaga Nasional Berhad (TNB), "Sustainability Report 2017,"
Tenaga Nasional Berhad, Kuala Lumpur, 2017.
[16] J. Kim, S. K. Behera, S. Oh and H. Park, "Reuse potential
of municipal wastewater treatment facility effluents
for sustainable water resource management in Ulsan, Korea,"
Waater and Environment Journal, vol. 24, no. 4,
pp. 293-302, 2010.
[17] A. Al-Husseini, " Study of potential corrosion and scaling
for treated water of two water treatment plants in Al-
Hilla City," Journal of Babylon University, Engineering
Sciences, vol. 4, no. 20, pp. 1180-1190, 2012.
[18] M. Shams, A. Mohammadi and S. A. Sajjadi, "Evaluation of
corrosion and scaling potential of water in rural
water supply distribution networks of Tabas, Iran," World
Applied Sciences Journal, vol. 17, no. 11, pp. 1484-
1489, 2012.
[19] S. B.S., "Determination of Scaling and corrosion tendencies
of water through the use of Langelier and Ryznar
Indices," Scholars Journal of Engineering and Technology (SJET),
vol. 2, no. 2A, pp. 123-127, 2014.
[20] K. A. KITZMAN, E. F. MAZIARZ, B. PADGETT, C. D.
BLUMENSCHEIN and A. SMITH, "Chemical vs.
Non-chemical Cooling Water Treatments – a Side-by-Side
Comparison," Alcoa’s Mt. Holly Works, Pittsburgh
, 2008.
[21] G. Tomberlin, J. Dean and M. Deru, "Electrochemical Water
Treatment for Cooling Towers," National
Renewable Energy Laboratory (NREL), Golden, 2019.
[22] D. Cutler, J. Dean, J. Daw and Dan Howett, "Alternative
Water Treatment Technologies for Cooling Tower
Applications," National Renewable Energy Laboratory (NREL),
Golden, 2019.
