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The Effects of Chlorine and Sunlight on Algae in the Kanapaha
Water Reclamation Facility Chlorine Contact Basins
In order to grow, algae need sunlight and a surface that can provide nutrients and is almost permanently wet.
With this in mind, algae growth in the chlorine contact basins (CCBs) at the Kanapaha Water Reclamation
Facility (KWRF) was proposed to be controlled by covering the basins, which would prevent the exposure
of wastewater to sunlight. Two factors were directly altered by covering the CCBs, solar radiation was decreased
and chlorine residual increased. Controlling these factors was expected to decrease the algal growth in the CCBs.
Two different studies were performed in order to account for these changes: a pilot study and a full-scale study.
The pilot study did not show any significant influence of solar radiation in the opaque and transparent basins. It
did show, however, that chlorophyll a was immediately degraded after the addition of chlorine. From the full-
scale study, 6 out of the 9 samples analyzed showed a difference in chlorophyll a concentration. The
average difference was 21.6% lower for the covered basin. Despite this decrease, the data did not provide
statistical evidence to prove that the difference was significant. Similarly, there was no significant difference in
total suspended solids (TSS) concentration, and therefore the suggestion that algae formation would be lowered
in the covered basin could not be supported. Even though statistical tests resulted in poor evidence, trends
on increased solar radiation and chlorine concentration were found to have some influence in the chlorophyll
The Kanapaha Water Reclamation Facility (KWRF) is an advanced wastewater treatment plant operated by
Gainesville Regional Utilities (GRU) that serves the northwest and southwest areas of Gainesville, Florida. KWRF
was opened in 1977 and has a current permitted capacity of 14.9 million gallons per day (mgd). The plant treats
the wastewater to drinking water standards and most of the water effluent is used for irrigation, reuse, and
injection into groundwater. This plant consists of the following processes: preliminary treatment, sludge
thickening facility, anoxic basins, aeration basins, secondary clarifiers, a mixed liquor splitter box, Severn-
Trent filters, an RAS/WAS (return activated sludge and waste activated sludge) pumping station, a post
aeration basin, and chlorine contact basins. These processes are shown in an aerial view in Figure 1, and a
process flow diagram is presented in Figure 2.
Figure 1. Aerial View of the Kanapaha Water Reclamation Facility (2004)
Chapman's Pond Anoxc Anexic
. Bas Basin ,
- Basin Basin
Waste Sludge Digesters
Hauling / -------------
- Filers 1&2
Deep Well Locason
Injection Chlorine Contact Basins
Rause 3 Post-
Chorine addiion |
Figure 2. Process Flow Diagram of Kanapaha Water Reclamation Facility
In order to achieve the high standard goals that KWRF has set, disinfection is an important part of the
treatment process. The disinfection process is carried out in two chlorine contact basins (CCBs) that are opened
to the atmosphere and exposed to sunlight. Preliminary investigations carried out by a team of the
Integrated Product and Process Design (IPPD) have indicated that sunlight has a number of adverse effects on
the disinfection efficiency in the CCBs. One of these adverse effects is the algal formation in these basins.
The presence of algae in these basins was visually confirmed by the IPPD team after an inspection inside one of
the CCBs that was not operating at the time.1 By looking at the clarifiers, significant algal formation can be
observed, as shown in Figure 3 below, which is a picture of one of the actual clarifiers. Chlorination does not seem
to completely remove this algal growth, since algae is still found in the CCBs.
Figure 3. Algae Formation in the Clarifiers at KWRF
Most algae are phototropic organisms that can fabricate their own food materials through photosynthesis by
using sunlight, water,and carbon dioxide. Most algae contain chlorophyll a, a molecule that absorbs the light
to enable photosynthesis. Chlorophyll a absorbs light in the blue (450 nm) and red (650 nm) wavelengths, as
shown by the two peaks in Figure 4, and emits light in the green wavelength.2
Absorption Spectrum of
60 56 6 00 66
Figure 4. Absorption spectrum of chlorophyll a
(Steer, James. Structure and Reactions of Chlorophyll)
Some of the negative consequences of algal formation in the CCBs are:
* Formation of disinfection byproducts (DBPs) from chemical releases of algae during chlorination
* Formation of solids at the bottom of the basins that can interfere with the chlorine efficiency.
In addition to the formation of algae, other aspects of concern in KWRF are the DBPs and haloacetic acids
(HAAs) formation related to chlorination. The form of chlorine used for the disinfection process is chlorine gas,
which is known to react with naturally occurring organic matter in wastewater to form DBPs. Similarly, the loss
of chlorine residual in the CCBs is a potential problem that directly affects the cost of disinfection. These aspects
were investigated by Heather Fitzpatrick, a graduate student in the department of Environmental
Engineering Sciences for her thesis project.
The study was conducted at the KWRF, and it consisted in two parts: a pilot study and a full scale study on the
CCBs. For the pilot study, two chlorine contact basins of 10.12 ft3 capacity each were built. One of them was
covered with a UV-transmitting clear acrylic cover that allowed the penetration of both visible and UV radiation,
to resemble the actual conditions in the treatment plant. The other basin was covered with a dark plastic top
to prevent from direct sunlight irradiation. These two basins are referred to as transparent and opaque,
respectively. The pilot study was set up in the area between the clarifiers and the filters as indicated in Figure 2.
The influent water for the pilot basins was coming from the clarifiers' effluent, and the experimental basins
and instrumentation were set up as shown in Figure 5. Chlorine, in the form sodium hypochlorite (NaOCI,
household bleach), was added steadily to the basins at different concentrations, hydraulic retention times (HRT)
and wastewater flow rates. Chlorine concentrations ranged from 6 to 16 mg/L. Sulfuric acid was added in
some occasions to keep the pH around neutral or lower, since it was expected to increase because of the basic
form of chlorine used. The maximum retention time applied was 3.81 hours, while the average HRT used for most
of the runs was 2.75 hours.
Field Sample Analysis and
Inlet Watar From
Figure 5. Pilot Study Schematics
The full-scale study consisted of covering one of the actual CCBs in KWRF with a tarp to prevent solar radiation
while leaving the other CCB open to the atmosphere in order to assess changes influenced by sunlight.
This paper presents a study on the interactions of algae with different factors including solar radiation
and chlorination, as well as its effects in the chlorine dosing concentration. Similarly, other factors such as
total suspended solids (TSS) are correlated to chlorophyll a concentrations to assess the presence of algae in
1. The formation of chlorophyll a is expected to be favored by the presence of higher solar radiation in direct
contact with the wastewater. This would correspond to a higher chlorophyll a concentration in the uncovered basin
as compared to the covered one.
2. The concentration of chlorine is expected to decay by UV irradiation as described by Equation 1. Therefore,
lower chlorine concentrations are anticipated for the uncovered basins than for the covered CCBs.
3. Chlorination is expected to reduce the formation of algae, so at higher chlorine concentrations, the formation of
algae is expected to be lower.
4. Algae concentrations and total suspended solids are expected to have a positive correlation.
Because of its importance in the photosynthetic process that algae undergo, sunlight can help predict the
productivity of algae. Sunlight was measured as solar radiation. The solar radiation and terrestrial radiation can
be divided in different wavelength ranges: ultraviolet (.2-.39 pm), visible (.39-.78 pm), near-infrared (.78-4.0
pm) and infrared (4.0-100.0 pm). Most of the solar radiation is contained in the region from 0.3 pm to 3.0 pm.
The global horizontal solar radiation is part of the solar radiation, and it is composed by two components of
sunlight falling together on a horizontal surface, i.e., the component of sunlight and the diffuse component
of skylight. Global horizontal radiation was measured by a Black and White Pyranometer (Model 8-48) and
ultraviolet radiation by a Total Ultraviolet Radiometer (Model TUVR), respectively, both manufactured by the
Eppley Laboratory, and they are shown in Figures 6 and 7. The pyranometer captures energy in the
wavelength range between 0.285 to 2.8 pm while the radiometer is limited to the wavelength interval from 0.295
to 0.385 pm. The measurements collected by these instruments were recorded by a data logger every five minutes
in units of mW/cm2.
Figure 6. Black & White Pyranometer
Figure 7. Total UV Radiometer
Sample Collection and Preservation
For the case of the pilot study, samples were collected at 3 different locations during 8 days. The sampling
locations are labeled in Figure 5 with number 1 representing the effluent coming from the clarifier (5INT), number
2 the effluent from the transparent CCB (5TRU), and location 3 the effluent from the opaque CCB (5TRC).
The samples were taken at 3 different times of the day: 9:00 am, 12:00 pm, and 2:00 pm to allow enough
detention time between sampling. The collected samples were preserved in a cooler with enough ice to keep
the samples cold until the time of analysis in the lab.
During the full-scale study, two samples were collected from the filter effluent, samples labeled Filter 1 and Filter
2 (locations 1&2, Fig. 2), one sample was collected at the post aeration effluent, 5PA, (location 3, Fig.2), one at
the influent of the chlorine contact basins, right after chlorination, 58S, (location 4, Fig.2), and two samples
were collected at the CCBs effluent, one from each basin, the covered, 53N (location 5, Fig.2) and the
uncovered one, 53S (location 6, Fig.2). The samples were collected for 3 days at the same times as the pilot
study and preserved in a similar manner.
The parameters analyzed in the field were chlorine residual, pH, water temperature, conductivity, and
dissolved oxygen. The other parameters such as chlorophyll a concentration, THMs, and HAAs were analyzed in
the lab. The total suspended solids were analyzed by the KWRF lab.
As mention above, field sampling analysis included the chlorine residual measurement, total and free
chlorine residual, which was analyzed with a Portable Datalogger Spectrophotomer, Model DR/2010 (UF #
4910AA 151134), manufactured by Hach Company. The other parameters measured were obtained using
different portable meters calibrated in advance in the lab.
Algae samples were analyzed using the Method 445.0, a standard method proposed by the Environmental
Protection Agency (EPA) for the determination of chlorophyll a in marine and freshwater algae. A detailed
description of this method is attached in Appendix A. Method 445.0 uses the principle of fluorescence, a
physical property that allows certain atoms and molecules to absorb light energy at one wavelength when they are
in an excitation state, and instantaneously re-emit light energy at another wavelength when they return to
their ground state, since the chlorophyll a molecule has this ability.
The samples of water obtained from the wastewater treatment plant were slowly filtered through a glass fiber filter
of 47mm manufactured by Whatman Company. The filters, together with a 90% acetone solution used to extract
the pigment from the phytoplankton, were then placed in a mechanical tissue grinder where they were
macerated. The resulting filter slurry was allowed to steep for a minimum of 2 hours, and in most of the cases for
24 hours in the dark at 40C to ensure complete extraction of the chlorophyll a. The samples were later centrifuged
for 15 minutes and the clear solution was immediately placed in a glass cuvette to measure the fluorescence in
a fluorometer. The fluorometer used was the Laboratory Fluorometer Model TD-700 (UF # 4910AA) manufactured
by Turner Designs.
The fluorometer was previously calibrated by using the Multi-Optional Mode-Direct Concentration
calibration procedure, which provides the actual unknown concentration directly without using any conversions.
The calibration curve obtained showed linearity in the range of 0 to 45 pg/L of chlorophyll a. Assuming this
linearity range, the samples were diluted so that all of them fell within these values. To assess the quality of
the method, a quality control test was run. This test consisted of four samples obtained at 9:00 am from
the clarifier's effluent (location 1, Fig. 5). According to the Method Detection Limit (MDL) performed in these
samples, the lowest detected chlorophyll a concentration corresponded to a value of 0.029 pg/L. Adopting this
value as the lowest possible accurate chlorophyll a concentration, all of the samples included for the analysis
were only considered valid if they were above the lowest detection value.
RESULTS AND DISCUSSION
Pilot Scale Study
The pilot study results showed that the concentration of chlorophyll a dramatically decreased from
the influent to the pilot CCBs after the chlorine was added. The concentrations of chlorophyll a
obtained at location 1 in Figure 5, which corresponds to the clarifier's effluent, were very high
as compared to the concentrations obtained from locations 2 and 3 (Figure 5) that represent the
CCBs effluent. As shown in Figure 8, samples 5TRU and 5TRC (transparent and opaque
basins, respectively) were 74% to 98% lower in chlorophyll a concentration than the 5INT samples.
$INT - Clarifier Effluent
J 5TRU - Transparent IBa~i
STRC - Opaque Basin
Figure 8. Chlorophyll a concentrations for all samples taken during the pilot study
It is possible to infer that chlorine adversely interacted with chlorophyll a to create such decay
in concentration. These results were further supported by the concentrations obtained for the
TSS samples taken at the same times and locations. A minimum of 25% and a maximum of 97% of
TSS reduction were recorded in these basins.
The results from this study concord with trends from previous findings on the effects of chlorination
and algal formation. For example, Cadwell reported that an algal removal of 64% was accomplished in
a 14-hour detention chlorine-contact pond when the applied chlorine dose was 12 mg/L.3
Similarly; Bowen also observed reductions of TSS as a result of chlorination. Except during winter
periods of unusually high chlorine demand, when a residual of approximately 2 mg/L was maintained
in the effluent of the Peterborough, New Hampshire oxidation ponds system, an average reduction
of 53% of TSS between the point of chlorination and the point of discharge from the contact basin
Even though the decrease of chlorophyll a after chlorination in the basins was anticipated, the
percent reduction was unexpectedly high. Further studies were carried out to investigate
this phenomenon more in depth. Laboratory experiments were run to observe the chlorophyll a
reduction after chlorination as a function of time and investigate whether the decrease was the result
of the interaction of chlorine bleaching the chlorophyll a thereby producing such a low
fluorescence reading. Standard chlorophyll a solutions at different concentrations (8.64, 21.6, 43.2
and 64.8 pg/L) were exposed to a chlorine dose of 8 mg/L. The results obtained from this experiment
are shown in Figure 9.
& 3 60 8 -- i,9- qfl! .
A 50 2 1.6>i.9LCr.lnF?
E 40 - 43.2 ,.gL Cil a
S 30 6 ,a .B L qnIL a
0 2 4 6 10
Time after chlorine addition (min)
Figure 9. Fluorescence Reading for Chlorophyll a concentration versus time measured after
The chlorophyll a concentration decayed immediately after the first minute of the chlorine addition
and the concentration became then steady. Figure 9 shows this steady state to continue after 10
minutes of contact with chlorine. The same steady state concentrations were recorded for samples
taken every hour for the next 5 hours, and after 24 hours. The results indicate that there is
an instantaneous reaction occurring between chlorophyll a and chlorine. For a constant chlorine dose of
8 mg/L, there seems to be a higher chlorine demand for higher concentrations of chlorophyll than for
the lower ones. The chlorine demand was estimated to average 0.56 mg of C12/mg of chlorophyll a
for the higher chlorophyll a standards corresponding to 64.8 pg/L and 43.2 pg/L. For the
lower concentrations of chlorophyll a (8.64 and 21.6 pg/L), the chlorine demand was 0.16 mg of CI2/
pg of chlorophyll a. Because only one dose of chlorine was tested, it cannot be concluded that there is
a specific value for chlorine demand by chlorophyll a. However, it can be suggested that
higher concentrations of chlorophyll a will require higher chlorine doses. On the other hand, there
should be an optimum chlorine demand to reduce chlorophyll a concentrations since these values do
not completely decay to zero.
Despite the fact that the pilot study data showed good evidence to confirm the decay of chlorophyll
a after the chlorine addition, it is not possible to infer anything about actual algal formation.
The results obtained confirm possible effects of chlorination on chlorophyll a; however, the pilot
study did not provide enough evidence to compare the extent to which the sunlight irradiation
affected the algal formation in the basins. The transparent and opaque basins did not show
significant difference in chlorophyll a concentration, and the concentrations were too low for
comparison. In many instances the opaque basin resulted in higher concentrations than the
transparent basin which was not expected. This phenomenon can be explained by chlorine having such
a high effect on the decrease of the chlorophyll a concentration that causes the retention time in
the basins, either exposed to the solar radiation or not, not to have much effect for new algal growth.
The concentration of chlorophyll a was not high enough after chlorination to account for any
productivity that might be attributed to the solar radiation.
The full-scale study results for the chlorophyll a concentrations provided a sequential description of
the algal formation throughout the different processes in the treatment plant. Figure 10 shows
the average chlorophyll a concentration at different locations of the wastewater treatment plant for
the full-scale study. The concentrations from one sampling day to another may vary slightly, but
they presented the same trend, with few exceptions discussed later in the section. As observed in
the figure below, the water coming from the clarifiers has a high chlorophyll a concentration (Filter 1
and Filter 2). The SPA samples, representing the post aeration basin effluent, are significantly lower
in chlorophyll a concentration. It can be concluded from these samples that the filters perform
optimally in removing most of the algae because the chlorophyll a concentration in the water
after passing through the filters decreased dramatically. When the water leaves the post aeration
basin to enter the CCBs, chlorine is injected into the water flow in pipes that are underground.
Samples 58S, taken right after the chlorine addition at the inlet of the CCBs are even lower in
chlorophyll a. This decrease supports the hypothesis that chlorination significantly reduces chlorophyll
a concentration in very short periods of time, demonstrated earlier by the pilot study. Samples 53S
and 53N represent the effluents from the uncovered and covered CCBs, respectively. The chlorophyll
a concentrations slightly increased from the influent to the effluent of the CCBs. Chlorophyll
a concentration was found to increase in both covered and uncovered basins. However, the chlorophyll
a found in the covered basin turned out to be lower than the one found in the uncovered one,
a 0 Filter I
0 3 I I5PA
9:00 12:00 14:00
Time of Day (hr:min)
Figure 10. Average Chlorophyll a concentration versus time of day for all samples taken during the 3
Out of the 9 samples collected from the CCBs effluent during the full-scale study, 3 of them did not
follow the expected trend, chlorophyll a concentrations from the covered basin were higher than
the uncovered basin. Figure 11 shows more clearly the difference in the two CCB effluent samples
(53S-Uncovered vs. 53N-Covered). Two of the samples that were higher in the covered basin
and accounted for the largest difference in the samples were obtained at 9:00 am. As observed in
Figure 11, the average of the 3 samples taken at 9:00 am is lower in chlorophyll a concentration for
the covered basin than for the uncovered.
S 0.4 5PA
9:00 12:00 14:00
Time of Day (hr:min)
Figure 11. Average Chlorophyll a concentration versus time of day for samples taken during the 3 days
of full-scale study. Same as Figure 10 excluding the filter samples to give a better view in the
lower concentration differences.
The mean chlorophyll a concentration found in the uncovered CCB was 0.264 pg/L as compared to
0.207 pg/L of the covered CCB (Fig.12). The lower chlorophyll a concentrations in the covered CCB
can be attributed to two main factors: the decrease in solar radiation reaching the basin and the
increase in chlorine residual.
Uncovered Basin Covered Buin
Figure 12. Average chlorophyll a concentration for the covered and uncovered chlorine contact basins at
Covering the basin with the tarp reduced the direct penetration of solar irradiation to the basin.
The lower availability of light might have diminished productivity of algae in the cover basin as
compared to the uncovered one. The difference in chlorophyll a concentrations from the covered basin
to the uncovered as they relate to the UV radiation and global horizontal solar radiation are presented
in Figures 13 and 14, respectively. Higher differences in chlorophyll a positively correlate to higher
solar radiation, so it can be inferred that the lack of solar radiation influenced the decrease of
chlorophyll a formation in the covered basin.
0.0 0.1 0.2 0.3
AChIa Concentration (Unc-Cov)
Figure 13. Difference in chlorophyll a concentrations (Uncovered CCB - Covered CCB) versus the
average UV radiation.
-I l 53S-Unc
0_ * N-Co%
-0.20 -0.10 0.00 0.10 0.20 0.30
hi(6 a Concentration (Uncovered - Covered)
Figure 14. Difference in chlorophyll a concentrations (Uncovered CCB - Covered CCB) versus the
average global horizontal solar radiation.
Preventing the basin from solar radiation did not only decrease the algal formation, but it also
increased the chlorine residual as predicted by equation 1. This hypothesis was tested and proved
by Heather Fitzpatrick during the analysis of the chlorine samples for her thesis project.5 As shown
in Figure 15, the difference in the chlorine residual of the covered basin as compared to the
uncovered basin increases as the UV radiation increases. This shows that the chlorine residual in
the covered basin is larger than in the uncovered one.
0.5-* Frcc Chlorine
0J ï¿½ .0 * I * Total Chlorin
* e .|-l 1 , LO 2.0 O,0 4.01 5,0
Average UV Radiation
Figure 15. Difference in chlorine residual concentration (Covered CCB - Uncovered CCB) versus
the average UV radiation.
The availability of more chlorine residual in the covered basin might have impeded the growth of algae
in the CCB. Since the chlorophyll a concentration is expected to be lower in the covered basin,
the difference between covered and uncovered basins should be negative. As presented in Figure 16,
this appears to be the case for most samples. Similarly, chlorine residual being higher for the cover
basin has a positive difference when compared to the uncovered basin. It can be observed from Figure
16 that most of the data points cluster on the second quadrant of the graph, meaning that
negative differences in chlorophyll a (lower chlorophyll a for the covered basin) relate to
positive differences of chlorine residual (higher chlorine for the covered basin). Therefore, it can
be suggested that lower chlorophyll a concentrations related to higher chlorine residual.
-0 2 4 1 1 3 QI O A o F r e e C l R e sd u a l
AChloroph~Ih~on centrAI 6)n (Cov - Unc)
Figure 16. Difference in chlorine residual concentration (Covered CCB - Uncovered CCB) versus
the difference in chlorophyll a concentration (Cov-Unc).
Even though the percent difference in the average chlorophyll a concentration of the covered basin
was 21.6% lower than the uncovered basin (Fig.12) and possible reasons for this occurrence have
been addressed above, a significance test, the Mann-Whitney test, performed on the data did not
provide enough evidence to say that this difference was significant (a = 0.10)
Similar to the chlorophyll a analysis, TSS samples were examined in the intent to prove the
hypothesis that algal formation would be decreased by covering the CCB. The average TSS
concentrations found in the different basins for the full scale study are presented in Figure 17, and
these are 0.356 mg/L and 0.367 mg/L for covered and uncovered basin, respectively. This difference
is very small, and as it would be expected from such a small difference, no significant evidence
resulted from this analysis. Using a t-test for this data resulted in insufficient evidence to
demonstrate that the TSS concentration in the covered basin was lower than in the uncovered basin.
Figure 17. Average total suspended solids (TSS) concentration in the covered and uncovered
chlorine contact basins at KWRF.
As demonstrated by the pilot study, chlorine influences chlorophyll a concentrations. It was
observed that this reaction takes place in a very short period of time. The actual chemistry involved
in this interaction has not been well defined. However, it is possible to confirm with certainty that
adding chlorine to wastewater decreases chlorophyll a concentrations dramatically. Even
though chlorophyll a is used as a measure of algae productivity, it is not possible to say that
the reduction in chlorophyll a directly relates to a decrease in algal formation because of the
bleaching effect of chlorine on the chlorophyll a that resulted in very low fluorescence readings.
The resulting TSS reduction in the pilot CCBs could suggest that chlorination did influence
algal formation; however, not specific correlation between chlorophyll a and TSS reduction was found
as it was expected at the beginning of the study.
The full scale study provided a thorough description of the chlorophyll a concentrations
throughout different processes in the treatment plant. From these results it is possible to infer that
as the wastewater moves from the clarifiers through the filters, a significant amount of algae is
removed, and this concentration is further reduced when the chlorine is injected to the wastewater.
After chlorination occurs, the retention time in the CCBs allows for additional algal development.
The extent to which either sunlight or chlorine residual influences this algae growth in the CCBs could
not be significantly assessed. Statistically significant evidence was not found in order to predict
whether a decrease in sunlight or an increase in chlorine residual would reduce the algal formation in
the CCBs. Therefore, it is not possible to say that covering the CCBs at the KWRF would
significantly reduce the algal formation. It has been suggested however, that chlorination would have
an effect in algae growth, so it might be possible that keeping significantly higher chlorine
residuals would decrease the concentration of algae. Additional studies would be necessary in order
to further prove actual interactions of chlorine and algae, as well as the influence of sunlight in this
1. Integrated Product and Process Design Team. "The effect of chlorine residual on disinfection by-
product formation in the Kanapaha Water Reclamation Facility chlorine contact basin". University
of Florida (2001-2002).
2. Kirk, John T.O. Light and photosynthesis in aquatic ecosystems. Cambridge University Press (1983).
3. Caldwell, DAHL. "Sewage oxidation ponds". Sewage Works Journal 18:3 (1946)
4. Bowen, ESP.. "Performance evaluation of existing lagoons, Peterborough, New Hampshire". U.
S. Environmental Protection Agency, Cincinnati, Ohio. EPA-600/2-77-085 (1977)
5. Fitzpatrick, Heather. Covering chlorine contact basins at the Kanapaha Water Reclamation
Facility: effects on chlorine residual, disinfection effectiveness, and disinfection by-product formation.
M.S. Thesis. University of Florida. Gainesville, Florida (2004).
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