Reaction kinetics and validity of BOD test for domestic
wastewater released in marine ecosystems Submitted to: Prof. A. B.
Gupta Deptt. Of Civil Engg. MNIT, Jaipur Submitted by: T. Sunder
rami reedy 2012 PCE 5010 Deptt. Of CE MNIT, Jaipur Downloaded from
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CONTENTS : Introduction. Materials and methods. Results and
discussion. Observations. Summary and conclusions. Downloaded from
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Introduction : cities have resulted in faster growth rate. 17
coastal megacities covering about 25% of the world's population.
The availability of oxygen in the ocean is limited due to high
chlorides. The biochemical degradation rates are slower in salinity
water. BOD is a wet oxidation process, which follows first-order
kinetics. The values of kinetic rate constants are expected to
differ with varying salinities and temperatures. Research is
carried out using glucoseglutamic acid and domestic wastewater to
evaluate the impact of salinity on biodegradation of carbonaceous
waste at 20C and 27C. Inverse relationship between rate of
biodegradation and salinity. BOD exertion at 20C (5 days) and 27C
(3 days) for the marine environment is comparable at selected
salinities. Downloaded from CivilDigital.com
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Exertion of BOD is: 1. P H,osmotic conditions,salinity,o 2. 2.
temp.,time of incubation, seed acclimatization. k ranging from 0.1
to 0.6 per day at 20C for the domestic wastewaters (Thomann1974).
BOD for glucoseglutamic acid showed lower value in seawater than
that observed in freshwater. Finding the of BOD exertion of GGA and
domestic wastewater under specific salinities expressed in terms of
chloride concentrations at 20C and 27C. Downloaded from
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Glucoseglutamic acid solution with ultimate BOD (L) as 480 mg/L
Days Average BOD (mg/L) 0 mg/L chlorides 5,000 mg/ L chlorides
10,000 mg/ L chlorides 15,000 mg/ L chlorides 20,000 mg /L
chlorides 1107131724441 21832251586471 3213241225164158
4307265245194181 5337285255200221 6373295268214244 7380281282240248
8390315295264261 9395344324279271 10397350338300284 BOD of
glucoseglutamic acid solution exerted with varying chloride
concentrations in dilution media at 20C. Downloaded from
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Glucoseglutamic acid solution with ultimate BOD (L) as 480 mg/L
Days Average BOD (mg/L) 0 mg/L chlorides 5,000 mg/ L chlorides
10,000 mg/ L chlorides 15,000 mg/ L chlorides 20,000 mg /L
chlorides 12332351624233 2277254262215216 3333281282249240
4370344319249260 5420358346302280 6443368356315286 7440371359315296
8443381372322293 9451380375326302 10455396387329306 BOD of
glucoseglutamic acid solution exerted with varying chloride
concentrations in dilution media at 27C. Downloaded from
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Glucoseglutamic acid solution with ultimate BOD (L) as 480 mg/L
Chlorides (mg/L) BOD exerted at 20C on the 5th day, mg/L/percentage
BOD exerted at 27C on the 3rd day, mg/L/percentage 0336 (70%)334
(69.6%) 5,000285 (59.3%)281 (58.5%) 10,000255 (53.1%)282 (58.5%)
15,000200 (41.7%)249 (51.8%) 20,000221 (45.8%)240 (50%) Comparison
of BOD of glucoseglutamic acid solution exerted with varying
chloride concentrations at 20C on the fifth day and 27C on the
third day. Days Chlorides (mg/L) Day 1Day 2Day 3Day 4Day 5 Average
k k value for the reaction constant at 20C 00.250.240.200.250.24
5,0000.32 0.230.200.180.25 10,0000.160.200.210.180.150.18
15,0000.100.070.140.130.11 20,0000.090.080.130.12 0.11 Days
Chlorides (mg/L) Day 1Day 2Day 3 Average k Average values of k at
20C and 27C for glucoseglutamic acid. k value for the reaction
constant at 27C 00.670.430.400.50 5,0000.670.380.290.45
10,0000.410.400.300.37 15,0000.090.300.240.21
20,0000.070.300.230.20 Downloaded from CivilDigital.com
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Materials and methods : BOD, which measures oxygen requirement
for aerobic stabilization of the organic matter, is a bioassay
test. The natural seawater with 3536 parts per thousand (ppt) of
salinity has about 20,000 mg/L of chlorides. The experiments were
conducted for a 10-day period to achieve maximum exertion of
carbonaceous BOD. A cotton-filtered domestic wastewater was used as
"seed to provide a heterogeneous population of microorganisms. In
view of the fact that BOD exerted at 20C for 5 days is equivalent
to the BOD at 27C for 3 days. The incubated samples various time
slots were analyzed for the existence and adequacy of heterotrophic
microorganisms under various chloride concentrations using
Zobel/nutrient agar media. Downloaded from CivilDigital.com
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Results and discussions : the decomposition rate of organic
contaminants phenomenon occurs due to restriction of osmoregulatory
processes responsible for the breakdown of organic compounds within
the cells of microorganisms. According to the first-order equation
of chemical kinetics (Sawyer et al.2010), the rate of decomposition
is directly proportional to the amount of undecayed material and
may be mathematically expressed as = - sign indicates the loss of
material with time. = C is the concentration of oxidizable organic
matter. at the start of the time interval t. = K is the rate
constant. The BOD curve can be described by a first-order kinetics
equation (Metcalf and Eddy, Inc.2003) dL 0/dt = -k L 0 Downloaded
from CivilDigital.com
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y = Amount of oxygen consumed (or BOD) at time t t = Time
elapsed since the start of the assay L0 = Total amount of oxygen
consumed in the reaction (or ultimate BOD) k = Reaction constant
Domestic wastewater solution with ultimate BOD (L) as 300 mg/L
Chlorides (mg/L) BOD exerted at 20C on the 5th day, mg/L/percentage
BOD exerted at 27C on the 3rd day, mg/L/percentage 0167 (55.7%)168
(56.0%) 5,000103 (34.3%)127 (42.3%) 10,000115 (38.3%)126 (42.0%)
15,000103 (34.0%)104 (34.7%) 20,00094 (31.3%)110 (36.7%) Comparison
of BOD of domestic wastewater exerted with varying chloride
concentrations in dilution media at 20C on the fifth day and 27C on
the third day. Downloaded from CivilDigital.com
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Days Chlorid es (mg/L) Day 1Day 2Day 3Day 4Day 5 Averag e k k
value for the reactio n constan t at 20C 00.250.200.230.180.160.20
5,0000.15 0.120.100.080.12 10,0000.190.140.120.110.100.13
15,0000.220.150.120.100.080.13 20,0000.210.150.110.08 0.13 Days
Chlorid es (mg/L) Day 1Day 2Day 3 Averag e k k value for the
reactio n constan t at 27C 00.390.250.270.30 5,0000.270.190.180.21
10,0000.270.190.180.21 15,0000.250.200.140.20
20,0000.300.210.150.22 Average values of k at 20C and 27C for
domestic wastewater. The importance of the reaction rate constant k
for BOD was realized, and it was felt that k values must be known
for a particular environmental condition for proper evaluation of
ultimate BOD status. Downloaded from CivilDigital.com
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Coefficient of determination (r 2 ), a measure of the
proportion of variability in a data set that is accounted for by a
statistical model; often called R 2 ; equal in a single-variable
linear regression to the square of Pearson's product-moment
correlation coefficient. (The strength of the linear relationship
between the values).Coefficient of determination The better the
linear regression (on the right) fits the data in comparison to the
simple average (on the left graph), the closer the value of is to
one. The areas of the blue squares represent the squared residuals
with respect to the linear regression. The areas of the red squares
represent the squared residuals with respect to the average value.
Correlation coefficient (r), a broad class of statistical
relationships between two or more random variables or observed data
values. Correlation Downloaded from CivilDigital.com
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Chlorides (mg/L) Glucoseglutamic acid 20C27C Correlation
coefficient (r) Coefficient of determinatio n (r 2 ) Correlation
coefficient (r) Coefficient of determinatio n (r 2 )
00.9820.9650.9760.953 5,0000.9750.9510.9710.942
10,0000.9890.9790.9710.943 15,0000.9790.9580.9190.844
20,0000.9860.9720.8840.781 Domestic wastewater
00.9700.9410.9830.967 5,0000.9920.9840.9880.977
10,0000.9980.9950.9800.961 15,0000.9970.9940.9820.964
20,0000.9820.9650.9950.990 Values of r 2 and r for BOD of
glucoseglutamic acid and domestic wastewater under varying
concentration of chlorides. the two variables is the correlation
coefficient (r). A positive correlation states that increasing
values in one variable correspond to increasing values in the other
variable, while a negative correlation states that increasing
values in one variable correspond to decreasing values in other
variables. Values close to 1 indicate excellent linear reliability.
Linear regression gives the relationship between two variables, by
fitting the observed data into a linear equation. The square of the
correlation coefficient (r) is a useful value in evaluating linear
regression. Downloaded from CivilDigital.com
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Observations : BOD exertion was 10% to 15% higher at 27C as
compared to 20C for all media. With incremental increase in
chloride concentration, BOD exerted for conventional time and
temperature (20C, 5 day) dropped progressively from 70% to 46% for
glucoseglutamic acid solution and from 56% to 31% for domestic
wastewater.With incremental increase in chloride concentration, BOD
exerted for conventional time and temperature (20C, 5 day) dropped
progressively from 70% to 46% for glucoseglutamic acid solution and
from 56% to 31% for domestic wastewater. The values of BOD exerted
at 20C, 5 days, and 27C, 3 days.The values of BOD exerted at 20C, 5
days, and 27C, 3 days Sudden rise in BOD exertion was not observed
after the sixth or seventh day when oxidation of nitrogenous waste
is expected to start.Sudden rise in BOD exertion was not observed
after the sixth or seventh day when oxidation of nitrogenous waste
is expected to start Adequate microorganisms were present at higher
chloride concentrations for the whole test period at both the
temperatures. Existence, survival, and multiplication of microbes
were not the limiting factors for reducing the trend in BOD
exertion at various chloride concentrations.Adequate microorganisms
were present at higher chloride concentrations for the whole test
period at both the temperatures. Existence, survival, and
multiplication of microbes were not the limiting factors for
reducing the trend in BOD exertion at various chloride
concentrations. The k values had lowered with increase in chloride
concentrations. Significantly higher values for k were observed at
27C as compared to 20C indicating faster rate of oxidation at
elevated temperature.Significantly higher values for k were
observed at 27C as compared to 20C indicating faster rate of
oxidation at elevated temperature The values of the square of the
correlation coefficient (r 2 ) were negative and greater than 0.9
indicating good strength of the negative association between two
variables, i.e., degradation rate and chloride concentration. This
trend analysis indicates that as the chloride concentration
increases, the rate of degradation of organic matter decreases.The
values of the square of the correlation coefficient (r 2 ) were
negative and greater than 0.9 indicating good strength of the
negative association between two variables, i.e., degradation rate
and chloride concentration. This trend analysis indicates that as
the chloride concentration increases, the rate of degradation of
organic matter decreases. Downloaded from CivilDigital.com
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Summary and conclusions : Ten percent to 15% higher BOD was
observed at 27C when compared to 20C for all media. Negative impact
of chlorides on the oxidation of organic matter was observed
showing decrease in BOD exertion at higher chloride concentrations.
This observation permits adoption of BOD test at 27C with shorter
duration for saline waters. Nitrogenous oxidation was not observed
at selected test conditions till 10 days. How ever additional
oxygen will be required for nitrogenous BOD and needs consideration
while designing waste discharges. Availability of microbes was not
the limiting factor for reduction trend in oxidation of organic
matter at increased chloride concentrations. The values of k
reduced significantly at elevated salinities. the correlation
coefficient values. The values indicate decreasing trend in
degradation with increasing salinities. Downloaded from
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Those are indicated the necessity for critical consideration of
slow degradation rates while planning the disposal options for
organic wastes in the marine environment. Downloaded from
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References :
http://link.springer.com/article/10.1007/s10661-011-2341-
y/fulltext.html.http://link.springer.com/article/10.1007/s10661-011-2341-
y/fulltext.html Thom Ann, R. (1974). Systems analysis and water
quality management. New York: McGraw Hill.
http://en.wikipedia.org/wiki/Pearson_product-
moment_correlation_coefficient.http://en.wikipedia.org/wiki/Pearson_product-
moment_correlation_coefficient
http://en.wikipedia.org/wiki/Coefficient_of_determination.http://en.wikipedia.org/wiki/Coefficient_of_determination
OSPAR (2001) OSPAR convention for the protection of marine
environment of the North-East Atlantic. Meeting of working group on
priority substances (SPS [2] 01/4),ARONA (SECRETARIAT/EC): October
1519, 2001 Downloaded from CivilDigital.com
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Domestic wastewater solution with ultimate BOD (L) as 300 mg/L
Chlorides (mg/L) BOD exerted at 20C on the 5th day, mg/L/percentage
BOD exerted at 27C on the 3rd day, mg/L/percentage 0167 (55.7%)168
(56.0%) 5,000103 (34.3%)127 (42.3%) 10,000115 (38.3%)126 (42.0%)
15,000103 (34.0%)104 (34.7%) 20,00094 (31.3%)110 (36.7%) Comparison
of BOD of domestic wastewater exerted with varying chloride
concentrations in dilution media at 20C on the fifth day and 27C on
the third day. Downloaded from CivilDigital.com
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Glucoseglutamic acid solution with ultimate BOD (L) as 480 mg/L
Chlorides (mg/L) BOD exerted at 20C on the 5th day, mg/L/percentage
BOD exerted at 27C on the 3rd day, mg/L/percentage 0336 (70%)334
(69.6%) 5,000285 (59.3%)281 (58.5%) 10,000255 (53.1%)282 (58.5%)
15,000200 (41.7%)249 (51.8%) 20,000221 (45.8%)240 (50%) Comparison
of BOD of glucoseglutamic acid solution exerted with varying
chloride concentrations at 20C on the fifth day and 27C on the
third day. Domestic wastewater solution with ultimate BOD (L) as
300 mg/L Chlorides (mg/L) BOD exerted at 20C on the 5th day,
mg/L/percentage BOD exerted at 27C on the 3rd day, mg/L/percentage
0167 (55.7%)168 (56.0%) 5,000103 (34.3%)127 (42.3%) 10,000115
(38.3%)126 (42.0%) 15,000103 (34.0%)104 (34.7%) 20,00094 (31.3%)110
(36.7%) Comparison of BOD of domestic wastewater exerted with
varying chloride concentrations in dilution media at 20C on the
fifth day and 27C on the third day. Downloaded from
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Percent exertion of BOD for domestic wastewater at various
chloride concentrations at 20C. Percent exertion of BOD for
domestic wastewater at various chloride concentrations at 27C
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Counts/100 mL a Chlorides (mg/L) 20C27C 5 days10 days3 days10
days 047322718 5,00056449068 10,00017012511791 15,0002001477053
20,0001139810187 Total colony-forming units of heterotrophic
bacteria during different incubation periods at variable chloride
concentrations. All values to be multiplied by a factor of 10 8All
values to be multiplied by a factor of 10 8 Downloaded from
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Days Chlorides (mg/L) Day 1Day 2Day 3Day 4Day 5 Average k k
value for the reaction constant at 20C 00.250.200.230.180.160.20
5,0000.15 0.120.100.080.12 10,0000.190.140.120.110.100.13
15,0000.220.150.120.100.080.13 20,0000.210.150.110.08 0.13 Days
Chlorides (mg/L) Day 1Day 2Day 3 Average k k value for the reaction
constant at 27C 00.390.250.270.30 5,0000.270.190.180.21
10,0000.270.190.180.21 15,0000.250.200.140.20
20,0000.300.210.150.22 Average values of k at 20C and 27C for
domestic wastewater Downloaded from CivilDigital.com
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Chlorides (mg/L) Glucoseglutamic acid 20C27C Correlation
coefficient (r) Coefficient of determination (r 2 ) Correlation
coefficient (r) Coefficient of determination (r 2 )
00.9820.9650.9760.953 5,0000.9750.9510.9710.942
10,0000.9890.9790.9710.943 15,0000.9790.9580.9190.844
20,0000.9860.9720.8840.781 Domestic wastewater
00.9700.9410.9830.967 5,0000.9920.9840.9880.977
10,0000.9980.9950.9800.961 15,0000.9970.9940.9820.964
20,0000.9820.9650.9950.990 Values of r 2 and r for BOD of
glucoseglutamic acid and domestic wastewater under varying
concentration of chlorides. Downloaded from CivilDigital.com
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BOD exertion and values of coefficient of determination of
glucoseglutamic acid at 20C. BOD exertion and values of coefficient
of determination of glucoseglutamic acid at 27C. Downloaded from
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Percent exertion of BOD for domestic wastewater at various
chloride concentrations at 27C. BOD exertion and values of
coefficient of determination of domestic wastewater at 20C
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