PART B: BOD DETERMINATION OF WASTEWATER
INTRODUCTION
According to Penn. M. R., (2009), one of the most common approaches in quantifying water pollution is by BOD. Biochemical Oxygen Demand (BOD) can be defined as the total oxygen amount that being uptake by bacteria from water when they oxidize organic matter and it was expressed in parts per million (ppm) or mg/L (Lee. J. H., 2000 ). Organic matters that get into the water may either being totally dissolved or suspended as particulate matters. Bacteria live and continuously growth in the water when there are oxygen for oxidation and organic matter as food. Human beings, animals and also bacteria oxidized organic matter by burning with presence of oxygen, by digestion or by biochemical action of bacteria. Normally, to determine the BOD of a water sample, the amount of oxygen used by the bacteria is calculated by comparing the amount left at the end of five days with the amount known to be present at the beginning. During the five day period, bacteria oxidize mainly the soluble organic matter present while very little oxidation of the insoluble matter occurs (Liu. J., 2002). BOD measurement has long been the basic means for determining the degree of water pollution. It is the most important measurement made in the operation operation of a sewage treatment plant. Basically, Vaiopaolo. E., (2005) study mentioned that the efficiency and effectiveness of sewage treatment can be examined by comparing the BOD of incoming sewage and the BOD of effluent water that leaving the plant. If water with high BOD value flows into a river, the bacteria in the river will oxidize the organic matter, consuming oxygen from the river faster than it dissolves back in from the river and this will result in dying of aquatic life from lack of oxygen. Thus, sewage treatment plants must remove as much BOD as possible from the sewage water. BOD of wastewater is typically 110-440mg/L and must be reduced to 20mg/L for discharge. There are two terms that commonly used in BOD which are BODu and BOD5. BODu measure the amount of oxygen usage by microorganisms over a long period of time. Meanwhile, BOD5 is the common approach in laboratory where it calculate the amount of oxygen consumed in mg/L over a 5 day period at 20̊ C in dark environment. In other words, BOD5 is a measure of
the bioavailability over a 5 day period under controlled conditions. The formula to calculate BOD of water sample is as below:
=
( − )
Where, Di
=
initial dissolved O2 concentration
Df
=
final or 5 day dissolved concentration
P
=
volumetric fraction of wastewater
=
() ′ ()
OBJECTIVES
The objectives of this studies are to assess the quality of surface waters. Besides, to determine the amount of dissolved ox ygen in waste water samples. The studies are to establish the concentration of organic matter in waste water samples. Lastly, to understand the characteristics of DO contained in water and wastewater.
PROCEDURES
Determine the wastewater sample source.
Firstly, the sample of wastewater was taken from the drain outside the campus of UniKL MICET using the bottle provided from the lab. Next, 200 mL of the sample was placed into 300 mL BOD bottle.
Addition on nitrification inhibitor.
After that, 0.16 g of nitrification inhibitor was weighed and added into the samples. Nitrification inhibitor also also known as BOD inhibitor purposely to eliminate the nitrogen and carbon dioxide inside the sample. Next, 100 ml of dilution water was refilled back into the sample and stirred them very slowly.
Record the initial and final DO level (ppm) of the sample.
The sample was then recorded the initial DO level (ppm) using the DO meter, and was place in an incubator at temperature of 20oC in about 5 days. On day 5, the final DO reading (ppm) was checked and recorded.
Calculate the BOD 5 of your wastewater samples.
Lastly, the BOD5 level was determined using equation below:
RESULTS AND DISCUSSION
For the second part which is Part P art B, biochemical oxygen demand (BOD) determination of wastewater, the biochemical oxygen demand (BOD) test measures the ability of naturally occurring microorganisms to digest organic matter in a five day incubation at 20oC by analyzing the depletion of oxygen. This measures biodegradable organic matter. The sample is filled in an airtight bottle and the dissolved oxygen (DO) content of the sample is determined before an d after five days of incubation. The BOD is calculated from the difference between initial and final DO as shown in Appendix.
Table 2.2: Data collected for Group 1 (Drained water from ADTEC) Parameters
Results
pH (Initial)
5.99
pH (Final)
6.67
DO (Blank)
8.29 Dilution (50 ml)
Dilution (100 ml)
Dilution (150 ml)
DO (Initial)
7.76
7.34
6.90
DO (Final)
5.72
3.16
2.42
P
0.167
0.333
0.50
BOD5
12.22
12.55
8.95
Table 2.3: Data collected for Group 2 (Drained water from UNIKL MICET) Parameters
Results
pH (Initial)
6.11
pH (Final)
6.67
DO (Blank)
8.29 Dilution (50 ml)
Dilution (100 ml)
Dilution (150 ml)
DO (Initial)
7.92
7.19
6.73
DO (Final)
5.62
2.93
2.71
P
0.167
0.333
0.50
BOD5
13.77
12.79
8.04
Table 2.4: Data collected for Group 3 (Drained water at junction of UNIKL MICET) Parameters
Results
pH (Initial)
6.92
pH (Final)
6.92
DO (Blank)
8.29 Dilution (25 ml)
Dilution (50 ml)
Dilution (100 ml)
Dilution (150 ml)
DO (Initial)
7.85
7.29
6.49
5.57
DO (Final)
5.03
3.55
3.74
3.95
P
0.083
0.167
0.333
0.50
BOD5
33.98
22.40
8.26
3.24
Table 2.5: Data collected for Group 4 (Drained water at UNIKL MICET) Parameters
Results
pH (Initial)
5.66
pH (Final)
6.78
DO (Blank)
8.29 Dilution (50 ml)
Dilution (100 ml)
Dilution (150 ml)
DO (Initial)
7.84
7.36
6.75
DO (Final)
6.68
4.92
4.22
P
0.167
0.333
0.50
BOD5
6.95
7.33
5.06
Table 2.6: Data collected for Group 5 (Drainage UNIKL MICET) Parameters
Results
pH (Initial)
5.93
pH (Final)
6.56
DO (Blank)
8.29 Dilution (50 ml)
Dilution (100 ml)
Dilution (150 ml)
DO (Initial)
7.84
7.43
6.89
DO (Final)
5.14
2.01
3.16
P
0.167
0.333
0.50
BOD5
16.17
16.28
7.46
There were five wastewater samples tested for BOD as stated. The initial pH for all samples were measured and adjusted between 6.6 and 7.2. As stated in references (Pauer et al ., ., 2013), the sample should have a neutral pH value of between 6.6 and 7.2 because microorganisms they require an environment that is suited to their species and in the purification of biological wastewater, based on the final pH value of both samples, it can be accepted. Besides, the dissolved oxygen for initial for the following dilution became increased for all of the samples. As the dilution of the samples increased, the concentration of dissolved oxygen, DO decrease due to a high demanding of oxygen from microorganisms. But after five days of incubation, DO final became decreased from the DO initial. This shows that the reduction of d issolved oxygen happened in the sample where microorganisms uptake the oxygen. This can be proven when low DO readings signify high oxygen demand from microorganisms, and can lead to possible sources of contamination depending on the process (Anonymous, 2010). The BOD5 level was calculated as shown in Table 2.2 until Table 2.5. From the observations, the BOD for all samples became d ecreased as the dilution of the samples increased. The lower the BOD value, the polluted the sample. A higher BOD indicates a high content of easily degradable organic material in the sample. While, a low BOD indicates a low volume of organic materials substances which are difficult to break down. In addition, a several dilutions are to be used to ensure that at least one will deplete the oxygen content by b y about 50%. For BOD value at least 2 mg/L of oxygen should shou ld be consumed with at least 1 mg/L remaining. If this condition is not found in any of the dilutions used, a wider range of dilutions must be selected for the examination of succeeding samples (Anonymous, 2010). Therefore, sample for Group 3 has a higher BOD5 level which is 33.98 ppm for first dilution. Besides, according to the reference, when the BOD5 level reach 100 ppm or greater than 100 ppm, the wastewater quality is very polluted, while if the BOD5 level is between 6 to 9 ppm, the wastewater quality is somewhat polluted. Hence, the BOD5 level of the last dilution for all samples were between 6 to 9 ppm which it shows that all the wastewater samples quality for last dilution were somewhat polluted. . In this experimental, it is found that the BOD5 value for Group 3 (Drained water at the junction of UNIKL MICET) is lower than Group 4 (Drained water at UNIKL MICET) which means that wastewater of Group 3 is more polluted compared to wastewater of Group 4. Therefore, the the lower the BOD5 value, the polluted the sample. The
oxidation of nitrogen from ammonium to nitrate by specific bacteria is called nitrification. The nitrification inhibitor blocks or toxifies the specific bacteria that are responsible for the degradation of the ammonium without damaging the microorganisms that degrade carbon compounds. Consequently, an inhibitor is added to the measurement solution to prevent the conversion of ammonium to nitrate.
CONCLUSION
The determination of Biochemical Oxygen Demand (BOD) is used in studies to measure the self-purification capacity of streams as a means of checking on the quality of effluents discharged to stream waters. The dissolved oxygen (DO) value for all samples were reduced after five days due to the microorganisms have uptake the oxygen in the samples. Hence, the DO recorded after 5 days incubation shows a decreasing results. In this experimental, it is found that the BOD5 value for Group 3 (Drained water at the junction of UNIKL MICET) is lower than Group 1 (Drained water from ADTEC) which means that wastewater of Group 3 is more polluted compared to wastewater of Group 4. Therefore, the lower the the BOD5 value, the polluted the sample. The dissolve oxygen and biochemical oxygen demand of a wastewater sample were determined. Hence, the objective of the experiment was achieved.
REFERENCES
Michael R. Penn, James J. Pauer and James R. Mihelcic. (2009). Biochemical Oxygen Demand. Journal of Environmental and Ecological Chemistry. Vol II
Jun Ho. Lee and Ki Woong Bang. (2000). Characterization of Urban Stormwater Runoff. Journal of Water Research. Vol 34, issue 6 pg 1773-1780
Jing Liu and Bo Mattiasson. (2002). Microbial BOD Sensors for Wastewater Analysis. Journal of Water Research. Vol 36, issue 15 pg 3786-3802
M. Dular and J. Zagorc-Koncan. (1990). Evaluation of Wastewater Pollution. Water, Science and Technology Journal. Vol 22, issue 5 pg 247-252
Eleni Vaiopoulou, Paris Melidis and Alexander Aivasidis. (2005). Sulfide Removal in Watewater from Petrochemical Industries by Autotrophic Denitrification. Journal of Water Research. Vol 39, issue 17pg 4101-4109
