Predicting Optimum Dilution Factors for BOD Sampling and Desired Dissolved Oxygen for Controlling Organic Contamination in Various Wastewaters

High biochemical oxygen demand (BOD) concentrations in water minimize oxygen availability, damage ecosystem biodiversity, impair water quality, and spoil freshwater. The increased level of BOD is an indication of severe organic pollution of freshwater. Thus, this study aims to establish empirical correlations between the 5-day biochemical oxygen demand (BOD 5 ) and organic decomposition time to control organic pollution in various wastewater eﬄuents. Ultimate biochemical oxygen demand (UBOD) and minimum and average BOD t data sets along with their reaction rates were collected from earlier sampling analyses in the plants used for industrial, domestic (sanitary), and storm (surface) wastewater treatment. Average BOD 5 /COD ratios were then utilized to calculate existing 5-day dissolved oxygen (DO 5 ) concentration for the estimation of experimental dilution factors (dfs) as a good start in sampling analysis to reach an optimum DO 5 concentration. Moreover, the relationships between average BOD 5 vs. COD, and BOD 5 vs. DO 5 , were obtained based on the literature with 60–70% oxygen consumption rates required for organic decomposition. Results showed that such BOD 5 relationships with time (power equations) or with COD (linear correlations) are helpful for wastewater engineers to generate valuable and accurate results for quality control, without the need to conduct laboratory experiments. The proposed regression equations would facilitate eﬄuent quality assessment, allowing selection of optimal processes to control microbiological contamination or organic constituents in wastewaters.


Introduction
Biochemical oxygen demand (BOD) is the oxygen demand of the organism to break down organic matter over a given period.Typically, organic pollution in freshwater bodies can be detected by the experimentally measured BOD levels from sampling analysis, which is directly correlated to microbiological contamination in sampled water [1].
e current projections of demographic growth and the increased demand for dairy products and consumption of meat prompted concerns regarding surface water quality due to the worsening of the global "sanitation crisis."Such climate change is expected because of the introduced sanitary issues in surface water bodies (especially rivers) that require reduction of discharge flows and/or dilution capability.BOD rates have been modeled on a global scale, which concluded that chemical wastes and organic discharges have a major impact on the world's economy if wastewater treatment progress is kept at current levels [2][3][4].
In Europe, a previous study projected an increase in organic pollution, especially in the southern countries, where most rivers have lost their dilution power as a result of the lack of dilution capacity of wastewater discharge in water-scarce areas.e study indicated that the eastern part of Europe and the Black Sea were to be more impacted by decreased river dilution capability and possible water quality deterioration [5].e BOD parameter was chosen by the United Kingdom (UK) in 1908 as an indicator of the organic pollution of rivers enforced by the UK "Royal Commission on River Pollution."e traditional five-day period to estimate the BOD 5 parameter was selected for this test because this is supposedly the longest time that river water takes to travel from its source to its delta (outlet end meeting a bay or an ocean) in the UK.Following that, the methods introduced in 1936 by the committee "American Public Health Association Standard" suggested using the BOD parameter as a reference indicator to evaluate the biodegradation of chemicals and hazardous substances.e use of the BOD 5 parameter arises due to three major applications: (1) it is an indicator for the conformity of the wastewater discharge and the waste treatment procedures with the current up-to-date regulations, (2) it is required to obtain the ratio of BOD 5 to chemical oxygen demand (COD) that would indicate the biodegradable fraction of effluent (discharge) from wastewater treatment plants, and (3) the ratio COD/BOD 5 is an indicator of the size of a wastewater treatment plant required for a specific location [6][7][8][9].
BOD 5 is the amount of oxygen that is consumed by bacteria and other microorganisms to be aerobically degraded in a water medium over a 5-day span at a standard temperature of 20 °C.erefore, the BOD 5 is an indirect metric method for quantifying existing organic or chemical wastes that are biodegradable in presence of oxygen in water, expressed in mg O 2 /L [10][11][12][13].BOD 5 indicates the amount of O 2 dissolved in mg/L that is required in a particular time for biodegradation of the components of organic water waste.
is value is an important parameter for the assessment of the degree of organic contamination that wastewater poses to the environment.e superficial flow of rainwater causes water to become contaminated, and this rainwater organic contamination can be analyzed by several parameters including BOD 5 .
e importance of this parameter value lies in the evolution of the degree of the contamination of environmental wastewater.Since the wastewater contents or constituents in the receiving water are decomposed by the bacteria present in it, the oxygen is either completely or partially withdrawn from the water to carry such organic pollutants degradation [6][7][8].
Two well-known methods are widely used for BOD measurement: (1) the dilution method, which is the most common and recent BOD measurement method based on the American Public Health Association (APHA) standards that have been certified by the US Environmental Protection Agency (USEPA), and (2) the manometric system, which has been commonly used in many sewage plants and other facilities around the world for over 75 years [14].However, the USEPA denied the approval of the latter method for wastewater analysis, although in certain cases the USEPA has approved the manometric method due to lack of data consistency and progress in associated laboratory techniques [15].In short, measuring BOD requires taking a minimum of two measurements, one measurement for the current (immediate) or initial dissolved oxygen (DO 0 ), and the second measurement is after incubation of water samples in the lab for 5 days to be then tested for the remaining amount of final 5-day dissolved oxygen (DO 5 ).Such experiments would allow us to quantify the amount of oxygen consumed by microorganisms to break down the organic matter present in the sample during the incubation period [10][11][12][13].
BOD is affected by the same factors that affect DO.High BOD-containing wastewaters will impact a minimum of 2.5 billion people by the year 2050.High BOD concentrations (e.g., 5 mg O 2 /L) in water minimize oxygen availability, degrade aquatic habitats as well as ecosystem biodiversity, impair water quality, and spoil freshwater [5].Sources of BOD include topsoil, leaves and woody debris, animal manure, and effluents from pulp and paper mills [10][11][12][13].
e high BOD loadings to freshwater and/or watershed systems are mainly coming from anthropogenic sources, as mentioned, comprising domestic and livestock (animal) waste, industrial emissions, agricultural pollutants, and combined or mixed sewer overflows.During their path in the stream network, BOD concentrations become lower with continuous microbial degradation, leading to river selfpurification, and self-revitalization, and dilution of BODcontaining wastewater before reaching the seas [5].e higher the BOD value, the faster the oxygen in the stream is depleted.is suggests that higher levels of marine life have less oxygen available to them to be consumed aerobically.High BOD has the same effects as low dissolved oxygen where marine lives become suffocated and eventually die.Wastewater treatment plants, feedlots, food-processing plants, failing septic systems, and urban stormwater runoff can cause a spike in recorded BOD due to organic wastes in water [10][11][12][13].
In the present study, we aim to establish empirical correlations between BOD 5 and organic decomposition time to control organic pollution.Ultimate biochemical oxygen demand (UBOD) and minimum and average BOD t data sets along with their reaction rates were collected from the plants used for industrial, domestic (sanitary), and storm (surface) wastewater treatment.e characteristics of various wastewater effluents (which are actually influents to the different wastewater treatment plants) have been thoroughly studied.e ultimate BOD and reaction rates were collected to be used as input to calculate average BOD 5 /COD ratios and DO 5 concentration for the estimation of experimental dilution factors (dfs) at various temperatures and times, that is a very important factor to know how much oxygen should be introduced, based on existing BOD, for successful and complete organic decomposition, allowing us to find the relationships between average BOD 5 vs. COD, and BOD 5 vs. DO 5 .
e proposed regression equations are believed to allow wastewater engineers to facilitate effluent quality assessment via selecting optimal processes that would control microbiological contamination, without the need for laboratory analysis.

Methodology and Study Framework
As discussed, the literature data were collected based on earlier BOD sampling analyses of various wastewater types including industrial, domestic (sanitary), and storm (surface) wastewater in different wastewater treatment plants.
e previously collected laboratory data regarding BOD t at their UBOD and minimum and average determined BOD t values were then utilized to calculate the corresponding minimum and average constant reaction rates (k 1 ) that would quantify organic decomposition rates in the studied BOD-containing sampled water.en, the same identified k 1 2 International Journal of Chemical Engineering was applied in the BOD t fundamental formula in equation (1), knowing UBOD, to obtain BOD t at various times for t � 0-60 days with an increment rate of 5 days.e ultimate goal was to establish relationships between the BOD t and organic decomposition time (t) to control organic pollution in various wastewater effluents.Reaction rates were assumed to be constant numbers since we are treating the same wastewater type at the same plant (i.e., similar wastewater characteristics).
We have also considered the impact of treating wastewater at lower temperatures than that already observed water temperatures in the various studied wastewater samples from selected wastewater plants.
e same steps and/or train of calculations were followed to obtain [BOD t vs. time] correlations when wastewater is treated at lower feed temperature, from using the common k 1 T temperaturedependent equation shown in equation ( 2) along with the predetermined θ constants and their temperature limits as reported in the literature (θ �1.056 for T � 20-30 °C and θ � 1.135 for T � 4-20 °C) [16]. ( e second established and adopted train of calculations starts with obtaining the average BOD 5 /COD ratios that were later used in estimating the average laboratory dilution factors (dfs).It is worth mentioning that we carried out our analysis with a selected ΔDO from x � 60-70% in equation (3), determined from DO 0 , where ΔDO corresponds to organic decomposition associated with the oxygen consumption in water (final dissolved oxygen minus initial dissolved oxygen), knowing that DO 0 at 20 °C � 9.1 mg/L for BOD 5 (for domestic and industrial wastewaters) and that DO 0 at 26.3 °C � 8.1 mg/L for BOD 5 (for storm wastewaters).
e chosen organic decomposition rate of x � 60-70% is considered a reliable range that has been previously applied in the simulation of oxygen saturation concentrations in wastewater in a sludge treatment plant in Jakarta at various temperatures.Also, from the list of oxygen concentrations at a certain temperature, it was found there is a standard DO 0 at a maximum of 9.1 mg/L and a minimum of 7.5 mg/L at 20 °C and 30 °C, respectively [13,16,17].
We have calculated the estimated df from the known BOD 5 , COD, and DO 0 and the determined DO 5 at x � 65% (average) based on equation (3), which would be input in equation ( 4) for df.
For each of the studied wastewater types from the various wastewater treatment plants, we have plotted the relationship between BOD 5 and COD, BOD 5 and df, as well as BOD 5 against DO 5 at x � 65%.Such identified trendlines are believed to allow wastewater engineers and plant technicians or operators to adjust operating conditions accordingly for desired DO corresponding to feed BOD 5 / COD ratios, which would ensure organic decomposition and smooth treatment operation.Figure 1 shows the study framework and the utilized step-by-step methods.

Data Collection and Data Set
Curation.Data sets of industrial wastewater were curated based on 3 factories located in Ghana (Kumasi Metropolis, the capital city of Ashanti) namely Kumasi Abattoir, Coca-Cola, and GGL factories.From sampling methods and adopted data collection for industrial wastewater type, the DO 5 content of liquid was determined by the Azide modification of Winkler's method before and after incubation for 5 days at 20 °C.Such calculated differences would give the BOD 5 values of the sample after allowance had been made for the dilution.For optimum biochemical oxidation, the pH values of the samples were kept in the range of 6.5-8 to have consistent analysis [18].ree various industrial plants were selected to gather their industrial wastewater BOD 5 and COD so that BOD 5 can be recalculated at different k 1 and different temperatures using the common k 1 T temperature-dependent equation shown in equation ( 2) along with the predetermined θ constants and their temperature limits as reported in the literature (θ �1.056 for T � 20-30 °C and θ � 1.135 for T � 4-20 °C) [16].Again, we calculated BOD 5 for 60 days, and in the last, we have taken the average BOD 5 / COD for each plant to get dilution factors.
Regarding stormwater data collection, data sets have been collected from stormwater sources found in different countries.We collected the stormwater quality from the previously carried out sampling of stormwater runoff in the street, highway, surfaces, and parking, collected from different catchments in the selected three different countries (Bialystok-Poland, Abeokuta-Nigeria, Luxembourg), and previously taken for the analysis of pollutants including the parameter of interest here, BOD 5 .Similar calculation steps were followed here to recalculate the BOD 5 in several storm wastewater plants to identify the relationship between BOD 5 vs. COD in ordinary wastewater runoff or rainwater while correlating BOD 5 to the initial dissolved oxygen and required dilution factors [6][7][8].
However, the collection of data and data set curation from various domestic wastewater treatment plants (three plants) was carried out based on data collected from Al-Diwaniyah Wastewater Treatment Plant, the wastewater treatment plants of Jordan, and the North Sewage Treatment Plant in Dhahran, Eastern Province, Saudi Arabia.Typically, domestic wastewater treatment plants collect their samples to be analyzed and find the level of water contamination, and then water quality is compared with other plants' influents/ effluents in the industry for the achievement of less polluted wastewater via various treatment methods.For instance, wastewater stabilization ponds, activated sludge units, and trickling filters are some of the common strategies used for municipal wastewater treatment.Locally, 27 wastewater treatment plants distributed in the populated centers of Jordan are using the above-mentioned techniques for International Journal of Chemical Engineering wastewater treatment.Such contamination can be investigated or attributed to the BOD 5 level in collected samples for pilot-scaling to improve the treatment performance from changing organic loading rates or modifying designed hydraulic, or operating conditions, considering pH, turbidity, TSS, COD, and BOD, for better effluent quality that would potentially reduce contamination to the environment and risk of ecosystem pollution [10-13, 19, 20].

Results and Discussion
Herein, the study of how BOD t changes over time concerning the three different wastewater types has been thoroughly discussed.Regarding the BOD t for stormwater influents (from three different plants), the increasing BOD t trendline with time was justified from raw data in the three selected plants, indicating the strong reliability of the existence of power relationships between BOD t and time as illustrated in Figure 2.Both average and minimum BOD t values (k 1 @ T � 20 °C) were plotted from the various storm wastewater plants, showing a mean range of an average BOD t ≈ 40-78 mg/L and a mean range of a minimum BOD t ≈ 16-55 mg/L, as plotted in Figures 2(a), 2(c), and 2(e).Similarly, the same analysis was carried out with k 1 @ T � 25 °C to find the impact of temperature on the BOD t mean ranges, which were found to increase the initial value (at t � 0) by +6 (with a mean range of an average BOD t ≈ 46-78 mg/L and a minimum BOD t ≈ 22-60 mg/L from k 1 @ T � 25 °C), as plotted in Figures 2(b), 2(d), and 2(f ). is analysis justified the strong correlation and dependence of BOD t on the water temperature, with an average of +1.2 mg/L per every 1 °C as a heat added to the water for the initial BOD t values.It is worth mentioning that the power relationships were expected in all plants since they refer to the organic decomposition rates occurring in storm wastewater that would follow an exponential or a power pattern according to the previously discussed or derived equation (1) for BOD t .
Moreover, the BOD t for industrial wastewater influents were observed with an obvious increase of BOD t trendline with time.However, much higher BOD t concentrations were there because industrial wastes contain very high amounts of organic compounds generated from various chemical and industrial processes.e power relationships between BOD t and time were only accurate at low or minimum BOD t of previously analyzed industrial wastewaters as illustrated in Figure 3.Such inaccuracies have been attributed to the rich organic constituents found with average BOD t samples, making it very difficult for the oxygen-containing wastewater to degrade organics over a short period of 60 days (i.e., it requires either much longer time or very high added oxygen concentrations to see the power relationship between maximum BOD t and time, instead of the linear trends).Plotted data sets showed a mean average BOD t >90,000 mg/L (with T � 20 °C and k @ T � 25 °C, respectively; (c, d) Luxembourg storm wastewater treatment plant with k 1 @ T � 20 °C and k 1 @ T � 25 °C, respectively; and (e, f ) Abeokuta-Nigeria storm wastewater treatment plant with k 1 @ T � 20 °C and k 1 @ T � 25 °C, respectively.
6 International Journal of Chemical Engineering an average of 84,000 mg/L) and a mean minimum BOD t <80,000 mg/L, both from k 1 @ T � 20 °C, as plotted in Figures 3(a), 3(c), and 3(e).Similarly, the same analysis was carried out with k 1 @ T � 25 °C to find the impact of temperature on the mean BOD t , which was found to increase the initial BOD t (at t � 0) by +400 mg/L or 10% more than that of k 1 @ T � 20 °C (with a mean average BOD t >99,000 mg/L from k 1 @ T � 25 °C and a mean minimum BOD t <88,000 mg/L from k 1 @ T � 25 °C), as plotted in Figures 3(b), 3(d), and 3(f ).us, industrial wastewater BOD t increases with temperature by almost +2 mg/L to +3 mg/L per every 1 °C, justifying the impact of temperature on BOD t as suggested.Again, the power relationships refer to the continuous organic decomposition rates as from equation ( 1). e BOD t for domestic wastewater influents were observed with a clear increase of BOD t trendline with time, where both average and minimum BOD t were found to intersect after a long period (60 days).Such behavior like this could be associated with the not low and not high BOD t values for domestic wastewaters, resulting in semisimilar  International Journal of Chemical Engineering trendlines, which correspond to almost similar organic degradation rates for average and minimum BOD t .Here, the power relationships between BOD t and time were justified at low and high selected BOD t from previously analyzed domestic wastewaters as illustrated in Figure 4. Plotted data sets showed a mean range of an average BOD t ≈130-260 mg/ L and a minimum BOD t ≈50-170 mg/L from k 1 @ T � 20 °C, as plotted in Figures 4(a), 4(c), and 4(e).Similarly, the same analysis was carried out with k 1 @ T � 25 °C to find the impact of temperature on the BOD t mean ranges, which was found to increase the initial BOD t (at t � 0) by +20 mg/L or 25% more than that of k 1 @ T � 20 °C (with a mean range of an average BOD t ≈ 150-250 mg/L and a minimum BOD t ≈ 70-160 mg/L from k 1 @ T � 25 °C), as plotted in Figures 4(b), 4(d), and 4(f ).Accordingly, it has been found that domestic wastewater BOD t increases with temperature by almost +4 mg/L per every 1 °C while having shorter required oxidation times at higher temperatures to achieve a nearcomplete organic oxidation rate from utilizing the introduced O 2 in wastewater.Again, as discussed earlier, the power relationships refer to the continuous organic decomposition rates as illustrated in equation ( 1).From correlating the average BOD 5 /COD ratios to the calculated existing DO 5 concentration at 60-70% oxygen consumption rates, we established the optimum df to be taken into consideration before experimentation for BOD t analysis of various wastewaters.
e step V center connection lines (using ORIGIN software), illustrated as solid red lines in Figure 5, show the optimum from df points with an exact average of df ≈ 9.2 for storm wastewater (STM), df ≈ 12 × 10 3 for industrial wastewater (IND), and df ≈ 18.5-28.5for domestic wastewater (DOM).
e importance of df numbers arises from its usefulness as a starting point for wastewater operators and engineers to select the ideal df that would ensure the success of the experimental (sampling) analysis of BOD t of various wastewaters for quantification of organic decomposition rates attributed to the introduced oxygen amounts.Despite that the DO 5 parameter values were assumed to be constant at different observed BOD 5 (due to the consideration of 60-70% oxygen consumption rates according to the literature [13,16,17]), this average oxygen consumption rate would give the best prediction towards estimating df values for each of the studied wastewater types.In other words, the relationships between average BOD 5 vs. df, and BOD 5 vs. DO 5 were found to be both following linear trends with an increase in df when BOD 5 becomes higher.According to the previously mentioned "standard methods for water & wastewater examination," dilution techniques should be done by creating five samples with several dilutions with at least two bottles giving acceptable minimum DO depletion (>2 mg/L uptake after a 5-day incubation period) and residual limits (>1 mg/L) [18].
e plotted linear regressions are useful to facilitate the experimentation and analysis of wastewater samples for optimum selection of df that corresponds to the BOD 5 and DO 5 levels of wastewater influents.Meanwhile, finding the relationship between average BOD 5 and COD is going to give much accurate and rapid analysis because such BOD 5 / COD ratios are known to serve as a guide in selecting proper dilutions for influents/effluents for the wastewater type of interest.
e average BOD 5 /COD ratios for various studied wastewater types (effluents) have been estimated as illustrated in Figure 6(a).Storm wastewater reserved the minimum BOD 5 /COD ratio among the three wastewater types, which indicates existing of lower amounts of organic compounds (as compared to chemicals) in storm wastewater effluents.Storm, industrial, and domestic wastewaters had an average range of BOD 5 /COD ratios of 0.1 ∼ 0.35, 0.36 ∼ 0.5, and 0.4 ∼ 0.48, respectively.Obtaining the average BOD 5 /COD ranges are very useful since they can be used as indicator tools that would help experimentalists to accomplish accurate sampling analysis.Furthermore, using the corresponding df values would allow reaching an optimum design for the treatment of a certain type of influent (or even a mixed influent) in specific wastewater treatment plants.Precisely, the reported exact df averages in Figure 6(b) were justified from our analysis to be the initial trials used for BOD t experimental analysis.is would allow supplying the required oxygen amounts to optimally control and disinfect microbiological contamination in wastewaters.Industrial wastewater had the highest average BOD 5 and COD values in the order of 10 3 , while storm wastewater had much less BOD 5 and COD than that of domestic wastewater, illustrated in Figure 6(b), explaining the reasons for having the lowest BOD 5 /COD ratio for storm wastewater as shown in Figure 6(a).is has been also confirmed from the determined average BOD 5 /COD ratios from the various studied wastewater treatment plants presented in Figure 6(c), which were calculated from the previously conducted BOD t analysis of wastewater influents used in generating such valuable and accurate standardized guidance and operation charts available in Figures 5 and 6 for quality control engineers who might not need to conduct the laboratory experiments prior taking design decisions.
e correlation of both df and DO 5 (mg/L) to the organic decomposition rates of the organic pollutants that exist in various wastewater types has been studied and plotted in Figure 7.As a rule of thumb, it is proven that there will be always a proportional relationship between existing oxygen (translated as DO 5 content) and consumption or organic degradation whereas that the higher the DO 5 there in the water, the more the organic decomposition occurs, as mathematically expressed previously in equation (3).One may observe that the df values here had the same optimum df average values for each wastewater type as predicted from Figure 5, with df≈9.2 for storm wastewater (STM), df ≈ 12 × 10 3 for industrial wastewater (IND), and df ≈ 18.5-28.5for domestic wastewater (DOM).Moreover, df found to have an approximate range of 4.5-13.5,1-22 × 10 3 , and 12-35 for STM, IND, and DOM wastewater types, respectively, which can be used as a guidance or a reliable reference when diluting a specific wastewater sample for BOD t sampling analysis.It is clear that the storm wastewater had the lowest df range and minimum df optimum average because of its lower BOD 5 as well as BOD 5 /COD ratio, as shown in Figure 6, thus indicating the low quantity of existing organic constituents in storm wastewater influents   12 International Journal of Chemical Engineering to be treated at storm wastewater treatment plants.However, the obtained df mean values can serve as a good start for wastewater plant engineers to reach an optimum cost-effective DO 5 concentration that would ensure maximum organic decomposition without the addition of excess or unnecessary extra oxygen amounts (Figure 7).Table 1 shows the summarized calculated results obtained from the collected experimental data sets based on the nine selected plants, as shown in Figure 6(c), for the three studied different wastewater types.All the data analysis has been conducted at the average wastewater temperature (T � 20 °C) that is assumed to be similar to the average surrounding temperature.Domestic wastewater has low BOD 5 /COD values since BOD 5 (organic contents) was found to be always less than half of the existing nonorganic contaminations (COD or chemicals contents) in wastewater.Typical values for the ratio of BOD 5 /COD for untreated municipal wastewater is 0.3 to 0.8 and If the BOD 5 /COD >0.5, the waste is considered easily treatable by biological means.
Knowing that UBOD is a parameter for water quality assessment that quantifies the oxygen required for the total biochemical degradation of organic matter by aquatic microorganisms, the depletion of DO 5 is a primary water quality concern since the oxygen level is associated with disinfection (pathogen destruction).
e DO 5 depletion define the microbial use or consumption (i.e., demand) of oxygen during the aerobic oxidation of electron donors such as readily degradable organic carbon (e.g., sugars as glucose) and ammonia in waters as shown in the simplified reactions equations ( 5) and ( 6) [21], ignoring the substrate being incorporated into biomass.e general form of the previous equations for decomposition of organic matter can be written as in equation (7), where the rate of biodegradation can be modeled as a firstorder reaction (i.e., as a function of the remaining oxygen demand).A portion of the organic matter (the growth substrate) is also converted into cell material, or biomass (the catalyst), so its concentration is changing as well [22]. (5)

Conclusion
We demonstrated the ability to establish empirical correlations between the 5-day biochemical oxygen demand (BOD 5 )  International Journal of Chemical Engineering and organic decomposition in wastewater effluents.Collected data sets from earlier sampling analyses included ultimate biochemical oxygen demand (UBOD) and minimum and average BOD t along with their reaction rates.With a reaction rate k 1 @ T � 20 °C, wastewaters would have an average BOD t of 40-78 mg/L, >90,000 mg/L, and 130-260 mg/L for the storm, industrial, and domestic wastewater, respectively.ere is a strong correlation and dependence of BOD t on the water temperature whereas that every 1 °C added to the water yield in an increase of +1.2 mg/L, +2 mg/L to +3 mg/L, and +4 mg/L in the initial BOD t values for the storm, industrial, and domestic wastewater, respectively.us, there will be shorter oxidation times required at higher temperatures to achieve a near-complete organic oxidation rate.
e microorganisms' oxygen uptake rate has to be less than the available oxygen for reduction of BOD.Based on the 60-70% oxygen consumption rates, the author estimated an optimum average of df ≈ 9.2 for storm wastewater (STM), df ≈ 12 × 10 3 for industrial wastewater (IND), and df ≈ 18.5-28.5for domestic wastewater (DOM).ese df values can serve as a good start in sampling analysis to reach an optimum costeffective DO 5 concentration without the addition of excess oxygen amounts.Such proposed regression equations and standardized guidance charts would bridge the gap between scientific observations and industrial best practices for optimal design and operation to control organic contamination in various wastewater treatment plants.

Figure 3 :
Figure3: e determined fitted power relationships between BOD t and time for 60 days of minimum and average BOD t values collected from analysis of influents in various selected industrial wastewater treatment plants: (a, b) GGL industrial wastewater treatment plant with k 1 @ T � 20 °C and k 1 @ T � 25 °C, respectively; (c, d) Coca-Cola industrial wastewater treatment plant with k 1 @ T � 20 °C and k 1 @ T � 25 °C, respectively; and (e, f ) Kumasi Abattoir industrial wastewater treatment plant with k 1 @ T � 20 °C and k 1 @ T � 25 °C, respectively.

Figure 4 :
Figure4: e determined fitted power relationships between BOD t and time for 60 days of minimum and average BOD t values collected from analysis of influents in various selected domestic wastewater treatment plants: (a, b) North Sewage domestic wastewater treatment plant with k 1 @ T � 20 °C and k 1 @ T � 25 °C, respectively; (c, d) Al-Diwaniyah domestic wastewater treatment plant with k 1 @ T � 20 °C and k 1 @ T � 25 °C, respectively; and (e, f ) Jordan domestic wastewater treatment plant with k 1 @ T � 20 °C and k 1 @ T � 25 °C, respectively.

Figure 7 :
Figure 7: e estimated organic decomposition rate (x) correlated to the calculated 5-day dissolved oxygen (DO 5 ) and experimental dilution factor (df ) for various wastewater influents: (a) storm wastewater (STM) data analysis from water characteristics in Poland, Luxembourg, and Nigeria storm wastewater treatment plants; (b) industrial wastewater (IND) data analysis from water characteristics in GGL, Coca-Cola, and Kumasi Abattoir industrial wastewater treatment plants; and (c) domestic wastewater (DOM) data analysis from water characteristics in North Sewage, Al-Diwaniyah, and Jordan domestic wastewater treatment plants.

Table 1 :
Estimated average and minimum BOD t and water temperature rise impact with the corresponding BOD 5 /COD, experimental dilution factor (df ), and average df range for the various studied wastewater types.∼ 0.48 18.5-28.512-35 * Average values from k 1 @ T � 20 °C, which correspond to the selected wastewater type experimental results.