With the onset of 21st century, the need of clean water is becoming extremely important due to fading water resources. The groundwater levels are depleting and water bodies are becoming increasingly polluted. This arises the need of proper water resources management and wastewater treatment. One of the key polluters is the commercial industry. Out of all commercial industries, the Indian Pharmaceutical Industry is one of the rapidly advancing areas among the developing countries in the world. (Lall 1974) The manufacturing processes of pharmaceutical products generate a mixed stream of wastewater, which is difficult to treat. Newer technologies need to be developed so that the pollution from these industries can be lessened. Several methods that can treat the process wastewater are mainly divided into aerobic and anaerobic treatment procedures.
Anaerobic treatment offers an attractive prospect because of its clear advantages over other treatment options. Some of them being low sludge formation and production of biogas as a form of energy. The remarkable advantages over aerobic treatment are low energy demand, high organic loading, short hydraulic retention time (HRT) and easy reactor construction. (Eddy 1991) Thus, for my study, I have created a lab-scale Up-flow Anaerobic Sludge Blanket (UASB) reactor and monitored its performance in treating pharmaceutical effluent taken from a local industry.
Keywords: Anaerobic, Methane, Pharmaceutical effluent, Sludge blanket, Up-flow, Wastewater
THEORY OF ANAEROBIC DIGESTION
One of the oldest processing technologies used by humankind is anaerobic digestion. It is also referred to as bio-methanization, a natural process that takes place in absence of air/oxygen. (Joy, Das et al.) It involves decomposition of complex organic material by various biochemical processes with release of biogas and production of nitrous by-products.
The digestion process that occurs in the absence of oxygen and generates mixture of gases, mainly methane is called anaerobic digestion (Rajeshwari, Balakrishnan et al. 2000) It is a multiple-stage process in which the main stages are as follows:
BIOLOGICAL PROCESSES FOR ANAEROBIC DIGESTION
Hydrolysis is a reaction that breaks down the complex organic molecules into soluble monomers. Bacteria decompose long chains of complex carbohydrates, proteins and lipids into small chains.
For example, hydrolysis reaction where organic waste is broken down into a simple sugar, in this case, glucose:
C6H10O4 + 2H2O ———› C6H12O6 + 2H2
This stage is facilitated by acid forming microorganisms, which transform the products of hydrolysis into simple organic acids such as acetic, propionic and butyric acid as well as ethanol, carbon dioxide and hydrogen. Acid forming stage comprises two reactions, acidogenesis (or fermentation) and the acetogenesis reactions.
In this stage, acidogenic bacteria transform the products of the first reaction into short chain volatile acids, ketones, alcohols, hydrogen and carbon dioxide.
Three typical acidogenesis reactions where glucose is converted to ethanol, propionate and acetic acid, respectively are:
Equation 1: C6H12O6 ? 2C3CH2¬OH + 2CO2
Equation 2: C6H12O6 + 2H2 ? 2CH3CH2COOH + 2H2O
Equation 3: C6H12O6 ? 3CH3COO
In this stage, the rest of the acidogenesis products, i.e., propionic acid, butyric acid and alcohols are transformed into hydrogen, carbon dioxide and acetic acid by acetogenic bacteria.
Glucose (equation 2) and ethanol (equation 3) are also converted to acetate during the final stage, acetogenesis.
Equation 1: CH3CH2COO- + 3H2O ? CH3COO- + H+ + HCO3- + 3H2
Equation 2: C6H12O6 + 2H2O ? 2CH3COOH + 2CO2 + 4H2
Equation 3: CH3CH2OH + 2H2O ? CH3COO- + 2H2 + H+
Methanogenesis is a reaction facilitated by the methanogenic microorganisms that convert soluble matter into methane. Two thirds of the total methane produced is diverted by converting the acetate or by fermentation of alcohol formed in the second stage. Finally, produced methane is a result of the reduction of the carbon dioxide by hydrogen.
The bacteria responsible for this conversion are called methanogens and are strict anaerobic. Waste stabilization is accomplished when methane gas and carbon dioxide are produced.
Equation 1: CO2 + 4H2 ? CH4 + 2H2O
Equation 2: 2C2H5OH + CO2 ? CH4 + 2CH3COOH
Equation 3: CH3COOH ? CH4 + CO2 (Ostrem and Themelis 2004)
GENERAL MANUFACTURING PROCESS IN PHARMACEUTICAL INDUSTRY
The modern era of the pharmaceutical industry is considered to have begun in the 19th century, thousands of years after intuition and trial and error led humans to believe that plants, animals, and minerals contained medicinal properties. (Dailey 2018) The unification of research in the 20th century in fields such as chemistry and physiology increased the understanding of basic drug-discovery processes. Identifying new drug targets, attaining regulatory approval from government agencies, and refining techniques in drug discovery and development are among the challenges that face the pharmaceutical industry today. (Weatherall 1990)
The production of pharmaceutical products can be broken down into three main stages:
1. Research and Development: New drug development involves four principal phases: Pre-Clinical Research and Development; Clinical Research and Development; Review of New Drug Application; and Post Marketing Surveillance
2. The conversion of organic and natural substances into bulk pharmaceutical substances: typically consist of structurally complex organic chemical compounds that are manufactured via a series of intermediate steps and reactions under precise conditions and are manufactured by Chemical synthesis, Fermentation, Isolation/recovery from natural sources and/or a combination of these processes.
3. The formulation of the final pharmaceutical product: to convert the manufactured bulk substances into a final, usable form. (Thakur 2013)
CHARACTERISTICS OF WASTEWATER GENERATED
The effluent generated from the various manufacturing processes of variety of products in the pharmaceutical industry has following characteristics (based on average data collected from local pharmaceutical industry):
pH (relatively acidic) 5.8-7.8
COD 128–960 mg/l
BOD 20-620 mg/l
TDS 650-1250 mg/l
TSS 230-830 mg/l
Alkalinity 130-564 mg/l
Chlorides 205-261 mg/l
Ammoniacal Nitrogen 1254mg/l
DETERMINATION OF PHYSICAL AND CHEMICAL CHARACTERISTICS OF WASTEWATER
METHODOLOGY FOR MEASUREMENT OF pH VALUE:
Principle: The pH of the wastewater sample is determined electrometrically using either a glass electrode in combination with a reference potential or a combination electrode.
Procedure: After proper calibration of pH meter, readings are taken. (Sawyer, McCarty et al. 1978)
METHODOLOGY FOR MEASUREMENT OF COD:
Principle: Chemical Oxygen Demand (COD) is the amount of oxygen required to enable chemical oxidation of organic matter using a strong chemical oxidant, like potassium dichromate and a catalyst of silver sulphate to enable redox reactions under reflux conditions.
Procedure: The COD is determined by the standard open reflux titrimetric method. (Sawyer, McCarty et al. 1978)
METHODOLOGY FOR MEASUREMENT OF TOTAL SOLIDS:
Procedure: 1) A pit crucible is cleaned and placed in a hot air oven at 103? for 1 hour.
2) The crucible is placed in a desiccator until it cools and then it is weighed.
3) The sample is thoroughly mixed and diluted to 100 ml by volumetric flask or pipette.
4) The sample is transferred to the crucible initially weighed and the flask rinsed or pipetted several times with small portions of distilled water and the rinsing added to the dish. It is to be made sure that all suspended matter is completely transferred to the crucible.
5) After the sample is evaporated, the crucible is dried in the oven at 103? for 1 hour, cool in the desiccator and weigh. (Sluiter, Hames et al. 2008)
Increase in weight (cm) × 1000 ÷ Volume of sample (ml) = Total solids in parts per million (ppm)
METHODOLOGY FOR MEASUREMENT OF TOTAL DISSOLVED SOLIDS (TDS):
Principle: Total solids consist of dissolved solids and suspended solids. Dissolved solids are soluble in wastewater.
Procedure: The readings are taken with the help of a TDS meter.
METHODOLOGY FOR MEASUREMENT OF AMMONIACAL NITROGEN:
Procedure: The Ammoniacal nitrogen (NH3N) test is determined by Nessler’s method. (Koch and McMeekin 1924)
OPERATIONAL PROCESS OF LAB-SCALE UASB REACTOR UNDER STUDY
The influent is pumped to the UASB reactor in a set-up from the bottom of it at controlled gravity flow at a definite upflow velocity. Here the suspended solids in the influent along with bacterial activity and growth lead to the formation of sludge.
The influent then moves upwards and gets in contact with the blanket of granular sludge. The sludge blanket is comprised of microbial granules (1 to 3 mm in diameter), i.e., small agglomerations of microorganisms that, because of their weight, resist being washed out in the upflow. (Schmidt and Ahring 1996) The rest substrate acts with the biomass again in the sludge blanket, which has a less concentration of biomass as compared with the sludge bed below.
The microorganisms in the sludge layer degrade organic compounds. As a result, gases (methane and carbon dioxide i.e. biogas) are released. The rising bubbles mix the sludge without the assistance of any mechanical parts.
While passing through the sludge bed, a considerable COD reduction is obtained. The volume of the sludge blanket must be sufficient to conduct the wastewater treatment by-passed by channelling. At the same time, it will ensure a stable effluent quality.
The gas outlet is dipped in water vessel to maintain the anaerobic conditions in the reactor system. Upstream velocity and settling speed of the sludge is in equilibrium and forms a locally rather stable, but suspended sludge blanket.
After several weeks of use, larger granules of sludge form which in turn acts as a filter for smaller particles as the effluent rises through the cushion of sludge. (Chen, Wang et al. 2011)
• Flow = 12 litre/day (500 ml/hr)
• Reactor volume = 4L
• Total influent COD = 10,000 mg/l
• Soluble influent COD = 8000 mg/l
• Total influent VSS = 2000 mg/l
• Effluent VSS = 250 mg/l
• Volume effective factor = 0.8
1) Volume effective factor = 4 L
= 5 litre (overall)
2) Volume = 5 litre (overall)
Diameter of reactor = 10.0 cm = 0.1 m
Side water depth = Vtotal
= 5 × 10-3 m3
= 0.6366 m
= 63.66 cm
Overall height = 75 cm (considering freeboard)
3) Hydraulic Retention Time (HRT) calculation
HRT = ? = V
= 5 litre
= 0.417 day
= 10 hours (Eddy 1991) (Karia and Christian 2013)
DISCUSSION AND RESULTS
Based on the design criteria as discussed above, a model was constructed using required materials as shown in picture below:
Figure 1: Actual lab-scale model created for study
Following were the average readings recorded:
Initial COD of the influent stream = 18800 mg/L
Final COD of the effluent stream = 11120 mg/L
Thus, the COD reduction in the effluent stream was observed to be around 40.85%
In the effluent stream, some amount of the suspended solids from the sludge blanket was also observed. Hence, before the analysis filtration was mandatory to remove the suspended solids to get the accurate results.
Along with COD, colour and odour problem was detected. Hence, further treatment to reduce the colour and odour is required to comply with the norms of Gujarat Pollution Control Board (GPCB).
Furthermore, the COD reduction observed was quite less than the theoretically mentioned value. To solve this, further treatment units would be required for reducing the COD to comply with the stringent GPCB effluent discharge norms. (https://gpcb.gov.in/)
It can be concluded that the anaerobic treatment system constituting Upflow Anaerobic Sludge Blanket Reactor system is easy with the installation work but difficult to maintain. The operational parameters related to the system, especially for pharmaceutical effluent are quite difficult to maintain during the practical running of the system making it quite less adaptable technically as well as economically for full-scale treatment of the pharmaceutical effluent.