Pollution control means treating them after they have been created rather than reducing or stopping the generation of pollutants at the source. It is also known as source reduction or waste minimisation. Drug and pharmaceutical industry is engaged in manufacture of life-saving items. However, production of drugs is also associated with generation of pollutants during manufacturing, maintenance and housekeeping operations. Typical waste streams include spent fermentation broths, process liquors, solvents, equipment wash waters, spilled materials, off-spec products and used processing aids. Implementation of cleaner production processes and pollutants treatment technologies can yield both economic and environmental benefits.

Manufacturing process
Pharmaceutical manufacturing is divided into two major stages. They are:
● Primary processing or manufacture, which includes the production of the active ingredient or drug
● Secondary processing, which includes the conversion of the active drugs into products suitable for administration

The pharmaceutical industry utilises a vast array of complex batch-type processes and technologies in both stages. Due to the diversity of these processes, it is impractical to provide a general set of waste minimisation guidelines that would apply to all drug manufacturing. The five areas which play a major role in the manufacturing of pharmaceuticals are:
● Research and development
● Chemical synthesis
● Natural product extraction
● Fermentation
● Formulation
CHARACTERISTICS OF WASTE
The pollutants in drug manufacturing are mainly divided into three categories. They include:
● Air Pollutants: It includes volatile organic compounds (VOCs) and particulate matter (PM)
● Liquid Effluents: It includes wash waters containing toxic organic residues
● Solid Waste: It includes process and effluent treatment sludges, spent catalysts and container residues

MEASURES FOR CONTROLLING POLLUTION
● Meter and control the quantities of active ingredients to minimise wastage
● Reuse by-products from the process as raw materials or as raw material substitutes in other processes
● Recover solvents used in the process by distillation or other methods
● Give preference to the use of non-halogenated solvents
● Use automated filling to minimise spillage
● Use "closed" feed systems into batch reactors
● Use equipment wash down waters and other process waters (such as leakages from pump seals) as make-up solutions for subsequent batches
● Re-circulate cooling water
● Use dedicated dust collectors to recycle recovered materials
● Vent equipment through a vapor recovery system
● Use loss free vacuum pumps
● Return toxic materials packaging to the supplier for reuse or incinerate/destroy in an environmentally acceptable manner
● Minimise storage time of off-specification products through regular re-processing
● Find productive uses for off-specification products to avoid disposal problems
● Minimise raw material and product inventory to avoid degradation and wastage
● Use high pressure hoses for equipment cleaning to reduce wastewater
● Provide storm water drainage and avoid its contamination from process areas
● Label and store toxic and hazardous materials in secure bunded areas. Also, spillage should be collected and re-used

TREATMENT TECHNOLOGIES
Air emission: There are certain effective and applicable technologies for minimising the release of significant pollutants to air. They are:

Scrubbers: These are used to remove particles or gases from industrial exhaust streams. Scrubber uses high-energy liquid spray for removing aerosol and gaseous pollutants from air / gas.

Generally, there are two broad classifications of air pollution controls referred to as scrubbers. They are:

Wet Scrubbers: Wet scrubbing works via the contact of target compounds or particulate matter with the scrubbing solution. Solutions may simply be water (for dust) or complex solutions of reagents that specifically target certain compounds. Removal efficiency of pollutants is improved by increasing residence time in the scrubber or by increasing surface area of the scrubber solution by the use of a spray nozzle, packed towers or an aspirator.

Configurations of wet scrubbers include:
● Orifice scrubbers form a category of gas-atomised spray scrubbers in which a tube or a duct of some other shape forms the gas-liquid contacting zone
● A venturi scrubber accelerates the waste gas stream to atomise the scrubbing liquid and to improve gas-liquid contact
● In fibre-bed scrubbers, moisture-laden waste gas passes through beds or mats of packing fibres, such as spun glass, fibreglass or steel
● Mechanical scrubbers comprise those devices in which a power-driven rotor produces the fine spray and the contacting of gas and liquid
● An impingement-plate scrubber is a vertical chamber with plates mounted horizontally inside a hollow shell. Impingement-plate scrubbers operate as counter current PM collection devices
● Spray scrubbers consist of empty cylindrical or rectangular chambers in which the gas stream is contacted with liquid droplets generated by spray nozzles
● Condensation scrubbing is a relatively recent development in wet scrubber technology. Most conventional scrubbers rely on the mechanisms of impaction and diffusion to achieve contact between the PM and liquid droplets

Dry scrubbers: Dry scrubbing systems are used to remove acid gases (such as SO2 and HCl) primarily from combustion sources. There are a number of dry types scrubbing system designs. However, all consist of two main sections or devices: a device to introduce the acid gas sorbent material into the gas stream and a particulate matter control device to remove reaction products, excess sorbent material as well as any particulate matter already in the flue gas.

CARBON ADSORPTION
Industrial activated carbon adsorbers eliminate volatile organic compounds (VOCs) and odours from industrial process exhaust streams. Activated carbon attracts and holds organic molecules, resulting in high efficiency removal and elimination of toxic or noxious discharge to the atmosphere.

BIOFILTRATION
Biofiltration is a low-cost and highly effective air pollution control (APC) technology, in which vapor-phase organic contaminants are passed through a bed of porous media and sorb to the media surface where they are degraded by microorganisms in the media.

BAGHOUSES
Baghouses, also known as fabric collectors, use filtration to separate dust particulates from dusty gases. They are one of the most efficient and cost effective types of dust collectors available and can achieve a collection efficiency of more than 99 per cent for very fine particulates.

OXIDATION
Organic contaminants are destroyed in a high temperature 1,000°C (1,832 °F) combustor.

LIQUID EFFLUENTS
Reverse osmosis or ultra-filtration is used to recover and concentrate active ingredients.

SOLID WASTES
Contaminated solid wastes are generally incinerated and the flue gases are scrubbed. Combustion devices should be operated at temperatures above 1,0000C with a residence time of at least one second to achieve acceptable destruction efficiency (of over 99.99 percent) of toxics. However, temperatures of around 9000C are acceptable provided at least 99.99 per cent destruction/removal efficiency of toxics is achieved.

Regulatory pressure and environmental concerns are causing drug manufacturing units to take a new look at how pharmaceuticals process waste are being treated. There are several efficient and applicable treatment technologies to control pollutants from pharmaceutical manufacturing. But due consideration should also be given to:
● Monitoring of equipment performance should be done on a continuous basis
● Monitoring data should be analysed and reviewed at regular intervals and compared with the operating standards so that any necessary corrective actions can be taken
● Records of monitoring results should be reported to the responsible authorities.
(The authors are with Sardar Patel University, Gujarat)