Treatment of Pharmaceutical Wastewater in Effluent Treatment Plant and Operational Issues-Sludge Bulking






(Waste Treatment in the Process Industries - Chapter 5 ( along with design examples & Calculations) 


The pharmaceutical industry manufactures biological products, medicinal chemicals, and botanical products. The industry is characterized by a diversity of products, processes, plant sizes, as well as wastewater quantity and quality. In fact, the pharmaceutical industry represents a range of industries with operations and processes as diverse as its products. 

Hence, it is almost impossible to describe a “typical” pharmaceutical effluent because of such diversity.The most frequently detected compounds were basically of pharmaceutical origin, that is, coprostanol (fecal steroid), cholesterol (plant and animal steroids), N,N-diethyltoluamide (insectrepellant), caffeine (stimulant), triclosan (antimicrobial disinfectant), and so on.


Bulk pharmaceuticals are manufactured using a variety of processes including chemical synthesis, fermentation, extraction, and other complex methods. Moreover, the pharmaceutical industry produces many products using different kinds of raw material as well as processes;

Classes and Subclasses with typical examples

1. Medicinal 

  • Antibiotics (e.g., penicillins, tetracyclines)
  • Vitamins (e.g., B, E, C, A)
  • Anti-infective agents (e.g., sulphonamides)
  • Central depressants and stimulants (e.g., analgesics, antipyretics, barbiturates)
  • Gastro-intestinal agents and therapeutic nutrients
  • Hormones and substitutes
  • Autonomic drugs
  • Antihistamines
  • Dermatological agents–local anesthetics (e.g., salicylic acid)
  • Expectorants and mucolytic agents
  • Renal acting and endema reducing agents

2. Biologicals 

  • Serums/vaccines/toxoids/antigens

3. Botanicals 

  • Morphine/reserpine/quinine/curare
  • Various alkaloids, codeine, caffeine, etc.

Hence, it is difficult to generalize its classification. In spite of extreme varieties of processes, raw materials, final products, and uniqueness of plants, a first cut has been made to divide the
industry into categories having roughly similar processes, waste disposal problems, and
treatment methods. Based on the processes involved in manufacturing, pharmaceutical industries can be subdivided into the following five major subcategories: 
  1. Fermentation plants;
  2. Synthesized organic chemicals plants;
  3. Fermentation/synthesized organic chemicals plants (generally moderate to large plants);
  4. Biological production plants (production of vaccines–antitoxins);
  5. Drug mixing, formulation, and preparation plants (tablets, capsules, solutions, etc.).


Much research has focused on bulking of the sludge in the aerobic treatment of pharmaceutical wastewater.

- The filamentous organism Sphaerotilus natans has been reported to be responsible for sludge bulking. The growth of these filamentous organisms was coupled with a deficiency of nitrogen in the wastewater and shock organic and hydraulic loading applied in the system

- Another researcher identified the Type 021N microorganism as being responsible for sludge bulking. Three microorganisms, Type 0092, Microtrix parvicella, and Type 0041, were also identified to be responsible for sludge bulking. It has been further noted that another factor responsible for the bulking of sludge is influent wastewater variability. Subsequently it has been concluded that all three organisms are correlated with filamentous bulking at low organic loading. 

- To deal with the problem of sludge bulking, the addition of nitrogen was recommended, but even after doing so, operational problems continued and the decision was made to expand the treatment facility to avoid shock organic and hydraulic loading in the reactor. It was further observed that the addition of PAC in the activated sludge process resulted in some improvement in sludge settleability; however, the MLSS settling rate remained at a very low level (0.01–0.05 cm/min). 

- The study demonstrated that due to nitrification, the pH decreased, causing a viscous floating layer of MLSS formed on the surface of the aeration basin and clarifier that resulted in significant reductions in the MLSS and PAC concentration in the system.

- Chlorination of mixed liquor has been recommended to address the problem of sludge bulking. It was expected that chlorination of the mixed liquor at dosages ranging from 3 to 7.5 lb Cl2/1000 lb MLSS could control the problem of sludge bulking; however, chlorination had in fact severely affected the treatment process and stopped nitrification. To resolve this problem, it was suggested that the plant should always operate at an F/M ratio above 0.15 to avoid filamentous growth, and that any increase in filaments should be treated before intense chlorination. Another study recommended that sludge bulking be controlled by operating the system at a dissolved oxygen (DO) concentration of MLSS greater than 3 mg/L. An optimal dissolved oxygen control strategy for an activated sludge system in treatment of pharmaceutical wastewater.


Recommended Level To Avoid Sludge Bulking

Chlorination of MLSS for Sludge bulking

3 to 7.5 lb of Chlorine/1000 lb of MLSS


1.36 to 3.40 kg of Chlorine/ 454 kg of MLSS

F/M Ratio to be maintained in case of chlorination* is conducted


Sludge bulking be controlled by operating the system at a dissolved oxygen (DO) concentration of MLSS greater than 3 mg/L

>3 mg/l

*Dosage to be done carefully to avoid dead MLSS/MLVSS

Temperature has been shown to affect the performance of the activated sludge process. Pilot plant results indicated that system efficiency was excellent as long as the aeration
basin temperature was less than 38 deg C, whereas at temperatures exceeding 38 deg C, BOD5 removal efficiency decreased considerably, accompanied with the cessation of nitrification. High temperatures resulted in killing of the nitrifiers and inhibited carbonaceous removal. Hence, a heat exchanger in the influent line has been suggested to bring down the wastewater temperature.

The above stated is the summary only. Please refer to the link below:

For detailed understanding and problem solving 
1. Treatment of Synthetic Organic Bulk Pharmaceutical Waste;
2. Treatment of Fermentation/Synthetic Organic Bulk Pharmaceutical Waste; and
3. Treatment of Fermentation, Organic Synthesis Processing, and Chemical Finishing and Packaging Type Bulk Pharmaceutical Waste.

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