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Zero Liquid Discharge Solutions
Zero liquid discharge is a concept that indicates no liquid effluent discharged from the process plant in surface waters which in effect completely eliminates the environmental pollution. In other words, it can be termed as conversion of the solute, ie, dissolved organic and inorganic salts or compounds into solid form by means of thermal evaporation and concentration. Apart from this, it also makes effective use of wastewater treatment, recycle and reuse concept thereby effectively contributing to water conservation through reduced intake of fresh water. This article discusses the challenges of zero discharge in variety of process plants and integrated wastewater treatment solution provided by Pra j Industries for one of the multinational chemical Industry.

Zero Liquid Discharge Technologies offered by Praj
Praj has been dealing with complex effluent treatment and addressing the issue with the help of evaporation and concentration technologies. Being strong thermal base Praj offers various types of evaporators. Selection of type of evaporator depends on composition of the effluent.

Typical comparison of the various types of Evaporators:

*Note: This comparison is based on Praj's experience with highly complex effluents from various industries. Typical challenges of zero liquid discharge systems for chemical industry

The above challenges can be handled by:
  • Innovative and customized solution offerings
  • To reduce scaling tendencies, selection of appropriate pretreatment, operate evaporation system at low temperature
  • To reduce capital investment, use various combination of evaporators
  • Recover steam and process condensate for reuse and recycle
  • Continuous operation of the system – minimization of CIP effluents
  • Use technologies like TVR or MVR for reducing the operating cost.

Project Details for Chemical Process Industry in India
Praj recently executed turnkey project including conceptualization, design, engineering, manufacturing, construction and commissioning of effluent treatment plant, biological and MVR-based evaporator system for one of the leading chemical manu facturing company having its manufacturing locations across globe. The group has business interest in area of specialty polymers and surfactants. To execute the effluent treatment plant for its manufactur ing complex, client awarded design, engineering, supply, erection and commissioning of 80 KLD effluent treatment plant for highly complex effluent with (Mechanical Vapour Recompression) MVR-based Evaporation Plant with pusher centrifuge to Praj. After successful installation and commissioning of evaporation plant client was able to produce Na2SO4 salt at the outlet of centrifuge.

Project Requirement
Client was looking for reliable end-to-end solution provider including biological and thermal solutions to treat its complex, challenging and high TDS effluent.

Pilot Trials
Praj carried out analysis and evaporation pilot trials at Praj Matrix – Research & Development Centre to get first-hand experience on effluent.

Highlights of ETP and ZLD plant supplied by Praj
  • Anaerobic System As the effluent from surfactant manufacturing contains active anionic contents (AAC), the aerobic system would result in heavy foaming in the effluent. Hence, anaerobic system is an appropriate solution to destruct the AAC and then the remaining BOD can be reduced using aerobic system.
    The system is specially designed with fixed media in the reactor and higher retention of the reactor.
  • Aerobic System Aerobic system post anaerobic and anoxic systems is provided to further reduction of BOD. As COD:BOD ratio was on high, aerobic tank was designed with high retention
  • "ECOVAP" Evaporation Plant Praj provided their unique evaporation technology called ECOVAP to concentrate high TDS effluent coming from the process. This is proven technology for treating complex effluents across the world.
    Praj recommended to go for MVR-based evaporator due to saving in energy and resulting into reduced opex.
  • Praj has successfully installed and commissioned plants based on ECOVAP technology in various industries such as textile, chemicals and fertilizers, pharmaceuticals and food and beverages, etc.
Typical schematic for the treatment of effluent from chemical industry

Typical ETP Plant Operating Parameters ETP Parameters

Typical Evaporation Plant Design Parameters

Advantage Praj
  • Turnkey solution under one roof - design, engineering, manufacturing, supply, installation and commissioning for effluent treatment, biological treatment and evaporation systems.
  • Customized design, solution backed by piloting at R&D which ensures minimization of performance risk.
Result of Commissioning of the Plant:
For this project, Praj has successfully designed, manufactured and installed and commissioned integrated biological effluent treatment for difficult to treat effluent and evaporation plant followed by pusher centrifuge