Zero Liquid Discharge (ZLD)

Concept

At Condorchem Envitech, we are committed to sustainable processes oriented to zero discharge (also known as zero liquid discharge). The reason is twofold: to try to recover water of excellent quality and to re-use waste or minimize its production.

Using combined concentration techniques, such as membranes and vacuum evaporation, a sufficient concentration of waste can be achieved to:

  • Reuse the water obtained after the treatment process.
  • Sell the waste for other applications.
  • Use the waste as an alternative fuel in cogeneration equipment or other systems.

Benefits

Zero discharge of liquid effluents is the most sustainable alternative that any industry can adopt in the management of its liquid waste. Zero discharge consists of using techniques and processes that make the reuse of liquid effluents possible with a dual purpose: firstly, to reduce water consumption as much as possible and, secondly, to minimize the volume of waste to be externally managed.

Thus, the zero discharge system concentrates pollutants by thermal treatment and, finally, the effluents are reduced to a dry residue, while the extracted water can be reused again in the process.

The main advantagentages of the implementation of a zero discharge system are the following:

  • Reduction in the company’s environmental impact by minimizing the production of liquid waste.
  • Financial savings in the external management of waste.
  • Reduction in the consumption of mains water by re-using water produced in the process. This advantage also results in an even greater reduction of the company’s environmental impact.
  • Financial savings by reducing the consumption of mains water.
  • Increase in the company’s environmental responsibility and its commitment to sustainability.
  • Strict compliance with the most demanding environmental regulations.
  • Financial savings from the taxation of the discharge and possible administrative sanctions for not complying with the environmental regulations in force.
  • Increased flexibility in the management of liquid effluents produced by not depending on any external agent.
  • Flexibility of the system in terms of changes in the composition.
  • Little space needed, as they are compact systems.
  • Simplicity of operation.
  • High degree of automation.
  • No need for specialized technical personnel.
  • Low cost of personnel.
  • Savings in the consumption of chemical reagents.
  • A high degree of self-sufficiency with regard to water consumption.
  • Possibility of taking advantage of secondary heat from other processes, dramatically reducing operating costs.

Condorchem Envitech Offer

Condorchem Envitech has a lot of experience in designing the zero discharge systems that best suit the specific needs of each customer. The optimal system is designed, built and put into operation according to the properties of the effluent and the volume to be treated.

Condorchem Envitech has a solid team of experts, backed by more than 200 successfully executed projects. We specialize in vacuum evaporators and crystallizers, which are currently the best available technologies for the effective implementation of a zero discharge system.

Our zero liquid discharge equipment

Water types

The features of a zero discharge system mean it is quite flexible and can be used practically with any liquid effluent. Only in those cases where the effluent contains volatile compounds is the system slightly more complex, but still equally effective. One of the advantages of this type of system is that it is not very selective in terms of the requirements the effluents to treat must meet.

The main obstacle when installing a zero discharge system may be its cost, as it is not always the most cost-effective solution. To see if a zero discharge system is efficient from a financial point of view, its CAPEX and OPEX have to be analyzed before any decision is made.

If possible, its implementation is highly advisable, as environmental regulations are increasingly restrictive and generally do not allow liquid effluents to be discharged without prior treatment. Although there are conventional treatments that can be technically feasible in a large number of cases, there are situations where the effluents are complex (e.g. in the case of MSW landfills) or they contain a high concentration of salts (e.g. the preparation of pickles and fish preserves) or emulsions (e.g. degreasing baths and release agents) and, in general, conventional processes are not effective.

In other cases, the treated effluent cannot be discharged for geographical reasons or it requires a high financial input to adapt it to increasingly stringent environmental regulations. In all these situations, the zero discharge system is presented as the optimal solution.

Sectors and applications

Sectors

Although the use of this technology is increasingly widespread since it became easier to obtain (renewable) energy at a lower price, its typical application is in all those cases in which conventional treatments are not viable. This occurs when the effluents are complex, brackish, contain emulsions or toxins, for example, or when it is important not to produce any liquid discharge. The implementation of zero discharge systems is common in the following sectors:

  • Food industry
  • Metals industry (e.g. emulsions, degreasing baths and release agents)
  • Pharmaceutical industry
  • Chemical industry
  • Surface treatment industry
  • Cosmetics industry
  • Perfume industry
  • Aluminum casting industry
  • Aeronautics industry
  • Microelectronics industry
  • Municipal solid waste dumps

Applications

For the treatment of effluents produced in certain types of processes, this technology has practically no competition. Some of the many examples are:

  • The preparation of pickles, preserves and salted fish.
  • Emulsions and degreasing baths in the metal-mechanical industry.
  • Equipment washes in the chemical, pharmaceutical, cosmetic and perfumery industries.
  • Leachate from municipal solid waste dumps.
  • Demolding agents in the aluminum injection industry.
  • Washes from the construction of plates and electronic circuits.

Processes and technologies

The implementation of a zero discharge system involves the treatment of all liquid waste to such an extent that its quality allows it to be reintroduced into the process, so that final rejection is at a minimum. To achieve this, effluent concentrating processes need to be used.

Thus, microfiltration and ultrafiltration units used as pre-treatment and processes such as nanofiltration and reverse osmosis recover around 80% of the water, while concentrating the contaminants in a rejected liquid stream. Subsequently, processes based on thermal separation, vacuum evaporation and crystallization focus on concentrating the reject from membrane techniques, producing distilled water, reusable in the process, and a dry solid residue. Thus, the objective of producing no type of discharge is finally possible.

Specifically, vacuum evaporation is a technology that combines the ability to reduce discharges as far as possible with efficacy, robustness, and sustainability. For this reason such systems are practically indispensable when implementing a zero waste management system. When the only waste should be a dry solid, vacuum evaporation is used in combination with a crystallizer, which crystallizes the residue from the evaporator.