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Electroplating operations use a lot of water in their processes, and the purer it is, the better. It's used for mixing chemicals and then rinsing the products between plating process steps. It's critical for the rinse water to be clean to prevent cross contamination between processes and for producing clean substrate. A clean active substrate is necessary to prevent delamination of the plated layers.

This point is especially critical for plating operations that use platinum group metals. Their final finishes are expensive, so rejects are very costly to the manufacturer. Additionally, platinum plating operations lose platinum group metals as waste runoff in the rinse and drag out rinse waters in the plating process. Reusing electroplating process wastewater allows the manufacturer to control the quality of each process step. This prevents rejects, saving the manufacturer money. Additionally, a metals recovery system can be easily integrated with a water reuse system so that when the platinum group metals are filtered out of the wastewater, they are actually available for return to the process tank. A separate metals recovery system should be used for each rinse step. For example, the drag out water (the stagnant rinse right after the plating bath) should have its own recovery system. That system should constantly scavenge metals from the stagnant water. The most commonly used methods for platinum recovery systems are:

  • Activated carbon (the platinum group metals are absorbed by the carbon).
  • Selective ion-exchange resin (the platinum group metals are bonded to the resin). This is effective for both rinse and drag out water.
  • A combination of carbon and metal selective resin.
  • Electrowinning (the metals are absorbed into a porous metal cathode). This is best for drag out water.

Integrating metals recovery with water reuse

Water reuse systems have two main treatment protocols:

  1. Purification. For example, lowering the conductivity using ion-exchange resins.
  2. Filtration. For example, reverse osmosis.

To integrate metals recovery into a reuse system, all the wastewater that may contain precious metals must flow through the metals recovery system before flowing through the water purification step in the reuse system. In other words, the whole treatment process looks like this:

Metals Recovery Process for Water Reuse

Directing rinse lines to the water reuse system

Because the drag out water requires periodic dumping through the water reuse system, after it flows through the metals recovery system, it is collected in a tank just before the reuse purification step. All the other rinse waters on the plating process line are counter flow, and the last one is the cleanest. The most concentrated rinse water will first flow to a collection tank before circulating through the metals recovery system. The drag out and post-plating ones (less concentrated) will flow through the precious metal recovery module first and then to the collection tank. All flowing rinse waters can be set up to circulate constantly or based upon its conductivity. The reuse collection tank should contain a level sensor that will trigger a pump to add city water to the tank when the level drops. This setup helps to maintain fresh water levels in the systems that is lost due to the evaporation and spillage.

Benefits of platinum recovery and water reuse

  • Better rinsing (higher purity)
  • Fewer rejects
  • Decreased amount of water purchased
  • Decreased amount of water discharged
  • Decrease in F006 waste
  • Increased precious metal recovery

ProChem strives to help their customers establish the highest level of credibility and a positive reputation within the regulatory community. Their goal is to significantly reduce the amount of fresh water that manufacturers require by providing sustainable solutions that will also benefit the customer’s bottom line.

ProChem, Inc. has been awarded a job for a leading titanium castings manufacturer in Oregon. The company is expanding a new Chemical Milling facility that improves employee safety and minimizes the company’s environmental footprint by adding waste recycling systems.

Namely, the facility will include a tailored ProChem, Inc. Industrial Water Reuse system, designed specifically for this customer’s application. This reuse system will treat the wastewater from the Chemical Milling facility and recycle it for reuse again in the Chemical Milling process.

The reuse system will achieve a 90%+ reuse rate using ProChem industrial high pressure reverse osmosis (I-PRO™) membrane technology, along with physical/chemical and deionization pretreatment protocols. The system features a clean in place (CIP) system for the I-PRO™ unit, allowing the customer to clean the RO membranes on site. The CIP saves time and money and extends the life of the membranes.

The water reuse system will be automated, so it is designed to operate all valves, pumps, and systems from a central PLC with a HMI. The HMI allows the operator to monitor the system. The system also features ProChem’s Remote Monitoring package, which provides web-based access to the water reuse system monitoring as well as trend data for analysis and reporting.

The system is scheduled for startup at the end of the year.  

ProChem strives to help their customers establish the highest level of credibility and a positive reputation within the regulatory community. Their goal is to significantly reduce the amount of fresh water that manufacturers require by providing sustainable solutions that will also benefit the customer’s bottom line.

Zero liquid discharge (ZLD) is a water treatment process that results in absolutely no water byproduct. Instead, solids are produced that can be processed either as hazardous or nonhazardous waste. This can be accomplished using techniques like solidification and evaporation, where the liquids are crystallized or evaporated. Such treatment techniques are gaining popularity with industrial facilities who face more stringent effluent limitation guidelines (ELGs) on the wastewater that they discharge from their facility. This is a growing trend, especially for power generation plants.

ELGs at power generation plants

When coal is burned to make energy, a gas is produced that contains sulfur dioxide. The gas is released into the atmosphere via the flue. Before the gas is released, however, it is cleaned using a scrubber system that includes a water solution. This cleaning process is called Flue Gas Desulfurization or FGD, and the wastewater from the FGD scrubber produces what is called FGD wastewater. The EPA has ELGs specifically for FGD wastewater. One of the main reasons for these rules is the concentration of Selenium found in FGD wastewater. While small amounts of Selenium are actually needed by wildlife for better health, higher concentrations can be detrimental to wildlife and even fatal. The levels of Selenium typically found in water surrounding and downstream of power plants are very high, which is dangerous to wildlife such as fish and birds who eat from that water source. In birds, for example, too much Selenium can lead to weaker eggshell production, resulting in lower birth rate. All power generation plants have to meet the ELG for Selenium that is mandated by the EPA. Moving to a ZLD water treatment process allows these facilities to meet ELGs by avoiding discharge altogether. This is the only 100% guarantee that their discharge permits will be met now and in the future.

Reasons to consider zero liquid discharge

ELGs do change and that requires the manufacturer to act or to face the consequences of not meeting the guidelines. More often, ELGs become stricter over time, and the manufacturing facility ends up needing to purchase additional water treatment equipment and chemicals or to replace their wastewater treatment system altogether. Adding or replacing water treatment equipment often means adding personnel to operate it and capital money to purchase it. The additional water treatment costs also contribute to higher operating costs overall. A zero liquid discharge system eliminates the need to react to changing ELGs because there is no longer any wastewater that has to meet the limits. These systems can be used as a stand-alone treatment following wastewater treatment, or they can be used in conjunction with an industrial water reuse system. Combining water reuse and ZLD means that not only will you never have any wastewater to discharge, but you still have the added benefit of cost savings on water purchases. What's more is that with the right pretreatment process, the solid waste from the ZLD system can be disposed in a landfill as non-hazardous waste. The reality is that most facilities will find themselves in a situation where the ELGs for its industry are changing, and you will need to find a way to meet them. You can take your chances and invest in additional equipment to support a treat and discharge process. It is likely, however, that you will have to modify your treatment process again in a number of years to keep up with EPA mandates. On the other hand, you can invest capital funds into a ZLD and water reuse process now so that you never have to discharge again.  

ProChem strives to help their customers establish the highest level of credibility and a positive reputation within the regulatory community. Their goal is to significantly reduce the amount of fresh water that manufacturers require by providing sustainable solutions that will also benefit the customer’s bottom line.