Zero Liquid Discharge vs. Water Reuse - You Can Have Both

 

Water reuse systems and zero liquid discharge systems are not the same. They do offer similar benefits such as reducing operational costs spent on purchasing water and disposing of wastewater. But which system is better? On the surface, it might seem obvious that recycling wastewater is best because you get the most out of the water you purchase. While zero liquid discharge systems require that you continue to purchase water and then solidify it rather than discharge it.

 

Depending on the facility, however, it may be more cost-effective to implement zero liquid discharge. So what is the answer? Both are best. You can integrate a water reuse system with a zero liquid discharge system. This combination yields ideal results. Zero liquid discharge system manufacturer

 

An industrial water reuse system alone is a great way for your company to proactively address drought concerns, meet corporate social responsibility initiatives, and lower operational costs.

 

These systems allow you to recycle your wastewater and use it again and again in a closed loop system. They still require liquid discharge sometimes. That is, once the concentrate becomes too concentrated for recirculation, it needs to be discharged.

 

In this case, you may still need to hold a discharge permit; though, it may not be the same as it was before installing the water reuse system. With one of these systems, you do get the added benefit of saving on water purchases, lowering your water consumption, and a must lower risk of not meeting your discharge permit.

 

Using a Zero Liquid Discharge process, however, means that you have no wastewater to discharge at all. It is solidified or evaporated into solids instead.

 

Depending on the pretreatment method, the solids may also be non-hazardous solid waste that can be taken to the landfill. You will not save on the costs of purchasing water because you are not reusing the water you purchase, but you will not need a discharge permit.

 

Now, if you combine the two systems, you will have all the benefits and none of the risk of discharge permits violations.

 

 

How it works

 

The water reuse system receives wastewater from the industrial process, treats it, and sends the purified water back to the process. The concentrate water is re-circulated through the treatment and reuse system until it's unusable.

 

At that point, the concentrate is sent to the zero liquid discharge system for solidification or evaporation.

 

Because water reuse systems require pretreatment to protect and extend the life of the membranes, the concentrate is still usually high enough quality for non-hazardous discharge.

 

This means that the solid waste produced from the zero liquid discharge system will also be non-hazardous and is easily disposed.

 

For the best results, use a water treatment vendor who offers both system types and integration services. This will ensure a cohesive and comprehensive design, which leads to the best results.

 

 

Industrial Water Treatment - Why Zero Liquid Discharge Is a Good Idea

 

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 non-hazardous 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 that 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.

 

Engineers of Waterman Australia has decades of experience in water treatment, wastewater treatment, drinking water purification, Water filtration plants, reverse osmosis systems, desalination plants, Ultrafiltration, Microfiltration, Nanofiltration, effluent recycling, zero liquid discharge system, Waste Incinerator for solid liquid waste management from concept to commissioning.

 

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 the 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 eggshells, resulting in a lower birth rate.

 

All power generation plants have to meet the ELG for Selenium which 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 of in a landfill as non-hazardous waste.

 

The reality is that your facility will find itself in a situation where the ELGs for your industry is changing, and you need to find a way to meet them.

 

You can take your chances and invest in additional equipment to support a treatment 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. Discover more