ELG Compliance: Know Your Plant’s Full Water & Wastewater Picture
The Whole is > the Sum of its Parts
This is post one of a four part series on ELG Compliance
As an industry, we’ve made a lot of progress since the effluent limitations guidelines came out. Since then, you’ve probably taken at least some first steps to ready your plant for compliance, like updating your plant’s water and mass balances. By now you should have some data in hand … a “picture” of your plant’s current water and wastewater situation, tracing out flow paths and characterizing water quality. So, what’s next?
Keep Gathering Data
Maybe you’ve gathered sample data for a few weeks—maybe for a couple of months. Are you confident the data you’ve gathered reflects all of the variables experienced at your plant over its entire operational cycle? Think about the seasons. Do you burn different fuel in the summer versus winter months? Use different limestone or other reagents? Operate differently? Different plant operating scenarios can also impact your wastewater flow rates and quality significantly, and the changes aren’t always as intuitive as you would expect.
For instance, our team was working at a two-unit facility, with both units normally operating at base load. While our team was conducting wastewater sampling and flow monitoring at the site, one of the units was shut down. We anticipated a decrease in the plant’s wastewater flow rate, but were surprised to see that certain flows actually increased, and increased significantly.
Due to the intermixing and recycling of wastewater streams between the two units, the loss of one unit limited wastewater reuse opportunities within the plant and ultimately increased the flow rate of wastewater discharged from the facility.
Dial in the Design Criteria
The more data you can collect, the better you will understand your systems and variations that may occur, and the more you can dial in your design. Conservatism in design costs $ and the better you can bound the limits of potential variations, the better you can tailor the design to fit your plant.
Yes, there can be a significant cost associated with continued sampling and testing. But it can pay off in the end by enabling you to refine your treatment system design, so you only invest in the equipment you truly need to achieve compliance. To minimize costs and get the most from your efforts, once you have the baseline data, be more strategic about when you collect additional data—sample when there’s a variance in your system like a new input or operational change. Be sure to note what the change or condition was so you can correlate the data to plant conditions.
Why is this important? Well, you might change coal or scrubber reagent sources and find your mercury or selenium concentration changes. Or the metals change in form in the wastewater. This may lead to different treatment equipment choices or sizing criteria to handle the variations. It’s important to know now that those variations can exist, so you can plan for them during wastewater treatment system design.
Time to Choose
As you’re reviewing the data collected, you’re beginning to vet potential technologies to meet the ELG requirements, make sure you consider and plan appropriately for piloting as a step in the vetting process. Piloting your shortlist of technology solutions provides confidence you’ll meet your limits and a better idea of the associated operational costs.
The pilot planning process can take some time while you work with your engineer and the equipment suppliers to schedule your pilot and develop the testing plan. As you develop your plan be sure to consider and think through details like temporary power provisions, pilot location, equipment sun/snow protection, operations, auxiliary equipment needed (piping, pumps, tanks, etc.), and whether you might want to run multiple technologies simultaneously to compare and contrast. Given the demand, it can be challenging to get your hands on the pilot equipment—equipment suppliers have a limited number of pilots available—so allowing time for this process is critical.
Once the equipment is in place, the pilot should be run for several months to provide you the opportunity to test outcomes in a real world environment. This is your chance to run the equipment through its paces. Plan to assess as many operational scenarios as possible and optimize the equipment and chemical dosages rates so you can determine if this is really the best technology solution for your plant’s circumstances.
As you move into these next steps, don’t forget to think holistically, and continue to look ahead. While you’re making changes for the ELGs, maybe you’re also addressing the CCR or other regulations—closing a CCR pond, making changes to air pollution equipment, handling ash differently. These changes may impact your ELG plans, so it’s important to coordinate efforts and predict now how these changes may impact the plant water and mass balances and any treatment systems you are planning to install. Look ahead a few years, and pay attention to changes in the coal power industry so you’re ready to adapt to all changes.
Look for my next post, 5 tips for getting your equipment in place on time.