国产麻豆

Part 2

Better late than never, the quest to implement wet landfill technology continues . . .

By Adam Jochelson, P. E., MOLO

Regular readers of this commentary may remember that the last installment ended with a bit of a cliffhanger鈥攖hat has been dangling for about five months now. My apologies to anyone who has been eagerly awaiting the follow up. But one thing Hollywood has taught me is that a good sequel takes some time to put together. Plus, even a writer dedicated to his trade can use a little time off.

A reminder of the story so far: inspired by what she learned at a conference, my boss set a course for our landfill to become a bioreactor. After much wrangling over the appropriate permit modifications and invention of a new name for it (Enhanced Leachate Recirculation or ELR), the TCEQ approved our plans. We hired an ELR Manager (Sam) to build and operate the system, who abruptly left for a better job somewhere else, bringing us to the start of Adventures in Bioreacting, Part 2 鈥�

A flourish of epic music 鈥� the camera pans across an arid, dusty landscape 鈥� arriving at the landfill, it slowly zooms in on our hero, wearing a broad-brimmed hat, toiling away in the heat 鈥�

Some Like It Hot

High Density Polyethylene (HDPE) begins to melt at about 400隆F. Fusion welding entails raising the temperature of adjoining lengths of pipe to a little above this temperature and squeezing them together under pressure as the pliable semi-liquid plastic hardens into a solid juncture.

Implementing ELR requires fusing hundreds of sections of HDPE together to provide a network of liquid transportation and injection infrastructure. Getting the geometries to work out can be somewhat challenging, especially when you need to include connections to pumps and portable tanks. But the weather can be even more challenging than that. Precipitation impedes progress; sometimes the temperature is too low to allow proper heating of the plastic; other days it feels hot enough for the pipes to fuse themselves together without any help from you.

In a perfect world, we would stage assembly of ELR infrastructure to avoid the Texas summer with high temperatures regularly in the triple digits. But we do not live in a perfect world, and sometimes we have no choice. Sam鈥檚 exit was just such a time. His departure came in the middle of construction of several permeable beds, with at least 1,000 feet of injection pipelines in a location that would soon be covered up by the next lift of garbage. So I rounded up our posse of experienced fusion welders, and we worked as fast as we could despite the stifling heat. We spent these days in the shadow of the landfill鈥檚 working face, hurried along by its steady advance in our direction. We managed to complete the work, but the experience fighting the mid-July sun at high noon motivated us to stay ahead of the game in the future.

Gravel and Tires and Glass, Oh My!

When Sam left, we had yet to determine the ideal material to use as a water-transmitting medium in our permeable beds (PBs). In fact, that first set of PBs we constructed after his exodus included many different bedding materials:聽 gravel, sand, crushed glass, mulch, brush, tires shreds, etc. We evaluated each option according to several criteria, including ease of spreading into a smooth working surface, availability in required quantities, and ability to protect completed pipeline from crushing by garbage and equipment. They all did well in some aspects, and less well in others.

Tire shreds are surprisingly easy to traverse and provide a springy cushion to protect your work. Plus, they鈥檙e typically abundantly available in most locations. However, we discovered their major drawback after we decided they were a viable option鈥攆lammability (see 国产麻豆, May 2015, The Second Worst Thing That Can Happen at a Landfill). Mulch and sand provide almost unrivaled working surfaces, but their fine particles tend to plug up the perforations in your distribution pipelines when used to cover them. Also, sand has more valuable uses around the facility and is often not readily available onsite. Gravel is practically ideal, except that it鈥檚 even more difficult to acquire than sand. Brush is almost impossible to spread into a viable working surface, but provides exceptional protection from crushing. Ultimately, we settled on using crushed glass as our bedding material and piling raw brush on top for protection. We happened to have a good supply of both鈥攇lass from our resource recovery processor that was too contaminated to recycle, and brush from our City鈥檚 residential bulk waste collections. Keep in mind that if you choose to pursue wet landfill operations, you may choose a very different path based on your particular environment.

Remember the Words of the Immortal Socrates, Who Said, 鈥淥ur Permit Says What?!鈥�¹

The winding road leading from idea to implementation of bioreactor technology can twist and turn and even double back on itself sometimes. In our case, after struggling to get permission from the TCEQ, then obtaining suitable materials and building necessary infrastructure, it would seem that we were ready to start pumping water into the waste mass. But to be sure we had not overlooked something important, we conducted a detailed review of the entire permit before commencing. Of course, we discovered something important 鈥� and bad. It was something that was there all along, but did not seem all that significant until we were about to be required to do it.

We noticed a provision of the section describing the various monitoring activities that would be initiated upon throwing the switch, so to speak. It required quarterly augering of the waste mass across the ELR landfill cells, sampling materials from the augered holes, visual evaluation of those samples on a number of criteria and sending them for laboratory testing to determine degradation, moisture content, etc. Serious consideration of this prospect led us to two vital conclusions: (1) This requirement would be extremely expensive and (2) it would not be particularly useful, akin to picking out a needle and calling it representative of the haystack. So we delayed our ELR ribbon cutting ceremony about a year while we sought another permit modification to remove that provision and correct a few other minor details. The moral of the story here is that you should learn from our missteps, and your wet landfill experience will likely be smoother than ours at McCommas Bluff.

Worth the Wait?

Whatever you call it鈥擝ioreactor, Wet Landfill, Enhanced Leachate Recirculation鈥攖hese types of landfill remain a relatively new technology. Some of the benefits, like improved gas quality and reduced leachate disposal costs, occur soon after implementation. Others take years or even decades to manifest themselves. I left my post at McCommas Bluff not long after initiation of liquid injection, having personally pumped just over 3 million gallons of water into the waste mass. Anecdotal reports from my contacts the remain there have been positive regarding the results, but who knows when the final chapter will be written?

Adam Jochelson, P. E., MOLO, is a principal engineer at DHR Engineering, Inc. (Irving, TX). He鈥檚 also the CEO of Modern Landfill Engineering Services (Dallas, TX) where he promotes the application of cutting edge technologies to improve the efficiency and effectiveness of landfill operations. Adam built his knowledge and techniques over a nine-year period as the onsite engineer at McCommas Bluff Landfill in Dallas, TX. His unique experiences in engineering and other fields have combined to create an exceptional understanding of the various challenges inherent in landfill planning, design and operations. Adam can be reached at (214) 789-2326 or e-mail [email protected] or [email protected].

Note

1. With apologies to one of my favorite films from my adolescent years. The correct quote comes from Real Genius (1985) spoken by the character portrayed by Val Kilmer:聽 鈥淚 was thinking of the immortal words of Socrates, who said, 鈥�… I drank what?鈥欌��