Florida Water Resources Journal — June 2012 - Biosolids Management & Bio-Energy Production
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Sludge Hauling: Lessons Learned
Dennis Hart

As operators and treatment plant managers, we don’t always get involved in contracts involving our facilities. Most contracts are left up to purchasing managers, and if we do get to review them prior to being bid out, it’s the exception rather than the rule. A series of events happened to me, however, that may make you think differently about how contracts are handled.<br /> <br /> Our facility recently installed remote cameras for security reasons. We had too much uncontrolled traffic passing through the facility, and subsequently, fuel and other items were missing. As an afterthought, I also wanted to improve the monitoring of the sludge presses and the sludge trailer as it was filling, thereby reducing the operator time needed to oversee the press operations. Once the cameras were in place, we gained much better response time to press problems by monitoring the gravity zone, and were able to adjust the gates to gain a more even fill of the trailers.<br /> <br /> Shortly after observing the trailer filling and making camera focus adjustments, I noticed sludge remaining in the trailers. At first I didn’t think much of it; it just didn’t all fall out. Then one day the sludge looked particularly deep and I climbed into the trailer to measure the stuck sludge. I found 8 to 10 inches of sludge remaining, which upon calculation was 28 percent of the available height of the 35 inches of depth available. With over $100,000 a year in hauling costs, this meant we were losing significant value since we were paying for each load, assuming a 35-yard load with each truck.<br /> <br /> We first tried several measures to “unstick” the sludge, including coating the trailers with diesel fuel, polymer, and soap. Needless to say, this was labor intensive and not very effective. Our next course of action was to contact the purchasing department and change the contract to tons hauled versus the existing loads. We thought that would fix the problem—but there were more factors to consider.<br /> <br /> As it turned out, the contractor could use the tier weight of the empty trailer to be subtracted from the weight into the landfill. This, however, didn’t solve the sludge sticking issue and we were still paying for the sludge stuck in the trailer. I spoke with a landfill supervisor who advised me that it was common practice for haulers who were paid by the load, especially if the load was enclosed or not normally observed, to leave part of the load in the truck; this applied to garbage trucks as well. Think of it: Leaving 20 percent in a trailer or truck results in the hauler being paid for 20 percent of unjustified hauling. The hauler, in our case, tried to empty the trailer by shaking the hydraulics and tying up his drivers at the landfill for an excessive amount of time, but to no avail.<br /> <br /> Ultimately, we found out that we could require the hauler to weigh in and out and be charged for sludge dumped instead of sludge hauled. We also had the landfill bill us directly for the tons versus billing the hauler, who would then bill us for loads.<br /> <br /> I suspect most contracts are already based on tons, but if you don’t weigh the loads in and out you could be paying too much. It was definitely worth it for us to look at the “empty” trailers and optimize our contract. Without our security cameras, we wouldn’t have been able to remotely observe the press operations and uncover this huge cost savings.<br /> <br /> Dennis Hart is a former plant supervisor at South Central Water Reclamation Facility for Brevard County.
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