Dewatering: The Sequel

Dewatering is poised to be a huge growth industry. Dennis Brunetti, vice president of sales and services with Renegade Oil, predicts that eventually, landfills will stop accepting waste with free liquids making dewatering a forward thinking practice. If that holds true, like all new industries, those that get in first tend to make a name for themselves, winning over customers and customer-loyalty.

“The Stuff That Dreams Are Made Of”

“We recommend the fill and settle system as opposed to the press,” says Brunetti. “We have bought two over the years from Flo Trend in Houston. You’ll also need a dosing station. Eventually, you’ll probably want to add settling tanks, which come in 20,000 to 40,000 gallons to let the product settle out before dewatering. This isn’t a critical step in the process, but something to consider as the business grows.”
Brunetti says that the box itself will last 20-25 years, but the filtering elements inside have lasted about 4-6 years depending on how often you use the box. Grease trap waste is tough on metal.

“When we discovered that the boxes would need their filters replaced, we bought a second box,” says Brunetti. “We can’t have our dewatering facility down for the 7-10 days that it takes to rebuild a box. We rebuild the inside ourselves with stainless steel brackets and fasteners—anything that will be exposed to waste—to try to get as long of a life out of our interior elements as possible.”

Flo Trend’s filters are mounted vertically inside the middle and sides of the tank. Nothing is on the bottom except the steel base of the box. “If the filter is on the bottom then someone can’t shovel out the stuff that doesn’t dump out when you lift the truck,” says Brunetti. “You’ll always have some stick and if there were filters on the bottom, you would risk damaging them. With the filters on the sides, you can go inside with a high pressure hose and it’s like washing down a wall. The filters are very durable, over time we have to do maintenance, but it is a very good system.”

Renegade Oil prefers the fill and settle process because almost no energy is used. They let it settle overnight (6-8 hours) and most of the water weeps out. “We don’t run motors, presses or centrifuges, you just put the product in and let gravity take over. We felt that system was best as opposed to presses or centrifuges. We have a 40 cubic yard box, which holds about 8,100 gallons, and a 30 cubic yard box, which holds about 6,100 gallons. A typical kitchen waste trap will hold 1,000 gallons. So, with a 40 cubic yard box, you can fit waste from eight restaurants.”

Renegade’s system uses a Poly-Mate dosing station from Flo Trend Systems which mixes and injects polymer into the waste. Then the waste goes to the Flo Trend Lime-Mate station where lime is injected before being put in a Flo Trend Sludge Mate roll-off container.

Flo Trend offers a variety of equipment. “The big difference between our Sludge Mates and other companies’ dewatering boxes is that our units don’t have a floor filter,” says Russ Caughman, vice president at Flo Trend. “We found that with a bottom filter, cake tends to stick to it when the box is dumped leaving a build-up of solids that have to be cleaned up when the box is taken back to the customer’s yard. And we’ve found that most of the drainage occurs through the wall filters anyway. Once a cake of an inch or so is built up on the bottom filter, very little water passes through it.” Flo Trend’s Sludge Mate units come in tipping stand-mounted, roll-off, and trailer-mounted styles to help meet your needs.

Suzetta Bonifay, sales manager with AQUA-Zyme Disposal Systems (ADS), says that the life span of an ADS unit is 12-14 years, depending on how well you take care of it.

“A 30 cubic yard dewatering unit typically dewaters 22,000 gallons, if solids are 1 1/2 percent,” says Bonifay. “If your waste is thicker, then you won’t run as many gallons through the unit. Septic and grease trap waste typically averages 1 1/2 percent. It takes about two hours to fill. Meanwhile, it’s draining the whole time. Gradually, solids accumulate on top of the floor filters and the draining slows. The dewatering unit will continue draining for about 24 hours reducing to a half box of solids. The dewatering unit can be picked up with a standard roll-off truck and taken to a landfill, compost site or other disposal site.”

Bucks Fabricating also makes a wide variety of dewatering units that can suit your needs, from 12-26 feet long and combinations of height and capacity, their boxes are made to suit your specifications. Their boxes are made with a high density poly liner to help protect it against corrosive materials. “We can build them with false floors and false sides as well as a center baffle for easy cleaning,” says Dan Webb, sales manager for Bucks Fabricating. “Ours comes with a removable basket, which makes it easy to clean. It also allows the same box to be used for other things.”

Depending on the consistency of the material going in, a regular 4,000 gallon Bucks Fabricating box will fill up and drain out in 4-8 hours. “By then, they will have a landfill acceptable load that will pass the paint filter test.” Passing this test is critical for landfills to accept the cake.

Liquid Assets Disposal in Pennsylvania successfully uses Bucks Fabricating units in their pre-treatment facility. They offer pumpers quick off-loading times and have storage facilities up to 300,000 gallons for rapid, bulk unloading.

Bonifay, with AQUA-Zyme Disposal, recommends pressure washing the dewatering unit right away after every load. “We haul dewatered sludge for several cities,” says Bonifay. “When they run a load, we will pick their unit up after 24 hours. Ideally, they will have two boxes so that we can drop off a clean one when we take the full one to the compost site. We will offload, then wash it out at our site. If they only have one box, then we will still wash it out for them when feasible.”

ADS often rents out their dewatering equipment. They encourage their rental customers to allow them to pick up the equipment as soon as they have finished with it to keep the boxes in optimal working order. “Straight grease trap waste is harsh on metal,” says Bonifay. “If you let that sit in the unit for two or three weeks, it will start to corrode the metal. The important thing is to keep the equipment clean.”

“May the Force Be With You”

Do your homework. Dewatering is not a solution for everyone. There are permits that need to be obtained and regulations vary from state to state. “We always tell the potential customer to check with their local authority to see what kind of permits they need,” says Caughman. “You have to have a plan of getting rid of the water. The cake is normally taken to a landfill for disposal, but we do have customers who take it to composters or land apply it (with permits). In some cases, dewatering has been a solution for them to get solids out of the sludge that typically cause odors so that they can land apply the water.”

“One of our customers installed a large septic tank and drain field on his property and puts the water from his dewatering process in the tank,” says Caughman. “The state allows him to put so many thousands of gallons in each day. We’ve heard from other people who own land that are talking to their own local authorities to do the same. We’ve sold equipment to a company in California that was getting charged because of the high BOD count in effluent water from the dewatering process. So, he designed a system to treat the water before sending it down the sewer. Since then, the city raised their BOD limits and now he can send the water straight to the sewer with no post treatment. These things are always changing.”

If you aren’t building a composting site, aren’t using alternative disposal options, or don’t have a wastewater treatment plant who will negotiate their disposal fees for the water coming from the dewatering unit, then dewatering may not be a viable option for you.

But, for some, price isn’t the only consideration. If their trucks are sitting full of waste then they can’t pump any more septics or grease traps. “We have storage tanks,” says Bonifay. “When we have enough in the tanks, then we start our process of dewatering. The storage tanks allow the trucks and drivers to offload whenever they need to. Some pumpers with smaller trucks come to dispose four times a day. They are able to offload and get back on the road.”

The dewatering box manufacturers interviewed here are happy to talk with you in more detail about your particular situation. They should be one of your first steps in determining if dewatering is an economical solution to your dumping problems. Each manufacturer offers different options, so doing your homework is key if you want to find your happy ending like Renegade Oil and Aqua-Zyme.

Story by Jennifer Taylor


For more information:
AQUA-Zyme Disposal Systems, visit
Bucks Fabricating, visit
Flo Trend Systems, Inc., visit

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