leachate disposal

August 23, 2021

Landfill operators forever work to stay on top of a diverse and complex mix of leachate contaminants—heavy metals, ammonia, and biochemical oxygen demand, among them. But lately, they have more to think about, for one: how to keep concentrations of these contaminants within the wastewater treatment plant’s tightening discharge limits. Add to this concern the possibility of more compliance pressure as the list of constituents on regulators’ radar grows. Some operators are preparing for what may be down the pike, from microplastics to PFAS and PFOA—with the latter sometimes called the “elephant in the room.”

Among the strategies, some are exploring on-site leachate treatment options, and there are several. Finding the most fitting, sustainable, and cost-effective one takes vetting. Here is the study of a Florida landfill’s informed decision-making process.

A landfill serving an exploding residential and commercial population recently found itself in a predicament when the overburdened municipal wastewater treatment plant stopped accepting leachate from all county waste operations. Pressed to find a credentialed treatment facility quickly, this SCS Engineers client contracted with a private plant, but the arrangement came with a steep price tag. Overnight, the site’s leachate hauling and disposal costs rocketed from just over three cents a gallon to almost 16 cents a gallon. So, the operator turned to SCS Engineers for help vetting a robust and financially sustainable solution. Ultimately, the client wants to eliminate dependence on a third party and better control its destiny to avoid landing in the same predicament.

In answer, SCS is looking into the feasibility of a system that would clean leachate to drinking water standards to be discharged directly to groundwater. The team is wrapping up a comprehensive study of the site’s current operations, system, and leachate composition as it prepares the client to go out to bid.

“Our goal is to position the landfill to be as independent as possible while providing a cost-effective solution to their leachate treatment,” says SCS Engineers Project Lead Kollan Spradlin. He and the SCS liquid management experts backing him have kicked into high gear because time is money. Right now, the landfill generates about 70,000 gallons a day of leachate through much of the year. In the wet season, that figure spikes to about 150,000 gallons a day. At roughly 16 cents, the landfill can shell out over $24,000 a day for leachate disposal during the wet season.

SCS Engineers’ preliminary work begins with compiling crucial information around current leachate generation and future projections and around site-specific characteristics of the liquids. Next, the team vets multiple leachate treatment systems, sizing up each one against the client’s individual needs to ultimately make a recommendation. And, as important, the team makes sure the operator is very clear on how much upfront capital they need to build an effective, reliable system to do the job.

Spradlin and SCS’s liquid management experts are working on an interim solution while developing a long-term plan. The interim remedy is an evaporator fueled by landfill gas, heats and evaporates water molecules.

“With the evaporator, our client’s private disposal volume is reduced by 50,000 gallons a day, significantly cutting disposal costs. But that’s not enough. We want to reduce that expense further and to manage all or the vast majority of the leachate on-site,” Spradlin says.

The ultimate plan is to design a plant that can treat almost 120,000 gallons a day to a quality that can discharge across a spray field at the facility to groundwater. The landfill saves on disposal costs and owns the system rather than paying for an outside operator’s treatment technology.

This Florida landfill relies on SCS’s site knowledge and its past liquids management experience. SCS’ understanding of the systems and daily operations helped the team develop operational measures already reducing leachate generation to make on-site treatment an option.

“We have completed plan design and construction of their collection, storage, treatment, and disposal systems. And that helped to provide insight into reliable, long-term leachate disposal recommendations,” says Bob Gardner, a 41-year veteran of SCS and part of the team supporting this particular project.

“We had knowledge of site fill sequencing, site conditions, and constraints. And this sped up the process of coming up with a modification that works within their operations and infrastructure,” he says.

All of this foundational background is key to identifying client-centered solutions and presenting a comprehensive data package to vendors. “We give bidders the details they need so they can size their equipment appropriately and provide a more accurate budget estimate. We are trying to eliminate bidder change orders resulting from inadequate background information,” Spradlin says.

The team is thinking ahead, evaluating treatment processes that address a wide range of leachate properties and consider constituents that may be regulated in the future.

“We may put in a reverse osmosis system, a membrane bioreactor, or ultrafiltration to reduce constituent concentrations and take out particulates. We design for flexibility to add more treatment technology on the front end or back end to save the client infrastructure costs in years to come,” Spradlin says.

What differentiates SCS from some other environmental engineering firms is its full-service model and deep bench.

“We touch everything at this landfill. And we have a multidisciplinary team, including national liquid management experts whose knowledge we can tap into at any time. So, we can be one-stop, saving the client from having to go to multiple vendors,” Spradlin says.

Sam Cooke is the lead liquid management expert for this Florida landfill. Like his colleague, Gardner, he knows the wastewater treatment problems landfill operators face; he knows the vendors and their technology. And he understands the importance of relationships—with the client, the state agencies, and every party who is key to the client’s success and the community they serve.

“We fully realize that the wastewater-leachate treatment system we design needs to do its job close to 24/7/365. Moreover, it must do it effectively, sometimes under difficult conditions. So, as we design treatment systems and work with equipment suppliers, facility owners, environmental managers, and treatment system operators, we strive to provide added value and support,” Cooke says.

“In this case, we’re using our knowledge to help our client develop a bid package that addresses specific technical requirements but also meets and helps protect their business and financial goals.”

The team has already met with the regulatory agencies to develop a clear permitting path to accelerate plant deployment and ensure the landfill is fully compliant before making the large transition to direct discharge.

By working with vendors and regulatory representatives well before releasing bid documents, SCS has paved a path to leachate treatment independence.