Geosyntec staff will make a considerable technical contribution to the Global Waste Management Symposium (GWMS) 2018 at the Hyatt Regency Indian Wells Resort & Spa in Indian Wells, California on February 11-14, 2018.

Geosyntec's presenters are Jesse Varsho, Chao Zhou, Nicholas Yafrate, Davis Garrett, Samir Ahmed and Kwasi Badu-Tweneboah. Other attendees are Scott Luettich, Jim Stout, Chriso Petropoulou, Justin Lottig, Mike Minch, and Amy Padovani.

The GWMS 2018 Symposium will deliver content and research on topics including: enhanced landfill temperature, leachate and condensate management, landfill gas and landfill gas management, gas collection and system management, leachate treatment: strategies, case studies, anaerobic digestion, landfill operations, coal combustion cesiduals, and emergency regulatory issues for municipal solid waste (MSW) landfills.

GWMS services the needs of landfill owners and operators, as well as their engineers and the consultant and vendor communities. Join this broad coalition of participants that also includes: facility owners and operators; local, state, and federal agencies; researchers; waste service companies; vendors and suppliers; trade organizations; solid waste generators; and students.

Presentations

• Jesse Varsho - Optimization of Leachate Pretreatment Plant Operations in Response to Complex Leachate Quality
• Chao Zhou - Comprehensive Treatability Evaluation of 1,4-Dioxane Removal from Landfill Leachate
• Nicholas Yafrate - Continued Development of Temperature and Pressure Instrumentation for Elevated Temperature Landfills
• Davis Garrett - Health and Safety Protocols for Investigating Elevated Temperature Landfills
• Samir Ahmed and Kwasi Badu-Tweneboah - Air Emissions Compliance and Emission Rate Analysis for a Municipal Solid Waste Landfill in Florida, USA

Abstracts

Title: Optimization of Leachate Pretreatment Plant Operations in Response to Complex Leachate Quality

Presenter: Jesse Varsho
Date: Tuesday, February 13, 2018
Time: 10:30 a.m. to 12:00 p.m.
Session: Session Five
Abstract:

BACKGROUND

An increasing number of municipal solid waste (MSW) landfills in North America have installed leachate pretreatment plants at their facilities to meet discharge standards or minimize surcharge fees. This presentation discusses the evaluation and implementation process that an existing leachate pretreatment plant (LTP) underwent to optimize their operations to address complex leachate quality caused by elevated temperatures. The elevated temperatures caused leachate to have complex quality such as high concentrations of metals and organic compounds along with low pH. The elevated temperatures were limited in extent and therefore leachate quality varied significantly from different areas of the landfill. The LTP operations were assessed using an integrated approach that included characterization of their leachate within the landfill, treatability studies to test technologies for the removal of heavy metals (iron and mercury) and fats, oils and grease (FOG), characterization of dissolved gases released in the headspace of the LTP units, implementation of odor management strategies of the LTP, and an analysis of the hydraulic capacity of the LTP.

RESULTS

Leachate Characterization Study

The facility implemented a leachate characterization study to accomplish the following objectives: (1) assess the spatial change in leachate quality across the landfill due to areas of elevated temperatures and (2) determine the 24-hour leachate flow and concentration variability at the entrance of the leachate pre-treatment plant. The results of the leachate characterization study showed that leachate from the different parts of the landfill could be segregated into two zones:  leachate that required treatment for removal of heavy metals and FOG to meet the limits set in the landfill's discharge authorization (DA) and leachate that would meet the DA limits (see Figure 1).

The results also showed large variations in heavy metals (Iron and Mercury) and FOG concentrations and therefore, additional equalization was recommended to reduce shock loading of the LTP units, provide adequate pH control and minimize chemical usage, flow surges to the LTP, allow for chemical feed rates within the optimal operating range of dosing equipment, and provide more consistent discharge to the municipal sewer (see Figure 2).

Optimization Evaluation of the LTP

The facility performed a comprehensive and holistic evaluation of the leachate that was being treated including, leachate extraction, storage, and treatment. This integrated approach was developed so that the operation of the leachate treatment plant could be effective and provide a permanent solution to the treatment plant operational concerns. The evaluation consisted of collecting the following information:

1. Field observations of the LTP operations;
2. Operational reports documenting operational and maintenance conditions;
3. Equipment malfunction observations;
4. Hydraulic capacity testing;
5. Leachate characterization data;
6. Leachate treatment plant contaminant profiling;
7. Headspace gas analysis;
8. Bench and field-scale testing results; and
9. Vendor information and standards of practice.

The LTP evaluation determined that there were design and operational improvements that can eliminate potential effluent violations. Implemented design and operational improvements including:  installation a flow and waste load equalization tank(s), optimization of reagent addition and solids separation processes, modification to treatment system recycle stream addition, odor control processes and process control logics modifications.  

CONCLUSIONS

The facility performed a comprehensive leachate evaluation that included characterization of leachate within the landfill to evaluate changes in leachate quality due to elevated temperatures, changes in leachate chemistry through the LTP, bench-scale treatability studies and a hydraulic capacity analysis. The evaluation identified a series of design and operational modifications to the LTP that allowed the facility to be in compliance with its permitted discharge limits, minimized operational costs and allow flexibility in LTP operations with changing leachate characteristics.

Title: Comprehensive Treatability Evaluation of 1,4-Dioxane Removal from Landfill Leachate

Presenter: Chao Zhou
Date: Tuesday, February 13, 2018
Time: 1:30 to 3:00 p.m.
Session: Session Six
Abstract:

1,4-Dioxane (dioxane) is an emerging water contaminant. Several industries including the waste management industry are considered the major sources of 1,4-dioxane. For example, 1,4-dioxane has been detected at elevated concentrations in leachate from both municipal and hazardous waste landfills. Although no federal maximum contaminant level (MCL) exists to date, several states have established stringent regulatory levels at or lower than 1 μg/L. Future discharge of landfill leachate (untreated and treated) to POTWs or surface water may be affected by those extremely low limits.

The objective of this study was to evaluate the feasibility to treat dioxane in leachate at a closed hazardous landfill site (Site) in Southern California to meet the California drinking water Notification Level (NL) of 1 μg/L. Dioxane concentration in the leachate at the Site is approximately 2000 to 3000 μg/L.

Conventional water and wastewater treatment processes do not remove dioxane effectively except for the expensive advanced oxidation process (AOP) technologies, which has long been considered the only "proven"; treatment technology for dioxane by the water industry. Synthetic media adsorption has been recognized as a potential alternative treatment technology for dioxane in contaminated groundwater remediation. However, the effectiveness of AOPs and synthetic media in treating dioxane in landfill leachate still requires careful evaluation since the characteristics of landfill leachate differ significantly from surface water and groundwater. On the other hand, emerging evidence, including initial data collected at the Site, showed dioxane could be degraded in the laboratory by a special group of microorganisms and in the field under certain conditions, but biological removal of dioxane in landfill leachate was not demonstrated conclusively.

This project evaluated dioxane treatment in landfill leachate by bioreactors and AOP processes. Various bench and pilot testing was conducted. It was concluded that AOPs treated the dioxane poorly in both raw and biologically treated leachate, although it was widely considered as the go-to technology for dioxane. It was also found that bioreactors, including the existing activated sludge leachate treatment plant at the Site, and two additional bioreactor configurations which were pilot tested on site, treated dioxane very effectively (>99% removal, Figure 6). Molecular biomarkers confirmed that the removal of dioxane was due to biodegradation. An additional advantage of bioreactors was that they were able to remove organics, ammonia nitrogen, total suspended solids, and other trace constituents required to be removed for discharge.

Additional polishing technologies were investigated to further reduce the dioxane concentrations in the biologically treated leachate, including granular activated carbon (GAC), synthetic media, and a second-stage polishing bioreactor. The performance of GAC adsorption confirmed the consensus in the water industry that it does remove dioxane very well. Synthetic media, which has high affinity to dioxane and can be regenerated on site using superheated steam, did perform well and achieved the treatment objective of the NL. The results of the ongoing bench-scale proof-of-concept testing of the second-stage polishing bioreactor is promising, and the preliminary results indicate further dioxane removal from the biologically treated leachate is achievable.

In summary, this study is the first of its kind comprehensive treatability evaluations of dioxane removal from landfill leachate. The findings are significant for two reasons. First, it indicates that dioxane, an emerging contaminant once thought to be resistant to biodegradation, can be removed at high rates to relatively low concentrations (such as ~10 μg/L or higher) by typical biological leachate treatment under certain conditions. Thus, modifying and/or optimizing the existing biological leachate treatment process could potentially become a cost-effective compliance option where relatively high dioxane limits were imposed. Second, this project preliminarily identified the additional polishing step that can be added downstream of the biological leachate treatment process for dioxane compliance purposes if the dioxane limits are lower. The finding that AOPs, despite being the "gold standard"; for the water industry, did not perform well for the treatment of Site leachate was important and suggests that a site-specific treatability evaluation is needed to minimize risks for AOPs before full-scale implantation. Synthetic media and potentially a second-stage bioreactor are better suited for polishing the biologically treated landfill leachate for the removal of dioxane.

Title: Continued Development of Temperature and Pressure Instrumentation for Elevated Temperature Landfills

Presenter: Nicholas Yafrate
Date: Tuesday, February 13, 2018
Time: 3:30 to 5:00 p.m.
Session: Session Seven
Abstract:
Introduction

Over the last several years the authors have performed extensive work monitoring temperatures and pressures at landfills across the United States. The instrumentation has included fiber optic distributed temperature sensing (FODTS) systems in landfills and vibrating wire piezometers.  The landfills were instrumented to provide in-situ data temperature and pressure data for ongoing analyses of several common traits and factors that may contribute to or be indicative of ET°LF development.

Temperature and Pressure Monitoring Instrumentation for ET°LFs

Landfill temperature monitoring can be performed using traditional point-sensor instrumentation (e.g., thermistors, thermocouples, vibrating wire sensors, etc.) or continuous sensors (i.e., FODTS cables). Pressures within a landfill can be measured using vibrating wire piezometers. Both FODTS and VWP sensors are commonly installed by inserting them in vertical boreholes drilled into the waste.

While previous ET°LF monitoring systems (first installed in 2014) were effective, they were also prone to component failure in the harsh ET°LF environment due to leachate chemistry corroding the sensors and/or large settlement (subsidence) bending/pinching the cables. Based on the experienced gained since 2014, improved monitoring system designs have been developed to increase system longevity, and simplify procedures for repair and/or replacement of fiber optic and vibrating wire sensor systems, as described below.

• Removable sensors – Direct burial of sensors in the waste provides the best temperature transmission from the waste to the sensors, however the sensors are not protected and cannot be removed or replaced without expensive re-drilling. Installation methods that allow for sensors to be extracted, inspected, and replaced if they are damaged without re-drilling has increased the overall value and longevity of the monitoring systems. Specifically, sensors installed in a vertical conduit and/or casing rather than by direct burial (as shown in Figure 7) are protected from damage due to the increased stiffness of the conduit/casing and may be removed and replaced as necessary. Questions have been raised about whether the spatial resolution (vertical precision) of the data is reduced by the conduits/casings, however, thermal modeling and in situ investigations have indicated that, even though the thermal conductivity of conduit materials may be higher that of the waste, heat transferred vertically up or down the conduit comes into equilibrium with the surrounding waste within a very short distance. Hence, the vertical resolution of the instrumentation inside conduits is for all practical purposes as accurate as direct burial configurations.

If conduits and/or casings are used, careful consideration of the following design features is necessary: material type (i.e. stainless steel, CPVC, etc.), perforation or slotting, backfill, and an above-ground seal. Stainless steel and CPVC conduit provide resistance to corrosion and temperature and are therefore suitable for many landfill conditions. Perforations or slotting of the casing and conduit may be used for direct leachate transmission to the sensors and are necessary for pressure measurements. The annulus between the borehole and conduit and or casing are filled with sand or grout backfill to allow for pressure transmission to the sensors. Bentonite layers within the backfill are used to isolate pressure zones. Cord grips or cable glands installed in the conduit cap can be used to hold the sensor cable in place and seal liquid and gas pressure in the conduit.

• Improved cable designs – FODTS cable designs have been recently improved to increase strength and minimize the potential for cable pinching. Stainless steel cable jacketing can provide chemical resistance and cable strength, but is susceptible to pinching. Armored cable with braided or twisted galvanized steel reinforcement and an outer chemical and heat resistant plastic jacket provides enhanced resistance to pinching.
• Pre-fabrication of fiber optic components -  Fiber optics are traditionally assembled and spliced in the field, however this process is very time consuming. With careful planning, the components can be pre-fabricated and installed more efficiently, thereby reducing field time by more than 50% of the time required for field splicing.
• Installation of FODTS cables in leachate collection pipes - FODTS cables can be installed in leachate collection or cleanout pipes to provide temperature measurements near the landfill liner without the risks associated with drilling close to the liner (see Figure 8). The FODTS cables used in these installations are designed to be flexible and resistant to corrosive leachate and elevated temperatures. Installation is accomplished using mechanized trollies that are detached and left in place.  

Ongoing Advancements

In addition to the advancements described above, the authors are currently developing an FODTS remote monitoring system and direct push sensors for landfill use. The remote monitoring system will eliminate the need for field personnel to manually read each instrument and the direct-push sensors will provide an alternative installation method whereby a cone penetrometer (CPT) rig is used to push the sensor to the desired depth instead of drilling holes to install the sensors.

Title: Health and Safety Protocols for Investigating Elevated Temperature Landfills

Presenter: Davis Garrett
Date: Wednesday, February 14, 2018
Time: 8:30 to 9:45 a.m.
Session: Session Eight
Abstract:

Investigating the conditions in ET°LFs often requires invasive activities such as drilling, waste sampling, and installation of instrumentation in dynamic regions of the landfill.  The authors have performed these tasks at more than a dozen ET°LFs, and in so doing, have valuable first-hand experience with how to manage safety hazards and challenges associated with the ET° conditions.  The safety hazards at ET°LFs are grouped in the following categories: (1.) Air Hazards: elevated levels of carbon monoxide, hydrogen, and hydrogen sulfide; potentially explosive conditions; and low levels of oxygen; (2.) Leachate/Hot Liquids; (3.) Pressurized Liquids & Gas; and (4.) Rapid Ground Subsidence (Sinkholes) and Slope Instability.  Mitigation of these hazards requires a combination of engineering and physical controls and purposeful behavioral awareness that work together to reduce the chances for bodily harm, as summarized below.

1. Air Hazards require careful selection of gas monitoring equipment and personal protective equipment (PPE).  Specifically, field personnel are trained in the use of air monitors equipped to detect levels of CO, H2S, O2, and lower explosive limit (LEL).  When air monitor alarms sound, personnel immediately move upwind of the work area and assess response actions.  Results from the gas meters in breathing zones are used to assess the need for respirators or other supplied air especially when working in very close proximity to the top of penetrations in the waste where gases are often the most concentrated.
2. Leachate/Hot Liquids are often manifested as pools and/or seeps of steaming or bubbling liquid on the surface of the waste.   These areas must be avoided to prevent dermal contact with hot liquid.  Similarly, hot liquid is often encountered in waste samples retrieved during drilling and must be recognized and allowed to cool prior to handling.  Proper PPE includes nitrile gloves, complete coverage of skin with Tyvek or similar suits, and face shields with supplemental eye protection.

Figure 9
3. Pressurized Liquids and Gas geysers sometimes occur during drilling and installation of instrumentation at ET°LFs.  These geysers are dangerous because they spew hot liquid, stem, and gas with very little warning.  Along with proper selection of PPE (including face shields), responses to the expulsion pressurized liquid and gas typically requires backing away from the area and allowing the pressure to dissipate. More complex measures and protocols have been developed to mitigate the hazards of hot leachate and high-pressure gas/steam emissions by the advent of back-flow shields retrofitted onto sonic drill rigs and cone penetrometer testing (CPT) equipment to protect the field personnel from exposure to potentially scalding conditions.  High pressure conditions are sometime exacerbated when drill rods or hole casings are left in the waste overnight and are temporarily capped to minimize air emissions and odors.  Whenever possible, the drilling and instllation activities at any given location should be completed and drill rods/casings should be removed within a single work day.  Removal of any capped conditions should be approached with extreme caution as the authors have seen threaded steel caps and geysers be propelled upward more than 50 ft upon removal.  In light of the dangers associated with high-pressure conditions, the authors have also developed wellheads that are installed at permanent locations to allow site gas-control systems to be connected to the conduits and casings thereby venting the system of pressure before personnel approach the instrumentation for maintenance or to obtain readings..

Figure 10
4. Safety hazards from rapid ground subsidence (sinkholes) and slope instability are mitigated by designating situational awareness personnel who observe the field work and the conditions of the landfill surface but are independent of the hands-on activities field work.  The focus of situational awareness personnel is typically to detect cracking or other visible indicators of movement at the landfill surface, and to detect potential emissions of leachate, steam, or gas from nearby features such as gas wellheads which sometimes are precursors to ground instability.  The situational awareness personnel are given authority to stop work and require field personnel to evacuate areas immediately.                          

Figure 11

These procedures have been developed and refined by the authors for health and safety plans and task hazard analyses at several ET°LF sites, based on the experiences gained from the actual field work.  The process of continually re-evaluating and applying experiences and observations for more than three years has allowed over a hundred holes to be drilled with waste sampling and fiber optic and vibrating-wire sensors to be safely installed and monitored at more than a dozen ET°LFs across the U.S. without incident.  It is important to share these experiences and detailed information with other professionals who work at ET°LF sites.

Title: Air Emissions Compliance and Emission Rate Analysis for a Municipal Solid Waste Landfill in Florida, USA

Presenters: Samir Ahmed and Kwasi Badu-Tweneboah
Date: Wednesday, February 14, 2018
Time: 10:00 to 11:15 a.m.
Session: Session Nine
Abstract:

The Indian River County Landfill (IRCL) in Vero Beach, FL recently underwent a Title V Air Operation permit renewal for the year 2017. Title V refers to the 1990 Clean Air Act requiring certain facilities with air pollution sources to obtain an air operating permit. The IRCL facility was issued an initial five year Title V Air Operation permit in 1998, and had renewed the permit every five years through one of the District offices of the Florida Department of Environmental Protection (FDEP). However, the latest renewal application in 2017 had to be processed by the Division of Air Resource Management (DARM) in Tallahassee, Florida as part of an overall centralized permitting system enacted by FDEP in 2013. This presentation focuses on the authors' experience in going through this process with DARM, completing a non-methane organic compound (NMOC) emission rate analysis for the facility, and highlights the recent change to the New Source Performance Standards (NSPS).

More Information

Learn more: Global Waste Management Symposium 2018.
Read the schedule at: Global Waste Management Symposium Schedule.
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