SCS Young Professional, Hydrogeologist Nicole Kron, recently finished her second session of Skype a Scientist, a program in which she Skypes with classrooms and talks to kids about her work as a professional geologist and her journey to become a scientist. The Skype a Scientist program connects students and teachers with people in scientific jobs to help attract kids to science, technology, engineering, and math (STEM) pursuits.
Skype a Scientist matches scientists with classrooms around the world; teachers are able to choose the type of scientist that will match their classroom’s interests. Participating scientists, like Nicole, then skype with the students for 30 to 60 minute Q&A sessions that can cover any topic – from their particular expertise to what it’s like to work as a scientist to their favorite pastimes. The program helps students get to know a “real scientist” and about their career in a STEM arena.
Nicole has completed two sessions so far – one in May and one in June, and she has agreed to stay involved with the program going forward. “It’s so much fun!” she says.
Some of the questions Nicole has answered include:
During these sessions, Nicole talked about geology, work-life balance, self-confidence, and her hobbies. The ninth grade class was particularly interested in her new venture to make French macarons as well as her love of dancing.
Nicole says she really enjoys participating in Skype a Scientist because, “It gives
me the opportunity to show students that scientists and engineers are well-rounded
people with many interests.”
An SCS Marketing Manager, Sarah Hoke, added: “I love to see our folks making an impact in the community.”
It’s never too soon to start recruiting the scientists of the future!
Nicole and Sarah both work at SCS Engineers in the Madison, Wisconsin office. SCS Engineers provides career opportunities across the nation to talented individuals who bring value to their clients and in their communities.
In an increasingly complex regulatory world, Remote Monitoring and Control (RMC) systems provide the tools necessary to improve safety, increase efficiency and make the right decisions quickly. Beyond capturing and storing data, these systems can sort through mountains of data, identify what’s important and deliver meaningful information to operators in real time or as needed.
Some of the added benefits of using RMC systems include:
Read the Waste Today article – click here. Learn more about Remote Monitoring and Control here.
By Ali Khatami
MSW sanitary landfills constantly face the issue of aesthetics due to leachate seeping out of the landfill slopes. Of course, the problem goes away after the construction of the final cover, but the final cover construction may not take place for many years after seeps show up on slopes. To the public, leachate seeps represent a problem with the design of the landfill and possible malfunction of the leachate collection system below the waste, which is an incorrect perception. Such arguments are common and difficult to counter.
Landfill operators use different means to control leachate seeps from landfill slopes and to clean up the unpleasant view of the seep as soon as they can. Innovative solutions to address the issue have been observed and noted in the industry. The degree of effectiveness of the solution to some extent depends on the amount of money spent to address the problem. Some landfills are located in rural areas and the operator may not mind the unpleasant appearance of the slopes, so naturally no urgency in addressing the issue or no money available to take care of the problem.
The environmental side of the leachate seep issue is the impact to surface water quality. If leachate seeps remain unresolved, liquids coming out of slope may eventually reach the landfill perimeter and mix with stormwater in the landfill perimeter ditch. At that point, the operational issue turns into a compliance issue, and regulatory agencies get involved. If the public around the site is on top of their game concerning their opposition to the landfill, they can take the non-compliance issue and turn it into a political issue. At that point, the landfill operator finds himself or herself on the hot plate dealing with the agency and the public on an environmental impact matter.
It always makes sense to stay ahead of the issues and address any potentially sensitive condition before it turns into a major problem. As discussed above, addressing leachate seeps can be done in many different ways, and the operator needs to be prepared to fight for funds to address leachate seeps as they appear on slopes. Availability of funds and willingness of the operator to take necessary action are the primary required elements to stay ahead of the game.
SCS has developed methodologies to address all sorts of leachate seeps on landfill slopes and is uniquely equipped to assist you with a solution. Reach out to a local SCS office for a consultation if you have leachate seep problem at your site.
On April 9, 2018, the U.S. Department of Treasury and the IRS approved Opportunity Zones for: American Samoa; Arizona; California; Colorado; Georgia; Idaho; Kentucky; Michigan; Mississippi; Nebraska; New Jersey; Oklahoma; Puerto Rico; South Carolina; South Dakota; Vermont; Virgin Islands; and Wisconsin. The Treasury Department has made the final designations of Opportunity Zones in more states during June 2018.
Use this interactive map to locate eligible zones in your state.
Opportunity Zones are communities where new investments may be eligible for significant tax incentives. The zones are based on Census Tracts that meet income criteria, and were created in the federal Tax Cuts and Jobs Act of 2017 as a means of helping economically depressed areas through tax incentives for new private investments.
Investors can defer tax on prior gains invested in a Qualified Opportunity Fund (a fund set up to make investments in Qualified Opportunity Zones). In addition, if investors hold the investment in the Opportunity Fund for at least five years they are eligible for capital gains tax reductions or exemptions. If they hold the investment in the Opportunity Fund for at least ten years, they are eligible for an increase in its basis equal to the fair market value of the investment on the date that it is sold.
Brownfields and Opportunity Zones
Many of the communities in the Opportunity Zones have properties impacted by environmental contamination. The Opportunity Zones program provides an economic tool to attract developers and financial backing to communities with brownfield redevelopment needs.
If you are interested in investing in a potential brownfield site, contact SCS Engineers to help you evaluate and manage environmental concerns associated with your site. Visit www.scsengineers.com to learn more.
This paper, presented at A&WMA’s 111th Annual Conference details the Tier 4 process and the potential issues that have arisen from conducting a Tier 4. This paper also assesses potential Tier 4 sites, exceedance reporting, wind monitoring, additional SEM equipment requirements, penetration monitoring, notification and reporting requirements, and impacts on solid waste landfills that will use the Tier 4 SEM procedure for delaying GCCS requirements. This paper reviews the changes between the draft NSPS and the final version of the new NSPS that was promulgated.
Click to read or share the paper, and learn about the authors.
In this blog, we discuss the basics of various wastewater treatment methods in use today including process design parameters, advantages, disadvantages, and costs. Some of the wastewater treatment methods are better suited to landfill leachate treatment than others. For example, the traditional activated sludge wastewater treatment technology, discussed in this article is not suitable for landfill leachates, but it has been modified and improved so that its close cousin – for example the membrane bioreactor (MBR) – is much better suited for landfill leachate treatment. The blog is intended for those who manage projects that include leachate treatment but who are not wastewater or process engineers. We start by grouping treatment systems into three basic categories; biological, physical and chemical. Our first blog in the series focuses on biological treatment.
The oldest treatment technology for sanitary wastewater, with the longest track record, is biological treatment. It is effective for treating the type of wastewater generated by humans because it uses naturally occurring microbes to reduce organics, ammonia and other naturally occurring impurities. The modern version of this time-honored biological treatment process (from the 1960s forward) is known as the basic activated sludge (BAS) process. This is the type of treatment that is used at large publicly owned treatment works (POTWs) and the same form of treatment can be used, on a smaller scale, for landfill leachate. The wastewater to be treated, whether it is sanitary wastewater or landfill leachate, contains organic compounds, nutrients (e.g., nitrogen and phosphorus) and naturally occurring microorganisms. When given the right balance of soluble food, temperature, and oxygen, the microorganism population can be increased rapidly. In multiplying their numbers, the microorganisms absorb some of the food sources (organics) in the wastewater for energy and convert that to new cell mass (through cell growth and reproduction), carbon dioxide (CO2), and water.
The actual BAS treatment process involves pumping the raw wastewater through an open tank, aerating and agitating the liquid by mechanically adding air or oxygen typically through a set of fine bubble diffusers, then after a prescribed time, passing that water to another tank called a clarifier. The process is illustrated below.
The dispersion pattern and the buoyancy of the bubbles promote mixing of the tank contents to ensure the bugs are getting adequate oxygen. An example of a bubble diffuser disc and a typical bubble diffuser bank layout is shown in the two photos below.
A process called nitrification also occurs in the aeration tank. Nitrification is a microbial process by which reduced nitrogen compounds (primarily ammonia) are sequentially oxidized to nitrite and nitrate by the species of microbes called Nitrosomonas, Nitrosospira, Nitrosococcus, and Nitrosolobus.
A biological system, such as a BAS has a susceptibility to some chemicals in leachate that in certain concentrations can be toxic to the “bugs.” For example, high concentrations of ammonia (NH3), chlorides or toxic substances can be harmful. Also, the treatment effectiveness of biological systems drops off significantly at a wastewater temperature lower than about 50 degrees Fahrenheit. Rapid changes in concentrations of these chemicals (or spikes) also can be harmful.
In the clarifier, flocculation chemicals are added to the water to aggregate and help to settle out the cell mass. The cell mass, almost 99% water, is called sludge. Periodically some of the sludge from the clarifier is removed and brought to the front of the process where this “activated” sludge (i.e., air enriched and microbes are alive) is used to seed the incoming wastewater with robust microbial growth and boost the growth of existing organisms that break the organics down. The balance of sludge (called “biosolid”) is removed from the clarifier and is typically dried, disinfected through use of high pH material and or heat and is then used as a soil conditioner directly or as a fertilizer ingredient.
The laboratory measurement of the amount of oxygen that microorganisms use to convert the food to new cell mass is called the biochemical oxygen demand (BOD5). The five day long BOD test was the earliest measure of the organic strength of wastewater and is a rough indication of how much energy (and relative cost) will be expended to treat the wastewater. Landfill leachate is typically considered a strong wastewater compared to municipal wastewater which is considered weak to moderate strength. Many municipal wastewaters are weak because they are heavily diluted with groundwater and infiltration of rainfall.
A key design parameter for any BAS process is the Mixed Liquor Suspended Solids (MLSS). The MLSS is the concentration of suspended solids in the aeration tank. The suspended solids are mostly the active microorganisms that do the work of decomposing the organic substances. The MLSS for a BAS is typically 4,000 to 6,000 mg/l.
Many other water chemistry aspects must be considered with the BAS process. However, these have not been included to simplify this explanation.
Over the decades the BAS process has been modified to address the many different types and strengths of wastewater, increase energy efficiency, reduce treatment times, improve resilience to shock loads, and pollutant removal effectiveness. You may have heard them called Sequencing Batch Reactor (SBR), or powdered activated carbon treatment (PACT). These are variations of the BAS process. Because landfill leachate is somewhat similar in chemical makeup to municipal wastewater, with typically higher chemical constituent concentrations, the landfill sector has successfully borrowed municipal treatment technology. An improvement to the BAS process that started showing up at landfills about 15 to 20 years ago is known as the Membrane Bio-Reactor (MBR) shown here.
The MBR took advantage of advances in micro-manufacturing capability in perfecting synthetic membrane filtration fabric. The membrane, when incorporated in the treatment process, eliminates the need for a clarifier. The membrane works by separating insoluble solids from the water. The advantages of the membrane filtration include;
The membranes are manufactured either as a cylinder shown below-left, or as a flat plate used in a rack outside the BAS reactor, or immersed in the BAS reactor. The diagram shown on the right illustrates the membrane filter process.
Some disadvantages of the MBR can include:
The MBR can manage a much higher MLSS than a conventional BAS; a typical maximum for a BAS is about 4,000 mg/l as compared to around 16,000 mg/l or more in an MBR. The higher MLSS allows for treating a stronger waste stream, and the system has better cold weather and shock load resistance. It can do this because the solids eventually are removed by a membrane. In the BAS process, the chemical treatment in the clarifier forms a large volume of sludge (organic chemicals + microorganisms) that has to be kept in balance by frequent sludge wasting out of the system. Without this wasting, the sludge volume recycled to the aerobic tank would overwhelm the aeration capacity, and the process would collapse. A process flow diagram may look like the one below.
Typically, landfill leachate may need other treatment processes to supplement an MBR system to meet requirements for reducing specific pollutants and other parameters before the treated effluent can be released to the receiving water. One of the key parameters is ammonia (NH3) nitrogen.
Ammonia is produced in the landfill by microorganisms utilizing the organic substances in waste for energy and reproduction in an anaerobic (without oxygen) environment. In an aerobic environment outside the landfill, ammonia can be oxidized by bacteria in a process called nitrification, converting ammonia to nitrite and then to nitrate. When combined with enough phosphorus, nitrates released to surface waters in high enough concentrations can promote algae blooms. The algae blooms typically die off from cold, or their normal lifespan. Large amounts of dead algae compete for oxygen with fish and other wildlife. The result can be fish kills, which can further worsen the water body oxygen depletion problem.
So, in addition to the ammonia being converted to nitrite and then nitrate, the nitrate-nitrogen typically must be removed before discharge of the treated wastewater effluent to surface water. The nitrite and nitrate removal process is known as denitrification and involves reducing the nitrate to nitrogen gas which is inert and not harmful to the environment. Denitrification in the leachate treatment process can be accomplished either by ion exchange, chemical reduction, or biological processes.
The biological method is very common and is typically conducted in a tank known as the anoxic tank. The anoxic tank typically has a filter bed containing the nitrate conversion microorganisms where the nitrate-laden water is passed through for treating. No air is added to maintain an environment that is suitable for the heterotrophic microorganisms that convert nitrate to nitrogen gas. Methanol or acetic acid is typically added to provide a food source for the denitrifying culture in the filters.
Some other key process parameters for the MBR that will affect process sizing and footprint includes the following:
For example, using these unit costs an MBR plant rated at 65,000 GPD would have a basic capital cost of $1.2 to $1.4 million. This does not include a building. The annual operating cost of chemicals and energy only (not including labor), with 90% availability would be $640K to $1.07 million. Extra costs would include; a building if desired or necessary, electrical supply, equalization tank, yard piping, bench and pilot tests, and engineering. These are rough figures to give the reader a sense of the magnitude of costs. Actual costs will differ. It is always best to check with one or more vendors on the unit costs they experience with installations that they provide.
Biological processes have been adapted successfully from the municipal wastewater industry by the wastewater equipment manufacturers who service the solid waste industry to treat landfill leachate. They form the basis of a viable treatment platform that can be expanded depending on the effluent requirements and other design goals. By coupling high-quality membrane filters to remove solids with the BAS-type treatment modifications, MBR plants are revolutionizing leachate treatment. MBR plants are a more efficient and more effective treatment of higher strength leachates. Many vendors are offering modular systems that fit well with the leachate production and growth typical at landfills.
In our next blog, we will discuss membrane filtration systems that are increasingly finding application where leachate has to meet tough discharge standards. Follow SCS Engineers on Twitter, LinkedIn, or Facebook.
Learn more about Liquids Management – Leachate Services
Heat generation in landfills is a natural phenomenon. It happens in every landfill to a degree. Heat generation in landfills accepting organic matter occurs to a higher degree due to organic material biological degradation. Subtitle D landfills accepting organic matter also accept other types of materials that can chemically react under specific conditions to generate additional heat through exothermic reactions.
Recent experience has shown that deep landfills with high levels of organic matter and high levels of moisture in the waste column can potentially create conditions deep within the landfill so that the heat generated cannot escape from the landfill boundaries fast enough. As a result, heat accumulates in the landfill and creates the condition known as elevated temperature landfill or ETLF.
The accumulation of heat causes rising temperatures within the landfill that can adversely affect the beneficial biological degradation of organic waste. Beneficial degradation of organic matter generates methane that is captured by the landfill gas control and collection system (GCCS) and in many instances converted to energy through highly technologically sophisticated systems.
Adversely affected biological degradation of organic waste under high-temperature conditions causes significant increases in the generation of carbon dioxide, hydrogen, and other gasses that have no economic value and can cause other environmental challenges, including regulatory compliance and increased public scrutiny. Additionally, control systems placed in service to address conditions resulting from elevated temperatures can be costly.
If you manage a deep and wet landfill with significant organic matter in your waste stream, you should consider design and operational steps to mitigate future operational and compliance challenges. These might include new engineered features to enhance liquids, gas, and heat removal from the deeper parts of the landfill. Many of the major landfill companies are currently designing and constructing systems to expedite the movement of water and gas through the waste column, which is a great help to potentially minimizing heat accumulations in the landfill.
Significant research work is currently underway to find out causes of heat accumulation in landfills, but it may take years before accurate cause and effect of such complex and inter-relating processes are more clearly determined, and solutions developed. Heat removal by landfill gas and leachate takes place on a regular basis, but the quantities are insignificant to affect a major reduction in accumulated heat in the landfill.
SCS is an expert in the management of elevated temperature landfills and has been promoting the development of heat management systems over the past several years. As a result, we are highly qualified to address heat accumulation in landfills and development of heat removal systems to control temperatures below the landfill surface. If you have an elevated temperature landfill at your facility or a landfill that seems to be progressing in the direction of becoming an elevated temperature landfill in the future, contact us and let us review field data from your facility and develop means to control temperatures below the landfill surface.
Author: Ali Khatami, PhD, PE, LEP, CGC, is a project director and a vice president of SCS Engineers. He is also our National Expert for Landfill Design and Construction Quality Assurance. He has nearly 40 years of research and professional experience in mechanical, structural, and civil engineering.
SCS Engineers recently added ammonia refrigeration Process Safety Management and Risk Management Program (PSM/RMP) Project Director William Lape to their professional team working with industrial clients. Mr. Lape joins the SCS Tracer Environmental team in the firm’s Minneapolis–St. Paul, Minnesota office.
Lape brings his expertise and established reputation as a plant engineering manager, senior environmental health and safety manager, and as the director of environmental health and safety – Process Safety, at Dean Foods (NYSE: DF). Dean Foods is a multi-billion dollar American food and beverage company, and the largest dairy company in the United States.
Ammonia refrigeration is a well-proven and effective refrigerant. It does require special programs and safety precautions called PSM/RMP. Lape’s education, expertise, and experience qualify him for the SCS team who hold safety and efficiency paramount. His experience includes senior positions in the food processing industry, direct management of facility operations and environmental compliance programs. Lape will support SCS clients with refrigeration and food industry changes and energy conservation initiatives while helping to keep their employees and facilities safe from potential toxicity and flammability events.
Lape is also a regulatory lobbyist for the Ammonia Refrigeration industry and is expert in developing and conducting technical and safety training classes. His process safety expertise includes Management of Change, Mechanical Integrity, Compliance Auditing, Process Hazard Analysis facilitation, and writing Operating Procedures. His experience also includes: developing release scenarios and preparing RMP submissions; operating and maintaining large industrial ammonia refrigeration systems; project management with scope and specification generation, cost estimating, scheduling, project oversight and commissioning.
He is formally educated and degreed from Purdue University, an active member in the Refrigerating Engineers and Technicians Association (RETA), sitting on their Board of Directors, and in the International Institute of Ammonia Refrigeration (IIAR) on both the Code and Standards Committees. He has multiple RETA and IIAR certifications; is CVI Certified for U.S Dept. of Homeland Security CFATS, and trained in RCRA & DOT Hazardous Materials Reporting.
“Bill is supporting SCS’s rapid growth in the Upper Midwest and Central U.S. industrial operations by providing increased safety and efficiencies to our private and government clients,” stated Thomas Rappolt, a vice president at SCS Engineers, and office director of SCS Tracer Environmental. “Our customers in the region and nationally will benefit from his valuable expertise managing the staff and protocol for safe and efficient multi-facility and multi-disciplinary facility needs.”
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Typical designs of landfill disposal cells include two slopes, one at the landfill base and the other along the leachate collection pipe. The drainage layer covering the entire cell base area follows the slope of the base toward the leachate collection pipe, and the flow in the leachate collection pipe follows the pipe slope. With the growth in the application of geosynthetics in the landfill industry, the majority of modern landfill designs include a geocomposite drainage layer, unless a granular material is readily available at an economically viable cost in the area of the landfill, which can replace the geocomposite material.
Base slopes are designed to maintain a positive flow toward the leachate collection pipe after long-term settlements of the foundation. In addition to this requirement, sometimes solid waste rules require either a minimum slope at the time of the design or a minimum slope after foundation settlement.
Regulatory agencies go through a comprehensive review process to make sure that such matters are addressed in a solid permit application involving the design of new disposal cells. However, sometimes designers propose slopes that seem to be significantly steeper than the minimum values required in the rules with no supporting foundation settlement analysis to justify the need for the steeper slopes. Slopes steeper than what is required (technically or regulatory-wise) have two drawbacks: 1) loss of the airspace which otherwise would be captured with a less steep slope; 2) lower liquid transmissivity in the geocomposite drainage layer. Laboratory experiments have shown that transmissivity of geocomposites reduces as gradient increases. This phenomenon may be related to higher turbulence in the flow of leachate through the geocomposite voids. The flow path of liquids within the geocomposite structure includes vertical and horizontal barriers that liquid flows around or over within the geocomposite thickness. Steeper slopes increase the velocity of liquids through the geocomposite, and higher velocity makes the flow more turbulent, and the higher turbulence reduces transmissivity.
One of the most important regulatory requirements on a landfill’s bottom lining system drainage layer is that the maximum head of leachate over the liner should not exceed 1 ft. When this requirement was developed, the consensus was that the drainage layer consisted of granular materials. Later, when geonets and geocomposites entered the market, the unwritten consensus among solid waste engineers and regulators was that the maximum head of leachate at the base should not exceed the thickness of the geonet or geocomposite drainage layer. With that in mind, the reduction in transmissivity of geocomposite laid over steeper slopes can adversely impact the maximum leachate head over the liner. Maximum leachate head is normally calculated from the theoretical model (along with some simplifications to disregard very small terms in the theoretical model) developed by C. A. Moore, J.P. Giroud, B. M. McEnroe, and others. One of these models was later incorporated into the Hydrologic Evaluation of Landfill Performance (HELP) model that is currently used by almost all solid waste engineers in the industry. Such model includes a parameter called hydraulic conductivity which is calculated from the transmissivity value of the geocomposite drainage layer. When transmissivity value reduces due to steeper slope at the base, the hydraulic conductivity reduces in turn as well. In the Moore’s and Giroud’s models, the maximum head of leachate is somewhat inversely proportional to the square roots of the hydraulic conductivity, which means the reducing hydraulic conductivity results in an increase in the maximum head of leachate passing through the geocomposite. The relationship between the leachate maximum head and the hydraulic conductivity is a lot more complicated in McEnroe’s model.
It’s recommended that the minimum base slope be initially determined based on foundation settlement. Then, the calculated minimum slope compared to the required value in the solid waste regulations, if any. If the rules require a minimum slope at the time of the design, pick the regulatory value if higher than the calculated minimum slope; otherwise, pick the calculated minimum slope. If the rules require a minimum slope after foundation settlement, then add the calculated minimum slope to the minimum slope in the rules and use that in the design.
A 1 percent slope at the base, provided all requirements are met, seems to be a suitable slope. The geocomposite transmissivity at 1 percent is higher than the transmissivity at 2 percent, and the space difference between the 1 percent and 2 percent slopes can be added to the landfill airspace for waste disposal.
Author: Ali Khatami, PhD, PE, LEP, CGC, is a Project Director and a Vice President of SCS Engineers. He is also our National Expert for Landfill Design and Construction Quality Assurance.
Landfill Design – Information and Case Studies
