Three Rivers Solid Waste Authority (TRSWA) operates a MSW landfill outside Jackson, South Carolina at which leachate is stored in a collection pond then trucked to a local wastewater treatment plant (WWTP) for treatment. This landfill operates a droplet spraying/misting system (referred to as the Lilypad system) to enhance leachate evaporation and ultimately reduce the quantity of leachate in the pond that requires subsequent treatment. Little work investigating the efficacy in using such a system to enhance leachate evaporation has been reported. The overall goal associated with this study was to quantify the amount of evaporation enhanced by the droplet spraying system and evaluate how the economics of the enhanced leachate evaporation compare to hauling leachate to a WWTP. This was accomplished by performing a water balance on the pond, developing a simple model to link leachate evaporation to the droplet spraying system, and performing an economic evaluation of the system. Overall, results from this work indicate the use of a droplet spraying/misting system to enhance leachate evaporation at on-site storage/collection ponds is effective, resulting in between 2.1 to 2.6 times more evaporation than what would occur naturally. In addition, the economic evaluation of this system indicates that operating the Lilypad system at maximum speed/flow for the greatest number of hours results in saving up to 7% of the total cost when compared to no operation of the Lilypad system.

The Three Rivers Solid Waste Authority (TRSWA) operates a MSW landfill outside Jackson, South Carolina (USA) at which leachate ammonia concentrations are of concern. The landfill operates a droplet spraying/misting system (known as the Lilypad system) in their pond to enhance both leachate evaporation and, possibly, ammonia volatilization. The overall goals of this study were to determine the fate of nitrogen in the pond and to ultimately quantify the role the Lilypad system plays in enhancing ammonia removal. To accomplish the study goals, an empirical model based on collected leachate and mist samples, climatological data, and pond hy-draulic data was developed to quantify the extent of ammonia volatilization, nitrifica- tion, and denitrification that occurred in the pond over the study period. Results from this work indicate that volatilization, nitrification, and denitrification were occurring in the pond, with volatilization of ammonia-nitrogen accounting for the majority of nitrogen removed from the pond. Results also indicate that the Lilypad system has the capability to significantly enhance the volatilization process.

The decomposition of landfilled refuse proceeds through distinct phases, each defined by varying environmental factors such as volatile fatty acid concentration, pH, and substrate quality. The succession of microbial communities in response to these changing conditions was monitored in a laboratory-scale simulated landfill to minimize measurement difficulties experienced at field scale. 16S rRNA gene sequences retrieved at separate stages of decomposition showed significant succession in both Bacteria and methanogenic Archaea. A majority of Bacteria sequences in landfilled refuse belong to members of the phylum Firmicutes, while Proteobacteria levels fluctuated and Bacteroidetes levels increased as decomposition proceeded. Roughly 44% of archaeal sequences retrieved under conditions of low pH and high acetate were strictly hydrogenotrophic (Methanomicrobiales, Methanobacteriales). Methanosarcina was present at all stages of decomposition. Correspondence analysis showed bacterial population shifts were attributed to carboxylic acid concentration and solids hydrolysis, while archaeal populations were affected to a higher degree by pH. T-RFLP analysis showed specific taxonomic groups responded differently and exhibited unique responses during decomposition, suggesting that species composition and abundance within Bacteria and Archaea are highly dynamic. This study shows landfill microbial demographics are highly variable across both spatial and temporal transects.

The Environmental Research and Education Foundation (EREF) recently completed a study to quantify the amount of MSW managed in the United States. The study represents the first to use a bottom-up, facility-based methodology in the U.S. to improve accuracy and more discretely track the amount of waste managed. Over 9,000 facilities managing municipal solid waste (MSW) were identified through the course of the study (landfills, WTE incinerators, recycling facilities, composting operations, and anaerobic digesters), and information on the amount and types of waste managed were collected. Results suggest 1.4 times more MSW is managed in 2013 than previously suggested by U.S. Environmental Protection Agency (U.S. EPA) estimates. Data show that the majority of MSW was landfilled and the least amount of tonnage was composted.​

Landfill functional stability provides a target that supports no environmental threat at the relevant point of exposure in the absence of active control systems. With respect to leachate management, this study investigates “gateway” indicators for functional stability in terms of the predictability of leachate characteristics, and thus potential threat to water quality posed by leachate emissions. Historical studies conducted on changes in municipal solid waste (MSW) leachate concentrations over time (longitudinal analysis) have concentrated on indicator compounds, primarily chemical oxygen demand (COD) and biochemical oxygen demand (BOD). However, validation of these studies using an expanded database and larger constituent sets has not been performed. This study evaluated leachate data using a mixed-effects regression model to determine the extent to which leachate constituent degradation can be predicted based on waste age or operational practices. The final dataset analyzed consisted of a total of 1402 samples from 101 MSW landfills. Results from the study indicated that all leachate constituents exhibit a decreasing trend with time in the post-closure period, with 16 of the 25 target analytes and aggregate classes exhibiting a statistically significant trend consistent with well-studied indicators such as BOD. Decreasing trends in BOD concentration after landfill closure can thus be considered representative of trends for many leachate constituents of concern.

Refuse decomposition in landfills is a microbially mediated process that occurs primarily under anaerobic conditions. Because of limited moisture conditions, hydraulic transport as a means of cellular translocation within the landfill appears limited, especially during the initial stages of decomposition. Thus, microbial communities within the incoming refuse serve as a primary source of facultative and obligate anaerobic microorganisms that initiate refuse decomposition. Fresh residential refuse was collected five times over 26 months, and microbial communities in these samples were compared with those in individual refuse components and decomposed refuse. Bacterial and archaeal community structures were determined using T-RFLP. The Bacterial microbial community richness was correlated (r(2) = 0.91) with seasonal differences in ambient air temperature. Analysis of the results shows that fresh refuse is most likely not the source of methanogens in landfills. Microbial communities in the solid and leachate phases were different, indicating that both matrices must be considered when characterizing microbial diversity within a landfill.

ABSTRACT The initiation of methanogenesis in refuse occurs under high volatile fatty acid (VFA) concentration and low pH (5.5 to 6.25), which generally are reported to inhibit methanogenic Archaea . One hypothesized mechanism for the initiation of methanogenesis in refuse decomposition is the presence of pH-neutral niches within the refuse that act as methanogenesis initiation centers. To provide experimental support for this mechanism, laboratory-scale landfill reactors were operated and destructively sampled when methanogenesis initiation was observed. The active bacterial and archaeal populations were evaluated using RNA clone libraries, RNA terminal restriction fragment length polymorphism (T-RFLP), and reverse transcription-quantitative PCR (RT-qPCR). Measurements from 81 core samples from vertical and horizontal sections of each reactor showed large spatial differences in refuse pH, moisture content, and VFA concentrations. No pH-neutral niches were observed prior to methanogenesis. RNA clone library results showed that active bacterial populations belonged mostly to Clostridiales , and that methanogenic Archaea activity at low pH was attributable to Methanosarcina barkeri . After methanogenesis began, pH-neutral conditions developed in high-moisture-content areas containing substantial populations of M. barkeri . These areas expanded with increasing methane production, forming a reaction front that advanced to low-pH areas. Despite low-pH conditions in >50% of the samples within the reactors, the leachate pH was neutral, indicating that it is not an accurate indicator of landfill microbial conditions. In the absence of pH-neutral niches, this study suggests that methanogens tolerant to low pH, such as M. barkeri , are required to overcome the low-pH, high-VFA conditions present during the anaerobic acid phase of refuse decomposition.

Landfills represent a unique microbial ecosystem and play a significant role in global biogeochemical processes. The study of complex ecosystems such as landfills using DNA-based techniques can be advantageous since they allow for analysis of uncultured organisms and offer higher resolution in measuring demographic and metabolic (functional) diversity. However, sample acquisition and processing from refuse is challenging due to material heterogeneity. Decomposed refuse was used to evaluate the effect of seven sample processing methods on Bacteria and Archaea community structure using T-RFLP. Bias was assessed using measured richness and by comparing community structure using multi-dimensional scaling (MDS). Generally, direct methods were found to be most biased while indirect methods (i.e., removal of cellular material from the refuse matrix before DNA extraction) were least biased. An indirect method using PO4 buffer gave consistently high bacterial and archaeal richness and also resulted in 28 and 34% recovery of R. albus and M. formicicum spiked into refuse, respectively. However, the highest recovery of less abundant T-RFs was achieved using multiple processing methods. Results indicate differences in measured T-RF diversity from studies of landfill ecosystems could be caused by methodological (i.e., processing method) variation rather than refuse heterogeneity or true divergence in community structure.

Non-hazardous industrial process wastes are receiving increased interest from landfill owners, especially with respect to bioreactor operation. These wastes could benefit bioreactors as they represent sources of liquid, nutrients, and/or substrate as well as revenue. However, landfill operators should exercise caution in accepting these wastes, as some could have detrimental effects on refuse decomposition. In this research, the use of laboratory-scale tests to evaluate the effect of one such waste on refuse decomposition is demonstrated. The waste evaluated, referred to as burnt sugar, is an acidic byproduct of corn-based polylactic acid production and represents a source of readily-biodegradable carbon. Lactic acid was the primary constituent of the BS at 0.73 g/g and the COD was measured at 1230 mg COD/g. Testing protocols were adapted to address the specific concerns surrounding the material. Abiotic dissolution tests conducted at mesophilic temperatures indicated that the majority of the waste dissolved into leachate recirculated over a layer of the waste within several days. Abiotic mixing tests suggested that the waste would acidify refuse to pH 6.41 at a loading of 21.9 g/dry kg refuse. However, in biologically active tests, the refuse was able to convert loadings as high as 196.7 g/dry kg refuse to methane. As the loadings increased toward and beyond this level, pronounced detrimental effects to the refuse ecosystem were observed, including a decrease in pH, accumulation of volatile fatty acids and COD, and lag in methane production. The results suggested that actively decomposing refuse has the potential to attenuate relatively high loading of a rapidly degradable but acidic substrate. Nonetheless, caution in the implementation of a field program to accept rapidly biodegradable acidic wastes is critical.

Eleven statewide waste characterization studies were compared to assess variation in the quantity and composition of waste after separation of recyclable and compostable materials, i.e., discarded waste. These data were also used to assess the impact of varying composition on sequestered carbon and methane yield. Inconsistencies in the designation of waste component categories and definitions were the primary differences between study methodologies; however, sampling methodologies were consistent with recommended protocols. The average municipal solid waste (MSW) discard rate based on the statewide studies was 1.90 kg MSW person(-1) day(-1), which was within the range of two national estimates: 2.35 and 1.46 kg MSW person(-1) day(-1). Dominant components in MSW discards were similar between studies. Organics (food waste, yard trimmings), paper, and plastic components averaged 23.6 +/- 4.9%, 28.5 +/- 6.5%, and 10.6 +/- 3.0% of discarded MSW, respectively. Construction and demolition (C&D) waste was 20.2 +/- 9.7% of total solid waste discards (i.e., MSW plus C&D). Based on average statewide waste composition data, a carbon sequestration factor (CSF) for MSW of 0.13 kg C dry kg MSW-1 was calculated. For C&D waste, a CSF of 0.14 kg C dry kg C and D waste(-1) was estimated. Ultimate methane yields (L-o) of 59.1 and 63.9 m(3) CH4 wet Mg refuse(-1) were computed using EPA and state characterization study data, respectively, and were lower than AP-42 guidelines. Recycling, combustion, and other management practices at the local level could significantly impact CSF and (L-o) estimates, which are sensitive to the relative fraction of organic components in discarded MSW and C&D waste.

Chapter 12 Anaerobic Biodegradation of Solid Waste Morton A. Barlaz, Morton A. Barlaz Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USASearch for more papers by this authorBryan F. Staley, Bryan F. Staley Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USASearch for more papers by this authorFrancis L. de los Reyes III, Francis L. de los Reyes III Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USASearch for more papers by this author Morton A. Barlaz, Morton A. Barlaz Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USASearch for more papers by this authorBryan F. Staley, Bryan F. Staley Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USASearch for more papers by this authorFrancis L. de los Reyes III, Francis L. de los Reyes III Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina, USASearch for more papers by this author Book Editor(s):Ralph Mitchell, Ralph Mitchell Laboratory of Applied Microbiology, Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts, USASearch for more papers by this authorJi-Dong Gu, Ji-Dong Gu Division of Microbiology, School of Biological Sciences, The University of Hong Kong, Hong Kong, ChinaSearch for more papers by this author First published: 16 December 2009 https://doi.org/10.1002/9780470495117.ch12Citations: 22 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Summary This chapter contains sections titled: Introduction and Objectives Solid Waste Composition and Management Introduction to Landfills Anaerobic Decomposition of Solid Waste Landfill Microbiology Alternative Biological Processes Summary References Citing Literature Environmental Microbiology, Second Edition RelatedInformation

Landfill gas contains numerous speciated organic compounds (SOCs) including alkanes, aromatics, chlorinated aliphatic hydrocarbons, alcohols, ketones, terpenes, chlorofluoro compounds, and siloxanes. The source, rate and extent of release of these compounds are poorly understood. The objective of this study was to characterize the release of SOCs and the regulated parameter, non-methane organic compounds (NMOCs) during the decomposition of residential refuse and its major biodegradable components [paper (P), yard waste (YW), food waste (FW)]. Work was conducted under anaerobic conditions in 8-L reactors operated to maximize decomposition. Refuse and YW were also tested under aerobic conditions. NMOC release during anaerobic decomposition of refuse, P, YW, and FW was 0.151, 0.016, 0.038, and 0.221 mg-C dry g(-1), respectively, while release during aerobic decomposition of refuse and YW was 0.282 and 0.236 mg-C dry g(-1), respectively. The highest NMOC release was measured under abiotic conditions (3.01 mg-C dry g(-1)), suggesting the importance of gas stripping. NMOC release was faster than CH4 production in all treatments. Terpenes and ketones accounted for 32-96% of SOC release in each treatment, while volatile fatty acids were not a significant contributor. Release in aerobic systems points to the potential importance of composting plants as an emissions source.