Process Analysis of Anaerobic Fermentation Exposure to Metal Mixtures.

Anaerobic fermentation is a cost-effective biowaste disposal approach. During fermentation, microorganisms require a trace amount of metals for optimal growth and performance. This study investigated the effects of metal mixtures on biogas properties, process stability, substrate degradation, enzyme activity, and microbial communities during anaerobic fermentation. The addition of iron (Fe), nickel (Ni), and zinc (Zn) into a copper (Cu)-stressed fermentation system resulted in higher cumulative biogas yields, ammonia nitrogen (NH4+-N) concentrations and coenzyme F420 activities. Ni and Zn addition enhanced process stability and acetate utilization. The addition of these metals also improved and brought forward the peak daily biogas yields as well as increased CH4 content to 88.94 and 86.58%, respectively. Adding Zn into the Cu-stressed system improved the abundance of Defluviitoga, Fibrobacter and Methanothermobacter, the degradation of cellulose, and the transformation of CO2 to CH4. The bacterial and archaeal communities were responsible for the degradation of lignocelluloses and CH4 production during the fermentation process. This study supports the reutilization of heavy metal-contaminated biowaste and provides references for further research on heavy metals impacted anaerobic fermentation.

Degradation of endosulfan by high-energy ball milling with CaO: process and mechanism.

Mechanochemical degradation (MCD) technology has shown its remarkable potential in the disposal of persistent organochlorines in a non-combustion manner. In the present study, endosulfan, as the newly listed persistent organic pollutants (POPs) in the Stockholm Convention, was investigated for its feasibility of mechanochemical destruction using high-energy ball milling. Using calcium oxide (CaO) as a co-milling reagent, the degradation efficiency of endosulfan was nearly 100% after ball milling for 60 min, while the dechlorination efficiency and the sulfate formation efficiency were delayed for endosulfan degradation. After ball milling for 120 min, the dechlorination efficiency and sulfate formation efficiency reached 87.55% and 26.28%, respectively. Based on the measurement results from various material characterization approaches, the main degradation pathway of endosulfan was proposed as sequential dechlorination followed by the destruction of hydrocarbon skeleton. The GC-MS analysis confirmed that complete desulfurization and dechlorination had been realized finally. This study provides an option for the way toward the efficient and rapid destruction of endosulfan as a new POPs using mechanochemical technology.

Single pot bioprocessing for ethanol production from biogenic municipal solid waste.

Burgeoning global energy demand and rapid diminution of fossil fuel reserves urged to seek for a sustainable energy source like bioethanol. Single pot bioprocessing (SPB) strategy employing in-house laccase, cellulase plus xylanase and amylase along with hexose and pentose sugar fermenting yeasts (Saccharomyces cerevisiae and Pichia stipitis) is designed in this study for ethanol production from biogenic municipal solid waste (BMSW). BMSW when subjected to simultaneous pretreatment and saccharification (SPS) resulted in 79.69% enzymatic digestibility and fared better compared to alkali pretreated counterparts (14.03%-51.10%). The maximum total sugar release in case of SPS was 146.9 g/L in 24 h. The maximum ethanol concentration of 5.24% (v/v) in 30 h was obtained from SPB of BMSW at 25% (w/v) solid loading. SPB for ethanol production from BMSW is an interesting and effective alternative to MSW going to landfill or incineration with an added perk of waste to wealth conversion.

Methane oxidation coupled to denitrification under microaerobic and hypoxic conditions in leach bed bioreactors.

Managing nitrogen and carbon cycles in landfills is an environmental challenge. In this study, our purpose was to test two types of methane oxidation processes coupled to denitrification inside landfills: microaerobic and hypoxic methane oxidation coupled to denitrification (MAME-D and HYME-D). Leach bed bioreactors were designed and operated for >100 d with NO3--N concentration ranging from 100 to 400 mg N/L. During six runs of the leach bed bioreactor experiment, leach bed bioreactor 2 (MAME-D) reached 100% denitrification efficiency and the highest average specific denitrification rate of 20.36 mg N/(L·d) in run 5, while leach bed bioreactor 3 (HYME-D) achieved 75% denitrification efficiency and the highest average specific denitrification rate of 8.09 mg N/(L·d) in run 6. Subsequently, waste from leach bed bioreactors 1, 2, and 3 was inoculated into anaerobic bottles to run a batch experiment for 13 d. The total consumed methane, oxygen, and nitrate amounts in the microaerobic system with no methane and oxygen supplement were 2.33, 2.38, and 2.04 mmol, respectively, which almost matched the theoretical equation of aerobic methane oxidation coupled to denitrification. In the hypoxic system, the total consumed methane and nitrate amounts were 0.23 and 0.41 mmol, respectively, the ratio of which closely matched the HYME-D. In addition, via the diverse functional community analysis, methane oxidation in the microaerobic system was confirmed to be conducted by methanotrophs (i.e., Methylobacter and Methylomonas) using oxygen as an electron acceptor. Subsequently, the generated organic compounds could support denitrifiers (i.e., Methylophilaceae) to complete denitrification. In the hypoxic system, Methylomonas and Methylobacter utilized nitrate as a direct electron acceptor to oxidize methane. The two landfill processes characterized here will expand our understanding of the environmental role of methanotrophs and methylotrophs in both carbon and nitrogen cycles.

Network Design for Municipal Solid Waste Collection: A Case Study of the Nanjing Jiangbei New Area.

Garbage collection is an important part of municipal engineering. An effective service network design can help to reduce the municipal operation cost and improve its service level. In this paper, we propose an optimization model for the network design of municipal solid waste (MSW) collection in the Nanjing Jiangbei new area. The problem was formulated as a mixed integer nonlinear programming (MINLP) model with an emphasis on minimizing the annual operation cost. The model simultaneously decides on the optimal number of refuse transfer stations (RTSs), determines the relative size and location for each RTS, allocates each community to a specific RTS, and finally identifies the annual operation cost and service level for the optimal scenario as well as other scenarios. A custom solution procedure which hybrids an enumeration rule and a genetic algorithm was designed to solve the proposed model. A sensitivity analysis was also conducted to illustrate the impact of changes in parameters on the optimality of the proposed model. Test results revealed that our model could provide tangible policy recommendations for managing the MSW collection.

A new strategy to control the proliferation of microorganisms in solid hospital waste and the diffusion of nosocomial infections.

A possible tool to reduce nosocomial infections is to identify unknown sources of contamination and then to provide a measure for controlling the related infections. In this study, solid hospital waste was considered a potential source of contamination, and a strategy to reduce the potential risk of pathogen contamination was tested. This paper describes a novel technique for waste management in healthcare settings with a view to facilitating infection prevention and control. We explored the innovative use of sodium dichloroisocyanurate (NaDCC) by investigating the microbicidal activity of chlorine, which derives from the hydrolysis of NaDCC mediated by humidity, and by testing its effect on the inhibition of microorganism growth. NaDCC was inserted in a solid hospital waste bin containing also Lauria-Bertani agar plates, with different dilutions of a known titre of three different microorganisms, namely Escherichia coli, Staphylococcus aureus and Aspergillus brasiliensis. The plates were incubated in the container with or without the antimicrobial agent (control, CNT) at room temperature for 5 days. The number of colony-forming units (CFUs) present on each plate was then counted. Microorganisms capable of proliferating in the CNT waste bin were not able to grow in the presence of NaDCC. Furthermore, the molecular chlorine which developed and was released in the waste bin under the experimental conditions (T=20°C, t=5 days) was quantified using iodometric titration. NaDCC hydrolysis, mediated by humidity, has a strong and long-lasting microbicide effect. The proliferation of tested bacteria and fungi is totally inhibited. These results demonstrate the effectiveness of NaDCC in controlling and/or inhibiting microbial proliferation and support its possible use in the treatment of hospital waste to control the spread of nosocomial contamination.

Metal leaching from refinery waste hydroprocessing catalyst.

The present study aims to develop an eco-friendly methodology for the recovery of nickel (Ni), molybdenum (Mo), and vanadium (V) from the refinery waste spent hydroprocessing catalyst. The proposed process has two stages: the first stage is to separate alumina, while the second stage involves the separation of metal compounds. The effectiveness of leaching agents, such as NH4OH, (NH4)2CO3, and (NH4)2S2O8, for the extraction of Mo, V, Ni, and Al from the refinery spent catalyst has been reported as a function of reagent concentration (0.5 to 2.0 molar), leaching time (1 to 6 h), and temperature (35 to 60°C). The optimal leaching conditions were achieved to obtain the maximum recovery of Mo, Ni, and V metals. The effect of the mixture of multi-ammonium salts on the metal extraction was also studied, which showed an adverse effect for Ni and V, while marginal improvement was observed for Mo leaching. The ammonium salts can form soluble metal complexes, in which stability or solubility depends on the nature of ammonium salt and the reaction conditions. The extracted metals and support can be reused to synthesize a fresh hydroprocessing catalyst. The process will reduce the refinery waste and recover the expensive metals. Therefore, the process is not only important from an environmental point of view but also vital from an economic perspective.

Removal of odorous compounds emitted from a food-waste composting facility in Korea using a pilot-scale scrubber.

Monitoring and control of odorous compound emissions have been enforced by the Korean government since 2005. One of the point sources for these emissions was from food waste composting facilities. In this study, a pilot-scale scrubber installed in a composting facility was evaluated for its performance in the removal of malodorous compounds. The exhaust stream contained ammonia and methylamine as the major odorants detected by the threshold odor test and various instrumental techniques (GC-FID, FPD, MS and HPLC/UV). For the scrubber operation, the column was randomly packed with polypropylene Hi-Rex 200, while aqueous sulfuric acid was selected as the scrubbing solution. To achieve 95% removal, the scrubber must be operated by using H2SO4 solution with pH at < 6.5, liquid to gas ratio > 4.5, gas loading rate < 1750 m3/m3-hr and contact time < 0.94 s. The scrubber performance was further evaluated by determining the mass transfer coefficients and then monitoring for 355 days of operation. The pilot-scale scrubber maintained > 95% ammonia and methylamine removal efficiencies despite the fluctuations in the inlet (from composting facility exhaust stream) concentration. The optimum operating conditions and scrubber performance indicators determined in this study provides a basis for the design of a plant-scale scrubber for treatment of composting facility gas emissions.

Municipal solid waste generation and disposal in Robe town, Ethiopia.

The amount of solid waste generated in developing countries is rising over time due to economic growth, change inconsumer behavior, and lifestyles of people. But it is hard to manage and handle the increase of solid waste with existing waste management infrastructure. Thus, the management system of solid waste is very poor and has become a serious problem. The main purpose of this study is to quantify the volume of solid waste generated and investigate factors affecting generation and disposal of wastes in the study area. The result of this study indicated that total waste generated from households was about 97.092 kg/day. Furthermore, the study reveals that the solid waste generation rate of the town is 0.261 kg/person/day. About 57.5% of solid waste is properly disposed of to a landfill site, whereas the remaining 42.5% is illegally dumped at the roadsides and open fields. Implications: Nowadays, in developing countries there is a high concentration of people in urban areas, causing the generation of an enormous concentration of municipal waste in urban areas. Therefore this study's findings will be important for various policymakers and town planners. This may also serve as a benchmark for the municipal authorities of the town for whom the problem is still invisible and negligible and can push environmental protection authorities to reexamine the implementation of their policies and strategies with regard to the broader issues of human and environmental health conditions of town dwellers.

Recovery of Macro and Micro-Nutrients by Hydrothermal Carbonization of Septage.

In this study, septic tank waste (i.e., septage) was hydrothermally carbonized (HTC) in order to recover macro and micronutrients, while tracking the fate of residual heavy metals. Three different HTC temperatures (i.e., 180, 220, and 260 °C) at autogenous pressures and two reaction times (i.e., 30 and 120 min) were applied on both solid and liquid septages. Hydrochar and HTC process liquids were characterized using ICP, CHNS, and UV-vis spectroscopy. Treatment at 260 °C for 120 min maximized ammonia recovery, producing a liquid with 1400 mg/L of ammonia. Overall, about 70% of available nitrogen ended up in the liquid phase as nitrate or ammonia. Solid hydrochars show potential for fertilizer use, with high phosphorus content of 100-130 kg/tonne. It was found that heavy metals mainly remained in the solid phase, although the concentrations of heavy metals are mostly lower than U.S. EPA regulation for biosolids with the exception of selenium.

An assessment of the potential use of compost filled plastic void forming units to serve as vents on historic landfills and related sites.

Much of the solid municipal waste generated by society is sent to landfill, where biodegrading processes result in the release of methane, a major contributor to climate change. This work examined the possibility of installing a type of biofilter within paved areas of the landfill site, making use of modified pervious paving, both to allow the escape of ground gas and to avoid contamination of groundwater, using specially designed test models with provision for gas sampling in various chambers. It proposes the incorporation of an active layer within a void forming box with a view to making dual use of the pervious pavement to provide both a drainage feature and a ground gas vent, whilst providing an active layer for the oxidation of methane by microbial action. The methane removal was observed to have been effected by microbial oxidation and as such offers great promise as a method of methane removal to allow for development of landfills.

The impact of nanoparticles on aerobic degradation of municipal solid waste.

The amount of nanoparticles released from industrial and consumer products has increased rapidly in the last decade. These products may enter landfills directly or indirectly after the end of their useful life. In order to determine the impact of TiO2 and Ag nanoparticles on aerobic landfilling processes, municipal solid waste was loaded to three pilot-scale aerobic landfill bioreactors (80 cm diameter and 350 cm height) and exposed to TiO2 (AT) and Ag (AA) nanoparticles at total concentrations of 100 mg kg-1 of solid waste. Aerobic landfill bioreactors were operated under the conditions about 0.03 L min-1 kg-1 aeration rate for 250 days, during which the leachate, solid waste, and gas characteristics were measured. The results indicate that there was no significant difference in the leachate characteristics, gas constituents, solid quality parameters, and temperature variations, which are the most important indicators of landfill operations, and overall aerobic degradation performance between the reactors containing TiO2 and Ag nanoparticles, and control (AC) reactor. The data also indicate that the pH levels, ionic strength, and the complex formation capacity of nanoparticles with Cl- ions can reduce the toxicity effects of nanoparticles on aerobic degradation processes. The results suggest that TiO2 and Ag nanoparticles at concentrations of 100 mg kg-1 of solid waste do not have significant impacts on aerobic biological processes and waste management systems.

Assessment of micro-scale anaerobic digestion for management of urban organic waste: A case study in London, UK.

This paper describes the analysis of an AD plant that is novel in that it is located in an urban environment, built on a micro-scale, fed on food and catering waste, and operates as a purposeful system. The plant was built in 2013 and continues to operate to date, processing urban food waste and generating biogas for use in a community café. The plant was monitored for a period of 319days during 2014, during which the operational parameters, biological stability and energy requirements of the plant were assessed. The plant processed 4574kg of food waste during this time, producing 1008m3 of biogas at average 60.6% methane. The results showed that the plant was capable of stable operation despite large fluctuations in the rate and type of feed. Another innovative aspect of the plant was that it was equipped with a pre-digester tank and automated feeding, which reduced the effect of feedstock variations on the digestion process. Towards the end of the testing period, a rise in the concentration of volatile fatty acids and ammonia was detected in the digestate, indicating biological instability, and this was successfully remedied by adding trace elements. The energy balance and coefficient of performance (COP) of the system were calculated, which concluded that the system used 49% less heat energy by being housed in a greenhouse, achieved a net positive energy balance and potential COP of 3.16 and 5.55 based on electrical and heat energy, respectively. Greenhouse gas emissions analysis concluded that the most important contribution of the plant to the mitigation of greenhouse gases was the avoidance of on-site fossil fuel use, followed by the diversion of food waste from landfill and that the plant could result in carbon reduction of 2.95kg CO2eq kWh-1 electricity production or 0.741kg CO2eq kg-1 waste treated.

The typical MSW odorants identification and the spatial odorants distribution in a large-scale transfer station.

Odorants from municipal solid waste (MSW) were complex variable, and the screening of key offensive odorants was the prerequisite for odor control process. In this study, spatial odor emissions and environmental impacts were investigated based on a large-scale working waste transfer station (LSWTS) using waste container system, and a comprehensive odor characterization method was developed and applied in terms of the odor concentration (OC), theory odor concentration (TOC), total chemical concentration (TCC), and electric nose (EN). The detected odor concentration ranged from 14 to 28 (dimensionless), and MSW container showed the highest OC value of 28, EN of 78, and TCC of 35 (ppm) due to the accumulation of leachate and residual MSW. Ninety-two species odorants were identified, and H2S, NH3, benzene, styrene, ethyl acetate, and dichloromethane were the main contributors in the container, while benzene, m,p,x-xylene, butanone, acetone, isopropanol, and ethyl acetate were predominant in the compression surface (CS) and compression plant (CP). Side of roads (SR) and unload hall (UH) showed low odorous impact. Based on this odor list, 20 species of odor substances were screened for the priority control through the synthetic evaluation method, considering the odorants concentrations, toxicity, threshold values, detection frequency, saturated vapor pressure, and appeared frequency. Graphical abstract.

Case study: Is the 'catch-all-plastics bin' useful in unlocking the hidden resource potential in the residual waste collection system?

Austria's performance in the collection of separated waste is adequate. However, the residual waste still contains substantial amounts of recyclable materials - for example, plastics, paper and board, glass and composite packaging. Plastics (lightweight packaging and similar non-packaging materials) are detected at an average mass content of 13% in residual waste. Despite this huge potential, only 3% of the total amount of residual waste (1,687,000 t y-1) is recycled. This implies that most of the recyclable materials contained in the residual waste are destined for thermal recovery and are lost for recycling. This pilot project, commissioned by the Land of Lower Austria, applied a holistic approach, unique in Europe, to the Lower Austrian waste management system. It aims to transfer excess quantities of plastic packaging and non-packaging recyclables from the residual waste system to the separately collected waste system by introducing a so-called 'catch-all-plastics bin'. A quantity flow model was constructed and the results showed a realistic increase in the amount of plastics collected of 33.9 wt%. This equals a calculated excess quantity of 19,638 t y-1. The increased plastics collection resulted in a positive impact on the climate footprint (CO2 equivalent) in line with the targets of EU Directive 94/62/EG (Circular Economy Package) and its Amendments. The new collection system involves only moderate additional costs.

Optimization of metals and plastics recovery from electric cable wastes using a plate-type electrostatic separator.

Plate-type electrostatic separators are commonly employed for the selective sorting of conductive and non-conductive granular materials. The aim of this work is to identify the optimal operating conditions of such equipment, when employed for separating copper and plastics from either flexible or rigid electric wire wastes. The experiments are performed according to the response surface methodology, on samples composed of either "calibrated" particles, obtained by manually cutting of electric wires at a predefined length (4mm), or actual machine-grinded scraps, characterized by a relatively-wide size distribution (1-4mm). The results point out the effect of particle size and shape on the effectiveness of the electrostatic separation. Different optimal operating conditions are found for flexible and rigid wires. A separate processing of the two classes of wire wastes is recommended.

Co-firing of pine chips with Turkish lignites in 750kWth circulating fluidized bed combustion system.

Two Turkish lignites which have different sulfur levels (2-2.9% dry) and ash levels (17-25% dry) were combusted with a Turkish forest red pine chips in a 750kW-thermal capacity circulating fluidized bed combustor (CFBC) system. The combustion temperature was held at 850±50°C. Flue gas emissions were measured by Gasmet DX-4000 flue gas analyzer. Two lignites were combusted alone, and then limestone was added to lignites to reduce SO2 emissions. Ca/S=3 was used. 30% percent of red pine chips were added to the lignites for co-firing experiments without limestone in order to see the biomass effects. The results showed that with limestone addition SO2 concentration was reduced below the limit values for all lignites. CO emissions are high at low excess air ratios, gets lower as the excess air ratio increases. During co-firing experiments the temperature in the freeboard was 100-150°C higher as compared to coal combustion experiments.

A full-scale study on thermal degradation of polychlorinated dibenzo- p-dioxins and dibenzofurans in municipal solid waste incinerator fly ash and its secondary air pollution control in China.

Degradation of polychlorinated dibenzo- p-dioxins and dibenzofurans in municipal solid waste incinerator fly ash is beneficial to its risk control. Fly ash was treated in a full-scale thermal degradation system (capacity 1 t d-1) to remove polychlorinated dibenzo- p-dioxins and dibenzofurans. Apart from the confirmation of the polychlorinated dibenzo- p-dioxin and dibenzofuran decomposition efficiency, we focused on two major issues that are the major obstacles for commercialising this decomposition technology in China, desorption and regeneration of dioxins and control of secondary air pollution. The toxic equivalent quantity values of polychlorinated dibenzo- p-dioxins and dibenzofurans decreased to <6 ng kg-1 and the detoxification rate was ⩾97% after treatment for 1 h at 400 °C under oxygen-deficient conditions. About 8.49% of the polychlorinated dibenzo- p-dioxins and dibenzofurans in toxic equivalent quantity (TEQ) of the original fly ash were desorbed or regenerated. The extreme high polychlorinated dibenzo- p-dioxin and dibenzofuran levels and dibenzo- p-dioxin and dibenzofuran congener profiles in the dust of the flue gas showed that desorption was the main reason, rather than de novo synthesis of polychlorinated dibenzo- p-dioxins and dibenzofurans in the exhaust pipe. Degradation furnace flue gas was introduced to the municipal solid waste incinerator economiser, and then co-processed in the air pollution control system. The degradation furnace released relatively large amounts of cadmium, lead and polychlorinated dibenzo- p-dioxins and dibenzofurans compared with the municipal solid waste incinerator, but the amounts emitted to the atmosphere did not exceed the Chinese national emission limits. Thermal degradation can therefore be used as a polychlorinated dibenzo- p-dioxin and dibenzofuran abatement method for municipal solid waste incinerator source in China.

Simulation of municipal solid waste degradation in aerobic and anaerobic bioreactor landfills.

Municipal solid waste generation is huge in growing cities of developing nations such as India, owing to the rapid industrial and population growth. In addition to various methods for treatment and disposal of municipal solid waste (landfills, composting, bio-methanation, incineration and pyrolysis), aerobic/anaerobic bioreactor landfills are gaining popularity for economical and effective disposal of municipal solid waste. However, efficiency of municipal solid waste bioreactor landfills primarily depends on the municipal solid waste decomposition rate, which can be accelerated through monitoring moisture content and temperature by using the frequency domain reflectometry probe and thermocouples, respectively. The present study demonstrates that these landfill physical properties of the heterogeneous municipal solid waste mass can be monitored using these instruments, which facilitates proper scheduling of the leachate recirculation for accelerating the decomposition rate of municipal solid waste.