Optimizing vermistabilization of waste activated sludge using vermicompost as bulking material

An integrated composting-vermicomposting system has been developed for stabilization of waste activated sludge (WAS) using matured vermicompost as bulking material and Eisenia fetida as earthworm species. Composting was considered as the main processing unit and vermicomposting as polishing unit. The integrated system was optimized by successive recycling and mixing of bulking material with WAS during composting and examining the effects of environmental condition (i.e. temperature: 10-30 °C and relative humidity: 50 and 90%) and stocking density (0-5 kg/m²) on vermicomposting. The composting stage resulted in sufficient enrichment of bulking material with organic matter after 20 cycles of recycling and mixing with WAS and produced materials acceptable for vermicomposting. Vermicomposting of composted material caused significant reduction in pH, volatile solids (VS), specific oxygen uptake rate (SOUR), total carbon (TC), total organic carbon (TOC), C/N ratio and pathogens and a substantial increase in electrical conductivity (EC), total nitrogen (TN) and total phosphorous (TP). The environmental conditions (i.e. temperature: 10-30 °C and relative humidity: 50 and 90%) and stocking density (0-5 kg/m²) have profound effects on vermicomposting. Temperature of 20 °C with high humidity is the best suited environmental condition for vermicomposting employing E. fetida. The favorable stocking density range for vermiculture is 0.5-2.0 kg/m² (optimum: 0.5 kg/m²) and for vermicomposting is 2.0-4.0 kg/m² (optimum: 3.0 kg/m²), respectively. The integrated composting-vermicomposting system potentially stabilizes and converts the hazardous WAS into quality organic manure for agronomic applications without any adverse effects.     

Experimental co-digestion of corn stalk and vermicompost to improve biogas production

Anaerobic co-digestion of corn stalk and vermicompost (VC) as well as mono-digestion of corn stalk were investigated. Batch mono-digestion experiments were performed at 35 ± 1 °C and initial total solid loading (TSL) ranged from 1.2% to 6.0%. Batch co-digestion experiments were performed at 35 ± 1 °C and initial TSL of 6% with VC proportions ranged from 20% to 80% of total solid (TS). For mono-digestion of corn stalk, a maximum methane yield of 217.60 ± 13.87 mL/g TS_added was obtained at initial TSL of 4.8%, and acidification was found at initial TSL of 6.0% with the lowest pH value of 5.10 on day 4. Co-digestion improved the methane yields by 4.42–58.61% via enhancing volatile fatty acids (VFAs) concentration and pH value compared with mono-digestion of corn stalk. The maximum biogas yield of 410.30 ± 11.01 mL/g TS_added and methane yield of 259.35 ± 13.85 mL/g TS_added were obtained for 40% VC addition. Structure analysis by X-ray diffractometry (XRD) showed that the lowest crystallinity of 35.04 of digested corn stalk was obtained from co-digestion with 40% VC, which decreased 29.4% compared to 49.6 obtained from un-treated corn stalk. It is concluded that co-digestion with VC is beneficial for improving biodigestibility and methane yield from corn stalk.     

Bioconversion of lawn waste amended with kitchen waste and buffalo dung in to value-added vermicompost using Eisenia foetida to alleviate landfill burden

Journal of Material Cycles and Waste Management - Enormous quantities of waste such as lawn waste (LW) and kitchen waste (KW) are generated in urban institutes, proper management of which is...     

Assessment of biotechnological strategies for the valorization of metal bearing wastes

The present work deals with the application of biotechnology for the mobilization of metals from different solid wastes: end of life industrial catalysts, heavy metal contaminated marine sediments and fluorescent powders coming from a cathode ray tube glass recycling process. Performed experiments were aimed at assessing the performance of acidophilic chemoautotrophic Fe/S-oxidizing bacteria for such different solid matrices, also focusing on the effect of solid concentration and of different substrata. The achieved results have evidenced that metal solubilization seems to be strongly influenced by the metal speciation and partitioning in the solid matrix. No biological effect was observed for Ni, Zn, As, Cr mobilization from marine sediments (34%, 44%, 15%, 10% yields, respectively) due to metal partitioning. On the other hand, for spent refinery catalysts (Ni, V, Mo extractions of 83%, 90% and 40%, respectively) and fluorescent powders (Zn and Y extraction of 55% and 70%, respectively), the improvement in metal extraction observed in the presence of a microbial activity confirms the key role of Fe/S oxidizing bacteria and ferrous iron. A negative effect of solid concentration was in general observed on bioleaching performances, due to the toxicity of dissolved metals and/or to the solid organic component.     

Evaluation of biotechnological processes to obtain ethanol from recycled paper sludge

Journal of Material Cycles and Waste Management - Finding innovative solutions to manage waste and to expand the production of biofuels are some of the current challenges. Pulp and paper sectors,...     

In-situ bioremediation of amine- and glycol-contaminated soils using low-intervention methods

Biological plugs are an innovative, low-intervention, in-situ bioremediation methodology for both saturated and unsaturated contaminated soils. They are modular in-ground immobilized microbe bioreactors designed to rapidly increase the oxidation of organic contaminants by placing an adapted consortia of microorganisms in close proximity to the contaminants of concern. The approach is versatile, in that contaminants can be remediated in-situ without the removal of existing structures as well as being able to efficiently and economically treat contaminants over a large area. Amine- and glycol-contaminated soils at gas sweetening plants, represent a significant problem in magnitude, prevalence, and risk along pipelines stretching through Canada's western provinces. A field pilot study was conducted at an isolated former gas sweetening plant in northwestern Alberta. Monoethyamine (MEA) and several glycols were successfully remediated in situ in a 138-day time frame. Soil toxicity was significantly reduced. The engineering challenges and associated economics of remediating such isolated sites are also presented.     

Optimal conditions to produce extracts of compost and vermicompost from oil palm and coffee pulp wastes

Journal of Material Cycles and Waste Management - Compost and vermicompost extracts represent an alternative to synthetic fertilizers and pesticides because of their beneficial effects on plants....     

The impact of the pyroligneous acid-assisted biomass ash vermicompost on dry beans through climatic and agroecosystem changes

Journal of Material Cycles and Waste Management - The present study investigates the potential of biomass ash (BA) to produce nutrient-rich vermicompost for recycling within cropping systems....     

Development of a novel hybrid microwave-heater reactor for paper-based waste treatment

It is necessary to develop a medical waste management system featuring nonburning treatment and safety functions for small medical institutions. In this article, the development of a waste management system without oxygen injection was achieved by means of hybrid heating using microwave energy and an electric heater. The shape of the microwave reactor was a rectangular parallelepiped with a volume of about 0.1 m³. In the experimental setup, microwave energy (2.45 GHz, about 800 W) was injected from the top of the reactor, while the heater (about 1 kW) was located at the bottom. Heat insulators were set into all the walls of the reactor. The gases generated in the system were vented through water and activated carbon. Five paper-based diapers with absorbed water were used as the waste sample. For the evaluation of performance, the reduction rate was defined as the ratio (in percent) of the weight before and after treatment. The reduction rate as a function of treatment time and the effect of the position of the waste in the reactor on the reduction rate and the uniformity of treatment were examined for about 3 kg of waste. It was found that the reduction rate reached as low as 4.2% at 3 h and then 3% after 8 h. The treated profile strongly depended on the position of the waste in the reactor. In particular, it was clarified that a metal cylindrical enclosure and a needle electrode played an important role in attaining uniform treatment of the waste.     

Environmental project management using fast-track methods to save time and money

In 1992, Eaton Corporation, a major manufacturer of vehicle components and electrical and electronic controls, implemented a fast-track remediation method to expedite the installation of a groundwater recovery and treatment system to contain and mitigate a chlorinated solvent plume at an industrial site. This dual-track method included fast-track and turnkey project management techniques. Our goal was to expedite the containment and removal of identified contamination, which would protect the environment, minimize future liability, and significantly reduce remediation time and costs. This goal was in the best interests of all concerned—Eaton, the community, and the state regulatory agency. This strategy took the project from dual-track concept approval by the regulatory agency to remediation system installation and start-up in less than eight months, cutting over two years from the standard Remediation Investigation/Feasibility Study (RI/FS) approach, with consequent earlier contaminant containment. Total remediation costs were half of what they would have been under the standard RI/FS procedure for this site.     

Determination of renewable energy yield from mixed waste material from the use of novel image analysis methods

Two novel techniques are presented in this study which together aim to provide a system able to determine the renewable energy potential of mixed waste materials. An image analysis tool was applied to two waste samples prepared using known quantities of source-segregated recyclable materials. The technique was used to determine the composition of the wastes, where through the use of waste component properties the biogenic content of the samples was calculated. The percentage renewable energy determined by image analysis for each sample was accurate to within 5% of the actual values calculated. Microwave-based multiple-point imaging (AutoHarvest) was used to demonstrate the ability of such a technique to determine the moisture content of mixed samples. This proof-of-concept experiment was shown to produce moisture measurement accurate to within 10%. Overall, the image analysis tool was able to determine the renewable energy potential of the mixed samples, and the AutoHarvest should enable the net calorific value calculations through the provision of moisture content measurements. The proposed system is suitable for combustion facilities, and enables the operator to understand the renewable energy potential of the waste prior to combustion.     

Monitoring, fault detection and operation prediction of MSW incinerators using multivariate statistical methods

This work proposes the application of two multivariate statistical methods, principal component analysis (PCA) and partial least square (PLS), to a continuous process of a municipal solid waste (MSW) moving grate-type incinerator for process control - monitoring, fault detection and diagnosis - through the extraction of information from historical data. PCA model is built for process monitoring capable of detecting abnormal situations and the original 16-variable process dimension is reduced to eight, the first 4 being able to capture together 86% of the total process variation. PLS model is constructed to predict the generated superheated steam flow rate allowing for control of its set points. The model retained six of the original 13 variables, explaining together 90% of the input variation and almost 98% of the output variation. The proposed methodology is demonstrated by applying those multivariate statistical methods to process data continuously measured in an actual incinerator. Both models exhibited very good performance in fault detection and isolation. In predicting the generated superheated steam flow rate for its set point control the PLS model performed very well with low prediction errors (RMSE of 3.1 and 4.1).     

Assessment of health-care waste disposal methods using a VIKOR-based fuzzy multi-criteria decision making method

Nowadays selection of the appropriate treatment method in health-care waste (HCW) management has become a challenge task for the municipal authorities especially in developing countries. Assessment of HCW disposal alternatives can be regarded as a complicated multi-criteria decision making (MCDM) problem which requires consideration of multiple alternative solutions and conflicting tangible and intangible criteria. The objective of this paper is to present a new MCDM technique based on fuzzy set theory and VIKOR method for evaluating HCW disposal methods. Linguistic variables are used by decision makers to assess the ratings and weights for the established criteria. The ordered weighted averaging (OWA) operator is utilized to aggregate individual opinions of decision makers into a group assessment. The computational procedure of the proposed framework is illustrated through a case study in Shanghai, one of the largest cities of China. The HCW treatment alternatives considered in this study include “incineration”, “steam sterilization”, “microwave” and “landfill”. The results obtained using the proposed approach are analyzed in a comparative way.     

Bioremediation of TCE in a fractured limestone aquifer using a novel horizontal passive biobarrier

This article discusses a project demonstrating the successful use of a novel horizontal biobarrier approach to protect a fractured limestone aquifer from continuing contamination while passive bioremediation of the overlying clay till source area is in progress. The emplacement of the biobarrier has significantly reduced the concentrations of chlorinated ethenes and dechlorination activity in the limestone aquifer, promoting complete reductive dechlorination of the trichloroethene plume. The biobarrier strategy has thus met the challenge of protecting the limestone from the overlying overburden. Direct GeoProbe injections performed in the source area, which consist of a clay till overburden, have also reduced the contaminant concentrations in the clay till due to enhanced dechlorination activity; however, repeat injections may be required to address the areas of the till in which the injectate has not yet been distributed. The time frame for remediating the source area in the till is expected to be on the order of a decade. © 2010 Wiley Periodicals, Inc.     

Hazard property classification of waste according to the recent propositions of the EC using different methods

Hazard classification of waste is a necessity, but the hazard properties (named “H” and soon “HP”) are still not all defined in a practical and operational manner at EU level. Following discussion of subsequent draft proposals from the Commission there is still no final decision. Methods to implement the proposals have recently been proposed: tests methods for physical risks, test batteries for aquatic and terrestrial ecotoxicity, an analytical package for exhaustive determination of organic substances and mineral elements, surrogate methods for the speciation of mineral elements in mineral substances in waste, and calculation methods for human toxicity and ecotoxicity with M factors.In this paper the different proposed methods have been applied to a large assortment of solid and liquid wastes (>1 0 0).Data for 45 wastes – documented with extensive chemical analysis and flammability test – were assessed in terms of the different HP criteria and results were compared to LoW for lack of an independent classification. For most waste streams the classification matches with the designation provided in the LoW. This indicates that the criteria used by LoW are similar to the HP limit values.This data set showed HP 14 ‘Ecotoxic chronic’ is the most discriminating HP. All wastes classified as acute ecotoxic are also chronic ecotoxic and the assessment of acute ecotoxicity separately is therefore not needed. The high number of HP 14 classified wastes is due to the very low limit values when stringent M factors are applied to total concentrations (worst case method). With M factor set to 1 the classification method is not sufficiently discriminating between hazardous and non-hazardous materials. The second most frequent hazard is HP 7 ‘Carcinogenic’. The third most frequent hazard is HP 10 ‘Toxic for reproduction’ and the fourth most frequent hazard is HP 4 “Irritant – skin irritation and eye damage”. In a stepwise approach, it seems relevant to assess HP 14 first, then, if the waste is not classified as hazardous, to assess subsequently HP 7, HP 10 and HP 4, and then if still not classified as hazardous, to assess the remaining properties.The elements triggering the HP 14 classification in order of importance are Zn, Cu, Pb, Cr, Cd and Hg. Progress in the speciation of Zn and Cu is essential for HP 14. Organics were quantified by the proposed method (AFNOR XP X30-489) and need no speciation. Organics can contribute significantly to intrinsic toxicity in many waste materials, but they are only of minor importance for the assessment of HP 14 as the metal concentrations are the main HP 14 classifiers. Organic compounds are however responsible for other toxicological characteristics (hormone disturbance, genotoxicity, reprotoxicity…) and shall be taken into account when the waste is not HP 14 classified.     

Vermicomposting of source-separated human faeces by Eisenia fetida: effect of stocking density on feed consumption rate, growth characteristics and vermicompost production

The main objective of the present study was to determine the optimum stocking density for feed consumption rate, biomass growth and reproduction of earthworm Eisenia fetida as well as determining and characterising vermicompost quantity and product, respectively, during vermicomposting of source-separated human faeces. For this, a number of experiments spanning up to 3 months were conducted using soil and vermicompost as support materials. Stocking density in the range of 0.25-5.00 kg/m² was employed in different tests. The results showed that 0.40-0.45 kg-feed/kg-worm/day was the maximum feed consumption rate by E. fetida in human faeces. The optimum stocking densities were 3.00 kg/m² for bioconversion of human faeces to vermicompost, and 0.50 kg/m² for earthworm biomass growth and reproduction.     

Changes in microbial properties and nutrient dynamics in bagasse and coir during vermicomposting: Quantification of fungal biomass through ergosterol estimation in vermicompost

In this experiment, different microorganisms viz., Trichoderma viridae, Aspergillus niger and Bacillus megaterium were inoculated in bagasse and coir with the objective to study their effect on nutrient dynamics and microbial properties, specially effect on fungal status in these waste materials. Fungal biomass (FBC) was calculated from the ergosterol content in the vermicompost samples. Inoculation of B. megaterium registered comparatively higher TP content in the final stabilized product. Vermicomposting increased microbial biomass carbon (MBC) and nitrogen (MBN) content in bagasse and coir. Microbial biomass carbon to nitrogen ratio (MBC/ MBN) was comparatively narrower in fungi inoculated vermicomposts and FBC/MBC ratio was increased up to 11.69 from 9.51 of control during vermicomposting.     

Assessment of municipal solid waste compost quality using standardized methods before preparation of plant growth media.

The quality of compost and its suitability for agricultural application depend upon physical and chemical parameters such as water-holding capacity, porosity, pH, electrical conductivity, C/N ratio, available nutrients and the absence of toxic substances. In the present study a complete characterization of an industrial municipal solid waste compost (MSWC) based on standardized European methods (CEN) for soil improvers and growing media was obtained, and compared with the quality of other Spanish composted biowaste and conventional substrates such as peat and pine bark. The MSWC was obtained from the main composting plant in Galicia (Spain), which processes organic waste that has been separated at origin and collected from more than 100 000 inhabitants. The MSWC presented a lower C/N ratio (15) than peat (84) and composted pine bark (CPB) (211), but had a similar ratio to other marketed MSWC. The nutrients and heavy metals were extracted using different recommended solvents (water, CaCl2 + diethylen triamin pentaacetic acid, and aqua regia). The nutrient concentrations of composted urban waste or manure were much higher than those of peat, CPB or pine bark. On the basis of the results of the plant tolerance test, the MSWC could be employed directly as a soil improver, but would need to be diluted with other low-salt components such as peat or CPB before being used as a growing media.