This study is focused on the effects of pH on the production of volatile fatty acids (VFAs) and their distribution through the acidogenic fermentation of source-sorted organic fraction of municipal ...solid waste (OFMSW) from a mechanical-biological treatment (MBT) plant, and food waste (FW) from a university canteen. In semi-continuous lab-scale digesters using OFMSW at a hydraulic retention time (HRT) of 3.5 days under acidic conditions (pH 6.0), the VFA concentration in the effluent increased to 9.8–11.5 g L
−1
(VS content of the feedstock between 4.2 and 5.2%
w
/
w
), while its individual VFA profiling was similar to the influent which was already pre-fermented (namely, C
2
35–41%, C
3
18–22%, C
4
17–21%, and C
5
9–12%). When working with the same conditions but using FW as feedstock, an effluent with a VFA concentration up to 11.5 g VFA L
−1
(FW with a VS content of 5.5%
w
/
w
) and a stable distribution of C
2
and C
4
acids (up to 60.3% and 12.9%, respectively) but with very low quantities of C
3
and C
5
acids (lower than 1.8 and 2.7%, respectively) was obtained. Anaerobic batch tests using FW revealed that alkaline pH near 9 could lead to higher VFA production with high acetic acid content when compared to pH 6. In the semi-continuous fermenters working at alkaline conditions (pH 9.5–10) using OFMSW and FW, an enhanced solubilization of organic matter was registered with respect to the fermenters working under acidic conditions. This fact was not reflected in a higher VFA production when using OFMSW as feedstock, probably due to free ammonia inhibition, since OFMSW was mixed in the MBT plant with supernatant from anaerobic digestion of this biowaste. However, when using FW, alkaline conditions lead to an enhanced VFA production with respect to the reactor working under acidic conditions, being acetic acid the predominant product, which represented up to 91% of the VFA spectrum obtained.
Refused Derived Fuel (RDF) could be considered as an alternative energy source, which not only helps to improve waste management, but also effectively reduce energy consumption and environmental ...pollution in huge industries. In the present study, the potential of energy valorization of rejected streams of municipal solid waste (MSW) processed in Isfahan mechanical and biological treatment (MBT) plant is investigated through RDF production. Therefore, various physical and chemical analysis of mechanical treatment rejects (MTR) and composting rejects (CR), as two streams being currently landfilled, were carried out. The results show that, RDF produced from both of these two streams could be classified as net calorific value (NCV): 3, Cl: 1 and Hg: 1 according to the European committee for standardization (CEN standard). Considering the amount of produced RDF from these two streams in Isfahan (300 t/d from MTR and 120 t/d from CR) and their NCVs, about 2 million GJ/year would be saved. As a result, in many cities of developing countries with the same condition like Isfahan, MTR and CR can be used as sources of RDF production and alternative fuels in the cement industry.
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•The potential of two Isfahan MBT plant rejects were investigated as a source of RDF production.•The MTR and CR can be used as an alternative fuel in the cement industry.•The obtain results can be generalized to other developing countries.
Municipal Solid Waste disposal is still a crucial issue, which is influenced by heterogeneous factors (political, social, economic and technological). The Mechanical Biological Treatment (MBT) plant ...is an important element of an Integrated Solid Waste Management system. These plants are aimed at separating the light and dry fraction of the Unsorted Waste from the wet one, producing the Refused Derived Fuel and recovering the metal parts. In the present work, an Exergoeconomic analysis is performed on two MBT plant structures in order to assess the unit exergy-based cost of products and allocate the irreversibility associated to each equipment. A linear variation of degree of Selective Collection (SC) of single materials (±30% respect to the base case) shows that the major influence on production costs is associated to the SC of plastic. A Monte Carlo simulation is then carried out by sampling from distributions of external (waste composition) and internal (energy consumption) uncertain variables. The resulted mean values (μ) and standard deviations (RStD) can be useful at the time of designing a new plant. The influence of the internal variable is definitely lower than the external one, with values of RStD more than 90% lower.
•Two Mechanical Biological Treatment structures are analysed.•Monte Carlo simulation is performed for uncertainty analysis.•Results show the primary importance of external variables over internal ones.•Material losses are the primary cause of irreversibility in MBT plant.•The structure of MBT plant tends to absorb and uniform the input fluctuations.
The mechanical–biological treatment (MBT) of municipal solid waste (MSW) has a number of advantages in comparison to other MSW management possibilities. However, adverse health effects related to ...this practice are not well known yet, as a varied typology of microbiological and chemical agents may be generated and released. In 2010, we initiated an environmental monitoring program to control air levels of volatile organic compounds (VOCs) and microbiological pollutants near an MBT plant in Montcada i Reixac (Catalonia, Spain). In order to assess any temporal and seasonal trends, four 6-monthly campaigns were performed. Important fluctuations were observed in the levels of different biological indicators (total and Gram-negative bacteria, fungi grown at 25°C and 37°C, and more specifically, Aspergillus fumigatus). Although overall bioaerosols concentrations were rather low, a certain increase in the mean values of bacteria and fungi was observed in summer. In contrast, higher concentrations of VOCs were found in winter, with the only exception of formaldehyde. Interestingly, although this compound was not detected in one of the sampling campaigns, current airborne levels of formaldehyde were higher than those previously reported in urban areas across Europe. Furthermore, the non-carcinogenic risks (Hazard Quotient), particularly in winter, as well as the cancer risks associated with the inhalation of VOCs, exceeded the threshold values (1 and 10−5, respectively), reaffirming the need of continuing with the monitoring program, with special emphasis on formaldehyde, a carcinogenic/mutagenic substance.
•Airborne concentrations of bioaerosols near an MBT are not of concern.•Air levels of formaldehyde were higher than those found in urban areas.•Formaldehyde and trichloroethylene were the main contributors to the Hazard Quotient.•Human health risks of VOC inhalation slightly exceeded threshold values.
Khanty-Mansiysk Autonomous Okrug – Ugra in Siberia has recently started to play a major role in the Russian economy because key oil and gas extraction sites are located in this region. As a result, ...the extensions of infrastructure and higher incomes have been leading to an accelerated population growth and consequent increase in the generation of solid household waste. The current methods of waste disposal have now reached their limits, especially in the towns Khanty-Mansiysk and Surgut. The key objectives of this study were to identify the influence of waste composition and transport routes on the life cycle assessment (LCA) results and to assess the current waste treatment option for solid household waste and to compare it with proposed scenarios. Furthermore, recommendations for an optimal use of LCA within a decision-making process for a waste management plan are presented. LCA methodology was used to evaluate different waste management scenarios such as landfilling and incineration. One result was that the options ‘incineration with recycling’ and ‘anaerobic mechanical–biological treatment with recycling’ demonstrated lower environmental impact in both Khanty-Mansiysk and Surgut. Another finding was that there were hardly any differences in the ranking of the scenarios for Surgut and Khanty-Mansiysk. However, the special socio-cultural circumstances and location of each town have to be considered seriously in the development of a sustainable waste management plan.
Legionella was detected in aeration ponds (biological treatment plant) at Borregaard Ind. Ltd., Norway, and in air samples harvested directly above these ponds. Since 2005, three outbreaks of ...legionellosis occurred within a 10 km radius from this plant. This work addresses the dispersion patterns of Legionella-containing particles by characterizing the aerosol plume emitted from these ponds (outbreak source) less than 500 meters using wind-tunnel measurements, CFD simulations, and real-life measurements. The most abundant particles directly over the ponds were less than 6 and more than 15 microm. The results showed that the aerosol plume remained narrow; 180 meters wide at 350 meters downwind of the ponds, and that 2 and 18 microm aerosols were mainly deposited in the vicinity of the ponds ( 150 - 200 meters). Furthermore, the maximum aerosol concentration level appeared 5-10 meters above ground level and the maximum concentration 500 meters downwind was approximately 2 per cent of the concentration level directly above the ponds. Our study demonstrates the strength of combining modeling with real-life aerosol analyses increasing the understanding of dispersion of airborne (pathogenic) microorganisms.
Legionella pneumophila were previously identified in the aeration ponds (up to 10(10) CFU/L) of a biological wastewater treatment plant at Borregaard Ind. Ltd., Sarpsborg, Norway, and in air samples ...(up to 3300 CFU/m(3)) collected above the aeration ponds. After 3 outbreaks of Legionnaires' disease reported in this area in 2005 and 2008, the aeration ponds of the plant were shut down by the Norwegian authorities in September 2008. The aim of the present work was to analyze the Legionella and non-Legionella bacterial communities in the aeration ponds before and during the shutdown process and to identify potential human pathogens. The non-Legionella bacterial community was investigated in selected samples during the shutdown process by 16S rDNA sequencing of clone libraries (400 clones) and growth analysis. The concentration of L. pneumophila and Pseudomonas spp. DNA were monitored by quantitative PCR. Results showed a decrease in the concentration of L. pneumophila and Pseudomonas spp. during the shutdown. This was accompanied by a significant change in the composition of the bacterial community in the aeration ponds. This study demonstrated that several advanced analytical methods are necessary to characterize the bacterial population in complex environments, such as the industrial aeration ponds.
On-line determination of pollution loads (Suspended Solids, Volatile Suspended Solids, Biological Oxygen Demand and Chemical Oxygen Demand) on biological waste-water treatment plant is the prevalent ...practice for process control. Both measurement of turbidity and others on - line parameters allows to approach plant loads. It is possible to estimate Suspended Solids of inlet by turbidity measurement at 550nm and 850nm. COD could be approached by turbidity and conductivity measurement. The conception of a dynamic probe in activated sludge allows us to determine suspended solids (with turbidity and settleability of sludge) and its volatile part (turbidity with settleability and oxygen decrease rate). By the way it can be possible to predict sludge bulking. All these parameters are obtained with a less than 15% average error (8% for sludge). We have to compare these results with the important error induced by sample conservation before analysis in the case of classic self-control.
Soil rehabilitation in the context of the restoration of quarries, dumping sites, or road slopes often requires the prior addition of organic amendments to improve the substrates used for Technosol ...construction. Bio-wastes coming from advanced Mechanical-Biological Treatment Plants, mainly compost-like-outputs (CLO) and digestates (DGT), are new and suitable sources of organic matter potentially useful as organic amendments for this purpose, in an approach clearly fulfilling the principles of circular economy. In order to assess the suitability of these materials, a complete physicochemical and biological evaluation was carried out, including an ecotoxicological evaluation to discard hazardous effects on key soil fauna groups. Field experiments were also carried out on several road slopes and a dumping site. The stability degree of organic matter and the impurities content could be restricting parameters for the use of CLO in soils. Low stability degree decreased plant development in the initial stages of restoration. Moreover, the high heterogeneity in terms of physicochemical parameters of the different CLOs assessed is a serious constraint to making generalizations about its use. In contrast, composition of DGTs was more stable between plants and batches, and presented low impurities and high N contents that make them more suitable for applying to soil and promoting plant development. Regarding the application rates, DGT application at 20 g kg−1 clearly improved plant growth after sowing, without compromising recruitment. However, application at 80 g kg−1 did not ameliorate seed germination and plant growth, in either CLO or DGT treatments, and increased N-leaching and toxicity risk to soil mesofauna in DGT amended Technosols.
•CLO and digestates from MBTP are suitable as organic amendments for Technosols.•The stability degree and the impurities content of CLO could be restricting parameters for their application to soils.•High heterogeneity between batches and production plants hinders making strong generalizations related to the use of CLO.•Digestates have a more stable composition and present lower impurities and higher N contents than CLO.•Application rates higher than 2% should be avoided.•A case per case evaluation should be done before its application at soil.
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