1,721,216 research outputs found
Carbon foot-print of aerobic winery wastewater treatment
No full textThe carbon associated with wastewater and its treatment accounts for approximately 6% of the global carbon balance. Within the wastewater treatment industry, winery wastewater has a minor contribution, although it can have a major impact on wine-producing regions. Typically, winery wastewater is treated by biological processes, such as the activated sludge process. Biomass produced during treatment is usually disposed of directly, i.e. without digestion or other anaerobic processes. We applied our previously published model for carbon-footprint calculation to the areas worldwide producing yearly more than 106 m3 of wine (i.e., France, Italy, Spain, California, Argentina, Australia, China, and South Africa). Datasets on wine production from the Food and Agriculture Organisation were processed and wastewater flow rates calculated with assumptions based on our previous experience. Results show that the wine production, hence the calculated wastewater flow, is reported as fairly constant in the period 2005–2007. Nevertheless, treatment process efficiency and energy-conservation may play a significant role on the overall carbon-footprint. We performed a sensitivity analysis on the efficiency of the aeration process (aSOTE per unit depth, or aSOTE/Z) in the biological treatment operations and showed significant margin for improvement. Our results show that the carbon-footprint reduction via aeration efficiency improvement is in the range of 8.1 to 12.3%.<br/
Poly-chlorinated dibenzo-p-dioxins, dibenzo-furans and dioxin-like poly-chlorinated biphenyls occurrence and removal in conventional and membrane activated sludge processes
No full textThe paper presents the results of a study focused on the occurrence and removal of dioxins and furans (PCDD/F) and poly-chlorinated biphenyls (PCB) in both conventional and membrane wastewater treatment processes. It was found that the conventionally activated sludge process could perform a good removal of PCDDs/Fs and PCBs, but the relatively low solid retention time applied and the presence of suspended solids in the effluent limited the removal capability of the system. On the other hand, the membrane bioreactor was capable of perfectly removing PCDDs/Fs and PCBs giving an effluent characterised by concentrations under the limit of detection for most of the tested compounds. This efficiency was the result of both the solids removal from the effluent (permeate) and the application of prolonged solid retention times which enabled the bioconversion of those compounds as demonstrated by the mass balances. A mathematical model was developed to predict the final fate of a given molecule according to the operational conditions applied in the wastewater treatment process.<br/
Two-phase thermophilic anaerobic digestion process for biohythane production treating biowaste: preliminary results.
Full text linkThis paper deals with the optimisation of a two-phase anaerobic process treating biowaste for hydrogen and methane production. Nor physical neither chemical pre treatments were used to optimise the process. The work was carried out at pilot scale, using two CSTRs (200 l and 380 l working volume respectively) both maintained at thermophilic temperature (55°C) and fed semi-continuously with biowaste. The experiment was divided in three periods; during the first two periods the organic loading rate was maintained at 20 kgTVS/m3d and the hydraulic retention time was changed from 6.6 to 3.3 days, while in the last period the digestate of the second reactor was recirculated to the first reactor in order to buffer the system and control pH at levels around 5. The HRT was maintained at 3.3 days and the OLR was decreased at 16.5 kgTVS/m3d. The best yield was obtained in the last period where a specific hydrogen production of 50.9 l/kgVSfed was reached, with a H2 content in biogas from the first reactor of 36%. The methanogenic stage after the hydrogen conversion reached a specific biogas production of 0.62 m3/kgVSfed and an overall organic removal above 70%, without any stability problem. The overall biogas production was some 1.5 m3 per day with a gas composition of 10% H2 and 50% CH4
Biohydrogen production from food waste in batch and semi-continuous conditions: evaluation of a two-phase approach with digestate recirculation for pH control
Full text linkThe research investigated the production of Biohythane in a two-phase anaerobic digestion process treating food waste as substrate. Preliminary batch assays were carried out at initial organic loadings of 15, 20, 25 and 30 kg TVS m?3, in stirred 1.5-l reactors at 55 °C. The results showed all hydrogen was produced within the first 24 h after feeding and the highest load tested gave the maximum hydrogen production (0.047 m3 H2 kg?1VS, H2 30%). Similar loadings were then tested in a two-phase system. Hydraulic retention times of 3 and 12 days were applied to the first and second reactor respectively. In order to keep the pH at ?5.5, either supernatant or whole digestate from the methanogenic reactor was recirculated to the first phase. Results showed that hydrogen was produced (0.117 Nm3 kg?1 VS, 47.7%) when recirculating whole digestate with an organic loading rate of 20 kg TVS m?3 day?1
Anaerobic co-digestion of winery waste and waste activated sludge: assessment of process feasibility
No full textIn this study the anaerobic co-digestion of wine lees together with waste activated sludge in
mesophilic and thermophilic conditions was tested at pilot scale. Three organic loading rates (OLRs
2.8, 3.3 and 4.5 kgCOD/m3d) and hydraulic retention times (HRTs 21, 19 and 16 days) were applied to
the reactors, in order to evaluate the best operational conditions for the maximization of the biogas
yields. The addition of lee to sludge determined a higher biogas production: the best yield obtained
was 0.40 Nm3
biogas/kgCODfed. Because of the high presence of soluble chemical oxygen demand
(COD) and polyphenols in wine lees, the best results in terms of yields and process stability were
obtained when applying the lowest of the three organic loading rates tested together with mesophilic
conditions
Full scale application of the coupled alternate cycles-membrane bioreactor (AC-MBR) process for wastewater reclamation and reuse
No full text
Nutrients recovery from anaerobic digestate of agro-waste: Techno-economic assessment of full scale applications
Full text linkThe sustainable production of fertilizers, especially those based on phosphorus, will be one of the challenges of this century. Organic wastes produced by the agriculture, urban and industrial sectors are rich in nutrients which can be conveniently recovered and used as fertilizers. In this study five full scale systems for the recovery of nutrients from anaerobic digestate produced in farm-scale plants were studied. Monitored technologies were: drying with acidic recovery, stripping with acidic recovery and membrane separation. Results showed good performances in terms of nutrients recovery with average yields always over 50% for both nitrogen and phosphorus. The techno-economic assessment showed how the specificity of the monitored systems played a major role: in particular, membranes were able to produce a stream of virtually pure water (up to 50% of the treated digestate) reducing the digestate volume, while drying, because of the limitation on recoverable heat, could treat only a limited portion (lower than 50%) of produced digestate while stripping suffered some problems because of the presence of suspended solids in the liquid fraction treated. Specific capital and operational costs for the three systems were comparable ranging between 5.40 and 6.97 € per m3 of digestate treated and followed the order stripping > drying > membranes. Costs determined in this study were similar to those observed in other European experiences reported in literature
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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